What is the function of the pump’s heat pump pipeline, and how does it work?

The protection line for pumps serves several functions. For warm pump lines, a bypass line is generally installed in front of and behind the check valve at the outlet of the standby pump; if the outlet valve is closed, the bypass line should be installed behind the outlet valve and in front of the check valve. The flow rate of the warm pump line is not high, and the control system is designed to prevent the standby pump from rotating in the reverse direction. We use pipelines with a diameter of DN15 or DN20 for this purpose. 1) Warm pump line – When transporting high-temperature oils with a temperature above 200°C, and when there is a standby pump, a warm pump line with a diameter of DN20–DN25 should be installed； (2) Low-flow line – When the pump’s operating flow rate is 30% below its rated flow rate, a low-flow line should be provided to allow the pump to operate normally at that lower flow rate ； (3) Balance line – For liquids with a saturated vapor pressure at room temperature that is higher than atmospheric pressure, or liquids in the bubble point state, a balance line must be installed to prevent vapor from forming in the liquid entering the pump or bubbles from entering the pump and causing cavitation ； (4) Bypass line – used for the trial operation of the pump, or to keep the pump running when the main outlet valve is closed under abnormal operating conditions. Bypass valves equipped with flow-limiting orifices are generally installed in situations where the pressure difference before and after the valve is very high ； (5) Anti-condensation system – When transporting liquids with a high pour point or high freezing point that solidify at normal temperatures, anti-condensation systems should be installed in the standby pumps and pipelines to prevent them from getting clogged ； (6) Safety valve line – For positive displacement pumps such as electric reciprocating pumps, gear pumps, and screw pumps, a safety valve line is provided on the outlet side; when the outlet pressure exceeds a set value, the safety valve opens and the fluid returns to the pump inlet pipe.

The statement on the 2nd floor is completely correct; for the specific pipeline layout design, refer to the second volume of the Chemical Process Design Manual

The heat pump line is essentially a bypass line for the outlet valve; the diameter of the pipeline for heavy oil is generally DN25, while for light oil or gases it is usually DN20 (mainly used for anti-freezing purposes in northern regions during winter). By taking advantage of the pressure difference between the outlet pressure and the inlet pressure, a low-flow circulation is created, allowing the fluid inside the pump to maintain a temperature that is the same as or similar to that of the system.