14 March 2019
Choosing the Correct Fabric for your Boom
by Andrew M. Crawford, SVP
Having worked in this industry for a number of years, a question that I am regularly asked is, “what is the best boom fabric to be used on my project”. The answer is that there is no right or wrong, but there are a few things to understand about the options you have before you make your choice. In years gone by, there were just 3 fabrics to choose from:
- Polyvinylchloride (PVC)
- Polyurethane (PU)
- Polychloroprene (CR) or (Neoprene)
The choice between these three materials was then quite easy. PVC was for cheap short life boom. PU the more expensive fabric with superior chemical and abrasion resistance for the Oil Spill Response Organisations and the multi time users. Principally coastal and inshore work and then Neoprene for offshore booms and the big stuff. However, times have changed and there are a multitude of choices now and not everyone is aware of the differences.
Firstly, there are 2 components of the boom fabric, the scrim and the coating. The scrim sometimes called the base fabric, is quoted like this “Polyester High Tenacity 1100 dtex – 990 deniers” or “Polyamide High Tenacity 1880 dtex – 1710 deniers” this provides the strength to the fabric.
Next we have the coating and this provides the protection for the scrim (the booms strength) against the elements, light, abrasion, chemicals etc. and so the thickness of the coating and material of the coating will determine how well the scrim (boom strength is protected) so these two elements together will form the weight of the boom fabric which is quoted in grams per square meter (gsm) or ounces per square yard (oz/yd). So typically fabric one could be “Polyamide High Tenacity 1880 dtex – 1710 deniers 1500 gsm” and fabric two could be “Polyamide High Tenacity 1880 dtex – 1710 deniers 1765 gsm”. Polyamide is actually more well known as Nylon. So this would mean that the fabrics were both the same strength but the coating on the second fabric thicker so gives better protection to the scrim. So fabric 1 better offshore where abrasion would not be so much of an issue and fabric 2 better for coastal and inshore where abrasion would be an issue. The question “which is stronger boom fabric neoprene or PVC “ is difficult since the strength depends on the scrim and how the boom is manufactured and not on the coating.
Today the choice of coatings is endless:
- Polyvinylchloride (PVC) This fabric is the cheapest. PVC is a naturally hard material and to make it soft it is mixed with plasticizers, which make the material soft and pliable. It is the plasticizers you can smell in PVC. Over time these plasticizers get bleached out of the PVC due to sunlight or exposure to hydrocarbons and PVC reverts to its natural state as a hard and inflexible material and therefore cracks destroying its strength and air tightness.The life of PVC is totally dependent on the quality of the material in the first place and the conditions that it has been kept in. Generally, 5 years is about the usable lifespan of the material. PVC does not handle extremes of temperatures well, unless specifically blended for this application. Manufacturing process of structures is by welding or by sewing. Repairs are easy when the boom is new, if there is a reasonable thickness of coating but as the boom ages it becomes more difficult and impossible when the fabric becomes hard and brittle.
- Polyurethane (PU) this material is still certainly the best boom coating as it does not contain significant plasticizers and has the best abrasion and chemical resistance of any material. It remains supple for its life and I have seen many booms 20 years old, still in good working condition. The down side of PU is that it is expensive. Manufacturing process of structures is by welding or by sewing. Repairs by welding or heat gun are easy when the boom is new, if there is a reasonable thickness of coating but as the boom ages, then it needs to be done with cold glue method. The boom fabric never becomes hard or brittle.
- Alloy of Polyvinylchloride and Polyurethane (PUA) this material is very popular now as the boom makers can advertise the booms are made from a PU fabric which is of course true in part because it is an alloy. The properties of this alloy depend totally on the percentage of materials in the alloy and I would say that fabrics with 5 or 10% PU, the alloy behave in a very similar way to the major constituent. You would need a minimum 20% PU in the mix to see any advantage from the alloy. Manufacturing process of structures is by welding or by sewing. Good repairs are generally difficult but not impossible when the fabric is new, but when the fabric becomes old the only way is by using the cold glue method.
- Polychloroprene (CR) or (Neoprene) This material is expensive but often used in in offshore application because of its high strength and ability to be fabricated into detailed structures by the vulcanising process that PU and PVC cannot. Manufacturers have 2 trains of thought here: one with light fabric 990gsm, which makes a light boom with high buoyancy to weight ration but poor strength, abrasion and chemical resistance by virtue of the very thin scrim and coating and potentially shorter life. The other is to have a heavy fabric with lower buoyancy to weight ration but stronger scrim thicker coating, thus providing a stronger boom with better abrasion, chemical resistance and a longer life.Repairs to the booms are easy and highly successful using hot vulcanising process however this requires a special glue that has a short shelf life and special packing to ship which causes long delays in the repair process. Field repairs are possible with cold glue. The age and condition of the fabric will dictate the success of the repair by vulcanising process and if this fails, then again use cold gluing.
- Chlorosulfonated Polyethylene (CSM) or (Hypalon) This coating for neoprene has superior characteristics for chemical and abrasion resistance. It also has better resistance to sunlight and the elements. Cost is an issue here as it tends to be quite expensive and have limited availability. We make our Floating barge tanks from this fabric which has Hypalon on one side and Neoprene on the other.
Repairs to the booms are easy and highly successful using hot vulcanising process. The age and condition of the fabric will dictate the success of the repair by vulcanising process and if this fails then use cold gluing.
There is plenty of further reading about booms and boom fabrics and the ASTM D751 Standard Test Methods for Coated Fabrics will give lots of info on the test procedures and ASTM F 1093 Standard Test Methods for Tensile Strength Characteristics of Oil Spill Response Boom.
At Lamor, we are always trying to research and use the best available technology (BAT) and this also translates into boom fabric from the point of view of both cost and performance. However, just remember and check with an industry professional that the boom you identified is suitable for the application and the environment that you are putting it into. Today a lot of emphasis is put on the price and we all know from our experience in all walks of life that the most economical solution is not always the best and should it fail it, will create another problem.
Call any one of our offices and we will give you the best advice for your application.
-Andrew M. Crawford, Senior Vice President, Lamor Corporation