More from: rigging supplies

How to Use Outrigger Pads the Safe Way

Outrigger pads are tools used to keep cranes and other pieces of heavy equipment from sinking into the ground during lifting. Anyone experienced with rigging is probably familiar with the pads to at least some extent. We sell outrigger pads as part of our inventory of rigging supplies.

We cannot stress enough the need for safety when deploying outrigger pads. As with everything related to rigging, there are safe and unsafe ways to deploy them. Relying on general rules of thumb or intuition doesn’t cut it. To be safe, you have to do things the right way.

Government Regulations

The place to begin here is with government regulations. According to OSHA, safety is always a requirement. OSHA 1926.1402 states that, in all instances in which a crane or other lifting equipment is used, the ground on which the equipment is placed must be firm, sufficiently drained, properly graded, and able to support blocking, cribbing, and outrigger pads.

OSHA regulations relate mainly to construction and industrial work. So for jobs outside their scope we look to ASME B30.5 code. This code has been approved by the U.S. government, making it legally binding. It states that any blocking or pads used to support heavy equipment must be sufficiently strong. They must be able to safely support floating and transmission of the load without excessive settlement, shifting, or toppling.

This is just a general outline of OSHA and ASME rules. For details, consult both documents online. They offer all the information you need for a safe lifting experience.

Working Load Limits

Next, it is important to know and understand the working load limits of your outrigger pads, blocking, or cribbing. The three models of outrigger pads that we sell have working load limits of 45,000, 55,000, and 60,000 pounds. All have a crush rating of 200 PSI.

These working load limits apply just to the pads themselves. They have nothing to do with the strength or support of the ground underneath. So just because you have an outrigger pad strong enough to handle the load you’re lifting doesn’t necessarily mean you’re good to go.

Making Some Calculations

Lifting safely requires a few basic calculations, beginning with the total amount of force the operation represents. Total force is really just the sum of all the ‘moving parts’, so to speak. Add together the weight of the crane, load, rigging equipment, and any accessories. The total weight equals the force of the load.

Next, you must calculate the amount of area needed to safely distribute the load across your outrigger system. For that, you’ll need to know ground (soil) pressure. The lift supervisor should provide you with that number measured as pounds per square inch (psi).

To determine area, divide the total force by the ground pressure. The resulting number will be the total area over which the weight will be distributed. Calculate the square root of that number and you’ll know how much area each of the four corners of your rigging system should cover.

In some cases, you may find your outrigger pads are sufficient in and of themselves to carry the load. Other cases might require additional blocking or cribbing underneath the pads. Just make sure you get it right one way or another.

Feel free to contact us if you have questions about our outrigger pads. Also remember that we carry a full line of rigging supplies. Whether you need slings, straps, blocks or hooks, Mytee Products probably carries it. And if we don’t, contact us anyway. We might be able to procure what you’re after.


Rigging Science: The Physics Behind the Block and Tackle

Mytee Products carries a full inventory of rigging supplies covering everything from blocks to turnbuckles and shackles. All of that is well and good, but sometimes it is helpful to understand the physics behind rigging principals. Understanding makes for safer lifts.

In light of that, we thought it might be interesting to discuss the physics behind the block and tackle principal. The block and tackle represents one of the easiest ways to lift extremely heavy loads with very little force. Block and tackle setups have been used for centuries by cultures all over the world.

The Block and Tackle Defined

A block and tackle isn’t a single piece of equipment. Instead, it is a particular kind of rigging set-up that includes multiple pulleys and some sort of means to lift the load – be it rope, wire, chain, etc. The most basic setup utilizes at least two pulleys with a rope or wire running between them.

The pulleys in a block and tackle system can be located close together or at a distance. Locations are chosen based on the nature of the lift. The pulleys on a crane might be close together while those in the warehouse rigging system are farther apart.

The Principle of Lifting Force

Physics dictates that a certain amount of force is required to lift a load off the ground. The heavier the load, the more force required. The lifting force has to be either equal to or greater than the weight of the load.

For example, imagine you are lifting a 200-pound load using a single pulley and a 200 ft. rope. You have to apply a minimum of 200 pounds of force in order to get the load off the ground. All 200 pounds will be carried by that single pulley. Also note that the amount of force you need is inversely related to the length of your rope.

If your rope is 100 feet long, more force will be required. The opposite is true if your rope is longer than 200 feet. What does this tell you? It tells you that a longer rope and more pulleys should require less lifting force from you.

Sharing the Load among Blocks

Remember that a block and tackle system utilizes multiple pulleys (or blocks) for lifting. Each of those blocks takes some of the weight of the load. So once again, let us assume a 200-pound load and two blocks in your system. Each block carries half the weight, or 100 pounds. Using the same 200-foot rope now means you only have to apply 100 pounds of lifting force instead of 200.

Introduce a third block into the system and you reduce the total weight carried by each block yet again. Instead of 100 pounds per block, you are now in the neighborhood of 70 pounds.

In theory, you can continue adding blocks and lengthening the rope to make your load even easier to lift. In practice though, there is a tipping point. Additional blocks and longer rope create resistance. Make your block and tackle system too big and the amount of resistance in the system could make it impossible to lift the load anyway. So there is a balance between distributing the weight and minimizing resistance.

Distributing the Load

The simplest way to understand the physics of a block and tackle system is to understand that each block in the system takes part of the load. It is all about load distribution. Greater distribution means less lifting force to get a load off the ground. That’s about it in a nutshell.


Wire Rope Nomenclature for Beginners

Now that Mytee is offering rigging supplies, we are beginning to see an increase in the number of questions for these products. Our customers need to know what they are purchasing before they complete their purchase, and want to ensure that all their questions are answered correctly. For example, we sell a number of different kinds of wire rope for rigging.

wire-rope

Two examples of wire rope products would be our peerless galvanized aircraft cable and peerless fiber core wire rope. If you were to view either of these products on our site, you would see a description complete with a set of numbers that you might not understand. Unfortunately, there is a certain nomenclature assigned to wire ropes that you may not be familiar with unless you have extensive experience with rigging.

Wire rope is normally identified using three features:

  • The number of wires in each strand
  • The number and/or configuration of strands in each rope
  • An indicator of the construction or arrangement of the wires in the rope.

For example, a product designated as ‘6×7 fiber core’ would consist of six strands of seven wires per strand, surrounding a core made of a synthetic fiber. To an experienced rigger, the product designation would be enough to tell him or her whether the product is suitable for his/her purposes or not. Someone who does not possess the same kind of knowledge might look at the product designation and think nothing of it.

Different Rope Cores

The core, or center of a wire rope, indicates how that rope is used and what its capabilities are. Riggers have to fully understand load requirements in order to know what kind of core is most suitable to the needs of the job at hand. There are three primary core options to choose from:

  • Strand Center – This core is made up of a strand of wires either similar or identical to the outer strands. It is the weakest kind of core, yet it is still strong enough to be used for guy wires, suspension bridge cables, and aircraft cable. It is the core of choice for applications in which crushing weights are a concern.
  • Fiber Center – This core consists of pre-lubricated plastic fibers made of a material such as propylene. The advantage of a fiber core is that it stands up to tremendous amounts of pressure. It also tends to do very well against caustic substances that might be damaging to a strand center rope. It is not a good choice for applications involving crushing weight.
  • Independent Center Core – Known formally in the industry as IWRC (independent wire rope center), this kind of core is essentially a separate wire rope made with its own strands and core. Wire ropes made with IWRC cores are the strongest of all. They are generally accepted to be 7% stronger than comparable strand center wire ropes. The increased strength makes IWRC the preferred core for wire ropes that will be used to carry heavy loads.

One last thing riggers need to consider is the lay of wire strands within a rope. A regular lay rope is one in which the individual strands of the rope run opposite to the rope itself. A lang lay rope consists of strands that are laid in the same direction as the completed rope.

Finally, the alternate lay configuration utilizes equal numbers of regular and lang lay strands, woven together alternately. You can see this alternating pattern by laying the wire rope on a flat surface and inspecting the individual strands.

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