There’s a lot of different terminology and rules to remember about synthetic rigging and lifting slings – but Hercules SLR has you covered.
When you think of a heavy duty sling, you might wonder why a rigger would choose a synthetic material over something ‘heavy duty’, like chain. They exist for a reason—Some benefits of synthetic rigging and lifting slings include:
- Great for applications where steel or wire rope slings could damage a delicate load.
RIGGING AND LIFTING SLINGS | WHAT THEY’RE MADE OF
Synthetic slings, or textile slings are made out of fabricated materials like nylon or polyester. Colour codes are used to identify the synthetic sling’s material. The colour is identified by a label on rigging and lifting slings – These are:
- BLUE: Polyester (ES)
- GREEN: Polyamide (PA)
- BROWN: Polypropylene (PP)
In terms of their construction, synthetic slings are often known as web slings or round slings.
RIGGING AND LIFTING SLINGS | SAFETY TIPS
There are many safety tips to keep in mind when lifting with synthetic slings. Here are a few simple safety tips and tricks to keep in mind:
- Store synthetic slings in a cool, dry place that’s free from exposure to ultra-violet light, like sunlight.
- Never pull your sling from under a load
- If the tags/labels are unreadable, don’t use the sling
- Be careful when using the sling around sharp corners or edges—Sharp corners can tear the synthetic sling
RIGGING AND LIFTING SLINGS | INSPECTON
Synthetic slings should be inspected on a semi-regular basis. There are three types of inspection you must do with your synthetic sling(s)—These are:
1) INITIAL INSPECTION
Before using your synthetic sling, a designated person or the user must check the sling to make sure it’s the correct to use for the application, and to ensure the sling meets the manufacturer’s specifications. A designated person is someone who has a recognized degree or certificate in an applicable field (like rigging) or someone who has extensive knowledge, training, experience and has successfully demonstrated the ability to solve or resolve problems that relate to the application.
This inspection should happen whether the sling is new, repaired or altered in any way.
2) FREQUENT VISUAL INSPECTION
Whoever is handling the sling, should conduct a visual inspection(s) each time it’s used. Further conditions for frequent visual inspection is:
A) A visual inspection for damage shall be performed by the user or other designated person each date or shift the sling is used.
B) If the sling has any conditions that could cause hazard, the sling should be removed from service and not returned until it’s been approved by a designated person.
3) PERIODOC INSPECTION
Each part of the sling must be inspected individually—Take care to expose and examine all surfaces and individual component.
Periodic inspections should not exceed one year—Inspect your synthetic sling at least once annually. Inspection frequency is based on how often slings are used, the kind of lifts being made, experience gained on service life of slings and how severe service conditions are.
Severe service conditions are defined as:
- Normal service—Yearly
- Severe service—Monthly to quarterly
- Special service—This is recommended by a qualified person
When you inspect your sling, look for these conditions:
- Bent or twisted fittings
- Chemical damage
- Crushing or knots
- Cuts and broken stitching
- Exposed internal cover due to cut or abrasion
- Heat damage
- Holes, cuts, tears or snags
- Missing or illegible sling identification
- Severe abrasion
- Twin path tell-tails not extending 1/2″ past the tag area
- Ultra-violet ray damage
- Worn or broken stitching
RIGGING AND LIFTING SLINGS | KNOW YOUR ANGLES
What do we mean when we discuss sling angles? Sling angle is the space where the sling and the horizontal part of the load meet.
Rated capacity, rated load or working load limit refers to the maximum working load that the sling manufacturer says the sling can hold. The terms ‘rated capacity’ and ‘working load limit’ are commonly used to describe rated load. The angle is important as the sling angle creates tension, which can impact the rated capacity of the sling.
Safe sling angles are typically 45° greater from the horizontal point of the load.
When we talk about sling angles, it’s important to talk about sling hitches. Hitches refer to the different way a sling can be applied to a load. The angle of multi-leg slings will effect the rated capacity of the bridle or multi-leg sling.
The most common types of hitches found in rigging are:
- VERTICAL: Method of rigging a web sling where the load’s attached to one end of the web sling, and the other end of the web sling is attached to the lifting device.
- CHOKER: Method of rigging a web sling in which the web sling is passed around the load, then through itself, then attached to the lifting device.
- BASKET HITCH (90°): Method of rigging a web sling where the web sling is passed around the load, and both ends are attached to the lifting device. A method of rigging a sling where it’s passed around the load, then through one loop eye, end fitting, or other device, while the other loop eye or end fitting at the other end is attached to the lifting device. Any hitch less than 5 degrees from the vertical may be considered a vertical hitch.
The degree of the angle determines the rated capacity of the sling—To find out if a sling has the rated capacity you need for a lift, take the angle between the sling leg and the horizontal, then multiply the sling’s factor.
As the sling angle decreases, so does the rated capacity. Here’s a chart for example:
|SLING ANGLE DEGREES||LOSS FACTOR|
RIGGING AND LIFTING SLINGS: OTHER FACTORS THAT REDUCE CAPACITY
It’s important to remember that rated capacities are based on perfect conditions. There are many other factors that reduce capacity. These include:
- Swing: Suspended loads can swing, which place more dynamic forces on the hoist in addition to the weight of the load. These additional forces (see point below) are difficult to quantify and account for, and could cause tip-over of the crane or failure of hoisting hardware. The force of the swinging causes the load to drift away from the machine, which increases the radius and side-loading on equipment. Keep the load directly below the boom point or upper load block. This is best accomplished by controlling the load’s movement with slow motions.
- Condition of equipment: Again, WLL and rated capacities are based on perfect conditions – this includes equipment and hardware. Damaged equipment should be taken out of service immediately.
- Dynamic forces: WLL and rated capacities are meant for static loads. Safety factor accounts for the dynamic motions of the load & equipment.
- Weight of tackle: Hoisting equipment’s rated capacity doesn’t account for the additional weight of blocks, hooks, slings, equalizer beams and other parts of the lifting tackle. The weight of these accessories combined must be added to the load’s total weight, the capacity of the lifting equipment including design safety factors and should be large enough to account for the extra load to lift.
RIGGING AND LIFTING SLINGS | TERMINOLOGY
Read on to discover MORE rigging and lifting sling vocabulary you need to know.
ABNORMAL OPERATING CONDITIONS: Environmental conditions that unfavourable, harmful or detrimental to/or for the operation of a sling, such as excessively high or low ambient temperatures, exposure to weather, corrosive fumes, dust or moisture-laden atmospheres and hazardous locations.
ABRASION: The mechanical wearing of a surface that results from friction with other materials or objects.
ANGLE OF CHOKE: Angle that’s formed with in a sling body as it passes through the choking-eye or fittings.
ASSEMBLY: Another word for sling.
AUTHORIZED: Approved by a duly-constituted administrative or regulatory authority.
BODY (SLING): The part of a sling between the eye(s), end-fittings or loop eyes.
BRIDLE SLING: A sling composed of multiple legs with the top ends gathered in a fitting that goes over the lifting hook.
D/d RATIO: The relationship between the curvative upon which the sling is used (D) and the nominal sling diameter (d).
DESIGNATED PERSON: Selected or assigned by the employer or employer’s representative as being competent to perform specific duties.
END-FITTING: Terminal hardware on the end of a sling. See sling.
EYE OPENING: The opening in the end of a sling of the attachment of the hook, shackle, or other lifting device or the load itself.
FABRICATION EFFICIENCY: The sling assembly strength, as a percentage of the material strength prior to fabrication.
FITTING: Hardware on the end of a sling, also known as a component.
GROMMET SLING: A type of endless sling.
LENGTH, SLING: The distance between the extreme bearing points of the sling.
SINGLE-LEG SLINGS WITHOUT END FITTINGS: Measured from pull to pull with or from bearing to bearing of eyes.
SINGLE-LEG SLINGS WITH END FITTINGS: Measured from pull to pull of end fittings or eyes.
LOOP EYE (WEB SLING): A length of webbing that has been that’s been folded back upon itself, forming an opening, and joined to the sling body to form a bearing surface.
PLY: A Layer of load bearing webbing used in a web sling assembly.
PROOF LOAD: The specific load applied in performance of the proof tests.
PROOF TEST:A nondestructive load test made to a specific multiple of the rated load of the sling.
SPECIAL OR INFREQUENT: Service that involves operation other than normal or severe, which is approved by a qualified person.
SPIRAL: A single transverse coil that is the basic element from which metal mesh is fabricated.
SPLICE (WEB SLING): The part of the sling that’s lapped and secured to become an integral part of the sling.
ASSEMBLY SPLICE (WEB SLING): Any splice that joins two or more parts of the sling without bearing any of the applied load.
LOAD BEARING SPLICE (WEB SLING): The part of a sling that is lapped and secured to become an integral load bearing part of the sling.
TRIANGLE CHOKER FITTING: An end-fitting for metal mesh or synthetic web slings; similar to the triangle fitting, except that is also a transverse slot through which a triangle fitting can be passed to facilitate a choker hitch on the load.
TRIANGLE FITTING: An end fitting for metal mesh or synthetic web slings, containing a single eye opening for connecting the sling to the lifting device.
YARN: A generic term for a continuous strand of fibers.