Pipeline valve installation

1. Valve installation position must be convenient for operation

Even if installation is temporarily difficult, long-term operator convenience must still be considered. The valve handwheel should ideally be positioned at chest height (generally about 1.2 meters above the operating platform) so that opening and closing operations require less effort.

The handwheel of floor-installed valves should face upward and should not be tilted to avoid inconvenient operation. Valves installed close to walls must also leave sufficient space for operators to stand and work safely.

Avoid overhead operation whenever possible, especially when handling hazardous media such as acids, alkalis, or toxic fluids, as this can be dangerous.

Do not install gate valves upside down (with the handwheel facing downward). Otherwise, the medium may remain inside the bonnet for a long time, leading to valve stem corrosion and difficulty in replacing the packing.

Open-stem gate valves should not be installed underground because moisture may corrode the exposed valve stem.

For lift check valves, the valve disc must remain vertical during installation to ensure smooth movement. For swing check valves, ensure that the hinge pin remains level so the disc can swing freely.

Pressure relief valves should be installed vertically on horizontal pipelines and must not be tilted.

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2. Construction precautions

Care must be taken during installation and construction. Avoid striking valves made from brittle materials such as cast iron.

Before installation

1. Carefully check the model and specifications of all valves to ensure they meet design requirements.

According to the valve type and manufacturer’s instructions, verify whether the valve is suitable for the intended working conditions. Perform hydrostatic or pneumatic testing if required.

2. Inspect the valve packing, gland bolts, valve stem, and valve disc.

Ensure:

• Packing is intact
• Gland bolts have sufficient adjustment allowance
• Valve stem and disc move freely
• No jamming or misalignment exists

For threaded valves, inspect thread quality carefully. Unqualified valves must not be installed and should be clearly marked or separated.

3. Remove all debris inside the valve before installation.

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Installation process

1. Valve lifting

When lifting the valve, do not attach lifting ropes to the handwheel or valve stem, as this may damage these components. Lifting ropes should instead be attached to the valve flange or valve body.

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2. Pipeline cleaning before valve installation

Pipelines connected to the valve must be thoroughly cleaned.

Compressed air may be used to remove:

• Rust particles
• Sand and dirt
• Welding slag
• Other debris

Such debris can scratch sealing surfaces or block small valves, causing malfunction.

For threaded valves, sealing materials such as PTFE tape or thread sealant should only be wrapped around the pipe threads and not inside the valve to avoid contamination and flow obstruction.

When installing flanged valves:

• Tighten bolts evenly and symmetrically
• Ensure pipe flanges and valve flanges are parallel
• Maintain proper alignment clearance

Improper alignment may cause excessive stress or cracking, especially for brittle valves or valves with low mechanical strength.

For welded valves, tack welding should be completed first. The valve should then be fully opened before final welding.

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3. Protection measures

Some valves require external protection such as:

• Thermal insulation
• Cold insulation
• Heat tracing

The required protection depends on process conditions.

If the medium temperature inside the valve drops excessively, production efficiency may decrease or the valve may freeze. In such cases, insulation or heating is necessary.

If excessive external temperature causes condensation or frost, cold insulation may be required.

Common insulation materials

• Asbestos
• Mineral wool
• Glass wool
• Perlite
• Vermiculite

Common cold insulation materials

• Cork
• Foam
• Plastic
• Perlite

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4. Bypass piping and instrumentation

Some valves require bypass lines and instrumentation in addition to protection systems.

Bypass piping allows:

• Easier maintenance
• Temporary operation during repairs
• Steam trap maintenance

The decision to install bypass piping depends on:

• Valve importance
• Operating conditions
• Process requirements

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5. Packing replacement

Some stored valves may contain packing materials unsuitable for actual operating media and therefore require replacement.

Valve manufacturers typically use standard packing materials, but in practice, the packing must match the actual working medium.

Packing installation requirements

• Install packing ring by ring
• Joint angles should preferably be staggered
• Typical stagger angle:
  • 45°
  • 120°
  • 180° depending on valve requirements

The packing chamber should not be completely filled. Space must remain for future gland tightening.

Common packing materials

• PTFE packing
• Graphite packing
• Rubber O-rings
• Nylon packing rings
• Fluororubber seals

When tightening the gland:

• Apply force evenly
• Avoid over-tightening
• Rotate the valve stem simultaneously to ensure even compression

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Valve pressure testing

Low-pressure, medium-pressure, and high-pressure valves must undergo:

• Strength testing
• Tightness testing

Alloy steel valves may additionally require material verification and spectral analysis.

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1. Valve strength test

The strength test is performed with the valve partially open to inspect external leakage.

For valves with PN ≤ 32 MPa:

• Test pressure = 1.5 × nominal pressure
• Test duration ≥ 5 minutes

No leakage is permitted at:

• Valve body
• Bonnet
• Packing gland

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2. Valve tightness test

The tightness test is performed with the valve fully closed to verify sealing performance.

Except for:

• Butterfly valves
• Check valves
• Foot valves
• Throttle valves

Testing is generally conducted at nominal pressure or 1.25 times the working pressure.

No leakage at the sealing surface is permitted.

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General rules for valve installation

• Valve installation must not obstruct operation, maintenance, or disassembly.
• Installation layout should remain neat and accessible.
• On horizontal pipelines, valve stems should preferably point upward.
• Do not install handwheels facing downward.
• Valves installed at high elevations may require chain wheel operation.
• Adjacent valves should maintain adequate spacing between handwheels.
• Large or heavy valves should be supported with brackets.
• Frequently operated valves above 1.8 meters should have operating platforms.

Flow direction arrows on valve bodies must match the actual pipeline flow direction.

For flanged valves:

• Ensure flanges are parallel and concentric
• Avoid using double gaskets

For threaded valves:

• Install unions near the valve to simplify maintenance and removal.

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