We are operating a balanced draft heater in DHDS units. What should be the action on Forced Draft fan in case of tube rupture of the heater and why...?
Answers
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10/06/2013
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A:
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Alan Goelzer, Jacobs Consultancy, alan.goelzer@jacobs.com
A large pinhole leak or crack in high pressure HTU charge heater is a major emergency incident. Personally I recommend following upon detection or inference:
- Drop to pilots only [do not shut off pilots]
- Stop oil feed
- Stop make up hydrogen input
- Keep recycle compressor running
- Initiate reactor loop depressurization at 5% rate until further decision
- Trigger bypassing of air preheater and ID fan
- Keep Forced Draft fan operating
- Do not open ports in the HP charge heater to look into the firebox [On-line High Temp CCTV is best]
- If there is not very quick drops in temperatures [process outlet / radiant outlet / convection outlet], upgrade to 10% rate depressurization until loop presssure is down to less than 5 psig / 0.3 bart
Intention is to keep burning off any leakage fluids until fuel sources are removed, from the process side. Hopefully, this will mitigate damage to the coils and the fired heater.
Note that my best practices---with emphasis on risk management and routine operation high degreee of encon----favor process service being two phase and radiant only with forced draft fan without air preheat and individual heater stack. HRSG for making MP SH Steam is only convection service.
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