How to Determine Whether a Non-Metallic Gasket Needs Replacement？

Non-metallic gaskets (such as rubber, graphite, PTFE, asbestos, etc.) are widely used in sealing parts such as pipes, valves, and pump bodies. Aging or damage to them can lead to leakage, equipment corrosion, or safety accidents. Understanding the key indicators and inspection methods of non-metallic gaskets that need to be replaced can ensure that the non-metallic gaskets are stable during use.

1. Visual inspection (direct observation)

(1) Surface cracks or cracks

Phenomenon: Obvious cracks, delamination, or embrittlement appear on the surface of the gasket.
Cause: Long-term pressure, high-temperature oxidation, or chemical corrosion.
Risk: Seal failure and possible sudden leakage.

(2) Compression deformation or thinning

Inspection method: Compare the thickness of the new/old gasket (measured with a caliper).
If the thickness decreases by more than 20% after compression (e.g., the original thickness is 3mm, now <2.4mm), it needs to be replaced.
Cause: Long-term pressure causes the material to lose its resilience.

(3) Edge damage or blistering

Phenomenon: The gasket edge is torn, blistered, or partially bulged.
Cause: Improper installation, medium corrosion or uneven expansion at high temperature.

2. Leak detection (indirect judgment)

(1) Medium leakage

Liquid/gas leakage: dripping, scaling or rust is found at the flange connection.
Note: Minor leaks may only appear as moisture or crystallization (such as brine pipes).

(2) Pressure test

Method: After the system is pressurized, maintain the pressure and observe whether the pressure gauge continues to drop.
Standard: Chemical pipelines usually require a pressure drop of less than 5% within 30 minutes.

3. Changes in physical properties

(1) Hardness change

Detection tool: Shore hardness tester (such as an increase in the hardness of a rubber gasket indicates aging).
Standard: Hardness changes exceeding ±10% require replacement (such as the original hardness of 70HA, now >77HA or <63HA).

(2) Rebound test

Method: Press the gasket and release it to observe whether it returns to its original shape.
Failure manifestation: After deformation, it cannot rebound and appears in a "flat" state.

4. Impact of Environment and Working Conditions

(1) Excessive Temperature

Phenomenon: Gasket carbonization (blackening), melting (e.g. PTFE exceeding 260°C) or hardening.
Countermeasure: Replace with a material that is resistant to higher temperatures (e.g. graphite gasket).

(2) Chemical Corrosion

Phenomenon: Gasket surface swelling, discoloration or stickiness (e.g. rubber encounters oily media).
Check: Compare with the media compatibility table (e.g. NBR rubber is not resistant to ketone solvents).

5. Replacement standards for non-metallic gaskets