An air audit may be in order for your compressor system, especially if it hasn’t been carefully examined recently. While many people focus on the initial cost of purchasing an air compressor, they often forget to factor in the cost of operating the machine over the long run. Any issue within a system can reduce its efficiency, wasting air and electricity, and thereby costing you more money.
But what exactly can an Air Audit do for you? Learn more about how an Air Audit can help you maximize savings. Download "What is an Compressed Air Audit"?
Here are a few guidelines on how to keep your reciprocating air compressor working optimally. No matter what brand of oil-lubricated reciprocating compressor you own, doing the following three things on a regular basis will extend its working life helping to ensure a trustworthy tool for years to come:
- Change lubricant quarterly
- Purge water from tank weekly (at least)
- Change air filter quarterly
Your reciprocating air compressor is basically an engine, and as such it requires constant lubrication to prevent excessive friction from damaging the moving parts and ultimately seizing the piston/s. Non detergent lubricants are typically preferred for reciprocating air compressors, but make sure you respect the viscosity the manufacturer suggests for your particular compressor.
Regularly check the oil level to make sure you have the right amount of oil in the crankcase. While the dangers of too little oil are obvious, it’s also important not to overfill a compressor with oil. If the oil level is too high the oil can get whipped and it will foam up, losing some of its lubricating properties. In addition, it will gain volume, further increasing your problems. So keep checking with your dipstick/gauge as you refill with oil and make sure your unit is perfectly level to the ground when you do this.
These are just as easy to read as the dipstick variety. The red dot represents the “OK” mark (I don’t know why they paint it red, should’ve been green). Ideally you want to keep the oil level within the center of the dot, but as long as the level is within the dot, you are OK.
On these it’s also easier to judge the state of the oil by looking at it with a flashlight, you can often see whether it’s getting milky (water) or darker (regular wear) without having to remove a sample from the crankcase.
Tip #1-Oil is regularly lost through the exhaust and the breather hole on the crankcase. Oil also ages and because of this, you should replace the oil after a certain amount of duty hours. A good rule of thumb that will help you comply with most manufacturer’s requirements is to change your reciprocating compressor oil on a quarterly basis. The actual time depends on many factors and its best if you obtain the manual for your particular compressor for a clear indication on when to replace the oil.
To remove the old oil there’s going to be a bolt at the bottom side or the bottom of the crankcase in all reciprocating air compressors. Simply remove this bolt to allow the old oil to drain into a bucket for proper disposal. To speed up the process, make sure you remove the oil when it’s warm and remove the filling cap so you don’t draw a vacuum.=
Removing Condensate from the Receiver Tank
As the compressor’s intake happens to be ambient air, humidity in the air is sucked in on every cycle. The water vapor from ambient humidity will condense and accumulate in the tank/s. Because of this dynamic, it’s imperative to drain the tank/s at least once a week.
Draining the tank is easy. Locate the drain valve at the bottom of the tank and open it until moisture and air come out of the valve. As soon as the flow of water slows to a trickle, close the valve.
If you don’t drain the tank the condensate will rust the tank’s envelope and ultimately corrosion and rust-through will occur. The more the condensate sits in the tank, the worse it’ll get in time.
To keep condensate from building up in the receiver tank with minimal effort, include the automatic electric timer drain with your purchase of a new compressor. An electric timer drain will open at preset intervals to keep condensate from building up in the tank and finding its way down stream to the shop equipment. Zero-loss drain valves do the same thing, but they lose less compressed air pressure and also reduce the number of short cycles needed to keep the compressed air system at the pre-set level. This saves on your electricity bill.
Tip #2- Because eliminating condensate from the tank is so important to the life of your compressed air system, put a tickler on your calendar to drain the tank at least once a week –more frequently in humid environments. Better yet, automate this task by investing in an automatic tank drain.
Intake Air Filter
The intake air filter is there to stop the compressor from taking in particles of dust in the ambient air which might cause damage to the metal surfaces inside the air compressor. If the location of the compressor has a lot of dust and dirt in the air, this filter may need to be kept clean or changed more often than the manufacturer’s recommendations. Use the manufacturer’s replacement intake air filter for proper fit and filtration.
Tip #3 – Refer to your manufacturer’s recommended intake air filter replacement schedule. Replacement of your intake filter is important to keeping your air compressor in compliance with the manufacturer’s basic and extended warranty. Even if your air compressor is out of warranty,
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.
- 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)
- 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
- 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
- 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
- The motor and compressor run continuously reducing wear
- Tighter range of pressure control (10 PSI)
- Steady progressive capacity control that matches demand
- 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)
- 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
- Makes the control complex
- The Over-run timer must be set to limit premature starting and stopping
- Energy-efficient control scheme that gets down to 50% of capacity
- Matches displacement to demand without reducing inlet pressure or increasing ratios of compression
- Makes the control complex
- High initial cost
- Only available for 50 HP+ compressors
- Energy-efficient and precise control
- Various rotating speeds and giving more displacement and power. These are directly proportional to speed rotation
- Makes the control complex
- High initial cost
- Reduced full load efficiency
- Efficiency of rotary screw compressor ends drop at lower or higher speeds
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:
- Turns the motor which drives the compressor on or off in response to a pressure signal (seen on reciprocating and rotary compressors)
- 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).
- 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).
- 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.
- This controller allows progressive reduction of the compressor displacement without reducing the channel opening (seen on reciprocating and rotary compressors).
- 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
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CA Series compressors aren't just built to handle harsh environments - they're also available in a wide range of configurations to meet your exact application.
Simplex compressors are well suited for common applications where only one compressor is needed.
All of our CA Simplex Compressors include:
- Magnetic motor starter
- Manual tank drain
- Oil sight glass
- Horizontal or vertical tank configurations available
For more information on our complete line of CA Series Air Compressor click here!
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Here’s What You Need to Know
If you’ve been in an auto body shop recently (which is unfortunate because it probably means you’ve had fender bender) or a small manufacturing operation, you may have heard the not-so-inconspicuous hum and rattle of an air compressor. More than likely it was a two-stage compressor. Why not a single-stage? Generally, single-stage units are for less demanding operations like home garages or construction job sites where the distinctive pop, pop, pop sound of nail guns pierce the air like firecrackers on the 4th of July. Nail guns or the occasional use of a rachet gun only require single-stage compressors.
So, why would you need a two-stage air compressor? There are three main reasons:
- Redundancy – If one pump/motor fails or needs service or repair, the other pump/motor can continue to operate, avoiding downtime. Important for any business. Your air flow may be cut in half, but it's better than shutting down your business while the compressor is service.
- Electrical Limitations – What if you absolutely need a 10-15HP compressor but three-phase electrical service is either not available or too expensive run? A duplex compressor with single-phase pump/motors would be your solution.
- Varying Air Usage – If you’re air needs, CFM, fluctuates throughout the work day, where one minute you’re using a small hand tool and the next a sand blaster, a two-stage compressor is perfect to help regulate air flow. When air consumption needs are low, only one pump/motor will operate on your two-stage compressor, but both pumps kick in when demand increases. Smart little boogers, aren't they.
If you’re in the market for a new two-stage compressor, here’s what to look for before you commit.
Definition: One HP is the force needed to lift 550 lbs. one foot in one second.
With all the hubbub made over HP, the CFM (cubic feet per minute) your compressor can generate is actually a more critical factor. But, it’s true that generally speaking, the more HP you have, the more CFM it can produce, so there is a direct correlation that can’t be overlooked. That said, it’s more prudent to shop by CFM, not HP.
CFM (cubic feet per minute)
Every air tool in your shop has a specific CFM requirement—the higher the CFM, the more air volume the tool uses. Keep in mind that if you’re a furniture shop then your sanders will require more air than nail guns.
Take an inventory of CFM requirements for each tool, and the number of everyday tools, and then calculate your necessary CFM, regardless of whether they will all be operating at the same time or not.
Single-phase? Three-phase? What’s the diff?
Generally speaking, single-phase electrical is found in residential settings. Three-phase in commercial buildings, manufacturing operations, etc. So, obviously your first consideration whether to choose a single-phase or three-phase compressor is based on where you will be using it.
Sidenote: Three-phase electricity is considered to be more efficient and therefore could result in less wear and tear on your compressor’s motor.
Keep in mind that electrical codes, voltage and phase vary widely geographically so be sure to check your local building codes and with an electrician before laying out that credit card.
So, now how big of a tank do you need for your compressor? How many gallons?
With two-stage compressors tank sizes range from 60 – 200 gallons. The size of your tank should be basedon how often the compressor will be in use.
This should give you enough to go when choosing your next, or first, two-stage compressor and enough ammunition to ask intelligent questions.
If you should have questions regarding purchasing a two-stage compressor, call our customer service department and we will be happy to assist you: 800-925-5431. Or, visit us online at: us.fscurtis.com
Click on the icons below to download product information about FS-Curtis reciprocating compressors.
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 Variable 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.