Questions about coke drum bottom unheading valve:
1. Do you follow the recommendation of refurbishing the valve every 8-10 years operation?
2. Do you observe significant wear during the turnaround
3. Have you ever run these valves for more than 10 years without refurbshing?
I think this is dependent on the pre-TAR inspection looking at
+ steam trends
+ HPU pressure/flow/history
+ history of operation
The longest I have heard is an overhaul every other TAR but most people do a overhaul each TAR.
Wear sites and locations varies between the TUD and BUD and the various generations of design. Seats, seals, and actuator components can see wear. The gates and body rarely see wear but it has happened for various reason. So it really comes down to your pre-TAR inspection.
These devices are in extremely severe service and are part of the coke drum pressure boundary. The steam purge flow trends are an indication about the condition of the device and provide some insight into how much work will be required at the turnaround. I would recommend a thorough inspection during each cycle ending turnaround and refurbishing the parts that show wear or cracks. Ten years is a very long time for equipment in severe, cyclic service.
There have been a number of improvements to these devices over the years that can only be implemented during an outage. A thorough review of the condition and upgrade options should be done prior to the turnaround to determine the scope of work for the turnaround.