When high-temperature and high-pressure centrifugal pumps deliver media above 200°C, the pump must be warmed up before starting up. Otherwise, the medium entering the pump will cause the temperature in the pump to rise instantaneously, the rotor parts will expand rapidly, and the static parts will be heated relatively lagging behind, resulting in moving and static parts. The gap between them is reduced, and mutual contact, friction or seizure may occur. In severe cases, the dynamic balance accuracy of the rotor will be damaged, and the rotor may jam, which is often referred to as shaft holding. High temperature and high pressure pumps must be warmed up when transporting easily solidified media, otherwise the inlet and outlet pipes will be easily blocked by the solidified media, causing cavitation and vibration failures.
1. High temperature and high pressure centrifugal pump heating method
(1) When the heating pump unit is started after trial or overhaul, the high temperature and high pressure centrifugal pump should adopt the positive heating method, that is, the pump inlet valve is slightly opened, and the medium flows from the pump suction port through the pump body and discharges from the pump outlet pipeline guide valve. Go to the designated collection device. It can also be called an intermittent heat pump.
(2) Precautions The precautions for the high-temperature pump start-up heating pump are as follows:
1) The temperature rise rate of the heat pump is 15-30 ℃ /h.
2) When the difference between the temperature of the pump body and the temperature of the conveying medium is ≤20℃, the warming pump can end.
3) After the positive heating is over, close the heat pump pilot valve and start again when other driving conditions are met.
2. Spare heating method of high temperature and high pressure centrifugal pump
(1) The OH2 structure standby pump heating pump causes a small amount of material to be drawn from the discharge pipe through the operating pump, flow through the pump body of the standby pump, and then return to the pump inlet, so that the standby pump is in a hot standby state to prevent the standby pump and the suction and discharge pipes The internal medium is solidified to ensure that the heating pump is easy to start, which requires the use of inverted heating. That is to say, from the pump outlet pipeline shut off the valve and the heating pump line before the outlet check valve, a gate valve and orifice plate are set on the heating pump line, so that a small amount of material is drawn from the heating pump line through the main pump, and slowly flows through the pump body of the standby pump. Return to the pump inlet to achieve the purpose of continuous heating of the pump.
(2) BB2 structure standby pump heating pump BB2 structure pump, the method of warming standby high temperature and high pressure centrifugal pump is from the pipeline behind the stop valve of the pump outlet to the warm pump pipeline parallel to the pump discharge pipeline, and the medium slowly flows back to the pump. Gate valves and orifice plates are set on the inlet and heating pump pipelines.
(3) Precautions The precautions for the standby pump heating pump are as follows:
1) The flow rate of the heat pump should not be too large, preferably 3% to 5% of the rated flow rate to ensure that the standby pump will not reverse.
2) The heating pump valve must be closed after the standby pump is started.
3) The temperature rise rate of the heat pump is less than or equal to 20°C/h.
4) The temperature difference between upper and lower pump body is ≤35℃.
5) When the temperature difference between the upper part of the pump body and the temperature of the conveying medium is ≤25℃, the standby pump can be driven.
6) During the whole heating process, the standby pump is cranked once every half an hour, and the rotor is rotated 180° and parked. If cranking is difficult, stop cranking and wait until the temperature continues to rise for a certain period of time before proceeding.
7) According to the size of the pump outlet pressure and the calculation of the medium characteristics, select the appropriate orifice plate. If a single-stage orifice plate cannot meet the requirements, a multi-stage orifice plate should be selected to prevent cavitation and cavitation.
8) When the operating pump is switched to the standby pump, the appeal step adjustment is also carried out on it, and it is adjusted until it is ready to be turned on again.
3. Other
If the temperature is lower than the freezing point of the material, a warm pump bypass is also required to prevent the material from solidifying in the pump body. In addition, an anti-condensation bypass must be set between the inlet and outlet of the standby high temperature and high pressure centrifugal pump, and connect it to the pump after the shut-off valve at the outlet of the pump. Before the inlet shut-off valve, when repairing the standby pump, close the inlet and outlet shut-off valve of the standby pump and open the anti-condensation line valve. A small amount of liquid flows slowly in the inlet pipe section of the pump to ensure that the fluid in the pipeline does not condense.
