A connection common in the oil industry consisting of two joints coupled by a threaded nut. Protrusions on the nut are hit with a sledgehammer to tighten the connection and energize the seals. Hammer unions are commonly used on treating iron because of their ability to be quickly made up or broken down.
Hammer Lug unions, or WECO couplings, as they are called, allow for quick connecting the pipelines and flexible hose assemblies in the oil and gas industry. They are popularly used on onshore and offshore drilling rigs to transfer petroleum, gas, drilling mud, cement, water, air and many other media.