Discussion on mechanical seal flushing scheme
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API682 states that \"Solution 52 is not suitable for dirty or aggregating media; in such cases, Solution 53 should be considered.\" In fact, I encountered a sealing and flushing configuration for such a centrifugal pump: the medium used was relatively pure methanol, the operating pressure in the sealing chamber was around 1.1 MPa, and the flushing scheme selected for the mechanical seal was PLAN11+53A+62(N2). My understanding is that since the first seal uses the PLAN11 self-flushing scheme, it’s a bit odd for the second seal to use the PLAN53A sealing scheme; switching to the PLAN52 scheme fully meets the requirements. I would be grateful for the expert opinions on the above questions. Please feel free to share your insights.
Personally, I think it makes more sense to combine PLAN53 with PLAN31 or PLAN32
The working pressure is 11 kg, while there is no pressure at 52; in terms of combinations, it can be said that 11 and 62 are also useless.
My personal understanding is that the purpose of using 52 in a pressure-free environment is to allow a slight leakage of the clean process medium into 52, while using 53A under pressure is intended to prevent the sealing surfaces of 53A from being contaminated by the process medium. API682 suggests using 53A when the medium is dirty; therefore, since 53A is chosen, it implies that the medium is assumed to be dirty. If the medium is dirty, then using the flushing method associated with 11 for the first seal isn’t very appropriate, as the dirty medium can contaminate the sealing surface of 11, thereby reducing its service life. Looking back at the 11+53A+62 configuration for this methanol pump, the methanol medium is actually very clean; therefore, it is appropriate to use 11 as the first seal. Using the energy-efficient 52 for the second seal is also more than sufficient. The 53A used for the second seal is somewhat overkill and represents a waste. The above is my personal understanding of sealing.
Looking at this pump as well, the medium used is methanol, and the operating pressure in the sealing chamber is 4.45 MPa. A 11+52 sealing scheme is employed; therefore, in my opinion, the operating pressure of the sealing chamber is not the main factor that determines whether to use model 52 or 53A.
52 will cause volatile light components to leak slightly into the system, while 53 will cause the isolation fluid to leak into the pump chamber. 53 indicates that leakage from the pump chamber into the system is not acceptable, while leakage from the system into the pump chamber is acceptable. “API682 specifies that 53A should be used when the medium is dirty; therefore, my understanding is that since 53A is chosen, it implies that the medium is assumed to be dirty. This logic seems a bit forced – couldn’t 53A still be used even if the medium is clean?
Returning to the original question: since both pumps use methanol, is it a waste to specify a 53A model?
It depends on the company’s requirements; if they are high, a 53a leak rate is sufficient, and completely preventing the leakage of hazardous substances is also a good option.
It makes sense; people have different views on the balance between safety and environmental protection on the one hand, and energy conservation and consumption reduction on the other. Some prioritize safety and environmental protection, while others focus on energy conservation and consumption reduction. The regulations do not provide clear guidelines for this balance
Personally, I think 53A is better; with stricter environmental regulations, many devices are required to have no leaks
52 and 53A were determined based on the owner’s requirements and understanding of environmental protection, which led to different solutions for the same medium. Could someone help me understand why, if 53A was chosen, 62 is still needed?