Reasons and solutions for valve leakage
If there is leakage beyond the rated range in the sealing area between the valve disc and the valve seat of the safety valve, it will cause the loss of the medium and subsequently damage the sealing material.
In general, the sealing surface of a safety valve is mainly composed of metal materials, and efforts are made to achieve smoothness and flatness. However, in the case of secondary compression of media under pressure, it is unlikely to demand complete sealing without leakage. So, under rated pressure environment, safety valves using steam as the medium can be detected solely by visual observation and auditory listening.
The main reasons for valve leakage are as follows:
(1) Dirt and debris appear on the sealing surface, and the originally sealed plane is blocked and separated, causing a gap between the valve core and valve seat Causing leakage of the valve. To solve this type of problem, it is usually necessary to clean the dirt and debris on the sealing surface. When the boiler is temporarily shut down for maintenance, a running weight test should be conducted on the safety door first. Once there is a leakage phenomenon, a comprehensive inspection should be carried out. The interval between running the ball is usually 20 minutes after complete cooling.
(2) The sealing surface is damaged. There are many reasons, such as: firstly, the materials used for sealing are not qualified. After years of use, a safety valve is prone to weakening the strength of its sealing surface due to continuous opening and closing, running in, and maintenance, which in turn weakens its sealing ability.
The suggested solution to this problem is to flatten the original sealing surface and perform secondary processing and welding according to the original drawings to enhance the surface hardness and strength. And pay attention to surface damage, be sure not to be careless. The second is the quality of maintenance. Due to the poor level of maintenance, the valve core and seat cannot reach a certain level in the grinding process. The solution is to use grinding or even turning methods depending on the severity of the damage to repair the sealing surface as much as possible. The third reason is improper assembly or incorrect part size. During the entire assembly process, if the valve core and valve seat are not completely aligned, or there is a serious light transmission problem on the joint surface, it is also possible that the sealing between the valve core and valve seat is too loose, making it difficult to truly seal. The solution is to strictly inspect the length, thickness, and distribution of the gaps next to the valve core, and ensure that the gaps in each part cannot lift the valve core. According to the data on the drawing, the width of the sealing surface should be appropriately reduced for sealing.
