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Pressure Vessel Repairs and Alterations

There are special requirements needed to repair or alter pressure vessels fabricated of tempered (UHT) and quenched materials. The most frequent repairs and alterations are done on over-the-road LPG (Liquid Petroleum Gas) transport vessels. These are the areas of consideration when repairing or altering tempered and quenched materials.  At Outweld Industries Inc., we guarantee our projects will meet all industry standards and exceed your expectations.

• Nozzle Design and Other Connections - All nozzle welds must be full-penetration design. There are specific requirements for attachment, geometry, and nozzle material details as well.

• Materials – All materials must be impact-tested in the final heat-treated condition. Sometimes additional drop weight tests are required basing on the minimum temperature of the metal design.

There are thickness limitations on specific materials that cannot be exceeded.

• At one time, only Ferritic Steel with Heat Treatment (UHT) could be used to join shell and head sections. It is now permissible to join UHT materials to Carbon and Low Alloy (UCS) or High Alloy Steel (UHA) materials in the shell and head sections.

• Reinforcement pads and nozzles need to be made of specific minimum strength material that is within ±20 percent of the shell to which it is attached. Communicating chambers, pipe or pipe flanges can be high or low alloy steel or carbon steel that is welded to nozzle necks as long as the rules of UHT are satisfied.

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• Welding Procedure Qualification – We review the requirements and are familiar with the rules governing repairs and alterations.

Any surface cut by a metal melting method, that is not going to be re welded, has 1.5 mm removed by mechanical means such as grinding. It is inspected by magnetic powder (MT) or penetrant testing (PT) after being ground.Temporary welds are removed after serving their purpose. The maximum weld reinforcement will not be more than the lesser of 3.0 mm or ten percent of the thickness of the plate. The base metal is restored to a smooth contour.

• Other Procedures – There are also requirements for Nondestructive Examination, Post Weld Treatment, and Nameplates. For any repair or alteration of pressure vessels, we refer to the Code of specific requirements that pertain to any material we use.