Application of fasteners in valves

Fasteners play a key role in valves, and their application involves structural connection, sealing, adjustment and stability. The following are specific application scenarios and related precautions:

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1. Connection between valve body and valve cover

• Fasteners type: bolts, nuts, washers (such as flat washers, spring washers).

• Function: Tightly fix the valve body and valve cover to ensure that the internal medium does not leak.

• Precautions:

1. High-strength alloy steel or stainless steel should be selected to withstand pressure and temperature changes.

2. Gaskets should be corrosion-resistant and bolts should be pre-tightened evenly to prevent deformation.

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2. Fixation of valve stem and valve disc

• Fasteners type: hexagon socket screws, pins, snap rings.

• Function: Fix the valve disc and valve stem to ensure accurate transmission of switching action.

• Precautions:

1. Rust-proof treatment (such as galvanizing, chemical nickel plating) is required to avoid jamming due to corrosion.

2. The pins need to be checked for wear regularly to prevent malfunctions caused by falling off.

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3. Flange and pipeline connection

• Fastener types: flange bolts, nuts (such as studs), flange gaskets.

• Function: connect the valve to the pipeline flange to ensure the sealing of the system.

• Notes:

1. Select the number and torque of bolts according to the standard (such as ASME B16.5) to avoid overload.

2. Heat-resistant gaskets are required for high temperature conditions to prevent leakage due to thermal expansion and contraction.

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4. Tightening of sealing structure

• Fastener types: gland bolts, packing pressure plates.

• Function: Tighten the sealing packing (such as graphite, PTFE) in the stuffing box to prevent the leakage of the medium.

• Notes:

1. The bolt preload must be uniform. Too tight may damage the packing, and too loose may leak.

2. Dynamic seals need to be adjusted regularly to compensate for packing wear.

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5. Bracket and fixed base

• Fastener types: anchor bolts, expansion bolts.

• Function: Fix the bracket of large valves (such as gate valves and ball valves) to resist vibration or external force.

• Notes:

1. The foundation needs to be stable, and the bolt specifications need to match the valve weight and working load.

2. Anti-loosening nuts or thread glue can be added in a vibrating environment.

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6. Assembly of operating mechanism

• Fastener types: small screws, locating pins, locking nuts.

• Function: fix operating parts such as handwheels, gearboxes, actuators, etc.

• Notes:

1. Anti-loosening design (such as spring washers, nylon locking nuts) is required to prevent loosening during operation.

2. The locating pins need to be precisely matched to ensure the neutrality of the transmission parts.

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7. Special working conditions

• High temperature/high pressure: use heat-resistant alloy bolts (such as Inconel) and high-strength studs.

• Corrosive media: use Hastelloy, titanium, or surface plating.

• Vibration environment: use anti-loosening washers and double nuts for locking.

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8. Maintenance and disassembly design

• Standardized design: use universal bolt specifications (such as ISO, DIN) for easy replacement.

• Removability: Avoid excessive rust (such as applying anti-seizure agent) and facilitate maintenance.

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Summary

Fasteners in valves are not just simple connectors. Their selection, installation and maintenance directly affect the sealing, life and safety of the valve. When designing, it is necessary to comprehensively consider the working conditions (pressure, temperature, medium), material compatibility and anti-loosening requirements, while taking into account the convenience of maintenance. For example, nuclear power valves may require redundant fastening design, while the food industry needs to avoid metal contamination and select non-standard materials.