Lift Planning and Evaluation
Before using any rigging device it is important to “plan your work and work your plan”. The “front end” time required to develop a successful lift plan may seem unnecessary for small or “non-consequential” loads. There’s always enough time to pre-plan “critical” lifts. After an incident involving what seemed to be a “non-consequential” amount of weight, the time required to mitigate the mess will dwarf the time spent on what was thought to be an unnecessary lift planning session. There’s always enough time to do the job right, the second time. We encourage you to make the “front end” investment in lift planning and successful rigging, before each and every lift.
A trained, qualified and knowledgeable user must take into account the following factors and issues and consider all relevant factors not addressed. Among the factors related specifically to slings and rigging, users must perform several activities, including (but not limited to) the following items:
Equipment and Lift Criteria
Fee based engineering services, including analysis and consideration of the above variables are available. Please contact us for details.
SLING SELECTION – Prior to selection, read and understand the information contained in our catalog and your responsibilities as detailed in all applicable regulations and standards. Select the sling with suitable characteristics for the load, environment and configuration of lift.
All sling users must be trained on the proper use of slings.
The American Society of Mechanical Engineers, in the ASME B30.9 Sling Safety Standard, clearly establishes the requirement for training. Section 9-X.1-Training states, “Sling users shall be trained in the selection, inspection, cautions to personnel, effects of the environment and rigging practices, covered by this chapter.”
DOL/OSHA Guidance on Safe Sling Use (29 CFR 1910.184) states that a qualified person is one: “who by possession of a recognized degree or certificate of professional standing in an applicable field, or who, by extensive knowledge, training and experience has successfully demonstrated the ability to solve or resolve problems relating to the subject matter and work.”
It is important that all sling users be knowledgeable about the safe and proper use and application of slings and be thoroughly familiar with manufacturer’s recommendations and all safety information provided with products. In addition, sling users need to be aware of their responsibilities as outlined in all applicable standards and regulations. If you are unsure whether you are properly trained or knowledgeable, DO NOT use slings or rigging devices until you are absolutely sure of what you are doing.
Slings must be protected from damaging edges, corners, protrusions or abrasive surfaces by materials of sufficient strength, thickness and construction to prevent sling damage and failure.
There are a variety of ways to employ sling protection and prevent sling damage. Regardless of the particular method chosen, the goal is to ensure that the sling maintains its ability to securely lift the load while avoiding contact with damaging or abrasive surfaces under tension. A qualified person must carefully consider the appropriate means to accomplish this goal by selecting sling protection appropriate for the types of exposure damage. Sling protection should not be makeshift (i.e., selecting and using cardboard, work gloves or other such items that were not designed to serve as protection devices).
Sling protection may not prevent cutting or other forms of damage. To avoid severe personal injury or death, personnel should be kept away from the load and never be under or near the load, while it is being lifted or suspended. Personnel should never be next to rigging under tension.
Chemically active environments can affect the strength of rigging products in varying degrees from moderate to total degradation. The materials used in the construction of slings and components must be compatible with the mechanical and environmental requirements imposed. Fumes, sprays, mists, vapors and liquids of acids or alkalis can degrade rigging products. The chemical agents must be identified. Specific time, temperature and concentration factors will assist the user and manufacturer in the selection of the appropriate sling material components.
It may be necessary to conduct an on-site suitability test. A sample would be subjected to exposure, under no load. The length of exposure must be determined by the qualified person. After exposure, the sample would be pulled to destruction to determine the retention of tensile strength and evaluated, comparing test results with the strength of an unexposed, “control” sample. We prefer “application” testing to chemical analysis of independent chemical agents done by referencing various charts or technical bulletins. Application testing (where the rubber meets the road) will also provide more accurate information on the cumulative effects of multiple chemical agents. We will match your efforts and assist you in determining the most suitable materials for your specific application.
Conventional synthetic products should never be used at temperatures above 194°F/90°C or below -40°F/-40°C. Temperature exposure outside the acceptable range must be considered and evaluated by a qualified person.
Continuous exposure to sources of ultraviolet light affect the strength of synthetic products in varying degrees from slight to total degradation. Factors which play a part in the degree of strength loss are length of exposure, sling construction and design. Other environmental factors such as: weather conditions, elevation and geographic location also affect the degree of degradation.
Exposure to sources of ultraviolet (UV) light affects the strength of synthetic products in varying degrees from slight to total degradation. Factors which play a part in the degree of strength loss are length of exposure, sling construction and design. Other environmental factors such as weather conditions, elevation and geographic location also affect the degree of degradation./
The Web Sling and Tie Down Association (WSTDA) conducted tests to determine the affects of strength loss, as a result of ultraviolet (UV) exposure. The report, WSTDA-UV-Sling-2003 is available at www.wstda.com
Many different variables were analyzed in slings that were exposed for a period of 36 months. Nylon and polyester endless slings featuring: treated and untreated webbing, 6800 Lbs. (class 5) and 9800 Lbs. (class 7) materials and single and double ply constructions were evaluated.
Initially, nylon web slings lost strength at a slower rate, when compared to polyester slings, but continued to lose strength as exposure time was extended. The loss of strength for nylon slings can be 40 to 60% after exposure periods ranging from 12 to 36 months.
In the first year of the study, polyester web slings lost strength at a greater rate, when compared to nylon slings. Loss in strength for polyester slings was approximately 30% after 12 months exposure. Polyester sling strength loss seemed to subside and level off after the initial 12 month period.
When slings are not in use, store them in a dark, cool, dry location, free from mechanical and environmental damage.
When not in use, store slings in a cool, dry, dark location, free of mechanical and environmental damage. The storage location should be ventilated and not exposed to heat sources, chemical exposure, weld spatter, grit, grime, foreign materials and splinters from grinding or machining.
Chemically active environments can affect the strength of synthetic products in varying degrees ranging from moderate to total degradation. Before slings are used, the chemical compatibility between the sling and the environment must be considered. Aluminum fittings should never be exposed to chlorine environments or cleaned with chlorine based cleaning solutions. Consult the sling manufacturer before purchase to evaluate chemical compatibility between slings, their components and the environment.
When nylon products are “wet” there is an approximate strength loss of 15%. This loss of strength is documented in the 1988 DuPont Technical Information Multifiber Bulletin X272, page 6. Nylon sling strength returns when the sling dries completely. Polyester and High Performance Fiber strength is unaffected by moisture absorption.
It is important to select slings and components possessing proper chemical characteristics, making them compatible with their environment. Nylon, Polyester, Aramid, Nomex®, Poly-Arylate (Liquid Crystal), Ultra High Molecular Polyethylene (UHMwPE) and K-Spec® fibers are ideal materials for synthetic slings because they offer varying degrees of resistance and compatibility with different chemical agents.
PERFORMANCE CHARACTERISTICS OF SYNTHETIC FIBERS
Nylon is popular and general purpose synthetic fiber which is unaffected by common grease and oil. Nylon products have good resistance to aldehydes, hydrocarbons, ethers and some alkalis, while degradation ranging from none to moderate occurs with exposure to certain alkalis. Nylon products are not suitable for use with acids and bleaching agents. Exposure can result in degradation from none to total. Dilute acids, such as, hydrochloric and sulfuric in 10% concentrations at room temperature cause significant strength loss in 10 hours.
Solvents for nylon include: concentrated formic acid, phenolic compounds and calcium chloride in methanol at room temperature, hot solutions of zinc chloride in methanol, benzyl alcohol at the boil, hot solutions of calcium chloride in: glacial acetic acid, ethylene chlorohydrins and ethylene glycol.
Nylon is not significantly affected by compounds of the following classes: alcohols, dry cleaning solvents, halogenated hydrocarbons, ketones, soaps and synthetic detergents or water (including sea water).
Nylon products lose 15% of their Work Load Limit when wet. The acceptable temperature exposure range is -40°F/-40°C to a maximum of 194°F/90°C. Stretch at Work Load Limit is approximately 8-10% for slings with treated webbing.
All webbing will become shorter, over time. Nylon webbing placed on a table, with no use, will shrink up to 5% in length after six months, as a result of the weave configuration. Dense weave webbing shrinks less than loose weave webbing. Nylon webbing will shrink more than polyester webbing. Other factors that affect shrinkage are humidity, temperature and usage.
Polyester is not significantly affected by most compounds of the following classes: alcohols, dry cleaning solvents, halogenated hydrocarbons, ketones, soaps and synthetic detergents or water (including sea water). Polyester also has good to excellent resistance to aqueous solutions of most weak acids at the boil and to most acids at room temperature, but is disintegrated by concentrated sulfuric acid (95%) at room temperature and exposure to alkalis. Polyester products also have some resistance to most aqueous solutions at room temperature, but are degraded by the same solution at the boil. Oxidizing agents and bleaching treatments ordinarily used by the textile industry do not degrade polyester fiber. Stretch at Work Load Limit is approximately 5-7% for slings with treated webbing. Polyester does not lose strength as a result of moisture absorption. The acceptable temperature exposure range is -40°F/-40°C to a maximum of 194°F/90°C.
Aramid fibers are resistant to most weak acids, alkalis, ketones, alcohols, hydrocarbons, oils and dry cleaning solvents. Strong acids, bases and sodium hypo-chlorite bleach attack Aramid fibers, particularly at elevated temperatures and/or high concentrations. Stretch at Work Load Limit is approximately 1%.
K-Spec® is a combination of High Molecular Polyethylene and Aramid fibers. Stretch at Work Load Limit is approximately 1% and the acceptable temperature exposure range is -40°F/-40°C to a maximum of 180°F/82°C. K-Spec® core yarn strength retention is based on test results of components at 150°F/65°C (or less) for 6 months. K-Spec® has a 100% strength retention when exposed to: age, 10% detergent solution, rot and mildew, sunlight and toluene; 99% retention when exposed to: acetic acid, gasoline, hydrochloric acid 1m, hydraulic fluid, kerosene and sea water; 98% retention when exposed to: 25% ammonium hydroxide, 10% hypophosphite solution, and 40% phosphoric acid; 97% retention when exposed to sodium hydroxide 5m; 95% retention when exposed to Portland cement, and 88% retention when exposed to Clorox® bleach and nitric acid.
Resists many chemical agents and retained 100% of the original fiber strength when immersed for 6 months in the following:
Clorox® degraded UHMwPE by approximately 10% after a 6 month immersion test.
Stretch at Work Load Limit is approximately 1% and maximum temperature exposure is 140°F/60°C.
Nomex® is resistant to most ketones, alcohols, dry cleaning solvents and many other organic solvents. Its acid resistance is superior to nylon, but is not as good as polyester. Nomex® shows good resistance to alkalis at room temperature, but is degraded by strong alkalis at higher temperatures.
Nomex® is compatible with fluorine-containing elastomers, resins and refrigerants at high temperatures and is resistant to fluorine compounds in concentrations usually encountered in stack gases from metallurgical and rock-processing operations.
The resistance of Nomex® to oxides of sulfur at temperatures above the acid dew point is superior to polyester. Below the dew point, concentrated sulfuric acid may condense on the fiber and cause a progressive loss of strength.