Finding the right kind of pressure monitor

bradyle

Ok so I want to be able to measure the pressure at the bottom of a vessel at work. I need to be able to see the max pressure reached however ideally I’d like to see how the pressure changes throughout the process. Seems easy right…sadly not!

It’s a pressure vessel and for various reasons it’s not possible to put any more holes into the vessels walls. So I need this to be wireless. It also needs to be able to withstand being fully submerged in a resin. It should in theory be seeing pressure of 100+ bar for 2 hours and will have to withstand being under vacuum for 1 hour (I don’t necessarily need to record the values during the vacuum stage but would be pretty nice).

Does anything like this exist? In my head I want a normal pressure transducer that goes to a small sealed computer thing that records the pressures throughout the process. I’d then be able to hook up the little computer thing to my system and download the information. To me this doesn’t seem that complicated but I cant seem to find anything like it. I don’t know if I’m just using the wrong terminology to search for or if in reality this is very complicated and I’m being stupid!

Any help would be very much appreciated!!!

2011

You need to provide far more information.

I assume that your plan is to connect a pressure transmitter to a PLC (or some sort of control system) and to be able to view trends on a HMI.
Is that correct?

Why wireless?

Are you saying that there are no available process connections on the pressure vessel?

bradyle

I just want to run a trial to check to see what the actual pressure is in the vessel compared to what in theory it should be. It wont be a permanent thing.

Yea there is no available connections on the pressure vessel and because we've lost the material sheet for the vessel it's not possible to get any more added.

I have been looking at submersible pressure loggers which seem to just record the pressure they experience over a length of time which i think would suit. Sadly though most see to only go to around 5 bar.

2011

bradyle wrote: »

Yea there is no available connections on the pressure vessel and because we've lost the material sheet for the vessel it's not possible to get any more added.

Are there any lines connected to the vessel? If so perhaps a process connection can be made available on one of these lines that is exposed to the same pressures as the vessel? Have you a P & ID showing the vessel ?

I have been looking at submersible pressure loggers which seem to just record the pressure they experience over a length of time which i think would suit. Sadly though most see to only go to around 5 bar.

This would be quite an unusual approach in my opinion.

It would not be difficult to find a pressure transmitter that can measure in excess 100 BarG with +/- 1% accuracy from someone such as Endress + Hauser. These units generally provide a 4 to 20 mA signal to a PLC or if there is no control system they can simply show the output on a head mounted LCD display. Values can be recorded manually and a graph can be plotted in Excel if it just a one off.

Doc_Savage

i was thinking using a strain gauge bonded to the outside of the vessel and relating it's output (resistance?) to the pressure inside.

this requires calibrating and a bit of maths, or if you had the data sheet for the vessel then you could work out a theoretical pressure and avoid calibration at the expense of accuracy.

2011

Personally I would buy something like a Endress & Hauser Cerabar S PMP75 pressure transmitter.

Similar cheaper units can be purchased from Krohne.

This can provide a 4 to 20mA (analog) output that is directly proportional to the pressure. The maths required is far more straightforward (y = mx + c).

bradyle

I can't see into the vessel it's completely enclosed so I can't use a gauge or anything for recording measurement. There are no inlets or outlets for wires and because I don't have any data sheets for the vessel I cant make any so I can't connect it to a PLC of any kind. The vessel is very old and isn't connected to any sort of PLC at the moment. It's all done manually and there are no checks in place to make sure the required pressure is being met. This is why I'm doing the trial to check if it is so that if it's not I can try and get a more modern vessel.

The strain gauge is an interesting idea, but the vessel's walls are very thick so I don't know if you will be able to see the pressure by applying it there.

I am going to go with a pressure logger that I can just place in the bottom basket of the vessel and it will record all the pressure values during the cycle. I can then just hook it up to my computer and download them. I have found a few that are capable of withstanding the pressure so I think it might be ok

2011

Is there not an inlet or outlet pipe to the vessel??

Doc_Savage

^^^
exactly, more detail please, i was just trying to give a starting point idea, 2011 seems to know a lot more on the subject than me, more detail means clearer answer, quicker.