Pneumatically operated systems are incorporated into many critical manufacturing processes, but if used inefficiently can impact significantly on overall operating costs. Katherine Crichton writes.
AS one of the highest consumers of electricity, there has been a lot of focus on refining compressor design in order to reduce energy costs and improve compressed air management.
However, compressed air systems are just part of the equation, with pneumatic devices playing a large part in driving efficiencies on the production line.
According to Bill Blyth, Manager, Industry Projects -Automation, SMC Pneumatics (Australia), companies involved in largely pneumatically-operated applications such as the food and beverage, and general automation sectors may be literally losing thousands of dollars in air leaks and inefficient processes and equipment.
He says a common mistake people make when examining compressed air efficiency is to focus on the compressor as the source of the problem.
“The compressor is merely a fan, it doesn’t generate the pressure. It’s the applications out in the plant that produce the pressure, so if we can undertake improvements in the factory, it has a corresponding effect on the amount of energy we are pulling out of the compressor,” Blyth said.
According to Blyth, a typical compressed air consumption pattern shows that around 15% of air use is made up of leaks, with actuators accounting for 35%, and air blow 50% of air usage.
This makes it all the more important then, Blyth says, to accurately gauge and address consumption at strategic locations throughout the factory.
“Unless the air demand is identified accurately, it is difficult to identify if excess consumption exists and establish plant benchmarks for ongoing monitoring,” Blyth explains.
Establishing benchmarks is essential for monitoring efficiency of pneumatic processes, and Blyth says there are several areas that need to be considered when benchmarking, notably air flowrate and pressure.
“Questions need to be asked such as what flowrate of air is required for the processes and what is the maximum pressure available? Is this pressure sufficient to satisfy all the processes?”
According to Blyth, a key area where manufacturers can identify process and energy efficiencies is through better management of air blow applications.
Air blow includes all operations where air is directed from a nozzle or open tube and can be the most costly and uncontrolled compressed air process.
“An increase in pressure of just 10kPa (2psi) will increase energy costs by 1%, and most of the excess pressures we see in factories are about 10 or 20 times that value,” he told Manufacturers’ Monthly.
“The use of the correct pressure cannot be overstated. The installation of pressure regulators at the point of application can greatly help in this regard. In most cases, air cylinders and actuators can operate at pressures around 4 – 5bar, without affecting performance.
The use of energy efficient blowguns and selecting the correct nozzles can also reduce air consumption by up to 75% without affecting performance,” he said.
However Blyth says wastage, excess consumption and the inefficiency of the compressed air processes, in a lot of cases, doesn’t filter through to the decision makers.
“In other words, the people who work with the air on the factory floor in general aren’t the one’s that sign the power bill.
“Managers need to focus more on energy efficiency when purchasing equipment, similarly to how people factor in fuel economy when purchasing a car,” he said.
As well as improving energy efficiency in compressed air applications, the use of hybrid or integrated pneumatic solutions are providing users with more production line flexibility at a lower cost.
Dale Marston, Festo Automation Consultant, says with the current global economic crisis, there is an increased focus on reducing cost while simultaneously boosting productivity.
“We are seeing an increased demand for pneumatic devices with integrated features such as better diagnostics and control. Products are becoming more modular and hybrid in their design so they not only offer pneumatic features, but electrical functions as well,” Marston said.
According to Marston, one of the key benefits of hybrid pneumatic devices is that they allow for improved process monitoring and measurement.
“Customers are adding more features to their devices, so valve terminals for example are now available with temperature measurement capabilities as well as an increased number of analogue inputs and process control measures,” Marston explained.
Marston gives a recent example of the company’s new position transmitter SMAT, which he believes will open up new areas of applications for pneumatic cylinders, particularly in automated applications.
A recent project the company took part in involved a supplier of die-cast products and assemblies to the automobile industry.
The company uses a conveyor to feed work pieces to a robot but the exact pick-up point varies due to the play in the conveyor chain drive.
“In order to improve the control system,” Marston explains “a servo drive could have been used for the conveyor system but it proved more cost effective to mount a position transmitting sensor on a pneumatic cylinder to carry out the universal offset measurement,” he said.
“The cylinder slides forward at the end and comes into contact with the indexing disc and the offset position of the work piece is then transmitted to the robot via the feedback signal from the SMAT.
“The effect of this is that the programming of the robot pick-up position is modified for every cycle, ensuring that it picks up at precisely the right position,” he said.