Category Archives: Compressor System Design

Point Of Use: Air Receiver Sizing and Placement

Hydraulic Conveyor System

Greetings once again everyone!

The last two installments have been about air receiver sizing within the compressor room.

  1. Compressor Room Layout: Air Receiver Sizing and Placement
  2. Compressor Room Layout: Air Receiver Sizing and Placement, Continued

Today we will address point of use receivers.


Point of Use Receivers

Again, the opinions are many. As always the best advice I can offer is to find a well-educated, consultative professional. Do away with the “salesman” that always has the best price.

In this profession (probably in most) we tend to hear the same concerns and potential solutions over and over. One of those repetitive concerns is: “Occasionally my pressure drops in the main header – so I want to install an air receiver at the far end to combat this issue.”

Although this solution very may well remedy the problem – most often it does not. The solution fails because people don’t take the time to identify the root cause of the problem. This takes time, effort and knowledge of both the system and the physics of compressed air.


Areas to Investigate

  • Design of the header (loop or branch)
  • Pressure drop and velocity in the header system
  • Proper supply volume
  • Point of use applications

 
For this discussion we will zero in on point of use applications that cause the header pressure to be insufficient. These are almost always rather large, intermittent demands. One such application is plasma cutting with a water table. In this application compressed air is used to raise and lower the water level though basically a bladder. Preparing for a cut the water level is raised by filling the bladder with compressed air. Upon completion of the cut, the compressed air is released thus lowering the water level.

2016-05-25-air-release-valve-open.01

Air Release Valve Closed

The filling of the bladder constitutes a large intermittent demand for compressed air. The proper solution comes in two parts. The first is to size a point-of-use receiver to handle 100% of the required volume. The second part is to prolong the re-pressurizing of the receiver as long as possible. Prolonging the re-pressurization results in an overall reduced demand on the compressor system allowing header pressure to remain stable.

I have purposely left out all of the research and formulas to properly size this receiver solution. Not for selfish reasons – just thought a brief blog was not the place to delve into the algebraic equations required.


Other Applications That May Benefit from a Point-of-Use Receiver

  1. sand blasting,
  2. pneumatic product transfer,
  3. sparging,
  4. packaging,
  5. and many more.

Atlantic Compressors is a full-service distributor, offering engineering services, and equipment sales and rentals. Our service department is fully staffed and trained to provide routine and emergency service on most makes and models of air compressor equipment.

Please contact us for a no obligation walk-through of your compressed air system by phone at (540) 728-1147 or by email at bill@atlanticcompressors.com.

Compressor Room Layout: Air Receiver Sizing and Placement, Continued

Hybrid Systems

We left our discussion determining that an air receiver for a load/unload rotary screw compressor system is best sized around 5-gal/cfm. Still staying in the compressor room for now, let’s discuss how many air receivers are necessary and where to locate them.

Once again there is no clear right or wrong way of doing things. Some will recommend a single “wet” receiver and others will insist all receivers be placed on the “dry” side of air treatment. Both scenarios have advantages and disadvantages.

Let’s review each and maybe interject a hybrid solution.


“Wet” Air Receiver

Advantages:

  • Provides excellent moisture separation
  • Allows cooling of compressed air
Disadvantages:

  • Potentially can over flow air treatment
  • Internal corrosion
  • Allows for proper operation of capacity control

“Dry” Air Receiver

Advantages:

  • Air treatment protection
  • Minimal internal corrosion
  • Supply of dry compressed air for large intermittent demands

Disadvantages:

  • Potential slugging air treatment with large quantities of liquids
  • Potential high inlet temperatures to air treatment
  • Pressure drop between tank and compressor capacity system

I am certain there are more than the ones I’ve mentioned.


If you have to choose…

In my opinion, if you only have room and money for one (1) tank,  make it a “wet” tank with a good, reliable zero loss drain.

Another option is the hybrid solution, which uses more than one (1) air receiver.


The Hybrid Solution

This solution is gaining in popularity as knowledge of the efficiency advantages are becoming more commonplace. Installing both a “wet” and “dry” air receiver provides the best solution with only minimal disadvantages. You still size the system for a total of 5-gallons/cfm of the largest cycling rotary screw compressor. But now you split the air receiver sizing so 1/3 of the capacity is on the “wet” side and 2/3 is on the dry side.

The pictures below show a recent installation for one of our customers:

This particular customer already had multiple tanks – so we re-worked the system so they had a single “wet” receiver and three (3) “dry receivers.

Wet tankDry tanks

Every application is different, you need a qualified, experienced professional to review all the parameters of the system and recommend the best solution.


Atlantic Compressors is a full-service distributor, offering engineering services, and equipment sales and rentals. Our service department is fully staffed and trained to provide routine and emergency service on most makes and models of air compressor equipment.

Please contact us for a no obligation walk-through of your compressed air system by phone at (540) 728-1147 or by email at bill@atlanticcompressors.com.
 

Compressor Room Layout: Air Receiver Sizing and Placement

Air Receiver Sizing and Placement for Compressed Air Systems

Hello again. I hope everyone had a great Thanksgiving. I can’t believe November got past me by with just a single blog post!

Today we’ll discuss the debate surrounding the sizing and placement of the air receiver in the compressed air room layout.


The Debate

To begin our discussion, I’d like to suggest that there aren’t many absolutes in the compressed air industry. Now don’t get me wrong, there are correct and efficient ways to do things; however, there is often more than one way to accomplish the same thing. For example, there are many differing opinions about air receiver size and where one should be positioned within a compressor system. In fact, no topic in this industry has caused more debate!

To better understand the reason for the diversity in opinions, I’d like to provide a little history. When rotary screw compressors emerged onto the stationary application, the capacity control system used at the time was inlet modulation. While this type of control system doesn’t need a large air receiver to produce good results, the control system itself can be quite an energy hog! As the inherit energy inefficiency of compressors became widespread knowledge, more efficient control systems were developed like dual control (load/unload) controls, and eventually variable speed drive (VSD).


Dual (Load/UnLoad) Controls

For this post, we’ll focus primarily on dual control (load/unload) controls. Modulating compressor manufacturers would typically recommend a tank sized for one gallon for every cfm the compressor produced (i.e.120 cfm = 120 gallon tank); dual control (load/unload) control manufacturers might recommend two to three gallons for every cfm produced. The additional tank size of course raised the purchase price and often a poorly-trained sales force would just “take the order” for an improperly sized tank. So while the system might work, no real energy savings were realized. (Note: The energy savings were also minimal with even two to three gallons/cfm.)

Air System AuditorToday, we have the benefit of years of energy awareness and concentrated studies on the efficiency of compressed air systems. Thanks to organizations like Compressed Air Challenge™, CAGI™, the U.S. Department of Energy, as well as the many independent auditors across the country, we know the real benefits of proper tank sizing.

I could go on for a few more pages, but I’ll stop here. Next time, I’ll talk about where to put these tank(s), and whether we should have more than one.


Tank Size & the Law of Diminishing Returns

The graph below (courtesy of plantservices.com) represents the kW savings from tank sizes based on gallons/cfm, for a dual control (load/unload) compressor. Although one can debate that bigger is always better (and it often is), the law of diminishing returns is also a factor.

Kilowatt Savings from Tank Sizes Based on Gallons/CFM


So what’s the bottom line?

The best deal for your money is around five gallons/cfm.


Atlantic Compressors is a full-service distributor, offering engineering services, and equipment sales and rentals. Our service department is fully staffed and trained to provide routine and emergency service on most makes and models of air compressor equipment.

Please contact us for a no obligation walk-through of your compressed air system by phone at (540) 728-1147 or by email at bill@atlanticcompressors.com.
 

Compressor Room Layout, Continued: The Effect of Temperature

Temperature Changes & Air Compressors

It’s now officially fall — the landscape is changing color, kids are gearing up for various festivities, and temperatures are getting cooler. As the great poet Bob Dillon once said “The Times They Are A-Changin’.” So how do cooler temperatures affect the location of your compressor?

Climate & Your Compressor Room Location

The climate here in Virginia is pretty moderate – it never gets really cold or hot. In this area (or areas similar to it) one might think that installing a compressor system outdoors would have some advantages. After all, the cost of square footage inside a facility comes at a premium compared to the cost of a concrete slab and a lean-to roof on the outside of a building. And depending on the type of business, if located inside, the compressor system could be very noisy and produce unwanted heat loads.

You would never consider placing an air compressor outside in northern climates where temperatures can easily drop below freezing and stay that way all winter. Nor would you install one outside in many southwestern states where summer temperatures consistently exceed 100 degrees. The reason for this is that oil lubricated rotary screw compressors (the most common type of industrial air compressor) simply won’t survive these extreme conditions.


What About Virginia?

Where temperatures get below freezing, air compressor rooms should be located indoors.Here in Virginia however, where winter temperatures consistently fall below freezing in the evening, the correct choice would still be to locate a compressor system indoors. In addition, most rotary screw compressor manufacturers now equip their compressor controllers with a low temperature inhibit feature. This feature prevents the compressor from starting if the oil temperature is below 38 degrees (on average). Another reason to locate the compressor indoors is to prevent condensate from freezing.

Now that we’ve settled the debate about where to locate a compressor system (rotary screw compressors installed in this area belong indoors). We also need to address the issues of noise, service access, and heat discharge from rotary screw compressors.


In my next post, we’ll continue this discussion along with other topics related to the layout and design of a compressor room.

Atlantic Compressors is a full-service distributor, offering engineering services, and equipment sales and rentals. Our service department is fully staffed and trained to provide routine and emergency service on most makes and models of air compressor equipment.

Please contact us for a no obligation walk-through of your compressed air system by phone at (540) 728-1147 or by email at bill@atlanticcompressors.com.
 

Designing a Compressor Room for Rotary Screw Air Compressors

Compressor Room Design for Rotary Screw Air Compressors

As I write this post, my family and I are I the midst of a major home renovation project. If you’ve ever been involved in a similar project, you can appreciate how over time it can become a learning and growing experience. Now that the renovation is close to completion, I realize there are some things I would have done differently.

The purpose of today’s post is to establish a few guidelines for designing a compressor room for rotary screw air compressors. In this post, I review the importance of:

 
By no means should this be your only or last reference, but consider it a great starting point for items that are often overlooked when designing a compressor room.


Location

As they say in real estate: it’s all about location, location, location. A compressor room is not much different.

First off, electrical wire and conduit are more expensive to install than compressed air piping. If given the option, always locate the compressor room close to the electrical source.


Free, Warm Air!

Next, air-cooled compressors discharge warm, clean and free air from their air/oil coolers. This heat source can be used for space heating, pre-heating water for boiler or hot water heaters, and other various applications. With this in mind, consider locating the compressor room where an application can benefit from this free heat source. Doing so and you could reap a large payback and help justify your project. Also, same goes for water-cooled compressors – the warm discharge water can be used for multiple purposes.


Routing Condensate

Compressor Room Layout - Condensate Drains
Click here to learn about condensate drain options

Probably the most overlooked item in a compressor is a floor drain. In my experience this is the most forgotten item when a compressor is designed. Air compressors produce large amounts of condensate that needs to be properly treated and disposed. Due to the potential oil carry-over from a lubricated rotary screw compressor, the condensate is listed as a hazardous material by the EPA. Therefore, the condensate must be handled and disposed of properly. The most economical way is to route the condensate through an oil/water separator first. This product will separate and collect the oil and the condensate discharge is 15-20ppm, which is suitable for most localities sanitary sewer system.

In my next blog post we’ll discuss more topics related to the layout and design of a compressor room.


Atlantic Compressors is a full-service distributor, offering engineering services, equipment sales and rentals. Our service department is fully staffed and trained to provide routine and emergency service on most makes and models of air compressor equipment.

Please contact us for a no obligation walk-through of your compressed air system. Call (540) 728-1147 or email bill@atlanticcompressors.com.