Pressure vessels and tanks usually have a relatively thin shell, which has cylinder or ball shape. They are often equipped with valves for filling and draining. Requirements for tightness of these products may be very stringent. Depending on the application and operating conditions 100% x-ray inspection of all joints may be needed.
These tanks and pressure vessels may be manufactured with the use of different processes, including those, which require industrial gases. For example, steel plates for external shell fabrication may be cut using gas, plasma arc or even laser cutting process depending on the type of shell material and requirements for part preparation for welding.
Other arc welding processes (MIG-MAG, TIG, plasma arc welding) may be used for assembling. Gas welding may also be applied as a method of gas flame treatment and sometimes even laser welding is required. Welding process and relevant gas type selection shall be based on the type of material, welding conditions, equipment availability etc.
No indications or residual strains (buckling) are allowed in pressure and tanks due to peculiarities of their operation. Before being re-welded, local welding defects in large items may be efficiently removed by a gas process called flame gouging. Flame straightening, which is another gas flame treatment process, may be used for stress relieving of steel. If it is applied by a qualified operator using proper equipment, this process may be very time and money saving