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Home   |   Case Studies   |   Seal repair & upgrade improves reliability of De Dietrich glass-lined biconical dryer

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Seal repair & upgrade improves reliability of De Dietrich glass-lined biconical dryer

Cutting an international agrochemical manufacturer’s downtime from 18 weeks to 9 weeks avoided significant lost production on a newly commissioned De Dietrich biconical dryer

Client challenge:

When a John Crane P32SP 160mm dry running seal failed shortly after the dryer was commissioned for the first time, the user faced significant production losses as they had no spare seal, no spare parts and poor response from both the seal and dryer OEMs. The lead time for either a new seal or the necessary seal spares was 18 weeks. So the user turned to NASH for help.

Our response:

Working closely with the client, we were able to quickly identify the 2 issues that had caused the seal to fail:

  • Inadequate structural support had caused the dryer pedestals to rock axially and the dryer to move out of level during operation, leading to failure of the bearing
  • The seal sleeve had moved axially during operation, unloading the seal and causing it to leak

Although the seal appeared to have failed catastrophically (see as received photo below), it was soon established that much of the damage to parts occurred during removal because the seal was seized on the vacuum tube due to the combined effects of the bearing failure and axial movement of the seal.

 

Fully disassembled seal

A plan was agreed involving NASH repairing and upgrading the seal in parallel with the user strengthening the dryer support structure. The target lead time was 8 weeks.

Seal repair and upgrade workscope:

  • Replace both rotary and stationary seal rings
  • Manufacture replacement spring plate
  • Manufacture replacement composite sleeve in Hastelloy C22/316
  • Manufacture replacement bearing housing
  • Manufacture replacement bearing bush
  • Design and manufacture a new drive arrangement (see drawing below)
  • Replace all secondary seals, springs and fasteners
  • Seal re-assembly
  • Pressure test per API682 air test
The drawing above shows the additional drive collar (Item 84), designed to make use of a positive abutment on the vacuum tube to prevent the seal sleeve moving down the shaft during operation. The original drive collar (Item 45) would not hold the seal in position because the wall thickness of the vacuum tube underneath it was not substantial enough and the tube deformed when the drive collar was tightened.

The seal was repaired and upgraded on time in 8 weeks and the supporting structure was strengthened. The seal was successfully installed and the dryer was re-commissioned without further delay.

Client benefits:

  • Projected plant downtime was reduced by 50%
  • Lost production was minimised
  • The client was ultimately able to meet the needs of their customers
  • The ongoing reliability of the dryer was assured

NASH was able to resolve a challenging engineered mechanical seal problem when no other company could. If you find yourself in a similar situation, please feel free to contact us – we’d be delighted to help!

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  • enquiry@nashseal.com
  • +44 (0) 1204 388 030
  • NASH Mechanical Seal Services Ltd, Nile Street, Bolton, Lancashire, BL3 6DW, England
    Company Registration Number: 01803027

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