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common-errors-and-hazards-in-valve-installation
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As the core component of a fluid control system, the quality of its installation directly affects the operating efficiency, safety and service life of the system.
During the actual installation process, various errors are prone to occur due to improper operation, insufficient technical knowledge or inadequate control of details, which may not only lead to leakage, increased energy consumption and other problems, but also cause equipment damage and safety accidents in serious cases.
We have sorted out the common errors in valve installation from multiple dimensions and analyzed their causes and hazards.
1. Errors in the pre-installation preparation stage
Pre-installation preparation is the basis for ensuring the normal operation of the valve. If omissions occur at this stage, subsequent problems are often difficult to remedy.
(1). Mismatch between valve selection and system
- Manifestations of errors:
- Failure to select valves of appropriate materials based on the characteristics of the medium (such as corrosiveness, temperature, and pressure), such as using ordinary cast iron valves for acidic medium pipelines.
- Mismatch between valve diameter and pipeline. Blindly pursuing large-diameter valves leads to reduced flow control accuracy, or small-diameter valves cause excessive pipeline resistance.
- Failure to select valve type according to system operating conditions, such as using gate valves (slow opening and closing speeds) instead of ball valves or butterfly valves on pipelines that need to be quickly cut off.
- Hazards: Valves are easily corroded by the medium and leak, or the mismatch of diameter and type leads to increased system energy consumption, control failure, and even pipeline burst.
(2). Inadequate valve inspection and cleaning
- Error manifestations:
- Failure to check whether the valve appearance (such as whether the valve body has cracks, whether the sealing surface is intact), model parameters (such as pressure rating, nominal diameter) are consistent with the design before installation.
- Failure to remove debris inside the valve (such as casting sand, rust, sealing material fragments), or failure to check the flexibility of the valve stem and valve core.
- Valves that need to be degreased and pickled (such as pipelines used in the oxygen and food industries) are not treated accordingly, and residual impurities contaminate the medium.
- Hazards: Impurities may get stuck in the valve core, causing the valve to fail to open and close normally; damage to the sealing surface will directly cause leakage; residual grease in the oxygen pipeline may cause an explosion.
2. Errors in connecting pipes and valves
The connection between valves and pipes is a key step in installation. Improper connection will directly affect the sealing and stability of the system.
(1). Common errors in flange connection
- Error manifestations:
- The flange sealing surface type does not match (such as mixing flat welding flanges with butt welding flanges), or there are scratches or deformations on the flange surface that have not been processed.
- Incorrect gasket selection: using gaskets that do not meet the characteristics of the medium (such as rubber gaskets for high-temperature pipes, which are prone to aging and failure); gasket size does not match the flange (too large to protrude inside the pipe, too small to result in insufficient sealing area).
- Irregular bolt installation: The bolt tightening sequence is chaotic (not tightened evenly diagonally), resulting in uneven force on the flange surface; inconsistent bolt tightness, too loose will result in poor sealing, too tight will result in deformation of the flange or bolts.
- Deviation between the center line of the flange and the pipe: The valve flange and the pipe flange are not concentric. Forced connection causes the valve body to bear additional stress, causing cracks or leakage.
- Hazards: Leakage at flange connections, loss of media causing waste or pollution; long-term uneven force can cause valve body cracking, especially in high-pressure systems, which may cause safety accidents.
(2). Common errors in threaded connections
- Error manifestations:
- Insufficient thread processing accuracy (such as incorrect tooth profile, dimensional deviation), or burrs and damage on the thread surface, resulting in loose connections.
- Improper use of sealing materials: Wrong winding direction of raw tape (opposite to the direction of thread tightening, resulting in seal failure when loosening); excessive application of sealant, which flows into the valve interior and contaminates the media or jams the valve core.
- Forced tightening: Misalignment of the thread during threaded connection, forced rotation, resulting in damage to the valve body thread or cracking of the valve body.
- Hazards: Leakage at threaded connections; damage to the valve body thread may make the valve unable to be disassembled, making maintenance difficult.
(3). Common errors in welded connections
- Error manifestations:
- Failure to clean the welding grooves of the valve and pipe before welding, resulting in impurities such as oil, rust, etc., resulting in pores and slag inclusions in the weld.
- Failure to take protective measures during welding: direct welding of cast iron valves (cast iron is prone to brittle cracking); failure to use argon arc welding as a primer for stainless steel valves, resulting in oxidation and corrosion of the welds.
- Welding temperature is too high or welding speed is too fast, resulting in deformation of the valve body and damage to the sealing surface.
- Hazards: Weld leakage; deformation of the valve body affects the normal operation of the valve core; oxidation of the stainless steel weld reduces corrosion resistance and shortens the life of the valve.
3. Errors in valve installation position and direction
The installation position and direction of the valve directly affect the convenience of operation, maintenance efficiency and the realization of system functions.
(1). Unreasonable installation position
- Error manifestations:
- The valve is installed in a narrow space or is blocked by other equipment, resulting in the operating handle and actuator not being able to operate normally and inconvenient for later maintenance.
- Safety valves, pressure reducing valves and other special valves are installed too high or too low, making it impossible to observe the pressure gauge or make adjustments.
- The valve is installed at a bend in the pipeline or near equipment with severe vibration. No fixing measures are taken, and long-term vibration causes the connection to loosen.
- Hazards: The valve is difficult to operate and cannot be opened and closed quickly in an emergency; vibration causes fatigue damage to the connection parts, causing leakage.
(2). Wrong valve installation direction
- Error manifestations:
- The installation direction of the one-way valve (such as the check valve) is reversed, resulting in medium backflow and abnormal system pressure (such as the reverse installation of the check valve at the pump outlet will cause the pump to run at no load and burn the motor).
- Valves with flow direction requirements such as stop valves and throttle valves are installed reversely, affecting the flow control effect and even causing sealing failure.
- Certain special structure valves (such as lift check valves) are not arranged according to horizontal or vertical installation requirements, resulting in functional failure.
- Hazards: The system function fails completely. For example, the reverse installation of the check valve will cause medium backflow and cause equipment damage; the reverse installation of the stop valve will cause the adjustment accuracy to decrease and the sealing surface to wear faster.
4. Errors in the installation of auxiliary devices
The normal operation of the valve depends on the correct installation of various auxiliary devices (such as actuators, pressure gauges, filters). Improper installation of auxiliary devices will indirectly affect the performance of the valve.
(1). Incorrect matching between actuator and valve
- Error manifestation:
- The torque or thrust of the electric or pneumatic actuator does not match the valve (too small will not drive the valve, too large will damage the valve).
- The connection between the actuator and the valve is not concentric, resulting in uneven force on the valve stem, causing jamming or breakage.
- Failure to install accessories such as limit switches and position transmitters as required, or incorrect wiring leading to control failure.
- Hazards: The valve cannot be remotely controlled or automatically adjusted; valve stem breakage causes the valve to lose control, causing a safety accident.
(2). Incorrect installation of the filter and pressure gauge
- Error manifestation:
- The filter is installed downstream of the valve, not upstream, causing impurities to enter the valve and damage the sealing surface.
- Improper selection of filter screen accuracy (too coarse to filter impurities, too fine to cause excessive pressure loss), or failure to clean the filter screen regularly, leading to blockage.
- The pressure gauge is improperly installed (e.g. far away from the valve or in a dead corner of the pipeline), which cannot accurately reflect the pressure before and after the valve; the pressure gauge valve or buffer device is not installed, resulting in damage to the pressure gauge.
- Hazards: The valve leaks due to wear caused by impurities; pressure monitoring is distorted, and the valve operating status cannot be judged, which may cause system failure due to overpressure.
5. Errors in post-installation commissioning and acceptance
The commissioning and acceptance after installation are the last step to ensure the normal operation of the valve. Omissions at this stage will lead to the failure of the previous work.
(1). Improper commissioning operation
- Error manifestations:
- Failure to perform pressure test or incorrect test method (e.g. only performing water pressure test and ignoring air pressure test, or the test pressure and pressure holding time do not meet the standards).
- Rapid opening and closing of the valve during commissioning, resulting in water hammer damage to the valve body or pipeline.
- Failure to check the sealing performance of the valve in the fully open, fully closed and intermediate positions, and only testing some working conditions.
- Hazards: Potential leakage points are not discovered, and medium loss occurs after operation; water hammer impact may cause the valve body to rupture, causing serious accidents.
(2). Incomplete acceptance records
- Error manifestation: Failure to record key information such as valve model, installation location, test data, or acceptance report without multi-party confirmation, resulting in the inability to trace valve parameters during subsequent maintenance.
- Hazard: Difficulty in quickly matching spare parts during maintenance, or secondary damage due to lack of understanding of installation details.
6. Targeted errors in the installation of special valves
Some special-function valves (such as safety valves, pressure reducing valves, and steam traps) have their own unique installation requirements. Violation of these requirements will lead to functional failure.
(1). Safety valve installation errors
- Error manifestation:
- The safety valve inlet pipe is too long or has elbows, resulting in excessive back pressure, affecting the accuracy of the starting pressure.
- The safety valve outlet pipe is not connected to a safe place (such as directly discharging to the room), or the outlet pipe has pressure (such as installing a valve), resulting in the safety valve being unable to discharge normally.
- The safety valve starting pressure is not adjusted according to the system pressure level, or it is not calibrated regularly.
- Hazards: When the system is over-pressured, the safety valve cannot be activated in time, which may cause equipment explosion; direct discharge of the medium may cause safety hazards or environmental pollution.
(2). Steam trap installation error
- Error manifestations:
- The steam trap is installed at a low position or in a dead water area of the steam pipe, which cannot effectively discharge condensate.
- Valves and filters are not installed before and after the steam trap, which is inconvenient for maintenance and cleaning.
- The steam trap type does not match the steam system operating conditions (such as using a low-pressure steam trap for a high-pressure steam system).
- Hazards: Condensate accumulation causes water hammer in the pipeline, damaging equipment; steam is wasted and the system thermal efficiency decreases.
Summary
Common errors in valve installation run through the entire process of preparation, connection, positioning, and commissioning. The root cause is often insufficient understanding of valve characteristics and system operating conditions, or improper operation.
These errors not only affect the normal function of the valve, but may also cause safety accidents such as leakage and explosion, resulting in economic losses and casualties. Therefore, before installation, the design plan must be rigorously reviewed to ensure the valve selection is compatible. During installation, specifications must be adhered to, with careful attention to detail (such as connection method, orientation, and installation of auxiliary devices). After installation, comprehensive commissioning and acceptance must be conducted, with complete records maintained.
Only meticulous operation throughout the entire process can ensure the safe and efficient operation of the valve and the entire fluid system.