Specification

In India they are made as per IS 5604: 1984 – Specification for Hand-operated Universal Gearless Pulling and Lifting Machines (First Revision).

This standard specifies the materials, requirements and testing for the hand-operated gearless pulling and lifting machines of lifting capacities up to 5 tonnes.

Applications

They are used for various applications like erection of steel structures, laying and pulling of pipes, guying, tensioning transmission line conductors (electric power transmission), pulling of under ground cables, moving and installing machines, etc.

Though they are supplied with standard length of wire ropes, there is no restriction on length of wire rope that can be used in such machines.

It may be noted that lifting and pulling capacity of each machine is different. Some of the technical data of such machines made by Tractel Tirfor India Pvt. Ltd. are as under.

For more information about application and technical data for machines made by Tractel, please visit their website – http://www.tractelindia.com

Specifications

ANSI/ASME B30.16-2007 Overhead Hoists (Underhung)

ASME B30.16 applies to the construction, installation, operation, inspection, testing, and maintenance of hand chain-operated chain hoists and electric and air-powered chain and wire ropes hoists used for, but not limited to, vertical lifting and lowering of freely suspended, unguided, loads which consist of equipment and materials.

Indian Standard

In India, chain pulley blocks are made as per IS 3832: 2005 (Hand-Operated Chain Pulley Blocks – Specification). This standard lays down the general requirements and testing of the hand-operated chain pulley blocks, worm or spur gear type. They are tested at 50% overload as specified in the standard.

They are generally provided with alloy steel load chain as per IS 6216: 1982. This standard prescribes the requirements for lifting chains, Grade T (8), accurately calibrated for use as load chains in pulley blocks and other lifting appliances. These are electrically welded round steel short link chains, fully heat-treated and tested and comply with the general conditions of acceptance of IS 5616: 1982.

Design safety factor shall be 4.0 or more.

Specifications for a chain pulley block include following items.

• Lifting Capacity (Safe Working Load).
• Number of falls of load chain.
• Effort on hand chain to raise safe working load.
• Weight of Chain pulley block assembly for 3.0 meter lift.
• Extra weight for each additional meter lift.

Effort on hand chain to raise safe working load by one reputed Indian manufacturer for various capacity of chain pulley blocks is as under.

Light chain pulley blocks and chain blocks requiring less pull on hand chain may be selected for easy of operation.

Operation and Inspection

Check and verify that structure or other equipment (e.g. travelling trolley) that will support the chain pulley block has a rated load capacity equal to or greater than the rated load capacity of the chain pulley block to be used.

Operation

• Check that chain is properly seated in sheaves and that chain is not twisted, kinked, or damaged.
• Don’t wrap chain around load or use chain as a sling.
• Don’t leave load suspended when chain block is unattended unless specific precautions have been instituted and are in place.

Inspection

Inspect break mechanism, load chain and hook as under.

Break Mechanism

Break is of self actuated screw and disc type. Brakes require more than audible-visual inspection. Check frequently by stopping chain block with / without load at various positions to test holding power and amount of drift. If drift is noticed, adjust break.

Periodically check evidence of worn, glazed, or oil-contaminated friction discs; worn pawls, cams or ratchet; corroded, stretched, or broken pawl springs.

Load Chain

Inspect contact points for excessive wear.

One manufacturer has suggested to measure inside length of 5 links under light tension using a caliper-type gauge. They have recommended replacing the chain if measurement exceeds maximum allowable gauge length as given below.

Hooks

Hook requires replacement because of excessive bends, twists, or throat opening indicating abuse or overloading.

Check for cracks (dye penetrant, magnetic particle, or other suitable detection method). Remove the crack if superficial by grinding. Replace the hook if it is deep.

Hook must be replaced when throat opening measurement has increased 5% over the original throat opening dimension of a new hook.

A bend or twist of the hook exceeding 10 degrees from the plane of the unbent hook requires replacement.

Measure hooks depth at load bearing point (base, bowl or saddle). Hook must be replaced when wear at load bearing point is 10% of the original depth of the hook load bearing point.

Caution:
Never repair hooks by welding or reshaping. Heat applied to the hook will alter the original heat treatment of the hook material and reduce the strength of the hook.

Manufacturers / Suppliers

Some of the Indian manufacturers / suppliers and their website address are as under.

Indef Marketing Services Ltd. – http://www.indef.com
Tractel Tirfor India Pvt. Ltd. – http://www.tractelindia.com
Hercules Mechanical Works – http://www.herculescranes.com

These clamps shall be designed to have ultimate load to be 5 times the Working Load Limit and shall be proof tested to 2 times the Working Load Limit. Generally they have welded alloy steel body and forged alloy components for strength and smaller size. Two types of clamps are used for handling plates or fabrications. They are vertical lifting clamps and horizontal lifting clamps as under.

Vertical Lifting Clamps

Vertical lifting clamp is used for the lifting, turning, moving or vertical transfer of sheet, plates, or fabrications from horizontal to vertical and down to horizontal (180°) as needed.

Fixed hoisting eye clamp is used as a single point pick or when used with a spreader beam with multiple vertical drop lines.

The hinged hoisting eye allows for the clamp to place and lift the load from any direction, or with a multiple leg sling with out side loading the clamp.

They are available in a variety of styles as under.

Standard clamp for materials with a surface hardness to 37Rc (345 HB).
Larger jaw opening.
For use with Stainless Steel material.
For use with materials with a surface hardness to 47Rc (450 HB).

Non-Marring type clamps will not mar, or scratch the material surface. Use them for Materials such as aluminum, stainless steel, painted materials, aircraft skins, composite material, glass, plastic, etc.

Note: Check for Minimum WLL for these clamps. Generally they have Minimum WLL of 10% of Maximum WLL.

Horizontal Lifting Clamps

Horizontal lifting clamps with spring loaded tension have a pretension feature that allows the user to attach the clamps to the material for horizontal lifting and transfer of sagging and nonsagging material. These clamps must be used in pairs or more as shown below.

Non-Marring type clamps will not mar, or scratch the material surface.

If clamps are not fitted with spring loaded tension to have a pretension, check adequacy of its design to handle sagging material.

Acknowledgements:
This article is written based on information in Crosby’s General Catalog. For other types of clamps like beam clamps, drum clamps, etc. please refer their catalog.

Wire rope clips are made from two types of materials. They are malleable iron and drop forged steel. Malleable wire rope clips are to be used only for non-critical, light duty applications with small applied loads. They should not be used for lifting or suspending load.

Specifications

Wire rope clips are made as per Federal Specification FF-C-450D and ASME B30.26.

As per Federal Specification, they are classified as under.

Type I: Single grip, single saddle, with U-bolts and nuts. They are made in two classes.
Class 1 – Steel saddle.
Class 2 – Malleable iron saddle.
Type II: Double grip, double saddle, with U-bolt and nuts.
Type III: Double grip, double saddle, with bolt and nuts. They are made in two classes.
Class 1: Assembled with integral L-shaped bolts and nuts.
Class 2: Assembled with separate hex head bolts and nuts.
Type IV: Double grip, two taper threaded half clamps with hexagon nut.

Type I and Type III clips are widely used in the industry.

Type III clips having double saddle design eliminates the possibility of incorrect installation.

For dimensional detail, please refer the specification or Crosby’s General Catalog.

For elevator, personnel hoist, and scaffold applications, refer ANSI A17.1 and ANSI A10.4. These standards do not recommend U-Bolt style wire rope clip terminations.

For OSHA (Construction) applications, see OSHA 1926.251.

Tables showing minimum number of clips to be installed, amount of wire rope required to turn back and tightening torque for various sizes of forged wire rope clips meeting performance requirements of Federal Specification FF-C-450D, Type I, Class 1 and Type III are given below.

Type I, Class 1 Clips

Type III Clips

*The tightening torque values shown are based upon the threads being clean, dry, and free of lubrication.

Note: Above tables are reproduces from Crosby’s General Catalog.

Method of Installing Wire Rope Clips

When using wire rope clips, extreme care must be exercised to make certain that they are attached correctly. Failure to do so could result in serious injury or death. Carry out their installation as under.

Match the same size wire rope clip to the same size rope diameter. For example, use a 3/8” wire rope clip with a 3/8” wire rope. Inspect wire rope clip nuts before and after each use.

Wire rope clips should be placed on the wire rope connection with the corrugation in their saddles coinciding with the lay of the wire rope. Generally saddles are provided with right-hand helix. For wire rope with left-hand helix, use clips having left-hand helix.

Making an Eye with a Thimble

Turn back specified length of wire rope from thimble (please refer tables given above). Put first clip one saddle width from seized “dead end” (Figure 1). Seat “live end” (load carrying part) of wire rope in saddle and position U-bolt over “dead end.” Tighten nuts evenly to proper torque.

Put the second clip as near the loop or thimble as possible (Figure 2). Install nuts firmly but do not yet tighten to proper torque.

Install all remaining clips equally spaced between the first two clips (Figure 3). Install nuts firmly but do not yet tighten to proper torque.

Apply light tension to wire rope assembly to take up rope slack and then tighten all nuts evenly to proper torque.

Add at least one more clip if a pulley (sheave) is used in place of a thimble. If more clips are used than specified, proportionally increase the amount of wire rope that is turned back.

If Seale construction or similar large outer wire type construction in the 6 x 19 Class is to be used for sizes 1 inch and larger, add one additional clip.

After assembly, first apply load to test the assembly. This load should be of equal or greater weight than loads expected in use. Next, check and retighten nuts to recommended torque.

When the required minimum number of clips are installed and nuts are tightened to required torque, the assembly will develop up to 80% efficiency for clip sizes 1/8" through 7/8" and 90 % for sizes 1" through 3-1/2"

If more number of clips are used than shown in the table, the amount of turnback should be increased proportionately.

Wire Rope Splicing (joining) Procedures

The preferred method of splicing two wire ropes together is to use inter-locking turnback eyes with thimbles, using the recommended number of clips on each eye as shown above.

An alternate method (without using thimbles) is to use twice the number of clips as used for a turnback termination as shown below. In this method the rope ends are placed parallel to each other, overlapping by twice the turnback amount. The minimum number of clips should be installed on each dead end. All other instructions given above shall be followed.

In accordance with good rigging and maintenance practices, the wire rope end termination should be inspected periodically for wear, abuse, and general adequacy.

Specification

Turnbuckles are made as per Federal Specification FF-T-791b, ASME B30.26 and ASTM F-1145.

Federal Specification FF-T-791b covers swaged, welded, cast or forged turnbuckles with and without jam nuts. Three types and four form of turnbuckles are made as per this specification as under.

Type I – Open turnbuckle bodies
Form:
1 – Forged
2 – Spread
3 – Resistance welded and
4 – Arc or gas welded.
Type II – Pipe turnbuckle bodies and
Type III -Rigging turnbuckle bodies.

They are made in eight classes as under.

1 – Turnbuckle, body only without end pulls, heads not drilled.
2 – Turnbuckle, body only without end pulls, heads threaded right and left hand.
3 – Turnbuckle with stub and stub end pulls, complete.
4 – Turnbuckle with eye and eye end pulls, complete.
5 – Turnbuckle with hook and hook end pulls, complete.
6 – Turnbuckle with hook and eye end pulls, complete.
7 – Turnbuckle with jaw and jaw end pulls, complete.
8 – Turnbuckle with jaw and eye end pulls, complete.

Class 4 to Class 8 turnbuckles of Type I, Form 1 (Forged) are shown below.

Turnbuckles and end pulls are made from steel of a grade which will meet recommended working load limits specified by the specification.

They are made with design factor of 5:1 and recommended working load limits in Pounds for nominal outside diameter of threads in inch are as under.

Note:
As steel is selected by manufacturer, turnbuckles offered by some manufacturers have higher safe working load than specified by above specification.

Turnbuckles bodies and ends are available in standard lengths. For dimensional detail, please refer the specification or Crosby’s General Catalog.

Application

Turnbuckles are recommended for straight or in-line pull only.

Generally open forged turnbuckles are used for hoisting and rigging operations.

If a turnbuckle is used in an application where vibration is present, the end fittings should be secured to the frame with lock pins or wires to prevent them from turning and loosening.

Lock nuts are available for all sizes of turnbuckles.

Hooks

Hooks are installed on cranes, hoists, etc. and are also used for rigging. Rigging hooks are used as part of rigging tackle, such as sling assemblies, or with below-the- hook lifting devices. They are available in carbon steel and alloy steel materials. They are made as per requirements of ASME B30.10 and Federal specification RR-C-271D.

A latch, or mousing, bridges the throat opening of the hook for the purpose of retaining slings, chains, or similar parts under slack conditions and is not intended to support the load. Latch equipped hooks shall be used for all hoisting and rigging operations unless the application makes use of the latch impractical, or unsafe.

Many styles of hooks are available. Two typical rigging hooks are shown below.

Some rigging hooks (e.g., sorting hooks) are designed to carry the load near the point/tip as well as in the bowl or saddle of the hook. The designated SWL applies only when the load is applied in the bowl or saddle of the hook. Generally forged alloy steel hooks are used as rigging hooks. The manufacturer’s identification shall be forged or die-stamped on the hook.

Application

Load shall be applied in the bowl or saddle of the hook.

Side loading, back loading and tip loading as shown below are conditions that damage and reduce the capacity of the hook.

Inspection

All hooks shall be inspected as per statutory requirements.

Service Classification for Hooks

Hooks fitted on cranes, hoists, etc. are classified based on service/use as under.

Normal Service: Service that involves operating at less than 85% of rated load except for isolated instances.
Heavy Service: Service that involves operating at 85% to 100% of rated load as a regular specified procedure.
Severe Service: Heavy service coupled with abnormal operating condition.

Hooks fitted on cranes, hoists, etc. having any of the following conditions shall be discarded.

• Deformation: Any bending or twisting visible to the inspector.
• Throat Opening: Any distortion causing an increase in throat opening exceeding 5% or as otherwise directed by the hook manufacturer.
• Wear: Any wear exceeding 10% of the original section dimension of the hook or its load pin or as otherwise directed by the hook manufacturer.
• Cracks: Any visible crack.
• Latch engagement: Damaged or malfunctioning latch (if provided).
• Nondestructive Testing: Hooks with a rated load greater than or equal to 10 tons and assigned to heavy or severe service shall receive an NDT by a qualified inspector.

Rigging hooks shall be visually inspected for the following deficiencies before use:

• Distortions such as bending, or twisting exceeding 10 degrees from the plane of the unbent hook.
• Increased throat opening exceeding 15%.
• Wear exceeding 10% of the original dimension.
• Cracks, severe nicks, or gouges.
• Hook attachment and securing means.

Rigging hooks shall be inspected as a part of the slings to which they are attached. The NDT of rigging hooks is not routinely required.

NDT Methods

Magnetic particle testing or liquid penetrant testing methods shall be utilized to inspect for surface intersecting discontinuities (i.e., stress or fatigue cracks).

NDT shall be done in accordance with the following American Society of Testing and Materials (ASTM) standards:
ASTM E-709, Standard Practice for Magnetic Particle Examination.
ASTM E-165, Standard Practice for Liquid Penetrant Inspection Method.

For magnetic particle testing, a coil, yoke, or wet technique should be used to eliminate the possibility of prod burns or arc strikes.

Repair of Hooks

Hooks with a crack, nick, or gouge shall be repaired by grinding lengthwise, following the contour of the hook, provided that the reduction of dimension is within the permissible limits as shown below.

ZONE A: Repair not required
ZONE B: 10% of original dimension
ZONE C: 5% of original dimension
ZONE D: Follow minimum thread size chart

Hooks shall not be repaired, altered, reworked, or reshaped by welding, heating, burning, or bending.

QUIC-CHECK® Feature

For quickly checking of hooks for deformation, Crosby provides Deformation Indicators and distance between them – AA as shown below for hoist hooks. Two markings are forged into the product, one just below the shank or eye and the other on the hook tip. This allows for measurement to determine if the throat opening has changed, thus indicating abuse or overload. It is called QUIC-CHECK® Feature by Crosby.

If there is no marking on a hook, two punch marks may be made on a hook and distance between them recorded. Measurement of distance between them after use will show deformation if any.

Barrel Hooks

They are used to handle barrels/drums. They are made from forged carbon steel. They are made as per Federal Specification RR-C-271D, Type V, Class 6.

Hooks made by Crosby has Working Load Limit of 1000 Kg (per pair of hooks) and has following dimensions.
I D of Eye = 39.6 mm.
O D of Eye = 71.4 mm
Overall Length = 174 mm and
Width of Lip = 73.2 mm.

Swivels

Swivels are positioning devices and are not intended to rotate under load. They are made as per Federal Specification RR-C-271D, Type VII. Swivels together with their pins shall be forged from carbon steel. They are made in three classes as shown below.

Class 1: Chain Swivel
Class 2: Eye and Eye Swivel and
Class 3: Jaw and Eye Swivel.

For information on their capacity and dimensions, please refer the specification or Crosby’s General Catalog.

Material, Specification and Marking

Eye bolts are made from forged carbon steel or alloy steel. Alloy steel eye bolts are forged, quenched, and tempered with improved toughness properties, intended primarily for low- temperature applications. Carbon steel eye bolts (ASTM A489) shall have the manufacturer’s name or identification mark forged in raised characters on the surface of the eye bolt. Alloy steel eye bolts (ASTM F541) shall have the symbol “A” (denoting alloy steel) and the manufacturer’s name or identification mark forged in raised characters on the surface of the eye bolt.

Eye bolts are made as per ANSI/ASME B18.15 and ASME B30.26.

ASME B18.15 is limited to dimensions and capacities for forged threaded eye bolts intended primarily for lifting applications, and cover the following types and styles:

Type 1, Plain Pattern (straight shank); Style A – Long Length; Style B – Short Length.
Type 2, Shoulder Pattern; Style A – Long Length; Style B – Short Length.
Short Length Shoulder Pattern eye bolts are also known as Machinery Type eye bolts.

ASME B30.26 include identification, ductility, design factor, proof load and temperature requirements.

Eye bolts shall have a minimum design factor of 5, based on ultimate strength. Working Load Limit shown is for in-line pull.

Eye bolts manufactured in accordance with ASTM A489 (Standard Specifications for Carbon Steel Lifting Eyes) are rated for lifting service between +30°F and +275°F. These temperature limitations are also referenced in ASME B18.15 (Forged Eye bolts). Eye bolts manufactured in accordance with ASTM F 541 (Alloy Steel Eye bolts) are rated for use at a low temperature of -40°F. ASTM F 541 requires the symbol “A” to denote alloy steel.

Safe Working Load for Carbon Steel Shouldered Eye bolts as per ANSI/ASME B18.15 is as under.

Safe Working Load for Carbon Steel Eye bolts as per ASME B30.26 for vertical (in-line) loading for Inch and Metric sizes are as under.

For angular lifts, adjust working load as follows:

IS 4190: 1984

Indian standard for eye bolts is IS 4190: 1984 (Specification for Eye Bolts with Collars). This standard specifies the basic dimensions, material, lifting capacity and conditions of use of lifting eyebolts of Grade M. These eyebolts, which are described as `universal` may be used in all cases involving vertical and inclined lifting. This standard covers only eyebolts with eyes of internal diameters capable of permitting direct engagement with eyehooks of the same lifting capacity (working load limit) for use with Grade T(8) chain. In the case of eyehooks for use with Grade M(4) chain, it may be necessary to use an intermediate component such as a shackle to make the connection.

Application

It is recommended to use shouldered eye bolts for rigging hardware, except when prohibited by the configuration of the item to which the eye bolt is attached. Where non-shouldered eye bolts are required, they shall be used only in vertical pulls or in rigging systems that are designed, analyzed, and approved by a qualified person.

For vertical loading, eye bolts without shoulders have the same load-carrying ability as shouldered eye bolts.

Shoulders of eye bolts shall seat uniformly and snugly against the surface on which they bear. Never undercut eye bolt to seat shoulder against the load. Always countersink receiving hole or use washers to seat shoulder.

When more than one eye bolt is used in conjunction with multiple-leg rigging, spreader bars or lifting beams should be used to eliminate angular loading. In case two or more than two eye bolts are used without spreader bars, their orientation shall be such that load is in the plane of the eyes as shown below (Orientation of eye bolts). When eye bolts cannot be properly seated and aligned with each other, a steel washer or spacer not to exceed one thread pitch may be required to put below the eye bolt. Proper thread engagement must be maintained. Use a washer with approximately the same diameter as the eye bolt shoulder and the smallest inside diameter that will fit the eye bolt shank.

If the hook does not go completely into the eye bolt, use a shackle to avoid loading the hook tip.

Installation for In-line Loading

For in-line loading application use regular nut eye bolt or shoulder nut eye bolt. Use number of nuts based on thickness of load as shown below.

Use one nut if thickness is more than one eye bolt diameter. Use two nuts if thickness is less than or equal to eye bolt diameter. Always tighten nuts securely against the load.

Installation for Angular Loading

Use shoulder nut eye bolt for angular loading. If the eye bolt protrudes so far through the load that the nut cannot be tightened securely against the load, use properly sized washers to take up the excess space between the nut and the load as shown below. Thickness of washers / spacer must exceed the distance between the bottom of the load and the last thread of the eye bolt.

Reeving of Sling

Slings shall not be reeved through an eye bolt or reeved through a pair of eye bolts. Reeving will alter the angle of loading on the eye bolt as shown below. Only one leg should be attached to each eye bolt.

Machinery Eye Bolt – Installation for In-line & Angular Loading

These eye bolts are primarily intended to be installed into tapped holes. For installation, tap the load (tap depth) to a minimum depth of one-half the eye bolt size beyond the shank length of the machinery eye bolt. If the plane of the machinery eye bolt is not aligned with the sling line, add shims (washers) of proper thickness to adjust the angle of the plane of the eye to match the sling line as shown below.

To attain the rated capacity, minimum thread shank length of engagement depends on parent material and must be as follows:
Steel: 1 thread diameter
Cast iron, brass, bronze: 1.5 times the thread diameter
Aluminum, magnesium, zinc, plastic: 2 times the thread diameter

Swivel Hoist Ring

Swivel hoist ring shown above is a patented product manufactured by The Crosbygroup Inc. and is available in UNC and Metric thread sizes. One of the main advantages for its use is self alignment of its eye with the load angle due to swivel movement and they are rated 100% for 90 degree angle. It gives 360° swivel and 180° pivot action as shown below.

Eye Bolt Inspection

Visually inspect each eye bolt before use. Eye bolts that are worn, cracked, bent, elongated or have damaged threads shall be discarded. Ensure that threads on shank and receiving hole are clean.

Note:
For more information on eye bolts (dimensions) and swivel hoist rings (different type of rings) please refer General Catalog of the Crosby Group.

Acknowledgement:

Sketches in this article are based on sketches in General Catalogue by Crosby Group.

Specifications

Shackles are manufactured in two configurations – Anchor Shackle and Chain Shackle. They are also known as Bow Shackle and Dee Shackle. Both are available with screw pin, round pin, or bolt type as shown below.

In USA, shackle specifications are defined by the following documents, depending on the shackle size:

For shackles 3/16 to 2 3/4 inches, the specifications are derived from Federal Specification RR-C-271, “Chains and Attachments, Welded and Weldless.”

For shackles 1 1/2 to 4 inches, the specifications are derived from MIL-S-24214, “Shackles, Steel, General Purpose and High Strength.”

For shackles 4 1/2 to 8 1/2 inches, ASTM A148M, “Standard Specification for Steel Castings, High Strength, For Structural Purposes,” should be used.

Note:
For the overlaps in size, with RR-C-271 and MIL-S-24214, either specification may be used; however, RR-C-271 is most commonly used. Catalogs and manufacturers’ literature will list the federal specification number as “RR-C-271(rev.).”

Two grades of shackles are made as per specification RR-C-271D.

Grade A shackles, together with their pins and bolts are forged from carbon steel. Grade B shackles together with their pins and bolts are forged from alloy steel.

Recommended safe working loads for these grades are as under.

It may be noted that shackles are sized by the diameter of steel in the bow section rather than the pin size. The recommended safe working loads are for In-Line loading. In In-Line loading, load is applied perpendicular to pin. If load is to be applied at an angle, it must be applied in the plane of the bow as shown below.

For side loading screw pin and bolt type shackles, safe working load shall be reduced as per following table.

However, shackles symmetrically loaded with two leg slings having a maximum included angle of 120° as shown below can be utilized to full Working Load Limit.

Design Factors:
Shackles manufactured in accordance with RR-C-271 and MIL-S-24214 have a minimum design factor of 5. Shackles manufactured to the requirements of ASTM A148M have a minimum design factor of 4.

Shackles for critical-lift service shall have an initial proof load test of two times the SWL (minimum). Before making a critical lift, ensure that the shackle has been proof tested.

ASME specification number for shackles is B30.26.

Specification number IS 6132: 2003, Forged Shackles for General Lifting Purposes – Dee Shackles and Bow Shackles is applicable in India. This Indian Standard is identical with ISO 2415: 1987 `Forged shackles for general lifting purposes – Dee shackles and bow shackles' issued by the International Organization for Standardization (ISO).

ISO 2415:2004 specifies the general characteristics of forged dee and bow shackles in a range of sizes having working load limits of from 0,32 t to 100 t and in Grades 4, 6 and 8, and presents their performance and critical dimensions necessary for their interchangeability and compatibility with other components.

Shackles by Crosby

In addition to normal shackles, Crosby makes two special types of shackles as under.

Wide Body Shackle

Use of wide body shackles increases sling bearing surface and eliminates need for a thimble. Due to higher D/d ratio, it also increases usable sling strength.

COLD TUFF® shackles

They are suitable for use to -50° F.

Application

Select type of a shackle as under.

Round Pin Shackles: They can be used in tie down, towing, suspension or lifting applications where the load is strictly applied in-line.

Screw Pin Shackles: They can be used in any application where a round pin shackle is used. In addition, screw pin shackles can be used for applications involving side-loading circumstances. Reduced working load limits are required for side-loading applications. While in service, do not allow the screw pin to be rotated by a live line, such as a choker application.

Bolt-Type Shackles: They can be used in any applications where round pin or screw pin shackles are used. In addition, they are recommended for permanent or long term installations and where the load may slide on the shackle pin causing the pin to rotate.

Useful Information on Use of a Shackle

The shackle pin shall never be replaced with a bolt; only a properly fitted pin shall be used. Bolts are not intended to take the load that is normally applied to the pin as shown below.

Centralize whatever is being hoisted on the pin by suitable washers or spacers as shown below.

Screw pin shackles shall not be used if the pin can roll under load and unscrew as shown below.

When using a shackle to make choker hitch, place pin in the eye of sling as shown below.

For more information like dimensions, finish, etc. please refer Crosby’s General Catalogue. Their website address is – http://www.thecrosbygroup.com

Types of Hitches

Every lift uses 1 of 3 Basic Hitches shown above – Vertical, Choker and Basket. Detail about various sling configurations using them is as under.

Single Vertical Hitch

In single vertical hitch a sling is used to connect a lifting hook or other device to a load. In this configuration the total weight of the load is carried by a single leg, the sling horizontal angle is 90º (angle between horizontal line and sling), and the weight of the load can equal the maximum working load limit of the sling. This hitch provides absolutely no control over the load because it permits rotation. A tagline should be attached to prevent rotation which may damage the sling.

Bridle Hitch

Two or more sling hitches can be used together to form a bridle hitch. This configuration provides good load stability when the load is distributed equally among the legs (symmetrical objects), the hook is directly over the load’s center of gravity and the load is raised level. In case of non-symmetrical objects (off-center loads), a sling leg may be fitted with a turnbuckle to adjust the length to level it. Instead of a turnbuckle, come-along of adequate capacity may be also used. Proper use of a bridle hitch requires that sling angles are carefully measured to ensure that individual legs are not overloaded. Because the load may not be distributed evenly, when more than two slings (3 or 4 leg slings) are used, load may be carried by only two legs while other legs are only balancing it. Unequal length sling legs may be one reason for this. In view of this, it is recommended to assume that the load is carried by two legs only and the sling may be rated as two leg sling. If a qualified rigger or rigging specialist ensures that the load is evenly distributed, the full use of all the legs is allowed.

Note:
All wire rope sling capacity tables (e.g. in ASTM B30.9 and Wire Rope Users Manual) consider all legs sharing equal loads.

Single Basket Hitch

The single basket hitch is used to support a load by attaching one end of the sling to the hook, then passing the other end under the load and attaching it to the hook. One shall ensure that the load does not slide along the sling during lifting.

Double Basket Hitch

The double basket hitch consists of two basket hitches passed under the load. They must be placed under the load so that it is balanced. The lags of the hitches must be kept far enough apart to provide balance but not so far apart that low angles are created and the legs pull in towards the centre. The angle between the load and the sling should be approximately 60º or greater to avoid slippage. On smooth surfaces, both sides of the hitch should be snubbed against a change of contour to prevent the sling from slipping as load is applied. Otherwise use a double wrap basket hitch.

Double Wrap Basket Hitch

The double wrap basket hitch is a basket hitch wrapped completely around the load and compressing it rather than merely supporting it, as done by the ordinary basket hitch. The double wrap basket hitch can be used in pairs like the double basket hitch. This arrangement is used for handling loose material, pipes, rods, or a smooth cylindrical load because the sling is in full 360º contact with the load and tends to draw it together.

Single Choker Hitch

The single choker hitch forms a noose in the rope. It does not provide full 360º contact with the load. It should not be used to lift loads difficult to balance or loosely bundled. The hitch reduces lifting capacity of a sling as this method of rigging affects the ability of the wire rope components to adjust during the lift, places angular loading on the body of the sling and creates a small diameter bend in the sling at the choke point.

Doubled Choker

The single choker hitch can be doubled up to provide twice the capacity or to turn a load as shown below (Doubling a single choker hitch is not the same as using a double choker hitch.).

Double Choker Hitch

The double choker hitch consists of two sling chokers attached to the load and spread to provide load stability.

Double Wrap Choker Hitch

Double wrap choker hitch is formed by wrapping the sling completely around the load and hooking it into the vertical part of the sling. This hitch is in full 360º contact with the load and tends to draw it tightly together. It can be used either single on short, easily balanced loads or in pairs on longer loads.

Endless Slings or Grommet Slings

Endless slings are used for all three types of basic hitches as shown above. They are made from wire ropes, chains and synthetic materials. They are flexible but tend to wear faster than other slings because normally they are not fitted with fittings and deforms when bent over hooks.

Sling Angle

The loading in any type of sling is affected by the angle of the sling leg. Any angle other than vertical (sling angle = 90º) at which the sling is rigged, increases the loading (tension) on the sling. Due to this, sling’s working load limit reduces. As the angle decreases the stress imposed on the leg of a sling increases. This angle, which is measured between a horizontal line and the sling leg or body, is called sling angle or horizontal angle as shown below.

Sling’s working load limit (WLL) can be calculated by applying trigonometrical function (for stress calculation) as under.

Sling’s working load limit = Sling’s vertical capacity x sine of horizontal angle.

For easy of understanding and 'day-to-day' practical calculation above equation can be written as under.

Sling’s Working Capacity = Factor x Sling’s Rated Capacity

Where Factor shall be taken based on sling angle from following table.

As sling stresses increase tremendously with angles smaller than 45°, it is recommended not to use sling angle less than 30º. Low sling angles also create large horizontal compressive forces in the load which may be sufficient to cause buckling, especially in long flexible loads. If two or more slings are used, the minimum horizontal angle shall be used for calculating working capacity.

As measuring of sling angle can be difficult on a construction site, use the following methods to estimate safe working loads for common sling configurations.

Each rule is based on the safe working load of a sling in vertical hitch of a given size and material and the ratio H/L, where H is the vertical distance of the hook to the top of the load and L is the distance, measured along the sling, from the saddle of the hook to the top of the load as shown below.

If it is not possible to measure the entire length of the sling, measure along the sling from the top of the load to a convenient point and call it distance “l”. From this point measure vertically down to the load and call it distance “h”. The ratio h/l will be the same as the ratio H/L as shown in above sketch. Either H/L or h/l will apply equally to the following methods.

Note:
When sling legs are not of equal length, use smallest H/L ratio.

Capacity of Bridle Hitches (2-Leg)

WLL = WLL (of Single Vertical Hitch) x (H/L) x 2

Capacity of Bridle Hitches (more than 2 legs)

Three and four leg bridle hitches are rated equally to account for the possibility of unequal load distribution in a four leg hitch.

WLL = WLL (of Single Vertical Hitch) x (H/L) x 3

The three leg hitches are less susceptible to unequal distribution since the load can tilt and equalize the loads in each leg. However, lifting an irregularly shaped, rigid load with a three leg hitch may develop unequal loads in the sling legs. To be safe, use the formula for a two leg bridle hitch under such circumstances.

Note:
The rated capacity of a multi-leg sling is based on the assumption that all legs are used. If this is not the case, de-rate the sling assembly accordingly and hook all unused legs to the crane hook so they will not become snagged during the lift.

Capacity of Single Basket Hitch

For single basket hitch, sling capacity is as under based on sling configuration.

For inclined legs, WLL = WLL (of Single Vertical Hitch) x (H/L) x 2
For vertical legs, WLL = WLL (of Single Vertical Hitch) x 2

Capacity of Double Basket Hitch

For double basket hitch, sling capacity is as under based on sling configuration.

For inclined legs, WLL = WLL (of Single Vertical Hitch) x (H/L) x 4
For vertical legs, WLL = WLL (of Single Vertical Hitch) x 4

Capacity of Double Wrap Basket Hitch

Depending on configuration, safe working loads are the same as for the single basket hitch or the double basket hitch.

Capacity of Single Choker Hitch

When the load is hanging free, and the choke was not forced down towards the load, the normal sling angle is about 45 degree.

Based on sling angle (formed by the choker), capacity of single choker hitch is as under.

For sling angle of 45º or more, WLL = WLL (of Single Vertical Hitch) x ¾

Sling angles of less than 45º are not recommended. If they must be used,

WLL = WLL (of Single Vertical Hitch) x (A/B)

In a choker hitch, sling shall be long enough so that the choker fitting chokes on the wire rope body and never on the fitting (sleeve/ferrule).

Capacity of Double Choker Hitch

Based on sling angle (formed by the choker), capacity of double choker hitch is as under.

For sling angle of 45º or more, WLL = WLL (of Single Vertical Hitch) x ¾ x (H/L) x 2

Sling angles of less than 45º are not recommended. If they must be used,

WLL = WLL (of Single Vertical Hitch) x (A/B) x (H/L) x2

Capacity of Double Wrap Choker Hitch

Depending on configuration, WLLs are the same for the single choker hitch or the double choker hitch.

Capacity of Endless/Grommet Slings

Although grommet slings support a load with two legs, their WLL is usually taken as 1.5 times the WLL of a single vertical hitch. This reduction allows for capacity lost because of sharp bends at the hook or shackle.

Center of Gravity

Center of gravity is the point around which an object’s weight is evenly balanced. The entire weight may be concentrated at this point.

It is always important to rig the load so that it is stable. For this the load’s centre of gravity must be directly under the main hook and below the lowest sling attachment point before the load is lifted.

A suspended object will always move until its centre of gravity is directly below its suspension point. To make a level or stable lift, the crane hook block must be directly above this point before the load is lifted as shown below.

For load stability it is equally important to ensure that the support points of a load (i.e. where the slings are attached to the load) lie above its centre of gravity. Under suspension, an object’s centre of gravity will always seek the lowest level below the point of support. This knowledge is especially important for lifting pallets, skids, or the bas of any object since they all have a tendency to topple. This type of load will be stable if the attachments are above the centre of gravity as shown below.

An object symmetrical in shape and uniform in composition will have its centre of gravity at its geometric centre. With odd shaped objects, the centre of gravity can be difficult to locate. In such cases the rigger must guess where it lies, rig accordingly and signal for a trial lift. The centre of gravity will lie somewhere along a line drawn vertically from the hook down through the load. The rigger than adjust the slings accordingly to balance the load. If any load tilts more than 5º after it is lifted clear of the ground it should be landed and rigged over again.

It may be noted that when the centre of gravity is closer to one attachment point than the other, the sling legs must be unequal in length. In this case their angles and loads will also be unequal.

Loading at Pick Points for Off-Centre Centre of Gravity Objects

When the center of gravity is not equally spaced between the pick points, the sling and fittings will not carry an equal share of the load. The sling connected to the pick point closest to the center of gravity will carry the greatest share of the load. The load carried by each pick point can be calculated as shown below.

For above case, load carried by slings 1 and Sling 2 will be,

Sling 1 = (10 T x 2 m) / (8 m + 2 m) = 2 T
Sling 2 = (10 T x 8 m) / (8 m + 2 m) = 8 T

The above calculation is based on the fact that for balancing, torque (load x length of lever arm) generated by both the pick points shall be equal and opposite.

D/d Ratio

The capacity of a wire rope sling can be greatly affected by being bent sharply around pins, hooks, or parts of a load. The wire rope industry uses the term “D/d ratio” to express the severity of bend. “D” is diameter of curvature that the rope or sling is subjected to and “d” is the diameter of the rope. The minimum D/d ratio is usually taken as 20 which correspond to 92 % efficiency. As wire ropes are usually at lease 8 % stronger than the catalogue strength, the bent sling at D/d = 20 is therefore considered 100 % efficient. In case wire rope slings are used for smaller D/d ratio, sling capacity shall be decreased based on wire rope efficiency as per following graph. This curve is based on static loads and applies to 6-strand class 6×19 and 6×37 wire ropes.

Based on above graph, if the shackle or object has 2 times the diameter of a wire rope sling (D/d = 2) the basket sling capacity must be reduced by 35 % as shown below.

To increase d/d ratio and sling capacity, use wide body shackle. If D/d ratio is 5 after using wide body shackle, sling capacity shall be reduced by about 20 %.

Load hooks must have sufficient thickness to ensure proper sling D/d ratio, particularly when using slings in an inverted basket hitch; that is the sling body is placed into the hook and the sling eyes are facing downward.

Preventing Sling Damage

Make sure loads are not bolted to the floor. In winter, make sure that the load is not frozen to the ground.

If slings are used above spreader, select their size based on weight of load to be lifted plus weight of spreader.

Use additional single leg slings to wrap around the load as shown below. If they get damaged they are less costly to replace.

For large loads a 4-leg bridle sling can be made into a double basket sling by adding 2 single leg slings. These single leg slings can be made of larger diameter rope to better withstand load conditions as shown below. They are less expensive to replace than the entire 4-leg sling if they get damaged.

Use proper corner protection. A sharp steel edge may cut through wire rope sling; at least it will permanently damage the sling. As shown below, sliced steel pipes have proven to an effective corner protector. For square and round objects proper wooden padding will be sufficient. Before making the final lift, do a trial lift. Check that the padding is strong enough and does not crack under the load weight.

Do not place the splice sleeves, rope thimbles, or sling hooks around corners as shown below. A sleeve failure will result in the failure of the sling.

Acknowledgement:

In this article, figures and technical information from Construction Safety – Slings published by Construction Safety Association of Ontario are used.

There are six types of slings based on material of manufacture – wire rope slings, alloy steel chain slings, synthetic web slings, synthetic round slings, metal mesh slings and fibre rope slings. Information about these slings is given in this article.

Click on a link below to jump to a topic or read all.

Wire Rope Slings

Alloy Steel Chain Slings

Synthetic Web Slings

Synthetic Round Slings

Metal Mesh Slings

Natural and Synthetic Fibre Rope Slings

General Recommendations on Use of Slings

Wire Rope Slings

Wire rope slings are a basic material handling tool and are the most frequently used type of slings in industry. Wire rope slings are made from wire ropes with either Independent Wire Rope Core (IWRC) or a fiber core. A sling manufactured with a fiber core is usually more flexible but is less resistant to environmental damage. Sling made of an independent wire rope core has greater strength and is more resistant to heat damage. Mostly slings are made from wire rope having right hand regular lay of 6×19 or 6×37 construction. Wire rope slings are made from various grades of wire rope, but the most common grades in use are Improved Plow Steel, Extra Improved Plow Steel (EIPS) and Extra Extra Improved Plow Steel (EEIPS).

Construction

Slings ends are generally made with plain loops or with thimbles.

Sling with Plain Loops

Sling with plain loops at both ends is used for general purpose lifting. The sling eye shall have maximum angle of 15 º a shown above. Generally the eye dimensions are W = 8d and L = 16d where d = wire rope diameter.

Sling with Thimbles

Thimble (shown above) is the reinforcing member of a rope eye. It protects the rope at the point of attachment. Thimbles are fitted to sling ends to protect the rope against wear and abrasion from hooks, links, pins, etc. Heavy duty thimbles are used for protection against concentrated wear. Commonly used sling end configurations with thimbles are shown below.

Sometime spelter or swaged type sockets are fitted at the end of a wire rope as shown below.

Sling ends are made by hand splicing, mechanical splicing or by rope clips as under.

Hand Splicing

Hand splice is made by forming an eye and "tucking" and "locking" a strand of the wire rope under other adjacent strands (interweaving the wire rope strands). Splicing by this method requires skill, is time consuming and requires long rope. The method is now replaced by mechanical splicing.

Mechanical Splicing

In mechanical splicing, the end of wire rope after forming an eye is secured to the sling body (wire rope) by pressing a metal sleeve/ferrule. A hydraulic swaging press with special dies is used to bond the sleeve in place. Extreme pressure forces the sleeve material to flow into the voids between the wires and strands, creating an assembly that maintains most of the wire rope's nominal breaking strength. This type of eye is known as loop back eye.

Flemish Eye

In Flemish Eye, the rope firstly undergoes a limited form of hand spliceing (Flemish Splicing) which is then completed by mechanically swaging a steel sleeve/ferrule over the ends of the rope as shown below.

Flemish eye is fabricated by unlaying the rope body into two parts, one having three strands, the other having the remaining three strands and core. The rope is unlayed far enough back to allow the eye to be formed by looping one part in one direction and the other part in the opposite direction and laying the rope back together. The strands are rolled back around the rope body and a metal sleeve is slipped over the ends and pressed (swaged) to secure the ends to the sling body.

Rope Clips/Clamps

It is recommended not to use wire rope clips (shown above) to fabricate wire rope slings, except where the application precludes the use of prefabricated slings and where the sling is designed for the specific application by a qualified person. It is also advised not to use slings made with wire rope clips in a choker hitch. If sling ends are fabricated by wire rope clips, they shall be made of drop forged steel and using adequate number of clips at recommended spacing. U bolt of a clip shall be fitted over the dead end of the rope and the live rope shall rest in the clip saddle. The clips shall be evenly tightened to recommended torque before and after the initial load is applied and shall be inspected regularly to ensure that the recommended torque remains.

Slings fabricated using wire rope clips shall be de-rated to 80% of the rated wire rope load capacity to account for the efficiency of the clips.

Swage Fittings and Spelter Sockets

Above picture shows open and closed type of swage and spelter sockets.

In case of swage fitting, a wire rope end is inserted into the fitting bore and swaged onto the rope (like mechanical splicing).

In case of a spelter socket, a wire rope end is inserted in the socket and attached to it by pouring molten metal (Zinc or White Metal) or resin in the fitting basket (cup).

For more information on spelter socketing procedures, please refer following standards.

IS 3937: Recommendation for socketing of wire ropes (Part 1: with Zinc, Part 2: with White Metal and Part 3: with resins).
ISO 7595: Socketing procedures for wire ropes―Molten metal socketing.
ISO 7596: Socketing procedures for wire ropes―Resin sockting.

For more information on splicing, please refer IS 5245 as under.

IS 5245, Part 1: Methods for splicing of wire ropes, Part 1 – Hand splicing of wire ropes.
IS 5245, Part II: Methods for splicing of wire ropes, Part II – Wire rope sling legs with Ferrule-Secured eye terminals.

Braided and Cable-Laid Slings

Braided Sling

8-part braided slings are fabricated from 8 pieces of small diameter wire ropes, braided together to form one large sling. They can be either flat or round. They are commonly used for high capacity lifts. They snug tightly to a load in a choker hitch, resist kinking and offer the ultimate in flexibility.

Cable-Laid Sling

Cable-laid slings are fabricated from a rope comprised of 7 small wire ropes. This construction creates a very pliable sling and is used where flexibility and resistance to kinking are more important than resistance to abrasion. Since the rope is made up of many smaller wire ropes, the sling can bend around smaller diameters without taking a permanent set or kink. The small wires, however, are susceptible to abrasion.

Minimum Length of a Sling

It is recommended to have minimum length of sling as under.

Slings made of rope with 6×19 and 6×37 classifications and cable slings should have a minimum clear length of rope 10 times the component rope diameter between splices, sleeves, or end fittings.

Braided slings should have a minimum clear length of rope 40 times the component rope diameter between the loops or end fittings.

Grommets and endless slings should have a minimum circumferential length of 96 times the body diameter of the grommet or endless sling.

Proof Loads

Wire rope sling assemblies shall be proof tested using the following criteria:

Hand Tucked: The proof load for hand-tucked slings shall be a minimum of the rated load and shall not exceed 1.25 times the rated load.

Wire Rope Clips: The proof load for wire rope clip slings shall be a minimum of the rated load and shall not exceed two times the rated load.

Others Configurations: The proof load for other types of slings including mechanical splice, zinc-poured, resin poured, and swaged socket shall be two times the rated load.

Multiple Leg Slings: The proof load for multiple-leg bridle slings shall be applied to the individual legs. The proof load for the individual legs shall be consistent with the particular single-leg assembly stated above. Any master link to which multiple legs are connected shall be proof loaded to two times the force applied by the combined legs.

D/d Ratio

The capacity of a wire rope sling can be greatly affected by being bent sharply around pins, hooks, or parts of a load. The wire rope industry uses the term “D/d ratio” to express the severity of bend. “D” is diameter of curvature that the rope or sling is subjected to and “d” is the diameter of the rope. The minimum D/d ratio is usually taken as 20 which correspond to 92 % efficiency.

Rated Loads / Capacity

Safe Working Load (SWL) Limit / Rated Capacity of a sling depend on strength of material (wire rope), fabrication efficiency and design factor (factor of safety).

Rated capacities (SWL) of commonly used single leg slings for vertical lifting expressed in Tons (2000 lb) are as given under. Rated loads in the tables are based on design factor of 5 and minimum D/d ratio of 25/1.

Wire Rope Classification: 6×19 or 6×37
Type of Core: Fiber Core (FC)
Wire Rope Grade (Tensile Strength): Extra Improved Plow Steel (EIPS) Grade

Wire Rope Classification: 6×19 or 6×37
Type of Core: Independent Wire Rope Core (IWRC)
Wire Rope Grade (Tensile Strength): Extra Improved Plow Steel (EIPS) Grade

Wire Rope Classification: 6×19 or 6×37
Type of Core: Independent Wire Rope Core (IWRC)
Wire Rope Grade (Tensile Strength): Extra Extra Improved Plow Steel (EEIPS) Grade

Indian sling manufacturers generally offer following two types of mechanically spliced slings in wire rope construction 6×19 or 6×37.

1.    Wire rope with fibre core made from galvanized wire as per Grade 1570 (160 Kgf / mm²).
2.    Wire rope with steel core made from black wire as per Grade 1770 (180 Kgf / mm² = Improved Plow Steel).

Rated capacities (SWL) of these single leg slings for vertical lifting expressed in Tonne (1000 Kgf) based on design factor of 5 are as under.

Note:
Generally wire rope of 6×19 classification is used for wire rope diameter up to and including 1 inch. For wire rope diameter larger than 1 inch, 6×37 classification is used.

IS 2762: Specification for wire rope slings and sling legs covers dimensions, construction, loading, tests and marking of one-, two-, three- and four-leg slings for wire ropes of nominal diameter 8 to 44 mm, having legs of following types:
a) Single part spliced,
b) Double part spliced endless, and
c) Double part grommet.

To get lighter slings, please specify wire rope with independent wire rope core (IWRC) made from wires having higher tensile strength (say 220 Kgf /mm² which is equivalent to grade 2160 / Extra Extra Improved Plow Steel Grade) and factor of safety = 5.

Construction Safety Association of Ontario recommends to use wire rope slings made from from improved plow steel with independent wire rope core to reduce the risk of crushing.

Attachments

Various types of attachments like link, hook, swivel hook, plate lifting clamp, etc. are attached to sling eyes for various applications. When two or more slings are connected to a common link for make a lifting bridal, the assembly is called multiple leg sling.

Above picture shows two, three and four leg slings with oblong link and eye hooks. Three and four leg slings are used for level lifting of a load.

When using a multiple leg sling, ensure that the rating shown for the single leg sling is not exceeded in any leg of the multiple leg sling.

All attachments shall have a rated capacity equal to or greater than that of the wire rope sling.

Ensure that all welded end attachments are tested by the manufacturer or equivalent entity at twice their rated capacity before initial use.

Effect of Environment

Permanently remove from service fiber core wire rope slings of any grade if they are exposed to temperatures in excess of 180º F (82º C).

Follow the recommendations of the sling manufacturer when you use metallic core wire rope slings of any grade at temperatures above 400º F (204º C) or below minus 40º F (minus 40º C).

Inspection and Removal

Make periodic inspections of slings at intervals not greater than 12 months. Do not inspect a sling by passing bare hands over the wire rope body. Broken wires, if present, may puncture the hands. Deterioration that would result in loss of original strength shall be observed. Remove sling from service if any of the following conditions are present:

• Severe localized abrasion or scraping of one-third the original diameter of outside individual wires.
• Kinking, crushing, bird caging or any other damage resulting in distortion of the rope structure.
• Evidence of heat damage.
• End attachments that are cracked, deformed, or worn to the extent that the strength of the sling is substantially affected.
• Severe corrosion of the rope or end attachments.
• For strand-laid and single-part slings, ten randomly distributed broken wires in one rope lay or five broken wires in one strand in one rope lay.
• Broken wires in braided and cable-laid slings as per table given below.

Recommendations on Use of Wire Rope Slings

Use wire rope slings with independent wire rope core (IWRC) to reduce the risk of crushing.

All eyes be fitted with thimbles and formed by Flemish Splice and secured by swaged or pressed ferrules/sleeves (mechanical splicing). Flemish Eye has reserve strength in case of failure of ferrule/sleeve.

Wire rope slings shall not be shortened or lengthened by knotting or twisting or with wire rope clips or other methods not approved by the sling manufacturer.

Do not subject fiber core wire rope slings to degreasing or to a solvent because of possible damage to the core.

Wire rope wedge sockets shall not be used to fabricate wire rope slings.

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Alloy Steel Chain Slings

Chain slings are used for application requiring flexibility and resistance to abrasion, cutting and high temperatures.

Construction and Rated Loads

Chain slings used for overhead lifting applications must be manufactured from alloy steel. Alloy steel chain slings are made from various grades of alloy, but the most common grades in use are grades 80 and 100. Rated loads for alloy steel chain slings shall be based on a minimum design factor of 4. If other grades of chain are used, use them in accordance with the manufacturer's recommendations and guidance. The general configuration of a chain sling is as shown below.

Rated loads (with Design Factor = 4) for vertical lift of single leg alloy steel Grade 80 and Grade 100 chain slings are as shown under.

Note:
As per Construction Safety Association of Ontario, like all other slings and attachments, chain slings and attachments must have design factor (factor of safety) of 5.

IS 2760: Specification for steel chain slings covers the requirements, methods of rating and testing of single-, two-, three- and four-leg or branch welded chain slings of Grades L (3), M (4), S (6) and T (8) using chains conforming to IS 2429 : Part I : 1970, IS 3109 : Part I : 1970, IS 6217 : 1971 and IS 6215 : 1971 respectively together with the appropriate range of components.

Attachments

All attachments shall have a rated capacity at least equal to that of the steel chain with which they are used.

All welded components in the sling assembly shall be proof-load tested as components or as part of the sling assembly.

Where used, handles shall be welded to the master link or hook before heat treatment (This prohibits welding on chain slings during field operations.).

Effect of Temperature

If the chain sling gets heated to a temperature above 400°F (204°C), rated loads shall be reduced in accordance with the chain manufacturer’s recommendations regarding usage both while heated and after being heated. If chain slings are to be used in temperatures of -40°F (-40°C) or less, the manufacturer should be consulted.

Typical reduction of chain sling’s rated load (Safe Working Load) according to temperature is as under.

Inspection, Repairing / Reconditioning and Removal

Make periodic inspections of steel chain slings at intervals no greater than 12 months.

Make a thorough inspection of slings and attachments. Look for wear, defective welds, nicks, cracks, breaks, gouges, stretch, bends, discoloration due to excessive heat, excessive pitting or corrosion, throat opening of hooks, etc.

Minimum allowable thickness at any point on a link is as under.

Note: Minimum allowable chain thickness is approximately 12 % reduction in diameter.

Use damaged slings only after they are repaired / reconditioned and proof tested by the sling manufacturer or a qualified person. Alloy steel chain, attachments, and coupling links used for repair shall conform to the strength requirements and other requirements of the original sling. It is recommended to replace rather than repair cracked, broken, or bent links.

Recommendations on Use of Chain Slings

Slings should be padded to prevent links from being bent and to protect the load.

Chain links and attachments shall hinge freely with adjacent links.

Chain slings shall not be shortened or lengthened by knotting, twisting, or other methods as shown below.

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Synthetic Web Slings

Synthetic web slings are light and flexible. They are fabricated by sewing woven synthetic webbing of nylon or polyester (Dacron) yarns. They are often selected when expensive, highly polished, fragile or delicate loads are to be lifted. The softness of the web will not mar, deface or scratch loads, while its flexibility assures a firm, secure grip around the item being lifted. Web slings have the ability to elongate, absorbing and minimizing the effects of shock loads. Nylon is resistant to many alkalis where as polyester is resistant to many acids. Since they are non-sparking, they can be safely used in explosive atmospheres. Nylon slings are more common but polyester slings are often recommended where headroom is limited since they stretch only half as much as nylon slings. Synthetic web slings may be coated with suitable material to improve abrasion resistance, protection from sunlight or ultraviolet degradation, seal out moisture, and prevent grit from penetrating the web and causing internal wear.

Construction and Rated Loads

Slings can be fabricated from single or multiple plies, may include accessories such as edge guard, wear pads or sleeves, and are available in several configurations as under.

Type I
Sling made with a triangle fitting on one end and a slotted triangle choker fitting on the other end. It can be used in a vertical, basket, or choker hitch.

Type II
Sling made with a triangle fitting on both ends. It can be used in a vertical or basket hitch only.

Type III
Sling made with flat loop eye on each end with loop eye opening on same plane as sling body. This type of sling is sometimes called a flat eye-and-eye, eye-and-eye, or double-eye sling.

Type IV
Sling made with both loop eyes formed as in Type III, except that the loop eyes are turned to form a loop eye which is at a right angle to the plane of the sling body. This type of sling is commonly referred to as a twisted-eye sling.

Type V
Endless sling, sometimes referred to as a grommet. It is a continuous loop formed by joining the ends of the webbing together.

Type VI
Return-eye (reversed-eye) sling is formed by using multiple widths of webbing held edge-to-edge. A wear pad is attached on one or both sides of the sling body and on one or both sides of the loop eyes to form a loop eye at each end which is at a right angle to the plane of the sling body.

Synthetic web slings are made from two class of stuffer weave construction webbing with a minimum certified tensile strength per inch of width of the webbing as under.
Class 5 Webbing – 6800 pounds.
Class 7 Webbing – 9800 pounds.

Rated loads for Type I, II, III and IV single leg slings for vertical lift for various constructions are as under.

Note: For Type VI slings, consult the manufacturer for rated loads

The rated capacity of synthetic web slings is based on the tensile strength of the webbing, a factor of safety of 5, and fabrication efficiency. Fabrication efficiency is typically 80 % to 85 % for single-ply slings but will be lower for multi-ply slings and very wide slings.

For slings made from other type of construction, select them based on rated load shown on sling identification.

Synthetic webbing materials other than nylon and polyester are also used and the manufacturer should be consulted for specific data for proper use.

Sling Attachments

If synthetic web slings incorporate metal fittings, the fittings shall have the following properties:

• Materials are compatible with the mechanical and environmental requirements of the sling.
• Fittings have a rated load at least the same as the synthetic webbing sling.
• They shall have sufficient strength to sustain twice the rated load of the sling without permanent deformation and a minimum breaking strength equal to five times the rated capacity of the sling.
• Surfaces shall be cleanly finished and sharp edges removed to prevent damage to the webbing.

To protect slings against wear and cutting due to repeated use against sharp corners, they are fitted with protective devices like buffer strips, edge guards and sleeve or sliding tube wear pads.

Effects of Environment

Certain synthetic materials perform better than others in specific applications and environments. Consult the sling manufacturer or a qualified person for a specific application or before using in and around chemical environments. High radiation or chemically active environments can destroy the strength of synthetic web slings. Specific environmental limits are as follows:

Do not use nylon and polyester slings in contact with objects or at temperatures in excess of 194º F (90º C), or below minus 40º F (minus 40º C).

Synthetic slings made from Kevlar (Kevlar is a registered trademark of DuPont de Nemours.), K-Spec (K-Spec is a registered trademark of SlingMax.) and nylon may be used in radiation areas when the responsible person ensures that the absorbed dose do not exceed 100,000 rad during the life of the sling.

Nylon web slings shall not be used where fumes, vapors, sprays, mists or liquids of acids are present.

Polyester web slings shall not be used where fumes, vapors, sprays, mists, or liquids of caustics are present.

Synthetic web slings are not recommended where extensive exposure to sunlight or ultraviolet light is experienced.

Store slings in an area where they will not be subjected to mechanical, chemical, or ultraviolet damage, or to extreme temperatures.

Inspection and Removal Criteria

Inspection should be made by the person handling the sling each day the sling is used. Periodic inspection shall be carried out at least annually by a qualified inspector.

Sling need replacement if cuts, holes, tears, broken stitching, worn eyes and worn or corroded or distorted fittings, burns from acid, caustics or heat are found.

Caution on Use of Synthetic Web Slings

When using sling in bridle and basket configurations, they should be used with extreme caution. At low sling angles one edge of the web will be overloaded and the sling will tend to tear as shown below.

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Synthetic Round Slings

Synthetic round slings also offer a number of advantages like synthetic web slings. They offer one additional advantage in that their jackets shield the fibre against ultraviolet degradation. A round sling is also easy to inspect and evaluate – if its jacket is damaged, take it out of service. Round slings have larger capacities than synthetic web slings of the same width. They can therefore be narrower.

Synthetic round slings are identified by Size Numbers adopted by the Web Sling and Tie Down Association to describe a slings or by Colour but always select them based on the vertical rated load shown on the sling identification.

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Metal Mesh Slings

Metal mesh slings are widely used in metalworking and in other industries where loads are abrasive, hot, or will tend to cut web slings. Unlike nylon and wire rope slings, metal mesh slings resist abrasion and cutting. Metal mesh slings grip the load firmly without extensive stretching.

Construction and Rated Loads

Material for Fabric Construction: Carbon Steel.

Rated loads of Metal Mesh Slings based on Design Factor = 5 for vertical and choker lift are as under.

Metal mesh slings are also made from materials other than carbon steel. They are made from alloy steel for higher rated loads and stainless steel for corrosive environments.

Effect of Environment

Metal mesh slings can be used without a rated load reduction in temperatures ranging from minus 20º F (minus 29º C) to 550º F (288º C) except elastomer-coated slings. Use elastomer-coated slings in temperature ranges of 0º F (minus 18º C) to 200º F (93º C).

Inspection

Make periodic inspections of metal mesh slings at intervals not greater than 12 months. Look for following items.

• Broken wires in any part of the mesh.
• Broken weld or broken brazed joint along the sling edge.
• Reduction in wire diameter of 25 percent or more due to abrasion or 15 percent or more due to corrosion.
• Lack of flexibility due to distortion of the mesh.
• Pitted, corroded, cracked, bent, twisted, gouged, or broken fittings.

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Natural and Synthetic Fibre Rope Slings

Slings manufactured from conventional three-strand natural or synthetic fiber rope are not recommended for use in lifting service. Natural or synthetic fiber rope slings shall be used only if other sling types are not suitable for the unique application.

Rated loads for synthetic fibre rope slings based on Design Factor = 5 and vertical lift are as under.

D/d ratio for rope slings shall be larger than 8/1.

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General Recommendations on Use of Slings

All types of slings shall have, as a minimum, the rated capacity clearly and permanently marked on each sling.

Each sling shall receive a documented inspection at least annually, more frequently if recommended by the manufacturer or made necessary by service conditions.

Wire rope slings shall be labeled with a tag or other identification methods similar to one shown below.

When repaired, a sling shall be permanently marked to identify the repairing agency.

New and repaired / reconditioned slings including welded components shall be proof load tested by the sling manufacturer or repair agency.

Replace hooks that have been opened more than 15% of the normal throat opening measured at the narrowest point or twisted more than 10° from the plane of the unbent hook.

Ensure that in a choker hitch, the choke point is only on the sling body, never on a fitting.

Do not rest loads on the sling. Do not pull a sling from under a load when the load is resting on the sling.

Do not drag slings on the floor or over abrasive surfaces.

For more information on slings please refer ANSI/ASME B30.9.

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Acknowledgement:

In this article some information is taken from OSHA’s website.
Their website address is – http://www.osha.gov/dsg/guidance/slings.