Booms may be improvised, manufactured and also have variable dimensions. They will be subjected to the marine currents, the direction and velocity of the wind, height and frequency of the waves as well as different depth.
There primary uses are for deflection, collection and protection. Depending on the type of the hydrocarbon derivative, such as naphtha and gasoline that are very volatile and have low flash points, we may opt to simply deflect from the risk of explosion or protect sensitive areas while it evaporates.
The containment booms are used to accumulate the oil and prevent it from spreading, facilitating its removal. A well deployed boom is the first step towards the success of an operation. The installation and the maintenance of booms require well trained personnel.
It is obvious that the efficiency of a designed boom is much better, but the first response is to try to stop the oil spreading by using anything that may be at hand. If at the moment of an oil spill, the crew does not have resources available for the response it, it is worthwhile to put together planks, foliage, screens and bags of sand or gravel.
The photo left, shows a couple of coconut fronds effectively holding back heavy fuel oil in a stream.
The booms should generally be the first response equipment to arrive at an oil spill and there efficient deployment is the first job to be done then the skimmers and tanks are deployed.
The persons responsible for the selection and use of the booms should understand their functions, and know exactly where each type of boom is most adequate. They should also understand the prevailing weather conditions, durability, forms of storage, transportation and the capacity for containment.
Operations with booms require knowledge of boat handling, use of anchors, buoys and ancillary materials. Some systems have hydraulic driven reels, so we have hoses and ropes on the ground these are all potential hazards and should be stowed correctly so the job can be done safely.
All ropes should be coiled or laid in a manner that know one gets caught in them. Everyone is responsible for the safety of the others in the team.
The effective capacity for response to oil spills is a combination of three principal factors: Speed and efficiency of mustering the service crew; Quantity, availability and applicability of the equipment for the response action. Quantity and availability of personnel trained to do the work.
The Canadian Shipping act establishes guidelines for planning equipment requirements for response.
The containment boom formula:
B = 1.25 x H
B = the amount of boom in meters required to contain the free floating oil.
H = The amount of oil spilled in m3
Based on this formula for a spill of 1000m3 B = 1.25 x 1000 = 1250 meters of boom.
This is a guide for planning purposes to see the minimum amount of boom necessary, not as some people think the correct amount required.
There are so many variables in reality, e.g. type of oil (heavy or light) time to respond, wind and current speed and direction, wave period and frequency. All of these things make the use of a formula for an effective response useless.
Bearing in mind that dependent on the type of oil involved 100m3 of fresh black crude oil can cover an area of 1km2 then 1000m3 could cover an area of 10km2 in a few hours. On the other hand, heavy fuel oil tends stay close to the spill site and not spread to the same extent.
Offshore boom usually comes in 250m or 300m lengths so at best this is 5 booms. When used in U or J configurations the vessels will be a maximum of 100 meters apart therefore these 5 systems will have 500m of boom encountering the oil.
Over the years minimum guidelines have been made for the construction of booms, for the weigh of ballast and the strength of materials used for different situations here are three important ones;
Water body classification for oil spill control systems
Type Wave Height meters General conditions
Calm 0 – 0.3 Small, short non breaking waves
Protected 0 – 1 Small waves, some white caps
Open 0 – 2 Moderate waves, frequent white caps
Open Rough > 2 Large waves, foam crests, some spray
Boom selection according to water body classification
Boom property Calm Calm – current Protected Open
Min reserve buoyancy to weight ratio 2:1 3:1 3:1 7:1
Min total tensile strength N 150 - 600 200 – 600 450 – 1,100 900 - 2,300
Min skirt fabric tensile strength N 6,800 23,000 23,000 45,000
Min skirt fabric tensile strength N/50mm 2,600 2,600 3,500 3,500
Min skirt tear strength N 450 450 450 450
Boom component parts
This may be air filled or rigid and has the purpose of maintaining the correct orientation of the equipment on the water, establishing freeboard in order to minimise the loss of oil over the boom. Float materials are air, foam, bubble rap, cork, etc. Designed to float the boom even with some load or tension. When inflated all caps should be replace, trash can get into valves and release air.
In some cases the float material used is bubble rap, these floats have been cut out of booms to be used as pillows in some poor areas of the world.
This is the minimum vertical height of the boom above the water line to the top of the float section. It prevents oil from being washed over the boom. If it is too high it may be pushed over by high winds. In open water the boom must maintain its freeboard in waves. It must be flexible enought to rise and fall with the waves so that the freeboard is not lost.
The continuous portion below the water, which has the purpose of containing the oil. To some degree the deeper the skirt the more effedtive it is however there is a optimum skirt depth for different applications. Since the forces acting on the skirt are proportional to the skirt area. Increasing the skirt depth to what is really necessary put heavy loads on the tension member.
The distance measured from the water line to the lower limit of the skirt is called the draft.
In shallow water it should be mentioned that the skirt should not take up more than 20% of the water depth as it causes and increase in current velocity which will drag the boom under the water with the oil flowing over the top or in other cases especially near the shoreline encourage oil to flow under the boom.
Is weight added to the bottom of the skirt to maintain the barrier in a position perpendicular to the surface of the water and in some cases to provide the tension member for the boom.
Some manufacturers use, Steel or lead weights, water, may be used. These weights are very often cut from booms by fishermen. Below is a guideline for the weight of ballast dependent on boom size.
Ballast for a 0.7 knot current
Skirt depth mm Ballast kg/m
Any component that carries the horizontal tension imposed on the boom. They are normally chains or wire ropes running along the bottom of the skirt. Some manufactures may run wire ropes along the top of the freeboard as well as the bottom of the skirt. Some booms may have heavy fabric that acts as the tension member. Others have tension members that are exterior to the boom. In this case they are positioned upstream and attached to both top and bottom with a series of bridle.
The tension member should never be lengthened as the stress will be transferred to the material usually causing the material to part thus loss of the boom from the operation.
A quick-connect device that permit the coupling together of as many lengths of booms as are necessary. These are just 6 of the many different types used by different manufactures and most will not interconnect.
When ordering boom make sure all your connections are the same to reduce problems during a future incident.
Some booms come with plastic thumb screws which can be brittle in winter or soft in hot climates, either way you ring the winged head off them causing a serious problem of getting the remains out of the hole.
Over the years these have been replaced by spring loaded toggle pins like the one on the left. These push through the holes in the connection where the toggle then drops and the spring holds it in place. These are fine for training but during operations where booms may be out for weeks, metal bolts with wing nuts and spring washers are safer.
There is a need for at least two in each connector, I have deployed booms where the manufacturer only supplied one in the middle. This worked fine while it was being deployed but when the weight came of the boom the connectors came apart slightly which allowed the current to bend all the connectors in the middle.
All responders should have spare pins and nuts and bolts in their pockets, in many cases the pins are connected to the boom with small wires that are pop riveted to the connection. Unfortunately these wires break so if you don't have a spare the boom does not get deployed.
The original Monsun valve was first introduced in 1971 and is used by various manufactures around the world.
The MV XS (Yellow) is particularly effective in oil booms of limited size, inflatable boats, tanks or other similar objects. Photo to follow of a tool I have to open and close the valve, as they tear finger ends.
MV XII (Black) has a low profile, easy-grip screw cap, no hooking parts and a spring-loaded valve disc that is extremely easy to lock and release and a large free area allow volumes of air to passthrough in optimised quantities, delivering faster inflation and deflation.
Valves removed through bad handling photo right cannot be replaced without the correct tools, it is much better to handle equipment with care than to find yourself with insufficient boom to complete the task in hand.
Tow ends / Bridles
From a logistics point of view the more compact and lighter the tow end is the better, it means more equipment in a smaller space. From an operational point of view the ligher the equipment the easier it can be handled and therefore the easier it is to deploy.
Here are some photo's of a few different tow end from around the world.
Photo left is an ASTM conector with a rope tow bridle in other cases the rope is wire some have both legs the same length others have a shorter leg at the bottom so the forces are directed to the tension member at the bottom of the boom skirt.
Photo right is a three leg tow bridle, each leg is of a different length. The top leg is shorter than the middle leg which is shorter than the bottom leg.
Basically the manufacturer put it on the wrong way around. This means that any forces will be transfered to the top of the boom which normally results in the boom material tearing away from the connector which is also shorter than the boom connector.
Photo left is a tow end which weighs approx. 25kgs.
The aluminium connector is attached to a galvanised steel frame which is bolted together (probably the manfacturer does not know how to weld) it is over 0.5m high and wide.
The float is over 30cm in diameter. This means that if the boom is used against e.g dock wall there will be a gap for oil to escape through.
It also has a ballast weight which is a little strange, as the boom has ballast and a float. Tow ends do not need to float upright on their own!
The size and weight makes it difficult to handle and from the logistical point of view you can put 50 of the top types into a 210ltr/45 gal oil drum, where as this bottom one will not fit at all, so unnecessary space is taken up.
It has also been noticed that the bottom type are so heavy they sink the end of small sized boom.
Their purpose is to maintain the booms in the correct position. Among the countless types, the most frequently used during oil spill operations are the Bruce (Mud) and Danforth (sand).
The length of anchor cable should be approximately 5 times the local depth. This is attached to a chain to keep the rope from lifting the anchor in swell or wave conditions.
E.g. if we are going to anchor a boom in 8m of water, we will need 40m of rope. Knowing the depth at high tide is important to avoid any embarrassment like the photo right wbere the apex of the boom is submerged.
I will never forget an idiot who once asked for boom to be anchored near an FPSO in 1,200m of water depth, we would have required 6km of rope for each anchor.
While on the subject of water depth, this diagram left shows something important to remember. The depth of the draft of you boom should not be more than 20% of the total depth.
This is more important in rivers or when the tide turns as this reduces the amount of space under the boom, thus increasing the speed of the current.
The same volume of water is trying to get through a smaller space.
This will also increase the opportunity for any oil to be entrained under the boom. This is known as under cut and is mentioned again below with all the other boom limitations.
On shorelines or riverbanks, steel or wooden stakes can be used. The main problem is not the stake it is the aim of the guy with the sledge hammer.
I read a safety report about a person hammering a steel stake into the ground, it is normal to see the top of steel stakes looking like mushrooms but in this case as the hammer hit the stake a piece of the mushroom flew off like a bullet and hit someone 5 meters away in the chest where it entered his heart and killed him. unfortunately someone usually has to die for things to change from a safety point of view.
When slide hammers like the one on the right are used they have removed this problem.
Photo left is a design for a simple plate anchor as used by the MCA in the UK for shorelines or river banks they have excellent holding strength.
Photo left shows metal stakes being used. When positioned correctly they are placed one behind the other in line with the boom. The way they are tied together puts the forces on the bottom of the front stake which cannot be pulled forward because the top of the front stake is lashed to the bottom of the rear one.
Photo right is a rake type anchor used in rivers where they dig into gravel, mud or sand. The prongs are on both side so that which ever way they land they will work.
This type of design comes from training and trying different things and therefore inventing objects that were not available at the time.
This claw shaped anchor was designed by Peter Bruce from the Isle of Man in the 1970s. Bruce gained his early reputation from the production of large scale commercial anchors for ships and fixed installations such as oil rigs. The Bruce and its copies, known generically as "claws", have become a popular. It was intended to address some of the problems of the only general-purpose option then available, the plough. Claw-types set quickly in most seabeds and although not an articulated design, they have the reputation of not breaking out with tide, instead slowly turning in the bottom to align with the force.
Claw types have difficulty penetrating weedy bottoms and grass. They offer a fairly low holding power to weight ratio and generally have to be over-sized to compete with other types. On the other hand they perform relatively well with low rode scopes and set fairly reliably.
American Richard Danforth invented the Danforth fluke type pattern in the 1940s for use aboard landing craft. It uses a stock at the crown to which two large flat triangular flukes are attached. The stock is hinged so the flukes can orient toward the bottom. Tripping palms at the crown act to tip the flukes into the seabed. The design is a burying variety, and once well set can develope high resistance. Its light weight and compact flat design make it easy to retrieve and relatively easy to store.
The fluke anchor has difficulty penetrating kelp and weed-covered bottoms, as well as rocky and particularly hard sand or clay bottoms. If there is much current or the vessel is moving while dropping the anchor it may "kite" or "skate" over the bottom due to the large fluke area acting as a sail or wing. Once set, the anchor tends to break out and reset when the direction of force changes dramatically, such as with the changing tide, and on some occasions it might not reset but instead drag.
In recent years there has been something of a spurt in anchor design. Primarily designed to set very quickly, then generate high holding power, these anchors (mostly proprietary inventions still under patent) are finding homes with users of small to medium sized vessels.
The German designed bow anchor, Bügelanker (or Wasi), has a sharp tip for penetrating weed, and features a roll-bar which allows the correct setting attitude to be achieved without the need for extra weight to be inserted into the tip.
The Bulwagga is a unique design featuring three flukes instead of the usual two. It has performed well in tests by independent sources such as American boating magazine Practical Sailor.
The Spade is a French design which has proved successful since 1996. It features a demountable shank and the choice of galvanized steel, stainless steel, or aluminium construction, which means a lighter and more easily stowable anchor.
The New Zealand designed Rocna has been produced since 2004. It too features a sharp toe like the Bügel for penetrating weed and grass, sets quickly, and has a particularly large fluke area. Its roll-bar is also similar to that of the Bügel.
The Rocna obtained the highest averaged holding power in Sail magazine's comparison testing in 2006.
Dependent on where you are and the availability of these anchors, rocks or concrete blocks work well in calm conditions.
Left we have the local population being used as anchors, why you have boom but don't have anchors or rope is difficult to understand.
A thin rope attached to the head of the anchor to assist with removing it from the mud or sand. We should use the length of rope equal to 1.5 times the local depth. A float tied to it for ease of location.
Photo right shows the damage done to anchors when they are stuck in the mud and are pulled out without a tripping rope.
Note: do not use nice bright buoys as people will steal them and receive a free anchor. Nobody looks twice at a floating 2 litre plastic bottle which is a lot cheaper and does the same job.
These are the locations appropriate for tying anchor ropes and serve to maintain a given configuration of the boom in the water. With many types of boom anchors can only be fitted at the connections.
Tying rope around the boom to make an anchor point usually cuts the boom material with the water movement. It is important to note that the faster the current the more anchors will be needed so shorter lengths of boom must be used to gain the extra connections where the anchors can be tied safely.
Generally polypropylene photo left is used as it is light and usually floats. 12mm to 15mm works well for coastal and river booms and a thinner one or sometimes of a different colour for the tripping buoy to make life simple.
As mentioned in the Ropes and Knots section braided ropes photo right are used where they are handled constantly. The braiding makes the rope more comfortable to handle but also increases the breaking strain. This can be seen here with 2 examples of 10mm diameter rope.
Rope material Kg per 100m Breaking load kg Breaking load kN
Polypropylene 4,5 1425 14.5
Braided Nylon 7.5 2750 25.7
The rope is the safety link to the boom and should always be of a lesser breaking strain than that of the boom. Rope is cheap, booms certainly are not.
It should be mentioned that if a coil or rope arrives like the one above left do not pull the loose end on the outside.
If possible make a box and have the inner loose end come through a hole on the middle.
If you pull the wrong end you end up with the tangle left.
When not in use, coil them or flake them in figure of eights and keep them tidy, as they seem to have minds of their own.
For more on rope see Rope and knots under the Marine tab above.
Dependent on given location, the following considerations should be kept in mind:
The circumstances under which the barrier will operate:
- Height of the waves
- Wave frequency
- Sheltered or open waters
- Currents speed
- Good access
- Fixed location (Close to the area of risk)
- Transportation requirements
- Availability of labour and equipment for deploying the boom
- The need for compatibility between the different types of booms.
Similar considerations will have to be taken into account for the deploying of the equipment. However, in many cases, the response team coordinator will have little choice in the types of booms and will have to use what is readily available.
The importance of pre-planning for the choice of booms and all of the associated equipment cannot be underestimated.
This boom has a world wide reputation as being one of the strongest and easy to work with booms around. The diagram shows the different sizes of boom this manufacturer produces from 910mm to 2mtr.
They do produce this type of boom to 3.5mtrs specifically for the Norwegian sector of the North Sea, this was produced after the diagram was made.
The idea of this diagram is to show that one manufacturer will produce many different types and sizes to suit many different situations.
Types of boom
These booms are made of rigid or semi-rigid material, in order to contain the floating oil. They are more able to resist abrasion, easy to handle, clean and store, besides being highly reliable.
They are used in calm quiet waters.
The disadvantages are they have low stability in strong winds and currents, slight flexibility for towing, low efficiency in waves and need reinforcement to prevent wear or breaking and are therefore used in calm areas.
Curtain (Tube and Skirt)
Air filled curtain booms have the advantage of being relatively compact when empty, they are easily stored, handled and are efficient. The float elements are chambers filled with air,. They are very good for towing and installing and are good in rolling seas. On the other hand, they have the disadvantage of low resistance to abrasion and are easily punctured if mishandled. They have a flexible skirt maintained by a ballast of either chain or wire rope which is also their tension member.
Solid flotation curtain booms are made of chambers filled with polyurethane, polystyrene, bubble rap or cork. They display high reliability and efficiency when towed, besides being easily handled; the disadvantage is they have large volume from a logistics point of view. They also have little horizontal flexibility in rolling seas. The booms are normally manufactured from oil resistant fabric, being coated with neoprene, polyurethane or PVC.
This manufacturer has a copyright on a boom that can be a fence boom and can be used in calm waters.
It can also be inflated to become a curtain boom for rougher waters on the right. The permanent floatation along both sides of the boom should provide more resistance in areas where abrasion is a problem.
Photo left is a version of the shore sealing boom which has an air inflated floatation tube on top and two lower tubes that are filled with water to make up the skirt of the boom and act as its ballast.
They are used in the inter tidal section of the shoreline, from the high tide mark to the low tide mark where a Curtain type boom is connected for the area below the low water mark.
The photo left also shows how not to do it, the black oil line on the boom shows that at high tide the oil passed the end of the boom.
The boom should always be deployed above the high tide line. At low tide, the lower tubes settle on the substrate, maintaining a seal and preventing the passage of oil as shown in the diagram below.
The line on a shore where all the plastic bottles, dead fish and flip flops are found is the high tide mark. In many cases the low tide line is difficult to find without local knowledge.
The photo right shows the boom positioned correctly passing the high water mark shown by the line of seaweed.
Be aware when pumping water into this type of boom that small pebbles and or sand may be pumped into the tube as well. This will cause serious problems later by both increasing the weight of the boom as well as the difficulty of getting it back out without damaging the boom.
In some places kelp or other types of sea weed may block the intake, I have seen this problem solved by using the drum of a washing machine which allowed the water to enter through the holes but kept the weed at bay. They are also made of stainless steel so it became part of the kit for that group of responders.The water tubes (bottom) have a pair of white relief valves to reduce the risk of damage during tidal changes especially on steep inclines. Without them the weight of all the water pushes against the end connection which in some cases it parts company with the boom material.
Some manufactures of this type of boom include pressure relief valves in the water tubes, others say they are optional extras but use the photo above left. Remember just because the photo in the brochure shows them. does not mean you will get them without asking.
Without these valves the water pump should be pumping water before it is connected to the boom or the pump will add air and not allow the section to be fully filled with water thus reducing the weight dramatically.
It also means the water has to be pumped from the end in the water as the other end is 20 or 25 meters away from the water. When this is done the onshore end valve can be opened to let the air out. In my opinion these valves are not optional extras they are necessary and reduce damage and new operator errors.
The water chamber valve caps should be painted blue to allow for quick recognitition during deployment.
The two photos below show the bay at São Luiz in northern Brasil, the tidal range is approx. 10 meters but the shore line is flat and so there are huge sand and mud banks from the high to low tide lines. In this case there is approx. 1 kilomete of mud. This is the area where the shore sealing boom needs to cover.
In areas like this tanks should be filled with water at the high tide mark and water pumped into the boom link tubes photo right maybe used to fill the boom during low tide. This allows for one point inflation for various lengths of boom. They may be removed at high tide to keep the integrity of the boom deployment
It must be mentioned that they are susceptable to damage and if you get a leak in one boom all of them will deflate.
When the tide comes in with the oil, only when the boom is floating totally will the oil stop escaping under the skirt.
Diagram taken from oil spill training.
The photo right is a common sight where the wrong boom for the purpose has either not been sent or probably more common has not been bought or sourced. There will always be someone there to take a photo of failures in planning.
Figure of eight
These booms have excellent wave following characteristics, they are constructed from two independent chambers, the upper of air and below of water. These booms require a constant flow of air and water while it is deployed. An air fan and water pump work continuously. In the event of a problem with the flow of air, the boom will sink. When deploying if there is insufficient weight of water in the boom they have been known to fly in windy conditions. This is an old design which is not common anymore due to its disadvantages outweighing the advantages.
Here are 2 different types the versions on the right we have springs down the length of each float section which lie flat when the boom is rolled up on the reel.
When the boom is deployed the spring opens up and sucks air in through the valve. This type of boom needs to be deployed at least twice per year and stored in the dry. One of the main problems is the steel spring gets rusty and sticks to the material if left for a long time or stored in a humid place. This can usually be sorted by kicking the side of the boom as it is deployed. Unfortunately some sections can have problems and with no air they sink.
The type on the left has a rigid plastic diamond structures inside the float section which when deployed open and suck air in through the valves. These valves are opened before the boom is deployed and closed when the boom has been recovered.
The boom is stored vertically on a carousel which can be difficult when recovering it as one or two people have to stand on the carousel to manually stand the boom vertically, on occasions new people get caught between the boom as it is being recovered.
The boom can be picked up by helicopter then taken to the spill site and dropped in the water where a boat picks up the tow end and as it moves away the boom unrolls very easily. If the helicopter is not an option then it can be recovered onto a standard horizontal boom reel which will make life much easier for both deployment and recovery. http://www.youtube.com/watch?v=zqxGn52RhV0&feature=related
I prefer booms with air panels as opposed to a continous air tube as they are much easier to repair during an operation. A section may leak but the whole boom can be used to collect oil, it is just a case of manouvering the damaged section out of the apex. With a continous air tube one problem and you have lost the whole boom until it is removed from the water and repaired.
Three vessels participate in this operation, two securing the extremities of the boom. When the configuration is ready, a third vessel recovers the oil. In some cases the U is used to collect a wider extent of oil then it is changed into a J so that the oil can be recovered. Good communications are needed so as not to lead to loss of oil in the apex. In most cases the recovery vessel becomes the command vessel as it is closest to the apex and can see what is happening with the oil which the other two cannot. It has been known for the recovery vessel to enter the U; this is not advisable due to the lack of manoeuvrability and unnecessary contamination of the vessel.
Two vessels secure the extremities of the booms, while at the apex a skimming vessel is attached. All the oil is directed towards this skimmer.
Many photographs have been taken of the oil passing under the skimmer vessel due to the speed of the tow vessels.
In this photo left there is a huge miss match of power in the tow vessels which can cause a see saw situation leading to oil loss. Good communications are required.
Many booms have been destroyed with this manouver usually during the early stages of the formation. The damage occurs when the less manouverable small tow end vessels are expected to pull the whole lenght of boom up in front of the main recovery vessel this usually takes a long time against the current and the pressure against the boom either breaks the tow rope or the boom itself.
This can be avoided simply by looking at the description in (Offshore deployments) below.
Three vessels are used. A central vessel, equipped with skimmers and storage systems is positioned in the centre the booms deployed from both sides of this vessel with two smaller vessels secure the extremities. This set up greatly restricts manoeuvrability and is only used with highly trained crews. The U configurations on each side are towed alternatively to form J's to recover the oil. Communications are extremely important.
This photograph show a W configuration with two recovery systems in place.
How things have changed for the good and bad over the years for the responder.
A few years ago when the world was not so obsessed with our environment, we used vessels of convenience for boom deployments.
It was rare that you would be able to find a free rig supply boat as they were few and had continuous work to do.
A supply boat is basically a truck at sea. It has a large free deck to carry drill pipe and all the other equipment necessary for the offshore drilling and production industry. They have various sizes and amounts of tanks dependent on the size of the vessel for carrying drilling muds, fluids, chemicals, diesel and fresh water needed to sustain a rig or platform during their operations.
In the late 70’s when I worked in the North Sea many of these supply boats fitted with fire monitors which could be used in the event of a fire aboard a rig or platform. This modification increased the daily hire charge for the vessel.
With the expansion of the world’s oilfields there has been an increase in the amount of supply boats. With the change to an Eco Friendly world, many of these vessels have now been fitted with oil spill booms and skimmers. In a lot of cases this has been a huge investment with excellent equipment in the right place for deployment.
From a good point of view this has increased the amount of equipment available and also increased the daily hire rate.
From a bad point of view many of these vessels have placed the equipment behind the accommodation to keep the deck clear so they can still be used as a supply boat.
Some supply vessels are built for a second role of rig anchor handling. Some of the chains weigh as much as 1 tonne per meter with a 20 tonne anchor on the end. We are now drilling in more than a thousand meters of water, so these vessels are designed to deploy and pull more than a thousand tonnes. We now put booms aboard and expect the same vessels to work with a few tonnes at the most. This is like tying two trucks together with an elastic band.
Many of these new vessels have the ability to stay in position using their main propellers, bow thrusters and stern thrusters or have the ability to operate at very low speed with their DP computerized systems.
Others can only achieve low speeds by clutching the main engine in and out. This can cause repeated strain on the tow rope and the tension member of the boom. Some booms are constructed with steel or stainless steel connections which can stand this type of strain.
Other booms have aluminium connectors which then have steel shackles to connect to the ballast chain or rope. This pushing action on the tow rope causes the steel shackle to deform its hole in the connector, after a couple of days the shackle pulls free and then the boom tears apart.
In many cases structures have been built so the boom is deployed over the side rail but in others it is deployed through a letter box in the side wall of the vessel.
This situation makes it more difficult to deploy and recover the boom, as the connectors snag on the edges of the hole and the boat crew cannot see the crew on deck at the reel.
This method originated in Norway where booms have become part of the ships structure.
Obviously it is much better for the equipment and personnel to be in the warm during the deploying rather than on deck in sub zero conditions. In warm tropical climate this is not a problem.
Deploying booms over the side has always been difficult, the recovery is even worse and in many case cause serious damage to the boom.
Most of this damage is caused by the tow vessel, trying to maintain position for the boom to be recovered onto a reel, with the prime vessel trying to maintain position across the current. It is easier in calm conditions but in a real event at sea it may be difficult to find a calm area.
To accomplish this each crew of each vessel needs to have regular exercises, unfortunately if the equipment is in the wrong place this may cause even more damage.
I have trained crews over the years in an attempt to reduce the damage cause during deployments.
Unfortunately what normally happens is the small towboat picks up the tow rope and pulls 400 meters of boom during its deployment.
Now it is expected to pull the boom up past the prime vessel to the required position for the configuration. This is when ropes part or worse the boom is damaged due to the strain.
As has been said before, the lack of training and equipment maintenance is still a serious problem in many parts of the world. The problem for many supply boats to carry out training is difficult with the amount of cargo work that has to be carried out on a normal day.
Having finally deployed the boom into the water the tow lines are then adjusted to bring the boom up the side of the vessel so that the skimmer can be deployed using the ships crane amidships photo right.
These cranes were positioned behind the accommodation for launching rescue boats at sea of receiving stores in port.
With the boom tied off along side and the J or U configuration in position the weight of water in the booms apex dependent on the boom type may be as much as 70 tonnes.
This weight may be up to 20 meters off the side of the vessel making it extremely difficult for the prime vessel to manoeuver. This is due to all this weight being at the point where the rope is tied off.
This point becomes the pivot point for the vessel, the closer to the stern the better as in photo left.
The helmsman will find it easy to turn towards the boom but nearly impossible to turn away from it without causing damage either to the rope or the boom where rope sizes and materials have been changed.
Dedicated oil spill response vessels OSRV's are now becoming more common though even some of these have side deployment systems. In some countries there is a need for certification for the recovery of spilled oil from a safety point of view.
The preferred place to deploy the boom from is the stern where the tow ropes are tied off and the apex of the boom is bought in as close to the vessel as possible making it much easier for the vessel to manoeuver and for the deck operation can be seen from the bridge.
Now let’s look at this sensibly:
1. we usually have a prime vessel with her drive propellers, bow and stern thrusters with which she can turn in her own length.
2. we also have a small work boat to pull the other end of the boom.
3. we deploy the boom over the stern of the prime vessel with a buoy on the end of the tow rope, photo left, when the boom is fully deployed and tied off in position, turn the prime vessel to form the U or J diagram right.
During this operation there is no strain on the boom.
4. when this is done, let the small vessel picks up the buoy and maintain position for the required configuration.
During a real oil spill event the prime vessel runs with the current and the oil, deploying the boom as she goes. When all is deployed and tied in place, she turns forming a J and begins collecting oil as the small vessel picks up the tow end and positions herself.
To assist even more we used sea anchors from old life rafts attached to the buoy to add more resistance during the deployment.
It is that simple but trying to get people to do it, is an uphill challange.
Forces acting on booms
The force of the wind acts on the freeboard and the force of the current acts on the skirt of the boom. The way the waves transmit their force to the booms is somewhat complex. The majority of mathematical models recognize that waves lend an additional "particle of velocity" to the water, independent of any constant current velocity.
The forces exercised on the booms are calculated using the following formula:
F (T) = F(C) + F (V)
F(T) = Total Force
F(C) = Force of the current = K . Ai . Vd2
F(v) = Force of the wind
Ai = submerged area (length of the boom multiplied by its draft) – m2
Vc = velocity of movement in relation to the water - knots
Fv (force due to the wind) = K . Ae . Vv2
K = 26 (constant)
Ae = exposed area (length of the boom multiplied by the freeboard)
Vv = velocity of the wind in knots
Generally the force of the current prevails over the force of the wind
Before purchasing a boom, an analyze of what type of location it will be used in (sheltered waters, offshore, waters under the influence of There are booms with different degrees of complexity tides). We should also take into consideration the number of people that will need to be trained and available to deploy it.
We should also consider the place where they will be stored. Before we purchace a boom, we should also take into consideration how long the boom will be exposed to the local weather conditions (sunlight, incrustations.
These booms are large, robust and they function well in waves up to 2 m in height. Above this height, the barrier begins to fail. Generally these booms have a freeboard of 40-60 cm and a skirt of 0.80 – 1.60. Some are up to 3 metres in total and are stored on huge reels they were developed for the rough northern seas. Many booms have 300m of continuous length.
Other booms look similar but have smaller sections which are connected by an inflation tube along the top of the float chambers. A blower is connected to the tow end during the deployment. When the required air pressure is achieve a valve closes and the air moves to the next section. The deployment process taking about 20 min. Other models have several sections. Each chamber must be inflated separately.
They have independent chambers with check valves this means that, if one of the compartments is ruptured, the others will continue to function. This type of boom requires greater skill of the user. These booms usually have smaller floatation sections and are in lengths of 50m on reels of 300m, this is good, if a section is damaged there is 250m left when the other has been removed. Reduction in deployment times and damage can only be achieved by continuous training.
These booms are much smaller than oceanic ones. Theay are designed to function well in locations with waves up to 0.80m high. Often they are used in bays and sheltered areas. They are easy to handle and require less training.
The permanent booms are larger (about 1 m); heavier and made from material that is resistant to solar radiation (PU-polyurethane). They are designed to withstand incrustations and have floats sized to support this added weight. Because of this, these booms are usually also much more expensive. They may work for up to 3 years permanently deployed but require maintenance mainly to remove marine growth.
Along dock walls the use of a quick rope rising mooring made from a rope with a weight on the end, this can be steel or concrete but not an anchor as they always get caught on the boom skirt when the job is finished. The first rope is threaded through the shackels on the tow end.
The simple things work the best for example this Boom Standoff Unit is basically an aluminium triange with wear resistant floats to keep containment boom away from the hull of a ship or to hold the boom off a dock area. This has two advantages, firstly it will reduce the amount of wear and abrasion the boom may encounter from marine growth (barnicles etc.) on the dock or ships hull, secondly it increases the catchment area.
These units may be used instead of conventional anchoring. They can help to catch oil that may run off the deck or quay side by holding the boom off a vessels side not allowing wind to push it against the side.
An essential part of this system is a means to remove the oil from the area inside the boom. This may be done by a skimmer. In some systems, the skimmers are incorporated into the boom itself. Aerial observation is essential to get the configuration into a position to collect the thickest of the oil at sea.
This use of booms is normally executed for shorelines. Usually where sensitive environmental areas are concerned. It is necessary to have an adequate point for the collection of oil on the beach. The booms are used to deflect the oil towards that point. After the oil has been deflected, it may be retrieved by skimmers, vacuum pumps or other methods of recovery.
The current speeds on river bends are slower on the inside than the outside. Using this type of boom oil can be moved to quieter water for collection and removal provided there is good access.
Some of the areas that can be protected are listed below
The situations where and how the booms can be used are numerous and varied. However, before a boom is used, it is essential that thorough consideration be given to how the oil is to be recovered.
Adequate access by land or by sea for the deployment of men, boats, ships and equipment is essential.
It is important to have anchors on the booms in order to fix them in position and avoid areas with abrasive surfaces such as barnacles.
The booms for containment used in these cases should have a skirt between 20 to 30 centimetres, freeboard between 15 to 20 centimetres and good resistance to tension, due to the strength of currents.
The most common technique for containment on rivers is to use the river banks to anchor the booms by means of existing points, such as trees, posts, existing construction or steel or wooden stakes driven for this purpose. Trees do not always grow where you require an anchor position, In some countries it is illegal to use trees as anchor points.
For many years magnets of various designs have been used to attach booms to the hulls of ships at thewater line. Obviously as the tide height changes the boom moves with it. Dependent on the design depends on how difficult the magnet is to get off the hull at the end of the job. This type has 4 screws to force the magnet off where as the version right has a cam system.
This Flexy boom™ is built to be under pressure when flexed. When deploying the extremities are bought togetherand placed in the water, it automatically opens and puts pressure on the vessels hull and the quay wall. The boom rises and falls with the tide. they are made in various lengths dependent on situation.
This is a very quick and reliable boom for bunkering operations and removes the need for encircling vessels in ports.
The photo right shows the problem we face. Here with the proximity of this container ship to the booms so the crew can take photo's, the wake when it passes will cause most if not all the oil contained to escape.
In some cases the response companies get fined when the oil leaves the boom. Photographic evidence like this helps you plead you case.
The booms will respond in accordance with the oceanographic and meteor graphic characteristics of the location. Booms will not function well if the speed of the current is greater than 0.7 of a knot for ease 0.5 of a knot or for none seagoing people 1 metre per second. Above this velocity, failure in their capacity to contain oil in the boom starts to occur. With lighter oils these failures can occur much more easily. This can be reduced by reducing the angle of the boom to reduce the pressure on it.
Various inovative types of equipment have been developed for use with exessive current speed. A few of these can be found at the end of the Inland spill section as this is where these currents are normally found.
Effects of current
In common with all of the other mechanical systems, booms are limited by their design and construction, as well as by the natural laws of physics. Booms should be capable of tolerating salt water and oil, with no detriment and also be strong enough to stand up to use and the forces expected in the location where they will be or are likely to be used.
This happens when the quantity of oil contained in the boom surpasses the maximum capacity for which it was designed. When a boom like this is full, if the oil is not remover by skimmers it will find a way of emptying itself by going under the apex as can be seen.
This can also be found with booms which are towed using odd numbers i.e. 3 or 5 boom lengths which puts a connector in the apex of the boom which then acts like a fence boom and with little effort leans over allowing the oil to flow through the gap. To avoid this problem use even numbers which puts the floatation section in the apex.
This also occurs when the boom is towed to fast, the angle of the boom is too obtuse to the current or when the length of the cable tied to the anchor is shorter than five times the depth.
The weight of water on the boom skirt pulls it under allowing all the collected oil to float over the top or in this case through the gap in the boom.
Unfortunately there is always someone available to take photos of good mistakes.
Generally occurs when there are strong winds and strong currents running in opposite directions. Or if there is insufficient weight of ballast chain weight. It also occurs when fence boom is towed or used in currents because the responder knows no better.
In some cases wires are fitted to the top of booms and the weight of the ballast chain is not increased to compensate due to the manufacturers lack of practical knowledge.
Photo left we have a response vessel with a gap between the boom and the vessel which allows the oil to pass through the gap.
The fact that when I took this photo the vessel had her stern to the flow of oil does not help with recovery. This vessel could have won a prize for the cleanest response vessels I have ever seen at an oil spill.
Photo right shows a few of the problems;
1: using an odd number of booms and therefore the connection is in the apex which will cause oil loss.
2: absorbent boom is not a skimmer if it were then it should be in the apex. In this case it is a waste generator, the oil where these vessels were used, was either emulsified or well weathered in either case the oil would be too thick and so the absorbent would just get dirty not impregnated with oil.
3: if oil were collected where on this shrimp fishing boat is it going to be stored.
This is one of those cases where the politics of the spill response are more important than the spill response itself.
As someone said these booms are "eye candy" they look nice even if they don't work. I like the phrase and unfortunately it is done to appease the press who know nothing about the subject. It does nothing for those professional responders who are trying to do the job correctly.
Photos like this just makes you cringe but they are good to demonstrate how not to do it and are easily found on the internet.
Three desirable design aspect
Should be fixed to the skirt of the boom, preferably on the chain or the connection. The faster the current the closer the anchor points need to be to keep the desired angle.
Should be as high as possible; otherwise the oil collected will spill over the boom under conditions of strong currents or high wind speed.
Shape of the boom
Should be as smooth as possible as in photo left, the pockets in this photo right would be filled with oil and it becomes difficult to get it to flow towards the collection area. Heavy oil tends to cling to the boom material making the problem even more difficult.
Protrusions and deformations interrupt the smooth flow of water and oil. These can cause vortex's, which could result in the loss of oil, even at very low current speeds.
In coastal areas, changes in the direction of the current due to the effects of the tide may be expected on a regular cycle. It is important to recognise this fact when installing booms for the following reasons.
A boom, once in position, normally will only be effective for collecting or deflecting oil coming from one direction. Additional booms should be put into position to take into account the different directions of currents due to tidal changes.
Anchors should be set for all booms, so that they stay in approximately the same position, regardless of the direction of the current. This will guarantee that the least damage will be done to the boom, by wear and tear on rocks, etc.
Effect of waves
Waves have an important role in the performance of a boom. Height and frequency have a direct relationship with the construction of the boom and its flexibility. These are specific considerations in order to find out if the boom will succeed in retaining the oil. Inevitably, because booms are constructed with such a variety of materials and designs, it is difficult to establish rigid rules. However, the following general comments should serve as a guide.
The highest part of the wave is called the crest. The lowest part is called the trough.
The wave height is the overall vertical change in height between the crest and the trough and distance between
two successive crests (or troughs) is the length of the wave or wavelength.
While one normally associates an up and down motion with the passage of each wave. Actually, a circular motion occurs. It is this orbital motion of the water (or objects on the surface of the water) that causes an object to bob up and down, forward and backward as waves pass under it.
But even this motion is not exactly circular but is trochoidal (line form traced by a point on a rolling wheel).
While the motion in a wave over deep water move is an almost closed circular path there is a tiny forward motion with the passage of each wave, particularly in large waves.
Also, in deep water, the motion changes as the depth increases fairly rapidly. The trochoidal shape at the surface flattens with increasing depth as well as a decrease in the total motion. This flattening of motion/decreasing size continues with increasing depth until all that remains is a small back and forth movement and even that will cease to be noticed which occurs at one-half of the waves's total length. For shallow water waves, the same flattening in the motion occurs but there is no decrease in the forward/backward motion.
As long as the boom is flexible, these should not cause any problem, except if they are excessively high.
Unless the barrier is very flexible, there is the real chance that “bridges” occur with wave heights significantly above 3 meters and the
oil will pass under the boom.
These occur in restricted waters or after larger waves in open waters, due to local winds. They cause excessive turbulence at the apex of a boom and with the help of the wind, could result in oil spraying over the top.
Booms near the shore need to be placed beyond the breaking waves (surf zone).
These photos show what happens when you try to fight mother nature, you can see clearly in both photos the breaking waves that threw the boom on the shore.
There is always a shortage of boom to protect all sensitive areas, In this case the booms will certainly be damaged and the oil will pass over them. This can only be classed as a waste of valuble resourses.
For those of us that know which spill these photos came from, will also know it was nearly impossible to find a boom doing its job correctly.
These photos show a lack of the very basics of boom deployment. These people obviously were not trained or missed the first talk on how to use boom.
These two photo's below show how a curtain (tube and skirt) boom has much better wave following characteristics than a fence boom in the same type of waves.
It is essential that the deployment be executed in a logical and well organised manner, first of all, in order to facilitate the work and, second and more important, to avoid damage to the boom.
The photo left shows a common mistake which happens when there is a need to get the boom out quickly. Quickly and correctly comes from training.
Below are a number of guidelines that could help in the installation of a boom with the minimum effort and damage.
The need to deploy the boom quickly sometimes causes the boom to have twists in it these will allow the oil to pass through these areas. A slower methodical deployment usually saves time in the long run.
Before the boom is deployed the next length required should be estimated and connected, whether on land or on board of a vessel.
In order to avoid fouling the anchor cables due to wave movement, they should be at least three times the local water depth but the ideal is five times if there is enough rope available.
Where a boom is being used to collect oil or to protect a sensitive area, every precaution should be taken to guarantee that the boom seals with the beach or bank, so that oil is unable to pass by. This is a particularly difficult problem in tidal waters, especially where the bottom is rocky or strewn with boulders. The use of shore sealing booms for the beach protection is recommended.
Much time has been saved with planning beforehand in areas that need booms for protection. The first step is the choice of the ideal locations for the collection of the oil. Permanent points of anchorage for booms will accelerate their installation. It is sometimes possible to position a boom of the correct length with all anchors and ropes cut to length and located in the area for faster deployment.
NOFI Boom Bag™
The Boom Bag™ has been around for more than 15 years, I am still surprised no one else has copied it.
The bag is stored folded on a pallet to reduce space as in the photo on the right. Its consists of a bag with 150m, 200m or 300m of solid floatation boom, the length is dependent on the height of the boom in a zag zag patten inside.
There is a Velcro closure across the end of the bag the Velcro then runs up the starboard side. The extremity of the boom has a sea anchor attached to it and the rope runs behind the Velcro to the tow boat.
The speed of response is the key to reducing the damage cause by a spill, this bag can be towed at 15 knots to the area of the spill. On arrival without reducing speed the sea anchor is thrown overboard it opens the Velcro fastener down the side of the bag and anchors the extremity of the boom allowing it to zig zag out of the bag, as shown in both the diagram and the photo.
Deployment is very fast which is needed. Re-packing takes time it’s a bit like a parachute it has to be packed correctly to know it will work when needed.
A word of caution;
I put a boombag into a 20 foot container, when we came to deploy it 6 months later it had settled into the corrugations of the container and did not want to come back out. To avoid this line the walls with some type of board to give a smooth surface for the bag to slide on.
Boom Vane™ family
Boom Vane™ is an excellent piece of equipment used to deploy booms from river banks or shorelines wit no need for boats or anchors, it may also be used with a vessel.
All BoomVanes are built for maximum performance in water speeds ranging from 1 to 5 knots. All models are self-balancing, no adjustments or trimming is required.
Powered by the water flowing through the vanes as the vessel advances, the Ocean Boom Vane held by a single tow line swings out to an angle of 30 – 35 degrees away from the operating vessel. The Ocean Boom Vane is completely stable and self-trimming at all sweep speeds and through turns, as well as being insensitive to wave action.
The Boom Vane is a device for boom deployment in rivers and other waterways. This powerful yet light response tool allows for rapid deployment of small boom in fast waters, without the use of boats, anchors or fixed installations.
The system can be operated in rivers with heavy traffic as the Boom Vane control rudder allows for speedy and effortless retrieval from midstream.
BoomVane is 1.1m high and was constructed as a cascade of vertical wings mounted in a rectangular frame. Powered by the current flow, the BoomVane, held by a single mooring line only, swings out towards the opposite shore with the oil boom in tow.
This version is .55m high and was designed for operations in shallow waters (less than 1 m / 3'). It may also deployed off a towing vessel to reach near the shoreline with booms and absorbents, where it is too shallow for the vessel to go.
The Ocean Boom Vane enables a single vessel to operate a wide swath sweep with coastal and offshore booms. The area of the vanes allows booms to be operated at much slower speeds.
The Ocean BoomVane is the largest an was designed for coastal and offshore single vessel operations with medium to large oil booms and advancing containment and recovery systems. It enables a single vessel to operate a wide swath sweep with offshore oil booms, in various modes and configurations:
• Over-the-side sweeps on large vessels, trailing sweeps on smaller vessels.
• “U” or “V” boom configuration, as well as closed or open apex.
• From one or both-sides.
A 1.5m version is being developed at the moment.
The photo left shows a basic problem with designers. look closely at the orange float and you will see a green and a red spot. All for the pieces that fit together are colour coded to make life easy.
Green is the international navigation colour for the starboard (Right) side of the vessel looking forward. So you would think that when the boom vane has been put together correctly using the green colour code it would be launched on the starboard side. That is the problem it will only work on the Port (Left) side which is internationally coded red!
Make your life easy; paint the correct colours in the correct place so green goes to green and deploys over the Starbord side and visa versa. Just make sure you paint a different patten so everyone knows it has been modified.
The manufacture has been told of this problem so be aware that new versioon couuld have been changed.
One more problem, not with the equipment but with operating companies being un-professional.
On the photo right we have three problems.
The Japanese came up with a easy way of deploying the Boom Vane™ when being used at sea with Current busters™ etc.
This requires a couple of quick modifications to the equipment:
Connect the Boom Vane mooring line to the triangle as usual.
Connect a shackle to the triangle at the boom connection.
Connect the shackle to the equipment tow rope and allow it to slide back (this may need a bit of help by pulling on the mooring rope to force the equipment open)
There will be pressure on the mooring rope until the Boom Vane arrives at the end of the tow rope then the pressure will be transfered to the tow rope.
To retrieve the Boom Vane stop the vessel and pull it back using the mooring rope (this can be difficult with currents so be carefull)
NOFI Current Buster™ family
In a bid to produce a recovery device that will work in currents in excess of 1 knot. The Current Buster™ was designed. This technology has been thoroughly tested with excellent results and has already proved itself in real oil spill responses such as the photographs taken during a blowout in the
Basically the mouth of the system allows oil to be funneled into the small channel under the joining floats, it the opens into the catchment area where the oil becomes calm enough to recover with conventional skimmers. In this area there is a sheet of material attached to the bottom of the floats with a slit in the middle to allow the water to flow out but leave the oil behind.
After its success came the bigger Ocean Buster™
The latest version is the Harbour Buster™ was designed to operate in a current or towing speed of approximately 2,5 knots and with great manoeuverability in areas with limited space. All versions are based on the same technology.
The manufacturer says the unique technical features of the system enables the operator to contain and recover oil in currents up to 3,5 knots. This is much better than conventional booms.
It needs to be said that it could be more effective if conventional booms were attached to the extremities to give a larger area of encounter. This can only be done by asking the manufacturer to add the boom connections that you use, as they are sold with NOFI connections which only fit NOFI booms.
Below is a diagram that give the dimentions of the three different versions of this system.
The photo top shows the entrance in the recovery area while the bottom one shows the exit flaps, this area is where the R&D money went obviously the measurements are critical for the equipment to work correctly.
In the case of this Harbour Buster the manufacturer says it can be towed at 3 knots. The photo left shows clearly that when towed over 3 knots in the calm water of a port the recovery section starts to sink under the weight of water. If this is not seen then oil will be lost over the top.
I am still at a loss to understand why there is a need to charge around trying to collect oil. We know there is always a difficulty in collecting oil if it is done correctly and with mother nature helping then the result will be be better.
I have been involed in the deployment of all three designs and if used correctly they are excellent devices. It just comes back to training to get them to work for you.
For anyone buying this device, the connections are for Nofi boom so if you use for example ASTM connections then you need to ask for them to be fitted. This is normally not done so you either do nothing o make a connection yourself to increase the front opening.
In 2012 the names changed to 2, 4, 6 and 8. I would have used 15, 22, 34 and 50 so the buyer would know the swath width but what do I know.
Info on changes; http://www.nofi.no
These systems can either be used with two vessels or one vessel and one of the Boom Vane™ versions dependent on the size of the buster.
From a practical point of view the operator needs to keep an eye on the water level in the catchment area as with more speed there is a possibility of breaking the rubber bands in the outlet. If this happens the opening get to big and allows the water and oil to get out like a plug hole.
Just because the manufacture says it can be towed up to 2.5 or 3.5 knots does not mean it has to be towed that fast.
Common sense is needed as with all things.
In my opinion there never has beena need to chase oil at speeds up to 5 knots with equipment with small encounter rates. What is needed is a wide encounter rate at a slower speed.
The photo far left shows an ASTM connection welded onto the Harbour Buster Just below the float.
This allows other manufactures boom to be added as in the photos right.
The photo middle shows the 15m opening of the Harbour buster.
The photo right shows the same buster with 30m of boom attached to each side of the opening effectively widening the encounter rate by 3 times.
Imagine what 100m each side could do, the system is still towed by the buster tow ropes they have just been extended.
While on the subject of NOFI equipment, I have never been a fan of the plastic loop connection which split even during a training exercise in calm water using a small MOS system photo left.
The loops were removed in this case but if you have a sharp knife then slits can be made in the plastic to allow a strong cord to be looped through.
The original white plastic strap was threaded through the loops and then the cord is tightened and the strap is secured with the cord to the tension rope.
This shows yet again the necessity for spare cord and a tool box to be present during either the real incident or training exercises.
Marine Oil Spill (MOS) Sweeper
This is a single vessel system utilizing a paravane to spread the sweeper. It consists of a series of shallow deflectors that push surface oil and water towards the centerline.
At the rear of the sweeper the oil is further concentrated in a so-called reduction channel that prevents splash over from an open surface, where after the oil is recovered and transferred to the vessel through a flexible hose.
Training exercises with the system by use of offshore fishing vessels have gained valuable experience, and at the same time demonstrated the similarity with operation of active fishing gear. The swath width of the offshore prototype is 50 m.
Care should be taken during deployment and recovery as the net can catch on obstructions and cause damage to the system.
This manufacturer deployed this boom to see how it would stand up to bad weather, of course nobody would deploy a boom to operate in these conditions but now you know it will perform well when used in normal conditions.
Another manufacturer in the early days of developement, left booms out in the arctic over the winter where they became frozen in the ice pack and were removed in the spring thaw. This became one of the most robust booms on the market.
In the case of the photo right the manufacture was asked if the boom could be deployed from an FPSO approximately 10 to 15 meters. They decided to deploy 300m from a 70m bridge close by. This shows dramatically that the material can stand up to this type of punishment as well as showing the boom reel has the strength to operate in condition more extreme than would normally be incountered.
Some people can see the value of such objects but others prefer to continue struggling common sence is a rare commodity in many places around the world.
One phrase that has always annoyed me is we have always done it this way.
We have to think of ways to reduce the risks involved during operations as well as the effort needed to do the job.
If one small object can reduce the risk and reduce the amount of people needed to carry out a task then we can do more than one task at the same time.
When starting a team, people from different backgrounds working together will come up with various new ideas. It then come down to the management to have open minds.
The use of air bubble curtains as oil barriers is well-known since the 30's. A pneumatic oil barrier in principle consists of a perforated hose fixed to the river or sea bed, into which compressed air is blown.
These systems maybe attached to an oil detection system and automatically turned on when oil is present on the water surface.
The hose can be installed depending on the local conditions at the bottom or into a ditch within the gravel bed. The bubbles leaking out of the holes rise to the water surface.
The hole diameter, hole spacing and the hose diameter is critical dependent on depth and current flow to provide a constant air flow along the length of the barrier.
The water ascending with the air bubbles causes a current moving away from the barrier in the upper water layer.
This surface current prevents the spreading of the oil film on the water. Wind, waves and currents also affects the oil spreading, so for the effectiveness of a pneumatic oil barrier the consideration of these factors and their physical procedures must be calculated.
As can be seen in the photo left in conditions of low current speed these barriers can be positioned for easy passage of vessels to a terminal and used during loading/unloading operations.
This bubble netting technique has been used by humpback whales for thousands of years to catch herring.
Maintenance on the job
Once the boom has been installed, it is important that its maintenance is performed regularly.
Continuous movement of the boom, due to the water and the wind, will result in wear and fatigue of the boom material and the anchor systems. Where strong currents exist, the dragging of anchors is a possibility.
Theft of anchors by fishermen and boat owners is a real problem in some areas leading to deformed boom configurations and loss of oil.
Photo left shows what happens when you put a boom on a running mooring on the far wall to close the enterance left. Everything is fine until the blue boat owner returns, seeing the boom in the place where he moors his boat, he moves it now when the tide goes out the boom is suspended in the air.
Movement causes wear and could shift the boom from its ideal location, or being totally destroyed.
Below are a number of important locations on booms that should be examined regularly in order to guarantee that they remain intact and operate in an efficient manner.
There are some repairs that can be done during the response, such as small punctures or tears. In the short term stitching the fabric can be done. Glue does not bond with wet or oiled booms. The affected section should be replaced.When major damage is done it is sometimes easier to recycle the connectors and the ballast chain to repair other lengths. Before recycling takes place it is necessary to know whether an insurance company will be paying for the damage. If so they will want to see it in its damaged condition. They also work slowly, it may take weeks or more often months for them to do the inspection. During this time the boom cannot be touched.
Here are two examples of boom being used to collect floating rubbish, the one on the left shows that the boom works well but if the rubbish is not removed the boom will probably part in the middle and let the rubbish go where the boom was protecting.The example on the right is also designed to stop rubbish passing but due to manufacture error the boom lays on the surface and lets the rubbish pass over the top.
Decontamination after the response using degreasing agents as well as high-pressure water jet cleaning require an appropriate place conforming to the pertinent local legislation.
Much of the equipment will also be used for the training of personnel hopefully before a spill occurs in the future. The equipment will need to be free of oil so as not to cause huge embarrassment in front of local dignitaries when oil comes out of a boom chain pocket in the middle of a demonstration. This has happened and clearly shows everyone how unprofessional you are.
Booms are very expensive pieces of equipment ranging from hundred to thousands of dollars per meter. They are also in many cases easy to damage therefore they should be treated with respect when deploying, recovering and use. A damaged boom is of no use to anyone. Some boom system cost more than a Ferrari who would treat one of those badly.
Unfortunately people do things that leave you scratching you head, here are a few photographs that explain what people do mainly through ignorance or just to make life easier for themselves without understanding the consequences.
Here several thousand dollars worth of permanent floatation boom left out in elements. Boom fabric does not like sun and rain for long periods this has been in this position for about 3 years, when the day comes to use it, chances are it will not work.
Left is self inflating boom as spoken about before, this was left unused for a long period of time and when the spring did open it tore the boom material. This is going to take a long time to repair or in the worst case it will be disposed of and new bought to replace it.
Right is a common problem when the weight of the tow is directed to the top of the boom and not to the tension chain or wire at the bottom in this case the material tears thus rendering the boom section useless. These type of problems can be repaired easily when as in both cases the booms are clean but if this happens during an oil spill then we are short of upto 50 meters of boom for the operation we were trying to perform.
Most of these problems arise from not enough training. In this next case when I said we were going to deploy this type of boom I was told that every time they deployed it they tore the ballast chain off.
The white sticker othe reel has a diagram showing how it should be done.Looking at the photo below left you will see the there are three shackles one inside the other. Well there should only be one this action has lengthened the tension chain.
The final small shackle is attached to the boom and not to the steel tow end. This was done because when you start to recover this type of boom there is a lot of tension on the chain to start with so the made it a bit slacker.
I removed the extra two and connected it to where it should have been also knowing that there was a good chance they had done the same at the other end. When we got close to the other end I stopped the deployment tied off the chain so I could connect the shackle correctly.
Having nearly got the pin in place, some nice person told to tow boat to take the strain, in the process I nearly lost my fingers and they successfully ripped the chain off the boom as seen it this photo right.
This brings up the importance of communication during operations and training exercises. If left to one person to direct the operation the boom would have been intact.
Photo left in some cases the manufacture makes the mistake by having the chain slightly longer than the material as in this case, the boom tore up from the bottom into the air tube causing the section to sink.
Photo right Obviously short of equipment when a connector is torn and you have to tie it to another boom with a couple of twists so it will not stop oil at all.
The main problem in many countries outside of Europe is the sun, booms inparticular are made from different plastics which are not resistant to the sun's uv radiation. The main indication of a problem is the change in colour as the sun bleaches the material, it becomes brittle and cracks. Polypropelene ropes left in the sun will stard to disintigrate.
The storage of booms in particular is important mainly to keep the material out of direct sunlight. Here are a few photos showing how not to do it. The light colour shows where the boom has been uncovered and bleached by the sun, the dark orange is the colour it should be not pink!
This section of boom is now scrap, because if it were used the material would know doubt split open and sink.
Left is a serious amount of money tied up in two boom reels where the covers have been damaged by sunlight so it is only a matter of time before the boom material becomes bleached pink and becomes brittle and in this case a section of 25 meters of boom will need to be replaced. New covers are considerably cheaper than new boom.
The photo right remindes me of a training course at Yambu, Saudi Arabia. They had this Troil fence boom which hangs in a frame. The cover had been destroyed by the sun and no one bought another one. While making the boom ready for deployment we noticed that the sun had also damaged the green braided plastic tow rope.
We tried to explain that the deployment would not go very well if the damaged materials were not taken care of, all to no avail.
The tow rope was given to a small tow boat and off he went. The air was full of green dust coming from the sun damaged tow rope. The boom unfurled from the frame and entered the water, as it did the top of the boom material opened and the square white floats floated as the rest of the boom sank to the bottom. Instead of storing it with a cover or just out of the sun the company lost 250m of boom from its inventory.
Unfortunately you are not allowed to take photos in Saudi Arabian terminals. I still have that image in my head.
Left is a boom reel which had a cover that was orange, it does not take long under a tropical sun for this to happen. The boom is made from neoprene which will take even less time to be effected if you do not have room to keep booms under cover you need to buy covers regularly.
Photo right shows a common problem. Usually when the maintenance people do not deploy the equipment. here we have a boom on a reel that has been left in the same position for a long time.
Gravity takes over and the boom sags onto the floor. This makes it very difficult to deploy without doing damage to the boom material. The heavier the boom the bigger the problem for those trying to deploy it.
The remedy is simple using an empty reel in front of the problem reel, turn both at different speeds to add pressure to the boom as seen on the middle photo.
Now monthly turn the reel to stop the gravity problem happening again.
This is especially important when booms are stored for a long time without the oportunities for training.
Here is a section of a Hydrofire boom which belonged to a company in a tropical region.
The white fire resistant material has been eaten by insects until the water hoses became exposed. Covering the boom with a plastic rap material did not help.
For the owner Deepwater Horizon happened and it went to the Gulf of Mexico here it was repaired before being used for that response.
The replacement fire booms will no doubt suffer from the same problem.