The previous article described about ALL WEILER sheet Screw pump This article will continue to introduce some key points that are easy to be ignored in selection and use.

5、 Matching between medium temperature and stator and rotor

In most cases, the medium transported by the single screw pump is in the normal temperature range, such as the working conditions of sewage and sludge transportation in the water treatment industry. However, for the transportation of a small number of high-temperature media, sufficient attention should be paid. For example, some pastes (ketchup, etc.) after high-temperature sterilization in the food industry, high-temperature starch after cooking in the paper industry, emulsion explosives, etc. The temperature of such media is usually close to or more than 100 ℃. This high temperature condition will be a great test for rubber parts such as rubber stator and universal joint sheath. It is very important to choose a rubber material that is compatible with the media and resistant to high temperature. Generally, ethylene propylene diene monomer (EPDM), fluororubber (VITON), or high nitrile rubber (HNBR) can be considered. It needs to be comprehensively considered according to different physical properties of the medium. However, if ordinary NBR is used, it will lead to premature wear, blocking or even degumming of the stator, especially when the rotor size does not match.

Clearance between stator and rotor

High temperature will lead to rubber expansion, which will increase the interference with the rotor, and lead to excessive wear, increased power consumption, difficult starting, etc. in the process of rotation. If it exceeds the design value too much, the expansion cannot be compensated, and the stator will crack and flake off. Therefore, under high temperature conditions, it is necessary to adjust the processing size of the rotor to leave compensation space for stator expansion. The compensation value varies according to the temperature range. However, this kind of compensation also requires comprehensive consideration of specific working conditions. For example, although the medium temperature is not low, and the transmission pressure is also high, it is not allowed to consider that the compensation amount is too sufficient, or the transmission pressure will be affected. For specific analysis, please consult the technicians of Shanghai Kunjin Electromechanical Co., Ltd. for details.

In practical application, ALLWEILER For some large users, there are more screw pumps of various models, and there may be more than one pump of the same model. Mixed use of high and low temperature pumps and spare parts is also common. Sometimes it will lead to unnecessary losses. For example, a pump configured at high temperature is used at normal temperature. Due to the large clearance between the stator and rotor, the flow and pressure cannot reach the standard. If the pump speed is increased blindly by DCS control, the stator and rotor will be worn quickly. If the pump is configured at normal temperature for high temperature conditions, the aforementioned damage such as stator cracking will occur. These are all things that the mechanic should pay extra attention to. If you cannot confirm the applicability of the pump or spare parts, you can always consult Shanghai Kunjin Electromechanical.

6、 Pump startup

Although the single screw pump has super self-priming capacity, experienced designers usually try to avoid working the pump in the suction state. The best layout is always to allow the medium to flow into the pump feed chamber automatically. For some special cases where the self-priming performance of the pump must be used, the pump suction chamber shall be filled with medium before starting. To ensure that there is sufficient medium flow between the stator and rotor during startup, so as to avoid dry operation or partial dry operation, and maximize the service life of the stator and rotor.

Foreign matter entering the pump

If possible, manually turn the pump before starting. In this way, part of the medium can enter between the stator and rotor to play the role of lubrication and cooling, and the second is to check whether the mechanical part of the pump is jammed or not. If there is no condition for hand turning, it is OK to jog several times, but pay special attention to whether there is abnormal noise or vibration near the pump. Once an exception is found, the startup process needs to be stopped immediately for further troubleshooting.