Ball valve lock failure main causes and judgment methods

Step 1: It is necessary to first open the transmission gearbox to determine whether the valve cannot operate normally due to serious rust, bearing damage or foreign body blockage in the transmission gearbox. If this is not the case, proceed to the following steps.

Step 2: Perform blowdown operations on the ball valve. If there is pressure in the valve chamber, it can be preliminarily judged that the cause of locking is the blocking of the seal seat. Normally, the sealing seat should have 0.003 inches of lateral movement space. If the injected sealing grease is hardened, dirt impurities are stuck in the gap of the seat, or the seal seat spring is not working properly, the seal seat can be blocked and the ball valve is locked.

Step 3: Blow off the ball valve. If there is no air pressure in the chamber, it is judged that the pressure difference between the valve chamber and the main line is too large. When the pressure difference between the valve chamber and the main line is too large, the sealing seat is pressed to the spherical surface, the operating torque is too large, and the ball valve can not operate normally.

Ball valve lock fault removal

According to the sealing principle of ball valve, fault cause analysis and successful field troubleshooting experience of ball valve lock fault, the troubleshooting methods of lock fault are summarized as follows:

(1) Transmission gearbox failure: As a preventive maintenance, it is necessary to open the gearbox regularly every year, check the lubrication, anti-rust and intact parts of the transmission mechanism in the box, clean the sewage and foreign matter in the box, and replace the fresh butter. If the bearing and other parts are damaged, it is necessary to replace it in time to ensure that the transmission mechanism is in good working condition and the valve is operated smoothly.

(2) Seal block failure: first inject the cleaning solution to soak (soaking time can be determined according to the valve grease), and then discharge the dirt impurities by sewage to eliminate the seal block; If the valve still cannot operate normally after repeated cleaning and blowdown, it can be judged that the seal seat spring and other parts are abnormal, and the valve must be disassembled for maintenance.

(3) The pressure difference between the valve chamber and the main line is too large: generally, the cleaning solution is injected first after soaking, and the original sealing grease is cleaned off the sealing surface. If the valve itself has a certain amount of internal leakage, the pressure balance between the valve chamber and the main line can be achieved; If the fault still exists, consider making a blowdown nozzle gas injection device connected to the ball valve blowdown nozzle to balance the pressure difference between the valve cavity and the main line as shown in Figure 3.1 to eliminate the locking fault. This flat pressing device is simple in structure and easy to make, and the effect is obvious. Using this device, we have successfully solved many other valve locking failures such as 12 "ball valve in a factory of Dagang Station. As shown in Figure 3.1, one end of the machine connector is a quick-install connector, and the other end is a screw buckle matching the drain nozzle interface specifications. It is recommended that engineers prepare a set of machine connector according to the common valve drain nozzle interface specifications.

The danger of barbaric operation

Brutal operation of valves that do not operate properly can result in:

(1) The force of the valve transmission gearbox is too large, causing the box to break or the gearbox and other components in the box to deform and damage;

(2) Serious scratches on the sealing sphere, leading to serious internal leakage of the valve, or even scrap;

(3) The extension rod is broken or multiple people operate at the same time, resulting in personal injury to the operator.

In order to avoid equipment damage, personnel injury and economic losses, the ball valve can not operate normally, do not take the use of afterforce rod or multi-person operation and other barbaric way of operation! Carefully analyze the cause of the fault and properly handle and eliminate the fault.