Article How It Works: Pipeline Safety
Choosing the right valve for your application is the first step in achieving a safer pipeline operation.
Dynatorque D-Stop
Partial-stroke test device
Overview
The Dynatorque D-Stop™ partial-stroke test device is one of the world’s premier mechanical devices for partial-stroke testing of installed critical service valves.
Applications
This product is primarily used on emergency shutdown valves (ESDVs) while they are flowing process fluids and full-stroke valve testing is not practical. It can be supplied as a component of a new automated valve or retrofitted in the field to an existing valve or actuator package. The complete kit consists of a Dynatorque D-Stop device, engagement key, and drive coupler to adapt to the valve and actuator. Custom-machined drive couplers are available on request.
Benefits
- Simplicity: When it comes to testing systems, already sophisticated automated valve system packages can become cumbersome if controls are added. Unlike electric systems, it's not necessary to integrate the Dynatorque D-Stop device into the control loop or add ancillary controls.
- Cost effectiveness: The basic cost of this device, depending on the torque requirement, is less than that of an electric or controls-driven system. Instrumentation personnel and software programmers are not required for installation, further lowering costs. Moreover, the device has no controls, eliminating the need for commissioning and routine calibration of controls.
- True safety system tests: Because the Dynatorque D-Stop device requires no extraneous controls when the valve is tested, all the safety instrumented system (SIS) components, controls, and elements used in an ESDV or safety valve will be activated.
- Integrity for demanding industrial environments: The device is vibration resistant. Its exterior is coated for corrosion protection and independently certified to IP67 to prevent water ingress. Stainless steel trim is used for the keys, shaft, and sockets. The device is permanently lubricated and factory sealed, requiring no routine maintenance.
Features
The Dynatorque D-Stop device has been found safety integrity level (SIL) capable by an independent third party. A copy of our failure modes, effects, and diagnostic analysis (FMEDA) is available on request, including information such as the probability of failure on demand (PDFavg) that is necessary to calculate SIL values for your application.
A cathodic epoxy coating is provided as standard on all units up to and including Model 60. The result is a superior black finish that is highly protective of both internal and external surfaces.
Provision for mounting feedback devices onto the Dynatorque D-Stop device is a popular optional configuration. The following options are also available:
- custom or ISO bolt patterns on one or both flanges, custom bores, custom drive adapters for direct mounting to the 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 range of valve and actuator combinations.
Tech Specs
Double-acting actuators maximum air-start torque (not to exceed)
| Model | Unit Weight, lbm | lbf.in | lbf.ft | N.m |
| 3 | 12.5 | 3,000 | 250 | 339 |
| 7 | 20 | 6,700 | 558 | 757 |
| 12 | 38 | 10,700 | 892 | 1,209 |
| 21 | 54 | 17,300 | 1,442 | 1,955 |
| 36 | 110 | 42,000 | 3,500 | 4,745 |
| 60 | 208 | 120,000 | 10,000 | 13,558 |
| 260 | 681 | 174,000 | 14,500 | 19,658 |
| 500 | * | 333,000 | 27,750 | 37,623 |
| 1000 | * | 667,000 | 55,583 | 75,359 |
| 2000 | * | 1,333,000 | 111,083 | 150,604 |
Spring-return actuators maximum spring-start torque (not to exceed)
| Model | lbf.in | lbf.ft | N.m |
| 3 | 2,250 | 188 | 254 |
| 7 | 5,000 | 417 | 565 |
| 12 | 8,000 | 667 | 904 |
| 21 | 13,000 | 1,083 | 1,469 |
| 36 | 31,500 | 2,625 | 3,559 |
| 60 | 90,000 | 7500 | 10,170 |
| 260 | 130,000 | 10,833 | 14,690 |
| 500 | 250,000 | 20,833 | 28,250 |
| 1000 | 500,000 | 41,667 | 56,490 |
| 2000 | 1,000,000 | 83,333 | 113,000 |
| Model | Standard Output Bore, in |
Standard Keyway Size, in | Standard Mounting Pattern (Quantity and Size, Bottom Flange) | Standard Mounting Pattern (Bolt Circle Diameter), in | Standard Mounting Pattern (Quantity and Size, Top Flange) |
| 3 | 1.250 | .250 × 0.188 | (4)5/16-18 | 2.756 (ISO F07) | (4).344 |
| 7 | 1.750 | .500 × 0.375 | (4)3/8-16 | 4.016 (ISO F10) | (4).406 |
| 12 | 2.000 | 0.375 × 0.375 |
(4)1/2-13 | 4.921 (ISO F12) | (4).562 |
| 21 | 2.500 | 0.500 × 0.500 |
(4)5/8-11 | 5.512 (ISO F14) | (4).688 |
| 36 | 3.250 | 0.750 × 0.750 | (4)3/4-10 | 6.496 (ISO F16) | (4).781 |
| 60 | 4.000 | 1.000 × 1.000 | (8)5/8-11 | 10.000 (ISO F25) | (8).688 |
| 260 | 6.250 | 1.50 × 1.00 | (8)1-1/8-8 | 14.016 (ISO F35) | (8)1.188 |
| 500* | 7.000 | 1.50 × 1.00 | (8)1-1/2-6 | 15.984 (ISO F40) | (8)1.562 |
| 1000* | 9.000 | 1.75 × 1.50 | (12)1-1/2-6 | 19.016 (ISO F48) | (12)1.562 |
| 2000* | 10.000 | 1.75 × 1.50 | (12)1-1/2-6 | 19.016 (ISO F48) | (12)1.562 |
* Application modifications significantly affect product weight.
FAQs
What is partial-stroke testing?
A "partial-stroke test" might be defined as, for example, allowing the safety system to close the valve only 20°. When the Dynatorque D-Stop device is disengaged, it has no impact on the operation of the automated valve. But when it is engaged, the device restricts the travel of the valve actuator to the specified limits. In that case, all the valve control elements (e.g., solenoids, positioners, relays, limit switches) 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 partial-stroke test. Because the valve is only partially closed during the test, the flow coefficient is not significantly affected and process flow continues.
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