Technical Contacts l Technical Information l Warranty Information
DXF files l MSDS l F.A.Q.

Gast provides unparalleled technical support to our customers. Our team of trained experts in product and process technologies are always on call to solve your toughest challenges.

Technical Assistance Representatives:
Ph: 269-926-6171 Ext: 5404

Warranty Analyst:
Ph: 269-934-1268

Customer Technical Support e-mail: technical.gast@idexcorp.com

Customer Technical Support Fax: 269-927-5727

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Here is some valuable technical information on
various product Applications.

Air Flotation Table
(To determine the cfm required to float an object)

1. Psi to float the object = weight of object(lbs)/surface area of bottom of object (square inches)

2. Determine number of holes and size of holes

3. Using the psi determined from #1, go to a chart showing cfm thru an orifice(hole size), and determine cfm thru each hole

4. Required total cfm = no. of holes x cfm (for each hole)

5. From Gast catalog, determine the best compressor/blower for the application

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Air Knife

Blower sizing for air knife
Sizing a blower for an air knife application is not a simple process. The velocity of air required depends on how fast the material to be dried passes under the air knife. With a blower as an air source, the higher pressure developed by the blower will increase the air temperature, resulting in a better drying process. Designing of equipment should include work to minimized air friction losses in plumbing connecting the air knife to the blower. It is best to use a larger pipe size than the air source discharge. The best method to determine the air consumption of an air knife is to test it. To increase the airflow exiting an air knife, the pressure must be increased four times.

Air Knife Facts:
A. To get equal distribution of air across the length of the air knife, the opening area must be 1 1/2 to 2 times smaller than the cross sectional area of the knife housing.
B. Different air velocities are required depending on the surface to be dried. Higher velocities are necessary if liquids tend to cling to the surface. For proper drying, the velocity may vary from 5000 to 20,000 feet per minute.
C. Higher blower pressure capability may be required to overcome restriction resulting from plumbing between the blower and the air knife.
D. The air knife should be located as close to the surface to be dried as practical.
E. Air Velocity,V(FPM)=3204 times times the square root of pressure (pressure, IN-H2O), this is an approximation since the knife edge radius or sharpness can change these values considerably
F. Air Velocity, V=Q(air flow in cfm) divided by A(area of opening in square feet)

Hot Tub/Tank Aeration

Size of blower to be used depends on the water depth and the surface area:
Blower Model

Tank Pump Down Times
An approximation of time can be determined as follows:

t=V/Q (N)

where
t = time in minutes
V= volume to be evacuated in cubic ft
Q= average capacity*
N= 1 for vacuums to 15 in-Hg
2 for vacuums greater than 15 but less than 22.5 in-Hg
3 for vacuums greater than 22.5 but less than 26 in-Hg

* using advertised vacuum curves use the above formula to calculate time in 5 -hg increments, then add each time increment to get the total time

note: add a 25% safety factor for system leakage

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Tank Pump Up Time
An estimated pump up time can be calculated as follows:

T=V(P2-P1)/P0(Acfm)

Where:
T= time in minutes
V= tank volume in cubic feet (cuft=gallons/7.48)
P0= atmospheric pressure in psia
P1= initial tank pressure in psia
P2= final tank pressure in psia
Acfm= average cfm during pump up

To use chart above:
1. determine pressure range___________
2. determine tank size_________________
3. amount of air required by application__________________
4. cubic feet of air(in pressure range) from chart____________________
5. air flow (in pressure range) of pump of choice______________
average compressor flow between starting pressure and final pressure)
6. "4"/("5"-"3")= minutes ON____________________
7.("5"/"3")/"3" = minutes OFF_________________

Vacuum at different elevations
From catalog performance curves for a specific vacuum pump, determine the pump's maximum vacuum capability. Use this to determine what % it is of perfect vacuum at sea level. (Example: if a pump is capable of 25 in-Hg vacuum at sea level, it's capability is 83.4% of perfect vacuum [25/29.92]).

Example:
The barometer reading at 5000 ft is 24.9. The maximum vacuum capability of the 25 in-Hg pump at that altitude is 83.4% of 24.9 in-Hg or 20.8 in-Hg.

Performance at different elevations

A 10% decrease in air density reduces performance by 10%. For example: If a blower produces 110 cfm at 40 in of water pressure, with a 10% decrease in air density, it will produce the same air flow at 90% of 40, or 36 in of water.

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Vacuum Lifting
Theoretical lifting force of a vacuum cup

W=C(P)(14.7)/F(29.92)

Where:

W = force in lbs
C = area of cup (sq in)
P = vacuum level in in-Hg
F = safety factor

Better than choosing the smallest cup that will work, use the largest possible cup to ease requirements on the vacuum pump. It is better to use a larger cup than to overwork the vacuum pump. Use a safety factor of 4 for vertical movement and a safety factor of 2 for horizontal movement.

Application Notes:
Porous material -- use a smaller size cup unless a very high flow of air is available

Metal Parts - use six or eight evenly distributed cups instead of two or three smaller cups which calculations show should be able to lift the weight of the plate.

Vacuum Hold Down

The maximum hold down force on an object, at standard atmospheric conditions with a perfect vacuum, is 14.7 psi. The actual force depends on the vacuum level capability of the vacuum pump, the barometer in your area, and the surface area of the object that is in contact with the vacuum. For example, if you were to use a Gast 0323 oilless model (capable of 25 in-Hg) as the vacuum source in an area with a standard atmospheric pressure (14.7 psi), the maximum hold down force would be 12.3 psi (25in-Hg¸2.03). If the hold down table has four (4) ½" diameter holes, the maximum hold down pressure would be .196 sq-in x 4(or.79 square inches) x 12.3 psi or 9.7 psi.

Additional hold down force is required if an object is being held for fabricating purposes, which may produce side, or twisting loads. If the hold down table surface is smooth, the object may tend to move no matter the hold down force. Therefore, it is recommended that a non-skid hold down table surface be used if possible. Hold down of a small part may not be possible unless a limited amount of fabrication is being done to it.

To select the best product for an application, be aware that a vacuum pump, such as the 0323, is best for use with materials that air will not easily be drawn through. Blowers, on the other hand, are best to use with porous materials, since blowers pull large volumes of air

Air Flow Through an Orifice

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