Installing flange accessories is a common operation in pipeline systems and mechanical equipment connections, and it is necessary to ensure sealing, stability, and safety. The following are detailed installation steps and precautions:
1. Preparations before installation
1) Inspect accessories
Confirm that the specifications of the flange, gasket, bolts, and nuts are compatible (such as pressure rating, material, and size).
Check if the sealing surface of the flange is flat, without scratches or burrs, and if the bolt holes are aligned.
The gasket material should be compatible with the medium (such as rubber, metal, PTFE, etc.), avoiding corrosion or aging.
2) Clean surfaces
Use a wire brush or sandpaper to remove rust, oil, or impurities from the flange sealing surface and bolt holes.
Wipe with a clean cloth to ensure no particles remain, preventing poor sealing.
3) Prepare tools
Wrench (adjustable wrench or torque wrench), level, lubricant (such as anti-bite agent), marker pen.
2. Installation steps
1. Positioning and alignment
Align the flange with the pipe or equipment port, ensuring the center lines are consistent.
Use a level to check if the flange is level (for vertical pipes, check the verticality), avoiding stress concentration that leads to leakage.
2. Installing gaskets
Place the gasket evenly on the flange sealing surface, ensuring it completely covers the sealing area without offset or folds.
Note: Metal gaskets need to align with the recess or flange on the flange sealing surface.
3. Assembling bolts and nuts
Insert the bolts through the flange holes and insert the nuts diagonally (to avoid single-direction tightening that causes the flange to deform).
Manually tighten all nuts initially, maintaining uniform flange clearance.
4. Crossed symmetrical tightening
Stage-by-stage tightening:
First round: Use a wrench to cross and symmetricalally tighten all nuts, with uniform force (about 50% rated torque).
Second round: Gradually increase torque in a diagonal sequence to 70%-80%.
Final round: Use a torque wrench to tighten according to the standard torque value (refer to the flange specification table) to ensure all bolts are under consistent force.
Avoid over-tightening: Prevent bolt breakage or flange deformation.
5. Inspection and testing
1) Visual inspection: Confirm that the gasket is not extruded, and the flange is not tilted.
2) Leakage test:
Low-pressure system: Apply soap water to the sealing surface and observe if it bubbles.
High-pressure system: Conduct a pressure test (usually 1.5 times the working pressure), hold pressure for 30 minutes without leakage.
3) Re-tightening: If leakage is found, depressurize and adjust the bolt torque.
3. Special scenarios handling
1) High/High-pressure systems
Use metal wound gaskets or octagonal gaskets, and apply high-temperature sealing glue.
The bolts need to be preheated before installation (to avoid cold contraction that causes loosening).
2) Corrosive media
Choose corrosion-resistant materials (such as Hastelloy, PTFE gaskets).
Apply anti-corrosion coating after installation to protect the bolts.
3) Vibration environment
Install spring washers or anti-loosening nuts to prevent bolt loosening.
Regularly inspect and retighten bolts.
4. Safety precautions
1) Wear protective equipment: gloves, goggles to prevent metal debris from scratching.
2) Pressure relief operation: Ensure the system is pressure-free before installation to avoid medium splashing.
3) Avoid mixing bolts: Do not mix bolts of different materials or strengths to prevent uneven stress.
4) Record torque values: High-pressure systems need to record the final torque for later maintenance.
5. Common problem solutions
Leakage: Check if the gasket is damaged, if the bolts are loose, or if the flange surface has defects.
Bolt fracture: Replace with high-strength bolts and recalculate the torque value.
Flange deformation: Correct the flange or replace the new part and reinstall.
By following standard operations and strict inspections, the long-term reliability and safety of flange connections can be ensured. If unfamiliar with the operation, it is recommended to consult a professional engineer or refer to the equipment manual.
