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.
When I am working on a project around my home, my wife often starts with a guess as to how many trips to the home improvement or plumbing supply store this project is going to take. (The Gif above is me trying to determine how many choice words will be used.) I try to foil her plans by either already having the first trip done before I start the project, or by buying a surplus of anything and everything I could possibly need on that first trip then returning what I don’t use.
In all actuality, the problem normally comes from working on a house that was built in 1951 and building codes were not the same back then. Whenever it is a new project, say installing a garden fence or building a trampoline platform, I can plan everything out and know all of the variables ahead of time. This results in a single trip to the store per project and more often than not a project that is on budget. That’s why we strive to help our customers here at EXAIR to be prepared for their upcoming projects.
When you are trying to implement a new Super Air Knife into your process, whether it be to cool, clean, or dry a process or product off, we don’t want you to have to go to another vendor, or even have to run back and forth to the tool crib 15 times just to get the knife hooked up to compressed air. To help simplify this, we offer Super Air Knives w/ Plumbing Kit Installed. Whenever a Super Air Knife is 24″ or longer is installed, the compressed air should be supplied to both ends of the knife. When lengths reach 48″ and higher even more ports will need to be plumbed along the length of the knife. This ensures even distribution of compressed air for the full length of the knife. While EXAIR does offer all the information on supplying air to the proper inlets for every given length of Super Air Knife, we also offer to simplify it even further by offering an installed plumbing kit to further simplify installation in the field.
This feature leaves the installation team with minimal points to plumb compressed air once the knife is in your facility. The Aluminum Super Air Knife uses general duty air hose with brass fittings and the 303 and 316 Stainless Steel Super Air Knives use 316SS tube and fittings. An additional pressure gauge is included with longer lengths to install at halfway points in the plumbing kit to verify the operating pressure of the knife.
Even when purchasing the Plumbing Kit Installed option we still offer detailed CAD models as well as PDF and 2D drawings of the knives to make it possible for an installation to be planned out and facilitate an easy, quick, and efficient installation.
If you would like to discuss what Super Air Knife w/ Plumbing Kit Installed would best suit your application, contact us.
There is hardly a day I work that I am not talking about the importance of properly installed pressure gauges. These small devices can often get overlooked or thought of as not necessary on an installation. When troubleshooting or evaluating the compressed air consumption of an application, this is one of the first items I look for in the installation.
As Russ Bowman shows in the above video discussing proper piping sizes, you can see the importance of properly placed pressure gauges. This shows the worst-case scenario where the pressure drop due to improper line sizes gives the false sense to the operator that they are achieving full line pressure when in fact they are not. In order to accurately measure consumption rates, pressure AT THE INLET (within a few feet) to any compressed air product is necessary, rather than upstream at a point where there may be restrictions or pressure drops between the inlet and the gauge. So how exactly do these analog gauges measure the pressure of the compressed air at the installed locations?
The video below shows a great example of pressure increasing and decreasing moving the Bourdon tube that is connected to the indicating needle. The description that follows goes more in-depth with how these internals function.
Most mechanical gauges utilize a Bourdon-tube. The Bourdon-tube was invented in 1849 by a French watchmaker, Eugéne Bourdon. The movable end of the Bourdon-tube is connected via a pivot pin/link to the lever. The lever is an extension of the sector gear and movement of the lever results in rotation of the sector gear. The sector gear meshes with spur gear (not visible) on the indicator needle axle which passes through the gauge face and holds the indicator needle. Lastly, there is a small hairspring in place to put tension on the gear system to eliminate gear lash and hysteresis.
When the pressure inside the Bourdon-tube increases, the Bourdon-tube will straighten. The amount of straightening that occurs is proportional to the pressure inside the tube. As the tube straightens, the movement engages the link, lever, and gear system that results in the indicator needle sweeping across the gauge.
If you would like to discuss pressure gauges, the best locations to install them, or how much compressed air an application is using at a given pressure, give us a call, email, or chat.