Electric actuator manufacturer AUMA has launched explosion-proof variable speed valve actuators for use in potentially hazardous environment. The new SAVEx actuators for open-close duty and SARVEx multi-turn actuators for modulating duty, combined with intelligent ACVEx actuator controls, provide full control of the motor speed at any time.
In oil and gas applications, variable speed offers significant advantages for challenging valve control tasks, since it allows the optimum operating speed to be selected for each change of valve position. High positioning accuracy and optimised setpoint control considerably increase the effectiveness of pressure control valves in gas pipelines, for example. On multiport valves, variable speed actuators aid rapid and accurate switch-over between ports.
Mechanical stresses on valve, actuator and pipeline are minimized by reducing the operating speed close to the end positions, allowing the moving element of the valve to make gentle contact with the seat. Pressure surges and cavitation effects in the pipeline can be avoided by using speed profiles.
When working in modulating duty, the actuator speed can be set to reduce progressively as the valve position approaches the setpoint, giving a significant increase in positioning accuracy.
Actuator speed can also be controlled by an external signal – either 4–20 mA analog or 0–100 % digital – to take full advantage of additional control variables or algorithms. A further option is speed synchronisation between two actuators.
AUMA’s new explosion-proof SAVEx and SARVEx actuators complement the weatherproof SAV and SARV type range. They are available in six sizes covering torques up to 1,000 Nm. Speed ranges include 6–60 rpm, 12–108 rpm and 24–116 rpm.
Why use pneumatic actuators?
Actuators come in many shapes. There is a wide portfolio of actuators in the market, each with different use for different applications. From electrical to pneumatic to hydraulic..The most common type available in the process industry would be the pneumatic type, since these are highly reliable, efficient and also safe. Pneumatic type uses pressurized air for the motion control to convert energy into rotary or linear motion. Pneumatic actuators are especially used to control the valves where fluids are moved in process industries.
There are two primary forms of pneumatic rotary actuators , single acting and double acting. They both work to push forward a piston.
Single-acting types have one port that allows air to flow into the cylinder. The pressure increases and pushes the piston forward or backward. Springs return the piston to its original position, making it ready for another pressure move.
Double acting type operate without a spring and have two ports. The first application of pressure pushes the piston forward. This is the same in both types. But the second pressure attack pushes the piston back into place. The customer however, should choose, which type he actually needs for the application: with the double type, when there is air loss no safety position required.
For the single acting (spring return) type there is the safety position when there is air loss.
Airpower actuators have the benefit to use the same body for both types. For the double and single acting type they have same body, which is a major advantage costwise since you need to keep stock just for one type. These can be converted into single-acting by merely inserting pre-stressed springs.
Along with the standard pivoting angle of 90° also available with 180° angle. And the pivoting angle is adjustable from 180° to 120°.
Another important aspect is the corrosion protection. In order to provide for corrosion protection a quality actuator should be hard anodized in body and caps. In addition, it should be powder coated. This is important for especially critical environments. For the single-acting type the springs should also be plastic coated in order to provide good corrosion protection.
(At airpower we cover a wide portfolio of pneumatic actuators. Pic: 3-position actuator)
(The double acting type APD-400 offering a torque vale up to 13022 Nm)
The APD-32 is the smallest in the airpower portfolio
(The stainless steel actuator from airpower AES 316. )
Dubai sewage treatment plant relies on AUMA actuators
200 AUMA electric valve actuators are now operating in Phase 2 of the Jebel Ali sewage treatment plant (STP) in Dubai. This increases the number of AUMA actuators on site to more than 400, including the 200 actuators at Jebel Ali STP phase 1 site that have been in operation since 2008. An additional 50 AUMA gearboxes have been installed for manual valve operation.
For Dubai Municipality, Jebel Ali STP Phase 2 is an important infrastructure project, helping to accommodate continued population growth as well as new developments including Expo 2020 Dubai. Phase 2 adds 375,000 m3/day of treatment capacity to the 350,000 m3/day already provided by Phase 1, while improving existing processes and treatment quality. The treated water is used for non-potable applications such as irrigation, helping Dubai Municipality reduce the need for desalinated seawater.
The AUMA actuators are installed across the entire new plant, located on a 670 hectare desert site. They automate a wide variety of gate valves, butterfly valves and penstocks at all stages of the treatment process. AUMA’s scope of supply includes 200 SA multi-turn actuators with AC actuator controls, some also combined with AUMA gearboxes. The most powerful gearboxes in the plant include six GS 400 part-turn gearboxes that control flow in a DN1800 pipeline, delivering a maximum torque of 125,000 Nm. All actuators are centrally controlled using the Profibus DP communication standard.
Some of the new actuators have been installed to automate valves in the phase 1 plant that were previously manually operated. Here, AUMA’s previous experience with similar retrofits proved to be particularly beneficial. AUMA’s local Dubai team provided comprehensive support to consultancy AECOM and contractor BESIX / Larsen & Toubro, from site survey, technical consulting and machining of tailor-made couplings to support for commissioning and training.
Rotork electric and pneumatic actuators chosen to deliver fresh water to German towns
Rotork electric and pneumatic actuators have been installed to help deliver fresh drinking water to neighbourhoods in Germany.
Stadtwerke Lohr am Main has been supplied with 39 GT pneumatic piston actuators and 13 CK modular electric actuators to be used at two municipal water works which supply the town of Lohr am Main, in Bavaria, and surrounding areas. The GT actuators have been installed at a plant in Schwebberg while the CK electric actuators are at a site in Wombach.
At both sites water is extracted from six springs and two deep wells while the treatment takes place at seven waterworks. The actuators, which have been installed on butterfly and gate valves ranging from 2 to 12 inches, are being used to drive isolation valves on the water stream in these plants to allow filtering, storage and distribution to take place.
Underground containers with capacity for 5,500 m³ store the treated water before it is distributed through a pipeline network which is around 180 km long.
The GT and CK actuators were chosen by the customer because of Rotork’s open communication and expert consultancy service. The functionality, reliability and durability of the actuators, as well as the modular nature of the CK, were also key factors.
Rotork’s GT range of single and double-acting pneumatic piston actuators offer torques from 2.4 to 15,300 Nm and air pressure of 2 to 10 bar. They can provide stroke adjustment of -5° to +5° from a 90° position while single or double end stop options are provided.
The actuator is suitable for use in hazardous areas with ATEX 2014/34/EU certification and is suitable for use at Safety Integrity Level 3 (SIL3) as a single device in accordance with IEC 61508.
The watertight CK range actuators are suitable for all valves in non-hazardous locations and can operate under the stress of high temperatures and strong vibrations by using separately mounted controls. It offers a direct output torque range of 10 to 500 Nm (7 to 369 lbf.ft), with a maximum torque when combined with a multi-turn gearbox up to 10,800 Nm (8,000 lbf.ft) and a maximum torque with a quarter-turn gearbox as high as 205,600 Nm (151,6000 lbf.ft).
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