Mechanical seal start-up exhaust?
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This post was last edited by Worker @ on 2015-10-26 06:50. The medium used in the high-temperature pump is residue oil, and double-end face mechanical seals are employed, arranged face to face； PLAN54 flushing protocol, using S2 as the isolation fluid ； Steam-cooled back side of the static ring for external sealing ； The problem now is that the pump requires frequent replacement of its mechanical seals. A set of repaired seals was just installed recently, but internal leakage occurred as soon as the pump started operating; most of the oil in the seal oil tank was lost, so the pump had to be shut down urgently ； Before starting the pump, a pressure test was conducted on the seal oil system, and no leaks were detected in the seals. Can this be used to rule out seal quality issues? Upon disassembling this set of mechanical seals, it was found that the graphite gasket on the inner rotating ring of the seal had been severed, and the rotating ring was displaced at its position relative to the shaft sleeve. {It is suspected that intense gas movement causes the moving ring to shift, thereby breaking the graphite gasket.} During the second maintenance session, a new mechanical seal was installed; while the pump was being warmed up, the seal oil system was put into operation. Is there a \"bang\"ing sound coming from the sealing chamber on the non-driving side? ； It is initially suspected that there is gas inside the sealing chamber; the seal oil outlet pipeline is equipped with a orifice plate, preventing the gas from escaping, which causes it to move violently continuously within the seal. . The most serious consequence is that the movement of the shaft sleeve can cause the end faces of the stationary and rotating rings to be damaged. Is it possible to install a shut-off valve in the outlet pipeline to allow air to be released before the pump is started? Is the above analysis reasonable? I would like to consult experts with experience in this field
First, rule out factors that are not related to assembly, and then work together with the production workshop to identify the cause!
Before installing the seal, check the coaxiality between the seal chamber and the shaft; poor coaxiality can lead to no leaks during pressure testing but leaks once the equipment is in operation. It is said that after adding the isolation fluid, the turbine must be rotated until the gas is completely discharged from the isolation fluid outlet.
Use the picture above. . . . Substantive
The PLAN54 flushing scheme relies on pressure lubrication provided by an oil pump
There are three imported feed pumps in total, with domestic and imported mechanical seals; the cost of replacements has already exceeded seven figures. . . . . The sealing environment is harsh, leading to frequent damage;; manufacturers, equipment technicians. . It can never be completely cured
The space at the sealed chamber is narrow, and this condition is not met. . . You say to check this coaxiality – I really have never checked it before
An increase in oil temperature leads to a vaporization process, which generates pressure in a sealed environment; therefore, a vent valve should be installed.
Where is the best place to install it? What is the nearest location of the export pipeline? The outlet pipeline has an orifice plate; shouldn’t it not be installed after the orifice plate?
It should be added at the highest point of the seal, as gas tends to accumulate at the highest location.
It is recommended to reselect the mechanical seal and ensure strict control over its quality. At the same time, please work together with the process team to conduct corresponding analysis based on the medium’s properties. 1. The rupture of the graphite ring is likely due to high specific pressure; reducing the specific pressure should solve the issue. 2. It’s also possible that the operator did not run the heat pump for long enough, or that the temperature rose too quickly. 3. Deformation of the sealing surface caused by excessive specific pressure at the end face seal due to thermal expansion of the spring. 4. The gas in the sealing chamber cannot be removed in a timely manner, resulting in the flushing mechanism losing its effectiveness or having reduced efficiency, which leads to excessively high temperatures in the mechanical seal. Personally, I think in situations like this it’s better to buy imported ones. ;P, it’s not that I admire foreign things to an extreme degree. Haha. Domestic products. You know what I mean.