The previous article described about ALL WEILER sheet Screw pump For most of the basic knowledge related to model selection, this article will continue to introduce some key points that are simply neglected in model selection and application.

5、 Matching between medium temperature and stator and rotor

In most cases, the medium transported by the single screw pump is of normal temperature scale, such as working conditions such as sewage and sludge transportation by water treatment professionals. However, with regard to the transportation of a small number of high-temperature media, the demand has attracted sufficient attention. For example, some pastes (ketchup, etc.) after high-temperature sterilization in the food profession, high-temperature starch after cooking in the papermaking profession, emulsion explosives, etc. The temperature of such media is generally close to or above 100 ℃. Under this high temperature condition, there will be great detection on 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. The demand is summarized and considered according to the different physical properties of the medium. However, if the general nitrile rubber (NBR) is selected, it will lead to premature wear, blocking and even degumming of the stator, especially when the rotor dimensions do not match.

Clearance between stator and rotor

The high temperature will cause the rubber to swell, and then increase the interference with the rotor, resulting in excessive wear, increased power consumption, and difficulty in starting during the rolling process. If the planned value is exceeded too much, the expansion cannot be compensated, and the stator will appear cracking, falling in pieces and other conditions. Therefore, under the high temperature condition, it is required to adjust the processing scale of the rotor to leave compensation space for stator expansion. According to different temperature scales, the compensation value is also different. However, this kind of compensation also needs to be summarized to consider the detailed working conditions. For example, although the temperature of the medium is not low, the transportation pressure is also high. At this time, it cannot be considered that the compensation amount is too sufficient, or the transportation pressure will be affected. For detailed analysis of the situation, please consult the technicians of Shanghai Kunjin Electromechanical Co., Ltd.

In practice, for some large users, there are many screw pumps of various types, and there may be many pumps of the same type. Mixed use of high and low temperature pumps and spare parts is also common. Sometimes it will lead to unnecessary loss. For example, a pump equipped with high temperature equipment is used under normal temperature conditions, because the clearance between stator and rotor is too large, the flow and pressure cannot be qualified. If DCS is used to control and improve the pump speed, the stator and rotor will be worn quickly. If the pump is equipped at normal temperature and used at high temperature, the aforementioned damage such as stator cracking will occur. These are what the maintenance personnel should pay attention to. If you cannot acknowledge the applicability of the pump or spare parts, you can always consult Shanghai Kunjin Electromechanical.

6、 Start of pump

Although the single screw pump has super self-priming ability, experienced planners generally try to prevent the pump from operating in the suction state. The best layout is always to allow the medium to flow into the pump feed chamber automatically. If it is necessary to use the self-priming function of the pump under some special conditions, the pump suction chamber should be filled with medium before starting. In order to ensure that there is sufficient medium flowing between the stator and rotor in the process of starting, and then prevent dry work or partial dry work, so as to maximize the service life of the stator and rotor.

Foreign matter entering the pump

If possible, manually crank the pump before starting. In this way, part of the medium can enter between the stator and rotor, which has a smooth and cooling effect. Secondly, it can check whether the mechanical part of the pump has abnormal conditions such as jamming. It is true that there is no condition for hand turning, so it can be jogged several times, but you need to pay special attention to whether there is abnormal noise or abnormal oscillation around the pump. Once abnormality is found, the launch process shall be stopped immediately for further investigation.

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