View Tameson's range of tank truck couplings. TW Couplings or Tank truck couplings are asymmetric couplings to connect hoses mainly for loading and unloading tank trucks. Couplings used on tank trucks are standardized throughout Europe through the EN 14420-6 standardization. The couplings consist of a male and female thread, which can be connected by turning the clamping lever and seal into the female part's crown. After turning, the clamping lever is locked into place, thus creating a secure connection. These couplings are free to flow with 50, 80, or 100mm nominal width and available in both 316 stainless steel and brass.