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Compress Energy Costs through Air Audit
With the rapidly escalating cost of electricity, there is an increasing focus within industry on the energy consumption of air compressor systems. As an un-maintained system can be wasting as much as 50% of a compressor’s output, it is important to ensure that your system is operating at its full potential.
A compressed air system audit can provide an important means of establishing the efficiency of systems and identifying precisely where energy losses are occurring. An audit will highlight the true costs of compressed air and identify simple opportunities to improve plant and process productivity, on-site safety, product quality, equipment reliability and plant downtime.
Things to target during an air audit to ensure compressed energy savings;
1. Plug those leaks and save
Studies indicate that as much as 50% of the compressed air produced in today’s industry is wasted to leaks. Identifying and correcting these leaks may save not only the purchase price of a compressor, but also reduce the amount of energy needed to run it.
It has been our experience that plants which have no disciplined compressed air leak-management program will have a cumulative leak level equal to 30-50% of the total air demand. This means that every 8-12 cfm leak can cost you $800-$1,200 per year.
NPS audits offer a leak inspection program so that every sector of the plant is inspected once a quarter to identify and repair leaks. Read more here.
2. Double-check air requirements
Often, production overestimates the amount of air it needs, resulting in an inefficient system.
More often than not, it is one process that needs a certain minimum pressure, affecting the pressure requirements of the entire system. For example, while the majority of a plant may only require 80 psi, the compressed air system may demand 98 psi.
In cases where only a small area of the system needs higher pressure, an effective solution is to set up a secondary, smaller, high-pressure unit or an appropriate booster, rather than driving the entire plant system at the higher pressure. Expecting the supply system to support a black hole is not a realistic design criterion.
3. Connections all teed off
One of the simplest fixes in a compressed air system is to replace tee connections with directional angle entry connections.
In a piping system where a feed line of compressed air is trying to feed into another airline, the turbulence caused by a 90 ° entry often causes a 3-5 psi pressure loss. Such a loss can cost you at every one of those tees.
More importantly, in a compressor house, the back pressure sends a false unload signal to the controls, causing premature unloading or extra compressors to be on-line. Using a 30-45° directional angle entry instead of a tee will eliminate this pressure loss, with the extra cost of the directional entry negligible.
4. Bad piping
Convoluted piping, piping restrictions, old pipes and incorrect pipe sizes often lead to pressure loss.
In a well-laid-out system, the interconnecting piping from the compressed air supply to the process and header distribution piping should create no pressure loss.
Piping is a major consideration, especially in older facilities or shops that have grown and expanded. Cast-iron piping will rust dramatically over time, releasing rust and scale into the compressed air system and creating build ups at various points in the system. In many cases, it is easy to simply replace a section of pipe to gain efficiency. When upgrading, ensure that the physical piping diameter is sized to deliver the required air flow with minimum pressure drop.
5. Down with over pressurisation
Excessive pressure increases leaks and wastes money.
Some end users will try to increase pressure in an attempt to compensate for capacity issues, however this in fact has the opposite effect on air flow, often exacerbating the problem. Additionally, there is a proportional relationship between pressure and power consumption, for which every 10 psi in excess pressure results in a 5% increase in power cost.
Too-high a pressure will amplify system problems, not solve them. Lower system pressures means less required mass, therefore fewer running compressors and lower overall running costs.
6. Insufficient storage
Insufficient storage is a common problem.
Across the board in manufacturing and processing, the value of an appropriately sized air receiver and appropriate compressed air piping is underestimated.
These tanks provide a first stage of moisture separation to help maintain compressed air quality. However, their primary function is storing and delivering compressed air to help meet periods of peak demand and to prevent excessive compressor cycling.
7. Inappropriate use
Unregulated and inappropriate use of compressed air wastes a lot of energy.
Considering that it costs eight times as much to use air as it does to use electricity, it is prudent to re-evaluate unregulated air-powered cabinet coolers, blow-offs, vacuum generators, mechanical pumps, air motors and hoists, vibrators, aeration, spraying and a host of other equipment.
Open blow, refrigeration and vortex cooling may all be replaceable with heat tube cabinet coolers with a potential savings of 3.5-4 kW each on a 30- by 24- by 12-inch average cabinet. In addition to this, venturi air amplifier nozzles or air inducers are recommended whenever possible, reducing blow-off compressed air by 50% or more.
8. Pumps and pule cleaners
Air-operated diaphragm pumps tolerate aggressive conditions relatively well and can run dry, which makes them a favourite with plant personnel.
But is an air-operated pump the best solution? Electric motor-driven diaphragm pumps are readily available, and may work just as well.
If air-operated pumps are needed, consider adding controls to shut the pumps off when they are not needed. Pumps waste the most air when they are pumping nothing. Additionally, check to see if the pump is running at the lowest possible pressure. Simple controls can increase pressure when needed.
9. Get rid of obsolete restrictions
Clogged filter elements, forgotten manual drain traps and neglected separator cartridges can cause significant drops in pressure and negatively impact capacity and reliability, not to mention creating air-quality issues.
One often overlooked item in the air piping system that causes pressure loss is equipment that is left installed but is no longer in use. Such things as old, unused orifice plate flowmeters, filters and separators are often left in the air system even though they are no longer required. Since they are not used or maintained, they fill with sludge, rust, and scale, causing ever-increasing blockage and pressure drop as the air flows past. This requires a corresponding increase in header pressure to maintain the required process pressure.
10. Maintain the system
Poor air quality adversely affects overall plant operations.
Air should be clean, oil free and dry, however to achieve this requires regular maintenance of the filters, separators and driers. Neglecting recommended maintenance can let oil get into the plant air and cause production problems such as dripping tools and fisheyes in paint systems.
Change air/oil separators, filters and other components at the optimum time and on a regular basis, not when they clog up and cause a pressure loss problem.
Air Audits by NPS
Nessco Pressure Systems offer a complete visual compressed air system audit, which may detect and identify problem areas. Our tailored audits have been proven to be extremely effective in increasing system production and providing significant cost savings. The cost of an audit may well be the best investment you have made, potentially saving you thousands of dollars a year in energy and production costs.
To ensure you are not spending more than you need to, our experienced service technicians can perform an efficiency audit on your system. Our audit involves a comprehensive report, with recommendations for a scope of work to improve your running costs. Call us on 1300 290 638 for more information!
