Parkersburg, WV--Unloading anhydrous hydrogen chloride from tank cars can prove a hazardous undertaking. Therefore, any measure designed to make that task safer merits a closer look. And, if you can produce a less costly operation in the bargain, you have a winning design.
That's what took place at a DuPont plant recently when the company began using a new hose with two concentric liners to provide a double layer of protection against any leaks while transferring the highly toxic gas. A key to the success of the hose hinges on the use of two fluoropolymer resins made by DuPont Fluoroproducts (Wilmington, DE).
The hose, Fluoroflex(reg) DLH, has a convoluted inner liner of DuPont Tefzel(reg) ETFE fluoropolymer within a nonconvoluted liner of DuPont Teflon(reg) PTFE fluoropolymer. The dual-layer construction leaves an annular space between the liners. This is monitored through a port in an end fitting to detect leaks. Crane Resistoflex Co. (Marion, NC) makes the hose.
In addition to the fluoropolymer liners, the hose has a braided outer covering and end fittings made of a corrosion-resistant metal alloy. An optional interlocked metal kink protector fits over the braid.
The hose incorporates one-inch NPS treaded fittings and has a nominal inside diameter of 0.94 inch (223.8 mm), a nominal outside diameter of 1.5 inch (38.1 mm), and a bend radius of 9 inches (229 mm). Working pressure ranges up to 375 psi.
The dual hose also provides more protection of product quality. The hose used in the past failed to withstand the full vacuum required for purging contaminating air and moisture. The new hose is rated for full vacuum and can be completely purged.
As an added bonus, the DLH hose promises to reduce costs. "In the past, we had to replace single-wall hoses annually as a preventive measure," explains Arthur Sweet, a DuPont engineer.
The dual hose should save maintenance costs by remaining in service indefinitely, unless monitoring of the space between liners reveals leakage from the inner layer. If a leak does occur, the outer layer will act as a barrier against emissions.