Thursday 16 February 2023

How Exair Cold Gun Cools Brazed Plate!

Brazing is a process that joins two or more metal surfaces by letting molten metal flow into the joint. The filler metal has a lower melting temperature than the parts to be joined to keep the workpieces from melting
 Although brazing is one of the oldest joining methods, it is still used today for a good reason.

Once Our Principal Exair-USA  provides a cooling solution to a manufacturer of custom hose and tube assemblies is brazing a 6" diameter metal plate. This joint causes the plate to heat up and prevents the plate from being comfortably picked up by an operator. They are looking to speed up production rates by cooling the plate faster, allowing the operator to pick up the plate and move it to the next step of manufacturing. 


They have chosen an EXAIR Model 5330 High Power Cold Gun with Dual Point Hose Kit to provide a 2" wide blast of cold air on to the plate and produce an area of the plate which can be held by the operator and speed up production.

Model 5330 High Power Cold Gun System

The Cold Gun Air coolant System produces a stream of clean, cold air at 50°F (28°C) below supply air temperature. Operation is quiet and there are no moving parts to wear out. It will remove heat to prolong tool life and increase productivity on machining operations when liquid coolants cannot be used.

The Cold Gun is also an alternative to expensive mist systems. It eliminates the costs associated with the purchase and disposal of cutting fluids and worker related health problems from breathing airborne coolants or slipping on wet floors.

EXAIR's Cold Gun is non-adjustable to prevent freeze-up during use. Cold airflow and temperature drop are factory set to optimize the gun's cooling capability.

Padmalochan Nayak



Vivek Engineers
#22, 1st Floor, 1st Cross, 
Bilekahalli Indl. Area, Adj. IIMB Compound, 
Bannerghatta Road, Bangalore - 560 076 
Ph : 080 -  2648 1309, 4170 1145.







Tuesday 7 February 2023

How EXAIR Products Save Compressed Air Cost!

  Air is one of the basic needs of human being without which we cannot survive and air is total free. But most people think that compressed air is free. No way, it is not free at all. Because of the expense, compressed air is considered to be a fourth utility in manufacturing plants.

In this blog I am going to show the calculation of the cost to make compressed air and hope this information will be sufficient to understand the uniqueness and energy saving features of EXAIR intelligent compressed Air products.


For electric motors, the power is described either in kilowatts (KW) or horsepower (hp).   

1 hp=0.746 KW 

The electric companies charge at a rate of kilowatt-hour (KWh).  

So, we can determine the energy cost to spin the electric motors. 
If your air compressor has a unit of horsepower, or hp, you can use 

Equation 1:

Energy Cost= hp × 0.746 × hours × rate / (motor efficiency)

where:

hp – horsepower of motor

0.746 – conversion to KW

hours – running time

rate – cost for electricity, KWh

motor efficiency – average for an electric motor is 90%.

If the air compressor motor is rated in kilowatts, or KW, then the above equation can become a little simpler, as seen in Equation 2:

Equation 2:

KW × hours × rate / (motor efficiency)

where:

KW – Kilowatts of motor

hours – running time

rate – cost for electricity, KWh

motor efficiency – average for an electric motor is 90%.

Example: a manufacturing plant operates 250 day a year with 8-hour shifts. The cycle time for the air compressor is roughly 50% on and off.  To calculate the hours of running time, we have 250 days at 8 hours/day with a 50% duty cycle, or 250 × 8 × 0.50 = 1,000 hours of running per year.  The air compressor that they have is a 100 hp rotary screw.  The electrical rate for this facility is at Rs 9.4 /KWh. With these factors, the annual cost can be calculated by Equation 1:

100hp × 0.746 KW/hp × 1,000hr × Rs 9.4 /KWh / 0.90 = Rs 779,156 per year.

In both equations, you can substitute your information to see what you actually pay to make compressed air each year at your facility.

The type of air compressor can help in the amount of compressed air that can be produced by the electric motor.  Generally, the production rate can be expressed in different ways, but I like to use cubic feet per minute per horsepower, or CFM/hp.

The positive displacement type compressors have different values depending on how efficient the design.  For a single-acting piston type air compressor, the amount of air is between 3.1 to 3.3 CFM/hp.  So, if you have a 10 hp single-acting piston, you can produce between 31 to 33 CFM of compressed air.  For a 10 hp double-acting piston type, it can produce roughly 4.7 to 5.0 CFM/hp.  As you can see, the double-acting air compressor can produce more compressed air at the same horsepower.

The rotary screws are roughly 3.4 to 4.1 CFM/hp.  While the dynamic type of air compressor is roughly 3.7 – 4.7 CFM/hr.  If you know the type of air compressor that you have, you can calculate the amount of compressed air that you can produce per horsepower. 

With this information, we can estimate the total cost to make compressed air as shown in Equation 3:

Equation 3:

C = 1000 * Rate * 0.746 / (PR * 60)

where:

C – Cost of compressed air (Rs per 1000 cubic feet)

1000 – Scalar

Rate – cost of electricity (KWh)

0.746 – conversion hp to KW

PR – Production Rate (CFM/hp)

60 – conversion from minutes to hour

So, if we look at the average of 4 CFM/hp and an average electrical rate of Rs 9.40 /KWh, we can use Equation 3 to determine the average cost to make 1000 cubic feet of air.

C = 1000 * Rs 9.40 /KWh * 0.746 / (4 CFM/hp * 60) = Rs 29 /1000ft3.


Once you have established a cost for compressed air, then you can determine which areas to start saving money.  One of the worst culprits for inefficient air use is open pipe blow-offs.  This would include cheap air guns, drilled holes in pipes, and tubes.  These are very inefficient for compressed air and can cost you a lot of money.  I will share a comparison to a 1/8” NPT pipe to an EXAIR Mini Super Air Nozzle.  (Reference below).  As you can see, by just adding the EXAIR nozzle to the end of the pipe, the company was able to save per year.  That is some real savings

The table above shows the air consumption for typical homemade blowoff s. The pages that follow give the air consumption and other data on EXAIR's Air Nozzles and Jets. Consider the following example where a Model 1102 Mini Super Air Nozzle replaces an 1/8" open pipe. The compressed air savings is easy to calculate and proves to be dramatic. Payout for Air Nozzles and Jets, including filter and installation cost is measured in weeks - not years, as is the case for other cost reduction equipment. Based on a 40 hour work week, 52 weeks a year.

Example: 

1. Existing blowoff is 1/8" open pipe at 80 PSIG (5.5 BAR) supply. 

Air consumption, from the table above, is 70 SCFM (1,981 SLPM). 

2. Use a 1/8 FNPT Model 1102 Mini Super Air Nozzle also at 80 PSIG (5.5 BAR) supply. Air consumption, from the image below, is 10 SCFM (283 SLPM). 


3. Compressed air saved = 70 - 10 = 60 SCFM (1,981 - 283 =1,698 SLPM) 

4. For this example, the blowoff is continuous. If the duty cycle was 20%, then air saved would be 60 x .2 = 12 SCFM (1,698 x .2 = 340 SLPM).

 5. Most large plants know their cost per 1,000 standard cubic feet of compressed air (10,000 standard liters). If you don't know your actual cost per 1,000 SCF, Rs 29 is a reasonable average to use. 

(Cost per 10,000 standard liters is approximately Rs 10 )

 6. Money saved per hour = SCFM saved x 60 minutes x cost/1,000 SCF
                                            (SLPM saved x 60 min x cost/10,000 SL)
                                          = 60 x 60 x Rs 29 /1,000 
                                         (= 1,698 x 60 x Rs 10 /10,000)

                                             =Rs 104/hour that is =Rs 4160/week and Rs 216,320/year savings for one nozzle.

                                           


Padmalochan Nayak



Vivek Engineers
#22, 1st Floor, 1st Cross, 
Bilekahalli Indl. Area, Adj. IIMB Compound, 
Bannerghatta Road, Bangalore - 560 076 
Ph : 080 -  2648 1309, 4170 1145.



Thursday 2 February 2023

What is the Unique Design of Exair Vortex Tube and Cold Fraction?

  In various industries, it is a very common issue, that is increase of temperature of a particular spot or small tools/ parts of machines during production process. Literally we can say a small issue can affect whole production process.

Also it is really uneconomical to facilitate air conditioning entire factories and workshops. If do so, then the main problem will arise as  their sizes and other problems will be the various heats generated by production processes. Also it will be really uncontrollable to stop the cold air escaping through windows,  open doors and loading bays. Of course the industry will need a  high capacity air conditioning system i.e. expensive to purchase and also not cost effective to operate.


To resolve this problem EXAIR-USA has produced some Industrial spot cooling products . In this article I will discuss about EXAIR Vortex tube  and the Cold Fraction generated by it which can produce cold air to a temperature as low as -46°C (-50°F) and most interesting matter is that it has no moving parts, so no tear and wear and made up of stainless steel which is wear resistance, as well as its resistance to corrosion and oxidation. So Exair provides a Industrial spot cooler i.e. Vortex Tube which will provide years of reliable, maintenance-free operation.

EXAIR Vortex Tubes are available in three sizes such as small, medium, and large. These sizes can produce a range of cooling capacities from 135 BTU/hr to 10,200 BTU/hr (34 Kcal/hr to 2,570 Kcal/hr).A generator plays vital role inside each Vortex Tube to provide such cooling effect. When the compressed air enters into the vortex tube, then it is controlled by the generator that can enter the Vortex Tube and initiating the spinning of the air.  

As an example, a medium-sized Vortex Tube, model 3240, will only allow 40 SCFM (1,133 SLPM) of compressed air to travel into the Vortex Tube at 100 PSIG (6.9 bar).  While a small-sized Vortex Tube, model 3208, will only allow 8 SCFM (227 SLPM) of compressed air at 100 PSIG (6.9 bar).  EXAIR manufactures the most comprehensive range, from 2 SCFM (57 SLPM) to 150 SCFM (4,248 SLPM).

After the compressed air goes through the generator, there will be a pressure drop to slightly above atmospheric pressure.  (This is the “engine” of how the Vortex Tube works).  The air will travel toward one end of the tube, where there is an air control valve, or Hot Air Exhaust Valve.  This side of the Vortex Tube will blow hot air.  This valve can be adjusted to increase or decrease the amount of air that leaves the hot end.  The remaining portion of the air is redirected toward the opposite end of the Vortex Tube, called the cold end.  By conservation of mass, the hot air and cold air flows will have to equal the inlet flow as shown in Equation 1:

Equation 1:


Q = Qc + Qh


Q – Vortex Inlet Flow (SCFM/SLPM)


Qc – Cold Air Flow (SCFM/SLPM)


Qh – Hot Air Flow (SCFM/SLPM)


The percentage of inlet air flow that exits the cold end of a vortex tube is known as the Cold Fraction.  As an example, if the Hot Air Exhaust Valve of the Vortex Tube is adjusted to allow only 20% of the air flow to escape from the hot end, then 80% of the air flow is redirected toward the cold end.  EXAIR uses this ratio as the Cold Fraction; reference Equation 2:


Equation 2:


CF = Qc/Q * 100


CF = Cold Fraction (%)


Qc – Cold Air Flow (SCFM/SLPM)


Q – Vortex Inlet Flow (SCFM/SLPM)


EXAIR created a chart to show the temperature drop and rise, relative to the incoming compressed air temperature.  Across the top of the chart, we have the Cold Fraction and along the side, we have the inlet air pressure.  As you can see, the temperature changes as the Cold Fraction and inlet air pressure change.  As the percentage of the Cold Fraction becomes smaller, the cold air flow becomes colder, but the amount of cold air flow becomes less.  You may notice that this chart is independent of the Vortex Tube size.  So, no matter the generator size of the Vortex Tube that is used, the temperature drop and rise will follow the chart above.


How do you use this chart?  As an example, we can select a model 3230 Vortex Tube.  It will use 30 SCFM (850 SLPM) of compressed air at 100 PSIG (6.9 Bar).  We can determine the temperature and amount of air that will flow from the cold end and the hot end.  For our scenario, we will set the inlet pressure to 100 PSIG, and adjust the Hot Exhaust Valve to allow for a 60% Cold Fraction.  Let’s say the inlet compressed air temperature is 68°F.  With Equation 2, we can rearrange the values to find the Cold Air Flow, Qc:


Qc = CF * Q


Qc = 0.60 * 30 SCFM = 18 SCFM of cold air flow


The temperature drop shown in the chart above is 86°F.  If the inlet temperature is 68°F, the temperature of the cold air is (68°F – 86°F) = -18°F.  So, at the cold end, we will have 18 SCFM of air at a temperature of -18°F.  For the hot end, we can calculate the flow and temperature as well.  From Equation 1,


Q = Qc + Qh or


Qh = Q – Qc


Qh = 30 SCFM – 18 SCFM = 12 SCFM


The temperature rise shown in the chart above is 119°F.  So, with the inlet temperature at 68°F, we get (119°F + 68°F) = 187°F.  So, we have 12 SCFM of air at a temperature of 187°F coming out of the hot end.

With the Cold Fraction and inlet air pressure, you can get specific temperatures for your application.  For cooling and heating capacities, the flow and temperature can be used to calculate the correct Vortex Tube size for your application. 

Padmalochan Nayak



Vivek Engineers
#22, 1st Floor, 1st Cross, 
Bilekahalli Indl. Area, Adj. IIMB Compound, 
Bannerghatta Road, Bangalore - 560 076 
Ph : 080 -  2648 1309, 4170 1145.