Rigging and Heavy Lift

Tools in this group

• Center of Gravity and Pick-Point Load Share - Load on each of two pick points and the percent imbalance from the total weight, span, and CG offset, with a flag when the CG falls outside the picks. The head rigger and the load weight govern.
• Crane Net Capacity After Deductions - Net capacity for the hook after the OSHA 1926.1417(o) deduction stack (hook block, jib, wire rope), the total hook load, the percent of net, and the 75 / 90 / 100 percent flags. The manufacturer's load chart governs.
• Crane Power Line Clearance (OSHA 1926.1408) - The 20 ft everyone carries is a DEFAULT you take when you have not determined the voltage -- one of three options, and usually the most expensive. Determine the line voltage and Table A applies instead, starting at 10 FT for lines up to 50 kV, which is most distribution: on a 12 kV service that is 10 ft of working radius bought back for the price of a phone call to the utility. The trap runs the other way too. The 20 ft default is only for lines UP TO 350 kV; above that it is 50, and Table A climbs to 25, 35, and 45 -- so on transmission the remembered number is not conservative, it is wrong in the dangerous direction, and the tile flags a clearance that would satisfy a default which does not apply. Over 1,000 kV there is no number at all: the utility or a qualified engineer sets it.
• Crane Ground Bearing Pressure and Mat Size - Outrigger / crawler ground bearing pressure vs an allowable soil bearing, the area required to pass, and the square mat or cribbing side. A geotech source and a qualified person govern.
• Wire-Rope Sling D/d Bend Efficiency - Bend efficiency factor and reduced working load limit of a wire-rope sling from the D/d ratio, per the WRTB curve. Inspect every sling before the lift.
• Wind Force and Swing on a Suspended Load - Velocity pressure, lateral wind force, and swing angle on a suspended load from the sail area, wind speed, and shape coefficient. The manufacturer's in-service wind limit governs.
• Max Wind Speed Before a Load's Swing Limit - The inverse of the wind-on-load tile: the sustained wind speed at which a suspended load reaches a maximum allowable swing, V = sqrt(weight x tan(swing) / (0.00256 x area x shape)). A 4,000-lb load with 200 ft^2 of sail reaches a 5-degree swing at ~20.7 mph; a lighter load or bigger sail hits it sooner. A planning estimate; the manufacturer's in-service wind limit and the load chart govern.
• Tag Line Pull and Handler Count - Tag-line tension to control a suspended load, the number of handlers at a safe per-person pull, and a flag when a mechanical tag is needed. The lift director governs.
• Tandem (Two-Crane) Lift Load Share - Each crane's share of a tandem lift from the CG, the derated allowable per crane, and a combined pass / fail. A designated lift director and an engineered plan govern.
• Shackle / Eye-Bolt WLL and Angular Derate - Working load limit and the angular derate of a shackle (side load) or shoulder eye bolt from the pull angle, with a pass / fail. The manufacturer's chart governs.
• Spreader Bar vs Lifting Beam Below the Hook - Top sling tension, spreader-bar axial compression, lifting-beam bending moment, and headroom for a wide load from one hook. ASME BTH-1 / B30.20 and the rating plate govern.
• Spreader Beam Minimum Top-Point Height - The inverse of the spreader-beam tile: the minimum top-point height so the top-sling tension stays within the sling WLL, since a taller rig makes a steeper sling that pulls less. angle = asin( load / (2 x WLL) ), then top = (bar/2) x tan(angle). A 10,000 lb load on a 10 ft bar with 6,000 lb slings needs at least 7.54 ft of top height. Answers 'how much headroom do I need' instead of the tension from a set height. The WLL must exceed half the load. ASME BTH-1 / B30.20 and the rating plate govern.
• Forklift Load-Center Capacity Derate - Net forklift capacity at the actual load center from the data-plate rating, a pass / fail against the load, and the remaining margin. The capacity plate is the legal rating.
• Roller / Skate / Jacking Push Force - Steady and breakaway push force to move a load on rollers or skates, the grade component, and the skate count by capacity. Verify the floor's own capacity.
• Chain / Lever Hoist Effort and Travel - Hand-pull effort, hand-chain travel for the lift, and a pass / fail against the rated WLL of a chain or lever hoist. ASME B30.16 / B30.21; the rated WLL is the ceiling.
• Guy-Wire / Down-Guy Tension and Mast Download - The tension in a guy wire holding a mast, pole, or tower against a horizontal load, and the vertical compression it stacks onto the mast. A down-guy attached at height H_a and anchored a lead L away sits at theta = atan(H_a/L) above horizontal. To resist a horizontal top load H (wind, a conductor pull, a sign's wind area) the guy carries H / cos(theta) -- always MORE than the load, climbing steeply as the guy steepens -- and pulls DOWN on the mast by H x tan(theta) (the mast download the pole and footing must carry) and UP on the anchor by the same. A 500 lb load, 20 ft up, 20 ft out sits at 45 deg: 707 lb tension, 500 lb download. A guy at 63 deg more than triples the download -- why crews want long anchor leads. Single-guy statics only; the pole class, anchor capacity, guy grade, and the engineer / NESC / RUS govern.
• Block-and-Tackle Reeving Line Pull - The pull on the hauling (lead) line of a block-and-tackle or crane hoist reeved with N parts of line, and how much sheave friction costs. Frictionless, each part carries load/N; real sheaves lose a few percent each and the loss STACKS, so pull = load x (1 - k) / (1 - k^N) with k the per-sheave efficiency (~0.98 roller-bearing, 0.96 plain-bronze). A 20,000 lb load on 4 parts at k 0.98 needs 5,152 lb (vs the frictionless 5,000), a reeving efficiency of load / (N x pull) = 97.0%. More parts multiply the advantage but stack more friction, so doubling the parts never quite halves the pull. This is the STEADY hauling pull on the lead line only, not the higher force to start the load moving. A rigging screen; the block/rope ratings, the actual sheave friction, the reeving pattern, and a qualified rigger and lift plan govern.
• Rigging Block Redirect Resultant Load - Resultant force on a rigging block and its anchor when a line changes direction (up to twice the line tension when doubled back). Size for the resultant, not the line tension.
• Max Redirect Angle for a Block WLL - The inverse of the block-redirect tile: the largest direction change a block or anchor of a rated WLL can turn a line without the resultant exceeding the rating, angle = 2 x asin( WLL / (2 x line tension) ). A 3,000 lb line through a 5,000 lb block can turn up to 112.9 degrees; if the WLL is at least twice the line tension, any turn up to 180 degrees is within rating. Answers 'how far can I turn it' instead of the resultant from a set angle. Keep margin for shock; the qualified rigger and the tags govern.
• Multi-Leg Sling Load per Leg - The tension in each sling leg of a multi-leg lift: per ASME B30.9, a rigid load on 3 or more legs is assumed to hang from only 2, so the conservative tension divides the load over 2 legs and then by sin(angle from horizontal), with an equal-share reference and the 1/sin load factor. The qualified rigger and the sling tag govern.
• Wire-Rope Breaking-Strength Estimate and WLL - A field estimate of wire-rope minimum breaking strength (construction factor x diameter^2, default 46 tons/in^2 for IPS 6x19, editable) and the working load limit at a design factor (default 5:1). An ESTIMATE only - the manufacturer's certified breaking strength governs, and unmarked or uncertified rope must not be placed in service.
• Wire-Rope Diameter for a Required WLL - The inverse of the wire-rope-strength estimate: the rope diameter for a required working load limit, d = sqrt(WLL x design factor / construction factor), then rounded up to the next standard size. A 5-ton WLL at 46 tons/in^2 and 5:1 needs 0.74 in -- pick 3/4 in (5.18 t). An ESTIMATE only; the manufacturer's certified rating governs, and unmarked rope must not be placed in service.
• Spanned Cable Sag and Tension - The tension a horizontally spanned cable (a tramline, highline, span set, or messenger) develops from its sag: H = w L^2 / (8 d), the support tension H sqrt(1 + (4d/L)^2), and the developed length. A 100 ft span at 1 lb/ft sagging 2.5 ft runs 500 lb; pull it to a 0.5 ft sag and the tension jumps to 2,500 lb - five times the load for the same span, because tension is inversely proportional to the sag. Shallow parabola (sag under ~1/10 span), uniform load, level supports; a concentrated load is the sling-angle case. A planning screen; the rope WLL, the anchors, and the head rigger govern.
• Spanned Cable Minimum Sag for a Tension Limit - The inverse of the spanline-sag-tension tile: the least sag a horizontally spanned cable can be pulled to before the support (anchor) tension reaches the allowable, d_min = w L^2 / (8 sqrt(T_allow^2 - (w L / 2)^2)). A 100 ft span at 1 lb/ft held to a 502 lb rope WLL needs at least 2.5 ft of sag; pull it tighter and the tension climbs past the limit, because tension is inversely proportional to the sag. The allowable must exceed the w L / 2 support vertical reaction, or no sag can carry the load. Enter the rope WLL or anchor capacity with the design factor applied. A planning screen; the WLL, the anchors, and the head rigger govern.
• Two-Leg Bridle Leg Tension - Each leg's tension and angle and the horizontal beam reaction of an asymmetric two-leg bridle from the apex load and the run/rise to each point. The legs never carry half each -- the steeper leg carries more, and a shallow bridle drives both legs above the hung load.
• Three-Point Bridle Leg Tension (3-D) - The exact leg tensions of a three-point bridle from the apex load and each leg's east / north / rise offsets: the 3x3 static equilibrium T1 u1 + T2 u2 + T3 u3 = (0, 0, W) solved by Cramer's rule, with each leg's length and angle. Physical only while every tension is positive - the apex must hang inside the triangle of its attachment points (a rope can only pull), and an asymmetric hang splits 1,000 lb as 497 / 419 / 244, nothing like an even 333 each. A design aid, not a rigging sign-off.
• Beam Clamp Reaction and Side-Pull Check - What a bridle leg actually does to the clamp: V = T sin(angle), H = T cos(angle), each checked against the clamp's vertical WLL and the manufacturer's side-pull allowance (zero for most beam clamps). The steep 860 lb leg of the two-leg bridle example loads its clamp to only 38% vertically but 77% of a generous 500 lb side-pull rating - the side pull governs, and on an unrated clamp the verdict is re-rig, not pass. A design aid, not a rigging sign-off.
• Wire-Rope Clip Count and Spacing (OSHA Table H-2) - The minimum U-bolt wire-rope clips and their spacing to form a load-bearing eye, per OSHA 29 CFR 1926.251 Table H-2 (the old H-20): a 3/4 in rope takes 4 clips at 6 x the diameter (4.5 in) on center, a 1/2 in rope 3 clips, a 1 in rope 5. The U-bolt (saddle) goes on the DEAD end and the base on the LIVE end -- 'never saddle a dead horse' -- torqued to the maker's value in sequence and retorqued after the first load. Below 1/2 in the OSHA table lists no count; 2 clips is the common manufacturer minimum. A properly formed clip eye develops only about 80% of the rope's strength; the clip and rope manufacturer and OSHA govern the termination. A field reference, not a rigging sign-off.
• Winch Drum Line Pull by Layer - The derated line pull, mean diameter, and increased speed of a winch drum at a given rope layer (Pn = rated x drum / (drum + (2n-1) x rope)). The rated pull is a bare-drum first-wrap figure that fades 30-40% on the outer layers -- plan the pull for the layer you finish on, not the nameplate.
• Crane Outrigger Reaction from Lift Geometry - The maximum single-outrigger reaction over a corner from the gross load and radius, counterweight, and outrigger spread (R_max = (W+Wc)/4 + M/(sqrt(2) spread)). Not a quarter-share -- swinging over a corner can concentrate well over half the load into one outrigger. The load crane-ground-bearing asks for but never derives.
• Crane Load Radius and Boom-Tip Height from Boom Geometry - Turns the boom-angle-indicator reading into the load RADIUS the load chart is indexed by: radius = boom-foot offset from the center pin + boom length x cos(angle); tip height = boom-foot height + boom length x sin(angle). A 30 ft boom at 60 degrees off a foot 4 ft out and 6 ft up puts the hook at a 19 ft radius and 32 ft tip height; lowering to 45 degrees swings it out to 25 ft. The inverse gives the angle for a target radius, acos((target - offset)/length), and flags a target beyond reach. RIGID-BOOM GEOMETRY ONLY -- boom deflection under load, rope stretch, and an out-of-level machine all INCREASE the real radius and cut capacity. The load chart, the load-moment indicator, and a qualified operator/lift director govern.
• Lifting Lug / Padeye Pin-Hole Check - Checks an engineered lifting lug or padeye against all four ASME BTH-1 pin-hole failure modes -- bearing, net-section tension, and double-plane shear tear-out -- and reports the governing capacity and DCR. The four modes trade off through hole placement; a lug sized for gross tension alone can tear out at the pin.