Friday, May 28, 2010

Understanding the Wire Rope The most important component of your crane is your wire rope. Therefore it is vital for you to understand the construction of a wire rope. If you know how your wire rope is made then you can properly inspect, and maintain it. It is easy to inspect if you know how to do it and what to look for. A wire rope is like a machine with all its components and make up. Here we will only cover the main points of a wire rope that will help you care for your wire rope. There are three main components of your wire rope. First you have your core (d). Your core is then surrounded by tiny strands (F) made up of several wires (E). When you’re inspecting your wire rope you do not need to rag the rope. Rag, is terminology that means to take a rag and wrap it around the wire rope and then operate the hoist so the wire rope feeds through the rag. This is left for the professional inspector to do. This can be dangerous if you have not done this before. The rag can tear out of your hands and you have the potential to cut your hand on a bad wire rope or even worse pull a body part into the drum of the hoist. DO NOT RAG YOUR WIRE ROPE. Save it for the professionals.
Per CALOSHA standards you should change your wire rope when you have 6 randomly distributed wires in one lay or 3 broken wires in one strand.
Another vital piece of information that you should know is how a wire rope is classified. Most wire ropes you will see on overhead cranes are 6X37. This means that it has 6 strands, and 37 wires per strand. The wires can fluctuate per strand and still be classified as a 6X37. According to Southwest Wire Rope it can typically run from 27 to 49 wires. There are several different classifications such as 6X19 which is the next classification down from 6X37 or even 6X61 which is the next classification up from 6X37. A wire rope is also classified based on the lay of the wire rope. A wire rope is either a right lay wire rope or a left lay wire rope. You can tell this by taking hand a grabbing the wire rope. If you take your left hand and wrap your hand around the wire rope and the strands are going in the same direction as your thumb then it is a right lay rope. Same as if you take your right hand and wrap it around the wire rope, if you’re the strands go in the same direction as your thumb then it is a left hand lay wire rope. When you order your wire rope you should be purchasing an OEM wire rope from your crane parts supplier. For your own information it is important to understand the types of lays in your wire rope. Most cranes will have regular lay wire ropes. However there are circumstances that you will find other types of wire ropes on your crane. If you look at a regular lay wire rope the wires are almost perpendicular from the lay of the wire rope. However on a Lang Lay the wires are going along the same pattern as the lay of the wire rope. Please see the below picture provided from They also list another type of lay which they call a reverse lay. I am more familiar with the term alternate lay. An alternate lay is when the wire rope switches back and forth from regular lay on one strand to Lang lay on the next strand. Again you will mostly be seeing regular lays on overhead cranes. It is good to know though that there are different types of lays of a wire rope. The core of the wire rope will either be made up of a fiber or it is made up of steel. If it is a fiber core it is listed as a FC. If it is a steel core then it is classified as an IWRC. There are benefits to both types of cores. A fiber core is more flexible and a steel core is stronger than the fiber core. It all depends on the use of the wire rope that would require a FC or a IWRC wire rope. Most cranes will have a IWRC unless it is a class A crane. Lastly you should familiarize yourself with lubricating your wire rope. Wire rope requires a periodic lubrication. The frequency is dependent upon the use of the crane, location of the crane, and the lubrication being used on the crane. You should be using a pliable type of lubricant. Do not use anything that dries on the wire rope. This does not allow for the entire wire rope to be covered in lube. You want to use a lube with a thick viscosity so it will reduce friction on the sheaves and drum, but not too thick that it does not get in between the strands of the wire rope. Most hoist manuals will tell you what type of lubricant to use on your equipment. It is best to follow the OEM guidelines. If you have a crane company working on your crane they will be using OEM lubricants on most crane components, however they may have a lubricant that they use for your type of wire rope. If you understand the above, you should go to your crane and see if you can tell what kind of wire rope you have and if it is lubricated or not. Ensure that the wire rope is being checked each shift before use, every month, quarterly, and annually. This of course is dependent upon frequency of use. Remember not all wire ropes are the same, and you cannot put any wire rope on a hoist. It has to be specified by the manufacturer. Now you understand the makeup of a wire rope and can properly identify a wire rope and you should when to change them. This will make your crane safer and more reliable.

No comments:

Post a Comment