Pneutorque® Pneumatic Multipliers

What is a Pneutorque Pneumatic Wrench?

The Pneutorque consists of a robust air motor driving a Norbar multiplier with three or more stages of epicyclic gearing.

Torque control is achieved by adjustment of the air pressure. An air pressure versus torque graph and a calibration certificate is supplied with each tool and allows specific torque values to be set. For more critical applications, Pneutorques can be fitted with a torque transducer and the precise torque output displayed.The tool can then be shut off at the desired torque either manually or automatically using suitable control circuitry.

Why use Pneutorque Pneumatic Wrenches?

Hand operated torque multipliers are ideal for low volume or intermittent use or when there is no power source available. However, for production lines or whenever a large number of bolts is involved, a powered multiplier will save a considerable amount of time.

Pneutorque operation is quiet – less than 85dB(A) with absolutely no impacting.These two factors make Pneutorques comfortable for the operator to use, reducing fatigue and consequently increasing safety.

Pneutorques provide accurate torque control – on a given joint they will stall repeatably to within ±5%. Using electronic shut off, this repeatability can be improved to ±2%.

Summary of Pneutorque Advantages

  • Sound pressure level does not exceed 85dB(A) when tested in accordance with ISO3744:1994.
  • No impacting means less damage to the tool, socket and bolted assembly.
  • Less operator fatigue, results in increased safety.
  • Powerful – models available up to 300,000 N.m (220,000 lbf.ft).
  • Repeatability of ±5% for accurate torque control.
  • A wide range of attachments and accessories make Pneutorques adaptable to many applications.

Pneutorque Applications

The smooth and continuous torque output of the Pneutorque makes these tools suitable for a wide range of bolting and non-bolting applications.

Bolting

Pneutorques are ideally suitable for tightening and untightening bolts of up to 150mm diameter.The following is just a small selection of applications:

  • Wheel nuts on trucks, buses and large machinery.
  • Structural steelwork.
  • High pressure joints eg. Pipelines, boiler feed pumps and pressure vessels.
  • Engine head bolts.
  • Injector heads on plastic injection moulding machines.
  • Heat exchangers.
  • Heavy vehicle production eg. Chassis and suspension bolts.

Non-bolting

Whenever a high continuous torque is needed, Pneutorques can be used as the power source.Typical applications include:

  • Ball valve operation.
  • Powering wagons and gantries.
  • Barring of large diesel engines (turning the crankshaft) during build.
  • Weld testing by applying test torques.
  • Roller adjustment in steel mills and paper mills.
  • Valving of gas bottles.

Torque Reaction

Principles of Torque Reaction

Newton’s law dictates that for every applied force there is an equal and opposite reactive force. For applications requiring relatively low torques that can be applied with a torque wrench this does not present a problem as the reactive force is absorbed by the operator. However, if the desired torque necessitates the use of a multiplier, the resultant reactive force can only be absorbed using an appropriate reaction device.

For this reason all Norbar multipliers are supplied with a reaction plate or reaction foot fitted as standard.

All of the standard reaction plates and feet illustrated have been designed to enable the multiplier’s use in a variety of environments but, due to an infinite number of bolting arrangements, it is impossible to have one reaction device that will satisfy every customer’s requirement.

What to do if the standard reaction device is not suitable
For those applications that do not permit the use of a standard reaction plate the customer has three options.

Norbar or an authorised Norbar distributor will design and manufacture a special purpose reaction plate to the customer’s requirements.
The customer can modify the standard reaction plate to suit his requirements.
The customer can fabricate his own reaction device after liaison with Norbar’s technical department or a Norbar distributor.
Customers wishing to either modify the original reaction plate or fabricate their own device should read the information on page 63 to avoid common torque reaction problems.

Torque Reaction

Avoiding Torque Reaction Problems

It has already been mentioned that the reaction force is equal to the force being applied. However, the magnitude of the reaction force is dependent upon the perpendicular distance between the point of reaction and the centre line of the multiplier, ie. the greater the distance the lower the force.

For this reason the point of reaction should be kept as far away from the centre line of the gearbox as is practical.

Customers using or modifying reaction plates for Standard Series multipliers up to a capacity of 3400 N.m should note that if the reaction is taken on the radiused part, the reaction force is perpendicular to the tangent of the curve. Consequently, the further around the radius the reaction is taken, the smaller the perpendicular distance and therefore the greater the force.

Although a longer reaction plate may mean lower forces, the bending moment close to the multiplier will increase.

Customers extending the length of Norbar’s standard reaction plates should be aware that an increase in overall length will result in a larger induced bending stress and should not assume that because the reaction plate is strong enough at one length it will remain so when extended.

Excessive side loading, resulting from poor reaction, increases frictional forces inside the multiplier.This can lead to lower multiplication ratios (outside ±4%).

Points to remember

Take the reaction as far away from the multiplier as practical.
Ensure that the reaction point remains square to the multiplier wherever possible as this will minimise any additional stress in the output square, which could result in premature failure. If the multiplier tilts under load, the reaction may not be square.
For applications that do not allow the reaction to be taken securely it is advisable to use a double ended or balanced reaction plate.

Reaction Force

When using Multipliers and Pneutorques the reaction point must be capable of withstanding reaction force.Therefore, great care must be exercised where reaction is taken when applying high torques to studs and bolts.

By using the following formula you can calculate the force at the point of reaction.The greater the distance the lower the force.

Pneutorque® Pneumatic Multipliers

Pneutorque® Standard Series : Models to 100,000 N.m, Single Speed
  • Models available for almost every bolting application, up to 100,000 N.m.
  • Forward and reverse operation.
  • Low operator fatigue – quiet, no impacting or pulsing.
Pneutorque® Standard Series : Models to 300,000 N.m, Two Speed - PT14 MTS

Two Speed Models offer all of the advantages of single speed versions but with the additional benefit of a run down speed five times greater than the final torque speed.

Pneutorque® Remote Control : 72mm Series

Remote control versions have no direction/shut-off control on the tool but rely on external pneumatic circuitry to provide this function.This opens up numerous application possibilities for the Pneutorque ranging from simple stall shut-off in a hazardous working environment to sophisticated, multi-spindle torque and angle shut-off systems.

Pneutorque® Remote Control : Standard Series
  • Stall control gives repeatability of ±5% on a given joint.
  • Torque transducers and angle encoders available for all models. These form the basis of sophisticated control systems giving repeatability of up to ±2%.
Reaction Nose Extensions

Special nose extension reaction devices are available for use in situations where the tool access is restricted. A typical application is the rear wheel nuts on heavy vehicles.