Abstract: Conventional apparatus for forming pressure vessels from tubing involves a separate step of the forming of the tubing into coils and then separately welding the coils together. The conventional method has proven to be costly because of the type of apparatus required as well as time consuming and frequently producing a poor quality product when the welding is done independent of coiling step. The subject apparatus overcomes these problems by providing a collapsible mandrel to which tubing is wrapped to form coils for a pressure vessel and simultaneously welding the coils together in one step. The coils are guided on the mandrel by a carriage means which is controlled by a hydraulic system to maintain the coils into intimate contact with each other as they are being welded together. A welding torch, also carried by the carriage, is guided by the forming of the coils rather than some guide means to guide the welder independently of this operation.