Why do non-metallic gaskets need to be cleaned?

Cleaning non-metallic gaskets is a critical step in ensuring reliable flange connections, safe operation, and extended equipment life. Neglecting this step can lead to serious consequences, ranging from minor leaks to catastrophic downtime or safety incidents.

1. Ensure an absolute seal to prevent leaks

This is the most direct and important reason.
Remove solid particles: Any dust, sand, old gasket debris, or metal shavings remaining on the gasket or flange surface can act as "fulcrums" when bolts are tightened.

These hard particles can:
Local embedding：Embedding into the soft gasket material, creating leakage pathways.
Impeding uniform compression：Preventing the gasket from being compressed evenly at the particles, resulting in insufficient sealing pressure in that area.
Damaging the gasket surface：Scratching the delicate sealing surface of the gasket.

Removing oil and chemical contaminants: Grease, lubricating oil, or old sealant can:
React with the medium：Reacting with the medium being transported in the pipeline (especially chemicals), causing the gasket material to swell, soften, or degrade, leading to failure.

Reduced Friction: Affecting the necessary friction between the gasket and the flange face makes the gasket more susceptible to "blowout" or displacement under pressure or temperature fluctuations.

2. Achieving Uniform Bolt Load and Stress Distribution

Non-metallic gaskets (such as graphite, PTFE, rubber, non-asbestos fibers, etc.) require plastic deformation through bolt tightening to fill microscopic unevenness on the flange surface.

Contamination Leads to Stress Concentration: If there are contaminants on the gasket or flange face, the load cannot be evenly distributed across the entire gasket sealing surface after bolt tightening. Points with contaminants will experience abnormally high stress, while other areas will experience insufficient pressure.

Consequences: This uneven stress can lead to localized over-compression (permanent damage) or under-compression (direct leakage) of the gasket, significantly shortening its lifespan and increasing the risk of leakage.

3. Prevention of Chemical Corrosion and Physical Damage to Gasket Materials

Many non-metallic gaskets are highly sensitive to contaminants.

Chemical Compatibility: For example, when conveying strong oxidizing media (such as chlorine and oxygen), any oil contamination on flanges and gaskets is extremely dangerous and may cause combustion or explosion. "Oil-free" cleaning is essential in such cases.

Swelling and Aging: Mineral oil may cause swelling in some rubber gaskets (such as NBR), reducing their strength and sealing performance.

4. Ensuring Operational Safety and Environmental Compliance

Safety Risks: Leaked media may be flammable, explosive, toxic, or corrosive (such as vapors, acids, alkalis, and hydrocarbon gases). A small leak caused by improper cleaning can develop into a fire, explosion, or poisoning incident.

Environmental Regulations: Almost all industrial sectors have strict environmental regulations prohibiting the leakage of hazardous substances. Reliable sealing is fundamental to meeting these regulations.

5. Extending the Service Life of Gaskets and Equipment

A gasket correctly installed on a clean, flat flange surface can operate stably throughout its design life. A gasket installed in a contaminated environment will fail prematurely due to uneven stress, localized damage, and chemical attack. Frequent gasket replacements not only increase spare parts and labor costs but also lead to unplanned downtime, causing significant production losses.

6. What precautions should be taken during cleaning?

Choose appropriate tools: Use a lint-free cloth, plastic scraper, or bristle brush. Avoid using wire brushes, as they may scratch soft metal flange surfaces or the gasket itself, resulting in metal particle contamination.

Use appropriate solvents: Select a suitable cleaning agent (such as acetone, alcohol, etc.) based on the type of contaminant, and ensure that the cleaning agent is compatible with the gasket material and will not dissolve or deform it. Allow the solvent to completely evaporate after cleaning.

Inspect the flange surface: Cleaning is also an ideal time to inspect the flange surface for scratches, dents, corrosion, or radial penetration damage. Defective flange surfaces cannot guarantee a seal even with a new gasket.