Mechanical Seal Flushing SolutionsMechanical Seals

During the operation of the pump, the seal in the seal chamber contains particles and impurities, which must be flushed, otherwise, due to the precipitation of crystals and the precipitation of particles and impurities, the dynamic and static rings of the mechanical seal will lose their floatability and the spring will fail. What's more serious is that the entry of particles and impurities into the friction pair will aggravate the wear and cause the rapid failure of the mechanical seal. Therefore, the mechanical seals used in general pumps should be flushed, especially for light hydrocarbon pumps.
Purpose of flushing:
⑴The liquid (external circulation) compatible with the medium is introduced into the sealing cavity to achieve: preventing high temperature, toxic and precious medium from leaking from the pump shaft; preventing medium containing solid particles from leaking into the sealing cavity and wearing the sealing surface; preventing The medium that is easy to vaporize and freeze (such as liquefied gas) leaks into the sealing cavity to generate gas, causing dry friction and wearing the sealing surface; prevent the medium that is easy to crystallize from leaking into the sealing cavity, and the sealing surface is worn due to the formation of crystallization due to cooling; down to prevent air and flushing fluid from leaking into the pump.
⑵ Cooling Prevent high temperature medium from entering the sealing cavity; guide the frictional heat generated when the moving ring and the static ring work
(3) Lubrication Keep a layer of liquid film between the sealing surfaces for lubrication.
The way of flushing:
1. Internal flushing
1. Positive flushing
(1) Features: Use the sealed medium of the working host to introduce the sealed cavity from the outlet end of the pump through the pipeline.
(2) Application: For cleaning fluid, p1 is slightly larger than p1, when the temperature is high or there are impurities, coolers, filters, etc. can be installed on the pipeline
2. Backwash
(1) Features: Using the sealed medium of the working host, it is introduced into the sealing chamber from the outlet end of the pump, and flows back to the pump inlet through the pipeline after flushing.
(2) Application: for cleaning fluid, and p into
3. Full flush
(1) Features: Use the sealed medium of the working host to introduce the sealed cavity from the outlet end of the pump through the pipeline, and then flow back to the pump inlet through the pipeline after flushing.
(2) Application: The cooling effect is better than the first two, and it is used for cleaning fluid, and p1 is close to p-in and p-out.
2. External flushing
Features: Introduce the cleaning fluid compatible with the sealed medium from the external system to the sealed cavity for flushing.
Application: The pressure of the external flushing fluid should be 0.05--0.1 MPa greater than that of the sealed medium, which is suitable for occasions where the medium is high temperature or solid particles. The flow rate of the flushing liquid should ensure that the heat is taken away, and it must also meet the flushing requirements without causing erosion to the seals. For this reason, it is necessary to control the pressure of the sealed cavity and the flow rate of flushing. Generally, the flow rate of the cleaning flushing liquid should be less than 5m/s; the slurry liquid containing particles must be less than 3m/s. The difference in pressure should be<0.5MPa, generally 0.05--0.1MPa, and 0.1--0.2MP for double-end mechanical seals. The orifice where the flushing fluid enters and exits the seal cavity should be set near the seal end face, and should be close to the moving ring side. In order to prevent the graphite ring from being eroded or deformed due to temperature difference due to uneven cooling, as well as impurity accumulation and coking, etc., tangential introduction or multi-point flushing can be used. If necessary, the flushing liquid can be hot water or steam.
Rinsing fluid requirements:
① Clean, non-corrosive without solid particles, low temperature (usually 40°C)
② It has certain lubricity and does not affect the quality of craft products;
③ It is not easy to vaporize under operating conditions;
④ Pay attention to the hardness of the cooling water, otherwise inorganic matter will accumulate on the shaft.