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 How to Install Rubber Flexible Joints (Rubber Expansion Joints)

By SYNTHETIC RUBBER PRODUCTS – The Largest Rubber Flexible Joint Supplier in Malaysia

Proper installation of rubber flexible joints (also known as rubber expansion joints or rubber bellows) is critical to ensure maximum performance, durability, and safety of your piping system.
Incorrect installation can cause premature failure, leakage, or overextension. Follow the guidelines below carefully.

 1. Pre-Installation Preparation

Before installing the rubber flexible joint:

•  Inspect the joint carefully – Check for cracks, deformities, or surface damage.
•  Verify material compatibility – Ensure the rubber type (EPDM, NBR, Neoprene, etc.) is suitable for the media (water, oil, acid, slurry, etc.).
•  Check pressure and temperature ratings – Confirm that the joint is rated for your system’s design conditions (e.g., PN10, PN16, etc.).
•  Align the pipeline – Misalignment should not be corrected by stretching or compressing the joint. The flexible joint should only absorb system movement during operation, not installation errors.
•  Clean all mating surfaces – Remove rust, scale, or debris from flanges before fitting.

 2. Installation Procedure (Flange End Type)

Step 1: Positioning the Joint

• Place the rubber flexible joint between the mating flanges of the pipeline.
• Ensure the joint is in a neutral position — not compressed, extended, or twisted.
• The flow direction (if marked on the joint) should match the pipeline direction.

Step 2: Inserting Bolts

• Insert bolts from the arch side of the joint to prevent thread damage.
• Ensure washers are placed under each nut and bolt head for even pressure.
• Use galvanized or stainless steel bolts for corrosion resistance.

Step 3: Tightening Bolts

• Tighten bolts gradually and evenly in a crisscross (star) pattern.
• Do not overtighten — excessive compression can damage the sealing flange.
• Torque should be applied progressively until all flanges are uniformly seated.
• After initial pressurization, recheck bolt tightness to ensure sealing integrity.

Step 4: Control Units (if applicable)

• If control rods (tie rods or limit bolts) are supplied, install them after flange tightening.
• Adjust rods with slight clearance to allow designed movement (axial/lateral).
• These prevent overextension under pressure surges or vacuum conditions.

 3. Installation Distance and Alignment

• Maintain straight alignment between connected pipes.
• Do not use rubber joints to correct major misalignments or elevation changes.
• For multiple joints in series, allow sufficient spacing between joints (typically at least one pipe diameter apart).
• Ensure that the joint is not exposed to excessive bending or twisting forces.

 4. Operating Conditions

• Keep the joint within its rated temperature and pressure limits at all times.
• Avoid vacuum conditions unless the joint is designed for it (vacuum-resistant type).
• Ensure fluid compatibility with the rubber compound (EPDM, NBR, CR, NR, Viton, etc.).
• If installed outdoors, consider UV protection or shielding to prolong rubber lifespan.

 5. Support & Anchoring

• The piping system should be properly anchored and guided to prevent excessive stress on the rubber joint.
• Do not use the joint to absorb full pipeline movement — guides and anchors must share the load.
• Install anchors near elbows, tees, and pumps to minimize thrust transfer.
• Use tie rods or control units when:
  • There are unanchored pipelines
  • Vacuum or high-pressure surges are expected
  • Thermal expansion may exceed allowable movement range

 6. Common Installation Mistakes to Avoid

 Do not twist the joint during installation.
 Do not exceed the allowable movement (axial, lateral, angular).
 Do not weld near the installed joint – high heat may damage rubber.
 Do not paint or coat the joint with chemicals that may attack rubber.
 Do not use as a load-bearing element or pipe support.
 Do not overtighten flange bolts – it can crush the sealing flange.

 7. Post-Installation Inspection

After installation:

• Pressurize the system gradually and check for leaks.
• Inspect joint alignment, flange sealing, and movement allowance.
• Verify tie rod spacing and clearance.
• After 24 hours of operation, recheck bolt torque and alignment.

 8. Maintenance Recommendations

• Inspect visually every 6 months for cracks, bulges, or leaks.
• Retighten bolts if joint relaxation is observed.
• Replace joint immediately if swelling, cracking, or delamination appears.
• Store spare joints in a cool, dry, and dark environment away from ozone sources.

 Tools Required for Installation

• Torque wrench
• Flange alignment tools
• Soft cloth or brush (for cleaning flanges)
• Lubricant (for bolts only; never apply to sealing surface)
• Control rod kit (optional)

 SYNTHETIC RUBBER PRODUCTS – Malaysia’s Trusted Expert

SYNTHETIC RUBBER PRODUCTS is The Largest Rubber Flexible Joint Supplier in Malaysia and The Highest Quality Union Flexible Joint Manufacturer, providing:

• Single Bellow Double Bellow Union Flexible Joints
• Flange End Threaded End Victaulic End Types
• Custom Material Options: EPDM, NBR, Neoprene, Natural Rubber, Viton
• Supply & technical support throughout Johor, Melaka, Negeri Sembilan, Selangor, Kuala Lumpur, Perak, Penang, Kedah, Perlis, Kelantan, Terengganu, Pahang, Sabah, Sarawak, and Labuan.