Industrial Utility Efficiency

Control Systems for Small and Medium-Sized Air Compressors


Energy Efficiency is also Possible for 25 hp Air Compressors

In today’s world, where “green” is “gold”, the efficient operation of multiple air compressors has taken on a new sense of urgency. In an era where giant manufacturing campuses with huge compressed air systems are fast disappearing, the emphasis shifts now to improving the efficiency of the higher numbers of installed small and medium size air compressors. With electrical rates on the rise and limited capital expenditure budgets, facilities are interested in improving the energy efficiency of their existing air compressors.  Retrofitting the control systems provides a viable alternative.

ADSE Facing LeftIt is a fact that the basic, air-cooled, reciprocating air compressor is still the most popular and affordable way to get compressed air to operate your small plant systems.  However, the available reciprocating compressor control systems are still start/stop or constant speed technology - both of which date back to the technology of one hundred years ago.

So the user operating two 25 hp reciprocating air compressors, for example, has the choice of either start/stop, constant speed or a confusing mixture of the two control options.  Too many start/stop cycles and the whole mechanical system is compromised with resulting starter and motor failures - or a complete shutdown of the system can occur as a result of overheating. Operating the machines in the constant-speed mode can end in uncontrolled and excess idling. This can compromise the plant filtration system with excess oil carryover and then of course the attendant increase in the cost of operation.

 

The Automatic Dual Control System

Installing a modern Automatic Dual Control on each compressor in the system allows each machine a selectable idle period before stopping. This brings all of the advantages of both the start/stop and constant speed systems in that it limits both the destructive cycling and constant idling and cools the motor/starter and compressor before stopping a machine that is no longer needed to meet plant capacity.

The Basic Universal Autodual Controller Model AD Converts a Recip or Rotary Air Compressor to High Efficiency OperationAutomatic or manual selection lead/lag control balances the wear on each compressor and  because of gradient pressure settings on each machine, never operates a compressor unless there is a need for more capacity. A totally unloaded timed soft-start is a major requirement for healthy system operation and motor and starter life echoes that.  An emergency shutdown system that operates simply and effectively on existing low oil level, low oil pressure or high air temperature signals has the ability to send a remote signal to indicate a shutdown. Pressure-control is maintained by pressure-transducers combined with a display panel making pressure selection accurate (+/-1/2%) and easy. The system does not use mechanical pressure switches.  Since we all know that an air compressor operates at its most efficient point when it is OFF, then that is the goal that this controller does meet.

 

Universal Aftermarket Application

The Universal Autodual is currently in use on air-cooled (all makes and all types) and water-cooled double-acting air compressors ( ESV, ESH, HB, WG-9, WN-112, YC) world wide.

Even small compressor systems can yield substantial savings. A recent aftermarket installation of a dual system comprised of two Champion 7.5 hp start/stop compressors in a large tire retailer in Westchester County, New York.  The local utility, ConEdison, had  a power monitoring system in place. After nine months of operation with the AutoDual ADSE controller (Automatic Dual control, auto lead/lag alternation), the power savings was annualizing at about \$1700.00 for the system.

The Universal Autodual controllers are equally at home with rotary screw air compressors. There are installations on air compressors up to 250 hp in size.

In a sawmill in Maine, two basic Universal Autodual controllers with automatic (cycles on the clock) lead/lag control were installed on two 250 hp Quincy Northwest rotary screw air compressors with constant-run, modulating controls.  The conversion to automatic dual control resulted in the lag compressor automatically stopping 19 hours per day on average. The installed cost of the Universal Autodual Controllers (about \$5000) was written off in about three weeks and the saw mill continues to accrue the power savings while reducing compressor turning hours by about 6000 hours annually.

A recent conversion was made to five LeRoi 100 hp constant-run, modulating-control, rotary screw air compressors in Texas.  They installed the Automatic Dual control and lead/lag operation resulted in stopping one compressor in the first shift and two in the second and third shifts (on average) resulting in substantial operating savings and reduced turning times.
The Universal Autodual converts older and inefficient modulating constant run rotaries of all sizes, including tank mounts, bringing new life and efficient operation to otherwise toxic installations.

 

Make the “Hodgepodge” Efficient!

The Universal Autodual will automatically link compressors of different makes and types - so typical of the hodgepodge existing in many operating facilities.  For example, it is not unusual to connect a rotary to a recip in automatic lead/lag configuration to operate the smaller machine in the lead position in the second and third shift. The larger air compressor is placed in the lag position and is always ready to automatically pick up any usual capacity requirement if required. First shift operation converts automatically to the larger rotary with the smaller recip in the ready-lag position.

 

Conclusion

In an economy that is requiring tighter control of operating machinery, users can use high-efficiency compressor controllers to revitalize an existing system and operate at high efficiency and automatically in virtually any load environment.  Remember, air compressors operate at their most efficient point when they are off.

 

 

For more information, please contact Bob Foege, Standard Pneumatic Products, Inc., www.stdpneumatics.com.