assignment 3

Joshua Turner14 EliUnit 24 Process measurement Assignment 3Task 1 (P8 and M3)

Scenario:

I have been contacted and requested to work on vessel V401 and calibrate two DP cells, a pneumatic and electronic cell. I have been asked to make sure that the vessel loops accurately measure the level inside of the vessel.

a) Documentation that I will need

I will need 3 pieces of documentation to be able to complete this job, they are listed below; (See appendix 1)

Instrument loop sheets Instrument details Calibration details of both DP cells

I would also need the rig 400 instrument settings (See appendix 2) and blank calibration sheets which would be filled in as I make my way through the calibrations (See appendix 3).

b) The DP cells that I will be calibrating are:

An electronic DP cell

Rosemount – Serial No. E120119

Calibration range – 0 –150” WG

Output – 4 – 20 mA (supply 12-45V DC)

Maximum working pressure – 2000 psig

A pneumatic DP cell

Foxborro – 13A – MS2

Serial Number – E253500

Output – 3 – 15 PSI

Range – 0 – 150” WG

Maximum working pressure – 1500 psig

316SS capsule (Stainless steel)

c) Health and Safety requirements


I need to undertake some necessary actions to make sure that the correct safety precautions are in place, first of all I need to make sure that I acquire a work permit from my supervisor(See appendix 4); this will inform me of the conditions I will be working in and the PPE that I will have to wear. The PPE is listed below:

Overalls – Used to stop any oils/chemical or grease getting on my clothes Boots – To protect my feet from anything being dropped on them such as the DP cell Gloves – To stop me from cutting my hands LEP – If there is any burst of air from the psi then I would need to protect my

eyes.

(As you can see from the photo (right) this is me in full correct PPE)

Another health and safety precaution would be to make sure that you isolate the loops correctly; the isolations that should take place are an electrical isolation which is lifting the knife edges for that loop within the control room. For the pneumatic isolation, you would have to turn the supply of air off by turning a lever at a point across the loop/system. The process lines must also be safely isolated as they could contain trapped air.

d) Equipment

The equipment that could be used for the calibrations would be:

Test bench comparator: This is made up of the following,

30 psi 0 – 100”WG regulated air – I will connect this up to the high pressure side of the DP cell and pump pressure into the instrument.

30 psi supply – I will connect the DP cell input to the supply. “WG digital indicator – This is used to show a reading when the

pressure is pumped into the DP cell via the regulated 0-30 psi / 0-100”WG supply.

30 psig gauge – This piece of equipment is used to measure the 3-15 psi output pumped from the DP cell, it will also indicate to me is the

span/range needs adjusting. 24 volt DC supply – Is used to provide a voltage to the system when connected up.

Druck DPI 601 portable calibrator: The Druck is used on site to provide the pressure to the DP cell.

Range 0–2 bar, 0-30 psig, 0-800”WG; I can use the 0-800”WG range. Serial number 5996/91/10


Multi-meter, Mastech Mas 830BC: This is used to give an indication of voltage, current and resistance. I can connect it up in series with the 24 volt DC suply to the electronic cell.

Serial number MBED021531

I could have gone onto the site and completed the job out there, or I could have disconnected the DP cell and took it back to the workshop and calibrate it in there. I have decided to go for the latter of the 2.

e) Why I decided to use certain equipment

As I have stated in task 1e, I have decided to calibrate the DP cell back in the workshop, I came to this decision for numerous reasons. First of all, taking environmental conditions into consideration I believe that progression would be made at a much quicker rate within the workshop if the weather was poor. It is warmer in the workshop than out on the site which would mean that the job would be completed at a higher level of competency as some people may rush the job on site if they were working in bad conditions, if the weather, for example, was rainy, then a problem that I would have to solve would be the open cover of the DP cell and all of the electrical interior of the DP cell being covered in rain. Secondly, if I were to calibrate the DP cell in the workshop then I would only have to isolate the loop once, whereas if I was to complete the calibration on site, I would have to make a total of 3 isolations of the loop for different reasons. Moving on from this, I would have to carry out different pieces of equipment such as a Druck and a multi-meter; this would lead to complications out on site because I would have to hook the Druck up to the DP cell and pump pressure into the DP cell along with using a multi-meter and trying to fill out a calibration sheet. Having a work bench also means that it is a better place to fill in the calibration sheet, the results would be set out a lot neater on the sheet than what they would be if I had to fill the sheet out on site. I also believe that another logical reason for calibrating the DP cell would be that I would not have to constantly pump the Druck to insert pressure into the DP cell, instead of that, all I would have to do is turn up the regulator on the test bench comparator to the amount of pressure that I want. Finally, the Druck is sometimes considered as unreliable because they can leak, an issue that arises with this is that I would be pumping pressure from the Druck into the DP cell but the pressure would be decreasing due to the leak.


Task 2 – P9

A) To calibrate the pneumatic DP cell I completed the following steps:

Step 1) I began by gathering a work permit and having it signed off by my supervisor.

Step 2) In my full and correct PPE, I went onto the site and located the correct pneumatic DP cell that I would be working on.

Step 3) I isolated the loop that the DP cell was located in; to do this I used a loop drawing.

Step 4) After the isolation, I removed the DP cell from the site and took it back to the workshop.

Step 5) Next I securely mounted the DP cell to the workshop bench so that it would not possibly fall and hit my feet.

Step 6) I then connected up the DP cell to a 20 psi supply as this would supply the input onto the DP cell

Step 7) After that, I connected a 3-15 psi output to a gauge that read 0-30 psi on the comparator panel on the workbench.

Step 8) I then connected a regulated 0-50”WG air supply to the high pressure side of the DP cell.

Step 9) I applied 0” of water to the high pressure side of the of the DP cell

Step 10) I had to make sure that there was a 3 psi output, to do this; I adjusted the zero screw on the DP cell.

Step 11) I applied 50”WG to the high pressure side of the DP cell.

Step 12) I also adjusted the range screw so I could get a 15 psi output

Step 13) I had to make sure that the readings were spot on, the way I could confidently prove this was to repeat steps 10 and 12 until the readings were accurate.

Step 14) I had to record the results so to do this I used a calibration sheet.

Step 15) The final step that I completed was to disconnect the cell from the workshop and take it back out onto site, refit the DP cell to V401 and re-commission it.


B) To calibrate the electronic DP cell I completed the following steps:

Step 1) I began by gathering a work permit and having it signed off by my supervisor.

Step 2) In my full and correct PPE, I went onto the site and located the correct electronic DP cell that I would be working on.

Step 3) Next, I isolated the loop by lifting the knife edges in reference to the DP cell.

Step 4) I then safely removed the electronic DP cell and took it back to the workshop to calibrate it.

Step 5) I made sure that the DP cell was secured on the test bench; this complied with health and safety because now it could not fall of the bench on possibly onto my feet.

Step 6) I connected the DP cell up to a 24 volt supply and mA in series.

Step 7) When the DP cell was correctly connected up; I applied 0 pressures to the DP cell and adjusted the 0 to give me a reading of 4mA on the digital screen.

Step 8) Next I applied a total of 50”WG to the cell and adjusted the range screw until I had a reading of 20mA.

Step 9) Before I move on to any other steps, I had to make sure that the 4 to 20 mA was spot on, to make sure of this I would keep repeating steps 7 and 8 until readings were accurate.

Step 10) I then recorded my results and to do this I filled in a calibration sheet.

Step 11) At this stage, I disconnected everything from the DP cell, took the DP cell back out on to the site and re-commissioned it.


C) Proof of calibrations (Photographic evidence)

D) My tutor completed an observation report on me (Appendix 5)

Task 3: Distinction 2

a) On completion of tasks 1 and 2, you should attach the calibration record sheets for the level system calibration and evaluate the data to determine the overall system error performance.

After I had undertook and completed the calibration I filled in 2 calibration sheets; one for the pneumatic DP cell and one for the electronic DP cell.

The details of the Electronic DP cell as are follows:

Make: Rosemount

Serial Number: E120119

As I went back over the sheets and analysed them, I found a slight zero error and there was also an error at 100% (rising) of 0.01 mA and this can also be seen as a 0.06% error, this happened when I applied a total of 50”WG, the digital screen was showing 20.01 mA instead of 20mA. I attempted to adjust the range; however I could not get this spot on and therefore settled for the extra 0.1 mA. Although I was certain that this reading was well within the tolerance, I showed the results to my supervisor who was also fine with them.

The other calibration that I undertook was of a pneumatic DP cell, the details of this are as follows:

Make: Foxborro

shows me calibrating an electronic DP cell.

This is an image of me removing the DP cells off the site.


Serial Number: E253500

After I had filled in the calibration sheet with my results, I then went back over them and look to see if I could spot any errors; I found one error at 50% (rising); it should have been 9 psig, however the reading I gathered was 9.1 psig which had a percentage error of 0.83%. This difference was only small and as I did with the electronic DP cell error, I checked it with my supervisor to make sure he thought it was acceptable. Due to this DP cell only having a zero and span adjustment screw it meant that I could not fix this error.

b) Found at the back of my assignment will be the calibration sheets that I filled in when I completed the calibration of the pneumatic and electronic DP cells. I have also provided evidence of me undertaking the calibrations and these photos can be found within tasks 1 and 2.

assignment 3

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