How to Examine Air Chain Hoists
When it comes to examining, testing, and re-certifying all types of lifting equipment, each company has their own standards. Such is the case for air chain hoists.
Most companies typically follow the American Society of Mechanical Engineers or ASME guidelines, which are utilized to ensure maximum efficiency and safety when using lifting equipment.
“A proper examination of the air chain hoist follows immediately after the client has returned it. To properly inspect the hoist, the chain is stripped from the hoist and the motor is taken out. The motor veins are reviewed for wear and if none is found, then the motor is lubricated and reinstalled inside the hoist. Next, they inspect the break disks for wear, as well. If that also clears inspection, then the chain is placed inside the hoist once again and ready to be tested.”
Different ways to test air chain hoists
Testing the air chain hoist is done in two fashions – dynamic and static. Dynamic and static are not vastly different from one another.
The main difference is that a static load test is comprised of a stationary overload load test at 125% of equipment rated capacity. This is conducted to verify the structural and mechanical integrity of the lifting equipment. The technician takes a digital load link and hook it up the hoist, and test it to 125% of rated and stamped capacity. Once it’s pulled to 125% of capacity, the technician waits 10-20 seconds and if there is no failure then it passes under load testing. This is currently the standards set by OSHA and ANSI regulations.
A dynamic load test consists of performing an overload test at 125% of rated capacity, and testing the following functions where applicable: hoisting and lowering of load and hoist brake hold. The same test is performed as the static load test except that now, the hoist is hooked up to a computer. The computer twill show a graph of force over time. Once it goes up to 125%, the technician can manipulate the hoist up and down to see if there are any deficiencies.
Each hoist, depending on the tonnage, will be given a dynamic or a static load test. ASME calls for at least a static test to be performed in order to meet their guidelines. Performing a dynamic test is considered beyond their standards.
Methods of protection for hoists
Although it is not a requirement of ASME, hoists can feature one or two methods of protection. One is an overload clutch, and the other is a Delta P. The Delta P measures the pressure differential that’s coming into the motor and compares it with the pressure that’s exhausting the motor. The differential between pressures is proportional to the load that’s on the hoist. The differential will trip the value and engage the break to protect the hoist.
The second method is the overload protection function on air chain hoists. In the US, this is considered an accessory to air chain hoists, but not a requirement. Some are designed with it while others are not. Air chain hoists with tonnages of 3-20 will have an overload clutch as a standard on the hoist. Hoists with 1-2 tonnages will not. The Delta P valve is considered an option on the 1/4th– 2 ton and on hoists of 20 tonnage or higher.
When it comes to any piece of lifting equipment, a proper examination of it is essential to guaranteeing a successful project. Give each air chain hoist a thorough inspection to meet the standards required for safety and efficiency.