Don’t Fall Victim To Undersized Piping

Pressure drops, incorrect plumbing, undersized piping, insufficient flow; if you hear these terms from tech support of your point of use compressed air products or from your maintenance staff when explaining why a process isn’t working then you may be a victim of improper compressed air piping selection.
Often time this is due to a continued expansion of an existing system that was designed around a decade old plan. It could also come from a simple misunderstanding of what size of piping is needed and so to save some costs, smaller was used. Nonetheless, if you can understand a small number of variables and what your system is going to be used for, you can ensure the correct piping is used. The variables that you will want to consider when selecting a piping size that will suit your need and give the ability to expand if needed are shown below.

  • Minimum Operating Pressure Allowed (psig) – Lowest pressure permitted by any demand side point of use product.
  • System Pressure (psig) – Safe operating pressure that will account for pressure drops.
  • Flow Rate (SCFM) of demand side (products needing the supplied compressed air)
  • Total Length of Piping System (feet)
  • Piping Cost ($)
  • Installation Cost ($)
  • Operational Hours ( hr.)
  • Electical Costs ($/kwh)
  • Project Life (years) – Is there a planned expansion?

An equation can be used to calculate the diameter of pipe required for a known flow rate and allowable pressure drop. The equation is shown below.

A = (144 x Q x Pa) / (V x 60 x (Pd + Pa)
Where:
A = Cross-Sectional are of the pipe bore. (sq. in.).
Q = Flow rate (cubic ft. / min of free air)
Pa = Prevailing atmospheric absolute pressure (psia)
Pd  = Compressor discharge gauge pressure (psig)
V = Design pipe velocity ( ft/sec)

If all of these variables are not known, there are also reference charts which will eliminate the variables needed to total flow rate required for the system, as well as the total length of the piping. The chart shown below was taken from EXAIR’s Knowledge Base.

Once the piping size is selected to meet the needs of the system the future potential of expansion should be taken into account and anticipated for. If no expansion is planned, simply take your length of pipe and start looking at your cost per foot and installation costs. If expansions are planned and known, consider supplying the equipment now and accounting for it if the additional capital expenditure is acceptable at this point.

The benefits to having properly sized compressed air lines for the entire facility and for the long-term expansion goals makes life easier. When production is increased, or when new machinery is added there is not a need to re-engineer the entire system in order to get enough capacity to that last machine. If the main compressed air system is undersized then optimal performance for the facility will never be achieved. By not taking the above variables into consideration or just using what is cheapest is simply setting the system up for failure and inefficiencies. All of these considerations lead to an optimized compressed air system which leads to a sustainable utility.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

Six Sigma and The Compressor Room

Throughout my undergrad courses as well as during my professional career I have encountered Six Sigma or Lean Manufacturing in many facilities.  There is at least one component to the theory that can be implemented into any facility with a compressor room. That component is the practice of the 5 S’s.

The 5 S’s of Lean Manufacturing come from the Japanese terms  listed below with their English translations:

Seiri – Sort (Organize)
Seiton – Set in Order (Orderliness)
Seiso – Shine (Cleanliness)
Seiketsu – 
Standardize
Shitsuke –  Sustain (Discipline)

These 5 points can aid in keeping any air compressor room in a facility efficient, safe, and effectively supplying the company with compressed air. How you may ask.

Sort – Keeping a compressor room as originally laid out and preventing it from being a catch-all for items that have nothing to do with the compressed air system. This can easily happen when it is actually a room that has unused floor space in a small facility. By keeping the area clean and free of unrelated materials, maintenance and troubleshooting can be done quickly. Clear labeling of anything kept in the room is also ideal to make items easily identified.

Set in Order – To deliver the air in a single path/direction as well as keeping equipment in locations where they can be easy to maintain and clearly labeled eases the troubleshooting and understanding of how the system is laid out. Rather than having a spaghetti bowl of piping running all around the room to different components it is wiser to keep a flow that matches the process. From the compressor(s) to the receivers, dryers, filter, and regulators, out to the point of use. This shouldn’t be a tangled web of piping that introduces air to a process which bypasses key components such as the dryer or receivers.

Block diagram of a compressor room layout.

Shine – The compressor room shouldn’t be a dirty grungy area. The compressor pulls the air in from this environment. Any exposed components easily collect airborne debris. By keeping the equipment clean again makes labels easy to read and a clean machine is always easier to perform maintenance and sometimes even troubleshoot. If there are puddles of oil or other liquids on the floor and no surfaces are clean then any leak may not be easily spotted.

Standardize – The layout and processes used within the room should be repeatable. Maintenance tasks should be performed on a schedule, per a process that doesn’t allow for much differentiation on methods and end results. This mitigates errors and is always the desired result when focusing on lean manufacturing. LOWER THAT DELTA!

Sustain – This is sometimes the hardest part of any process. Getting the program up and running, starting with a fresh build is always the easiest.  Everything is fresh, new and you want to keep it shiny. Years later the desire to dust and maintain piping as well as keep receiver tanks and floors clean isn’t always at the top of the desired list.  It should always be a priority because cleanliness also promotes safety and reduces overhead by lowering downturns due to housekeeping related failures.

If you want to discuss how we can help lean out your compressed air usage, maintenance costs, and help to standardize the use of compressed air in your facility, contact an Application Engineer today.

Brian Farno
Application Engineer – Green Belt Certified
BrianFarno@EXAIR.com
@EXAIR_BF

Proper Plumbing Prevents Poor Performance

There’s nothing quite like an ice-cold Coke from McDonald’s. While there’s many reasons for this, one of the reasons for the unique experience of a McDonald’s Coke lies in the straw itself. In their drinks, they provide wider straws that are designed to help enhance the taste of Coca-Cola, or so they claim. Another impact of this is it allows you to drink significantly faster. The wider the opening for liquid to pass through, the more volume you’re able to drink. Imagine trying to drink your Coke, or any other beverage, through a coffee stirrer. I imagine you’re going to have a difficult time and a dry mouth as you try and force what little amount of liquid you can through the small I.D. of a coffee stirrer. Try that with a milkshake and the problems compound…..

The same is true when it comes to plumbing of your point-of-use compressed air products. I recently assisted a customer that was experiencing lackluster performance from the Super Air Knife they purchased. The application was fairly straightforward, they were hoping to reduce the rate of rejected material on their production line of plastic sheets. The sheet goes through a washing process to remove any residual contaminants, then would air dry as it made its way down the line. As the material dried, there were water spots left on the material that would have to then be cleaned off. In the hopes of speeding up the drying process, they purchased a Model 110060 60” Super Air Knife to provide a wide laminar sheet of air to dry the material.

WhatsApp Image 2018-12-13 at 15.49.45 (2)

When they hooked everything up, the flow from the knife seemed far less than they were expecting. They were supplying full line pressure (just over 90 PSIG), so in theory they should feel a strong blast of air from the knife. When they installed a pipe tee and pressure gauge directly at the inlet, they noticed the pressure was dropping to 35 PSIG while the knife was in operation. When this occurs, it’s indicative of a lack of volume of air. This can be caused by undersized compressor,  or improper plumbing. In their case, they were only plumbing compressed air to one center inlet of the knife. For a 60” knife, EXAIR recommends a minimum of (4) air inlets to ensure adequate volume.

SAK plumbingh

The size of these lines is also critical. You can’t force greater volumes of air through a smaller hose or pipe, just like you can hardly drink through a coffee stirrer with any great success. A 60” knife requires a supply pipe size of 1-1/2” for up to a 50’ run, if you’re trying to supply a knife of this length with a 100’long, ¼” ID hose, you’re not going to get the performance you expect. If you’re experiencing less than optimal performance from any of your EXAIR Intelligent Compressed Air Products, there’s a good chance air supply is the culprit. The first step is determining what the actual inlet pressure is, install a pipe tee and pressure gauge right at the inlet. Then, give us a call and we’ll help work through the proper line sizes and ensure that you’re getting the most out of our products.

I hope I didn’t make you hungry or thirsty… But I think I know where and what I’m having for lunch 😊!

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@EXAIR.com
Twitter: @EXAIR_TD

How to Calculate and Avoid Compressed Air Pressure Drop in Systems

EXAIR has been manufacturing Intelligent Compressed Air Products since 1983.  They are engineered with the highest of quality, efficiency, safety, and effectiveness in mind.  Since compressed air is the source for operation, the limitations can be defined by its supply.  With EXAIR products and pneumatic equipment, you will need a way to transfer the compressed air from the air compressor.  There are three main ways; pipes, hoses and tubes.  In this blog, I will compare the difference between compressed air hoses and compressed air tubes.

The basic difference between a compressed air hose and a compressed air tube is the way the diameter is defined.    A hose is measured by the inner diameter while a tube is measured by the outer diameter.  As an example, a 3/8” compressed air hose has an inner diameter of 3/8”.  While a 3/8” compressed air tube has an outer diameter that measures 3/8”.  Thus, for the same dimensional reference, the inner diameter for the tube will be smaller than the hose.

Why do I bring this up?  Pressure drop…  Pressure Drop is a waste of energy, and it reduces the ability of your compressed air system to do work.  To reduce waste, we need to reduce pressure drop.  If we look at the equation for pressure drop, DP, we can find the factors that play an important role.  Equation 1 shows a reference equation for pressure drop.

Equation 1:

DP = Sx * f * Q1.85 * L / (ID5 * P)

DP – Pressure Drop

Sx – Scalar value

f – friction factor

Q – Flow at standard conditions

L – Length of pipe

ID – Inside Diameter

P – Absolute Pressure

 

From Equation 1, differential pressure is controlled by the friction of the wall surface, the flow of compressed air, the length of the pipe, the diameter of the pipe, and the inlet pressure.  As you can see, the pressure drop, DP, is inversely affected by the inner diameter to the fifth power.  So, if the inner diameter of the pipe is twice as small, the pressure drop will increase by 25, or 32 times.

Let’s revisit the 3/8” hose and 3/8” tube.  The 3/8” hose has an inner diameter of 0.375”, and the 3/8” tube has an inner diameter of 0.25”.  In keeping the same variables except for the diameter, we can make a pressure drop comparison.  In Equation 2, I will use DPt and DPh for the pressure drop within the tube and hose respectively.

Equation 2:

DPt / DPh = (Dh)5 / (Dt)5

DPt – Pressure drop of tube

DPh – Pressure Drop of hose

Dh – Inner Diameter of hose

Dt – Inner Diameter of tube

Thus, DPt / DPh = (0.375”)5 / (0.25”)5 = 7.6

As you can see, by using a 3/8” tube in the process instead of the 3/8” hose, the pressure drop will be 7.6 times higher.

Diameters: 3/8″ Pipe vs. 3/8″ tube

At EXAIR, we want to make sure that our customers are able to get the most from our products.  To do this, we need to properly size the compressed air lines.  Within our installation sheets for our Super Air Knives, we recommend the infeed pipe sizes for each air knife at different lengths.

There is also an excerpt about replacing schedule 40 pipe with a compressed air hose.  We state; “If compressed air hose is used, always go one size larger than the recommended pipe size due to the smaller I.D. of hose”.  Here is the reason.  The 1/4” NPT Schedule 40 pipe has an inner diameter of 0.364” (9.2mm).  Since the 3/8” compressed air hose has an inner diameter of 0.375” (9.5mm), the diameter will not create any additional pressure drop.  Some industrial facilities like to use compressed air tubing instead of hoses.  This is fine as long as the inner diameters match appropriately with the recommended pipe in the installation sheets.  Then you can reduce any waste from pressure drop and get the most from the EXAIR products.

With the diameter being such a significant role in creating pressure drop, it is very important to understand the type of connections to your pneumatic devices; i.e. hoses, pipes, or tubes.  In most cases, this is the reason for pneumatic products to underperform, as well as wasting energy within your compressed air system.  If you would like to discuss further the ways to save energy and reduce pressure drop, an Application Engineer at EXAIR will be happy to assist you.

 

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb