Derrick definitions

A derrick is an apparatus made of a mast (or equivalent) held at the top by guys or braces, with or without a boom, used with a hoisting mechanism and operating ropes. This definition comes directly from 1910.181(a)(1).

• Use this definition to determine whether a piece of equipment must meet the derrick rules in 1910.181.

An A-frame derrick is a derrick in which the boom is hinged to a cross member between the bottom ends of two upright members that spread apart at the base and join at the top; the boom point is secured at that junction and the side members are braced or guyed from the junction point. This is the definition in 1910.181(a)(2).

• The distinguishing feature is the A-shaped frame with a boom hinged at the cross member, compared with other derricks that may be single-masted, basket-style, or stiffleg-supported.

A basket derrick is a derrick without a boom, similar to a gin pole, whose base is supported by ropes attached to corner posts or other parts of the structure and whose base sits lower than its supports; its base location can be changed by varying the length of the rope supports. See 1910.181(a)(3).

• Use this when evaluating the stability and rigging of a rope-supported derrick during setup or moves.

A boom is a timber or metal section pivoted at the heel and supported at the point by chains, ropes, or rods; the boom length must be measured as the straight-line distance between the axis of the foot pin and the axis of the boom point sheave pin (or the upper load block attachment pin where used). This is specified in 1910.181(a)(12).

• Measure boom length exactly as the standard describes when using or preparing load charts or ratings for the derrick.

The rated load chart for a permanently installed derrick must include the manufacturer's approved load ratings at corresponding boom angles or operating radii, the specific component lengths used to determine those ratings, and the required parts for hoist reeving (rope size and construction may appear on the chart or in the operating manual). See 1910.181(c)(1) and its subitems 1910.181(c)(1)(i), 1910.181(c)(1)(ii), and 1910.181(c)(1)(iii).

• Keep the chart durable, legible, and posted where operators can see it.

For nonpermanent installations, the manufacturer must provide enough information so that capacity charts can be prepared for that specific installation, and those capacity charts must be located at the derrick or the jobsite office, per 1910.181(c)(2).

• If you install a derrick temporarily, make sure the job-specific chart is created from the manufacturer's data and made available on site.

All new derricks constructed and installed on or after August 31, 1971 must meet the design specifications of the American National Standard Safety Code for Derricks, ANSI B30.6-1969, as incorporated by reference in 1910.181(b)(2).

• When purchasing or installing new derricks, verify compliance with ANSI B30.6-1969 as required by the standard.

Only designated personnel are permitted to operate a derrick covered by 1910.181, as required by 1910.181(b)(3).

• "Designated" means selected or assigned by the employer or their representative as being qualified for the duties (1910.181(a)(16)).

Prior to initial use, all new and altered derricks must be inspected to ensure they comply with the provisions of 1910.181, as stated in 1910.181(d)(1)(i).

• That inspection should check the items listed elsewhere in the inspection rules, and any deficiencies must be addressed before putting the derrick into service.

Frequent inspections occur at daily to monthly intervals and are meant to catch defects that develop quickly; periodic inspections are more thorough and occur every 1 to 12 months (or as the manufacturer specifies) to identify wear and deterioration that take longer to appear. See 1910.181(d)(1)(ii), 1910.181(d)(1)(ii)(a), and 1910.181(d)(1)(ii)(b).

• Use frequent inspection for items exposed to rapid change and periodic inspection for complete system reviews.

Frequent inspections (daily to monthly) must include control mechanisms for adjustment, wear, and lubrication; chords and lacing (visual); tension in guys; plumb of the mast; deterioration or leakage in air or hydraulic systems; derrick hooks for deformations or cracks (see hook criteria); rope reeving for compliance with manufacturer recommendations; hoist brakes, clutches and operating levers for proper function; and electrical apparatus for malfunction or excessive deterioration. See 1910.181(d)(2) and its subitems such as 1910.181(d)(2)(i) and 1910.181(d)(2)(vi).

• Check these items before operations begin each day and more often if the derrick sees heavy use or harsh conditions.

Periodic inspections must include the frequent-inspection items plus a full check of structural members for deformations, cracks, and corrosion; bolts or rivets for tightness; pins, bearings, gears, sheaves, drums, rollers, and locking/clamping devices for wear or distortion; the gudgeon pin for cracks, wear, and distortion each time the derrick is erected; powerplants for proper performance and compliance; hooks; and inspection of foundations or supports for continued ability to sustain imposed loads. See 1910.181(d)(3) and subitems 1910.181(d)(3)(i)(a-f).

• Use periodic inspections to catch slower-developing problems that could become hazards if left unchecked.

A derrick idle for 1 month or more but less than 6 months must receive an inspection meeting the frequent-inspection requirements and 1910.181(g)(3) before being placed back in service; if idle over 6 months it must receive a complete inspection meeting both the frequent and periodic requirements plus 1910.181(g)(3) before use; and standby derricks must be inspected at least semiannually under the frequent requirements and 1910.181(g)(3). See 1910.181(d)(4).

• Follow these timing rules before returning a derrick to service after a lay-up period.

Prior to initial use, operational tests must be performed for load hoisting and lowering, boom up and down, swing, and operation of clutches and hoist brakes, as required in 1910.181(e)(1) and its subitems 1910.181(e)(1)(i-iv).

• Complete these tests to confirm safe functioning before placing the derrick into service.

All anchorages must be approved by the appointed person, and rock and hairpin anchorages may require special testing, as stated in 1910.181(e)(2).

• Make sure the person approving anchorages has the authority and competence to verify capacity and suitability.

Employers must perform preventive maintenance on derricks to keep them in safe operating condition, as required by 1910.181(f)(1).

• Establish a preventive maintenance program that follows manufacturer guidance and addresses items identified during inspections and testing.

The term "load, working" means the external load in pounds applied to the derrick and includes the weight of load-attaching equipment such as load blocks, shackles, and slings, as defined in 1910.181(a)(22).

• Include all lifting hardware weight when calculating capacities and selecting rigging.

Yes; unless otherwise specified, the term "rope" in this section refers to wire rope, according to 1910.181(a)(28).

• If you plan to use synthetic rope or other types, confirm any special requirements or manufacturer recommendations before use.

A "Safety Hook" is a hook with a latch that prevents slings or the load from accidentally slipping off the hook, as defined in 1910.181(a)(29).

• Use safety hooks where there is a risk of the sling or load becoming disengaged during lifts.

Side loading is a load applied at an angle to the vertical plane of the boom; it should be avoided because booms are designed for vertical-plane loads and side loading can put unsafe stresses on the boom and its attachments, as defined in 1910.181(a)(30).

• Inspect for and prevent side loading when rigging, and consult manufacturer guidance if unusual load geometry is required.

Swing means rotation of the mast and/or boom to move loads horizontally about the axis of rotation, as defined in 1910.181(a)(34).

• Plan swing movements carefully to avoid personnel exposure and to prevent side loading or other unsafe conditions.

An "appointed" person is someone assigned specific responsibilities by the employer or their representative, while a "designated" person is selected or assigned by the employer as being qualified to perform specific duties. See 1910.181(a)(10) and 1910.181(a)(16).

• In practice, use "appointed" for authority/approval roles (e.g., anchor approvals) and "designated" for qualified operators or inspectors.

A derrick bullwheel is a horizontal ring or wheel fastened to the foot of a derrick used to turn the derrick by ropes leading from the wheel to a powered drum, as defined in 1910.181(a)(15).

• It's used to rotate the mast when a powered means at the base is preferred over rotating at the head.

Derrick hooks must be inspected frequently for deformations or cracks; hooks with cracks, more than 15 percent increase in throat opening, or more than 10° twist from the plane of an unbent hook must be removed from service and treated per the hook requirements in 1910.181(d)(2)(vi) and related provisions such as 1910.181(e)(3)(iii).

• If a hook fails inspection, tag it out and replace or recondition it according to manufacturer or recognized procedures before returning it to service.

Yes — employers must ensure employees who are exposed to overhead hazards while lifting with derricks wear head protection when there is potential for injury from falling objects. OSHA's head protection rule 1910.135(a)(1) applies where overhead hazards exist, and OSHA has explained that crane/hoist operators exposed to overhead hazards must wear helmets in its interpretation on head protection for crane operators (June 6, 2024 Letter of Interpretation).

• Employers must evaluate the workplace for overhead hazards under 1910.132(d)(1) and provide helmets that comply with the referenced ANSI standards per 1910.135(b)(1).

Yes. Employers must establish a preventive maintenance program for derricks that is based on the derrick manufacturer's recommendations, as required by 1910.181(f).

• Keep the manufacturer's recommended schedule and procedures on file and follow them for inspections, adjustments, lubrication, and parts replacement.
• Document maintenance actions and keep records readily available to demonstrate the program is being followed.

Cited: 1910.181(f).

You must take the listed precautions before beginning any adjustments or repairs on a derrick: arrange the derrick to minimize interference, engage all hoist drum dogs, lock the main or emergency switch if an electric hoist is used, post warning or out-of-order signs, lower and support or safely tie off booms being repaired, and set up a communication system between the hoist operator and the person in charge, per 1910.181(f)(2)(i).

• Examples of the specific items are in the subparagraphs (a)–(f) of 1910.181(f)(2)(i).

Cited: 1910.181(f)(2)(i).

You must lock the main or emergency switch in the open (off) position when an electric hoist is used for repairs, as required by 1910.181(f)(2)(i)(c).

• If you need to temporarily re-energize for testing, follow the control-of-hazardous-energy procedures in 1910.147 and OSHA guidance on temporary energization when necessary, as explained in OSHA’s interpretation on the minor servicing exception at https://www.osha.gov/laws-regs/standardinterpretations/2024-10-21.

Cited: 1910.181(f)(2)(i)(c) and OSHA interpretation https://www.osha.gov/laws-regs/standardinterpretations/2024-10-21.

It means you must set the mechanical devices (dogs) that prevent the hoist drum from turning so the drum cannot rotate while repairs are made, as required by 1910.181(f)(2)(i)(b).

• Engaging drum dogs provides a positive holding mechanism to prevent unexpected load movement during maintenance.
• After repairs, do not operate the derrick until guards are reinstalled and safety devices reactivated, per 1910.181(f)(2)(ii).

Cited: 1910.181(f)(2)(i)(b) and 1910.181(f)(2)(ii).

You may not operate the derrick until all guards are reinstalled, safety devices are reactivated, and maintenance equipment is removed, according to 1910.181(f)(2)(ii).

• A final check should confirm that all protective equipment and safeguards are in place and functioning before resuming operations.

Cited: 1910.181(f)(2)(ii).

Any unsafe condition found by inspection must be corrected before the derrick is operated again, as stated in 1910.181(f)(3)(i).

• Corrective work should restore the component to safe operating condition and meet required safety factors.
• If repairs are significant, follow the precautions in 1910.181(f)(2)(i) before performing them.

Cited: 1910.181(f)(3)(i).

Replacement and repaired parts must provide at least the original safety factor of the part they replace, as required by 1910.181(f)(3)(iii)(d).

• Use parts that meet or exceed the manufacturer's specifications for strength and durability.
• Document the repair or replacement and the basis for concluding the safety factor is preserved.

Cited: 1910.181(f)(3)(iii)(d).

Running ropes in use must be thoroughly inspected at least once a month, and a certification record showing the date, inspector's signature, and an identifier for the ropes inspected must be prepared and kept where readily available, per 1910.181(g)(1).

• The inspection should note any deterioration that results in an appreciable loss of original strength and determine whether continued use would be hazardous.
• Keep the certification record on file and accessible to operators and safety personnel.

Cited: 1910.181(g)(1).

Conditions that can show appreciable loss of rope strength include reduced diameter, broken or worn outside wires, corrosion or damage at end connections, improperly applied end fittings, and severe kinking, crushing, cutting, or unstranding, as listed in 1910.181(g)(1)(i)–(vi).

• Inspect areas where ropes contact sheaves or saddles carefully, since limited travel can cause heavy wear (1910.181(g)(2)).

Cited: 1910.181(g)(1) and 1910.181(g)(2).

Idle ropes that have been unused for a month or more must receive a thorough inspection for all types of deterioration before being put back into service, and a certification record with the date, inspector's signature, and rope identifier must be prepared and kept readily available, as required by 1910.181(g)(3).

• Treat idle-rope inspection the same or more thoroughly than running ropes since long idle periods can hide corrosion or internal damage.

Cited: 1910.181(g)(3).

Derrick operations must be directed only by the individual specifically designated for that purpose, as stated in 1910.181(h).

• The designated individual should be competent and familiar with operational and safety procedures for the specific derrick.
• Ensure the designation is clear to all workers and recorded in site procedures or a safe work plan.

Cited: 1910.181(h).

No derrick shall be loaded beyond its rated load, and when a load approaches the derrick’s maximum rating you must determine the weight within plus or minus 10 percent before lifting, as required by 1910.181(i)(1)(i)–(ii).

• Use calibrated scales or validated weight estimates and document the calculation when lifting near the rated capacity.
• If you cannot reliably determine weight within ±10 percent, do not lift the load.

Cited: 1910.181(i)(1)(i)–(ii).

The hoist rope must not be wrapped around the load; the load must be attached by slings or suitable devices; it must be well secured and balanced before lifting more than a few inches; and before hoisting you must check that the hoist rope is not kinked, multiple part lines are not twisted around each other, and the hook is brought over the load to prevent swinging, per 1910.181(i)(2) and 1910.181(i)(3)(i)–(ii)(a)–(c).

• Do a pre-lift check list that includes balancing, rigging inspections, and rope condition.
• If any of these checks fail, correct the issue before lifting.

Cited: 1910.181(i)(2) and 1910.181(i)(3).

No. No hoisting, lowering, or swinging shall be done while anyone is on the load or hook, and people should not be permitted to stand or pass under a suspended load; operators should also avoid carrying loads over people, as required by 1910.181(i)(3)(v) and 1910.181(i)(4)(ii).

• Barricade or exclude personnel from the drop zone and use taglines or other measures to control loads if people must be nearby.

Cited: 1910.181(i)(3)(v) and 1910.181(i)(4)(ii).

The operator must test the brakes each time a load approaching the rated load is handled by raising it a few inches and applying the brakes, and neither the load nor the boom shall be lowered below the point where fewer than two full wraps of rope remain on their respective drums, per 1910.181(i)(3)(vii) and 1910.181(i)(3)(viii).

• If brakes fail the test, stop the lift and correct the brake issue before proceeding.
• Monitor drum wraps during the lift; plan lifts so the drum never goes below two full wraps.

Cited: 1910.181(i)(3)(vii) and 1910.181(i)(3)(viii).

Exposed moving parts that present a hazard under normal operating conditions must be guarded, guards must be securely fastened, and each guard must be capable of supporting the weight of a 200-pound person unless it is located where stepping on it is impossible, as required by 1910.181(j)(1) and 1910.181(j)(1)(iii).

• Common moving parts to guard include gears, ropes, setscrews, projecting keys, chains, and sprockets.
• Maintain and inspect guards during preventive maintenance; replace damaged guards promptly.

Cited: 1910.181(j)(1) and 1910.181(j)(1)(iii).

You must keep a carbon dioxide, dry chemical, or equivalent fire extinguisher in the immediate vicinity of the derrick and ensure operating and maintenance personnel know how to use and care for it, and refueling from portable containers must use approved safety containers with automatic closing caps and flame arresters and never be done with the engine running, as required by 1910.181(j)(3)(i)–(ii) and 1910.181(j)(4)(i)–(ii).

• For the meaning of "approved" containers, see 1910.155(c)(3).

Cited: 1910.181(j)(3), 1910.181(j)(4), and 1910.155(c)(3).

Hooks must meet the manufacturer's recommendations and must not be overloaded, and safety-latch type hooks should be used wherever possible, as required by 1910.181(j)(2)(i)–(ii).

• Inspect hooks for deformation, cracks, or defects and discard hooks that show hook defects described elsewhere in the standard (see 1910.181(f)(3)(iii)(a)).

Cited: 1910.181(j)(2) and 1910.181(f)(3)(iii)(a).

Operations near overhead electric lines must comply with the electrical safety provisions referenced in 1910.181(j)(5), which point you to the safe work rules in 1910.333(c)(3).

• Maintain required minimum approach distances, de-energize and ground lines when possible, or use insulating barriers and qualified line-clearance procedures as described in 1910.333(c)(3).
• Train and designate qualified persons to work near energized overhead lines.

Cited: 1910.181(j)(5) and 1910.333(c)(3).

Necessary clothing and personal belongings must be stored so they do not interfere with access or operation of the derrick, according to 1910.181(j)(6)(i).

• Keep controls, emergency stops, and walkways clear; store items in designated bins or lockers away from control areas.
• Regularly inspect the cab to ensure nothing has migrated into operating spaces.

Cited: 1910.181(j)(6)(i).