It is a typical call to receive from customers looking to replace an inefficient, commercial grade or homemade compressed air product. Nearly always, customers can save dollars by using their compressed air more efficiently through an engineered product like ours. The performance characteristics of EXAIR products are presented at a pressure and air consumption capable of solving most industrial applications, but these performance numbers can be increased or decreased in a couple of ways. One way is by adjusting the inlet air pressure. The force, flow and volume will increase or decrease with increased or decreased pressure. Secondly, some products like Super Air Wipes, Super Air Knives and Super Air Amplifiers have an internal shim which can be changed to increase or decrease the precision air gap of the product. Applications like the following benefit from changing the shim in these products:
I worked with a customer who was using our 9″ aluminum Super Air Knife to dry a ceramic block with several individual cells. The unit was working great and they were looking to add another machine to their production line but since the Super Air Knife came with the wash coating machine, they were unsure how much air they were using and were concerned the demand on their compressor might be too great. As mentioned above, one way to reduce the air consumption would be to use a pressure regulator to adjust the supply pressure as well as control the output flow and velocity. Another simple way to control the airflow would be to change the shim to a different thickness. (for reference, here’s a video blog showing how to change the shim on a Super Air Knife)
The Super Air Knife is shipped from stock with a .002″ shim installed which is red in color. I asked if they knew what shim was in the knife and they didn’t have the thickness but knew it was green not red. That was all the info we needed, the green shim is .003″ thick and certainly overkill for removing a water based liquid from most surfaces. The performance spec chart below references the air consumption per inch with the .002″ shim installed. With the .003″ shim installed, these values would increase by 1.5 times.
Chart showing air consumption (per inch) at various supply pressures.
I recommended the customer order the .002″ shim, which the OEM had removed and replaced with a larger shim. This would cut the current air consumption rate from 39 SCFM at 80 PSIG to 26 SCFM at 80 PSIG. That was what it took to get the application solved and to increase production with a new machine.
Just last week I received a package on my front porch. This was a replacement part for a tool which I purchased used, knowing it needed the part. The trick is, I needed it a few months ago. I ordered the part from the manufacturer directly on July 2, 2015. This part was said to be in stock and would ship to my home from their location which was also in the United States. I heard good things about the company and I bought the tool with confidence I could have the part and the tool fixed quickly. I thought, no big deal I will get it within a week, fix it, and then use it.
After not receiving a shipping notification and nothing showing up at my door for two weeks I decided to call the company. I finally got hold of a customer service representative after I had to wade through the automated phone attendant. The person explained that they had in fact received my order and they would try to ship it out the next day so watch my email. Well, the next day came and when it was nearing the end of the day I decided to call in again since I had still yet to receive a shipping confirmation. This time I got in touch with a different customer service rep who explained there had been a fire in their warehouse and that nothing was shipping that day or even that week. The fire didn’t happen that day, it had happened over 2 weeks prior to that. Instead of notifying me when I placed my order, or even when I called in the first time I was simply told incorrect information. I gave them the benefit of the doubt and after discussing the issue the customer rep. told me they are doing their best to get items lined up and out as quickly as they can. It should only be a few more weeks.
I accepted the explanation and began the waiting period. a few weeks came and I received a back-order notification in the mail, still no notification of any sort stating they are not shipping any products out. Few more weeks and another post card. After the third post card I had almost forgotten about it. Finally I received an e mail, my item had shipped. Two days later it was on my porch and packed like any other shipment. No explanation for the delay, no apologies, and as if it was just normal business for them.
I ordered the part on July 2nd, I received the part on October 13th. Needless to say, the quality is good but the customer service communication is fairly lacking.
I began to think about what we do at EXAIR, and came to the realization that if something like this had happened here we would have sent out an E-News, a simple e-mail, tell customers who call in, and other forms of communication to every last customer that had an order in and we would be notifying every customer that was placing new orders. We would be up front with the information and we would not hesitate to apologize for the inconvenience. We have had disruptive incidents in the past which we handled this way, this is just good business etiquette. This goes hand in hand with the fact you speak to a human when you call in to our office, all stock products (and we stock it ALL) ship same day on orders received by 3 PM ET when shipping in the US, and we will give you updates via e-mail or phone however you prefer. Then to top it all off, we will give you a 30 day guarantee and a 5 year built to last warranty on pneumatic parts.
30 Day Guarantee
So if you want to be informed, treated right, get the products you need in a timely manner, and get your problem solved, you have zero reason to go with anyone else.
I had an application where a customer needed to have a room at 80% relative humidity (RH). They produced a nylon backing for carpet, and they needed the high RH to reduce the “stickiness” in the process. Currently he was at 40% RH in a room that was sized at 40ft long by 20ft wide by 20ft high (12.2m long X 6.1m wide X 6.1m high). He wondered if our Atomizing Nozzles could help him. I decided to put on my engineering hat to calculate the amount of water that he would need to increase the moisture content. Other markets that would require higher RH in their ambient air are wood working, dust control, laboratories, and High Voltage applications.
Relative humidity (RH) is the percentage of water vapor as compared to saturation at the same temperature. So, at 100% RH, the ambient air cannot hold any more water. With our atomizing nozzles, we can atomize the water droplets to a very small droplet to help increase the absorption rate into ambient air. This will increase the RH of a room, but I will have to determine what size and how many.
The equation that I use is as follows, Equation 1:
Imperial Units S.I. Units
H = V * RAC * (Wf – Wi) / (v * 7000) Imperial H = V * RAC * (Wf – Wi) / (v * 997.9) Metric
Where:
H – mass flow rate of water, Lbs/hr H – mass flow rate of water, Kg/hr
V – Volume of Section, ft^3 V – Volume of Section, m^3
RAC – Room Air Changes, No. per hour RAC – Room Air Changes, No. per hour
Wf – Final Water Content, Grains/lb of dry air Wf – Final Water Content, Grams/Kg of dry air
Wi – Initial Water Content, Grains/lb of dry air Wi – Initial Water Content, Grams/Kg of dry air
v – Specific Volume of Air, ft^3/lb v – Specific Volume of Air, m^3/Kg
The customer stated that the room is at 68 deg. F (20 deg C). The humidity sensor is +/- 5%; so, when the RH in the room gets to 75%, it will kick on their system. They also use a standard HVAC unit to heat and cool the room. From these factors, we can determine some of the variables above. With the water content, you can find a chart online to determine the amount of water vapor that is contained in air at a specific temperature and RH. At 68 deg. F (20 deg. C), I was able to find the following information:
Imperial Units S.I. Units
Wi = 43 Grains/lb of dry air at 40% RH Wi = 6.1 Grams/Kg of dry air at 40% RH
Wi = 80.5 Grains/lb of dry air at 75% RH Wi = 11.5 Grams/Kg of dry air at 75% RH
Wf = 85.5 Grains/lb of dry air at 80% RH Wf = 12.2 Grams/Kg of dry air at 80% RH
v = 13.35 ft^3/lb @ 68 deg. F, 1 atm v = 0.8334 M^3/Kg at 20 deg. C, 1 bar (absolute)
V = 40ft X 20ft X 20ft = 16,000 ft^3 V = 12.2m X 6.1m X 6.1m = 454 m^3
Another factor is the number of air changes in that room. With the HVAC system, it will turn on and off to heat and cool the air. Some fresh air is brought in during this cycle. With a typical system, the room air will change between 2 – 4 times an hour. So, RAC = 4/hour (worse case). (Other locations may have scrubber systems, continuous air flow systems, etc. and the RAC will be greater).
If we plug in the numbers that we have, we can determine how much water that we will need to spray into the air to increase the RH from 40% to 80%.
Now that we know the rate of water to put into the ambient air, we have to look at the set up. With the settling time of the water droplets and the location of the humidity sensor, we will have a lead/lag problem. To help in this situation, I would recommend to turn on the Atomizing Nozzles for 10 – 15 seconds, and wait 2 minutes to re-measure the RH. This will help to not over saturate the room. As for the location of the Atomizing Nozzles, you have to make sure that the spray does not contact any structure or other atomizing spray patterns. This will cause the water to condense and either coat a structure or create rain. To help with the entire system, I suggested our No Drip External Mix Wide Angle Flat Fan Pattern Atomizing Nozzle. This will eliminate a water valve at each Atomizing Nozzle. When the air pressure is turned off to stop spraying, the No Drip Atomizing Nozzle will seal and not allow any water to drip. To also help with consistent RH in the room, the EB2030SS was my choice. The spray range helps to cover the area especially with multiple units operating.
No Drip Atomizing Nozzle
To determine the number of Atomizing Nozzles, we want to look at the time determination with the controller and the intermittence of operation. With the RAC = 4/hour, the air in the room will change over every 15 minutes. We want to have a balance between the new air and the existing air. So, with the time measurement of 2 minutes off and 15 seconds on, we will have 6 humidity checks over 15 minutes. We can divide the amount of water to be injected into the room by 6 to cover that time span. Also, we have to factor in that we will not be running the Atomizing Nozzle for the continuous hour. We will have to adjust the amount for only running for 15 seconds. So, the intermittent factor will be 0.0042 (the 15 seconds portion of the hour).
In taking into consideration the flow rate required during operation time, we can calculate the amount of flow required for the Atomizing Nozzle as in Equation 2.
Imperial UnitsSI Units
Flow rate: Q = H / (D * T * f) Flow rate: Q = H / (D * T * f)
Mass Flow Rate: H = 29.1 lbs/hr Mass Flow Rate: H = 13.3 Kg/hr
Density of Water: D = 8.34 lbs/gal Density of Water: D = 1 Kg/L
Span division of time: T = 6 Span division of time: T=6
Intermittent Factor: f = 0.0042 Intermittent Factor: f = 0.0042
In the catalog, the model EB2030SS will flow 14.0 GPH (53.0 LPH) at 40 PSIG (2.8 Bar) water pressure. This would be in the compressed air pressure range of 50 PSIG (3.4 Bar) to 95 PSIG (6.5 Bar). If we divide these out, it will tell us how many atomizing nozzles that is needed to humidify the room.
Imperial: 138.5 GPH/14.0 GPH = 9.9 or 10 Atomizing Nozzles.
SI units: 527.8 LPH/53.0 LPH = 9.9 or 10 Atomizing Nozzles.
The last thing to determine is the amount of time that would be required to maintain the 80% RH when the controller calls for more humidification. At 75% RH, we can use Equation 1 to determine the amount required to reach 80%. As we plug in the initial Water Content, Wi, at 75% RH as 80.5 Grains/lb of dry air (11.5 Grams/Kg of dry air), we will get an H value of 3.42 lb/hr (1.55 Kg/hr). With each Atomizing Nozzle putting out 14.0 GPH (53.0 LPH) of water, we can determine the time to atomize the 3.42 lbs (1.53 Kg) of water during the operational time. The control will be much better as the air is changing with the new incoming air and the existing air. Thus, we have in Equation 3:
Imperial UnitsSI Units
Time (sec): T = 3600 * m/ (N * Qa * D) Time (sec): T = 3600 * m/ (N * Qa * D)
Mass of water: m = 3.42 lb Mass of water: m= 1.53 Kg
Density of Water: D = 8.34 lb/gal Density of Water: D = 1 Kg/L
T = 3600 * 3.42 lb / (10 * 14 GPH * 8.34 lb/gal) T = 3600 * 1.55 Kg / (10 * 53 LPH * 1 Kg/L)
T = 10.5 seconds T = 10.5 seconds
With some other humidification devices like steam generators, companies have to capitalize the system. With the Atomizing Nozzles, my customer was able to keep the cost down and control the RH at a high level for his manufacturing process. In turn, he was able to increase productivity and reduce downtime. If you need to increase the level of moisture in an area, you can always contact one of the Application Engineers at EXAIR for help.
John Ball
Application Engineer
Email: johnball@exair.com Twitter: @EXAIR_jb
One of the great benefits of technology is the ease with which we can take and share photos or videos. A domestic engineering firm contacted me earlier this month in search of a suitable cooling method with their application. They provided excellent details about the application, but there were still a few discrepancies between what was described, and what I thought was being described.
So, I asked for a photo, and thanks to the ubiquity of camera phones, I received the image below.
Soldered connection of harness which needed to be cooled
In this application a soldering process is performed at pin connections of an electrical harness. The harness is then inserted into a plastic housing, and the heat remaining within the soldered joint was posing problems for the next step in production of an electronic module. So, the end user, and the engineering firm, ultimately needed a suitable way to remove the heat from the soldering process.
And, in addition to this problem, the soldered assemblies were experiencing defects due to static as they were fed down the conveyor line shown below.
Module exit point onto conveyorEnd of the conveyor. When the modules would reach the end of the conveyor, they would be statically charged.
While we knew the heat from the soldering process needed to be removed, we were not 100% certain as to how much cooling (exactly) was needed. So, we opted to use the model 3930 EXAIR Cooling Kit which includes a medium sized Vortex Tube and all related generators to configure up to 10 different Vortex Tube models. With this kit we were certain that a suitable cooling capacity could be reached with the minimum amount of compressed air.
To remedy the static problem, an 18” Super Ion Air Knife was installed over the width of the conveyor. The Super Ion Air Knife was mounted with the exhausting airflow at a low, 30° angle of attack, opposite the direction of module travel. By blowing ionized air over the full width of the conveyor, the static was removed, thereby removing the process disturbance and solving the static problem.
What started as a simple email compounded into multiple applications with problems that were all solved using EXAIR products. If you have a similar application, whether for cooling, cleaning, static removal, conveying, or material coating, contact an EXAIR Application Engineer.
