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2021

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01

Anti-clogging (stuck) methods for regulating valves that are often stuck or clogged

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Welding slag, rust, slag, etc. in the pipeline cause blockage or jamming in the orifice, guide part, and balance hole of the lower valve cover, causing strains and scratches on the curved surface of the valve core and guide surface, and indentations on the sealing surface. wait. This often occurs in newly put into operation systems and in the early stages of operation after overhaul. This is the most common failure.

 

cleaning method

 

Welding slag, rust, slag, etc. in the pipeline cause blockage or jamming in the orifice, guide part, and balance hole of the lower valve cover, causing strains and scratches on the curved surface of the valve core and guide surface, and indentations on the sealing surface. wait. This often occurs in newly put into operation systems and in the early stages of operation after overhaul. This is the most common failure.

In this case, it must be disassembled and cleaned to remove slag. If the sealing surface is damaged, it should be ground; at the same time, open the bottom plug to flush away the slag that fell into the lower valve cover from the balance hole and inspect the pipeline. Rinse. Before putting into operation, let the regulating valve fully open, and let the medium flow for a period of time before bringing it into normal operation.

 

External flushing method

 

When ordinary valves are used to regulate some media that are prone to sedimentation and contain solid particles, the orifice and guide are often blocked. The flushing gas and steam can be externally connected to the bottom plug of the lower valve cover.

When the valve is clogged or stuck, open the external gas or steam valve to complete the flushing work without moving the regulating valve, allowing the valve to operate normally.

 

How to install pipe filters

 

For small-diameter control valves, especially ultra-small flow control valves, the throttling gap is extremely small, and there should be no trace of slag in the medium.

In case of blockage in this case, it is best to install a filter on the pipe in front of the valve to ensure the smooth passage of the medium.

For regulating valves with a positioner, the positioner does not work properly and the air path orifice is clogged. This is the most common fault.

Therefore, when working with a positioner, the air source must be properly handled. The usual method is to install an air filter pressure reducing valve on the air source pipeline in front of the positioner.

 

Increasing the throttling gap method

 

For example, solid particles in the medium or welding slag and rust that have been washed away in the pipeline cannot pass through the throttling opening, causing problems such as blockage and jamming. You can use a throttling piece with a large throttling gap - the throttling area is open. Because the throttling area of ​​valve cores and sleeves such as windows and openings is concentrated rather than circumferentially distributed, faults can be easily eliminated.

If it is a single or double-seat valve, the plunger-shaped valve core can be changed to a "V"-shaped port valve core, or it can be changed to a sleeve valve, etc.

For example, in a chemical plant, a double-seat valve often got stuck. After it was recommended to use a sleeve valve, the problem was immediately solved.

 

media flushing

 

The medium's own scouring energy is used to scouring and taking away things that are easy to precipitate and block, thereby improving the anti-blocking function of the valve.

Common methods are:

Change to closed flow type use;

Adopt streamlined valve body;

Place the throttle at the most severe erosion point. When using this method, attention should be paid to improving the erosion resistance of the throttle material.

 

Straight through to angle method

 

The straight-through flow is inverted S flow, with complex flow paths and many dead zones in the upper and lower chambers, providing a place for the medium to settle. With angular connection, the medium seems to flow through a 90°C elbow, with good flushing performance, small dead zone, and easy design into a streamlined shape. Therefore, when a straight-through regulating valve is slightly clogged, it can be changed to an angle valve.