The end cap is the end cap on the pressure vessel and is a major pressure-receiving part of the pressure vessel. The role played is sealing. One is to make the top and bottom of the tank-shaped pressure vessel, the second is the pipe to the head, not ready to extend forward, then use a sealing head to seal the pipe in the form of welding. Products with similar functions to the head have blind plates and caps, but the two products are detachable. After the head is welded, it cannot be dismantled. The supporting fittings include pressure vessels, pipes, flanges, elbows, tees, and four-way products.