Rotary Air Compressor

FS-Curtis Assists Those in the Fabricated Metals Industry

Compressed Air is an integral part of the Fabricated Metals Industry. Premier Tool Grinding manufacturer of carbide cutting tools uses our NxB22 along with our RNE Dryer and CF Filtration system. See how we assist companies like Premier Tool in the Fabricated Metals Industry.
Many processes and applications continue to use inefficient devices to deliver the compressed air, and many companies fail to recognize the simple implementation and significant payoff of improving compressed air efficiency.

Improving compressed air efficiency, or saving more of your compressed air capacity by minimizing compressed air demand, can be realized by following some simple procedures. Though there are many actions that can be taken to further improve compressed air efficiency, some simple and effective steps can be put to action quickly.

A few things you need to do to improve the demand of your air compression: Measure the air consumption to identify sources that waste compressed air Find and fix the leaks in your compressed air system. Upgrade your blow off, cooling and drying operations using engineered compressed air products. Use intermediate storage of compressed air near the point of use Control the operating air pressure at the point of use to minimize air consumption.

Why not take your compressed air to the next level by seeing the services and products that FS-Curtis can offer?

 

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

4 Ways to Get Efficient Rotary Air Compression for the Summer

4 Ways to Get High Level Rotary Air Compression for the Summer

With high summer temperatures fast approaching please make sure your Rotary Compressor is prepared for the change in climate. Here are 4 tips to keep your Rotary Compression at peak performance for the summer.

  1. Lubricant and Coolant Levels

Is your lubricant and coolant low? Is it due for a fluid and filters service? Please note that running FS-Curtis synthetic fluids will reduce the heat generated by your compressor. The compressor oil serves as coolant in oil flooded rotary compressors. In rotary compressors, the compressor oil is circulated 7 or more times per minute through the machine. This is why oil levels become more critical in the summer. To be sure of the condition of your air end and bearings we recommend an oil analysis by any of one of distributors.

  1. Air Density

In the summer your compressor will have a lower performance. Make sure you install a new intake filter for the hot summer days. Please be aware that dirtier environments require more frequent intake air filter changes.

  1. Having Clean Compressor Air and Oil Coolers

A clean cooler may be the difference between normal operation and a high temperature shut down. Many times synthetic compressor oils are fruitless because the oil breaks down prematurely due to overheating. To protect from high acid numbers, loss of lubricity and increased viscosity, long oil change intervals must be monitored with frequent lube analysis, particularly when exposed to high ambient temperatures. Please contact your local FS-Curtis service company for a compressor “health” check.

  1. Hot Ambient Air and Moisture

Most lubricated, air cooled, rotary screw compressors run 100 to 110 degrees F above the ambient temperature. If your compressor room is over 100 degrees, you are already in trouble. Cross flow ventilation is advisable in non ducted compressors. If your compressor oil sump or airend discharge is more than 120 degrees F over ambient temperature in the room, you need to find out why. FS Curtis has factory approved Air Treatment accessories to minimize moisture in your system and water in the air lines.

What To Consider When Purchasing a Rotary Air Compressor?

Let’s say you buy a Volvo, arguably considered one of the safest cars on the road, and you drive it 70 mph into a brick wall (by the way, don’t do this, it ruins the paint job), is it the car’s fault that it may no longer run?

The same scenario applies to equipment. If the OEMs installation recommendations are not adhered to, there will be a high degree of probability that the compressed air equipment will not be reliable, will not experience the stated longevity, may require above average maintenance, may consume more electrical energy than required and may not consistently provide the compressed air quality required by production.

While it’s impossible to cover all of the things you need to consider when installing a rotary air compress (and we hope it’s an FS-Curtis), this short article is intended to help avoid the equivalent of driving your car into a brick wall.

Electrical

1) Have your system voltage measured. The most common electrical utility voltages in the United States are 200 volt, 208 volt, 230 volt, 460 volt. Electrical utilities guarantee a voltage supply tolerance of + 10%.  For example, if the voltage stated supply is 230 volts it could measure at any given time from 207 up to 243 volts. Most electrical utilities attempt to hold the supply voltage to + 5%. Operating electrical motors off design or away from their nameplate voltage will generate additional heat leading to reduced motor life expectancy. The majority of induction motors, 5 hp through 600 hp supplied to the U.S. market, are 230 & 460 volts; however, 200 & 208 volt systems are becoming more popular. If a 230 volt name plated motor is operated on a 200 to 208 volt system it will operate in an elevated heated condition leading to extremely reduced motor life. This is not a recommended practice. There are motors specifically designed for 200 & 208 volt operation. For these applications motors name plated as such should be used.

2) Many air compressors operate into the motor service factor. As such, request the package full load operating amp draw from the manufacturer to properly size the electrical utility supply equipment (i.e., wire, electrical quick disconnect, overloads, transformers). Seek out a qualified electrical contractor in your area to assist in proper electrical utility modeling and sizing.

Placement

1) Proper placement and mounting is vital. Request a General Arrangement (GA) drawing from the OEM for each piece of compressed air equipment purchased. The GA drawing should illustrate the weight and recommended clearances to be maintained around the equipment. The floor will need to support the static weight of each piece of equipment. The equipment should be secured to the floor to prevent it from shifting around imparting stress on connected utilities such as piping, electrical and ducting. In addition, many states have adopted seismic codes mandating equipment be structurally secured to the floor. Many floors appear flat to the eye but are not flat enough to meet accepted equipment mounting practices. Many floors can be crowned (bowed) or have undulations. When securing equipment to a floor it is important to identify floor imperfections filling the air gaps with shims. When properly shimmed, the tightening of the mounting bolts will not bend or distort the equipment frame. Frame distortion will lead to excessive equipment vibration. Excessive vibration causes premature component failure which reduces machine reliability, increases cost of ownership and could potentially create an unsafe situation.

Proper clearances should be adhered to. These recommended clearances provide boundary area around the machine for safe, effective operation and servicing of the machine. This boundary area also allows adequate cooling airflow around the machine.

Piping

All piping should be properly supported as to not impart stress on the equipment. When connecting piping to the equipment pipe connector, it should be supported with proper tooling to prevent the equipment connector from turning during the piping tightening process. If the equipment receiving connector is allowed to turn (rotate) it very well could damage internal components to the equipment. Air piping should be properly sized and configured to prevent short cycling of the air compressor controls. A rule of thumb is to always use piping at least the size of the supply connection of the air compressor. If the dryer connections are larger don’t worry, the reason could be the dryer is oversized due to rerating or simply the fittings are larger to slow the compressed air velocity down through the dryer. The piping exiting the dryer can be the same size as the air compressor connection or the outlet piping size of the dryer can be used to establish the piping downstream of the dryer.

Ambient Air

If the ambient air conditions can drop below 32°F measures should be taken to prevent the compressed air equipment from being exposed to this as it will freeze up. During air compressor operation the most effective way to condition the room temperature is to use the heat generated by the operating air compressor(s). Excessive heat can be discharged from the room by way of a properly sized wall fan. The wall fan can be thermostatically controlled to keep the room at a constant temperature. If there are times when all of the compressed air equipment is not operating, an auxiliary heating system should be considered.

Air-cooled rotary screw air compressors gives off 2545 btus/hr per horsepower.

Example: A 50 horsepower air-cooled rotary screw air compressor discharges 127,250 btus/hr into its surrounding environment.

That is enough heat to keep a 1500 square foot home comfortable in the dead of winter with outdoor temperatures below 32°F.  Many of these air compressors are installed with little thought of eliminating heat build-up around the air compressor. The heat discharged into the ambient air surrounding the air compressor is continuously cycled through the heat exchangers elevating the temperature. Unchecked, the temperature will rise to an unacceptable level, eventually overheating the air compressor & shutting it down. Ducting can be attached to the air compressor to directly route the cooling air discharge outdoors or away from the air compressor. Wall or ceiling fans can also be strategically placed in the room to exhaust the hot cooling air outside. Either way, an adequate amount of replacement cooling air must be brought into the room.

All installations have contaminants in the ambient air. Contaminants can negatively impact an air compressor in many ways. Two critical ways are indigestion into the air compressor itself with the other being fouling of the air-cooled heat exchangers. The best way to determine if the air compressor is digesting an abnormally high amount of contaminants is to consistently perform oil analysis. The oil analysis should look for components not normally part of the oil make-up. The results need to be properly interpreted.

In the case of a lubricated rotary screw air compressor, all of the ambient air drawn into the machine for compression flows right past or through the airend bearings. Too much ingestion of particulate will damage the bearings. The oil not only cools the air during compression it also washes the contaminants out of the air. Over time these contaminants will build up continuing to be cycled through the bearings.

Example:  A 10 micron particle should be able to flow through an anti friction bearing suspended in the oil film without damaging the bearing surfaces.

This does not account for multiple particles clumping together, which will damage the bearing surfaces. Two solutions for reducing digestion of contaminants are to install an air filter with a lower micron rating and higher efficiency rating. The ratings should be adjusted until the oil analysis indicates the level of contaminants is satisfactory. Remember, as the rating of the inlet air filter is increased the surface area should also be increased or the air filter may have to be changed out too frequently from excessive fouling. The second solution is to relocate the inlet air filter to a remote environment which is cleaner than the immediate area around the air compressor. The piping used to remote mount the air filter should be non-ferrous. PVC works great as it is light, easy to assemble and inexpensive. Connect it to the air compressor air end with an easily removable joint in case machine repairs or troubleshooting is required. The piping i.d. should be no smaller than the i.d. opening in the OEM supplied inlet filter mounting assembly. For every 10 feet of inlet pipe run, the pipe diameter should increase one size or 1". If the inlet air filter is relocated outdoors it should be protected from digestion of rain or snow.

Relocation of the inlet air filter is a recommended solution when the surrounding ambient area around the air compressor contains hazardous vapors or fumes. There are air filters which can remove hazardous fumes or vapors; however, they are costly to purchase and maintain.

If you’d like more information about FS-Curtis rotary screw air compressors, please click on the icons below to download product literature. I you have questions or would like more information or pricing, please visit our Distributor Lookup page on our website to locate a distributor in your area.

May 16-18th: Compressed Air Systems Training

FS-Curtis and Compressed Air Challenge have come together to provide Distributors with training and advanced training on air compressors. All of this great training and advanced instruction will take place on May 16th-18 in Philadelphia, PA. Also over the next year if you sell a Nx 60-185 HP compressor you will get your registration refunded.

The conference will be held at Courtyard Marriott in Plymouth Meeting, PA

A good accommodation option:

Springhill Suites

430 Plymouth Rd

Plymouth Meeting PA 19462

610-940-0400

May 16th- Fundamentals of Compressed Air Systems

Find out how a compressed air system works and the benefits of optimal compressed air system performance. This initial class demonstrates how to compute the current cost of your plant's compressed air systems, how to measure and create a baseline of system performance, and how to determine the impact of different compressor control types. Learn basic approaches for cutting costs; identify steps for proper system operation, maintenance, and point-of-use accountability; and tailor a compressed air system management action plan for your plant.

May 17-18: Adv. Management of Compressed Air Systems

This is an intensive two-day training that provides in-depth technical information on troubleshooting and making improvements to industrial compressed air systems. This training is designed to help end users as well as industry solution providers learn how to: Collect and use data and tools to assess the efficiency and cost-effectiveness of a compressed air system; Develop and use a system profile; Implement a system maintenance program; Address air quality, highest pressure requirements and high-volume intermittent applications; Understand complex control system strategies; Align the supply side to demand side operation; Explain the value of heat recovery; and Successfully sell compressed air improvement projects to management. When you register, you will be sent an information packet including materials you will complete prior to the training. This information will be critical as you use data to calculate cost and performance in your specific facility.

 

When Should I Service My Oil Flooded Rotary Screw Air Compressor?

Each manufacturer’s make and model of rotary screw air compressor gives specific guidelines for preventative maintenance in the operations manual sent with the air compressor. You’ve invested a good deal of money in your new compressor, to protect your new investment it’s a wise idea to follow these preventative maintenance procedures. Keep in mind this is not a comprehensive list, but it’s a good start and will help give peace of mind knowing you are not neglecting your air compressor.

Every manufacturer of rotary screw air compressors provide an Operators Manual with specific guidelines for preventative maintenance. You’ve invested a good deal of money in your new compressor, to protect your new investment it’s a wise idea to follow the preventative maintenance procedures. Some compressor designs may require more steps and checks, but here is a good place to start to get the longest life out of your investment

Daily:   Check for abnormalities (unusual sound, vibration, leaks, warnings or alarms on the controller, etc.)

  • Check oil level
  • Monitor temperature and pressure
  • Check control panel for any alarms or maintenance lights

Monthly: Perform Daily checks

  • Clean inlet air filter and enclosure filters.
  • Check operation (load and unload, low and high pressure set-points, maintaining pressure, etc)

Quarterly: Check hour meter and check the maintenance schedule to determine if its time for maintenance to be scheduled. Your compressor may require lubrication change at 2,000, 4,000 or 8,000 hours depending on the manufacturer’s recommendations.

  • Take oil sample if needed
  • Check separator scavenger line flow (if applicable)
  • Check v-belts (if applicable)
  • Perform daily and monthly checks

Semi-Annual or 4000 hours:  Perform Quarterly Check list.

  • Change air/oil separator filters (spin on or drop in type)
  • Take oil sample and sent to compressor vendor

Annual or 8000 hours: Start by checking annual maintenance list for manufacturer’s recommendations:

  • Change lubricant
  • Change air / oil separator (drop in type)
  • Perform quarterly checks

 

Keep in mind; these are the basic maintenance items needed to keep an oil flooded rotary screw compressor in good operation. This preventative maintenance program is designed for a standard condition, but as we all know most installations for air compressors would be considered dirty and dusty environments.

Another factor that is critical to the life of a compressor is the actual run time. All rotary screw compressors underlying guideline for maintenance is hours of operation. Most installations never operate 24 hrs per day / 7 days a week. There are only 8760 hours in a year and anything less than 24 hours will result in lower hours, which affect the amount of maintenance needed for each installation.

So, with all of these factors to consider, what does an owner of an oil flooded rotary screw compressor do to properly maintain the air compressor to ensure long reliable operation?

To answer this question we need to look at several factors:

1)   Environment

First the environment is the one factor that governs all of the others. If your compressor is running in a dirty environment where you have to keep cleaning the coolers externally to keep the compressor cool and the air filter is continually dirty when you inspect it periodically; then you have a dirty environment. Use the monthly recommendations and not the hours of run time.

2) Hours of operation (less than 4000 hrs per year)

In this case the recommendation would be to follow the time frame set out for preventative maintenance as described in the operations manual. Use monthly intervals for filter changes and not the hours of operation as your guide. This means air and oil filters changed every quarter (or more frequently) as well as air/oil separators changed per instruction manual. Please note if you are running 24 hrs / 7 days then air and oil filters will need to be changed in accordance with OEM recommendations.

3) Costs

Costs of preventative maintenance should be only considered as a last resort as it has been proven in many studies that preventative maintenance saves money. A proper preventative maintenance program will translate into more reliable operation and less down times for the owner. This will create a more efficient production process for the owner which generates income on a consistent basis.

In all other instances the OEM manual should be used as a guideline for changing all filters for the proper maintenance your rotary screw compressor.

A properly maintained air compressor can be accomplished by following several practical guidelines and discussing your needs with an FS-Curtis compressed air professional. To learn more download the product information or contact your local FS Curtis distributor.

FS-CURTIS WINS PRODUCT OF THE YEAR FOR THE NX SERIES ROTARY AIR COMPRESSORS

Press Release:
St Louis, MO, May 4, 2016– FS-Curtis/Curtis-Toledo, Inc., a leading manufacturer of reciprocating and rotary air compressors since 1854 has announced that their Nx Series of Rotary Air Compressors has been awarded the prestigious Plant Engineering Product of the Year GOLD Award.
The Nx series rotary-screw air compressor features the iCommand-Touch controller—an intelligent technology that features touchscreen capabilities with bright, full-color graphics. At a glance, users can track pressure, temperature, and usage to easily diagnose and optimize their facility’s air system. The controller graphs information and trends that can be downloaded to an SD card, for troubleshooting and quality control measures. Customers have provided praise regarding the innovative Nx series intelligent package design, which easily allows simple maintenance tasks. The unique design of the motor and fan, coupled with airflow baffling and superior sound insulation, ensures extremely quiet operation. So quiet, the unit can be installed where you need it the most.
“Trusted and dependable reaches a whole new level with our Nx series rotary screw air compressors. The overwhelmingly positive response from customers highlights the quality of the air compressor, which is further reflected in the Nx being selected as the Gold Winner from Plant Engineering,” said Matt Smith, National Sales Director, FS-Curtis. “The entire FS-Curtis team continues to be focused on providing customers with trusted and dependable compressed air solutions that exceed their expectations.”
Plant Engineering's Product of the Year program is a premier award for new products in the manufacturing industry. The annual reader-choice program provides Plant Engineering's audience with information about the top new products in their fields.
About FS-Curtis/CURTIS-TOLEDO, Inc.
Since 1854, FS-Curtis/CURTIS-TOLEDO, Inc. has been designing and manufacturing solutions for industry. The FS-Curtis Air Compressors brand continues to be the symbol of quality and excellence in the design and manufacture of air compressors. Dedicated to customers and loyal distributors, our brand names are synonymous with Legendary Reliability since 1854. FS-Curtis/Curtis-Toledo, Inc. is proud to be ISO 9001:2008 and ISO 14001:2004 certified.
If you would like more information about this product, please visit www.fscurtis.com or contact Natalie Fontana at 314.383.1300 or email at Info@FSCURTIS.com.

Important Considerations When Installing a Rotary Air Compressor

Let’s say you buy a Volvo, arguably considered one of the safest cars on the road, and you drive it 70mph into a brick wall (by the way, don’t do this, it ruins the paint job), is it the car’s fault that it may no longer run?

The same scenario applies to equipment. If the OEMs installation recommendations are not adhered to, there will be a high degree of probability that the compressed air equipment will not be reliable, will not experience the stated longevity, may require above average maintenance, may consume more electrical energy thanNx_CD_with_tank required and may not consistently provide the compressed air quality required by production.

While it’s impossible to cover all of the things you need to consider when installing a Rotary compressor (and we hope it’s an FS-Curtis), this short article is intended to help avoid the equivalent of driving your car into a brick wall.

Electrical

1) Have your system voltage measured. The most common electrical utility voltages in the United States are 200 volt, 208 volt, 230 volt, 460 volt. Electrical utilities guarantee a voltage supply tolerance of  + 10%.  For example, if the voltage stated supply is 230 volts it could measure at any given time from 207 up to 243 volts. Most electrical utilities attempt to hold the supply voltage to + 5%. Operating electrical motors off design or away from their nameplate voltage will generate additional heat leading to reduced motor life expectancy. The majority of induction motors, 5 hp through 600 hp supplied to the U.S. market, are 230 & 460 volts; however, 200 & 208 volt systems are becoming more popular. If a 230 volt nameplated motor is operated on a 200 to 208 volt system it will operate in an elevated heated condition leading to extremely reduced motor life. This is not a recommended practice. There are motors specifically designed for 200 & 208 volt operation. For these applications motors nameplated as such should be used.

2) Many air compressors operate into the motor service factor. As such, request the package full load operating amp draw from the manufacturer to properly size the electrical utility supply equipment (i.e., wire, electrical quick disconnect, overloads, transformers). Seek out a qualified electrical contractor in your area to assist in proper electrical utility modeling and sizing.

Placement

1) Proper placement and mounting is vital. Request a General Arrangement (GA) drawing from the OEM for each piece of compressed air equipment purchased. The GA drawing should illustrate the weight and recommended clearances to be maintained around the equipment. The floor will need to support the static weight of each piece of equipment. The equipment should be secured to the floor to prevent it from shifting around imparting stress on connected utilities such as piping, electrical and ducting. In addition, many states have adopted seismic codes mandating equipment be structurally secured to the floor. Many floors appear flat to the eye but are not flat enough to meet accepted equipment mounting practices. Many floors can be crowned (bowed) or have undulations. When securing equipment to a floor it is important to identify floor imperfections filling the air gaps with shims. When properly shimmed, the tightening of the mounting bolts will not bend or distort the equipment frame. Frame distortion will lead to excessive equipment vibration. Excessive vibration causes premature component failure which reduces machine reliability, increases cost of ownership and could potentially create an unsafe situation.

Proper clearances should be adhered to. These recommended clearances provide boundary area around the machine for safe, effective operation and servicing of the machine. This boundary area also allows adequate cooling airflow around the machine.

Piping

All piping should be properly supported as to not impart stress on the equipment. When connecting piping to the equipment pipe connector, it should be supported with proper tooling to prevent the equipment connector from turning during the piping tightening process. If the equipment receiving connector is allowed to turn (rotate) it very well could damage internal components to the equipment. Air piping should be properly sized and configured to prevent short cycling of the air compressor controls. A rule of thumb is to always use piping at least the size of the supply connection of the air compressor. If the dryer connections are larger don’t worry, the reason could be the dryer is oversized due to rerating or simply the fittings are larger to slow the compressed air velocity down through the dryer. The piping exiting the dryer can be the same size as the air compressor connection or the outlet piping size of the dryer can be used to establish the piping downstream of the dryer.

Ambient Air

If the ambient air conditions can drop below 32°F measures should be taken to prevent the compressed air equipment from being exposed to this as it will freeze up. During air compressor operation the most effective way to condition the room temperature is to use the heat generated by the operating air compressor(s). Excessive heat can be discharged from the room by way of a properly sized wall fan. The wall fan can be thermostatically controlled to keep the room at a constant temperature. If there are times when all of the compressed air equipment is not operating, an auxiliary heating system should be considered.

Air-cooled rotary screw air compressors reject 2545 btus/hr per horsepower. Example: A 50 horsepower air cooled rotary screw air compressor rejects 127,250 btus/hr into its surrounding environment. That is enough heat to keep a 1500 square foot home comfortable in the dead of winter with outdoor temperatures below 32°F.  Many of these air compressors are installed with little thought of eliminating heat build-up around the air compressor. The heat rejected into the ambient air surrounding the air compressor is continuously cycled through the heat exchangers elevating the temperature. Unchecked, the temperature will rise to an unacceptable level, eventually overheating the air compressor & shutting it down. Ducting can be attached to the air compressor to directly route the cooling air discharge outdoors or away from the air compressor. Wall or ceiling fans can also be strategically placed in the room to exhaust the hot cooling air outside. Either way, an adequate amount of replacement cooling air must be brought into the room.

All installations have contaminants in the ambient air. Contaminants can negatively impact an air compressor in many ways. Two critical ways are indigestion into the air compressor itself with the other being fouling of the air cooled heat exchangers. The best way to determine if the air compressor is digesting an abnormally high amount of contaminants is to consistently perform oil analysis. The oil analysis should look for components not normally part of the oil make-up. The results need to be properly interpreted.

In the case of a lubricated rotary screw air compressor, all of the ambient air drawn into the machine for compression flows right past or through the airend bearings. Too much ingestion of particulate will damage the bearings. The oil not only cools the air during compression it also washes the contaminants out of the air. Over time these contaminants will build up continuing to be cycled through the bearings. For example, a 10 micron particle should be able to flow through an anti friction bearing suspended in the oil film without damaging the bearing surfaces. This does not account for multiple particles clumping together, which will damage the bearing surfaces. Two solutions for reducing digestion of contaminants are to install an air filter with a lower micron rating and higher efficiency rating. The ratings should be adjusted until the oil analysis indicates the level of contaminants is satisfactory. Remember, as the rating of the inlet air filter is increased the surface area should also be increased or the air filter may have to be changed out too frequently from excessive fouling. The second solution is to relocate the inlet air filter to a remote environment which is cleaner than the immediate area around the air compressor. The piping used to remote mount the air filter should be non-ferrous. PVC works great as it is light, easy to assemble and inexpensive. Connect it to the air compressor air end with an easily removable joint in case machine repairs or troubleshooting is required. The piping i.d. should be no smaller than the i.d. opening in the OEM supplied inlet filter mounting assembly. For every 10 feet of inlet pipe run, the pipe diameter should increase one size or 1". If the inlet air filter is relocated outdoors it should be protected from digestion of rain or snow.

Relocation of the inlet air filter is a recommended solution when the surrounding ambient area around the air compressor contains hazardous vapors or fumes. There are air filters which can remove hazardous fumes or vapors; however, they are costly to purchase and maintain.

If you’d like more information about FS-Curtis rotary screw air compressors please follow this link FS-Curtis Rotary Screw Air Compressors. I you have questions or would like more information or pricing, please visit our Distributor Lookup page on our website to locate a distributor in you area.

                          

 

Auto Care Shop Compressors – Don’t Rotate from Recip & Don’t Vary from Fixed Speed

A Variable Speed Drive compressor sounds like a smart idea, but is it really?

Earlier we posted a blog on why rotary machines are often not ideal applications in auto care shops – CLICK HERE TO GO TO THAT POST. Now let’s address another rotary compressor question that auto care facilities ask us on a regular basis: Should I spend the extra money to put an energy-saving VariableCT10_(1) Speed Drive (aka: Variable Frequency Drive) rotary screw compressor in my facility? The short answer to this question is: probably not.

The folks asking this question have heard that VSD/VFD machines may cost more up front but that they cost less to run and thus pay for themselves in the long run. In addition, many utility companies offer rebates for VSD/VFD machines that can help offset the larger up-front cost. Just like everyone else, automotive care facilities want to save money and energy, so this supposed value proposition sounds attractive. Right?

So why then is VSD/VFD probably not a good idea for most automotive care facilities?  The short answer is that most automotive care facilities typically have severe peaks and valleys in their compressed air usage due to the intermittent use of tools and equipment in the shop. This in itself does not rule out VSD/VFD. In fact, VSD/VFD is ideal for customers whose demand fluctuates, provided that it does not fluctuate too much. The problem with auto care facilities is that their valleys are too deep. Too much downtime. The rule of thumb is that when the valleys are 30% or less of the peaks, the compressor will have to shut down, essentially forcing it to run as a start/stop machine. There are several issues with running a VSD/VFD machine in this type of application:

  • More expensive – First of all, the customer is paying a 30% or more premium for a VSD/VFD machine to run just like a cheaper start/stop fixed speed machine. Perhaps the more important comparison is that the customer would be paying a whopping 70% premium compared to a fully-loaded UltraPack recip, which is probably the best application in most auto care shops.
  • Phantom Energy Savings – VSD/VFD machines are ideal for loads somewhere between 30 and 80 percent of full load. There are little to no energy savings otherwise. Even though very short payback periods are often cited, these are for machines in ideal scenarios with exactly the right load profile. Auto care facilities very seldom have an appropriate load profile. If one isn’t going to get the benefit of the VSD/VFD, why pay extra for it, and risk some of the potential headaches outlined below?
  • Increased Maintenance - 

o   VSD/VFD’s require minimal incremental maintenance on the drive compared to standard fixed speed machines. These increased costs should be considered in any decision to go with a variable speed machine.

o   VSD/VFD’s require a cleaner environment for the sensitive electronics of the drive. This can lead to increased maintenance costs and possibly drive replacement, which is very expensive. If the machine is going to be placed in a shop with dust and other contaminants floating in the air, then the cost of protecting the drive from these contaminants, or paying extra for maintenance and/or replacement, must be considered.

The bottom line is that most auto care applications are not ideal for VSD/VFD machines.  The severe valleys in demand profiles mean there probably won’t be energy savings to offset the increased acquisition and maintenance/replacement costs. In addition, most shops are too dirty to install a VSD/VFD without increased risk and cost.

If you would like more information on fixed speed compressor options, click here to compare different options. If you still think a VSD/VFD makes sense, or if you have further questions about our machines (e.g. What is UltraPack? Duplex?) visit our YouTube Library, our distributor portal, our website, or simply call us at 800.925.5431.