Precautions in Vacuum Valve Operation
Avoid valve staggering, wrong closing, missing opening and missing closing. The operator shall clearly understand the function of each valve and its position in the process pipeline to avoid misoperation, or it may cause material running, mixing, pressure holding and other accidents. For example, steam purging is carried out before the start of a refinery equipment, and a vent valve is leaked after purging. As a result, 370 ℃ high-temperature oil slurry is discharged from the vent valve during the start of the project, causing a fire, and the equipment is shut down.
When the temperature is below 0 ℃, the valve that is out of service shall be antifreezed first, and the plug at the bottom of the valve shall be opened in time to discharge the condensed water inside. The valves that cannot be cleaned and operated continuously shall be kept warm.
For valves operating at high temperature, when the temperature rises above 200 ℃, the bolts are heated and extended, which is easy to make the valve seal not tight. When necessary, the bolts shall be “hot tight”. When hot tight, it is not suitable to conduct in the fully closed position of the valve. In order to prevent the valve stem from being jacked and difficult to open again.
When the valve leaks, the leakage position and reason shall be identified first. Generally, the leakage is divided into two types: leakage at the packing, leakage at the valve cover, valve body and leakage at the sealing surface or fabric according to the external structure. The operator shall accurately judge the leakage, and handle the problems that can be solved by himself in time, and the problems that can not be solved by him in time.
The packing gland of the valve should not be pressed too tightly. It is better that the valve rod can rotate sensitively. If it is pressed too tightly, the friction of the valve rod will be increased and the operating torque will be increased. During valve operation, it is generally not allowed to replace or add packing with pressure at will, otherwise, leakage of medium may cause risks.
