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Safety Valve problem and solutions

【 Common Faults of Safety Valves and Solutions】
Improper selection or operation may result in faults to safety valves. If such faults are not corrected in time, they can have impact on the effect and life of valves, and even cause them unable to perform the function of safeguard. The table below shows the common faults and solutions.
Faults
Causes
Solutions

Leakage
1. Dirt Occurred on sealing surface
Use lift wrench or other method to make valve opened several times to wash away the dirt. If the dirt cannot be removed, take apart the valve to clean it away, and then have the valve reassembled for commissioning.


2. Sealing surface damaged
Take apart the valve and have the damage repaired by grinding or grinding after  turning responding to the extent of damage. After repair, sealing face shall be assured of sound plainness With its roughness Ra value not lower than 0.1.


3. Improper installation or the additional load of pipeline
Re-install or remove the additional load of pipeline.


4. High temperature or corrosive media
Have spring or even valve replaced according to the actual working conditions. If it is merely for the reason of improper adjustment of spring, it can be regulated by fastening or loosening the adjusting bolt.


5. The opening pressure of safety valve is too close to the working pressure equipment
Reset the pressure with the permissible range of spring pressure. On the condition that strength can be met, the set pressure of safety valve shall be suitably enhanced.

Inflexible opening and closing
1. Improper position adjustment of adjusting ring
Improper position of adjusting ring has made the opening process of safety valve lengthened or re-seating slow. Re-adjust it to meet the requirements of production process

 

2. The moving parts inside jammed
It may be possibly for the reasons of improper assembly, insufficient machining precision, valve body invaded by impurities, or spare parts getting corroded. Take out solutions according to different occasions.


3. Excessive resistance of discharge pipe, high discharge back pressure, or insufficient lift of safety valve
Reduce the bending of discharge pipe and try to use straight pipe of diameter greater than outlet diameter.

Deviation of opening pressure value
1.Caused by working temperature
1.Pressure regulation under cold state for safety valves used under thermal state, loosen the nut of adjusting bolt and suitably fasten the adjusting bolt.
2.In case of improper model selection, such as safety valve for boilers in power station, the type carrying radiator may be used.


2. Caused by spring corrosion
Replace the spring. Under the conditions where media have the property of corrosion, spring used shall be wrapped by fluorine plastic on surface or safety valves with bellows isolation mechanism shall be used.


3. Caused by Variation of back pressure
In case that back pressure varies greatly, bellows safety valves with balanced back pressure shall be used.


4. Moving parts inside jammed
Check and remove

Chatter or flutter
1. Excessive discharge capacity of safety valve ( relative to the required discharge capacity)
Use safety valves of rated discharge as far as possible close to the required discharge of equipment


2. The diameter of inlet pipe being too small or having too much resistance
Make the inner diameter of inlet pipe not lower than the inlet diameter of safety valve or reduce the resistance of inlet pipe.


3. Excessive resistance of discharge pipe ( excessive discharge back pressure)
Lower the resistance of discharge pipe.


4. Improper adjustment of adjusting ring
Re-adjust the position of adjusting ring and reduce the excessive re-seating pressure


Excessive rigidity of spring
Use spring of lower rigidity.

 


【 Common Faults of Safety Valves and Solutions】
Note: the specifications on the deviation of set pressure in GB/T 12243 Spring Laded Safety Valves:
① Deviation of the set pressure of safety valves used for pressure vessels and pipelines: ±0.014MPa in case of set pressure lower than 0.5MPa, and ±3% of the set pressure in case of set pressure greater than or equal to 0.5MPa.
 ② Deviation of the set pressure of safety valves used for steam boilers:
±0.014MPa in case of set pressure lower than 0.5MPa,
±3% of the set pressure in case of set pressure between 0.5-2.3MPa,
±0.07MPa in case of set pressure greater between 2.3-7.0 MPa,
±1% of set pressure value in case of set pressure greater than 7.0 MPa.

【 Maintenance of Safety Valves 】
To ensure reliable action and longer service life of safety valve, the following points shall be conformed in the operation
① Regularly check the safety valves in operation to see if there is any abnormal phenomena, like leaking, jamming, spring rusting, etc, and notice whether the adjusting bolt and lock nut of adjusting ring set screw have been loosened or not.  If problems arise, timely solutions shall be carried out.
② Safety valve shall be taken off regularly for complete cleaning. It can be reused only after checking, regrinding and pressure setting.
③ Safety valves installed outdoors shall be provided with suitable protective measures to prevent safety valves and discharge pipeline from invasion by rain, fog, dust, rust, etc. In case that the ambient temperature is lower than 0 ℃, necessary anti-freezing measures shall be carried out to ensure the operating reliability of safety valves.

Hits:  UpdateTime:2017-03-09 14:46:17  【Printing】  【Close
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