In the 1980’s my late brother-in-law was working as an instrumentation technician at a new styrene plant being built in Texas. Toward the end of construction he said, “shouldn’t we be doing loop checks about now?”. They asked him what he meant and he explained that you go out into the field and stimulate or simulate the field device to send signals back to the control room to ensure everything is hooked together correctly and does what it is supposed to do. Also does the stuff in the field do what it is supposed to do when the control system tells it to? Do valves open when they are told to? Do they fail closed or open in the way they are supposed to when they lose air supply or control signal? They explained that they did not have to do this since the contractor had guaranteed they would hook everything up correctly.
He rather skeptically let them run with their misconception.
Fortunately, they had enough experience with styrene that they didn’t go live on day one. Styrene plants are one of the things that can go boom in the night. Or any at other time for that matter. So they started by running water through the lines, not product. Things didn’t happen even close to the way they should. My brother-in-law racked up a lot of overtime doing loop checks as the plant tried to play catch up with their start-up schedule.
My work at the refinery project changed from construction to loop checks towards the end of July. My construction skills are adequate and had been improving over the summer, but I have much more experience with troubleshooting and maintaining instruments than installing them. The way this site does loop checks the instrument technicians work pretty much alone in the field and communicates with the control room by radio. I rather like this as you work at your pace and are neither holding somebody up nor trying to drag a reluctant partner along depending on the circumstances.
In construction you work in pairs. I do miss having an apprentice to help train on instrumentation, but also feel they will be learning better hands-on construction skills being partnered with experienced journeymen that have mostly construction experience. When working with me they learn how to figure out how to do something neither of us knew how to do when assigned the task. It’s not bad experience to learn how to solve problems and learn quickly and that’s what they learn working with me, but working with a pure construction hand they learn how everybody typically does a particular type of installation.
I thought I had passed the stage of getting delight from solving problems and was in the season of looking for routine, but discovered that making something work that was not even close to working the way it was installed still gets my juices flowing and puts a spring in my step at the end of that day.
In 1977 the instructor stated that in thermocouples “the red wire is always negative and when you are checking them out you will find the electricians often connect the red wire to the positive terminal”. Still true in 2017.
All loop check work assignments and documentation are on iPads. In 1985 I was on a crew that was re-commissioning a paper machine that had been mothballed for the lean years of the early 80’s.
Assignments were more casual.
There was a handwritten list of things that had to be done stuck to the window of the door to the area instrument supervisor’s office. You would put your name next to an item to claim it and then sign off as it having been done when it was complete.
One of the Bert’s in the department (there were three I can remember, two since succumbed to the effects of age and disease) signed up to loop check a pneumatic instrument panel. He came back to the shop about an hour later and went to sign off as having completed the task. Half a dozen of us were in the shop and all challenged that possibility and wanted to know how he could have done it so quickly. He said, I turned on the air to the panel, put all the controllers at 50% output and walked around and looked. All the valves were at fifty percent open. He was satisfied. We explained that wasn’t necessarily good enough. He agreed to try it our way. Mobs have that effect on people.
By going one loop at a time he found some where the tubing had been changed and the controller wasn’t operating the valve it needed to. He found a few valves that had been changed out and were no longer going in the desired direction. That is why you do loop checks and do them one loop at a time.
