Here is another mechanical seal failure.

This occurred on one of a duplex pump set, or more accurately Twin Head Single Stage in line pumps Grundfos Type TPD (motors in vertical position). These pumps are on the primary circuit of a hot water boiler. They circulate water from a suction header through the boiler to a discharge header ona closed circuit. Suction pressure at inlet is 2.6 bar. Discharge of pump is at 3.6 bar. This is a new installation in service for about 8 months. The pumps alternate duty automatically. Water temperature is about 75degC. Suction header is about 1 metre above pumps and the highest elevation is 2.3 metres above pumps. Pipe lengths are relatively short as the pumps are located under the headers and the boiler is some 4 metres away. A strainer and isolating valves are installed. Nothing abnormal was noted on the pump operation, no noticeable vibration whatsoever. Then the seal of one of the pumps started leaking noticeably. These pumps arrived completely mounted so they are just put in location.

I'm a bit perplexed as I think it was practically impossible to run these pumps dry, so I thought you might have some suggestions on the cause of this failure. We have'nt stripped it yet as we're awaiting parts delivery.

Thinking aloud:
- seal tension relaxed due some loosening
- dirt entrapment
- other?

I think you should proceed to strip it ASAP to allow times to inspect the mech seal (to determine type of wear) rather than wait for the parts delivery and start troubleshooting or RCA as early as possbile. Of course, have to protect it after dismantle in the workshop.

What type of mech seal is it, from the pump drawing?

Could you say what sort of Mechanical Seal you are using? i.e Single seal, Tandem or Dual pressurised?

What brand is it?

This is the pump in question.

TPD50.pdf (93 Kb, 60 downloads) Boiler Pumps