ESD Input


Thread Starter



LT ESD input which trip the pump at LALL.


If the LT become open circuit (like knife switch accidentally opened or etc.), it will trip the pump or not?
Hi there,

Yes it will definitely trip the pump if it's output is configured to do so and in this case in most probably is since it is a level application. You need to have a look in the ESD Cause and Effects matrix what the action will be of the LT. It might be configured to give only a alarm so I cannot tell you that, but a action will definitely be initiated if the transmitter goes open circuit.

On top of the alarms and trips that will be happening you still going to get your boss and production on your back as well for not following the laid down safety procedures for the ESD system. Getting fired for something like this is not out of the question either since you are seen as a threat to the safety of others on the plant if you caused something like this. They will also not accept ignorance as a excuse since it is your responsibility to make 110% sure you know what you are doing before you do it. 100% only means I think this is how it will work.

The level trip and alarm settings are based on this analog input. You can see the alarm and trip settings on the LT face plate in the CCR. If the level goes low the ESD will take action as per the alarm and trip setting so it will already start it's action the moment the level indication goes lower than the LALL setting.

Open circuit will give a 3,5mA signal to the ESD so this is obviously lower than the level alarm and trip settings.

If you need to work on the transmitter or disconnect it, you need to apply a inhibit on the Tx's output in the ESD system, so the ESD system will not initiate a trip or start a shut down sequence.
CCR will normally do this inhibit for you if you have all the paperwork and permissions and signatures from the bosses. SSIC (Safety system isolation cert)
Hello Sam

Thanks a lot. I am thinking about the accident that the circuit could be open unintentionally, in that case process is still normal but once it become open circuit it will trip the pump as you explained (if it is so).

I mean accident is not being considered? like it will give alarm first that the circuit is open then they can fix it?
Hi again,

Yes I see your point but with the ESD it is like the wild west shoot first and ask questions later. Afterwords you will see the ESD level indication is red indicating a open circuit so that helps with fault finding later. The F&G have this facility to indicate window fault or open circuit since the detector will only activate with 17mA
Hi Sam

Is the open circuit usually happen in the operating plant? (by means of loss connection, etc.)

because if it is so, if the previous example could shutdown the plant and then it goes to open circuit... then they gonna lost a lot of million dollars?
Hi again,

Why do think I stressed so much in my first reply about you doing something on the ESD system without the proper authorization and inhibits.

It hardly ever happen and I have personally in all my years only experienced it once, and that was when a cable shave through on a sharp edge on a S/S cable rack. That was very difficult to find but that was what happened. So the action after that was that all cable racks were checked to make sure this kind of thing does not happen again.

Since we knew there was no real emergency we just inhibited the transmitter and restart the plant while the technicians start searching for the fault, so there is no need or reason for millions of dollars losses as you described, even in a situation like this. You are not going to stop your car and start walking, just because the ref counter in your car all of a sudden stop working, are you?
The operators are also very experienced and will know to keep on monitoring the DCS transmitter since the ESD is out of commission, and will take manual action should anything go wrong.
Thanks Sam.

Please be patient on me, i'm just a little kid in this industry. No experience in operating plant. Came from EPC. ^_^
Hi again,

No worries man. Nobody knows it all and I am sure you will be able to tell us much about EPC since I know little again in that area.

Don't ever apologize for asking since the person that ask questions and who is working with a manual next to him in the plant is someone I would like to have on my plant and not the person that think he knows and then just do things without asking first or do some double checking in a manual first.