Five free practice questions on commissioning and start-up: block G of the Red Seal 307A Steamfitter/Pipefitter exam, about 11 of its 130 questions. They are in the exam's format: four options, one correct answer. Answer each one before opening the explanation. No account, no email.
01The questions
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A long new transfer line at a refinery will be cleaned by pushing a foam or brush cleaning pig through it with the flushing medium. What is set up at the start and the finish of the run?
- A temporary strainer at the start and a target plate at the finish
- A pig launcher at the start and a pig receiver at the finish
- A spectacle blind at the start and a drip leg at the finish
- A check valve at the start and a vacuum breaker at the finish
Show the answer
B. Correct. The RSOS lists setting up pigging devices, launchers and receivers for cleaning pipe. The pig is loaded into the launcher barrel, driven through the line by the flushing medium, and caught in the receiver barrel, which is isolated and depressurized before it is opened.
Why not the others
A. A strainer catches debris in a flowing system and a target plate is the acceptance check for a steam blow. Neither can put a pig into the line or catch it safely at the end.
C. A spectacle blind is a positive isolation device and a drip leg collects condensate on steam mains. A pig needs a launcher barrel to be loaded and a receiver barrel to be recovered.
D. A check valve prevents reverse flow and a vacuum breaker admits air to let equipment drain. Neither handles a pig, which is loaded in a launcher and caught in a receiver.
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A new spiral-wound gasket has been fitted in a leaking Class 300 flange on an oil-sands plant hydrocarbon line. How are the lubricated studs tightened to the torque sheet value?
- Star pattern, each bolt taken to full torque on the first pass
- One side fully tightened first, then the opposite side to match
- Clockwise around the flange, each bolt to full torque in one pass
- Star pattern in stages to the torque sheet, then a circular pass
Show the answer
D. Correct. Bolts are drawn up in a star (crisscross) pattern in stages, typically about 30 %, 60 % and 100 % of the torque-sheet value, then a final circular pass at full torque catches bolts that relaxed. This keeps the faces parallel and loads the gasket evenly; the torque values are recorded.
Why not the others
A. The pattern is right but the single pass is not: the first bolts pulled to full torque pinch the gasket before the rest are snug, leaving uneven load. Torque is applied in stages.
B. Tightening one side first pulls the flange faces out of parallel and pinches the gasket unevenly. Load is built up evenly around the flange in a crisscross pattern.
C. Taking each bolt to full torque in turn around the circle cocks the flange faces, crushing the gasket on one side and leaving it loose on the other, so the joint leaks again.
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Variable-spring hangers on a new refinery hot-oil line were installed with their travel stops in place and left locked through the hydrostatic test. What is done at the pre-check before the line is heated?
- Remove the travel stops and confirm the cold-load setting
- Leave the stops in so the hangers cannot move as the line heats
- Remove the stops after the line reaches operating temperature
- Replace the spring hangers with rigid rods now testing is done
Show the answer
A. Correct. Travel stops lock the spring so it can carry the weight of test water without bottoming out. Before operation they are removed so the hanger can follow the line's thermal movement, and each load indicator is checked against its cold setting on the hanger schedule. Supports and anchors are part of the RSOS pre-check conditions.
Why not the others
B. A locked spring hanger acts as a rigid support. As the line grows with heat it cannot follow the movement, overloading the pipe, the hanger and the equipment nozzles. The stops come out before start-up.
C. Heating the line with the stops in place overloads the supports and nozzles during warm-up. The stops are removed at the pre-check, before heat is applied, once the test water is out.
D. Spring hangers are specified because the line moves vertically with temperature; rigid rods would defeat the design. Only the temporary travel stops are removed.
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A calibrated commissioning gauge will be used to confirm that a food plant's new compressed-air header reaches its 100 psig (690 kPa) operating pressure. Which full-scale range suits it best?
- 0–60 psig
- 0–1000 psig
- 0–200 psig
- 0–100 psig
Show the answer
C. Correct. At 100 psig the needle sits near the middle of a 0–200 psig dial, where the gauge is most accurate and has room for overshoot. The common rule is a full-scale range of about 1.5 to 4 times the pressure being read, with a current calibration check before use.
Why not the others
A. A 0–60 psig gauge would be driven past full scale at 100 psig, which damages the Bourdon tube and gives no reading. The gauge range must be well above the pressure being read.
B. At 100 psig the needle would sit at one-tenth of the scale, where each graduation is too coarse to read the pressure accurately. The range is far larger than needed.
D. A gauge read at full scale is at its least accurate and least safe point, and any overshoot pegs it. Choose a range that puts the working pressure near mid-scale.
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A school's new steel heating-water piping has been flushed and is now to be chemically cleaned per the treatment specialist's procedure. Which order is correct?
- Refill and add inhibitor, then clean once the system is running
- Clean, drain and rinse to neutral, then refill and add inhibitor
- Clean, then leave the cleaner in to act as the operating treatment
- Add inhibitor, then clean, then drain and rinse before refilling
Show the answer
B. Correct. The cleaner (degreaser or pre-operational cleaner) is circulated for the time, temperature and pressure the chemical engineer specifies, then drained to an approved disposal route and the system rinsed until the water tests neutral. Only then is it refilled and dosed with the operating inhibitor, pH control or oxygen scavenger, with levels signed off.
Why not the others
A. Cleaning a system that is already in operation with inhibitor in it skips the whole pre-operational clean. Oil, flux and mill scale stay in the piping and the inhibitor is wasted on dirt.
C. Pre-operational cleaners are aggressive and are designed to be drained and rinsed out; left in, they can attack gaskets and metal. The operating treatment is a separate inhibitor dosed after rinsing.
D. Inhibitor added first would be consumed by the dirty system and then drained away with the cleaner. The operating treatment goes in last, after the cleaning and rinsing.
02Answer key
| Question | Answer | Sub-task |
|---|---|---|
| Q1 | B | Flushes system |
| Q2 | D | Corrects faulty conditions |
| Q3 | A | Pre-checks system for commissioning |
| Q4 | C | Selects and connects commissioning equipment |
| Q5 | B | Chemically treats system |
03What block G covers
This block covers getting a finished system ready and handing it over. It includes flushing, steam blows, pigging and chemical cleaning, passivation, pre-check walkdowns, test blind lists and spring hanger stops, filling and venting, raising pressure to operating, finding and fixing leaks, pump rotation checks, balancing, pipe markings and valve tags, weld maps and the turnover package.
The Red Seal Occupational Standard names this block “Performs commissioning, start-up and turnover”. It carries 8.5% of the exam, about 11 of the 130 questions, split across two tasks. The share column is each task's weight within the block, as the standard publishes it.
| Task and its sub-tasks | Share of block |
|---|---|
| Prepares system for commissioning, start-up and turnover Flushes system; Chemically treats system; Pre-checks system for commissioning; Selects and connects commissioning equipment | 55% |
| Commissions systems Secures commissioning area; Pressurizes system; Inspects system; Corrects faulty conditions; Participates in start-up and turnover procedures | 45% |
04What the questions turn on
Flush fast enough to carry debris
Every part of the system must reach the specified flushing velocity, or heavy slag settles where flow is slow and moves later. Coils, control valves and pumps are bypassed with temporary jumpers so the flush cannot damage them.
Account for every temporary item
Before filling, every test blind on the list is removed and signed off, spring hanger travel stops are pulled and cold settings checked, and relief valves, gauges and control valves removed for the test are reinstated.
Low head, low flow, low amps
A centrifugal pump turning backward still moves some water, but with low discharge pressure, low flow and low motor current. Swapping two of the three phase leads reverses it, which is why rotation is bump-tested at the pre-check.
Fill low, vent high
Fill from the low point with the drains closed, venting at the high points until solid water appears. When draining, open the high-point vents as well as the drains, or the risers pull a vacuum and drain slowly.
05The other blocks
The 307A exam has seven blocks. Each has its own page of free questions:
The 307A Steamfitter/Pipefitter practice exam page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.