Q-Series Rack & Gear Valve Actuators

QS and QD Series

  • Ductile Iron & 316 Stainless Steel constructions
  • Rack & GearTM mechanism
  • CF8M shaft and rack in all sizes and versions
  • Torques to 14,000”#
  • Single & double acting
  • 90 degree rotation + 5 each end
  • Pressures to 150 psig
  • Temperatures from –60F to +400F
  • Cycle times as fast as 0.1 seconds

Designed to Outperform

  • Fewer seals yield fewer failures
  • Reduced friction for extreme longevity
  • Offset cylinders reduce internal stresses
  • Captured springs for safety
  • Action reversal by turning top side down
  • Outstanding throttling capabilities with optional throttling certification available
  • Exceptional corrosion resistance with stainless steel construction
  • Handles vibrating pipes with ease

Lower Installed Cost

  • Non-proprietary commodity seals
  • Piston seals replaceable while actuator remains installed
  • Contaminant damaged seals quickly replaceable in line using inexpensive commodity seals
  • Reversible SR cylinders serve as spares if damaged
  • Seal replacement does not require accessory recalibration
  • SR version uses less air volume than most competitors saving $ and eliiminating valve jump

Numerous Options

  • Partial stroke
  • Top mounted lock outs
  • Dribble control
  • Anti-water hammer
  • High speed / low speed
  • Manual override
  • Solpaq direct NAMUR solenoid mounting
  • Universal mounting capability
  • “Close mount” on extended stem valves

Design Overview

The distinctive look of the QTRCO Q-Series actuator comes from the uniquely designed Offset Cylinders.


The QTRCO Rack & Gear® design offsets the cylinders to where the piston axis is aligned to the pitch circle diameter of the pinion gear. This means that the piston forces cause no side loading of the piston into the cylinder wall. The lack of side loading means less friction and thereby less wear. Additionally, throttling (modulating) quality is improved as there is less sticking and stick/slide action of the piston.
Standard Rack & Pinion actuators have rack gear teeth that are off center of the piston axis such that when spring or air force is applied to the piston, there is a cantilever induced side force that pushes the piston into the cylinder wall.
To account for the side loading, R&P designers include wear pad material on the piston skirt to lessen the wear between the piston and the cylinder. Initially the wear pads do not fully conform perfectly to the cylinder bore but they ‘wear in’ after some number of cycles. The greatest problem with wear pads is that they slide against the cylinder bore and they “stick” when stationary and cause stick/slide motion when used for throttling applications.


THE PATENTED RACK & GEAR® MECHANISM WITH LOW FRICTION ROLLERS AND TWIN SIDE RAILS compliment the cantilever force eliminating offset cylinders to result in an extremely low friction actuator that, in the DA version, can be operated using only one’s breath pressure (see video).

Reduced friction, while extending cycle life, also provides for excellent throttling control.


All QTRCO Rack & Gear® actuators have Balanced Shafts.  This symmetric shape gives several advantages.  By having the same drive geometry on both sides, it is capable of driving two valves at the same time or it can be turned upside down to reverse the action.  But the primary reason behind the design is to eliminate the Piston Effect often found in rack and pinion actuators.  Thus, there are no side forces applied to the shaft when under pressure, which can cause premature wear and ultimate failure.


The full diameter, nested and inward located springs are captured with redundant retention and are designed with stress levels suited to infinite cycle life.  In the unlikely event of spring breakage, the entire spring assembly is replaced with users never experiencing expanded springs.


DESIGNED TO PREVENT FAILURES,all QTRCO actuators are still subject to entrained contaminants which may at times cause piston seal damage.  In this event, piston seals are replaceable at very low cost, while the actuator remains installed on the valve. Leaving the valve in the line and the actuator installed saves the labor otherwise required to remove the actuator and to convey it to the maintenance shop – or to send it outside for repair. On SR versions, the captured springs allow safe end cap and cylinder removal and full access to the piston seal which is always a low cost, locally available commodity o-ring. Should the cylinder be damaged, turning it end for end provides a clean undamaged bore for continued operation without need to purchase a new cylinder. Because the springs remain in place, they continue to hold the actuator in the spring fail position, making it possible that the process may not require shutting down. Even if the process is shut down, the ability to quickly obtain and to replace the piston seals means it will not be shut down for long. An added plus is that these repairs do not affect instrument settings so no re-calibration is required to place the unit back in operation.



Field ReversibleQ Series Rack & GearTM actuators are provided with standard ISO 5211 mounting patterns on both top and bottom sides of the actuators in order to facilitate the ability to change actions by turning the actuators top side down.


The shaft drives are double square female and are over sized to allow use of adapters for mounting flexibility.

Should the normal ISO bolt pattern not be ideal for an application, there are extra mounting holes that can be used to bolt on a Universal Mounting Plate (UMP) that can be provided with application specific bolt patterns. Usually, we can mount directly to any valve that does not have a protruding packing gland.


The side not against the valve is provided with a removable ‘Top Hat’ that provides the common NAMUR accessory mounting and drive slot.  Being removable, this is relocated to the opposite face when action reversal is desired.


Using the inherent mounting flexibility we are readily able to provide ‘Replipaqs’ that convert our normal mounting geometries to precisely match those of competitive actuators.  This allows users to replace existing actuators with QTRCO’s with the need for new brackets and couplers.


Our ‘Close Mount’ concept allows Q series actuators to achieve a very compact assembly when driving extended stem valves and the valve shaft is ‘swallowed’ by the through hole actuator shaft and then driven from the top side of the actuator.  Typical V type ball valves are excellent candidates as they use the actuator’s throttling capability and compact package size to provide users with a smaller yet high performance product.


Bracket and coupler designs are closely controlled to provide optimum user mounting.  An example is out two piece Omega bracket kit that easily and separately  mounts to the actuator and the valve and is then brought together to form the final assembly. Fat fingers are not squeezed trying to access hidden fasteners.