Mechanical seal Leak problem

[marzzia666]

I would like to ask anyone who has any experience with flowserve plan11/53B seal. In the drawing, it is instructed that the drain plug should be removed before operation, unfortunately the plug was not removed and the equipment was running for 3 months in this condition, then after 3months leaks was discovered in the shaft part beyond gland bushing. The drain plug was then removed but the leak in the drain was unacceptable. The green highlight in the attached drawing shows the path of the leak from the faces to the drain, but since the plug is not removed, it seems the green part was subjected to pressure (12barg). When the seal is dismantled, the gland bushing has two cracks opposite to each other. And the rotating face at the left side with the highlight has some deposit of carbon/rubber material (I think O-ring). The technician said that it can be because of misalignment but I cannot accept it since we do proper alignment of pump and motor, and there is no vibration experienced during the 3 months operation.
Questions:
1.What could be the reason for the leaking? Can this be because of the drain plug not removed?
2.Can the leaks be related to the broken gland bushing?

I hope someone could help me regarding this. Thank you very much.

 

[bk19702]

Was your Plan 53B piped to the proper connections? The gland bushing is the last item in the seal designed to mitigate the amount of leakage to the atmosphere should the outer seal fail. If you are suggesting you had 12 barg in this cavity between the outer seal and gland throttle bushing, then either something is not correct in how this seal is connected to the support system or your outer seal has failed miserably. You should have little to no pressure in that area of the seal, regardless of whether or not the drain plug is installed. The drain plug is left open to provide a tell tale of leakage past the outer seal; if the plug is left in then there is only one place for leakage to go and that is past the gland bushing and out of the back of the seal. The bushing appears to be a fixed clearance type and it won't restrict leakage as much as a floating or segmented bushing which have much tighter clearances, but it would still hold some pressure should the outer seal faces fail terribly and the cavity pressurize with barrier fluid. Did you get any alarms on the Plan 53B? How did the faces look?

 

[flexibox]

A few photographs may help but I would be looking at your venting to start with. BK19702 is correct, you do not normally have pressure gauges in the drain connection and if you had the plan 53B connected wrong, you wouldn't have run for 3 months. Why did you highlight the inboard dynamic Oring?
Your seal failure is not because the drain plug was in nor the broken bushing. Looks like this is an overhung impeller and perhaps cavitation has damaged the bushing. Also check the pressure trends on your plan 53B because it seems you have a connection for Plan11. Do you use this connection?

A few photos will help us solve your problem.

 

[marzzia666]

bk19702 and flexibox, thank you very much for your response.

We get low pressure alarm on seal plan. The faces of the outboard have some scratches according to vendor inspection report. the rotating face of inboard seal which I highlighted has some material deposit that seems to become embedded in the highlighted area. vendor said it is due to one side rubbing. the spring in the inboard seal part has also deposits of carbon particles, probably from the process fluid (hydrocarbon). 12 barg in the green area is just what goes to my mind, now I understand things better. I'm not sure if plan 11 was used. Maybe tomorrow I can provide some photos.

Thank you very much for the help.