What are the Reasons for Internal Valve Leakage?

The thermal loss caused by the internal leakage of the valve within the thermal system is an important factor leading to the increase of the boiler heat loss. Coal-fired power plants should formulate measures to prevent valve leakage and treat valve leakage as a key task.

Effects of Valve Leakage

1. Safety problem

Safety is the core of coal-fired power plants. Without safety, the continuity and efficiency of operation are no longer guaranteed. The internal leakage of the valve makes it impossible to isolate and eliminate the running equipment, which threatens the safety of the maintenance staff even causes serious consequences.

2. Influencing economic benefits

Valve internal leakage will cause the decrease of negative load rate and operating efficiency. For example, the internal leakage of the drain valve of the feed water pump will seriously affect the capacity of the unit to carry the load. In addition, the increase of the number of leaking valves will increase the cost of valve repairing, grinding and replacement.

3. Pollution

While pursuing economic benefits, enterprises also shoulder certain social responsibilities. The internal leakage of the valves of desulfurization, ash removal, coal transportation, and chemical systems may cause leakage of acids, alkalis, slurries, waste water and exhaust gas, which will cause damage to the surrounding environment.

Causes of Valve Leakage

1. Internal leakage caused by unqualified water quality

When the unit starts, especially during debugging, it is required to flush the drain valve of the fully open system. Because the system is out of service for a long time, there is a lot of rust and salt in the pipeline. If the rinsing is not thorough, impurities such as rust will be accumulated between the stainless steel valve core and the valve seat. These impurities stuck to the bottom of the valve core will cause the valve unable to close improperly and cause internal leakage.

2. Internal leakage caused by improper operation

If the unit shuts down too late or opens prematurely, the high temperature and high pressure steam will have a serious erosion to the valve. When Shut-off valves are in a half-open and half-closed state, the valve blow-outs will cause valve leakage. It was not confirmed that it was closed properly or the valve was not opened and closed in accordance with the prescribed operating sequence, all have risks to lead to internal leakage.

3. Controlling Effects

The traditional control methods of electric valves are mechanical control methods such as valve limit switches and over-torque switches. These control elements are affected by ambient temperature, pressure, and humidity, may lead to the incorrect of the valve positioning. As well as objective factors like spring fatigue and uneven thermal expansion coefficients, may cause internal leakage of electric valves.

4. Internal leakage caused by valve failure

Valve manufacturers do not strictly control the valve material, processing technology, and assembly technology during the production process, and before the on-site installation, the quality inspection professionals has not strictly checked, causing unqualified products to enter the production site.