Vessel engineers first use the design pressure to find the required thickness of all components on a vessel. Next, normally a stock plate or pipe thickness is chosen for each vessel component that is higher than the exact minimum required. Because there is excess thickness in each part, the designer can then back-calculate the highest pressure the vessel can hold. This pressure is known as the MAWP or maximum allowable working pressure. MAWP is always equal to or higher than design pressure.
Many vessel owners want this higher calculated MAWP stamped on the nameplate, so they can use the vessel in higher pressure service if needed. But other owners prefer to rate the vessel only for the design pressure, which means that any extra thickness in each component can then be used as additional corrosion allowance. This method could extend the service life of the vessel. Contact us if you have any questions about MAWP and stamping options.