CHAIN BLOCK

CHAIN BLOCK

The most important thing to remember is that heavy items have mass and mass equals energy. It may not be obvious but you know if you drop something heavy on your foot it will hurt. But it may do more than hurt. An anvil, swage block or milling vise dropped on one's foot could break numerous bones, disable and cause considerable expense.

There are three types of chain hoist. Differential,

Lever Ratchet, and

Handchain.

Differential HoistsThese use a continuos loop of chain and a double chainwheel at the top with different number of pockets on the two sides. The lower "hook" wheel has grooves to ride on the chain but no pockets. As the chain is pulled around the inner load loop gets smaller or larger by the difference in the number of pockets on the chainwheel (the differential). As the lifting loop gets shorter the hand loop gets longer and vise versa. This is a bit of an inconvenience but the mechanism is as simple as they get.

Differential HoistsLever Ratchet HoistsThese are small portable units with capacities up to 5 tons but the common ones are rated 1/2 or 1 ton. The ratchet handle operates simple gears that pull a short load chain. The load is supported by a disk type friction brake similar to an automotive clutch disk held by a paw and sprocket (ratchet). Lifting rotates the brake/clutch on the ratchet. Lowering releases the pressure on the brake via a multi-lead screw similar to a brake Bendix.

Lever Ratchet HoistsHand Chain Hoists (standard chain hoists)These operate like the ratchet hoists above except a chain wheel and loop of hand chain turns the gearing. A brake holds the load and a ratchet prevents the brake from rotating one direction. The chainwheel rides on a screw that loosens the brake when the chain is pulled in the lowering direction. Most have planetary gearing on the brake wheel. Chain hoists are made with straight pulls and compound pulls up to 10 tons or more. Chain hoist are made in steel, portable aluminium housings, spark proof materials and corrosion resistant materials.

Hand Chain Hoists

Common Features and ProblemsHigh quality hoists have ball thrust bearings in the hook to allow rotating the load.Load hooks have openings parallel to the back. Properly rated load hooks that have been overloaded will spring open and not be parallel.The brakes in industrial duty hoists are large and sufficient to support the load. A two ton hoist has an 8" to 10" diameter brake. Small import 2 ton hoists have small 3 to 4 inch brakes that are patently dangerous. They will slip under partial load without operation then due to heat rapidly slip more. These are dangerous junk that have no place in a safe shop.

Hoist Maintenance and InspectionChain hoists are durable and long lasting. The only regular maintenance is inspection, cleaning and lubricating. Chains should be kept clean and rust free. There are only a few bearing points that require oiling but these often require dismantling the hoist. Depending the use this should be done once a year or two. Since these devices have gears it is important to keep them sand and grit free. To clean the gears requires dismantling. Afterwards they should be greased with a tacky high pressure lube like Never Seize or gear grease.Hoists that slip should be tagged "out of order" and repaired if possible. If not they should be scrapped. Chains that are worn, kinked or stretched should be replaced. Load chains have gently curved sides that when overloaded become straight and sometimes stiff to flex. Stretched, straightened chains should be scraped and replaced. Load chains on hoists that have been stretched will not run smoothly on their blocks. Snapping or popping chains are an indication of overloaded chains.Safety Factors and TestingTraditional European and North American load lifting equipment has always had significant safety factors. Most steel crane and hoist parts are rated to be loaded to a maximum of 10,000 PSI at 1.5 to 2 times the rated load. This allows almost all parts to be safely made of mild steel. But then the parts are often made of steels that have five to ten times the strength of mild steel thus having huge safety factors. These 15 to 20 to one safety factors are what allows load lifting equipment to snag or catch a dropping load and safely absorb the inertia of such over loading.These safety factors should never be assumed or taken advantage of. The basic 1.5 rating is the amount of test load that is periodically put on industrial cranes to test them. Private owners and small shops should also periodically inspect and test their equipment to full or 1.5x capacity and record the test.On our large 10 Ton crane a 30,000 pound test load was not often available but occasionally we would have large assemblies that we normally did not lift. We would take advantage of these occasions and carefully lift them a few inches, have folks in the shop witness the lift then carefully put the load down. One thing we would have to be wary of was that at test load conditions the crane bridge would deflect more than that 1/4" or less and the trolley would try to roll to the center of the beam.Hanging HoistsHoists can be hung statically using a loop of chain or shackle. Movable hoists are hung on a trolley. In either case the support method should be rated for the capacity of the hoist.Trolleys should be hung on an appropriate beam. Crane or hoist beams are rated by deflection. Deflection should be 1/4" or less at the middle of the beam when fully loaded. This rule does two things. At 1/4" deflection trolleys do not roll down hill. At 1/4" deflection the strain on most beams is well within a safe range.OperationA chain hoist is operated by hand. An operator will pull down on one of the chain loops on one side of the chain. This will turn a pulley mechanism inside the chain hoist housing. When this pulley turns, it will lift up the end of the other chain which usually has a hook on the end. By pulling down on one chain, the manual hoist is actually able to increase the mechanical work that is being done. This is caused by the gear ratio inside the manual chain hoist DesignInside the chain hoist housing are two gears. One is smaller than the other. Most chain hoists use a 20 cm and 25 cm gear. The two gears are attached, so when one moves, the other moves. The chain is looped over the smaller gear, and then hangs down in a loop (the loop you pull on). The chain then continues on over the larger gear and down to a point or another loop, depending on the type of hoist you are using. The operator pulls on the section of chain which is looped over the smaller gear.

Gear RatiosWhen someone pulls down the chain as explained in Section 1, the smaller gear will turn. However, since it is smaller in size, it turns faster than the larger gear. It makes more rotations than the larger gear in a cycle. Since the larger gear is turning slower, it creates more force, in effect transforming the "pull" on the chain into a larger force. This is a mechanical advantage. An operator can put less force on the smaller gear, but still lift large objects. That is because the larger gear transforms that force into a much larger onMost chain hoists I've seen have two chains. You have the loop of pull chain which is the one you grab to move the hook. Next, you have the lifting chain. The end of the lifting chain typically has a swivel and hook on the end. The chain goes up to the hoist, and comes out the other side. Most of the time it loops down, then back up, and the end is secured to the hoist. When that loop of chain is gone, you're at your max height.OBJECTIVE:A pulley is a simple machine that makes it easier to lift objects, by requiring less input force. Learn about the mechanical advantage of pulleys, and how to calculate the mechanical advantage, based on the number of rope sections in the pulley system.

PULLEY

In the illustration to the right we have a rope attached to a load weighing 100kg. The rope has been passed through a pulley which is attached to an anchor point and returns back down to ground level.The amount of effort required to lift the load in this situation is 100kg so we have not formed any mechanical advantage. This system has a ratio of 1:1, additionally for every metre of rope that the user pulls through the system the load will be raised by a metre.All this system does is change the direction of where the effort needs to be put in, instead of pulling the rope in an upwards direction it can now be pulled downwards which is usually more efficient. This is commonly referred to as a directional or redirect pulley.In this situation the directional or redirect pulley and its anchor point will actually be feeling double the weight of the load, as there is the loads weight on one side and an effort of 100kg needs to be applied on the other side to raise the load.

If we take a 1:1 system and turn it upside down it will result in a 2:1 mechanical advantage. Instead of the pulley being attached to an anchor it is now attached to the load (pulley A).On one side of pulley A the rope has been attached to a fixed anchor point, the rope on the other side of pulley A has been sent back down to the ground via a redirect pulley (pulley B) where the user applies the effort to lift the load.As the load is being supported by two sections of rope (via pulley A), each rope will bear half of the loads weight or 50kg in this example. Pulley A is being subject to the full weight of the load (100kg).The directional or redirect pulley (pulley B) supports half of the weight of the load (50kg) on one side but an effort of 50kg is being applied on the other side to raise the load, so pulley B and its anchor are actually being loaded with 100kg.

With this 5:1 pulley system the user is required to apply an effort of only 20kg to lift the 100kg load. Notice that when the end of the rope is attached directly to the load this usually results in a mechanical advantage with an odd ratio.When the end of the rope is attached to a fixed anchor point this will normally result in a mechanical advantage with an even ratio.

Ablock and tackle[is a system of two or morepulleyswith aropeorcablethreaded between them, usually used to lift or pull heavy loads.The pulleys are assembled together to formblocksand then blocks are paired so that one is fixed and one moves with the load. The rope is threaded, or reeved, through the pulleys to providemechanical advantagethat amplifies that force applied to the rope.

Various ways of rigging a tackle.Mechanical advantageIffrictionallosses are neglected, themechanical advantageof a block and tackle is equal to the number of parts in the line that either attach to or run through the moving block -- in other words, the number of supporting ropes. The formula is derived usingvirtual workin detail in the article "mechanical advantage".An ideal block and tackle with a moving block supported bynrope sections has the mechanical advantage, where FAis the hauling, or input, force and FBis the load.The mechanical advantage of a tackle dictates how much easier it is to haul or lift the load. A double tackle has a mechanical advantage of 4, so it will be able to lift a 100N load with only 25N of tension on the hauling part of the line.Ideal mechanical advantage correlates directly withvelocity ratio. The velocity ratio of a tackle refers to the relative velocities of the hauling line to the hauled load. A line with a mechanical advantage of 4 has a velocity ratio of 4:1. In other words, to raise a load at 1 metre per second, the hauling part of the rope must be pulled at 4 metres per second. Therefore the mechanical advantage of a double tackle is 4.

A pulley, also called a sheave or a drum;Sand Castingmethod. Generally use gray iron or ductile iron material to cast pulley. We also can supply cast carbon steel pulley.

A pulley, also called a sheave or a drum, is a mechanism composed of a wheel on an axle or shaft that may have a groove between two flanges around its circumference. A rope, cable, belt, or chain usually runs over the wheel and inside the groove, if present. Pulleys are used to change the direction of an applied force, transmit rotational motion, or realize a mechanical advantage in either a linear or rotational system of motion. It is one of the six simple machines. Two or more pulleys together are called a block and tackle.Our manufacture processes:1.Sand Casting, ResinSand Casting2. Investment Casting, Lost Wax Casting or Precision Casting3. Lost foam casting4. Die casting.5. Permanent Casting.6. CNC Machining.

The material included: cast gray iron, ductile iron, carbon steel, stainless steel, malleable iron ,brass alloy and aluminum alloy.Sand Casting is the most commonly used Casting Process, in the entire Casting Industry.The Sand Casting ConceptThe top and the bottom of the mold form the flask. This top and bottom, are also called the flask assembly, and this flask assembly "holds the whole thing together." The upper or top-most section of the flask is called the cope, while the bottom of the flask is called the drag. There is always an impression device, in the middle of the flask assembly. This is called the pattern. The sand around the pattern is called the, holding medium.These are the basic, universal casting components, which can be applied to all Casting and Molding Processes.To cast an object, the mold maker, uses the pattern to make the impression in the holding medium, the sand. He then sets the pattern aside. At that point, the molder closes the cope and drag, to complete the flask, and forms the mold, with the impression of the pattern captured in the sand. What the mold maker wants, is the potential "CASTING" or the void left from the impression of the pattern, in middle of the sand. To get that "CASTING," the mold maker fills that void with a molten material; which could be almost anything, but here just imagine the material is aluminum.

Casting a component

Wire ropeis a type ofropewhich consists of several strands of metalwirelaid (or 'twisted') into ahelix. Initiallywrought ironwires were used, but todaysteelis the main material used for wire ropes.Historically wire rope evolved from steel chains which had a record of mechanical failure. While flaws in chain links or solid steel bars can lead to catastrophic failure, flaws in the wires making up a steel cable are less critical as the other wires easily take up the load. Friction between the individual wires and strands, as a consequence of their twist, further compensates for any flaws.Wires:Steel wires for wire ropes are normally made of non-alloy carbon steel with a carbon content of 0.4 to 0.95%. The tensile forces and to run over sheaves with relatively small diameters.StrandsIn the so-called cross lay strands, the wires of the different layers cross each other. In the mostly used parallel lay strands, the lay length of all the wire layers is equal and the wires of any two superimposed layers are parallel, resulting in linear contact. The wire of the outer layer is supported by two wires of the inner layer. These wires are neighbours along the whole length of the strand. Parallel lay strands are made in one operation. The endurance of wire ropes with this kind of strand is always much greater than of those (seldom used) with cross lay strands. Parallel lay strands with two wire layers have the construction Filler, Seale or Warrington.Spiral ropes:In principle, spiral ropes are round strands as they have an assembly of layers of wires laid helically over a centre with at least one layer of wires being laid in the opposite direction to that of the outer layer. Spiral ropes can be dimensioned in such a way that they are non-rotating which means that under tension the rope torque is nearly zero. The open spiral rope consists only of round wires. The half-locked coil rope and the full-locked coil rope always have a centre made of round wires. The locked coil ropes have one or more outer layers of profile wires. They have the advantage that their construction prevents the penetration of dirt and water to a greater extent and it also protects them from loss of lubricant. In addition, they have one further very important advantage as the ends of a broken outer wire cannot leave the rope if it has the proper dimensions.Safety:The wire ropes are stressed by fluctuating forces, by wear, by corrosion and in seldom cases by extreme forces. The rope life is finite and the safety is only given by inspection for the detection of wire breaks on a reference rope length, of cross-section loss as well as other failures so that the wire rope can be replaced before a dangerous situation occurs. Installations should be designed to facilitate the inspection of the wire ropes.Lifting installations for passenger transportation require that a combination of several methods should be used to prevent a car from plunging downwards. Elevators must have redundant bearing ropes and a safety gear. Ropeways and mine hoistings must be permanently supervised by a responsible manager and the rope has to be inspected by a magnetic method capable of detecting inner wire breaks.Load testingis the process of putting demand on a system or device and measuring its response. Load testing is performed to determine a systems behavior under both normal and anticipated peak load conditions. It helps to identify the maximum operating capacity of an application as well as any bottlenecks and determine which element is causing degradation. When the load placed on the system is raised beyond normal usage patterns, in order to test the system's response at unusually high or peak loads, it is known asstress testing. The load is usually so great that error conditions are the expected result, although no clear boundary exists when an activity ceases to be a load test and becomes a stress test.The Safe Working Load will normally be equal to the Working Load Limit but in some circumstances it may be less e.g. If the sling is used in choke hitch SWL=WLL x 0.8 .CautionIn all cases, where hooks or shackles are used, the WLL of the hooks and shackles shall not be less than that of the leg to which they are attached.Working LoadLimits TonnesOne Leg SlingTwo Leg SlingThree and Four Leg SlingEndless Sling - Choke HitchAngle tothevertical00 - 45>45 - 600 - 45>45 - 600Nominal rope Diameter mmTensile n/mm2Fibre CoreSteel CoreFibre CoreSteel CoreFibre CoreSteel CoreFibre CoreSteel CoreFibre CoreSteel CoreFibre CoreSteel Core819600.760.821.061.150.760.821.61.721.141.231.221.31919600.961.041.351.450.961.042.022.181.441.561.541.661019601.191.281.661.791.191.282.492.691.781.921.92.05Load Chart

Load securing, also known ascargo securing, is the securing ofcargofortransportation. According to theEuropean CommissionTransportation Department it has been estimated that up to 25% of accidents involving trucks can be attributable to inadequate cargo securing.[1]Cargo that is improperly secured can cause severe accidents and lead to the loss of cargo, the loss of lives, the loss of vehicles, or cause environmental hazards.

Cargo damage because of improperly secured cargoBlocking & BracingBlocking & bracing is a load securement method utilizing lumber and metal bars to reduce or inhibit front to rear shifting of freight/cargo. Plastic forms are also used. Fasteners]Depending on the type of load and the particular vehicle, largeboltsandnailsmay be used. These may be on the load itself or onwoodblocks used to brace the load.

DunnageMain article:DunnageDunnage for securing cargo has included scrap wood to fill voids in cargo, wooden boards forming "cribs", blocking and bracing, and modern mechanical, spring-loaded post-and-socket systems, Dunnage segregates cargo in the hold and prevents shifting of the cargo in response to ship or vehicle motions.Strapping Main article:StrappingStrapping is used to create a transportable unit.[citation needed]Types of strapping includesteel,polyester,polypropylene,nylon,paper, and composites. The type of strap used depends on the requirements, for example, strength, elasticity, ability to withstand various environments, easy of use, safety, and cost.All types of tensioned strapping, particularly steel, need to be handled carefully because of potential injury.

Lashing Lashing is the securing of cargo for transportation with the goal of minimizing shifting. Items used for lashing includeropes,cables,wires,chains, strapping, andnets. These items are anchored to the container and tensioned against the cargo. Another form of lashing used four devices attached to the top of each corner of a container.[3][4]Lashing is products and methods are governed by various authorities such as the Association of American Railroads (AAR) for rail transportation in North America, the international Maritime Organization (IMO) for ocean transportation and the National Motor Freight Traffic Association (NMFTA).

How to order Wire Rope SlingsPlease provide the following information while ordering Steel Wire Rope Slings to quote you the correct product & rate.Maximum load to be liftedType of material to be handledType of Sling to be usedHeight of liftSize & Type of terminal fitting attachmentsNumber of sling legs requiredDistribution of load on multiple slingsConstruction of the steel wire ropeDiameter / Capacity of steel wire rope.Refer Wire Rope Sling Capacity Chart.Effective Length requiredEye Length & WidthA reference to International Standard if anyTest Certificate

Leg AngleLoad Factor901.000851.003801.015To calculate the load on a particular sling leg proceed as follows:Take the total weight of the load and divide this by the number of legs supporting the load. For example, assume a 2000 pound load is to be supported by 2 legs of a sling. The above will give a total minimum weight on each leg of the sling of 2000 pounds divided by 2 legs or 1000 pounds.Determine the load factor by observing the load factor chart below. Ex. Assume that the leg angle will be 60. The load factor for 60 from the load factor chart is 1.154.Multiply the load factor times the minimum weight to be supported by the leg, i.e. 1000 pounds times 1.154=1154 pounds. The rated sling capacity needed is then 2308 (1154x2) pounds in basket capacity to safely lift the 2000 pound load.

To calculate the load on a particular sling leg proceed as follows:Take the total weight of the load and divide this by the number of legs supporting the load. For example, assume a 2000 pound load is to be supported by 2 legs of a sling. The above will give a total minimum weight on each leg of the sling of 2000 pounds divided by 2 legs or 1000 pounds.Determine the load factor by observing the load factor chart below. Ex. Assume that the leg angle will be 60. The load factor for 60 from the load factor chart is 1.154.Multiply the load factor times the minimum weight to be supported by the leg, i.e. 1000 pounds times 1.154=1154 pounds. The rated sling capacity needed is then 2308 (1154x2) pounds in basket capacity to safely lift the 2000 pound load.