# Pg — Gauge pressure

> Source: https://rodlesspneumatic.com/resource-center/pneumatic-glossary/pg/
> Language: en-US
> Category: Pressure & safety

## Definition

Gauge pressure: Pressure referenced to local atmospheric pressure. Do not mix gauge and absolute values in one formula. Read the applicable product data and technical standard before treating a catalog value as interchangeable.

## Key facts

- **Term:** Pg
- **Full form:** Gauge pressure
- **Selection effect:** Do not mix gauge and absolute values in one formula.

## Pg: definition and engineering context

Gauge pressure. Pressure referenced to local atmospheric pressure.

The term belongs to the pressure & safety context. Its exact limits can depend on the cited standard, catalog convention, unit system, reference state, and component configuration.

## Why Pg affects pneumatic selection

Do not mix gauge and absolute values in one formula.

- Cracking pressure: It affects low-pressure operation and retained pressure.
- Proof pressure: It is not the normal operating-pressure rating.
- Burst pressure: Never use it as a working-pressure target.
- MAWP: Use the lowest rating of every component in the circuit.

## How to evaluate Pg in a catalog or replacement project

Read the value together with its unit, test basis, operating pressure, temperature, circuit state, and manufacturer definition.

For replacement work, compare the complete datasheet and drawing. A matching abbreviation or nominal size does not by itself prove functional or dimensional interchangeability.

- Initial opening pressure: Differential pressure at which a check or relief element begins to open.
- Proof test pressure: Pressure used to verify integrity without permanent deformation under stated conditions.
- Failure pressure: Pressure at which a component may rupture or lose containment.
- Maximum allowable working pressure: Highest permitted working pressure under specified conditions.

## What to verify before selection

- Do not mix gauge and absolute values in one formula.
- It affects low-pressure operation and retained pressure.
- It is not the normal operating-pressure rating.
- Never use it as a working-pressure target.

## Common mistakes

- Treating Pg as a universal definition without checking the manufacturer or standard context
- Mixing gauge and absolute values, incompatible units, or different reference conditions in one comparison
- Selecting a component from the term or nominal value alone without checking the complete operating point and drawing

## Frequently asked questions

### What does Pg mean in pneumatics?

Gauge pressure. Pressure referenced to local atmospheric pressure.

### Why does Pg matter when selecting a component?

Do not mix gauge and absolute values in one formula.

### Can Pg values be compared directly between catalogs?

Only after the unit, reference condition, test method, operating point, and manufacturer definition have been reconciled.

## Technical references

- [ISO 5598:2020](https://www.iso.org/standard/67985.html): Provides the international fluid-power vocabulary used to interpret pneumatic terminology.
- [ISO 4414:2010](https://www.iso.org/standard/44790.html): Provides general rules and safety requirements for pneumatic systems and components.