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Red Seal Millwright practice questions

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Question 1Common Occupational Skills (safety, tools, communication, documentation)

Before shutting down a machine for scheduled maintenance, what should the millwright do first?

  1. Remove the machine guards
  2. Apply a personal lock
  3. Test the start circuit
  4. Notify affected workers Correct answer.

Explanation

Lockout begins with preparation: everyone who works on or near the equipment must be told the machine is going down so they can protect their own tasks and equipment. Only after the machine is stopped and energy is isolated do locks, stored-energy release and verification follow.

Question 2Common Occupational Skills (safety, tools, communication, documentation)

What eye and face protection is required when using a bench grinder?

  1. Safety glasses alone
  2. Safety glasses plus a face shield Correct answer.
  3. A face shield alone
  4. No protection if the guard is adjusted

Explanation

Grinding throws sparks, grit and wheel fragments at high speed, so a face shield protects the face while safety glasses protect the eyes from particles that pass around the shield. Both are worn at the same time.

Question 3Common Occupational Skills (safety, tools, communication, documentation)

What does a WHMIS pictogram on a product label communicate?

  1. The hazard class of the product Correct answer.
  2. The shelf life of the product
  3. The manufacturer's contact details
  4. The required disposal method

Explanation

WHMIS pictograms are hazard symbols that identify the class of hazard, such as flammable, corrosive or acutely toxic. The label also carries the product identifier, supplier information and precautionary statements.

Question 4Common Occupational Skills (safety, tools, communication, documentation)

A hammer handle is found to be cracked. What is the correct action?

  1. Marked and sent to the tool crib for repair
  2. Used only for light duty work
  3. Wrapped with tape and kept in service
  4. Taken out of service and replaced Correct answer.

Explanation

A cracked handle can fail without warning and let the head fly off, so the tool must be removed from service immediately. Wood handles cannot be safely restored by taping, gluing or restricting the tool to light work.

Question 5Common Occupational Skills (safety, tools, communication, documentation)

Which class of fire extinguisher is designed for flammable liquid fires?

  1. Class B Correct answer.
  2. Class C
  3. Class D
  4. Class A

Explanation

Classes are assigned by the fuel involved: A for ordinary combustibles, B for flammable liquids and gases, C for energized electrical equipment and D for combustible metals. A flammable liquid fire therefore calls for a Class B extinguisher.

Question 6Common Occupational Skills (safety, tools, communication, documentation)

For every 4 m of working height, how far from the wall should the base of a ladder be placed?

  1. 1 m Correct answer.
  2. 2 m
  3. 0.5 m
  4. 1.5 m

Explanation

The 4:1 rule sets a ladder at roughly 75 degrees, which balances the risk of tipping backward against the risk of the base sliding out. One metre out for every four metres of height satisfies that ratio.

Question 7Common Occupational Skills (safety, tools, communication, documentation)

A container of lubricating oil tips over and spills on the shop floor. What is the first action?

  1. Hose the area down to the floor drain
  2. Continue working and clean it up at the end of the shift
  3. Block off the area and absorb the spill Correct answer.
  4. Cover the spill with cardboard

Explanation

The spill must be contained and the area made safe before anyone walks through it, so the immediate step is to barricade the slick and absorb the oil with suitable material. Oil washed into a drain becomes an environmental release, and delaying cleanup leaves a slip hazard in place.

Question 8Common Occupational Skills (safety, tools, communication, documentation)

At what daily noise exposure level does hearing protection generally become mandatory in Canadian workplaces?

  1. 85 dBA Correct answer.
  2. 75 dBA
  3. 65 dBA
  4. 80 dBA

Explanation

Most Canadian jurisdictions set an 8-hour exposure limit of 85 dBA, at which hearing protection and a hearing conservation program are required. Exposure is averaged over the shift, so short loud periods are weighted against quieter periods.

Question 9Common Occupational Skills (safety, tools, communication, documentation)

How should a click-type torque wrench be stored after use?

  1. At the setting last used
  2. At its highest scale setting
  3. At its lowest scale setting Correct answer.
  4. With the handle clamped in a bench vise

Explanation

Leaving a click-type wrench wound up keeps the internal spring compressed, which gradually changes its release point. Backing the adjustment off to the lowest setting removes that load and preserves calibration.

Question 10Common Occupational Skills (safety, tools, communication, documentation)

A metric micrometer shows 7 mm on the barrel sleeve and the 22nd division on the thimble aligned with the reference line. What is the reading?

  1. 7.72 mm
  2. 7.22 mm Correct answer.
  3. 7.022 mm
  4. 8.22 mm

Explanation

The sleeve gives whole millimetres and the thimble gives hundredths of a millimetre, so each thimble division counts 0.01 mm. Adding 7 mm to 22 hundredths gives 7.22 mm.

Question 11Common Occupational Skills (safety, tools, communication, documentation)

A vernier caliper with a least count of 0.02 mm shows the main scale just past 24 mm, and the 7th vernier line coincides with a main scale line. What is the reading?

  1. 24.20 mm
  2. 24.07 mm
  3. 24.14 mm Correct answer.
  4. 24.70 mm

Explanation

The main scale supplies the whole millimetre value and the vernier supplies the decimal part, obtained by multiplying the coinciding line number by the least count. Seven lines times 0.02 mm equals 0.14 mm, giving 24.14 mm.

Question 12Common Occupational Skills (safety, tools, communication, documentation)

A dial indicator mounted on a magnetic base with its plunger against a shaft is normally used to check which condition?

  1. Fastener torque
  2. Material hardness
  3. Surface finish
  4. Radial runout Correct answer.

Explanation

A dial indicator measures small linear displacements, so with the plunger on a rotating shaft it reads the total variation in the shaft surface, known as runout. Surface finish, hardness and torque each require a different instrument.

Question 13Common Occupational Skills (safety, tools, communication, documentation)

What happens to the tension in each leg of a two-leg sling as the legs are spread further apart?

  1. The tension in each leg decreases
  2. The tension stays the same
  3. The tension becomes equal to the load weight
  4. The tension in each leg increases Correct answer.

Explanation

Spreading the legs increases the angle from vertical, so each leg must carry a larger share of the load to produce the same vertical lifting force. The rated capacity of a sling therefore falls as the included angle grows.

Question 14Common Occupational Skills (safety, tools, communication, documentation)

A rigger holds a clenched fist at shoulder height toward the crane operator. What does this signal mean?

  1. Stop Correct answer.
  2. Lower slowly
  3. Dog everything
  4. Hoist the load

Explanation

In standard crane hand signalling a clenched fist held up means stop, halting all motion of the crane. Only one designated signaler should give signals at a time so the operator has a single source of commands.

Question 15Common Occupational Skills (safety, tools, communication, documentation)

During an inspection you find a wire rope sling with a crushed section and several broken wires. What should you do?

  1. Use it only for loads under half the rated capacity
  2. Return it to service if the breaks are only on the outside
  3. Shorten the sling and continue using it
  4. Tag it out of service and remove it from the area Correct answer.

Explanation

Crushing and broken wires are removal criteria because they reduce the rope strength and indicate internal damage that cannot be seen. The sling is tagged out, taken out of service and physically removed so it cannot be picked up again by mistake.

Question 16Common Occupational Skills (safety, tools, communication, documentation)

Why does a millwright record parts used and hours worked on a work order at the end of a repair?

  1. To update the operator's training record
  2. To calculate the machine's production rate
  3. For maintenance history and cost tracking Correct answer.
  4. To satisfy the parts supplier's warranty

Explanation

A completed work order builds the equipment history and lets the planner track repair costs, repeat failures and parts consumption. That record is what supports decisions on preventive maintenance and replacement.

Question 17Common Occupational Skills (safety, tools, communication, documentation)

Which information is found in Section 4 of a safety data sheet?

  1. Firefighting measures
  2. First-aid measures Correct answer.
  3. Toxicological information
  4. Handling and storage

Explanation

The sixteen sections of a safety data sheet follow a fixed order: Section 4 covers first-aid measures, describing what to do after exposure by inhalation, skin contact, eye contact or ingestion. Knowing the section numbers lets a worker find critical information quickly in an emergency.

Question 18Common Occupational Skills (safety, tools, communication, documentation)

Before entering a confined space, in what order should the atmosphere be tested?

  1. Toxics, then flammables, then oxygen
  2. Oxygen, then flammables, then toxics Correct answer.
  3. Toxic gases, then oxygen, then flammables
  4. Flammables, then toxics, then oxygen

Explanation

Oxygen is tested first because many combustible sensors need adequate oxygen to give a valid reading and because oxygen deficiency is immediately life threatening. Flammable gas is tested next, followed by toxic gases, all from outside the space before entry.

Question 19Common Occupational Skills (safety, tools, communication, documentation)

Which of the following is acceptable as a fall-arrest anchor point?

  1. A nearby guardrail that feels solid
  2. A 22 kN rated anchor point Correct answer.
  3. A rope tied to a vent stack
  4. A handrail of 25 mm pipe

Explanation

Fall-arrest anchors must be engineered and rated to withstand the arrest forces, commonly taken as 22 kN (5000 lbf) per worker in Canada. A guardrail, handrail or building service is not designed for that load and can pull free during a fall.

Question 20Common Occupational Skills (safety, tools, communication, documentation)

Why should a worker repeat an instruction back over the radio before acting on it?

  1. It records the instruction for the logbook
  2. It lets other crews hear the plan
  3. It confirms the message was received correctly Correct answer.
  4. It keeps the radio channel open longer

Explanation

Repeating back the message closes the communication loop and lets the sender correct any misheard detail before work begins. This three-way exchange is standard practice for critical instructions where noise or radio distortion can change the meaning.

Question 21Common Occupational Skills (safety, tools, communication, documentation)

A precision level is marked 0.02 mm/m. What does this marking mean?

  1. The level can measure errors up to 0.02 mm only
  2. One division equals a 0.02 mm rise per metre Correct answer.
  3. The level is accurate to 0.02 mm over its full length
  4. The bubble moves 0.02 mm for each division of tilt

Explanation

The marking describes the sensitivity of the vial: a change in height of 0.02 mm over a 1 m base moves the bubble by one division. Sensitivity is not the same thing as total accuracy, and it does not limit the instrument to measuring only tiny errors.

Question 22Common Occupational Skills (safety, tools, communication, documentation)

In the thread designation 1/2-13 UNC, what does the 13 represent?

  1. The pitch in millimetres
  2. The thread length in millimetres
  3. The number of threads per inch Correct answer.
  4. The major diameter in sixteenths

Explanation

In inch-series thread callouts the first number is the nominal major diameter and the second is the number of threads per inch. UNC means Unified National Coarse, so 1/2-13 has 13 threads per inch.

Question 23Common Occupational Skills (safety, tools, communication, documentation)

Before opening a hydraulic circuit, what must be done in addition to locking out the pump motor?

  1. Loosen the fittings slowly to let pressure escape
  2. Cap all open lines immediately
  3. Warm the oil to operating temperature
  4. Bleed off residual pressure and release accumulators Correct answer.

Explanation

A locked-out pump can still leave trapped pressure in lines and charged accumulators that will move actuators or spray hot oil once a fitting is opened. Pressure must be released through the designated bleed valves and accumulators discharged before the circuit is broken.

Question 24Common Occupational Skills (safety, tools, communication, documentation)

On a mechanical drawing, what does a datum identify?

  1. The finish allowance left for machining
  2. The tolerance on an unspecified dimension
  3. A reference surface for measurements Correct answer.
  4. The maximum allowable surface roughness

Explanation

A datum is a theoretically exact reference, usually a surface or axis, from which related dimensions and geometric tolerances are measured. Using a common datum keeps inspection consistent between the shop and the supplier.

Question 25Common Occupational Skills (safety, tools, communication, documentation)

A micrometer reads 0.03 mm when its measuring faces are closed. It is then used to measure a part and shows 12.45 mm. What is the actual size of the part?

  1. 12.48 mm
  2. 12.42 mm Correct answer.
  3. 12.75 mm
  4. 12.45 mm

Explanation

A reading of 0.03 mm with the faces closed means the instrument over-reads by 0.03 mm, so that amount must be subtracted from every measurement. Subtracting 0.03 mm from 12.45 mm gives an actual size of 12.42 mm.

Question 26Common Occupational Skills (safety, tools, communication, documentation)

A small fire breaks out inside an energized electrical control panel. Which class of portable extinguisher is intended for this type of fire?

  1. Class A
  2. Class C Correct answer.
  3. Class B
  4. Class D

Explanation

Extinguishers are classified by the fuel involved: A for ordinary combustibles, B for flammable liquids, C for energized electrical equipment and D for combustible metals. Because the panel is still energized, a Class C agent (such as carbon dioxide or a clean agent) is the correct choice. Water-based Class A agents must not be used until the power is confirmed off.

Question 27Common Occupational Skills (safety, tools, communication, documentation)

A millwright is about to grind a steel bracket with an angle grinder. Which protection is appropriate for the face and eyes?

  1. A face shield by itself
  2. Safety glasses by themselves
  3. Tinted safety goggles by themselves
  4. A face shield over safety glasses Correct answer.

Explanation

Grinding throws high-speed particles that can pass around the edges of a face shield, so impact-rated safety glasses must be worn underneath it as the primary barrier. The face shield then protects the face and throat from larger debris and sparks. A face shield alone is not an approved substitute for eye protection.

Question 28Common Occupational Skills (safety, tools, communication, documentation)

A bench grinder is being set up for general shop use. What is the maximum allowable gap between the face of the wheel and the tool rest?

  1. 1 mm
  2. 6 mm
  3. 3 mm Correct answer.
  4. 10 mm

Explanation

The tool rest must be kept close to the wheel, no more than about 3 mm (1/8 in), so that a workpiece cannot be pulled down into the gap and jammed or flung back. The rest is adjusted as the wheel wears and is rechecked whenever a wheel is changed. The tongue guard at the top of the wheel has its own, slightly larger, limit.

Question 29Common Occupational Skills (safety, tools, communication, documentation)

Before starting a non-routine repair, a millwright and an apprentice walk through the job step by step to list the hazards and the controls for each step. What is this practice called?

  1. A job hazard analysis Correct answer.
  2. A root cause analysis
  3. A pre-startup safety review
  4. A preventive maintenance inspection

Explanation

A job hazard analysis (also called a field-level risk assessment) breaks a task into steps and identifies the hazards and controls before work begins. It is done at the job site by the people doing the work and is reviewed when conditions change. The other terms describe investigations or program activities carried out at different stages of a job.

Question 30Common Occupational Skills (safety, tools, communication, documentation)

A millwright completes a repair that is only temporary and the permanent fix must wait for the next shutdown. What is the best documentation practice?

  1. Leave the details for the next shift to pass on by word of mouth
  2. Add the details to the PM checklist for the area
  3. Close the work order because the machine is running again
  4. Note the temporary repair and schedule the permanent fix Correct answer.

Explanation

Maintenance records must show what was actually done and what is still outstanding, so the temporary repair is described on the work order and follow-up work is raised for the shutdown. This gives planners the information to schedule parts, labour and downtime. Verbal handover or a closed work order leaves no reliable trace for the next technician.

Question 31Rigging, Hoisting and Lifting

Before any load is rigged or lifted, what two things must a millwright establish about the load?

  1. The boom length of the crane that will lift it
  2. Its total weight and the location of its center of gravity Correct answer.
  3. The colour code of the slings that will be used
  4. The number of workers available on the site

Explanation

Every lift begins with knowing how heavy the load is and where its center of gravity lies. The weight determines the required rigging capacity, and the center of gravity determines how that weight divides between the attachment points and whether the load will hang level.

Question 32Rigging, Hoisting and Lifting

What is the primary purpose of the latch on a crane or rigging hook?

  1. It lets two slings share the hook at the same time
  2. It prevents the hook block from shock loading the rope
  3. It increases the working load limit of the hook
  4. It keeps slings and fittings from slipping off the hook Correct answer.

Explanation

The latch closes the throat opening so a sling, shackle or eye cannot ride up and slip off, especially when the line goes slack. Latches add no strength and are never included in the hook's rated capacity.

Question 33Rigging, Hoisting and Lifting

A chain sling has a link with a cracked weld. What is the correct action?

  1. Remove the sling from service and tag it out Correct answer.
  2. Cut out the damaged link and reattach the hook
  3. Keep using it if the crack is under 10 mm long
  4. Weld-repair the link using a qualified welder

Explanation

Alloy chain slings must never be field repaired or reworked; welding destroys the heat treatment and the rated capacity. Any cracked, stretched, gouged or bent link makes the sling unfit for service. It must be tagged and removed so it cannot be used accidentally.

Question 34Rigging, Hoisting and Lifting

A nylon web sling has a hard, glazed patch where it contacted a hot workpiece. What should be done with the sling?

  1. Tag it and remove it from service Correct answer.
  2. Use it only for loads lighter than 500 lb
  3. Wrap the patch in tape and use it at half capacity
  4. Trim off the glazed edge and put it back in service

Explanation

Melted or glazed fibres from heat or chemical attack have lost their strength, and the damage usually extends beyond what is visible. Synthetic slings with burns, charring, or acid or caustic contact are permanently removed from service. Cutting away the damaged area is never an approved repair.

Question 35Rigging, Hoisting and Lifting

Which hand signal tells a crane operator to raise the load?

  1. Both arms extended outward and slightly raised, palms open
  2. Arm extended downward, forefinger pointing down, hand moving in a small horizontal circle
  3. Arm extended horizontally, palm down, hand moving back and forth
  4. Arm extended upward, forefinger pointing up, hand moving in a small horizontal circle Correct answer.

Explanation

The raise signal is given with the arm out and the forefinger pointing up while the hand circles, which is distinct from the lower signal that reverses the finger direction. Standard signals must be used consistently so the operator reads the same meaning from any signaler.

Question 36Rigging, Hoisting and Lifting

When assembling a screw-pin shackle for a lift, the pin should be:

  1. Seated fully so the pin shoulder bears on the shackle body Correct answer.
  2. Replaced with a grade 8 bolt if the original pin is lost
  3. Backed off half a turn so the sling can swivel
  4. Locked with a nut threaded onto the far end

Explanation

The rated capacity assumes the pin is fully engaged and its shoulder is tight against the shackle ear. A partly engaged pin bends under load and can be pulled out. Shackle pins must always be the manufacturer's correct replacement part.

Question 37Rigging, Hoisting and Lifting

A 2000 lb load is carried on a two-leg bridle whose legs each sit 60 degrees above the horizontal. Ignoring hardware weight, what is the tension in each leg?

  1. 1155 lb Correct answer.
  2. 1000 lb
  3. 866 lb
  4. 2000 lb

Explanation

Each leg initially carries half the load, 1000 lb, as a vertical share. Because the legs are inclined, the tension is that share divided by the sine of the angle from horizontal: 1000 / sin 60 degrees = 1000 / 0.866 = about 1155 lb. Steeper legs mean less tension; flatter legs mean more.

Question 38Rigging, Hoisting and Lifting

A 4000 lb load is lifted on a two-leg sling with each leg at 30 degrees above the horizontal. What is the approximate tension in each leg?

  1. 2828 lb
  2. 2310 lb
  3. 2000 lb
  4. 4000 lb Correct answer.

Explanation

The vertical share per leg is 2000 lb. Dividing by sin 30 degrees (0.5) doubles it to 4000 lb per leg, so the sling hardware and the load's attachment points must be rated well above the load weight. Flattening slings toward horizontal causes a rapid rise in tension.

Question 39Rigging, Hoisting and Lifting

Ignoring friction, what mechanical advantage does a single movable block provide when the pull line and the load line are parallel?

  1. 4
  2. 1
  3. 3
  4. 2 Correct answer.

Explanation

A single movable block is supported by two parts of rope, so the load is shared between them and the pull needed is about half the load. Friction in the sheave and rope stiffness reduce the actual advantage, which is why the theoretical value is never fully achieved.

Question 40Rigging, Hoisting and Lifting

A wire rope sling shows a birdcage, with the strands forced apart and the core visible. What is the correct disposition?

  1. Remove it from service immediately Correct answer.
  2. Serve it with seizing wire and return it to use
  3. Use it for vertical lifts only
  4. Reduce its rated capacity by 25 percent

Explanation

Birdcaging means the rope has been twisted or shock loaded and the strand structure is permanently disturbed; strength cannot be restored. Core protrusion, kinks and birdcages are all removal criteria. Seizing or derating does not make a distorted sling safe.

Question 41Rigging, Hoisting and Lifting

With boom length held constant, what happens to a mobile crane's rated capacity as the load radius increases?

  1. It increases steadily
  2. It decreases Correct answer.
  3. It decreases only past 45 degrees of boom angle
  4. It stays the same until the boom is fully extended

Explanation

Rated capacity falls as radius grows because the load moment on the boom and the tipping moment on the crane both increase. The load chart lists capacity against radius, so the chart must be read at the actual radius for the lift.

Question 42Rigging, Hoisting and Lifting

Why is a tag line attached to a load during a crane lift?

  1. To increase the rated capacity of the crane
  2. To control load rotation and swinging Correct answer.
  3. To measure the weight of the load while airborne
  4. To take part of the weight off the crane hook

Explanation

A tag line lets a worker steer and steady the load from outside the fall zone without touching it. It carries no load and adds no capacity. It must never be wrapped around a hand or body.

Question 43Rigging, Hoisting and Lifting

A load must be lifted at an angle to the axis of its eye bolts. What is the correct choice?

  1. A plain eye bolt, fully tightened against the load
  2. A forged shoulder eye bolt rated for angular loading and derated for the angle Correct answer.
  3. A standard eye bolt with an extra nut and washer added
  4. Two plain eye bolts sharing the load equally

Explanation

Angular pulls bend plain eye bolts at the shank and can open the eye. Forged shoulder eye bolts are designed to be loaded off-axis and must be derated according to the manufacturer's chart for the angle used. Plain eye bolts are for straight, in-line pulls only.

Question 44Rigging, Hoisting and Lifting

When building a timber crib stack to support a heavy machine, the timbers should be:

  1. Nailed at the corners and stacked as high as needed
  2. Stacked with all the grain running the same way
  3. Laid in alternating layers at right angles, fully bearing Correct answer.
  4. Stood on end as vertical posts under the load

Explanation

Alternating layers at right angles tie the stack together and spread the load over a wide base, and each timber must bear fully on the layer below. Cribbing is a compression structure, so short, solid, defect-free hardwood or engineered blocks are used.

Question 45Rigging, Hoisting and Lifting

A spreader beam is placed between the sling legs above a wide, fragile load mainly to:

  1. Allow the load to be rotated while suspended
  2. Reduce the total weight that the crane must lift
  3. Increase the rated capacity of the crane
  4. Keep the legs vertical so the load is not crushed Correct answer.

Explanation

A spreader converts the inward horizontal component of angled slings into compression within the beam, so the load sees only vertical lifting forces. Lifting beams and spreaders are rated for that bending and compression and must carry their own weight in the load calculation.

Question 46Rigging, Hoisting and Lifting

What effect does tying a knot in a rope have on its lifting strength?

  1. It can cut rope strength by about half Correct answer.
  2. It increases strength by spreading the load over more rope
  3. It has no effect as long as a bowline is used
  4. It only affects strength when the rope gets wet

Explanation

A knot forces sharp bends that concentrate stress and reduce the rope's breaking strength, often to roughly half. Any knotted assembly must be rated on its knotted strength, not on the rope's catalogue strength. For lifting, splices or certified fittings are used instead of knots.

Question 47Rigging, Hoisting and Lifting

A 3000 lb machine is lifted vertically from two points 6 ft apart, and its center of gravity lies 2 ft from point A. What load does each point carry?

  1. 2000 lb at A and 1000 lb at B Correct answer.
  2. 1000 lb at A and 2000 lb at B
  3. 1500 lb at A and 1500 lb at B
  4. 2250 lb at A and 750 lb at B

Explanation

The load at each support is the total weight multiplied by the distance from the center of gravity to the opposite support, divided by the span. For A: 3000 x 4 / 6 = 2000 lb; for B: 3000 x 2 / 6 = 1000 lb. The support nearer the center of gravity always carries more.

Question 48Rigging, Hoisting and Lifting

A symmetrical four-leg bridle sling supports a 6000 lb load. For capacity rating, how many legs are assumed to share the load?

  1. Three legs Correct answer.
  2. One leg
  3. Two legs
  4. All four legs

Explanation

Because a rigid load rarely lets all four legs share equally, recognized sling standards base the rating on three legs carrying the load. The rigging is therefore sized as if only three legs were effective, which provides a margin for the slack or short leg.

Question 49Rigging, Hoisting and Lifting

A load of 2000 lb is raised with a four-part line reeved through a set of blocks. Ignoring friction, what pull is needed on the lead line?

  1. 500 lb Correct answer.
  2. 2000 lb
  3. 1000 lb
  4. 250 lb

Explanation

The load is shared by the number of parts of line supporting the movable block, so 2000 lb divided by four parts gives 500 lb. Friction in the sheaves and the weight of the lower block mean the real pull is somewhat higher.

Question 50Rigging, Hoisting and Lifting

A wire rope sling is bent around a pin that is only slightly larger than the rope diameter. What is the effect on the sling's capacity?

  1. The sling must be derated because of the small D/d ratio Correct answer.
  2. Capacity increases because the rope grips the pin tightly
  3. Capacity is reduced only when the sling is used in a choker hitch
  4. Capacity is unchanged if the pin surface is polished

Explanation

Capacity depends on the ratio of the pin or shackle diameter (D) to the rope diameter (d). A small D/d ratio crushes and distorts the strands on the inside of the bend, so the sling's efficiency drops and it must be derated accordingly. Larger diameter fittings preserve more of the rope's strength.