API 510 key terms

An industry standard that specifies requirements for in-service inspection, rating, repair, alteration, and rerating of pressure vessels, including rules for owner/users, inspectors, and repair organizations.

The entity legally responsible for the pressure vessel, including its operation, maintenance, inspection program, and ensuring that all code-required activities are performed by qualified personnel.

A person certified by API to perform API 510 inspections, evaluate results, and approve repair, alteration, and rerating plans for pressure vessels within the code's scope.

The credential issued by API after an individual passes the required examination and meets education and experience criteria; it must be renewed periodically to remain valid.

A company that performs repairs or alterations on pressure vessels and is responsible for complying with API 510, including using qualified welders, approved procedures, and proper documentation.

The governmental or regulatory body with legal authority over pressure vessel installation and operation; its requirements may supplement or take precedence over portions of API 510.

The highest internal pressure permitted at the top of a pressure vessel in its normal operating position at the coincident operating temperature, based on the weakest pressure-retaining component.

The stress value from the applicable construction code at the design temperature, used in design equations to calculate required thickness and establish pressure ratings.

The wall thickness needed to withstand design pressure at the allowable stress, including corrosion allowance and structural requirements; it is the limit below which a component must be repaired, reraited, or retired.

Extra wall thickness added to the minimum required thickness to compensate for expected metal loss over the vessel's design life.

The rate at which metal thickness decreases, typically expressed in inches or millimeters per year, calculated from thickness measurements taken over a known time interval.

The estimated time before a component reaches its minimum required thickness, calculated by dividing the difference between current thickness and minimum required thickness by the corrosion rate.

The maximum allowable time between inspections, based on remaining life and code limits; it generally cannot exceed half the remaining life or ten years, whichever is less.

A detailed examination of the interior of a pressure vessel by an inspector to identify corrosion, cracking, or other damage that could affect its integrity.

A visual and dimensional examination of the exterior of a pressure vessel, including supports, insulation, and attachments, to detect leaks, corrosion, or mechanical damage.

An inspection performed while the vessel remains in service, using external or non-intrusive methods, when internal inspection is impractical and alternative coverage is acceptable.

A risk assessment methodology used to prioritize inspection activities and set intervals, focusing resources on vessels with the highest likelihood and consequences of failure.

A specific point on a pressure vessel designated for repeated thickness measurements or other monitoring to track corrosion or damage progression over time.

The determination of wall thickness at designated locations using ultrasonic or other nondestructive methods, used to calculate corrosion rates and remaining life.

Inspection methods such as radiography, ultrasonic testing, magnetic particle testing, and liquid penetrant testing that reveal surface or internal discontinuities without damaging the component.

A pressure test using water or another liquid to verify the strength and tightness of a pressure vessel at a specified test pressure.

A pressure test using air or another gas, permitted only when hydrostatic testing is impractical, and requiring extra safety precautions because of stored energy.

A device designed to protect a pressure vessel from overpressure by automatically releasing fluid; examples include pressure relief valves and rupture disks.

A spring-loaded valve that opens automatically at a preset pressure to discharge fluid and prevent overpressure, then closes when pressure falls below the reseating pressure.

A non-reclosing pressure relief device that bursts at a predetermined pressure to relieve overpressure, often used alone or in combination with a pressure relief valve.

The inlet pressure at which a pressure relief device is adjusted to begin opening under specified conditions; it is a key parameter for overpressure protection.

The pressure increase above the maximum allowable working pressure that a pressure relief device allows during discharge, typically limited to a specified percentage of MAWP.

The difference between the set pressure and the reseating pressure of a pressure relief valve, often expressed as a percentage of the set pressure.

The restoration of a pressure vessel or component to its original condition or to a condition that meets the applicable code, without changing its design or rating.

A change to a pressure vessel that affects its pressure-retaining capability or alters its design, such as changing dimensions, adding nozzles, or changing service.

A change to the maximum allowable working pressure or temperature of a pressure vessel, based on new calculations or an engineering evaluation, with proper documentation and approval.

A written document that specifies the welding variables for a particular welding process to ensure repeatable, code-compliant welds; it is qualified by a procedure qualification record.

A record of the actual welding variables and test results used to qualify a welding procedure specification, demonstrating that the procedure produces acceptable welds.

Controlled heating and cooling of a welded component after welding to relieve residual stresses and improve material properties, often required by the construction code.

The lowest temperature at which a pressure vessel is designed to operate without risk of brittle fracture, considering material toughness and impact testing requirements.

An engineering evaluation that assesses whether a damaged or corroded component can safely continue operating under specified conditions for a defined period.

A documented program that defines inspection methods, locations, intervals, and acceptance criteria for a pressure vessel, developed by the owner/user.

A metal plate attached to a pressure vessel that displays key design information such as MAWP, design temperature, material, and manufacturer.