Discussion on overpressure at the standby pump inlet
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As stated below, the standards require that, when a pump is used with another pump to prevent hazards caused by backflow, the inlet pressure rating of the pump should be the same as that of the outlet. May I ask: What is the opening status of the inlet and outlet valves of the standby pump under normal conditions? When will backflow cause overpressure at the inlet of the standby pump? Because standards specify the use of dual check valves to prevent backflow in operating pumps, with these dual check valves in place, when could it lead to overpressure in the standby pump? Specification: If a pump of the same model has a backup unit, the following measures should be considered at the pump inlet to prevent hazards caused by backflow. When the pump outlet pressure P is: a) P ≤ 4.0 MPa: the grade of the inlet valve shall be the same as that of the outlet valve ； b) P > 4.0 MPa: A cost-effective solution can be chosen based on investment considerations and the condition of the mechanical seal, such as using the same valve grade for the inlet as for the outlet, or adding a safety valve without raising the valve grade.
Describe what’s shown in the picture: what kind of standard is this, and what does its device look like? Are you referring to the lubricant station? Pressurization station? ? ?
1. When the standby pump of a centrifugal pump is in standby mode, the inlet valve should be fully open and the outlet valve should be in the middle position. 2. In practical operations, this situation arises: for example, with pumps 1#, 2#, and 3# operating in series, when a command is given to stop pump 2#, that pump does stop. However, due to a fault, the outlet valve of pump 2# cannot be closed, which results in high-pressure oil flowing back toward the pump’s inlet
Sinopec’s internal design specifications, applicable to the design of petrochemical plants
It still depends on the visuals; with a simple process, one can understand what’s going on. It’s hard to say without anything. Processes like this can be fully automated with current control methods. It won’t cause any overpressure.
The inlet valve of the standby pump is fully open, and the outlet valve is closed.