What Is Limiter Torque?

Whether you’re building an industrial-grade machine or a hobbyist with an electric arc welder, you’ll need a limiter torque to make sure that you’re not over-tightening the machine’s nut. It can be a daunting task to determine what a limiter torque is, but if you’re careful and you use the right tools, you’ll be able to measure it easily.

Shear-pin

Choosing the right type of limiter is important for protecting the expensive mechanisms on your machine. Torque limiters are usually made from hardened steel and are available in a variety of designs. Some are hydraulic while others are pneumatic. They can be mounted in a number of different positions, including horizontal, vertical, and inverted. It is important to select the right type of limiter for your machine before you start squeezing it into a tight space.
A shear pin, or shear-pin, is a shear-shaped metal or plastic pin that is inserted between the mating flanges of two rotating bodies. It may be hard to believe that a small piece of metal can provide a solid connection between the two rotating elements. In fact, a shear pin can provide a rigid connection between the rotating elements of a high-torque drive, such as a motor or a turbine.
The shear-pin’s main advantage is the ability to provide a sturdy connection between the two rotating elements. Shear-pins are especially useful for applications that require a high level of torque and rigidity, such as the coupling of a high-torque gearbox to a crankshaft or a turbine to a turbine rotor.
A ball detent, or BDM, is a common torque limiter device that uses hardened balls to compress a spring to transmit force. These devices are often found on conveyors, textile machinery, and printing machines. Ball detents are usually adjusted by a rotating collar. The ball detent is typically the tiniest of the plethora of limiter devices.
Other possible mechanisms include the aforementioned shear-pin and the more conventional sprockets. Unlike a shear-pin, sprockets are not suitable for coupling applications. In addition, a sprocket’s size is limited to a couple hundredths of a millimeter, whereas a shear-pin may be used in larger sizes. Nonetheless, the shear-pin’s main advantage is that it can be installed in a variety of different locations. This is important for applications where space is at a premium, such as on a conveyor belt or in a textile plant. It is also important to consider the number of pins required. Using the proper number of shear-pins can ensure maximum efficiency and capacity within the confines of a machine’s footprint.

Friction-disc

Typical torque limiters for coaxial shafts comprise a stack of interleaved discs interconnected with torque pins. This allows for a significant increase in the surface area of the discs. It also minimizes bearing and spline wear. The stack of discs is alternately connected to the housing and a second shaft. The rotation of the discs enables the torque load to be transmitted from the input hub to the output hub.
The discs of the stack are supported by an annular ring. This ring receives the spring piston assemblies that engage the discs. The spring pistons compress the springs and force the discs into frictional contacting engagement. This precompression allows for substantially constant force characteristics. The spring piston assemblies also reduce the characteristic force by 10% over the life of the torque limiter.
The assembly has a wear indicator pin 42 extending from the back of the spring pin assemblies. This pin is used to test the torque limiter’s capabilities. It is also indexed with ball detents. It is recommended that you run the torque limiter at 500 revolutions at 50-60 rpm to ensure that the torque limiter performs as expected.
The torque limiter comprises an input hub 72 in communication with an output hub 74. The input hub is typically connected to a power source. It is arranged so that the output hub is aligned with a first end plate 90 coaxial with the output hub. The keeper plate 76 is also attached to the output hub.
The input hub comprises a cylindrical housing 18 with a cylindrical inner separator disc 52 affixed to the drive shaft. The inner disc 52 serves as a separator plate between the disc stack 40. This inner disc minimizes spline and bearing wear and minimizes the torque load required to rotate the discs. The axial thrust load is carried through the housing and is transferred to an annular disc 24. The additional thrust load is carried through the end plate 54.
The outer diameter of the friction discs has tabs that secure the discs to the SLEEVE. A precision machined pilot is incorporated in the SLEEVE for ease of use.

Synchronous magnetic

Unlike mechanical torque limiters, synchronous magnetic limiters transmit torque through thin plastic wall instead of metal shafts. Because of the difference in design, they may have more backlash than mechanical types. However, the torque limiter can be set dynamically and reset automatically, and some are equipped to uncouple the load completely in the event of overload.
There are three types of synchronous magnetic limiters. These are the permanent magnet, the magnetic-particle, and the disconnect types. The permanent magnet type uses mating magnets on the disc faces. The magnetic-particle type is similar to the friction plate clutch. It has a non-ferrous output rotor cup that generates coupling torque through eddy currents. Disconnect type torque limiters include synchronous magnetic, pawl and spring, and shear pin.
Permanent magnet synchronous motors are used for variable-speed drives. They are highly efficient and have low power losses in the rotor. They also deliver quick response and low ripple. A four-pole synchronous motor with 400 W power has a rotational speed of 1500 rpm. It uses a stator of asynchronous motor type Sh 71-4B.
Magnetic-particle torque limiters have a drive side and a driven side. The drive side contains a thin plastic wall that transmits the torque. The driven side contains a hollow shaving-filled housing. It also has loose shavings that rest inside the shaft detents. It can be configured to statically or dynamically set the torque.
Ball detent limiters are also available. These have balls that rest inside the shaft detents. They are usually adjustable by a rotating collar. If over-torque occurs, the balls are pushed out of the shaft detents.
Shear-pin limiters use pins that are embedded in the faces of the disc. When the assembly exceeds the design torque, the pins break. They can’t transmit torque through jams, but they can be secured. They may be set to reset automatically or manually.
Some disconnect torque limiters are designed to have multiple detent positions, but they may have a snap-acting spring that requires a manual reset. They can also be designed to uncouple the load completely in the case of overload.

Maintenance and repair scheduling

Managing maintenance and repair scheduling for limiter torque is a crucial task. Since there is no way to predict when a torque-limiting instrument will fail, a proper maintenance and repair schedule must be used to prevent a sudden failure.
The useful life of a torque instrument is determined by various factors. This includes the design of the instrument, the condition of the instrument during its life, and the conditions of the environment in which the instrument is used. It is also important to have a replacement program and a retirement program for the instrument.
Some of the factors that can affect the useful life of the instrument include wear, lubricant breakdown, and spring relaxation. It is also important to maintain the proper torque on fasteners. This is important for safety and for ensuring the proper driving condition of the vehicle.
In heavy-duty high-cycle operation, proper maintenance is critical. Torque tools are also useful to help mechanics apply torque correctly. The repair manual of each vehicle will have torque values for all of the fasteners. The manufacturer will also publish repair manuals for each vehicle. This will include the torque value for each fastener, along with the proper bolts.
A maintenance and repair schedule should be based on the operating environment and the vehicle application. Maintenance tasks will be listed and intervals will be given. It is also important to consider the skill level of workers involved in the maintenance and repair of the equipment. Some tasks may be more advanced and require highly skilled workers. However, less skilled workers may not be given high-priority tasks.
It is also important to include notes from past technicians and procedures from the maintenance manual. This will help make the task easier to perform. You may also want to contact a third party parts supplier to purchase repair manuals.
To ensure the reliability of your device, you need to use a conditioning cycle before the final calibration. This will increase the reliability of the device and decrease the risk of failure.
Finally, you need to consider how the instrument will perform in the field. This is known as the duty interval. Duty intervals measure the performance of the instrument during the instrument’s life.

editor by CX 2024-03-26