system for lubricating mechanical seals

by:Lepu     2019-11-13
The mechanical seal combination includes a dual mechanical seal and a barrier liquid pump system.
Barrier fluid circulating pump 10 is coupled with the rotatable axis 3 in order to derive its power from the rotatable axis.
When the axis of rotation is not running, a-
By arrangement, the barrier fluid flows between the barrier fluid Collector Box 7 and the seal 3, avoiding the pump 10 and allowing the generation of a hot siphon effect.
Dual mechanical seals are usually placed at the interface between the process pump and the rotary axis of the drive pump.
The double mechanical seal is to avoid the loss of fluid from the pump in the area where the rotary axis can be inserted into the flow pump.
The rotatable shaft is usually driven by a motor.
Most double-mechanical seals have a cavity defined by the sealing surface, the sealing shell and the rotatable shaft through which the barrier fluid cycles, the proper operation of both sets of surfaces is supported by cooling the seal.
The barrier fluid is stored in the collector and cycled through the inlet and outlet pipes to the seal.
At present, there are two main systems for the circulation of barrier fluid.
The first uses a hot siphon and the second uses a separate circulating pump.
The thermosiphon system allows the removal of heat from the sealing surface through the circulation of water.
When the water is heated, it expands and thus becomes less dense than the cold water that enters.
Place the outlet in the sealing cavity above the inlet to ensure that the heated water is discharged from the sealing cavity and escape back to the collecting box.
Therefore, breathe cold water through the inlet.
Sometimes it is better to use oil instead of water as a barrier fluid, for example, the sealed product is incompatible with water.
Because when the oil is heated, the oil is not fully expanded to a hot siphon, it must be pumped around the system.
Barrier fluid must also be pumped, in which case a large amount of heat must be removed from the seal, for example, in the case of equipment being used with explosive chemicals, the building-
Heating can be very dangerous, or a differential pressure is required to ensure that the barrier fluid is on the sealing surface, not on the product.
In this case, a second motor has been used to drive the barrier fluid pump.
However, in areas where explosive chemicals are present, there may be problems with the use of a second motor, as the tendency of the motor and its electrical connections to cause sparks may be a fire hazard.
In addition, the use of the extra pump is historically very expensive because they are used in dangerous chemical environments and therefore need to meet strict safety requirements.
The collection box used in the pressurized system itself must also be manufactured in accordance with asme viii standards.
It was suggested to avoid the necessity of using a second pump and motor by installing fins on the sealed part connected to the axis of rotation, or otherwise modify the shape of the sealing cavity in order to allow the rotation of the shaft to cause flow.
However, it has been found that this design is much lower than expected and, while producing limited flow, may not be good enough for critical hazardous chemical systems, they do not produce enough positive pressure to produce a differential pressure on the sealing surface.
There is a double mechanical seal 6 around the rotary axis 3, which enters the pump 1.
The double seal 6 is typical because it includes both the inner and outer sealing surfaces and the gland housing, which together with the shaft defines the internal cavity that allows the barrier fluid to circulate.
Barrier fluid is stored in a container or tank 7 of the collection box and is directed by a double seal 6 through the down inlet tube 8.
The inlet tube 8 is connected with an external copper fin 8a to increase the heat dissipation rate of the blocking fluid.
Barrier fluid is recycled back to the Collector Box 7 through the outlet tube 9, which comes with a fin 9a that connects the top of the Collector Box 7.
The set box is mounted on the frame 11 which is rigid connected to the bed plate 12.
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