The 5th step in the 6 steps to optimizing your compressed air system highlights the use of intermediate storage of compressed air near the point of use. Secondary, or intermediate Receiver tanks are installed in the distribution system to provide a source of compressed air close to the point of use, rather than relying on the output of the compressor.
Compressed air receiver tanks are an integral part to many compressed air distribution systems. Compressed air is stored at a high pressure after drying and filtration, but just upstream of point of use devices. The receiver tank is charged to a pressure higher than what is needed by the system, creating a favorable pressure differential to release compressed air when needed.
Think of a compressed air receiver tank as a “battery”. It stores the compressed air energy within a system to be used in periods of peak demand, helping to maintain a stable compressed air pressure. This improves the overall performance of the compressed air system and helps to prevent pressure drop.
They can be strategically placed to provide a source of compressed air to intermittent high volume compressed air applications. Rather than having to pull from the compressor, a receiver tank can be sized to provide the short-term volume of air for a particular application. In a previous post, we’ve highlighted how to calculate the necessary receiver tank based on the air consumption and duration of the application.
EXAIR offers from stock a 60-gallon receiver tank designed specifically for these higher-usage intermittent types of applications. Model 9500-60 can be installed near the point of high demand so that you have an additional supply of compressed air available for a short duration. The tank comes with mounting feet and is designed to stand up vertically, saving floor space. The tank meets American Society of Mechanical Engineers (ASME) pressure vessel code.
Just this past Spring, EXAIR hosted a live webinar where we discuss how to size, install, and implement secondary storage in your plant’s distribution system. If you missed it, check it out here on our website hosted by my colleague, Russ Bowman.
If you have an application in your facility that’s draining your compressed air system, a receiver tank could be the ideal solution. Give us a call and one of our Application Engineers will be happy to help evaluate your process and determine the most suitably sized receiver tank.
In any manufacturing environment, compressed air is critical to the operation of many processes. You will often hear compressed air referred to as a “4th utility” in a manufacturing environment. The makeup of a compressed air system is usually divided into two primary parts: the supply side and the demand side. The supply side consists of components before and including the pressure/flow controller. The demand side then consists of all the components after the pressure/flow controller.
The first primary component in the system is the air compressor itself. There are two main categories of air compressors: positive-displacement and dynamic. In a positive-displacement type, a given quantity of air is trapped in a compression chamber. The volume of which it occupies is mechanically reduced (squished), causing a corresponding rise in pressure. In a dynamic compressor, velocity energy is imparted to continuously flowing air by a means of impellers rotating at a very high speed. The velocity energy is then converted into pressure energy.
Still on the supply side, but installed after the compressor, are after coolers, and compressed air dryers. An after cooler is designed to cool the air down upon exiting from the compressor. During the compression, heat is generated that carries into the air supply. An after cooler uses a fan to blow ambient air across coils to lower the compressed air temperature.
When air leaves the after cooler, it is typically saturated since atmospheric air contains moisture. In higher temperatures, the air is capable of holding even more moisture. When this air is then cooled, it can no longer contain all of that moisture and is lost as condensation. The temperature at which the moisture can no longer be held is referred to as the dewpoint. Dryers are installed in the system to remove unwanted moisture from the air supply. Types of dryers available include: refrigerant dryers, desiccant dryers, and membrane dryers.
Also downstream of the compressor are filters used to remove particulate, condensate, and lubricant. Desiccant and deliquescent-type dryers require a pre-filter to protect the drying media from contamination that can quickly render it useless. A refrigerant-type dryer may not require a filter before/after, but any processes or components downstream can be impacted by contaminants in the compressed air system.
Moving on to the demand side, we have the distribution system made up of a network of compressed air piping, receiver tanks when necessary, and point of use filters/regulators. Compressed air piping is commonly available as schedule 40 steel pipe, copper pipe, and aluminum pipe. Some composite plastics are available as well, however PVC should NEVER be used for compressed air as some lubricants present in the air can act as a solvent and degrade the pipe over time.
Receiver tanks are installed in the distribution system to provide a source of compressed air close to the point of use, rather than relying on the output of the compressor. The receiver tank acts as a “battery” for the system, storing compressed air energy to be used in periods of peak demand. This helps to maintain a stable compressed air pressure. It improves the overall performance of the system and helps to prevent pressure drop.
Finally, we move on to the point-of-use. While particulate and oil removal filters may be installed at the compressor output, it is still often required to install secondary filtration immediately at the point-of-use to remove any residual debris, particulate, and oil. Receiver tanks and old piping are both notorious for delivering contaminants downstream, after the initial filters.
Regulator and filter
In any application necessitating the use of compressed air, pressure should be controlled to minimize the air consumption at the point of use. Pressure regulators are available to control the air pressure within the system and throttle the appropriate supply of air to any pneumatic device. While one advantage of a pressure regulator is certainly maintaining consistent pressure to your compressed air devices, using them to minimize your pressure can result in dramatic savings to your costs of compressed air. As pressure and flow are directly related, lowering the pressure supplied results in less compressed air usage.
EXAIR manufactures a wide variety of products utilizing this compressed air to help you with your process problems. If you’d like to discuss your compressed air system, or have an application that necessitates an Intelligent Compressed Air Product, give us a call.
To fully appreciate how impactful a properly functioning air compressor system is to your bottom line, it is foremost important to fully understand how much your compressed air costs. Compressed air is a self generated utility within your facility that is a top 3-4 utility expense for your company. This fact is often overlooked or misunderstood, because the expense is primarily linked to the electric and or gas bill. This can be a costly oversite. You will see an example below where a single common maintenance issue causes a 4psi reduction in performance and resulted in $1265 in additional annual cost to that company. Imagine when/if there are multiple issues…
In order to calculate the compressed air cost, some companies use an educated guess of @$0.25 per 1000 cubic feet of compressed air consumed, and others are more precise. The U.S. department of Energy performed an energy saving study in 2004 and they show a precise way to calculate your compressed air cost. Here is their sample calculation:
“Compressed air is one of the most expensive sources of energy in a plant. The overall efficiency of a typical compressed air system can be as low as 10%-15%. For example, to operate a 1-horsepower (hp) air motor at 100 pounds per square inch gauge (psig), approximately 7-8 hp of electrical power is supplied to the air compressor. To calculate the cost of compressed air in your facility, use the formula shown below:
Cost ($) = (bhp) x (0.746) x (# of operating hours) x ($/kWh) x (% time) x (% full-load bhp) ÷ Motor Efficiency Where: bhp = Motor full-load horsepower (frequently higher than the motor nameplate horsepower—check equipment specification) 0.746 = conversion between hp and kW Percent time = percentage of time running at this operating level Percent full-load bhp = bhp as percentage of full-load bhp at this operating level Motor efficiency = motor efficiency at this operating level Example: A typical manufacturing facility has a 200-hp compressor (which requires 215 bhp) that operates for 6800 hours annually. It is fully loaded 85% of the time (motor efficiency = .95) and unloaded the rest of the time (25% full-load bhp and motor efficiency = .90). The aggregate electric rate is 0.05/kWh. Cost when fully loaded = (215 bhp) x (0.746) x (6800 hrs) x ($0.05/kWh) x (0.85) x (1.0) = $48,792 .95 Cost when unloaded = (215 bhp) x (0.746) x (6800 hrs) x ($0.05/kWh) x (0.15) x (0.25) = $2,272 .90 Annual energy cost = $48,792 + $2,272 = $51,064″
I encourage you to calculate this self generated utility cost for your facility. Also keep in mind that this example is using $0.05/kWh, this example was form 2004, today the average industrial sector cost in the US is $0.0747 (see more here). This annual cost puts so many things into perspective. First and foremost the importance of Maintenance. Even more specific, the preventative maintenance costs become much lower than the impact of even one small oversite. Here is an example from the Department of Energy that discusses a specific and common maintenance issue and it’s annual impact.
“A compressed air system that is served by a 100-horsepower (hp) compressor operating continuously at a cost of $0.08/kWh has annual energy costs of $63,232. With a dirty coalescing filter (not changed at regular intervals), the pressure drop across the filter could increase to as much as 6 psi, vs. 2 psi when clean. The pressure drop of 4 psi accounts for 2% of the system’s annual compressed air energy costs. (or an increase of $1,265 per year)”
The realization of the dollars spent for compressed air certainly pushes the priority of maintenance. If we extrapolate from the above filter example, we can see that a 4 psi pressure drop in that system increased the cost by $1265 per year. We need to then ask ourselves, what other areas could be causing a pressure drop or stressing the motor? And if there is an issue upstream to this issue, will it cause even more issues, or more pressure drops?
There are many tips, tools, websites, YouTube videos and more, out there that address the recommended maintenance of your compressor and system. Many of you already have specific guidelines for your precise system, and set maintenance schedules in place. Below is a sample checklist (not all-inclusive) of maintenance items to watch for with your compressor in case you need a starting point. If left unchecked and or uncorrected, any of these (if an issue) will cost your company money – over time, lots of money.
I would be amiss if I finished this blog without mentioning the perils of pressure leaks. The Compressed Air and Gas Institute stated that a single 1/4″ leak, can cost you between $2500 and $8000 per year (CAGI article). Imagine the impact of several leaks!!!
How do I find leaks? I’m glad you asked. The first step is to walk your lines and check any or all of the following areas for leaks or damage.
A great way to identify leaks is to use our Ultrasonic Leak Detector to listen for leaks. Look for and ask the technicians if there seems to be a change in productivity. Install Pressure Regulators and gauges at each point of use in your facility – monitor and log these pressures often. Once you find an issue, no matter how small, correct it. A small leak adds up $$$ over the hours, weeks, and months.
In addition to leaks, there are many times that air is wasted by being blown on empty space (i.e. the space between items on your conveyor). you, please look at our Electronic Flow Control (EFC) product, this device gives you an out of the box automation solution that can be set up in minutes and save thousands. There are so many clogged and leaking pipes, bad hoses inside many plants, this coupled with using an poor performing Air Gun, or Air Nozzle all have large dollar impacts for your company. EXAIR has products that can help in all of these areas…
In parting, please keep in mind that many Utility companies offer incentives to companies that take an initiative to reduce their energy footprint. In our current time of inflation this is a real way to reduce costs, many times significantly. We are here to help. Please contact us for assistance in dramatically reducing both your utility costs, and your environmental impact.
One thing that is found in virtually every industrial environment is an air compressor. Some uses for the compressed air generated are: powering pneumatic tools, packaging, automation equipment, conveyors, controls systems, and various others. Pneumatic tools are favored because they tend to be smaller and more lightweight than electric tools, offer infinitely variable speed and torque, and can be safer than the hazards associated with electrical devices. In order to power these devices, compressed air must be generated.
There are two main categories of air compressors: positive-displacement and dynamic. In a positive-displacement type, a given quantity of air is trapped in a compression chamber. The volume of which it occupies is mechanically reduced (squished), causing a corresponding rise in pressure. Of the positive-displacement variety they are broken down further into two more categories: reciprocating and rotary.
A reciprocating compressor works like a bicycle pump. A piston reduces the volume occupied by the air or gas, compressing it into a higher pressure. There are two types of reciprocating compressors, single or double-acting. Single-acting compressors are the most common and are available up to 30HP at 200 psig.
Their small size and weight allow them to be installed near the point of use and avoid lengthy piping runs. Additionally, the single-acting reciprocating compressors do not need a separate cooling system. All of this leads to much simpler maintenance procedures, making the single-acting reciprocating compressors one of the easiest to maintain.
There are some disadvantages to this style of compressor. Rings have a tendency to wear out over time, if they’re not replaced as needed this can lead to lubricant carry-over into the air supply. These styles of compressor are relatively loud and comparatively cost more to operate than many other types. Because of this, they’re not designed for applications and processes that have a heavy-duty cycle of 70-90%. The single-acting reciprocating compressor should be used in installations where it’s only going to run 50% or less of the time.
At EXAIR we’re committed to providing you with the point of use products that’ll use your compressed air as efficiently and safely as possible. Feel free to reach out to an Application Engineer to discuss how we can help you improve in your processes.
