AWT - Relibility through simplicity
At the hub of process control, Rotork understand that the actuator is fundamental to process reliability. Our recognised design excellence in actuation has led to the AWT - a reliable, rugged yet simple design.
Actuator torque and thrust plus operating time must be defined and guaranteed for life. Position limit and torque settings must be fixed and repeatable. Valve torque sealing and protection has to be reliable if the valve is to do its job and isolate every closure.
Actuators located in extreme environments such as hot and cold ambient temperatures, high humidity, spray, flooding, chemical attack or vibration must be protected and go on performing year after year.
Electrical and instrumentation control gear must be designed to cope with regular and infrequent operation typical for vale duties, plus be suitable for upgrade should control or indication philosophies change.
Actuator maintenance tasks should be minimised and even eliminated, freeing site engineers to look after other site equipment.
Standardisation - engineering simplicity
In bringing together the valve, power and control system it is important that the actuator minimises plant design engineering, reducing time, installation costs and simplifying commissioning.
AWT features include:
- Standard mounting interface for valve connection
- Standard motor control schemes for electrical power
- Standard electrical control circuit irrespective of valve type
- Standard instrumentation interface
- Standard commissioning procedure for all valve types.
Protection - the key
Vast experience in the application of electric actuators has enabled Rotork to lead the world in actuator environmental protection. Situated in environments ranging from desert to tundra, marine and underground, where flooding, humidity and corrosive atmospheres are normal, actuators have to perform unfailingly. Rotork understand that the most important factor affecting the reliability of an actuator is protection from the environment - in simple terms, the integrity of its enclosure.
Ineffective cover or cable gland sealing allows breathing - a process where moisture is drawn into the enclosure forming condensation, the result of air exchanges caused by the expansion and contraction of air within the enclosure. Actuator failure will result - sooner rather than later.
AWT-watertight, non breathing, double sealed
Rotork Awr range actuators do not breathe. They are double sealed*, watertight and dust tight rated IP68 - IEC60529, NEMA 4, 4X & 6, suitable for submersion to a depth of 7 metres for 72 hours.
Reliability through double sealing
Double sealing is a means whereby the conduit entry and terminal compartment is completely sealed from the motor, control and switching compartments of the actuator. Should the cover be left off during installation or a defective cable gland or conduit allow water into the terminal compartment, the rest of the actuator remains fully protected. Without double sealing, investment in modern sophisticated controls can be rendered worthless as moisture and dirt ingress will cause actuator failure.
Some other manufacturers try to imitate double sealing by using sealed limit switches. With this design approach, while limit switches are protected, contactors, relays, heaters and travel measurement mechanisms are not resulting in actuator failure.
Integral motor control - AWT SyncroPAK
AWT SyncroPAK actuators incorporate the motor starter and local controls, with considerable economy to site wiring as shown below.
The SyncroPAK arrangement allows the essential elements of the valve control system to be factory tested and sealed prior to actuator despatch.
The valvemaker can carry out valve testing, requiring only a 3-phase power supply. Factory acceptance testing of the motorised valve can be simply carried out with no risk of incorrect motor control wiring causing valve or actuator damage.
Non-Integral motor control - AWT SyncroSET
Where a new installation requires motor control from the users Motor Control Centre (MCC), or existing installations already incorporating a MCC, the AWT SyncroSET provides the basic components for valve actuation.
Limit switches, indication contacts, optional local control station and motor supply wiring are brought out to the actuators terminal compartment ready for integrating into the MCC control system as shown below.
SyncroSET actuators are particularly suitable for installations where equipment at the valve location must be minimised, for example where high ambient temperature, vibration or space restrictions are present.
Valve control - reliability to the limits
At the heart of reliable valve control is the ability of the actuator to move on demand and, as important, to stop at the exact position needed for valve sealing. Position limit switches must be 100% reliable and repeatable. Position indication to the control centre must exactly reflect valve status. Torque protection for the valve must be easily selectable by both valvemaker and site maintenance personnel.
The AWT switch mechanism has being doing this job with complete reliability for 40 years. The unique design allows simple limit set-up by screw adjustment for turns, and selectors for independent torque overload setting and 'torque' or 'position limit' valve seating. The standard latch mechanism prevents both torque switch 'hammer' when seating and torque trip during unseating of sticky valves.
Valve control - a difficult problem made simple:
- Standard actuator control circuits irrespective of valve type.
- Standard set up procedure for all valve types.
- Built in torque, anti-hammer and sticky valve protection.
- Once set limits do not 'slip' or 'wander'.
- 2 normally closed & 2 normally open volt free contacts for end of travel valve status indication.