There is a common perception that not much is new in the world of pneumatics and hydraulics, but scrape the surface and a different picture emerges.
Dying technologies
Talk to most system integrators and control system engineers and they will authoritatively pronounce that pneumatic controls and devices belong in the ark. Their fellow mechanical and electrical engineers will explain that hydraulic actuators and motors are being superseded by their electrical counterparts.
But the statistics tell another story. Rob Carter, an analyst at IMS Research, blogged that the company’s latest studies show that the market for pneumatic actuators grew 8,2% from 2010 to 2011. Healthy growth trends have also recently been published by the UK’s BFPA, which noted that 16 countries reported double digit growth in hydraulic equipment sales from 2010 to 2011 and 20 countries reported positive growth in pneumatic equipment sales over the same period. And in an August 2012 analyst briefing Frost & Sullivan predicted a compound annual growth rate of 5,6% through 2018 in the European pneumatic equipment market.
Drivers of change
It would be oversimplifying the situation to write that the causative factors driving change in these industries could be reduced to regulatory and green initiatives.
Fundamental drivers of change include safety, standards and compliance; manufacturing efficiency; and operational efficiency.
The last decade and the start of this decade have seen the introduction of a plethora of safety standards and regulations with which manufacturers and end users of pneumatic and hydraulic equipment are mandated to comply.
To remain competitive in a global village experiencing a Great Recession, successful manufacturers have explored and adopted technologies with which to combat rapidly escalating input costs. Energy costs, rising raw material costs and labour costs have all been targeted. At the same time manufacturers have been forced to respond to regulatory and social pressures to reduce emissions.
Similar demands have been faced by operators who have also needed to reduce operational input costs and total cost of ownership. This has resulted in a need for low maintenance equipment with longer operating life and lower consumption of lubricants and fluids.
The consequences of responding to these drivers of change include component integration; simpler system integration; miniaturisation; new manufacturing methods; and innovative raw materials.
Component integration
Manufacturers in the fluid power arena have been making equipment smarter by integrating more components into functional units. In some cases this has been by incorporating more of the same technology and in some cases it has been achieved by creating hybrid devices combining pneumatic (or hydraulic) components with electronic components. One of the factors preventing a decline in the use of pneumatic equipment is the integration of electronics with air power.
Component integration can provide benefits such as cost savings and can add intelligence to offer local loop control autonomy, self-diagnostics and ease of integration into digital control systems. An example of the same technology integration can be found in Parker’s integrated economy circuit for hydraulic circuits. Where previously such an energy recovery circuit was accomplished through external valves, it is now achieved inside the standard valve housing.
Programmable position controllers which integrate electronics with pneumatics or hydraulics are examples of hybridised component integration. The Insight Air Cylinder from Motion Controls LLC is an excellent example of this, comprising a fully programmable pneumatic cylinder with integral keypad and QVLA LED light based position/volume sensing.
System integration
System integrators and machine builders can have their choice of almost any RS-232, RS-485 or Ethernet interface and protocol to interface their fluid control components to digital control systems for basic process control and for safety circuits. For example Festo’s MPA-L valve terminal can be equipped with network interfaces to most common industrial and Ethernet protocols via Festo’s CPX distributed I/O family. Even single hydraulic servo valves like Moog’s D670 series are available equipped with CANopen, Profibus or EtherCAT interfaces.
Miniaturisation
There is a prevailing trend towards miniaturisation. Smaller is better since smaller is lighter and generally costs less in terms of input costs (raw materials, handling, labour, conversion energy), but the degree of feasible miniaturisation varies. For motive applications using fluid power there is some limit to how far manufacturers can miniaturise before cooling and flow rate issues come into play. Despite this a whole new technology called mesofluidics is coming into play.
For off-highway vehicles the greatest motivator for miniaturisation has been the phased introduction of emission regulations, resulting in the need to improve fuel efficiency. This has driven hydraulic reservoir sizes and circuit capacities down to reduce vehicle size and weight. Manufacturers have responded with more component integration, smaller devices capable of handling higher flow rates, and increased system pressure. A good example is Sauer-Danfoss’s recently launched PVG 100 High-Flow valve option which offers a 30% increase in flow capacity in a claimed 'smallest on the market' package.
New manufacturing methods
This is one of the most exciting changes starting to impact the fluid power industry. 3D-printing or additive manufacturing (AM) is already used in a limited way in the production of components for this industry (see Motion Control, 1st quarter 2012). It involves the use of a carefully directed laser beam on a powdered plastic or metal material. As the laser strikes the powder, it melts and then solidifies. Multiple passes of the laser solidify one layer on top of the previous.
AM vastly reduces the amount of raw material and subsequent machining required for a part. It allows the manufacture of finished parts with complex internal voids, so manufacturing hydraulic control block is child’s play. Often no additional surface finishing stages are required and there are no restrictions to the number or internal voids or their shapes. This means that instead of traditional hydraulic pathways that are machined from a solid block of material and that are full of energy sucking right angle bends, hydraulic systems can be manufactured with smoothly radiused internal bends.
In a case study by leading British additive manufacturer 3D RTP, a twin-clutch gear change hydraulic actuator was redesigned to reduce mass and improve flow paths. The study showed that weight savings of over 30% were achievable with flow rate improvements of between 1,5 and 2,5 times.
Festo has made significant investment in AM production capacity and has successfully used this technology to manufacture the FinGrippers used in its Bionic Handling Assistant, achieving an 80% weight saving over conventional metal grippers.
Innovative raw materials
In response to green initiatives many new materials are being used in manufacturing and several harmful materials are being phased out. Manufacturers of hydraulic cylinders have been looking at alternatives to hard chroming of piston rods and piston ends. Parker has been comparing PTFE coatings, ceramic coatings and coatings of various nitrides in conjunction with new matching seal compounds.
Manufacturers of hydraulic fluids have introduced zinc-free products in response to concerns about toxicity. Recently Shell announced the introduction of its Tellus S3 M zinc-free hydraulic fluid. Graphene based materials, with their high strength and electrical conductivity have been reported to hold great promise for actuators working like human muscles and activated by the application of voltage, heat or light.
New nanomaterials have been developed for pneumatic and hydraulic oil filtration. Donaldson’s Ultra-Web filters for example are made of electro-spun fibres 0,2 to 0,3 microns in diameter and are capable of capturing particles down to as small as 0,3 to 1 micron.
Conclusion
The winds of change are surely creating exciting opportunities for growth and a sustainable future for pneumatic and hydraulic equipment and systems and all those who work with these.
To read the full version visit http://www.instrumentation.co.za/7570a
About the author
Andrew Ashton has electrical, mechanical and business qualifications and has been active in automation and process control since the early 1980s. Since 1991 he has headed up a company that has developed formulation management systems for the food, pharmaceutical and chemical manufacturing industries and manufacturing solutions involving the integration of various communication technologies and databases. Developed systems address issues around traceability, systems integration, manufacturing efficiency and effectiveness. Andrew is a contributing editor for S A Instrumentation and Control and Motion Control.
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