Sealing problems in liquid hydrocarbon pumps
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Sealing problems with liquid hydrocarbon pumps: It’s happened three times in a row; the seals need to be replaced on average once a month. The model is a bellows mechanical seal of type DBM90B-1\W-M with resin impregnation, designed for use with liquid hydrocarbons. I’m not sure what the cause is
For the sealing of liquid hydrocarbon pumps, we are currently using cascade seals, which have proven to be very effective; there have been no leaks in the seals over the past two years.
The original poster, please be more specific – what circumstances are causing the seals to need to be replaced so frequently? It's better to describe the specific phenomena before analyzing them.
Pay attention to the operation of the pump and ensure a sufficient inlet pressure to prevent the medium at the pump inlet from vaporizing, which could lead to vacuum formation within the pump. This can easily cause the seal to fail. (Because dry friction occurs between the sealed stationary and rotating rings due to the lack of flushing fluid)
There’s nothing special about it either. It’s working normally. At first, there was a scraping sound coming from the sealing area; later, liquid hydrocarbons started to leak. However, the pressures at the inlet and outlet were normal. Now, the seal is making noise again
Liquid hydrocarbon pumps are prone to leakage, as the properties of the medium are very poor; once the pump is evacuated, the sealing surfaces wear out rapidly and the rotor loses its balance. Our factory has also experienced leaks, but fixing them resolves the issue and prevents further leakage
Liquid hydrocarbons (light hydrocarbons) present challenges in terms of sealing; due to their volatile nature, specialized design is required, as standard products alone cannot meet the sealing requirements. Ordinary bellows come with standard seals and are not suitable for sealing light hydrocarbon fluids, unless specific modifications are made. The manufacturers that are good at producing such seals abroad are John Crane, while in China it’s Dalian Huayang; actually, they produce the same type of seals. There are four specific seal designs designed for use in light hydrocarbon applications, and these seals perform very well when used in series.
It is recommended to try a series-mounted mechanical seal. Liquid hydrocarbons have high saturated vapor pressures, and they easily vaporize as the temperature rises, leading to dry friction damage of the mechanical seal.
Liquid hydrocarbons have very poor self-lubricating properties. After operating for a while, if there are problems with cooling – and generally DBMs use self-flushing cooling methods – the heat generated between the frictioning surfaces cannot be removed; as a result, the liquid hydrocarbons vaporize, leading to phenomena similar to flash explosions. This causes the stationary and rotating rings to open and close, producing sounds of metal colliding； At the same time, liquid hydrocarbons also leaked intermittently ； Over time, scratches appear on the sealing surface, leading to seal failure. It would be better to change its cooling method to forced water flushing.
I just checked the forum and found some great materials that might explain these reasons in more detail; you can take a look: http://bbs.hcbbs.com/thread-30418-1-72.html； http://bbs.hcbbs.com/archiver/tid-177070.html