1. Impeller of heat transfer oil pump
The impeller is a key component of the heat transfer oil pump.
(1) According to its mechanical structure, it can be divided into three types: closed type, semi-closed type and open type. Closed impellers are suitable for conveying cleaning fluids; semi-closed and open impellers are suitable for conveying suspensions containing solid particles, which are inefficient.
When the closed and semi-closed impellers are in operation, a part of the high-pressure liquid leaving the impeller can leak into the cavity between the impeller and the pump casing. Since the pressure at the liquid suction port on the front side of the impeller is low, the liquid acts on the front and rear of the impeller. The pressure on the sides is not equal, and an axial thrust directed to the suction side of the impeller is generated. This force pushes the impeller to move toward the suction side, causing friction at the contact between the impeller and the pump casing, causing vibration of the pump in severe cases and damaging the normal operation of the pump. Drilling a number of small holes in the rear cover of the impeller reduces the pressure difference across the impeller, thereby reducing the adverse effects of axial thrust, but at the same time reducing the efficiency of the pump. These small holes are called balance holes.
(2) According to different liquid absorption methods, the impeller can be divided into single suction type and double suction type. The single suction type impeller has a simple structure, and the liquid can only be sucked from one side. The double suction impeller can simultaneously draw liquid symmetrically from both sides of the impeller, which not only has a large liquid absorption capacity, but also substantially eliminates the axial thrust.
(3) According to the geometry on the blade on the impeller, the blade can be divided into three types: back bend, radial and forward bend. Because the back bend blade is beneficial to the conversion of kinetic energy of liquid into static pressure energy, it is widely used.
The snail-shaped pump casing, the back-bending blade on the impeller and the guide wheel can all improve the conversion rate of kinetic energy to static pressure energy, so they can all be regarded as energy-transfer devices.
2. Shaft sealing device
Since the pump casing is fixed and the pump casing is fixed, there must be a certain gap at the contact between the shaft and the pump casing. In order to avoid leakage of high pressure liquid in the pump along the gap or to prevent outside air from entering the pump from the opposite direction, a shaft seal device must be provided. The shaft seal of the centrifugal pump has a stuffing box and a mechanical (end) seal. The stuffing box is used to seal the pump shaft through the annular gap of the pump casing, and a soft packing (such as oil-impregnated or graphite-coated asbestos rope) is placed therein. The mechanical seal consists of a moving ring mounted on the rotating shaft and another stationary ring fixed to the pump casing. The end faces of the two rings are relatively rotated by the spring force to act as a seal. Mechanical seals are suitable for applications where the seal is high, such as the transport of acids, bases, flammable, explosive and toxic liquids.
3. Guide wheel of heat transfer oil pump
In order to reduce the energy loss caused by the impact when the liquid leaving the heat transfer oil pump impeller directly enters the pump casing, a fixed and vaned guide wheel is sometimes arranged between the impeller and the pump casing. The vanes in the guide wheel gradually turn the liquid entering the pump casing and the flow passage continuously expands, so that part of the kinetic energy is effectively converted into static pressure energy. Multistage centrifugal pumps are usually equipped with guide wheels.
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Label: Introduction to the impeller and other components of the heat transfer oil pump
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