LEEA FOU_(Global)_Workbook_v1.6_Jan_2024_ (3) (5).pdf

LEEA – Foundation Certificate (Global) – Course Workbook Shear, Tension and Compression Loading conditions: lifting equipment may be subjected to single or multiple types of stress: Single shear – forces acting across a material o Example: A lifting lug on...

LEEA – Foundation Certificate (Global) – Course Workbook Shear, Tension and Compression Loading conditions: lifting equipment may be subjected to single or multiple types of stress: Single shear – forces acting across a material o Example: A lifting lug on a waste skip being lifted Double shear – forces acting across a material in two areas o Example: A shackle pin under load Compression – a pushing force o Example: A jack body under load Tension – a pulling force o Example: A chain sling under load 44 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Torsion – a twisting force o Example: A rotating gearbox shaft driving a hoisting appliance Notes: 45 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Units of Measure A unit of measure can be described as a standardised quantity of a physical property, used to determine multiple quantities of a given property. For example: Weight Length Mass Force Different systems of units are based on different choices of a set of fundamental units. The most widely used system of units is the International System of Units, or ‘SI’. There are seven SI base units. All other SI units can be derived from these base units. Under the SI system when marking lifting equipment only one decimal point is used for fractions of a tonne e.g. 2.1t, apart from when marking 0.25 which is always to two decimal places, e.g. 2.1t, 2.2t, 2.25t, 2.3t, 2.4t, 2.5t, 2.6t, 2.7t, 2.8t, 2.9t Notes: 46 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Question: Let's check your understanding of symbols relating to units of measure. From the list below, select which one you think matches the symbol of 'cwt'. (Select one answer) □ Pound □ Hundredweight □ Imperial or US Ton □ Metric tonne □ Kilograms NOTE: Question: From the list below, select which one you think matches the symbol of ‘T’. (Select one answer) □ Imperial or US Ton □ Hundredweight □ Kilograms □ Metric tonne □ Pound NOTE: Symbols and Conversions Ton (US) T = Imperial or US Ton 1 Ton (US) = 2000lbs = 907.185kg = 0.907t (metric) (commonly referred to as the ‘short Ton’) 1 tonne (Metric) t = Metric tonne 1 tonne (metric) = 1000kg = 2204.62lbs (rounded to 2204lbs) 1 Ton (Imperial) kg = Kilogrammes 1 Ton (imperial) = 1016kg = 2239.9lbs (rounded to 2240lbs) (‘long Ton’ in the USA) 1 cwt cwt = Hundredweight 1 cwt = 50kg The hundredweight was established in the imperial measurement system in which 1 Ton is divided into 20 subdivisions, each being a hundredweight. Occasionally, lifting accessories may be found in service today with a marked safe working load or working load limit of ‘cwt’. 1 hundredweight (cwt) = 50 kg, therefore, a marked load limit of 2 Ton 1 cwt = 2050kg, rounded down to 2t. 47 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook ▪ 1kg = 2.2lbs ▪ 1 inch = 25.4mm ▪ 1 foot = 12 inches ▪ The SWL of new equipment will normally be in the metric units of tonnes (t) or kilograms (kg) or imperial units of Tons (T) and Pounds (lb). The generally accepted rule is that a SWL of less than one tonne or Ton are marked in kilograms or pounds, respectively. Notes: 48 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Types of Verification New equipment should comply with the essential health and safety requirements stipulated in any applicable legislation, product standard where available, and issued with the required conformity documentation. This documentation is often combined with the results of the verification and together they form the ‘birth certificate’ which is an important legal document. New Equipment For new equipment, the verification methods used by the manufacturer will depend on the standard being worked to. Some equipment is unsuitable for proof load testing due to the nature of the materials used, e.g., textile slings. Some items are assembled from components verifiedto their own standards so no further tests are required, e.g., grade 8 mechanically assembled chain slings. Once in service, the verification methods used will be those deemed necessary by the Competent Person in reaching their conclusions about fitness for purpose. Types of Verification There are many types of verification and test available to the examiner, including: 49 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Test Machines and Force/Load Measuring Equipment Many of the product standards and codes of practice that require the application of a load, or force, lay down the accuracy to which the test load or force must comply. For example, BS EN 818-1 for chain requires accuracy of ±1%. It requires that test machines and load cells be calibrated and verified by a competent person or authority, in accordance with ISO 7500-1 at intervals not exceeding 12 months. It also requires that the accuracy of the applied load/force must be within that required by the standard being worked to and, in all cases, within ±2% of the nominal load/force. ▪ ▪ 1.0 ▪ Grade 0.5 = ±0.5%, 1.0 = ±1% and 2.0 = ±2%. The certificate will also give the Lower Limit of Calibration. This will be expressed as a load or force, depending on the units in which the machine or device is calibrated. This is the minimum load/force that can be read from the display within the required accuracy. Test loads below this cannot be measured with this equipment. In some cases, there may also be a similar restriction on the upper limit. 50 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook The person performing any form of load test must be aware of the limitations for use imposed on the test machine, or load/force measuring equipment, and ensure that the accuracy of the applied load meets the requirements of the standard being worked to. LEEA Technical Requirements LEEA Technical Requirements requires that a procedure be in place for checking and verifying measuring devices at appropriate periods. For tapes and rules, it will probably only be necessary to regularly check them to ensure that they are undamaged. However, precision measuring equipment will require periodic verification. Crack Detection When dealing with general lifting equipment, usually only basic crack detection (such as dye penetrate or magnetic particle) is performed to examine welds. Trained operatives are required to perform the tests and interpret the results. The tests are relatively inexpensive, both in termsof the equipment and the labour necessary to perform the tests. For more detailed crack detection examinations, particularly on high-value items or where additional safety requirements require a higher degree of examination, other methods used are eddy current, radiography and ultrasonic. These are more expensive to perform and call for a high degree of training and skill to interpret the results. Notes: 51 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Dye Penetrant: Dye penetrant crack detection is used to locate cracks, porosity, and other defects that break the surface of a material and have enough volume to trap and hold the penetrant material. Liquid penetrant testing is used to inspect large areas very efficiently and will work on most nonporous materials. Magnetic Particle (MPI): common and easy to use method for the detection of surface cracks and laminations in ferrous/magnetic materials and is primarily used for crack detection. The specimen material is magnetized and if the material is sound, the magnetic flux is predominantly inside the material. If there is a surface-breaking flaw, the magnetic field is distorted, causing local magnetic flux leakage around the flaw. This leakage flux is displayed by covering the surface with very fine iron particles applied either dry or suspended in a liquid. MPIis considered much more accurate, effective, and efficient than inspections that use dye penetrants. MPI is excellent at detecting flaws on the surface of objects. Eddy Current: this test can accurately find tiny flaws (cracks, corrosion, erosion, material degradation and loss of thickness in a material) in materials using hi-tec software and detection equipment. Operators can identify anomalies on both the surface and sub-surface of a material with good levels of accuracy. It cannot however be used on materials that are non-conductive.It requires minimal set-up time and there is no requirement to use chemicals or radiation in the process. 52 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Ultrasonic: a transducer is moved over a material by the operator. This subjects the material to high-frequency sound waves; tiny cracks, hairline fissures, microscopic pockets will create an echo that is shown visually on the test machine. The benefits of UT include speed, reliability and versatility for use in the field. In addition, the results of particular tests can usually be recorded, allowing for comparisons to be made over a length of time (identifying signs of deterioration). It is now one of the most commonly used methods of NDT. Radiography: a hazardous form of NDT that is not so common now as it has been in the past. Operators can be exposed to dangerous doses of radiation and there are extremely specialist skills are required to use this equipment. The test monitors the varying transmission of ionising radiation through a material with the aid of photographic film or fluorescent screens to detect changes in density and thickness. It will locate internal and surface-breaking defects. Electromagnetic Wire Rope Examination: This is a fast method of detecting defects in long lengths of wire rope. The rope is passed through a magnetic field. Breaks and disturbances in the magnetic field are detected and a printout of the field is given. The test involves using an instrument to examine ferromagnetic wire rope products in which the magnetic flux and magnetic flux leakage methods are used. If properly applied, the magnetic flux method is capable of detecting the presence, location, and magnitude of metal loss from wear, broken wires, and corrosion, and the magnetic flux leakage method is capable of detecting the presence and location of flaws such as broken wires and corrosion pitting. 53 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Hardness: indentations are used to verify the hardness of lifting equipment following heat treatment, or where equipment is used in conditions that might affect the heat treatment. There are three basic methods: Vickers, Brinell and Rockwell. Brinell is the most common method used in the lifting equipment industry by manufacturers. The Brinell Test Impact: the impact test is normally carried out by manufacturers using one of two methods, Charpy, or Izod. The Charpy impact test, also known as the Charpy V-notch test, is a test that determines the amount of energy absorbed by a material during fracture. This absorbed energy is a measure of a given material's notch toughness and identifies the properties that material will exhibit when it experiences a shock loading that causes the specimen to immediately deform, fracture or rupture completely. A specimen of material is supported at its two ends on an anvil then struck on the opposite face to the notch of the swinging pendulum and broken as the pendulum swings through it. The height of the pendulum swing measures the amount of energy absorbed during fracture. Three specimens are tested at any one temperature. The Izod Impact test is similar to the Charpy test but in this test, the material is held vertically in a vice type jaw and is in a cantilever. Izod impact is defined as the kinetic energy needed to initiate fracture and continue the fracture until the specimen is broken. Izod specimens are notched to prevent deformation of the specimen upon impact. This test can be used as a quick and easy quality control check to determine if a material meets specific impact properties or to compare materials for general toughness. 54 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Bend: this is a simple and inexpensive qualitative test that deforms the test material at the midpoint causing a bend to form without actually breaking the specimen. The test can determine the ductility or resistance to fracture of a material. Generally, a bending test is performed on metals or metallic materials but can also be applied to any substance that can experience plastic deformation, such as polymers and plastics. The bend test is usually used for the testing of welds. The purpose of bend testing welds is to make sure that the weld has properly fused to the parent metal and that the weld itself does not contain any defects that may cause it to fail when it is subjected to bending. Marking Lifting Equipment: marking should be by suitable means, i.e. plate, metal tab, textile label, etc, permanently attached or by stamping directly into the equipment, preferably in a non- load bearing or low-stress area. Stamping into a stressed area may also be permissible provided that the mechanical properties of the component are not significantly impaired. Where applicable, the position and size of stamping should be as indicated in the relevant standard. When the means of marking can be lost, additional information should be used to convey this information. It is therefore recommended that the identification mark should also be put directly onto the equipment so that in the event of the original means of marking becoming detached, the identity is not lost, and the other information can be recovered from the related documentation. It may occasionally be necessary to re-mark lifting equipment, but care must be taken in doing so as stress raisers may be induced. Marking should therefore only be made on selected areas where detrimental effects are minimised, and the stamping should not be too sharp or excessively deep. Notes: 55 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Trigonometry of slinging and the effects of angles in sling legs Uniform and trigonometric load methods When multi-leg slings are used at angles, the load in the individual sling legs will increase as the angle of each leg to the vertical (included angle between the sling legs) becomes greater. There are currently many multi-leg slings in service which are marked with the rating expressed at the ‘included angle’ or range of angles, e.g. 0-90°. This is the angle between the legs of the sling, and it should be noted that the LEEA COPSULE no longer recommends this method, stating that best practice is to use the angle between the sling leg and the vertical. As many geographical regions will not yet have adopted this approach, we will reference both the ‘included angle’ and ‘angle to the vertical’ in this training course. It must however be noted that in some regions, the angle of the sling leg to the horizontal is also used (e.g. USA) and at specifically included angles of 60°, 90° and 120° (e.g. Australia). These will be visited in the regional versions of the Lifting Accessories Diploma (Australia) / (USA) training courses. Notes: 56 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook If a sling is to be used safely, allowance must be made for this angle and this is achieved by rating the sling in one of two ways. The two methods of rating are often known as the ‘uniform load method’ and the ‘trigonometric method’. The Uniform Load Method This is a simpler option. It has built-in safety advantages which allow only one working load limit up to an angle of 45° to the vertical (90° included angle) and a reduced working load limit at angles between 45° and 60° to the vertical (90° and 120° included angle). This is the recommended method that should be used for all multipurpose slings. The working load limits are obtained from the following: Single leg sling = 1.0 x WLL of a single leg Two leg sling 0-45° (included angle 0-90°) = 1.4 x WLL of a single leg Two leg sling 45°-60° (included angle 90° -120°) = 1.0 x WLL of a single leg Three and four-leg sling 0-45° (included angle 0-90°) = 2.1x WLL of a single leg Three and four-leg sling 45°-60° (included angle 90° -120°) = 1.5 x WLL of a single leg Standards where the uniform load method has been used, rate a multipurpose four-leg sling at the same working load limit as a three-leg sling of the same size and grade. This is on the assumption that the load might be taken by only three of the four legs. However, some national standards have now been amended such that they work on the assumption that the load may be carried by two of the legs. Note: Some standards do not recommend the rating of three leg slings at included angles greater than 90°. This is due to the danger of a user assuming that the ‘included angle’ referred to the angle between the legs of the sling instead of twice the angle of a leg to the vertical. Where slings are rated and marked on the basis of the angle to the vertical this danger does not exist. In Australia, the WLL of multi-leg slings comprising of more than two legs is limited to the same WLL as a two-leg sling. This is rated at an included angle of 60° between sling legs. Mode Factor The mode factor is a numerical value that is applied to the marked working load limit of the sling to determine the maximum load which the sling may lift, according to the mode of use and assembly, e.g. angle of sling legs to the vertical in use. 57 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Calculating the Mode Factor The mode factor for various sling angles is derived from the cosine of the angle to the vertical. Question: The WLL of a single leg sling is 2t. If two of these identical slings are used together at an included angle of 0-45° to lift a load, what is the maximum load that the sling assembly may lift? (Select one answer) □ a. 4t □ b. 2.8t □ c. 1.4t □ d. 5.4t The Uniform Load Method Design Factors The following design factors should be applied to the WLL of a single leg to establish the WLL of multi-leg sling assemblies or where a number of single slings are being used in combination: 2 leg sling 0°- 45° to the vertical (or 0° - 90° included) 1.4 2 leg sling 45°- 60° to the vertical (or 90°-120° included) 1.0 3 and 4 leg sling 0° - 45° to the vertical (or 0° - 90° included) 2.1 3 and 4 leg sling 45° - 60° to the vertical (or 90°- 120° included) 1.5 58 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook The Trigonometric Method The trigonometric method provides for a variation in the working load limit as the angle to the vertical (or the angle between the sling legs) varies. This method is the one that was previously used in many standards, but in order to use it for multipurpose applications, the operative must calculate the SWLs at various angles for each size of the chain, rope, etc. It also requires the operative to be trained in judging a range of angles and has the inherent danger that if he should misjudge these, the sling may well be overloaded. Although the uniform load method was introduced to some standard practices, some manufacturers continue to rate and mark multipurpose slings by the trigonometric method. Slings intended for multipurpose use marked this way will not comply with those standards that have adopted the uniform load method and it is strongly recommended that this method should be used only for slings designed for a single purpose or in accordance with the applicable national standards that permit it. Working load limits are obtained from the following: Single leg sling 1.0 x WLL of a single leg Two leg sling 2 x WLL of a single leg x cos β Three leg sling 3 x WLL of a single leg x cos β Four leg sling 4 x WLL of a single leg x cos β Rating of Slings The uniform load method simplifies matters by removing the need for tables and reducing the need for the operative to estimate angles. Whilst the uniform load method of rating is most easily applied to equipment such as multi-leg slings, it may, with advantage, also be applied to such items as eyebolts when used in pairs. Many national and international standards are now in favour of the uniform load method, largely on the grounds of safety and simplicity. However, this does not exclude the trigonometric method when working to national standards that allow it within their scope or with a justifiable reason to deviate from the uniform load method. 59 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Other forms of rating for lifting equipment Multi-Leg Slings (User Information): If a multi-leg sling is used with less than its actual number of legs attached to the load, then obviously the safe working load of the sling must be reduced.The amount by which it should be reduced can be calculated exactly but it is rather complex, as numerous factors need to be considered, including the method of rating. An easy way of ensuring that the sling is never overloaded is to reduce the safe working load from that marked on the sling according to the number of legs in use. The following ratings apply: ▪ A 4 leg sling with only 2 of the legs being used: ▪ A 3 leg sling with only 2 of the legs being used: Rating of Lifting Accessories Endless slings have fewer variations of use, but it should be remembered that the slinging factor for endless chain and wire rope slings assumes choke hitch, whereas the standard rating for textile slings assumes a straight pull. In all cases, it is also assumed that, at the points of attachment to both the lifting appliance and the load, the radius around which the sling passes are large enough to avoid damage to the sling. In the case of chain and wire rope endless slings, the rating takes account of the chain and wirerope being bent around itself on the bight. Rating of other types of lifting accessories will be detailed in the relevant modules within this, and further Diploma level LEEA courses. 60 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Wire Rope Slings Wire rope slings are very popular for general lifting duties. Due to their rigidity, they can be easily passed under loads when slinging. However, they are more susceptible to damage than chain slings. The construction of the rope from which the sling is made is within reason unimportant provided that the rope has adequate flexibility and an adequate minimum breaking load (from which the SWL of the sling is calculated). The rope should be ordinary lay and maybe six or eight strands having a fibre or a wire core. As with any lifting media, slings of all configurations can be assembled from wire rope and will be found in service. Those working in the offshore industry will be familiar with the ‘five leg’ slings attached to offshore containers. These are actually four-legged wire rope slings with a pendant sling attached to the master link. In general industry, the most common type of wire rope slingin service is the single leg. Thimbles: these are a protective insert that is fitted to the eye of a sling leg at the time of manufacture. Thimbles are fitted where it is desirable to protect the eye from the worst effectsof abrasion and point loading. Two common types of thimble are used in the construction of slings. The teardrop-shaped thimble, which is used where sling legs are to attach to other fittings, and the reeving thimble, is designed to permit the passage of one eye through the other so that the sling may be used in choke hitch. A similar protective inset, known as the stirrup or half thimble, is designed to protect the wire rope of a soft eye when the sling is used in choke hitch. Hand Spliced Eye: the hand spliced eye is an eye formed at the end of a sling by the traditional method of threading the individual strands of the rope back along the main body of the rope ina prescribed pattern. This type of eye is now less popular than the more modern ferrule secured eye, but it is still available and preferred by some users. 61 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Common Sling Assemblies: in addition to 2, 3 and 4 leg wire rope slings, the most commonly used wire rope sling assemblies are: Single leg with soft eye or thimble eye at each end. They can also be fitted with a link at one end and a hook at the other. 62 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Terminal Fittings Notes: 63 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Eye Terminations There are two ways that eyes can be made, ferrule secured (sometimes incorrectly referred to as a mechanical splice) and hand spliced. 1. Turn Back Loop The turn back loop is the cheaper option to manufacture and therefore is perhaps used more commonly for general purpose slings. With this method, an aluminium ferrule is used to secure the eye made in the end of the rope The eye is simply formed by passing the ferrule over the rope, bending the rope back on itselfto form the eye, pulling the ferrule back over the returning tail end of the rope and then pressing the ferrule. Under pressure the aluminium flows into the rope formation, making a homogeneous joint Ferrule Secured Eyes When square-cut ferrules are used, it is necessary for a small amount of the tail to protrude through the ferrule to ensure that the rope is fully engaged within the ferrule. The standard says that the length of this should be no more than one half of the rope diameter. However, if the rope has been cut by a heat process, a portion of the rope will have become annealed (softened) in the heat-affected area. The protruding tail in this case should be no more than an amount equal to one diameter of the rope and positioned so that none of the annealed section is within the ferrule Tapered Ferrules Tapered ferrules are also available from some manufacturers. In this case, the tail end remains within the ferrule and it is essential that the ferrule manufacturer’s instructions for fitting are followed. Often, the manufacturer of the ferrule will provide a small view hole in the ferrule to enable the tail end to be seen 64 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook 2. Flemish Eye A tapered steel ferrule is passed over the rope. The standing part of the rope is then taken, and three strands are unravelled and opened so that a ‘Y’ formation is made. Care must be taken to ensure that the strands still lay together as they had in the rope The leg of the ‘Y’ that includes the core is bent to form an eye so that the ends of the strands sit against the undisturbed part of the rope at the bottom of the ‘Y’. The remaining three strands are then re-laid into the rope in the opposite direction, taking up the position they originally had inthe rope so that the lay of the strands is not disturbed The ends of the strands are then evenly distributed around the intact standing part of the ropeto complete the eye. The ferrule is then slid back over the distributed wires without displacingthe strands and then pressed. The ferrule compresses and grips the rope Stirrups The minimum peripheral length of a soft eye should be four times the rope lay length. This is so as to ensure that the lay of the rope is not disturbed. It is extremely difficult to fit thimbles whenmaking Flemish eyes. If the sling is to be used in a choked situation then a protective attachment, known as a stirrup thimble, is commonly used to protect the rope from damage Hand Spliced Eyes A hand-spliced eye is an eye formed at the end of a sling by the traditional method of threading the individual strands of the rope back along the main body of the rope in a prescribed pattern Whilst this type of eye is now less popular than the more modern ferrule secured eye, it is still available and preferred by some users In the case of hand splices, these should be made with five tucks against the lay of the rope. The type of splice where the tucks are made with the lay of rope, should not be used as this tendsto undo if the rope rotates in use and is effectively banned from splicing wire ropes for lifting purposes Wire Rope Grips For many years it has been common practice to make temporary eyes in wire rope, particularly winch wires, by using clamp-type grips, commonly known as ‘bulldog’ grips. The use of such gripping devices which clamp the wire to form temporary eyes is not recommended for the manufacture of slings. The reason for this is that tests have showed that these grips do not give an acceptable or consistent level of safety. Sockets and Fork Ends Sometimes used fitted to the rope by a compression process or 65 by a white-metal or resin bonding process. The manufacturer’s/supplier’s advice should always be sought and Page followed where their use is intended. © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024  LEEA – Foundation Certificate (Global) – Course Workbook Single and 2-Part This is not a common way of producing sling legs but is used for WireRope Slings very large capacity slings, so the examiner needs to be aware of them. An endless sling is produced and then a thimble is bound at each end. The thimbles that are used must be two or three sizes larger than would normally be used for the rope diameter. The looped sling leg will take a greater load than a single part sling made from the same size rope and a thimble for the actual rope diameter would collapse under the increased load it has to take. In order to make the thimble fit the rope it is necessary to serve the rope with wire or spun yarn. A sling leg produced by this method is not capable of twice the WLL of a single part of the rope, as one might expect, but is in the order of 25% less than this. This is due to the increased stress due to the rope being bent around such a tight radius. Notes: 66 Page © LEEA Academy - FOU (Global) Workbook v 1.6 Jan 2024