Mechanical seal leakage
Thread Content
Our factory has two self-priming pumps from 2017 used to pump xylene; these pumps serve a dual purpose: for unloading material and supplying it to the workshop. In one of the pumps, the outlet pressure during operation is high (compared to the pump’s own parameters), which causes leakage at the mechanical seal. During unloading, the pump outlet pressure was 0.06 MPa, and the mechanical seal was in good condition. However, when conveying the medium to the workshop and the pump outlet pressure reaches 0.3 MPa, leakage occurs at the mechanical seal. New bearings and pump shafts have been installed, the bearing housings have been replaced, and the type of mechanical seal has also been changed from the original 120 type to a 128 type made of PTFE and cemented carbide – yet the leakage persists. The unit’s concentricity has also been recalibrated. The sound and vibration of the pump in operation at the site are normal. I was wondering if anyone could help me analyze the reasons behind this and suggest some good solutions. In both operating conditions, the pump inlets are under backflow.
Mechanical seal leakage source: 1. Moving and stationary friction surfaces； 2. Dynamic ring O-ring ； 3. Static ring O-ring. Factors to consider include: 1. Rotational speed ； 2. Material of the stationary and rotating rings of the mechanical seal ； 3. Material of the O-rings in the dynamic and static rings of the mechanical seal (compatibility with the medium) ； 4. Surface finish of each assembly point for the stationary and rotating rings ； 5. Compression amount of the stationary and rotating rings and assembly accuracy. By eliminating them one by one as mentioned above, it’s generally possible to find the cause.
The compression level is too low; increase it
It seems there might be an issue with the pump selection; replacing the self-priming pump with a magnetic drive pump or a multi-stage pump could help. Because there is a spring inside the mechanical seal, and it will leak when the pressure exceeds its capacity.
The outlet pressure is 0.3 MPa, which is not very high; adjusting the compression amount of the machine seal spring should resolve the issue. If strict airtight sealing is required, then switch to a magnetic pump or a shielded pump
For mechanical seals, multiple springs or double-end faces can be considered
The pressure may be too low, or the sealing ring could be damaged, the end faces might be misaligned, and the compensation mechanism could get stuck – any of these issues can cause leakage in the mechanical seal, and it is necessary to investigate these possibilities
\ud83d\udc4d\ud83c\udffb
If there is no pumping phenomenon, then consider the issue of insufficient compression. Additionally, the material of the stationary and rotating rings may not provide good sealing performance for this medium