A problem in the process design prevents the fuel gas from being vented after an ESD event
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In a gas power generation project abroad in 2017, after the gas from the upstream gas field arrived, it passed through a fuel gas treatment skid before entering three compressors to increase its pressure, and then it was sent to gas turbines for power generation. In this seemingly simple process system, the design team failed to consider everything properly; two check valves were installed at the outlet of the fuel gas treatment skid. As a result, when an ESD event occurred, the inlet isolation valves of the three compressors closed, while the fuel gas treatment skid and the three compressors each activated their own ESD vent valves to release gas from the system. This led to the gas in the pipe section ranging from the check valves at the outlet of the fuel gas treatment skid to the inlet isolation valves of the compressors not being able to be vented. Since the project is about to start operation, it’s too late to make any design changes. As the contractor responsible for the commissioning phase, we could only report the issues in writing to the general contractor; in the end, the matter was left unresolved, with the foreign owner being kept in the dark. However, we hope that the ESD system will not activate on its own throughout the entire lifecycle of the factory.
It’s impossible to do without an emergency shut-off valve, right? . .
Why not add a safety valve to the pipeline
Two in use and one as backup; venting is generally not necessary, unless there is a fault in this section of the pipeline
The situation at that time was that air started to flow in immediately; the design team had already been disbanded. The general contractor did not want to delay the commissioning timeline. Anyway, ESD activation occurs very rarely, and such mistakes are usually not detectable. Adding safety valves is definitely not a solution; what’s needed is an ESD vent valve to allow the system to be vented. This means drilling holes in the pipes for welding, purchasing ESD valves, connecting them to the venting system, and also modifying the control system to include this ESD vent valve (along with installing control wires). There are a whole series of issues involved, and it’s no longer possible to make any changes
No, what I mean is that when ESD is activated, during normal operations, it is possible to open one of the booster pump inlet valves in order to release the gas from the manifold
The ESD vent valve is used for emergency release; to achieve a complete evacuation, it is necessary to displace the gas with an inert gas. The displacement port should be located at the front of the treatment skid, after the shut-off valve there. At this time, the ESD vent valve should be in the closed position; the inlet valve of the booster and the vent valve should be opened respectively to discharge the gas
Yes, that’s how it’s done if replacement is needed
Is it possible to install an expansion safety valve that does not connect to the ESD system, but instead releases pressure to the air defense system when overpressure occurs? Starting operations isn’t a reason to leave safety hazards behind; it will be difficult to explain any problems that arise in the future
Installing a safety valve is one consideration, but full station venting after an ESD event is another issue. A safety valve ensures safety by enabling passive venting in the event of overpressure, yet high-pressure gas still remains in the pipelines. Venting after an ESD event is active venting, which releases all the gas remaining in the pipelines, ensuring that all combustible gases inside the station are vented to a pressure of 0. This is in line with the design principles of ESD; therefore, these are two different types of mechanisms
One can only hope that no emergencies will occur