Compressed Air Systems

Pros and Cons of Individual Compressor Controls

Previously we described the 6 different types of Basic Air Compressor Controls but what kind of control would you want for your compressor. Her are few pros and cons of the controls to help you assess the needs of your compressor.

Start/Stops

Pros

  • Simple control using only a pressure switch
  • Motor and compressor operate only when needed which saves energy
  • Good for small compressors that are 25 HP or less (depending on application)

Cons

  • Frequent starting wears down motor and compressor
  • Pressure setting to stop must be higher than required system pressure to build storage and may increase energy use
  • Loses of pressure control in the range of 35 psi
  • Limited to small compressors

Load/Unload

Pros

  • Motor compressor runs continuously which reduces wear  and tear associated with too many frequent motor starts
  • Tighter range of pressure (approx 10 psi)
  • Provides adequate storage and offers energy-efficient control of rotary screw, reciprocating and some centrifugal compressors

Cons

  • If applied incorrectly short cycles cause  premature wear and tear. There is minimal or no power savings on lubricant-injected rotary screw compressors
  • There needs to be proper blow down time and the storage capacity required for lubricant-injected rotary compressors to achieve energy savings and prevent lubricant foaming
  • Requires over-pressurizing to maintain minimum system pressure

Modulating

Pros

  • The motor and compressor run continuously reducing wear
  • Tighter range of pressure control (10 PSI)
  • Steady progressive capacity control that matches demand

Cons

  • Pressure ratios increase as inlet pressure is throttled
  • Inefficient at lower loads(lubricant-injected rotary compressors limited to 40-60% capacity; centrifugal compressors limited by potential surge and may require discharge blow off)

Dual/Auto Dual

Pros

  • Combines features of modulating, load/unload. and start/stop
  • Shuts down compressors when unloaded for pre-set duration which in turn saves energy
  • Better selects operation mode for small reciprocating compressors

Cons

  • Makes the control complex
  • The Over-run timer must be set to limit premature starting and stopping

Variable Displacement

Pros

  • Energy-efficient control scheme that gets down to 50% of capacity
  • Matches displacement to demand without reducing inlet pressure or increasing ratios of compression

Cons

  • Makes the control complex
  • High initial cost
  • Only available for 50 HP+ compressors

Variable Speed

Pros

  • Energy-efficient and precise control
  • Various rotating speeds and giving more displacement and power. These are directly proportional to speed rotation

Cons

  • Makes the control complex
  • High initial cost
  • Reduced full load efficiency
  • Efficiency of rotary screw compressor ends drop at lower or higher speeds

The 6 Types of Basic Individual Compressor Controls

Compressor controls are designed to match compressor delivery with compressed air demand, by maintaining the compressor discharge pressure within a highly specified range.  This discharge pressure should be set as low as possible to minimize the energy usage.

Compressor systems are typically composed of multiple compressors delivering air to a common plant air header. The combined capacity of these machines is generally sized to meet the maximum plant air demand. System controls are almost always needed to orchestrate a reduction in the output of the individual compressors during the times of having lower demand. Compressed air systems are usually designed to operate within a fixed pressure range and to deliver a volume of air that varies with system demand. System pressure is monitored and the control system decreases compressor output when the pressure reaches a predetermined level. Compressor output is then increased again when the pressure drops to a lower predetermined level.

There are 6 basic types of individual compressor controls that a person has to take into account when looking into purchasing and using air compression:

Start/Stop

  • Turns the motor which drives the compressor on or off in response to a pressure signal (seen on reciprocating and rotary compressors)

Load/Unload

  • Allows the motor to run constantly but unloads the compressor when a predetermined pressure is reached. The compressor reloads at a predetermined lower discharge pressure. This is also sometimes referred to as constant speed or constant run control (seen on reciprocating, rotary, and centrifugal compressors).

Modulating

  • Restricts passage of air to the compressor to progressively reduce compressor output to a specified minimum, when the compressor is then unloaded. This is also referred to as throttling or capacity control (seen on rotary and centrifugal compressors).

Dual/Auto Dual

  • This controller is commonly seen in small reciprocating compressors, allows the selection of either Start/Stop or Load/Unload. When used in a lubricant-injected rotary compressor it provides modulation or load/unload control to a preset reduced capacity. When unloading the addition of an over-run timer will stop the compressor after running unloaded for a preset time.

Variable Displacement

  • This controller allows progressive reduction of the compressor displacement without reducing the channel opening (seen on reciprocating and rotary compressors).

Variable Speed

  • This controller adjusts the compressor capacity by varying the speed of the electric motor driving the compressor in response to system signals.

Learn more about the these six basic compressor controllers and more about other FS Curtis products

10 Steps to Saving Compressed Air System Operating Costs (6-10)

Small adjustments can reduce your operating pressure and energy costs while improving flow rates and output. Learn the final steps you can take to optimize your compressed air system and save energy costs. Make sure that you also know the first 5 things you can learn to "Save your Compressed Air System Operating Costs"

  1. Review Piping Infrastructure. Many systems aren't optimized.
    A piping system design should optimize transfer of compressed air at the desired flow and pressure to the point of use. Increasing the size of a pipe from two to three inches can reduce pressure drop up to 50 percent. Shortening the distance air has to travel can further reduce pressure drops by about 20-40 percent.

The more flow through a pipe the greater the pressure drop will be. Pressure drop in a pipe increases with the square of the increase in flow, which means if the flow is doubled, the pressure drop will increase four times. Air distribution piping should be large enough in diameter to minimize pressure drop.

How can FSC features and benefits help with this step? If your compressed air piping system was installed years ago when your compressor was much smaller, this might be an indication that the distribution pipes are too small.  A quick guide is to look at the air compressor outlet size. If your distribution piping is smaller than your air compressor outlet size, then it may be time to get your FS Curtis Distributor in to evaluate your piping system. If up-grades are needed, FS Curtis offers a modular, aluminum piping system that is easy to install and is a cost effective alternative to copper or steel piping.

 

  1. Change Filters Systematically. Not every once in a while.
    Inspect and replace filters systematically to ensure the quality of your air and prevent pressure drops. Go beyond the air compressor and compressor room. There are several air-line and point-of-use filters within the facility. Those are just as important to maintain as the air compressor and air compressor room filters.

How can FSC features and benefits help with this step?  Your FS Curtis Distributor will provide you with a complete Filter Package located on your compressed air system supply side.  Your process and type of equipment used will determine the level of air quality needed.  If you are not sure what you need, ask your FS Curtis Distributor who can guide your selection using an industry standard selection chart.

 

  1. Recover Heat. Compressing air generates heat - reuse it!
    It's simple physics that compressing air gives off heat, and as much as 90 percent of that heat can be recovered for use in your operation. For example, you can produce hot water for washrooms or direct warm air into a workspace, warehouse, loading dock, or entryway. The savings can really add up.

How can FSC features and benefits help with this step?  A simple heat recovery step can be making sure the hot air from your compressor room is directed into a nearby work space. If you have a larger rotary screw compressor with and e-COOL® Technology, you may find capturing the exhaust air from your air compressor and ducting into your facility during the heating season.  More aggressive heat recovery systems can be used to pre-heat water or process materials if you operate larger compressor systems.

  1. Emphasize Proper Maintenance. Ignoring maintenance costs more.
    As with most industrial machinery, a compressor runs more efficiently when properly maintained. Proper compressor maintenance cuts energy costs around one percent and helps prevent breakdowns that result in downtime and lost production. Protect your reputation and profits with proper maintenance.

How can FSC features and benefits help with this step? Your FS Curtis i-Command® Touch Control will help monitor your compressor for items needing maintenance as well as sending signals showing maintenance alerts.  Having your FS Curtis Distributor establish a scheduled service interval based on the number of hours your compressor runs per year will save you money in the long run.  Take advantage of your Extended Warranty by using correct parts and lubricants at the correct time. If you skip service and don’t do maintenance, then you can expect that future warranty claims if needed, may be rejected.  Just like you car, if you don’t take care of it, it won’t take care of you!

  1. Identify and Eliminate Inappropriate Uses of Compressed Air.
    Inappropriate uses of compressed air include any application that can be done more effectively or more efficiently by a method other than compressed air. For example, high pressure air often is used for cooling or applications where much lower air pressure is required.

How can FSC features and benefits help with this step? Your FS Curtis Distributor can help you with this. If you have a Compressed Air Leak Survey scheduled, the Auditor normally is looking for inappropriate uses of compressed air at the same time.  Common mis-uses are: blowing off a work station with an air gun instead of using a hand brush; using an air stream as a personal cooler instead of a fan; Plus many, many more ways…..

10 Steps to Saving Compressed Air System Operating Costs (1-5)

The first step to reduce compressed air energy costs is to measure and monitor your compressed air system's energy consumption, flow rates and operating air pressure. Your FS-Curtis Distributor can help you with your understanding of your compressed air system through an assessment or audit of your system.  The FS-Curtis Distributor will provide you with a report which will help you see how your air compressor(s) are being controlled, how much energy they are using, and how much air flow and pressure you system is using.  Recommendations can be made to help your reduce your operating costs and return those losses back into profit for your business.  Small adjustments can reduce your operating pressure and energy costs while improving flow rates and output. Here are 10 steps you can take to optimize your compressed air system and save energy costs.

  1. Turn It Off.
    There are 168 hours in a week, but most compressed air systems only run at or near full capacity between 60-100 hours. Depending on your shift pattern, turning your compressors off during the evenings and weekends could reduce your energy bills up to 20 percent.

How can FSC features and benefits help with this step?  Here’s a suggestion to help you turn off your compressor effortlessly.   Look into the FS Curtis Nx Series of Air Compressors using the i-Command® Touch Control. This advanced compressor controller can be set to turn off your air compressor at the end of a shift or work day automatically.  Another energy-saving option i-Command® Touch Control is to allow the system to reduce the system pressure during non-production hours.  Let’s say you operate several CNC machines which need to keep 80 psi in order to maintain the tool settings. So your  i-Command® Touch Control can be set to reduce the system pressure down to the 80 psi range during your off shifts.  This saves you electric costs because for every 2 psi you can drop your system pressure, you reduce your electric costs by 1%.  So that 20 psi reduction just reduced your electric usage by 10% for the non-productive hours…

  1. Fix Existing Leaks.
    A quarter-inch air leak at 100 psi will cost you more than $2,500 a year. Pipe systems, hose connections, and filter/regulator housings older than five years can have leaks of up to 25 percent. Because it takes energy to generate compressed air, any air that leaks is money wasted. Approximately 80 percent of air leaks are not audible, so to minimize these problems, third-party help in detecting these leaks may be a necessity.

How can FSC features and benefits help with this step? Your local FS Curtis Distributor can help you with a leak survey using an ultra-sonic leak detector.  They can find leaks in your system and pneumatic equipment without shutting down your production. The survey will provide you with a list of items needing attention and repair. Your utility may offer a cost sharing program to help pay for the survey. You can have your maintenance team make the repairs or have your FS Curtis Distributor make the repairs.

  1. Prevent New Leaks.
    As Benjamin Franklin said, “An ounce of prevention is worth a pound of cure.” So, be proactive and look inside your piping system. A clean, dry pipe indicates good quality air and no corrosion issues. Dust in the pipe is caused by particles in the compressed air. If compressed air is not filtered, or if the filter is clogged, pressure drops will occur and the risk of end product contamination will increase. Sludge in the pipe is bad news and must be fixed immediately. Dust and sludge in a compressed air piping system will cause corrosion very quickly and will greatly increase the number of leaks. Dried and filtered compressed air keeps piping clean.

How can FSC features and benefits help with this step? Your FS Curtis Distributor will often recommend installing a Flow Meter at the point where your compressed air leaves the compressor room and flows to the “Demand Side” of your air system.  Some Flow Meters can be tied into your building’s data logging equipment. If you don’t have a data logging system, just setting up a simple log sheet so when your maintenance staff make their daily check on the air compressor, they can write down the flow rate seen on the Flow Meter screen.  If you start to see an increase in the Flow numbers, it’s time to start to investigate.  Did you add new equipment that takes more air? Did a process change? If nothing changed, its time to look for air leaks again!

  1. Reduce Pressure. Run at required pressures, not beyond.
    Each two psi reduction cuts energy consumption one percent. Check the system pressure and resist the urge to turn up the pressure to compensate for leaks or drops in pressure due to piping problems or clogged filters. A central supply side controller can greatly reduce the operational pressure band and orchestrate air production much more efficiently and effectively.

How can FSC features and benefits help with this step? Your FS Curtis Distributor is a good resource to help you. They can help you establish a pressure profile of your facility. Let them help you find what process or equipment is needing the highest pressure.  Often we find air supply systems running at 15 to 50 psi higher than what is really needed.  A simple DemandSmart® Flow Controller may help you manage your demand side pressure and flow. Not only will you reduce your energy bill, but your facility may have less wear on air tools and improve your product quality due to a constant air pressure in our plant.  Have your FS Curtis Distributor include checking needed down-stream point of use filters for pressure drop and clogged filters.  Sometimes folks crank up the pressure to get more pressure to the equipment, when a change in the filter element is really needed.

  1. Check Drains. Are your condensate drains stuck open?
    Condensate drains on timers should be adjusted periodically to ensure they open as intended or aren't stuck open. Better yet, replace timer drains with zero-loss drains to stop wasting compressed air.

How can FSC features and benefits help with this step? First, when you purchasing a new air compressor select an energy saving zero-loss drain. While the zero-loss drain may have a higher investment price, you will not be losing compressed air every time the timer opens the drain valve. The opening of the timer drain can cause the compressor to come on for a short period of time causing an unneeded motor start and extra wear on the air compressor.  Always make sure your FS Curtis Distributor is checking your auto drains for correct operation when they are doing your scheduled maintenance.

See the Final Steps to Saving Compressed Air System Operating Costs

What Can I Do to Reduce the Cost of Operating My Compressed Air System?

This is a question that a business owner should ask…   What can I do to reduce the cost of operating my Compressed Air System?

For years now, the whole industrial world has been listening to the experts that want to help you reduce your electric bill by selling you a more energy lighting system, heating and air conditioning system, speed controlled pumps, and automatic “do-dads” that promise a lower power bill.  The Air Compressor industry has been drawn into this energy-saving charge because in most facilities, the electric motor in the compressed air system can be the largest and most powerful electric device in the building. So the air compressor has become one of the favorite targets of the utilities wanting to reduce the peak load on a local power grid. You’ve heard all of the sales pitches now from both the compressor guys and the power companies. But there may be low-cost actions you can take to make your compressed air system more efficient and further reduce your monthly electric bill.

First, find ways to reduce your existing air systems’ operating costs. You may not need to pay for a compressed air system audit, unless you don’t have the time or experienced staff to conduct your own system assessment. Sometimes, just focusing your facilities manager on reducing the cost of the compressed air system can work. Sometimes having a trusted air compressor vendor works well. And sometimes you may need the help of a paid compressed air auditor if you’re budget allows.  However, as a starting point there are some things you can do on your own first.

According to CAGI (Compressed Air and Gas Institute), the most expensive component in the total cost of compressed air is energy. In fact, over the lifespan of a typical compressor, energy typically costs several times more than the purchase price of the compressor. The bottom line, maximizing energy efficiency saves you money.

At the beginning, you must know what your compressed air system is doing and why.

  • What is the highest pressure required by your equipment and processes?
  • What equipment and processes require the highest pressure?
  • What machine or process truly needs that much pressure and flow?
  • How clean and pure must your compressed air supply be in order to not cause product “do-over’s” caused by water or oil in the air lines?
  • What is the lowest and the highest rate of flow to the demand side of the piping system, and what causes the increased demand for flow?

If you can’t answer these basic questions for your compressed air system, then you really don’t understand or manage your compressed air system effectively.  And you are probably wasting a lot of money that could easily be turned into profit dollars.

The first step to reduce compressed air energy costs is to measure and monitor your compressed air system's energy consumption, flow rates and operating air pressure. Your FS-Curtis Distributor can help you with your understanding of your compressed air system through an assessment or audit of your system.  The FS-Curtis Distributor will provide you with a report which will help you see how your air compressor(s) are being controlled, how much energy they are using, and how much air flow and pressure you system is using.  Recommendations can be made to help your reduce your operating costs and return those losses back into profit for your business.  Small adjustments can reduce your operating pressure and energy costs while improving flow rates and output.

Learn about the 10 Steps to Saving Compressed Air System Operating Costs (1-5)