4th Class Power Engineering plant maintenance and inspection practice questions (4B).

Five free practice questions on plant maintenance and inspection: unit B5 of paper B (4B) of the 4th Class Power Engineer certificate exam, written to the SOPEEC syllabus. 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

1. Procedural · Describe the types and proper use of measuring tools

   The end of an operator's steel rule is worn and rounded. To measure the length of a pipe nipple accurately with this rule, the operator should

   1. measure from the 10 mm line and subtract 10 mm from the reading
   2. butt the worn end against a square held on the nipple and read directly
   3. read from the worn end, then add about 1 mm to make up for the wear
   4. measure on the inch scale along the other edge, then convert to millimetres
   Show the answer

   A. Correct. A worn end has lost the true zero, so the measurement is started at a clean graduation, such as the 10 mm line, and that amount is subtracted. The worn end is never used as the starting point.

   Why not the others

   B. A square gives a firm stop at the nipple's end, but the reading still starts from the worn end. With part of the end worn away, the graduations sit closer to the tip, so the reading comes out high. Start at a clean graduation, such as 10 mm, and subtract it.

   C. A rule worn short at its end reads high when measured from that end, because the first graduations now sit closer to the tip, so adding makes the error worse; and the wear is not known. Measure from the 10 mm line and subtract 10 mm.

   D. Both scales on a rule start from the same end, so the inch scale has lost its zero too, and converting adds a rounding step. Start from a clean graduation such as the 10 mm line and subtract it.

2. Recall · Discuss the correct use and limitations of wire cable and rope, including cable attachments and rope knots

   An operator inspecting a three-strand fibre hand line twists the strands open to look inside the rope. Which finding inside means the line must be taken out of service?

   1. Powdered and broken fibres between the strands
   2. Inner yarns that are brighter than the outer surface
   3. Strands that lie back snugly once released
   4. Light fuzz of raised fibres on the outside
   Show the answer

   A. Correct. Fine powder and broken fibres between the strands show internal wear, from grit or from the strands rubbing under load, which the outside does not reveal. Mildew, rot or chemical staining inside also condemn the line.

   Why not the others

   B. The inside of a rope is shielded from sunlight and dirt, so clean, bright inner yarns are a good sign. Powdered or broken fibres between the strands are what condemn it.

   C. Strands that return to their lay when released show the rope still has its structure. The finding that condemns a fibre rope is powdered, broken fibres inside it.

   D. A light, even fuzz on the surface comes with ordinary use. The inside of the rope is checked because internal wear, seen as powdered, broken fibres between the strands, can be severe while the outside looks fair.

3. Procedural · Describe ways of detecting firetube and tubesheet leaks

   A firetube boiler suspected of a leaking tube end has been cooled, drained and opened. Which test shows the leaking tube most directly, at the pressure the plant's procedure sets?

   1. Fill it to the normal water line, then look along the tubes through the manhole
   2. Fill it completely, pressurize it and watch the tube ends from the fireside
   3. Fire it at low load with the smoke box doors open, then watch for escaping steam
   4. Pressurize the empty shell with air, then listen for the leak at the stack outlet
   Show the answer

   B. Correct. A hydrostatic test with the boiler full to the top puts every tube and tube end under water pressure, and with the smoke box doors open the weeping joint can be seen at the tubesheet. Water, unlike air, stores little energy if something gives way.

   Why not the others

   A. Without pressure a small leak may not weep at all, and from inside the shell the tube ends in the tubesheets cannot be seen where they leak. Fill it full, pressurize it and watch the tube ends from the fireside.

   C. Firing with the gas passages open is unsafe, and flame and flue gas hide a small leak. The leak is found cold: fill the boiler full, apply hydrostatic pressure and watch the tube ends.

   D. Compressed air stores far more energy than water at the same pressure, and a hiss at the stack does not say which tube is leaking. A hydrostatic test, watched at the tube ends, finds it.

4. Recall · Describe the internal inspection of a boiler

   An internal inspection of a firetube boiler finds that the crown of the furnace has bulged down toward the fire, and the waterside there carries a thick, hard layer of scale. Why did the bulge form?

   1. Scale kept the water from cooling the metal
   2. The steam pressure rose above the safety valve setting
   3. The furnace grew longer than the shell and buckled
   4. The furnace plate was too thin for the pressure
   Show the answer

   A. Correct. Scale conducts heat poorly, so the furnace metal under it runs much hotter than metal wetted by water. Steel loses strength as it heats, and the boiler pressure acting on the outside of the furnace pushed the softened crown down into a bulge.

   Why not the others

   B. An overpressure acts on the whole boiler and would not single out the spot under the scale. A bulge where thick scale lies shows the metal overheated and lost strength at normal pressure.

   C. Differential expansion between furnace and shell is taken up by the furnace's corrugations and the end plates; it does not produce a local bulge under a scale deposit. The scale let the metal overheat.

   D. A furnace too thin for its pressure would have shown it in its pressure tests and in service from new. A bulge under a thick scale layer is the mark of metal overheating where water could not cool it.

5. Procedural · Describe the types and proper use of hand threading tools

   An operator is hand-tapping an M10 thread in a steel bracket for a new gauge mount. After a few turns, the tap wrench becomes noticeably harder to turn. What should the operator do?

   1. Take the tap out, then open the hole up with the next larger tap drill
   2. Fit a longer tap wrench, then keep turning with steady, even pressure
   3. Take the tap out, then finish the thread with the bottoming tap instead
   4. Reverse it half a turn to break the chip, then go on with cutting oil
   Show the answer

   D. Correct. Rising torque means chips are packing in the flutes. Reversing about half a turn every turn or so breaks the chips off and lets them clear, and cutting oil eases the cut in steel. Forcing a packed tap is how taps snap off in the hole.

   Why not the others

   A. A larger tap drill leaves shallower threads that strip more easily, and it does not touch the real cause, which is chips packing in the flutes. Backing the tap off about half a turn to break the chips, with cutting oil, cures it.

   B. More leverage hides the warning instead of removing its cause. The packed chips keep wedging the tap, and a longer wrench makes it easier to twist the brittle tap off in the hole. Back it off to break the chips, and use cutting oil.

   C. A bottoming tap has a very short lead and cuts more aggressively at the start, so in a partly cut, chip-packed hole it binds even harder. The problem is chip packing: back the tap off to break the chips and use cutting oil.

02Answer key

03What unit B5 covers

Maintenance in the powerhouse: safe use of hand tools, threading, measuring and layout tools, grinders and drills, ladders and scaffolds, rigging and hoisting, rope and fasteners, servicing packaged firetube and cast-iron boilers, finding and replacing leaking firetubes, preparing a boiler for inspection, and mechanical and chemical boiler cleaning.

Part B of the SOPEEC 4th Class syllabus names this unit “B5 Power Plant/Heating Plant Maintenance” and lists four objectives under it (objectives 18 to 21 of 52). SOPEEC does not publish how many exam questions come from each unit, and neither do the ABSA, Technical Safety BC, TSASK or TSSA pages we checked. The right-hand column is how many questions our bank holds on each objective, Standard and Advanced together, not a count from the exam.

04What the questions turn on

Flatter slings carry more

On a symmetric two-leg bridle each leg carries the load's weight divided by twice the sine of its angle above the horizontal. The flatter the legs, the higher the tension, so the sling rating sets a minimum angle and with it a minimum headroom above the lugs.

Rated points, safe ladders, landed loads

A hoist hangs from a rated lifting beam or gantry, never from a steam main and its hangers. An extension ladder's feet go out a quarter of its working length. A load is not left hanging overnight: it is landed on blocking and the hoist slackened off.

Preparing for the inspector

A boiler is cooled slowly before it is drained, because emptying it hot bakes the sludge onto the surfaces. The waterside and the fireside are both opened and cleaned: soot and ash left in the flues and furnace hide the metal the inspector has come to see.

What the inspection finds

Small deep pits under reddish-black caps near the feedwater inlet point to dissolved oxygen. A furnace crown bulged toward the fire under thick scale shows overheated metal. Rising make-up, a falling sulphite residual and wet soot at the rear tubesheet point to a leaking tube end.

05The other units

Paper 4B has twelve units, B1 to B12. Each has its own page of free questions:

The 4th Class Power Engineering practice exam (4B) page describes the full question bank; paper A has its own 4A practice exam. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.