A prominent company’s agricultural chemical division struggled for years with the difficult handling process utilized for loading and unloading a highly corrosive material into small containers. Their process required filling 100 plastic drums with this acidic material which normally took 8-10 hours to complete and tied up more resources than desired. The issues with this process of small container loading caused the project engineers to reevaluate the situation and consider alternative solutions.
Their search led to the fluoropolymer lining of a larger container. The container finally selected was a 4000 gallon tank trailer lined with Ethylene Chlorotrifluoroethylene (ECTFE), otherwise known as Halar, sheet material that resists corrosion from a wide range of strong acids, alkalies, metal etchants, liquid oxygen and organic solvents.
ECTFE (Halar) was selected for this application not only for the excellent permeation resistance and durability, but also for the significant cost and time savings provided in comparison to the small container process. The tank trailer, 48’ long and 4’ in diameter and designed for operation at 50 psig and 220°F, was sent to Electro Chemical Manufacturing (ECM) for installation of the ECTFE lining.
The ¼” thick carbon steel surface was sandblasted to facilitate a strong bonding base, primed, and multiple coats of a specially formulated elastomeric adhesive was applied to both the tank trailer surface and the knit glass backing of the 90-mil thick ECTFE tank lining.
The ECTFE sheets were supplied in 48” wide by 50’ long rolls, and custom shapes were cut to minimize the number of joints. Instead of abutting or overlapping the sheets, a 1/16” to 1/8” segment was left between the adjacent edges that allowed the sheets to be heated and rolled against the tank trailer wall and the adhesive to set to maximize bonding and eliminate any trapped air. ECM also ensured a pin-hole free lining by using a gas welding process including 1/8” diameter ECTFE weld rods. Once this was completed, all excess ECTFE was ground away leaving a flush and smooth surface.
In addition, joints were never made at corners to mitigate excessive stress in the welds. The ECTFE sheet was rolled over all corners and joints were developed several inches away on the flat surfaces. Then the entire application was inspected visually for surface defects, the dimensions and tolerances were inspected and all lined areas tested with a dielectric spark tester adjusted to 10,000 volts AC.
The client gained great benefits from this ECTFE lined tank trailer solution. After a process that required 8-10 hours, filling the ECTFE lined tank trailer was complete within thirty minutes. This provided significant cost savings, and the project engineers involved have reported no issues after more than eighteen months of usage.
Due to the precise and reinforcing measures taken in installing the strong corrosion protection lining, the service life should extend for years to come. If repairs are ever needed from damage done during service, all that is required is to cut out the damaged area, apply another ECTFE sheet of the same dimensions and repeat the welding process described above. The ECTFE lining meets all the requirements of the ICC and Department of Transportation.
