Why does a hot oil pump need to be preheated? How to preheat?

:Lol, the thermal expansion must be uniform, with a thermal expansion curve

This post was last edited by Green Lotus on 2019-1-13 at 14:49 (1) High temperature. The operating temperature of hot oil pumps is generally around 200~350°C. If preheating is not done, when hot oil enters a cold pump body, the pump cannot withstand such a sharp change in temperature, which can lead to leaks, cracks, damage to components, or the two parts may get stuck together due to differences in their expansion coefficients. (2) High viscosity. The media transported by hot oil pumps have relatively high viscosity; they solidify at normal and low temperatures, and can even seal up the pump’s 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. However, in special circumstances, such as when an accident occurs and activation is required, its preheating time can be shortened. The preheating method is as follows: (1) The pump 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 through the preheating pipe at the inlet to enter the pump inlet pipeline and reach 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 require preheating; the liquid inside the pump must be drained or emptied, and the pressure must be reduced to zero. After the maintenance is completed, it should be promptly put into hot standby mode. (3) Cooling water must be supplied to the cooling water jacket of the preheated pump stuffing box (large cover) 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) It is absolutely forbidden to reverse the pump during preheating. (5) 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, the drain valve activated to remove the air from the pump, and then closed again (someone must monitor to prevent accidents caused by hot oil leaking out). Open the outlet valve 3–4 turns to preheat (use a preheating tube if available). (6) During preheating, turn the shaft 180° every 15–20 minutes to prevent bending due to uneven preheating temperatures. During preheating, do not use too much oil to prevent the impeller from rotating in reverse. (7) During preheating, if the pump starts pumping vacuum, preheating should be stopped; vacuum pumping must be halted first before preheating can resume. (8) The preheating temperature should be increased gradually, usually by 50°C per hour, with exceptions in special cases. Steam can also be used externally to the pump for auxiliary preheating, in order to speed up the preheating process.

If normal operation is to proceed, preheating with the medium during the startup phase should be sufficient, right? Is there any procedure that requires the use of steam separately? I guess the condensation water has accumulated

Steam preheating is rarely used; generally, the medium used by the pump itself is employed for preheating

The preheating of the low-pressure pump in our pressure reduction tower often leads to the pump running dry. Could everyone help resolve this issue and analyze the reasons?

A hot oil pump operates in hot conditions; it performs very well at certain temperatures, but its performance is not as good when working in cold conditions, which is why preheating is necessary. Taking the American SR71 Blackbird as an example, its flight speed is extremely high; therefore, when it is not in flight and located at the airport, oil leaks from this aircraft. Once it reaches the air and attains a certain speed, the thermal expansion caused by that speed fills up those gaps.

Preheating is intended to ensure that the machine pump can be switched over promptly when needed; without preheating, emergency pump switching may cause damage to the pump due to uneven heating. Make a cross connection of DN20 or 25 at the outlet valve. Drive less usually; ensuring proper preheating is sufficient.