DR uses a seal in as they call it (often preferred to set/rest but basically the same), the one problem I see with DR logic is probably a mis-interpretation of the way the existing system works, I think the pump has to be started initially & the manual start/stop is not just manual mode as they have no man/auto selection (or that is how it appears, however, without seeing all the logic cannot be sure), so in DR's code, if started using the top rung it is assumed this is manual control so the low level timer will not stop the pump as the pump is controlled by what he calls override (Ored round the low level condition).
The code I produced assumes (I think correctly) that the operator starts (or rather enables) the pump, this is then controlled by the level in the tank, so My logic is if you like start process (enable pump to run) if low level is reached, it stops the pump, as it has already been enabled (Started) it will re-start when the low level gets covered (including delays to prevent hunting), no idea how the process deals with low level is it automatic re-fill ? or does the operator have to top it up ?.
Without the complete description on how this system is operated then we can only guess, from what I have seen, the process is a bit iffy, the original code seems messy, probably little alarm handling, certainly not to a standard I would expect from a process.
I'm not directly knocking the original coder, we don't know the process/design & usual factors we have faced ourselves when a production manager is breathing down your neck.
From what I gather (with little information) this is a buffer tank for cooling water, this is fed through some kind of cooling system to cool something ? we do not know if this is a loss system i.e. water is passed through a possible jacket to cool & then dumped to drain (in this mode would require an auto top up system) or is it returned to the buffer tank possibly through a heat exchanger to cool it back down again.
What worries me is that without knowing completely this part of the process we could be barking up the wrong tree.
I would suggest to Mas01, if reliable answers are required he describes that part of the process in detail, I know he has restrictions on what he can disclose of the process, but this is not rocket science and unlikely to be use to others, as an experienced systems engineer I have done many different types of control so unlikely to be something that myself or many others have not done before.
The code I produced assumes (I think correctly) that the operator starts (or rather enables) the pump, this is then controlled by the level in the tank, so My logic is if you like start process (enable pump to run) if low level is reached, it stops the pump, as it has already been enabled (Started) it will re-start when the low level gets covered (including delays to prevent hunting), no idea how the process deals with low level is it automatic re-fill ? or does the operator have to top it up ?.
Without the complete description on how this system is operated then we can only guess, from what I have seen, the process is a bit iffy, the original code seems messy, probably little alarm handling, certainly not to a standard I would expect from a process.
I'm not directly knocking the original coder, we don't know the process/design & usual factors we have faced ourselves when a production manager is breathing down your neck.
From what I gather (with little information) this is a buffer tank for cooling water, this is fed through some kind of cooling system to cool something ? we do not know if this is a loss system i.e. water is passed through a possible jacket to cool & then dumped to drain (in this mode would require an auto top up system) or is it returned to the buffer tank possibly through a heat exchanger to cool it back down again.
What worries me is that without knowing completely this part of the process we could be barking up the wrong tree.
I would suggest to Mas01, if reliable answers are required he describes that part of the process in detail, I know he has restrictions on what he can disclose of the process, but this is not rocket science and unlikely to be use to others, as an experienced systems engineer I have done many different types of control so unlikely to be something that myself or many others have not done before.