What is the purpose of installing Pang Tong pipes before and after the outlet shut-off valve of a high-head pump?
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What is the purpose of installing Pang Tong pipes before and after the outlet shut-off valve of a high-head pump?
There should be a bypass for the outlet check valve! Generally, a bypass is provided for the outlet check valve of high-head pumps in order to prevent the check valve from failing to open due to excessive pressure difference when starting the pump, and the bypass is used to balance the pressure. If a bypass is installed before and after the outlet shut-off valve, it is usually a heat pump anti-freezing bypass (when there is a backup pump)
A bypass valve is provided on the pump outlet check valve, used to warm the pump before starting it up and to prevent backflow into the pump； A bypass valve is provided for the outlet shut-off valve, which is used to balance the pressure difference before and after the shut-off valve after the pump is started, thereby facilitating its smooth opening. If the process medium is prone to vaporization, the bypass valve adjacent to the pump should be slightly opened before starting the pump. Generally, after starting the pump, there is a period of time required to check the oil pressure, the motor, and the valves, etc.; leaving the bypass valve slightly open will prevent the medium from remaining in the pump for an extended period and thus vaporizing.
You are right regarding the heating pump lines of the pump; generally, high-head pumps are equipped with a minimum flow line (to prevent pressure buildup when the pump starts and to avoid vaporization of the fluid inside the pump), or an electric valve is installed at the pump outlet to ensure that the shut-off valve can open despite high pressures when the pump starts.