Actuator modularity – what does it really mean?

Water treatment works (WwTW) provide an essential public service, operations need to run smoothly 24 hours a day and technology needs to operate seamlessly.

As the intelligence behind most of the valves used at water treatment plants, electric actuators play an essential role in a wide range of applications including the operation of inlet and outlet control valves, control of filter bed applications and failsafe closure of certain valves critical to the plant operation.While electric actuators may look unassuming, the technology is sophisticated. Using an outside power source, actuators respond to a signal to automatically move to the desired position and motors drive a combination of gears to generate the desired torque level.

Electric actuators are frequently used on multi-turn valves such as gate or globe valves. With the addition of a quarter-turn gearbox, they can be used on ball, plug, or otherquarter-turn valves.The actuators’ performance needs to be maintained for the effective operation of the WwTW and off-site repairs or upgrades should be avoided – these are costly, time-consuming and damaging to the smooth flow of operations.In the first place, to achieve a true fit-and-forget actuator solution the actuator

With such a lengthy list of options, the actuator supplier needs to hone the recommendations for the initial solution to meet the precise needs of the customer, ensuring the system is tailored to complement and support the performance needs of the treatment works supplier needs to understand the role and requirements of the technology to ensure that the system supplied offers appropriate functionality.

Not only are there a wide range of actuator types but there is also an extensive list of features that can be provided such as fieldbus functionality, travel switches, torque switches, local position indicators, integral pushbuttons / controls, manual overrides and motor overload protection.

With such a lengthy list of options, the actuator supplier needs to hone the recommendations for the initial solution to meet the precise needs of the customer ensuring the system is tailored to complement and support the performance needs of the treatment works.

The supplier’s technical knowledge is essential in meeting the actuation needs of the treatment works. For example, is the valve based on simple open and close operation, is the valve required to control flow, should the valve operate under timer conditions and are intelligent digital based bus solutions required.

Fieldbus technology

But the WwTW is not a static environment. Water companies look to consistently improve performance. As a result, requirements can change and this is where true modularity is key to the success of the actuator’s design – this enables technology to evolve with minimum disruption to the workings of the site.

To achieve real modularity, complete adaptability of the system is required whereby actuator components dove-tail together to provide a ‘mix and match’ solution.

This ensures that the actuation products can be expanded, enhanced and refined on-site without removing the system for a factory upgrade. To provide total modularity, the concept of adaptability should extend beyond the actuator’s software functions.

Housing electrical connections separately from the actuator using ‘plug-and play’ technology is an important aid to the modular solution as wiring can be reached without disturbing the actuator’s internal components. And, from a safety perspective, should the actuator need to be removed, this can be done without contacting any cables.

One current trend for additional functionality that is sought from actuators, and a good illustration of the need for modular product design, is fieldbus technology.

Like any communication application, cables are unsightly and costly and the water

treatment industry is no different from other sectors in wanting to move away from traditional hard-wired solutions.

Fieldbus describes a new generation digital communication network that replaces

centralised control systems with a distributed network of devices.

The field devices linked by bus technology include controllers, transducers, actuators and sensors.

Set-up costs

These devices are equipped with computing power and have the ability to perform diagnostics, control and maintenance functions as well as providing bi-directional communication capabilities.

As a result it can report if there is a failure of the device or manual calibration is required – this increases the efficiency of the system and reduces the amount of maintenance required. Benefits of bus technology are centred on the advantages of digital data transmission which is considerably more accurate than traditional analogue methods.

Fieldbus also presents major cost saving advantages as the analogue approach demands that each device has its own set of wires and its own connection point, whereas fieldbus requires only a single twisted pair wiring connection.

The main appeal of digital bus technology is its ability to reduset-up costs and minimise maintenance challenges. Bus solutions including Profibus-DP, DP V1, DeviceNet, Foundation Fieldbus and Modbus are therefore becoming increasingly popular in the water treatment market.

As a result, several actuator users are looking to incorporate the new generation digital technology and this is where modular actuation systems have a distinct appeal – even existing actuators that have been supplied linked onto hard-wired control systems can be updated by simply changing the actuator’s integral control package.

The long term view should therefore be taken when entering into a relationship with an actuator supplier.

Technology evolves and a truly modular system will be key to the provision of products that will meet both the immediate and potential future needs of the treatment works.

Other key areas to be assessed to provide the foundations for a fit-and-forget solution will be establishing whether the actuator supplier has the backing of an established manufacturing operation with its own research and development facilities.

Additionally, can the company demonstrate that there is no design obsolescence, and will you be supported by technically-trained company representatives with engineering backgrounds that understand the need for adaptable actuator solutions and share the modular mind-set.

Ian Sully is managing director of Auma Actuators.

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