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3 shielded pump type and scope of application
Depending on the temperature, pressure, viscosity, and presence or absence of particles in the delivery fluid, the shield pump can be divided into the following categories:
(1) basic type
Transmission medium temperature does not exceed 120 ℃, head does not exceed 150m. Various other types of shielding pumps can be based on the basic type, through the modification and improvement.
(2) reverse cycle type
In this type of shielded pump, the direction of fluid flow through the bearing lubrication, cooling, and cooling of the motor is exactly opposite to the basic one. Its main feature is not easy to produce cavitation, especially for easy vaporization of liquid transport, such as liquefied petroleum gas, chloroform and so on.
(3) high temperature type
General transport medium temperature up to 350 ℃, the maximum flow 300m3 / h, head up to 115m, suitable for hot medium oil and hot water and other high temperature liquid.
(4) high melting point type
Pump and motor with a jacket, can greatly improve the motor heat resistance. For high melting point liquid temperature up to 250 ℃. Jacket can pass steam or a certain temperature of the liquid, to prevent the crystallization of high melting point liquid.
(5) high-pressure type
The housing of a high-pressure shielded pump is a high-pressure container that allows the pump to withstand high system pressures. In order to support the shield under internal high pressure, the stator coil can be used to withstand the pressure.
(6) self-priming type
When the suction tube is not filled with liquid, the pump drains liquid through an automatic suction action and is adapted to extract the liquid from the underground container.
(7) multi-level type
Equipped with multiple impeller, suitable for high-lift fluid delivery, the maximum lift of up to 400m.
(8) mud type
Suitable for transporting liquids mixed with a large amount of mud.
4 shield pump selection precautions
The general shielding pump uses a part of the liquid transported to cool the motor, and the annular gap is small, so the liquid must be clean. For conveying a variety of liquid mixtures, if they produce precipitation, coking or jelly, then the selection of shielding pump (non-mud type) may block the shielding gap, affecting the pump cooling and lubrication, resulting in burning graphite bearings and motor burn.
Shielded pumps are generally circulating cooling pipe, when the ambient temperature is lower than the freezing point of the liquid pumped, the anti-freezing measures should be used with the accompanying pipe to ensure easy start-up pump.
In addition, the shield pump should strictly comply with the opening sequence of the outlet valve and inlet valve at start-up. When the pump is stopped, the outlet valve should be closed first. When the pump operation is stopped, the inlet valve is closed and the outlet valve is closed.
In short, the use of shielded pump, completely leak-free, effectively avoiding environmental pollution and material loss, as long as the correct selection, the operating conditions did not abnormal changes in normal operation, almost no maintenance workload. Shielded pump is the ideal pump to transport flammable, explosive, corrosive and valuable liquid.
Shielded pump performance characteristics and selection (2)
(3) For a long period of time, operating at a low flow rate, shielding pump efficiency is low, will lead to heat, liquid evaporation, resulting in dry pump rotation, thus damaging the sliding bearing.