Extensive mechanical seal face and o-ring damage linked to high ferric oxide concentrations in power station feed water was repaired within a European client’s tight cost and time expectations.
Following the failure of boiler feed water pump mechanical seals – thought to be caused by a combination of incorrect o-ring specifications from a different vendor and ferric oxide deposits in service – a major European power station was forced to rely on its spare seal set. Restoring the damaged seals became an urgent priority.
Rather than go back to the seal OEM, our client – a pump service specialist – asked NASH to examine and repair the damaged seals so they could return them to their customer’s site as quickly as possible to minimise plant vulnerability.
A GA drawing and duty conditions were available. It was also confirmed that the seals had run hot prior to their removal. NASH analysed the damage and generated detailed Inspection Reports.
These showed: –
- Heavy wear on the stationary seal rings, with chips to inside and outside face edges
- Heavy fretting on the sliding diameters of the stationary seal ring carriers
- Heavy wear on the inside diameters of the associated dynamic o-rings
- Heavy wear to the faces of both rotary seal rings
- Seal plate safety bushes were also worn and loose
- Importantly, both seals were contaminated with ferric oxide (magnetite) deposits
We concluded that the root cause of seal failure was a combination of incorrect o-ring specifications and a build-up of ferric oxide particles and deposits in the pump system.
Work scope: –
- New rotary and stationary seal rings supplied and fitted
- Sliding diameters of both stationary carriers recoated with tungsten carbide
- New springs, fasteners and elastomers to correct specification supplied and fitted
The NASH team also advised that to prevent any recurring damage: –
- Associated equipment and line work should be inspected and cleaned to remove all ferric oxide build-up
NASH was able to: –
- Restore the seals to original specification
- Ensure further premature seal failures and consequent unplanned outages were eliminated
- Meet both the client’s and the client customer’s tight lead time expectations
- Provide a more cost-competitive service than the seal OEM