The Definition of Pressure Vessel Safety

Definition of Pressure Vessel Safety

Pressure vessel safety is the set of design, fabrication, inspection, maintenance and operating practices that prevent containers holding gases or liquids at pressure from failing. Pressure vessels include air receivers, reactors, separators, heat exchangers, storage bullets, autoclaves and boilers. Because they store large amounts of potential energy, a rupture can cause explosions, fragments, toxic or flammable releases and fatalities.

In the U.S., most pressure vessels are designed and built to the ASME Boiler and Pressure Vessel Code, Section VIII, and in-service inspection and repair often follow the National Board Inspection Code. States and cities set their own registration and inspection rules, while OSHA addresses specific items such as compressed air receivers in 29 CFR 1910.169.

Key Facts About Pressure Vessel Safety

• Every vessel has a maximum allowable working pressure (MAWP) stamped on its nameplate.
• Relief valves or rupture discs provide overpressure protection and must be sized, set and tested correctly.
• Corrosion, fatigue, cracking and modifications without engineering review are common causes of failure.
• Non-destructive testing, such as ultrasonic thickness readings, tracks wall loss over time.
• Vessels must be depressurized and isolated before maintenance.

Example of Pressure Vessel Safety

An inspection of a plant air receiver finds that the drain valve has been seized for months, allowing water to collect and corrode the shell. Ultrasonic testing shows wall loss, so the receiver is removed from service and replaced, and a weekly drain check is added to the pre-use inspection list.

How to Manage Pressure Vessel Safety

1. Keep an inventory of vessels with nameplate data, MAWP and inspection due dates.
2. Comply with jurisdictional registration and inspection requirements.
3. Inspect and test relief devices on a set schedule.
4. Use non-destructive testing to monitor corrosion and cracking.
5. Route repairs, alterations and setpoint changes through management of change.

Related Terms

• Overpressure Protection
• Boiler Safety
• Gas Cylinder Safety
• Non-Destructive Testing (NDT)
• Explosion Hazard

Frequently Asked Questions: Pressure Vessel Safety

Does OSHA have a pressure vessel standard?

OSHA has no single general standard for all pressure vessels. It covers specific equipment, such as air receivers, and relies on recognized codes like ASME and the General Duty Clause. State and local codes usually govern inspections.

How often should pressure vessels be inspected?

Intervals depend on jurisdiction, service and condition, commonly every one to five years for internal or external inspections, with more frequent checks of relief devices and drains.

What does the ASME U stamp mean?

It shows the vessel was built and inspected to ASME Section VIII, Division 1 by an authorized manufacturer.