Preheating with hot oil pump

It is by using a low flow rate to gradually heat up the pump body. The reasons for preheating a hot oil pump are as follows: (1) High temperature. The temperature of a hot oil pump is generally around 200–350°C. If it is not preheated, the pump body remains cold; when hot oil enters, the large difference in temperature can cause the pump to be unable to withstand such drastic changes, leading to leaks, cracks, damage to components, and issues arising from the different coefficients of thermal expansion, which can cause two parts to stick together. (2) High viscosity: The fluids transported by hot oil pumps have high viscosity; they solidify at normal and low temperatures, and may even freeze the pump components and pipelines, resulting in an inability to start the pump, low flow rates and head pressure, as well as vibrations and noise in the pump. A hot oil pump cannot be used without preheating, but under special circumstances, such as when it is necessary to start it urgently in the event of an accident, the preheating time can be reduced. The preheating method is as follows: (1) All pumps used for hot oil must always be in a hot standby state. That is, oil enters through the preheating pipe at the pump outlet, passes through the pump body, and then exits via the preheating pipe at the inlet to enter the pump’s inlet pipeline and feed the operating pump; when switching pumps, it can be started at any time. (2) If the standby pump is to be overhauled, it does not need to be preheated; the liquid inside the pump must be drained or emptied, and the pressure must be reduced to zero. After the overhaul, it should be promptly put back into hot standby mode. (3) Cooling water must be supplied to the cooling water jacket of the pump stuffing box (large cover) that is in the preheating stage, to prevent high temperatures from damaging the components or the packing or causing leaks; if necessary, a small amount of seal oil can be applied. (4) To prevent the running pump from being evacuated during the preheating of the standby pump, the outlet valve must be closed, the inlet valve opened, and the drain valve opened to release the air inside the pump before closing it again (someone should monitor this to prevent accidents caused by hot oil leaking out). Then, the outlet valve should be opened 3–4 turns to carry out the preheating process (if a preheating pipe is available, it should be used). (5) During preheating, turn the shaft 180° every 15–20 minutes to prevent bending due to uneven preheating temperatures. Do not use too much oil during preheating to prevent the impeller from rotating in reverse. (6) The pressure in the outlet pipeline of the hot oil pump is higher than the inlet pressure. Therefore, during preheating, the oil in the outlet pipeline can push the oil pressure from the preheating pump back. In this way, it serves as a preheating effect. (7) During preheating, if the pump operates to create a vacuum, preheating should be stopped; the vacuum must first be eliminated before preheating can proceed. (8) The preheating temperature should be increased gradually, usually by 50°C per hour; exceptions apply in special cases. Steam can also be used externally around the pump to assist with preheating, thereby increasing and accelerating the preheating rate.