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Our DYNATORQUE D-Stop partial-stroke test device is for use in automated quarter-turn valve applications in which compliance with standards such as ISA-S84.01 (Application of Safety Instrumented Systems for the Process Industries) and IEC 61508/61511 (Functional Safety of E/E/PE Safety-Related Systems) is of concern.

The test device enables testing of the safety instrumented system (SIS) in applications where exercising the final trip element (the valve) may not be practical, such as when the valve is installed in an active process flow line (reference ISA-S84.01, paragraph One of the terms associated with these industry standards is "valve partial-stroke testing."


Double-acting actuators maximum air start torque

Model  Unit Weight, lbm in.lbf ft.lbf N.m
D3DS 12.5 3,000
250 339
20 6,700 558 757
38 10,700 892 1,209
54 17,300 1,442 1,955
110 42,000 3,500 4,745
208 120,000 10,000 13,558
681 174,000 14,500 19,658
333,000 27,750 37,623
667,000 55,583 75,359
1,333,000 111,083 150,604

Spring-return actuators maximum spring start torque

Model  in.lbf ft.lbf N.m
D3DS 2,250
188 254
D7DS 5,000 417 565
D12DS 8,000 667 904
D21DS 13,000 1,083 1,469
D36DS 31,500 2,625 3,559
D60DS 90,000 7,500 10,170
D260DS 130,000 10,833 14,690
D500DS 250,000 20,833 28,250
D1000DS 500,000 41,667 56,490
D2000DS 1,000,000 83,333 113,000


Model Standard Output Bore, in Standard Keyway Size, in Standard Mounting Pattern
Quantity and Size (Bottom Flange), in
Standard Mounting Pattern
Bolt Circle Diameter, in
Standard Mounting Pattern
Quantity and Size (Top Flange), in
D3DS 1.250 0.250 × 0.188 Four 0.3125–18 2.756 (ISO F07) Four 0.344
D7DS 1.750 0.500 × 0.375 Four 0.375–16 4.016 (ISO F10) Four 0.406
D12DS 2.000 0.375 × 0.375 Four 0.50–13 4.921 (ISO F12) Four 0.562
D21DS 2.500 0.50 × 0.50 Four 0.625–11 5.512 (ISO F14) Four 0.688
D36DS 3.250 0.75 × 0.75 Four 0.75–10 6.496 (ISO F16) Four 0.781
D60DS 4.000 1 × 1 Eight 0.625–11 10.000 (ISO F25) Eight 0.688
D260DS 6.250 1.50 × 1 Eight 1.125–8 14.016 (ISO F35) Eight 1.188
D500DS† 7.000 1.50 × 1 Eight 1.50–6 15.984 (ISOF40) Eight 1.562
D1000DS† 9.000 1.75 × 1.50 Twelve 1.50–6 19.016 (ISO F48) Twelve 1.562
D2000DS† 10.000 1.75 × 1.50 Twelve 1.50–6 19.016 (ISO F48) Twelve 1.562

Application modifications significantly affect product weight.

What is partial-stroke testing?

A partial-stroke test can be defined as, for example, enabling the safety system to close the valve only 20°. However, when the DYNATORQUE D-Stop device is disengaged, it has no impact on the operation of the automated valve. When the device is engaged, it limits the travel of the valve actuator to the specified travel limits. In that case, all of the valve control elements (solenoids, positioners, relays, limit switches, etc.) are tested. If the automated valve is inoperable because of valve blockage, mechanical failure, misalignment, or some other control system anomaly, it will become apparent during a DYNATORQUE D-Stop device test. Because the valve is only partially closed during this test, the flow coefficient is not significantly affected, and process flow continues.

Principles of operation

The device has two internal cams. During normal valve operation, the DYNATORQUE D-Stop device is disengaged, and the actuator is free to stroke the valve on demand.

When the partial-stroke test is to be performed, the stainless steel engagement key is inserted into the key socket. When the redundant safety device is pulled, the engagement cam is free to rotate 90° counterclockwise. This safety feature forces an intentional, “two-handed operation” to engage the device.

When the key is turned 90° counterclockwise, it is locked into the device and the engagement cam rotates—the device is now “engaged.” At this point, when the valve actuator is sent a test signal to go to the ESD or safety-test position, the drive cam that is attached to the actuator through the drive coupling rotates until it comes into contact with the engagement cam, normally 20° (this is a specifiable value).

The unique key cannot be removed from the DYNATORQUE D-Stop device while the unit is engaged. Therefore, if the key is kept in a control room or lock box, the plant operators are assured that the device has not been accidentally left in the engaged mode. All keys and devices are serialized. If a key is ever lost, new ones can be easily obtained from the factory. DYNATORQUE D-Stop devices may be keyed such that one key fits several devices in a plant, or each device can be supplied with its own unique key.

Actuator-to-valve direct interface mounting

The device can be provided as a component of a “new” automated valve, or it can be field retrofitted to an existing valve or actuator package. The complete kit consists of a DYNATORQUE D-Stop test device, engagement key, and drive coupler for customer adaptation to the valve and actuator. Custom-machined drive couplers are available from Cameron on application.

Housing flanges can be factory drilled to accommodate a wide variety of valve and actuator combinations, including custom and ISO bolt patterns on either or both flanges, custom bores, custom factory drive adapters for direct mounting to actuator and valve, increased or decreased travel limits, automation mounting packages, limit switches, and option for remote operation.

The device is totally enclosed, weatherproof, and permanently lubricated. No routine maintenance is required. The standard device has been independently certified to IP-67 for protection against water ingress. It is available for applications up to 4,000,000-in.lbf actuator torque.

Metal-to-metal safety

The DYNATORQUE D-Stop device physically prevents the valve from moving past the specified test point. Once the device is engaged, the valve cannot move past the set point.


DYNATORQUE D-Stop devices with torque ratings up to 180,000 in.lbf have cast or ductile iron housings and covers. Units in excess of 180,000 in.lbf are fabricated of carbon steel. Engagement cams are stainless steel; drive cams are cast ductile iron; input shafts are stainless steel; shaft and segment seals are Viton rubber; bushings are oil-impregnated copper nickel steel alloy; cover-to-housing sealant is silicon RTV 732 to assure against water ingress. Engagement keys and key sockets are stainless steel.

As a standard superior coating, Cameron offers a cathodic epoxy coating on all units up to and including D60Ds. The result is a superior black finish that is highly protective of both internal and external surfaces.

Other options

  • ISO bolt patterns on either or both flanges
  • Custom bores
  • Custom factory drive adapters for direct mounting to actuator and valve
  • Increased or decreased travel limits
  • Automation mounting package
  • Limit switches
  • Remote operation
  • Lock-in tag-out configuration
  • Factory-drilled bodies to accommodate a wide variety of valve and actuator combinations
  • Provision of mounting feedback devices