Case Studies

The Problem

A major pump maker sent a flexibox mechanical seal to NASH for an independent failure analysis and report.

The seal was from a boiler circulation pump operating on a UK power station.

The seal was a robust high duty single cartridge seal with silicon carbide v carbon faces, plus Kalrez and filled PTFE secondary seals.

After operating for only four weeks, a gradual increase in leakage became excessive. This was a recurring problem and the pump maker was not happy with the support from the seal OEM.

Looking for independent technical support to improve the seal performance they sent the seal to NASH.

The Solution

NASH carried out a detailed failure analysis and compiled a report with recommendations to improve performance together with quotations for repair and modification.

The seal failed due to severe abrasive wear of both faces.

This was clearly caused by fine abrasive magnetite (ferric oxide) in the water; a common problem on this type of application.

The faces also showed evidence of poor film formation, again a common problem with water at high temperature. The seal also leaked due to degradation of the Kalrez o-rings, whichwas of a grade unsuitable for hot water.

NASH repaired the seal and changed the face materials to significantly improve wear resistance and thermal conductivity. The o-ring material was also changed to a perfluoroelastomer suited to hot water duty.

The modifications improved seal performance significantly leading to the change out of other seals on the plant.

The Benefits

NASH provided the Pump OEM and end user with an alternative service solution.
Significant cost saving on seal repair.
Significant increase in seal service life.
Reduction in plant down time.

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