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Application Guidelines

Double Purchase Cable Cylinder Application Guidelines

1. Proof-loading and Pretensioning Cables
Once installed, but before putting into service, the cables on the cylinder should be proof-loaded and pretensioned to ensure that they are rigid for the maximum service life of the cylinder.

Proof-loading and pretensioning involve removing the two types of stretch in the cable by adjusting the clevis terminal lock nuts.

CC: Cable Tension Illustration
  • Proof-loading- When cables are manufactured, individual wires and strands are laid in position, but left slightly loose. When subjected to proof-loading the wires align themselves, tighten, and constructional stretch in the cable is eliminated.
  • Pretensioning- Elastic stretch in cable is inherent in the wire itself. It is removed when subjected to pretensioning.
There are two ways to proof-load and pretension a cylinder's cables- The Torque Method or The Field Method. All cables should be checked periodically from a preventative maintenance standpoint. When installing new cable assemblies, proof-load and pretension using these same methods.

PROOF-LOADING AND PRETENSIONING CABLES: THE TORQUE METHOD

  1. Tighten the clevis terminal lock nuts equally with a torque wrench to the values listed under Proof-loading torque in the Proof-loading, Pretensioning table below.

  2. Let tightened nuts sit for 30 seconds.

3.    Loosen the lock nuts to remove        
       tension (but tight enough to eliminate
       any slack.)

4.    Re-torque clevis terminal lock nuts        
       equally with a torque wrench to the
       total pretensioning figures listed in
       the table below.

Double Purchase Cable Torques

PROOF-LOADING AND PRETENSIONING CABLES: THE FIELD METHOD

  1. Block the load some distance from the end of stroke to keep the piston from bottoming.

  2. Apply a pressure that is 15% to 20% higher than the actual load pressure.

    NOTE: Load pressure is defined as the pressure required to move the load. When the load is stopped externally, before the piston bottoms, the relief valve or regulator setting becomes the load pressure.

3.   Upon pressurizing, one cable will become 
      tight while the other will become slack. 
      Manually adjust out the slack with a
      wrench on the clevis terminal lock nut.

4.   Release the pressure, block the load on
      the other side and repeat steps 1 thru 3.
      When these steps are done, turn down the
      regulator pressure to the normal operating
      pressure and remove the block.

CC: Field Method Illustration

2. Determining Special Cable Length
When an application requires a specialized cable length, use the dimensional table and illlustrations to determine the proper cable length.

CC: Pulley Dimensional
CC: Strip Dimensional
Double Purchase Special Cable Specs
NOTE: Pulleys and cables used on double purchase cable cylinders are always from the next smaller model size. Refer to the Double Acting cable cylinder models for cable specifications.

3. Lubrication Guidelines
All Tolomatic cable cylinders require internal lubrication unless specified. To ensure maximum cylinder life, the following guidelines should be followed:

  • Filtration: We recommend the use of dry, filtered air in our products. "Filtered air" means a level of 10 Micron or less. "Dry" means air should be free of appreciable amounts of moisture. Regular maintence of installed filters will generally keep excess moisture in check.

  • External Lubricators: External lubrication should be utilized for maximum service life of pneumatic cable cylinders. Lubrication must be maintained in a constant supply or the results will be a dry cylinder prone to premature wear. Oil lubricators, (mist or drop) should supply a minimum of 1 drop per 20 standard cubic feet per minute to the cylinder. As a rule of thumb, double that rate if water in the system is suspected. Demanding conditions may require more lubricant. If lubricators are used, we recommend a non-detergent, 20cP @ 140oF 10-weight lubricant. Optimum conditions for standard cylinder operation is +32o to +150oF (+0o to 65.5oC).

  • Sanitary environments: Oil mist lubricators must dispense "Food Grade" lubricants to the air supply. Use fluids with ORAL LD50 toxicity ratings of 35 or higher such as Multitherm® PG-1 or equivalent. Demanding conditions can require a review of the application.