Energy Efficiency: Compressed Air Systems

This is the last article of a five-part series on industrial energy efficiency. This month we will address how Compressed Air Systems are prime targets for energy efficiency measures.

Compressed air is used in many industrial processes, such as sandblasting, injection molding, spray painting, and equipment heating and cooling, to name just a few. Air compression motors have high electrical demands. In fact, up to 20% of total electrical use in certain industries can come from air compression systems.

Which makes these systems prime targets for energy efficiency measures.

High Maintenance

If you use compressed air equipment, you probably know that the cost of the equipment itself is often a fraction of the cost of operating and maintaining it.

In fact, the cost of operating a compressor for just one year usually equals or exceeds the initial cost of the unit. So a reduction in operation and maintenance expense will create substantial savings over the lifetime of the system.

Let’s take a look at some of the low-cost or no-cost measures that can help minimize the expense of operating compressed air systems.

Air Leak Surveys

An industrial plant that has not been well maintained will typically leak about 20% of total compressed air production capacity. But this can be reduced to less than 10% of compressor output by proactively detecting and repairing leaks.

The best way to detect leaks is to use an ultrasonic acoustic detector. This device can recognize the high frequency hissing sounds associated with air leaks.

The units are portable and consist of directional microphones, amplifiers, and audio filters. They typically use either visual indicators or earphones to detect leaks.

Ultrasonic detectors filter out background noises within the audible range. As a result, leaks can be heard in even the noisiest environments.

The benefits of ultrasonic leak detection include versatility, speed, ease of use, the ability to perform tests while equipment is running, and the ability to find a wide variety of leaks. In addition, any operator can become competent after about 15 minutes of training.

Fixing Air Leaks

Air leaks occur most often at joints and connections. Which means stopping leaks is often as simple as tightening a connection. But it can also be as complex as replacing faulty equipment (couplings, fittings, pipe sections, hoses, etc.).

In many cases, leaks are caused by bad or improperly applied thread sealant. This is why it’s so important to select high-quality components, and install them properly with the appropriate thread sealant.

Did you know that non-operating equipment can be an additional source of leaks? To remedy this problem, any equipment no longer in use should be isolated with a valve in the distribution system.

You can also reduce air leaks by lowering the demand air pressure of the system. The lower the pressure differential across a hole or leak, the lower the rate of flow. A lower rate of flow translates into reduced leakage rates.

 

Once leaks have been repaired, the compressor control system should be re-evaluated and adjusted (if necessary) to realize the total savings potential. A proactive leak prevention program will go a long way toward improving the performance of your plant’s compressed air systems.

Recovering Waste Heat

As much as 80%-90% of the electrical energy used by an industrial air compressor is converted into heat. In many cases, a heat recovery unit can recover 50%-90% of this available thermal energy and put it to use heating air or water.

Typical uses for recovered heat include supplemental space heating, industrial process heating, and water heating. (Recoverable heat from a compressed air system is usually not hot enough to produce steam directly.)

For example, packaged air-cooled, rotary screw compressors are very amenable to heat recovery for space heating or other hot-air uses. Packaged compressors are typically enclosed in cabinets and already include heat exchangers and fans. So the only system modifications needed would be additional ducting (and possibly another fan).

Similarly, by using a heat exchanger, you can produce hot water. This is done by extracting waste heat from the lubricant coolers found in packaged water-cooled, reciprocating or rotary screw compressors.

Compressed Air Storage

An effective control strategy for your compressed air system should include adequate storage.  Employ storage to cover peak air demands by strategically locating receivers. This reduces both the amount of pressure drop and the rate of pressure decay.

For systems with highly variable air demand, you can achieve tight control by combining storage with a pressure/flow controller.  Narrowing the pressure variation with better controls not only uses less energy; it also minimizes any potential negative effects on product quality.

A Final Note

The final low- to no-cost measure recommended for improved energy efficiency pertains to inappropriate uses of compressed air. These include any application that can be done more effectively or efficiently by another method. The following table illustrates:


Sources:

Sustainable Plant

Compressed Air Best Practices

US Dept. of Energy

Univ. of Minnesota Technical Assistance Program


Energy Efficiency: Battling Start-Up Spikes

This is the fourth article of a five-part series on industrial energy efficiency. This month we cover Part Four of the series: Start-Up Spikes. This occurs whenever energy-consuming equipment and systems are started simultaneously.

Start-up spikes are an all-too-common occurrence in most manufacturing and distribution facilities. When energy-hogging equipment is started up at the beginning of a shift, it can often lead to unintended peak-demand energy charges.

But these spikes can also be a problem for any commercial buildings where lighting and HVAC systems kick into high gear at the same time each day.

Hard Starts

In the manufacturing and warehouse environment, start-up spikes result when multiple mechanical systems are turned on simultaneously. These “hard starts” can result in additional energy costs. But they’re also rough on equipment, causing premature wear and tear.

That’s because the inrush current from a hard start is often five to six times a motor’s full-load running current. This massive current creates heat in the motor windings, and heat can kill a motor over time.

One solution to this problem is a “soft starter.”

Soft Starters

Soft starters ramp up the voltage gradually, thereby limiting the inrush current. Here’s how: Every time your compressor, pump, or machine starts, the soft starter limits the current for about the first five seconds. It then reverts back to normal running conditions. This results in a more gradual increase of current and eliminates the spike.

The gradual increase in voltage significantly reduces heat buildup. Which ultimately results in an extended lifetime of the motor – particularly of motors that are stopped and started frequently.

In fact, a soft starter will allow you to turn a motor on and off much more frequently without damaging the windings. And for motor applications that involve intermittent loads, a soft start may enable you to shut the motor down in between loads, rather than running it continuously.

Variable Frequency Drives

At the high end of the starter spectrum is the variable frequency drive (VFD). VFDs are typically used for motor speed control, but they can also be used on small motors where they function as motor starters only.

The benefits of using a VFD include:

  • Reduced current starting
  • Communications to a central building management system, and
  • Easy interface for automatic control.

But these benefits come at a cost: increased complexity, increased installation costs, and sensitivity to the environment in which the VFD is installed. Also, additional equipment is often required to support VFDs (such as filters and surge protectors), which further increases cost.

Staging the Start-Up

Another technique for eliminating start-up spikes in factories and warehouses is to stage equipment to come online just in time (that is, sequentially, rather than simultaneously). By gradually ramping up mechanical equipment in a staged manner, excessive energy charges can be avoided without compromising production output.

Equipment start-up can be sequentially staged any time power has been interrupted through a “load control system.”

This staging of load ensures that power quality is maintained and any on-site generators are not overloaded during start-up. In addition to the sequential start-up, the load control system would monitor on-site generators, removing power load from the system if the generators become overloaded.

A Case Study

Start-up spikes can sometimes go undetected unless you’re monitoring your energy data. The following situation, reported by Industrial IP Advantage, is a case in point:

A manufacturer’s energy consumption profile documented a significant spike in demand that occurred monthly, without fail, on the same day and at the same time. A submeter pinpointed the source of the spike. During lunch break on the same day of the month, the maintenance staff simultaneously started all of the production equipment for testing purposes.

Staging the start-up – achieving a steady state with one system before turning on the next – would avoid the spike. But the optimal energy management strategy also included scheduling the once-monthly testing at 6 a.m. during the power utility’s off-peak demand period. The bump in overtime costs is minimal relative to paying peak rates over the course of an entire year.

This example underscores the importance of routine energy monitoring, so that start-up spikes can be pinpointed and eliminated before they become a problem.

Next Up…

Up to 20% of total electrical use in certain industries comes from air compression systems. Our last article in this series will address how these systems are prime targets for energy efficiency measures.


Sources:

DS&O Electrical Cooperative

Cummins

Industrial IP Advantage

Consulting-Specifying Engineer


Energy Efficiency: Are Weeknight Setbacks Worth the Trouble?

This is the third article of a five-part series on industrial energy efficiency. This month we cover Part Three of the series: Weeknight Setbacks. This is the practice of reducing or eliminating an industrial facility’s energy usage during weeknight off-periods.

Energy is complex. With so many moving pieces, it’s easy to get overwhelmed when trying to improve efficiency. And industrial facilities, with multiple independently-controlled systems, are equally complex.

Let’s see if we can’t simplify the strategy for setting up a weeknight setback procedure in your facility.

Identify the Baseload

First, identify the amount of energy used during weeknight off-shift periods.

Buildings don’t turn off at night, they turn down. Overnight load (or “baseload”) is something you always want to minimize if your facility is unoccupied. It sounds like a no-brainer, but even the most efficient buildings may present a baseload energy management opportunity.

Differences in baseload are often easy to spot. For instance, if you’re seeing only shallow drops in energy demand, that probably means that few pieces of equipment are actually shutting down during these off-periods.

Ask yourself, “What do we turn off on Saturday night that we don’t on weeknights?”

A Walk-Through Energy Audit

A walk-through audit of your facility after hours can really shed some light.

  • Is there any equipment routinely left on that could be shut off? Any motors operating unnecessarily (such as a ceiling fan in an unoccupied space)?
  • What about computers and office equipment? Any that don’t go into “sleep” mode after a period of inactivity? This could be a real power drain.
  • With regard to lighting, occupancy sensors and timers can capture significant energy savings. But they need to be combined with lighting systems that can be effectively controlled. Is your staff trained to turn off all lights when closing?
  • Space heaters are huge energy hogs. If they’re being used in your facility, that usually indicates poor HVAC system control. You’ll want to investigate.
  • Is your rooftop ventilation unit equipped with exhaust fans? You can set them to run only when spaces are occupied.

Temperature Setbacks

Did you know that heating and cooling your facility can account for up to 50% of your energy use?

One of the most cost-effective means of reducing energy consumption is by setting the temperature back during weeknight off-periods. (Typical thermostats are set between 65°F to 70°F for heating and 72°F to 78°F for cooling.)

The Department of Energy projects that you can reduce your energy cost by  5% – 12% with a 3°F to 10°F setback. A 10°F to 20°F setback can result in a 9% – 18% energy cost reduction!

 

Programmable thermostats are typically classified as three types:

Electromechanical thermostats use an electrical clock and a series of pins and levers to control temperature. These are the least expensive programmable thermostats. They’re also easy to control, but offer limited flexibility.

Digital thermostats allow you to tailor settings to varying schedules for different days of the week, or up to four different “setpoints” per day.

Occupancy sensor thermostats maintain the setback temperature until triggered by a person entering the controlled space. The trigger mechanism can be a switch, button, light, or motion sensor.

Is It Worth It?

Once you’ve implemented a weeknight setback program, you need to determine if it’s paying off.

Fortunately, new technologies now allow industrial businesses to compare energy use over time to see how setback sequences change. Having access to historical demand data to create a relative performance benchmark is a key consideration when contemplating an energy efficiency strategy.

According to the Department of Mechanical and Aerospace Engineering at the University of Dayton, the easiest way to track your progress is by using data analysis software that compiles available temperature, production and utility billing data.  Anything more complicated may be too complex for widespread use.

The EPA’s Energy Star Portfolio Manager is a reasonable choice. Not only does this online tool measure energy and water consumption, but it tracks greenhouse gas emissions as well. And it can be used to benchmark the performance of a single building or multiple buildings.

Up Next…

Hard starts are rough on equipment, causing premature wear and tear. And they can lead to unintended peak- demand charges. Our next article, “Start-Up Spikes,” will look at how to avoid them.


Sources:

Business Energy Advisor

NC Energy Office

Gridium.com


Why Are Wood Pallets Heat Treated?

Did you ever wonder why wood pallets are heat treated?

What’s the purpose of the heat treatment, and when did it all begin?

Infestation!

ippc-logo-screen-largeIn 1951 a group called the International Plant Protection Convention (IPPC) was formed under the auspices of the Food and Agriculture Organization (FAO) of the United Nations. The IPPC’s purpose was to “protect cultivated and wild plants by preventing the introduction and spread of pests.”

But by the 1990s, a large number of newly established exotic bark- and wood-infesting pests was being reported worldwide. The IPPC noted that there was a strong association between these infestations and wood packing materials, particularly crates and pallets.

The Asian Longhorned Beetle

The following infographic highlights the problems caused the the Asian Longhorned Beetle, a common pest found in untreated wooden pallets and crates:

Infographic Courtesy of Visual.ly

The Emerald Ash Borer

The dreaded emerald ash borer, was another serious concern. This tiny creature has been known to totally devastate large populations of ash trees. Here’s how our Canadian neighbors are responding to the problem:

ISPM 15 to the Rescue!

The Asian beetle, ash borer and other wood-boring pests had to be stopped. So the IPPC got together in March of 2002.

The group decided that all solid wood packaging must be heat-treated or fumigated before they can be imported into any of IPPC’s 182 member countries. This new regulation was called ISPM 15. (ISPM stands for International Standards For Phytosanitary Measures.)

pallets_ispm15_for_international_shippingWith the implementation of ISPM 15, the pallet business was forever changed.

The goal of ISPM 15 is to “reduce significantly the risk of introduction and spread of most quarantine pests.” There are only two established methods for reducing the risk of wood pests:  heat treatment and fumigation with pesticides (usually, methyl bromide).

However, due to increased health concerns and ozone depletion associated with methyl bromide, heat treatment is the preferred method.

How Does Heat Treatment Work?

In the heat treatment process, wood pallets are placed in a special chamber (like the one shown at the top of this page). The pallets are then heated until the wood’s core temperature reaches 132.8 degrees Fahrenheit. This temperature must be maintained for at least 30 minutes to comply with ISPM 15.

Once heat treatment is complete, the pallet is stamped with a mark of compliance, like this one:heattreat

Advantages of Heat-Treated Pallets

In addition to their pest control properties, heat-treated pallets offer several other advantages:

fig2_art08

Heat treating wood adds longevity and quality. Did you know that when wood is heat treated, its composition is actually altered?

It’s true. As a result, the heat-treated wood is less likely to decompose, even when exposed to dampness and extreme humidity.

Heat-treated pallets are also more resistant to fungi and other microorganisms that contribute to wood rot. Heat treating also hardens the wood and makes it less permeable, thus preserving the wood’s longevity while also reducing swelling and shrinkage.

Heat-treated pallets are environmentally sound. No chemicals are used in the manufacture of heat-treated wooden pallets, and they do not add any toxic stress to the ozone layer. They can also be recycled as wood chips and repurposed, so that nothing really goes to waste.

cargoshipwithshippingcartonsHeat-treated pallets are lighter in weight. Heat treating reduces moisture in the wood and makes it moisture resistant. The end result is a pallet that weighs less, saving money on shipping costs.

Heat-treated pallets are accepted internationally. International standards that regulate heat-treated wooden pallets in compliance with ISPM 15 are strictly enforced. With heat-treated pallets, wares can move freely across international boundaries without facing any shipping restrictions.


Sources: