I am modelling a system with an existing relief valve set to discharge when a system reaches pressure of >700kPa. Advice from the supplier is that the valve could take 10 seconds to open and 60 seconds to close - so for the first time I am trying the new time-based SRV functionality.
The model results look surprising to me though, and I just want to test my understanding of how this is modelled. It seems as though once the valve is triggered to open, it has to go through the full cycle of opening and closing regardless of the actual system conditions? For example, the valve closure cannot be interrupted if, in the meantime, the pressure rises above 700 kPa once again - rather, once it has closed over 30 seconds, it can then start opening again. Do I have this correct?
Ideally, I would want to set the valve with Kv/Cv curve, 'time to fully open' and 'time to fully close' and then let it respond to the actual conditions. Is there a way to do this?
Thanks, Liz
Hello Liz,
A Surge Relief Valve (SRV) should close immediately after pressure drops below the threshold specified. With the CONNECT Edition Update 3 of HAMMER you do have time based control where you specify the opening and closing times.
lizh said:The model results look surprising to me though, and I just want to test my understanding of how this is modelled. It seems as though once the valve is triggered to open, it has to go through the full cycle of opening and closing regardless of the actual system conditions? For example, the valve closure cannot be interrupted if, in the meantime, the pressure rises above 700 kPa once again - rather, once it has closed over 30 seconds, it can then start opening again. Do I have this correct?
Can you provide your model or a simplified version of your model where we can see this? Please share the model files as per this article.
Alternatively, have you tried using a TCV with a D2A connected to it? The TCV could give more functionality and control in such cases. See this article for reference: Modeling Reference - Valve Closure
For reference please also go through this article in case you haven't already: Modeling Reference - Surge Valves
Let me know if this helps.
Regards,
Yashodhan Joshi
We confirmed with the developers that the surge valve is working as expected, with no interrupted operation allowed during the calculation. A note on this was added to the surge valve wiki article for clarification. Yashodhan's recommendation in the earlier post may work as a workaround. We can review the possibility of including a feature like this in a future version of HAMMER.
Scott
Thanks both. I will go back to the method of using TCV based on observed behaviour in model iterations, as I need the valve to respond more dynamically. Advice from manufacturer has been that, in reality, there is no need for the valve to fully close before it can start to open again, if that's what pressure conditions dictate.
Regards, Liz
A feature request for this has been filed. The reference number is 906159. The development team will review this for inclusion in a future release of HAMMER.