ANSI (American National Standards Institute) flanges are widely used in industrial piping systems to connect pipes, valves, and equipment. Proper maintenance is crucial for ANSI flanges to prevent leaks and failures. This article provides best practices for maintaining ANSI flanged connections.

Importance of ANSI Flange Maintenance

Regular maintenance of ANSI flanges is important for several reasons:

• Prevents leakage which can be hazardous and lead to lost production.
• Avoids bolt failures that can cause flange separation.
• Maintains proper bolt preload to prevent flange gasket creep.
• Extends service life by reducing corrosion and wear of flanges.
• Lowers costs by preventing unplanned downtime and replacements.

ANSI Flange Maintenance Schedule

A maintenance schedule must be developed based on:

• New installations - after 24 hours, one week, then quarterly in the first year.
• Existing flanges - monthly or quarterly inspection initially. Increase inspection frequency for older flanges or problem areas.
• Critical services - weekly or fortnightly inspection for services that cannot tolerate any leakage.
• Flange size - Large-diameter flanges need more frequent inspections.
• Operating conditions - higher pressures and temperatures accelerate wear so need frequent checks.

ANSI Flange Visual Inspection

A close visual examination of ANSI flanges should check for:

• Leakage - bubbles, water droplets, or fluid stains around the flange gasket.
• Bolt damage - corrosion, wear, deformation, or fatigue cracks.
• Gasket deterioration - hardening, shrinking, erosion, or blowout.
• Flange face damage - pitting, galling, cracks, or wear.
• Flange misalignment - tilting, warping, or distortion.

ANSI Flange Bolt Tightening

Loose bolts must be re-torqued to specification. Useful tips include:

• Have proper torque wrenches for accuracy.
• Follow the right bolt tightening sequence.
• Do not over-tighten to avoid flange damage.
• Adjust torque for lubricated bolts.
• Replace worn-out bolts and washers.

Gasket Maintenance

Gaskets form the heart of the flange seal. Below are some gasket maintenance guidelines:

• Look for gasket creep, shrinkage, hardening, or channeling.
• Replace compressed gaskets before they extrude from the flange.
• For critical services, install new gaskets during reassembly.
• Keep spare gaskets as per flange size and service conditions.
• Store gaskets properly to prevent damage and contamination.

Flange Face Maintenance

Flange face condition impacts gasket sealing. Useful face maintenance tips:

• Refinish flange faces if scratched, indented, or warped.
• Replace flanges with excessive pitting, erosion, or cracking.
• For frequent breakdowns, use harder flange-facing materials.
• Avoid rotating flanges under pressure to limit facing damage.
• Use protective flange guards in services prone to erosion.

Corrosion Prevention

Corrosion is the top cause of flange failures. Some ways to prevent corrosion:

• Use suitable flange materials like stainless steel for corrosive services.
• Coat carbon steel flanges with epoxy or zinc plating.
• Look for corrosion signs during inspections.
• Isolate flanges from dissimilar metals to avoid galvanic corrosion.
• Keep flanges properly lubricated.

Flange Leak Testing

It is good practice to periodically pressure test flanged assemblies. Tips for leak testing:

• Isolate the flange section and pressurize with water.
• Apply soapy water and look for bubbles to detect leaks.
• Slowly increase the pressure up to the design rating.
• Mark and retighten any leaking flange bolts.
• Repeat the test until no leaks are observed.

Flange Replacement Decision

Flanges should be replaced if excessive:

• Leakage that cannot be stopped by tightening.
• Bolt deterioration or stretching of bolt holes.
• Face gouges, pitting, or erosion beyond limits.
• Warping that leads to misalignment.
• Cracking or other damage.

ANSI Flange Record-Keeping

Maintaining records is vital for managing flange assets. Essential records include:

• Flange identification with size, rating, and material.
• Installation dates and last inspection/maintenance.
• Leak, failure, and replacement history.
• Bolt torque values.
• Drawings indicating flange locations.

Sourcing Quality ANSI Flanges from China

Many global projects source ANSI flanges from leading China flange manufacturer due to their competitive pricing.

Some tips when procuring ANSI flanges from Chinese flange supplier include:

• Review test reports and quality control documentation.
• Inspect flange dimensions, face finish, and marking.
• Audit the factory for its manufacturing and quality capability.
• Examine packaging practices to prevent shipping damage.

By following robust quality assurance procedures and selecting reputed manufacturers, end users can source cost-effective, high-quality ANSI flanges from China.

Regular inspection, leak testing, and preventive maintenance enable ANSI flanges to deliver leak-free performance over decades. Proper record keeping and timely replacement of damaged flanges minimize operational risks. Sourcing ANSI flanges from qualified Chinese manufacturers can provide cost savings without compromising on quality.