Regarding mechanical seals

Generally speaking, it is said that the seal can remain intact for a year, but this is not usually achieved due to vacuum conditions or abnormal shutdowns. When using that special instrument to observe the interference fringes on the sealing surface, it is best to have average interference fringes that are also densely packed on average. Old sealing surfaces that are not broken can be ground; scratches can also be ground, but those that are broken cannot be repaired. Also, check whether the bellows are broken – they are part of the compensation mechanism. Other water pumps can allow a slight leak – it’s up to you to determine the medium. Liquefied gas and things like that definitely can’t be ground

With new mechanical seals, their service life is reduced after maintenance; it’s better to find out the reason for that. If the operating conditions of the mechanical seal are stable, it should work fine for several years. We here have seals that are two years old and they’re still working fine. DanDong Klon is considered one of the better manufacturers in China. The repair of mechanical seals is usually carried out by the manufacturers themselves; they use grinding machines to make repairs. Generally, they check whether there are any deep grooves on the sealing surfaces. If there’s no leakage, then the rotating and stationary rings are aligned again, and the seal should be able to function properly. This is just a partial view based on personal experience; it’s meant for reference only

Generally, light oil pumps can last for over 1 year, sometimes even two to three years (with one in use and one as a spare, inspected monthly); it is recommended to use them after grinding. There isn’t much of a problem with leakage issues. High-temperature oil pumps, those used for liquefied gas, or systems dealing with acidic water, where leakage must be avoided, should use new pumps

As a reminder, the original poster should take a close look at the area where leakage is occurring; it’s possible that oil is leaking from the shaft coupling rather than due to a problem with the mechanical seal.

Sometimes leakage isn’t necessarily caused by a damaged seal; even if the seal isn’t installed properly, leakage can still occur. Grinding the stationary and rotating rings might also help, in my opinion. But still, we end up replacing the seal in all cases! !

Mechanical seals don’t need to be replaced just because there’s a leak; it depends on the type of fluid involved. For fluids that are not very important and don’t cause much environmental pollution, there’s no need for such strict requirements. As for the lifespan of mechanical seals, it depends on the manufacturing conditions and the quality of assembly. There isn’t much difference between manufacturers; certainly, those from abroad are generally of better quality, but they are also more expensive.

If there are many seal failures over a certain period of time, the first possible cause is changes or significant fluctuations in your manufacturing processes. The second possibility is that there is a problem with the quality of these mechanical seals, or that they have reached the end of their useful life. If this situation persists from the start of operation, the selection of the mechanical seal should be considered.

There is a standard for seal leakage: for example, 20 drops per minute for heavy oil and 10 drops per minute for light oil. Based on this, it can be determined whether repairs are necessary. Additionally, for more expensive seals, it may be possible to extend their useful life, even if leakage has already started (provided that the medium is clean). For critical equipment such as heat transfer oil pumps, a decision must be made on-site depending on the circumstances, so as not to disrupt production. 2 For liquid hydrocarbon pumps, basically, if the leakage is not severe, it is possible to continue operating them with steam protection; on one hand, this may prevent further leakage, and on the other hand it can help avoid safety accidents. If there is a significant leak of liquid hydrocarbons, it’s better to carry out repairs, as this substance is quite dangerous. Whether grinding is necessary depends on your attitude and that of the fitter. In general, if a mechanical seal leaks, it can definitely be ground, and after grinding it can even be used for a longer period of time. However, this depends on the skill level and attitude of the fitter, so all factors need to be taken into consideration; here we usually opt for replacement instead. 4 If a pump keeps leaking and requires frequent repairs, then it’s time to consider replacing the seal – continuous leakage is definitely not acceptable. 5 A general principle: the decision of whether to repair something or not should rest with those in charge of the equipment; however, in any case, production operations must not be affected! This is the red line

If the service life of the mechanical seal is too short and it needs to be replaced frequently, there is definitely a problem. 1. Check whether the correct model has been selected based on the medium used and the operating conditions. 2. Examine whether there are any issues with the installation of the mechanical seal. 3. Determine if there are problems with the operation of the equipment; excessive vibration can damage the seal. 4. It is not recommended to attempt repairs or grinding; instead, the root cause should be identified and addressed.

This post was last edited by Feng Yiran on 2012-4-12 at 15:56. First of all, one shouldn’t try to polish it without professional skills; it’s likely that you won’t be able to do a good job of polishing it, and there will be leaks if done improperly, let alone when trying to do it by oneself. Second, check whether the medium is a bit dirty. Third, if it’s not a pump that operates continuously, verify whether it is still running while under vacuum conditions. Fourth, the quality of installation. Fifth, the quality of spare parts