Point Of Use Compressed Air Storage

February 9, 2016Ken Bean

There are frequent articles on the site touting the benefits of compressed air storage. We usually refer to large receiver tanks as the ones pictured above. This article will focus on the benefits of local storage or receivers located at or near the point of use where there are one of just a few intermittent high flow demands. I have found this technique to be extremely beneficial in bag house pulsing applications.

A correctly-sized storage receiver close to the point of the intermittent demand with a check valve and a metering valve can be an effective and lower cost alternative. For this type of storage strategy, a check valve and a tapered plug or needle valve are installed upstream of the receiver. The check valve will maintain receiver pressure at the maximum system pressure and only allow air to be consumed from the receiver when the system line pressure falls below the pressure of the receiver. The plug or needle valve will meter the flow of compressed air to “slow fill” the receiver during the interval between demand events. This will have the effect of reducing the large intermittent requirement into a much smaller average demand.

Understand Your System

February 2, 2016Ken Bean

Compressed air system’s are complex. Each components carries it’s own difficulties in understanding but once multiples of these components are installed in an industrial plant, a simple area drawing gets complicated really quick.

Before implementing energy reduction strategies, be familiar with all aspects of your compressed air system.

System Supply

Analyze the supply side of your compressed air system for the types of compressors and dryers used, suitability and settings of capacity controls and other operating conditions. Understand the basic capabilities of the system and its various modes of operation. Verify that air compressors are not too big for end uses. For example, an air compressor is oversized if the end use only requires air pressure that is 50 % of the pressure that the compressor is capable of producing. Once the big picture is in view, supply side operating conditions can be modified, within the constraints of the compressed air unit, to better match the demand side uses of compressed air.

System demand

Identify all the uses of compressed air in the plant. Quantify the volume of air used in each application and generate a demand profile, quantity of air used as a function of time, for the compressor. Equipment specifications for operations that use air are good resources for obtaining data on air volume use rates. The profile highlights peak and low demand. A general assessment of compressed air use will help identify inappropriate uses of air.

System diagram

Develop a sketch of your compressed air system including compressors, dryers, receivers, filtration, drain traps, air supply lines with dimensions, and compressed air end uses to provide an overall view of the entire compressed air process.

Distribution system

Investigate the distribution system for any problems related to line size, pressure loss, air storage capacity, air leaks and condensation drains. Verify that all condensation drains are operating properly because inadequate drainage can increase pressure drop across the distribution system.

Maintenance

Evaluate maintenance procedures, records and training. Ensure that procedures are in place for operating and maintaining the compressed air system, and that employees are trained in these procedures.

Qualified audit engineers can give you a complete understanding of your system.

Keep Your Money

January 26, 2016January 26, 2016Ken Bean

Conservation Strategies for Compressed Air Systems

Identify easy to implement energy conservation opportunities in your compressed air system by conducting a walk-through assessment. Simple conservation opportunities can result in savings up to 25% of the current cost to run the compressed air system.

Leaks

Routinely check your system for leaks. A distribution system under 100 pounds-per-square-inch gauged (psig) of pressure, running 40 hours per week, with the equivalent of a quarter-inch diameter leak will lose compressed air at a rate of over 100 cfm costing over $2,800 per year. In noisy environments an ultrasonic detector may be needed to locate leaks.

Compressor pressure

The compressor must produce air at a pressure high enough to overcome pressure losses in the supply system and still meet the minimum operating pressure of the end use equipment. Pressure loss in a properly designed system will be less than 10% of the compressor’s discharge pressure found on a gage on the outlet of the compressor. If pressure loss is greater than 10%, evaluate your distribution system and identify areas causing excessive pressure drops. Every two PSI decrease in compressor pressure will reduce your operating costs 1.5%.

Identify artificial demands

Artificial demand is created when an end use is supplied air pressure higher than required for the application. If an application requires 50 psi but is supplied 90 psi, excess compressed air is used. Use pressure regulators at the end use to minimize artificial demand.

Inappropriate use of compressed air

Look for inappropriate uses of compressed air at your facility. Instead of using compressed air, use air conditioning or fans to cool electrical cabinets; use blowers to agitate, aspirate, cool, mix, and inflate packaging; and use low-pressure air for blow guns and air lances. Disconnect the compressed air source from unused equipment.

Heat recovery

As much as 80 to 90% of the electrical energy used by an air compressor is converted to heat. A properly designed heat recovery unit can recover 50 to 90% of this heat for heating air or water. Approximately 50,000 British thermal units (BTUs) per hour is available per 100 cfm of compressor capacity when running at full load. For example, consider a 100 hp compressor that generates 350 cfm at full load for 75% of the year. If 50% of heat loss is recovered to heat process water, the savings, at $0.50 per therm, would be about $4,100 per year in natural gas.

Inlet air filters

Maintain inlet air filters to prevent dirt from causing pressure drops by restricting the flow of air to the compressor. Retrofit the compressor with large-area air intake filters to help reduce pressure drop.

Compressor size

If your compressor is oversized add a smaller compressor and sequence-controls to make its operation more efficient when partially loaded. Sequence-controls can regulate a number of compressors to match compressed air needs, as they vary throughout the day.

Air receiver/surge tank

If your compressed air system does not have an air receiver tank, add one to buffer short-term demand changes and reduce on/off cycling of the compressor. The tank is sized to the power of the compressor. For example, a 50 hp air compressor needs approximately a 50-gallon air receiver tank.

Cooler intake air

When ingesting cooler air, which is more dense, compressors use less energy to produce the required pressure. For example, if 90 degree F intake air is tempered with cooler air from another source to 70 degree F, the 20 degree F temperature drop will lower operating costs by almost 3.8%.

V-belts

Routinely check the compressor’s v-belts for proper tightness. Loose belts slip more frequently which reduces compressor efficiency.

An air audit performed by a professional auditing company can find tremendous savings in your compressed air system. Consider an audit as an investment for your companies future.

Compressed Air For Free

January 19, 2016Ken Bean

If you are a regular reader, you frequently see post’s discussing the extreme cost of compressed air. We spend a lot of time posting of various ways to reduce the cost of producing compressed air for your applications and how to optimize your compressors to reduce the cost of electricity.

Following up on last weeks article discussing gas turbine drivers, This week I wanted to discuss the benefits of utilizing a steam turbine driver for your centrifugal compressor.

Wouldn’t it be great if you could run your air compressors for FREE! Of course it would but how could that be possible? Certain large industrial clients use a tremendous amount of steam for plant applications. The steam is often produced at a higher than use pressure and therefore the plant will incorporate steam pressure reduction valves (PRV’s) in the plant where the steam pressure is reduced from it’s output pressure from the boiler or steam generator to the required use pressure in the plant.

Rather than incorporate a PRV, a better use would be to incorporate a steam turbine which can drive the air compressor and put the reduced pressure steam back into a lower pressure steam system. I have a particular client that takes in 575 pounds of steam pressure to their steam turbine which is driving their centrifugal compressor and then downstream of the turbine, the steam is directed to their low pressure plant steam system at 110 pounds of pressure.

I’m sure when most people think of a steam turbine, the initial thought is a huge piece of equipment that perhaps drives a generator at a power plant. However, from the picture above you can see that small turbines can be incorporated into plant use for a variety of applications. Another great feature of using steam turbines is you incorporate a large amount of horsepower from a very small footprint. A 2000 horsepower steam turbine has a much small footprint than a 2000 horsepower electric motor.

If you have excess steam in your facility and feel that driving your air compressor with steam is a viable alternative, feel free to contact me to discuss your particular requirements.

Natural Gas Cost Vs Electricity

January 12, 2016January 12, 2016Ken Bean

I recently received a phone call from a client asking for some preliminary pricing on a centrifugal compressor that was driven with a natural gas engine. I’ll have to admit, in my years in the compressed air field I had never had this request but I’m always willing to seek out new idea’s.

Contacting my regional engineer for some guidance, I found this is more common than I knew and the factory could accommodate the request for budget pricing.

My clients goal with this project is to meet a corporate mandate that electrical consumption be reduced by 25% over the next several years. His thought was the cost of natural gas could potentially be lower than their cost for electricity or at least near the same. By utilizing natural gas the reduction in electrical consumption could be met. I know over the past few years that many of my power generation clients are moving to mothball coal fired gas plants and they are being replace by natural gas fired plants. Although their direction is being pushed much harder by EPA emission mandates than by fuel cost.

Further researching this type of driver, I found it is much more common in the oil & gas industry than in other area’s of manufacturing. While researching the idea I also found an article written by our friends over at Bechtel Engineering and thought there might be some interest from our readers to look into this further as well.

You can read the overview and download the whitepaper at the following link: http://bit.ly/1RwSjy4

I’ll keep you posted on my clients project and let you know how this progresses and also the determination of how this change would actually pay off in the end from both a reduction of carbon footprint along with overall fuel cost.

The Power Company Loves You

January 5, 2016Ken Bean

With a powerhouse full of compressors, your power company wakes up looking like the little boy pictured below; just thinking of the money it will make from you today.

How much does it cost to run those air compressors?

Compressed air is one of the most expensive uses of energy in a manufacturing plant. About eight horsepower of electricity is used to generate one horsepower of compressed air. Calculating the cost of compressed air can help you justify improvements for energy efficiency.

Cost per year To find the annual cost of electricity used to power a compressed air system, calculate the cost for running the system under loaded and unloaded conditions. For each, multiply:

horsepower (hp)

conversion factor 0.746 kW/hp

total operating hours per year (hr/yr)

cost per kilowatt-hour ($/kWh)

% time fully-loaded or unloaded

% full-load hp, loaded or unloaded

Divide the product by the motor’s efficiency.

Use the formula below for your calculations.

Find A Leak To Fix A Leak

December 28, 2015December 28, 2015Ken Bean

Leak Detection

A small leak in your compressed air system may not seem like a big deal. Until you consider that small leak at 1/32” diameter will pass 1.62 SCFM on an air system running at 100 PSIG. That equates to 2,332 SCFM in a 24 hour period. This shows with just a few small leaks, they can quickly add up to the equivalent of several horsepower of compressed air being required just to satisfy the leaks.

The best way to detect leaks is to use an ultrasonic acoustic detector, which can recognize high frequency hissing sounds associated with air leaks. These portable units are very easy to use. Costs and sensitivities vary, so test before you buy. A simpler method is to apply soapy water with a paintbrush to suspect areas. Although reliable, this method can be time consuming, messy and on some applications, near impossible to reach.

Utilizing Compressed Air Storage

December 15, 2015December 21, 2015Ken Bean

If you look at most any industrial compressed air system you will find a receiver located somewhere in the layout. However, just having a receiver does not mean the system is fully utilizing the capability of the storage.

Properly utilized compressed air storage should allow a compressed air system to meet its peak demand needs and help control system pressure without starting additional compressors. The correct type and quantity of air storage depends on air demand patterns, air quantity and quality required, and the compressor and type of controls being used. An optimal air storage strategy will enable a compressed air system to provide enough air to satisfy temporary air demand events while minimizing compressor use and pressure.

To properly utilize the stored compressed air the pressure in the receiver needs to be stored at a higher pressure than the system pressure. The strategy is to allow the differential between these 2 pressures to be sustained by incorporating a pressure flow controller (PFC) and/or metering valves.

This allows the pressure in the demand side to be reduced to a stable level that minimizes actual compressed air consumption. PFCs are added after the primary receiver to maintain a reduced and relatively constant system pressure at points of use, while allowing the compressor controls to function in the most efficient control mode and discharge pressure range. Properly applied, a PFC can yield significant energy savings in a system with a variable demand load.

A professional air audit can determine the proper storage size requirements.

Turn It Off

December 8, 2015December 8, 2015Ken Bean

Those big air compressors in the back that nobody wants to look at consume a huge amount of energy. A 100 horsepower compressor can cost $75,000 per year in energy costs (based on 8,760 hours at $0.10 per kilowatt hour). Utilizing automation, storage and flow control, system balancing and best use practices along with other details, can allow you to turn some compressors off. Just running the above mentioned 100 HP compressor during lunch each day can cost up to $3,000.00 annually.

An Air Audit today could save thousands next year!

Saving Energy On Compressed Air Does More Than Save Money

December 1, 2015August 3, 2016Ken Bean

Approximately 70% of all manufacturers have a compressed air system. These systems power a variety of equipment, including machine tools, material handling and separation equipment, and spray painting equipment. Energy audits conducted by the U.S. Department of Energy (DOE) suggest that over 50% of compressed air systems at small to medium sized industrial facilities have low-cost energy conservation opportunities.

Significant air emissions are released when electricity is produced. A recent study for the state of Minnesota, indicated that one-fourth of the energy-related emissions of carbon dioxide, sulfur dioxide, lead and mercury are from generating electric power. Industry uses over 34% of this electricity. Reducing electricity used by compressed air systems will help improve everyone’s air quality.

A team of qualified auditing engineers is the correct way to evaluate your system.

Contact me today to schedule a consultation.