Journal for Control-Systems Engineering

Many manufacturers turn to an IoT approach as a cost-effective approach to modernising their infrastructure and increasing the speed of production. Sure, large fully automated plants have been in existence for a significant period of time, but it is only now that parts of this technology have started being used commonly amongst small to medium sized businesses. With the emergence of cheap, onsite prototyping from 3D printers, many SMEs are looking more closely at what other IoT based technologies can be incorporated into their workflow.

Aside from the design and manufacturing benefits, these technologies are also allowing plant managers and overseers to assess the operations of their facilities in real time, as a result, any problems that may occur are able to be picked up and resolved quicker with less waist and downtime.
Automated machinery and tools can operate for long periods of time and can adjust their speeds in response to delays in other points of the production line.

Full-scale automation can be very costly, as workspaces, or even buildings may need to be redesigned. The introduction of individual automatic machinery is much more reasonable of most companies.

Another solution that many are turning to are the upcoming robots-as-a-service providers, which work like common software-as-a-service agreements; it is essentially a model which encompasses the fields of artificial intelligence, cloud computing and shared services in one combined package and works similar to the renting of equipment from a third-party provider.

A recent study has revealed that the two fastest growing industries for RAAS are healthcare and manufacturing.

Laboratories are under huge pressure to find new ways to increase the efficiency and effectiveness of their processes this can include automation technologies, such as cloud connectivity, robotics and even electronic vision for quality control.

Products such as the “Thermo Scientific inSPIRE”, a vertical modular robotic platform is designed to integrate multiple instruments in a uniformed compact solution, provides intuitive control of all its integrated systems online from a standardised interface.

Automated water leak detection in domestic property has evolved over recent years, unlike with gas leaks, water can in many scenarios go un noticed for hours and cause significant damage. Water leak detectors usually work by placing a water detector wherever leaks may occur, more recently technology has been emerging that works by monitoring consumption, if there is a draw of water when the property is vacant the system can respond accordingly.

This response can be in the form of an audible alarm, a message sent to a mobile device or to cut the water and electricity supplies. This cut-off unusually by way of an automatic ball vale on the main water line.

Water leak detection systems can prevent damage totalling significant amounts of money, with some sources estimating over £6,000 in the first 12 seconds of an averagely sized water leak in the home.

Battery back-up systems or universal power supplies have been used as a safety system for many decades to provide an alternate power source to drive electric valve actuators to a pre-set failsafe position when external power fails. Nickel Cadmium batteries were generally replaced by Lithium Ion to improve battery performance and charge retention. However, all batteries require re-charging and have a limit to the number of times that the charge can be used before a re-charge. Failure of a battery trickle-charge system could result in a battery not recharging and therefore the safety failsafe system not be available when needed. A more extreme fault is that batteries can catch fire.

Until recently the size and weight of the battery back-up or UPS has not been a consideration and many manufacturers would attach an additional housing containing the failsafe system, adding considerable bulk and weight. And cost. A move towards more compact electric actuators, and a need to eliminate as many possible failure scenarios as possible cause a re-think and the use of capacitors was developed as an alternative to battery failsafe systems.

Capacitors are an electronic component that are quick to charge and then hold that charge until needed, and although single use per charge, can be charged and discharged millions of times. Modern high-performance capacitors are inexpensive and physically small, and battery back-up systems or UPS solutions typically can’t compete either on performance, size or cost.

Keen to test the newer capacitor failsafe electric actuator technology, J4CS recently tested the failsafe version of the AVA electric actuator from Actuated Valve Supplies and were surprised at all aspects of it.

1 The AVA Model 20 actuator is incredibly compact and sat comfortably in our hand, and as its failsafe system is by a capacitor, sees no housing size change when supplied as a failsafe actuator.

2 Fitted to a 2” PVC ball valve, J4CS opened the actuator using a 24VDC supply, then disconnected the 24VDC after 1 minute, causing the capacitor to discharge and close the actuator. After 1 minute the cycle repeated. The test was left to run on a continuous loop, thereby not restricting the number of operations.

3 J4CS stopped the continuous test without observing a single issue after 200,000 cycles, and with the ease in which the 200,000 cycles were achieved by the AVA actuator felt that the test could easily have continued to double the number observed.

4 J4CS were given an indication of cost which was compared with equivalent products online, whilst normally not commenting on commercial aspects, noted that the AVA capacitor is driven failsafe actuator was very competitively priced.

The conclusion arrived at was that where capacitors can be used to provide an alternative power source in failsafe systems in electric valve actuators, they offer significant benefits in terms of performance, functionality, size and apparently cost when compared to equivalent battery operated failsafe systems.

Footnote: Safeguards and restrictions introduced on flying batteries around the world following instances of batteries catching fire on aircraft do not affect or apply to capacitor based failsafe electric actuators.

Traditionally electric valve actuators could not be considered to replace pneumatic valve actuators where the fast opening and closing speeds that are standard in pneumatic actuators were required, resulting in the expense of installing an air compressor, air pipework, driers and filters to drive the air actuators. With far fewer moving parts air actuators can comfortably be used in applications where a high number of cycles are required, another ‘Achilles heel’ of electric valve actuators as the relevant European norm limits the performance of part-turn on-off electric actuators to just 10,000 cycles.

Some new smart electric valve actuators are now able to operate at speeds under 1 second making them contenders to replace costly compressed air systems and offering customers a real lifetime cost advantage. One application for fast-acting electric actuators is in filling systems, traditionally a stronghold of the pneumatic actuator.

J4CS recently tested an AVA S20 fast acting on-off smart actuator fitted to a 1” stainless steel ball valve from Actuated Valve Supplies in the UK and can report that the actuator operated the electric ball valve in 1 second effortlessly and faultlessly over a test of 30,000 cycles. It is clear from our test that the build quality of the AVA is high to withstand our test and we would not be surprised that the claim from the manufacturers’ UK agent that they have fast acting AVA modulating actuators in an application that have exceeded 6 million movements is true.

Modern manufacturing techniques have enabled the consistent production of highly accurate components which when assembled under quality-controlled conditions, produce products with a high build quality that result in accurate and reliable performance in service, and offer a long service life. Following our tests, our opinion is that the AVA electric actuator is an excellent example of the use of modern manufacturing techniques with an obvious and deep understanding of the benefits of strict attention to all aspects of quality control.

The design of smart electric valve actuators remained near stagnant for many years with most designs relying on the traditional cam and micro-switch solution to stop the motor. So-called design improvements often saw small changes to improve the design of the cams and switches, or the introduction of a brushless motor, for example, rather than a more radical change to the basic principals of operation.

Recent advances have seen a move towards digital control of the actuator’s position via digital magnetic positioning technology, which offers not only improved accuracy as it is digital but also a non-mechanical system which has obviously improved lifetime service implications compared to mechanical systems that are prone to ‘wear and tear’.

Whilst the elimination of mechanical components hints at improve total life cost as there as fewer parts that can fail, it is the switch to control of the functionality of the electrical actuator by software that is the more significant benefit. Employing brushless motors from the start, actuators like the AVA actuator available from Actuated Valve Supplies in the UK, recently tested by J4C-S have embraced modern technology and offer a dazzling list of standard and optional features, all controlled by software.

Combining a user interface comprising of a bright OLED screen and external push buttons, users not only have useful operational information displayed on the screen but have the ability to either control the electronic actuator locally, more commonly referred to a ‘local control’, but can make minor adjustments to several useful operational parameters that separates valve actuators like the AVA actuator from most rivals in its class, from a user perspective.

Features such as speed control, external adjustment of zero and span (open and closed positions) which in electric actuators with cams and switches requires the cover to be removed to access the switches, and external setting for 3 positions become standard features in software-driven actuators rather than ‘factory specials’ from manufacturers still using the original cam and switches design.

Smart electric actuators are devices that convert electrical energy into rotary torque which then can drive and automate various apparatus in industry.

With basic electrical actuators, the motor drives the equipment until the desired position is reached; this position is usually detected using a system of cams mounted to the actuator’s driveshaft, but can also be ascertained with magnetic digital position sensors linked with digital encoders, that when coupled with appropriate software or firmware stops the motor when a specific, usually pre-configured, angular position is reached.

The device’s motor usually drives the driveshaft via a planetary gearbox. This driveshaft then conects to the required apperatus, a valve for example, using a system defined in international standard ISO5211.

Control

The electrical and control connections vary substantially between applications and countries, ranging from traditional cable glands and cables connected to an internal terminal-strips, through to highly-sophisticated computerised data-bus connections over wired, or increasingly wireless, networks that has led to physical separation of control and manufacturing systems across the globe. This physical separation is especially useful for automated systems that span large geographical distances such as water or oil pipelines.

Modbus over TCP/IP, RS-232 or RS-485 is still one of the most widely used
Industrial Ethernet protocols currently in use today. The protocol fully complies with the standards defined in IEC 61158 and has become a de facto standard; this is despite it being originally propitiatory (Schneider Electric) and dating back to the late 1970s.

Types

There are generally four types of electric actuators, uni-directional, on-off, fail-safe and modulating.

• Uni-directional actuators always rotate in the same direction with the motor being stopped at certain angular intervals (usually 90°).
• On-off actuators drive the driveshaft from fully open to fully closed, or back as one movement.
• Fail-safe actuators have a secondary power supply, this is usually a battery or increasingly a capacitor. This supply drives the actuator to a preset safe position on the loss of primary power.
• Modulating actuators derive their drive-to angular position from either a digital or analogue input signal.