TRAINING

Vacuum technology

 

 

Magdeburg hemispheres

 

 

Table of contents:

 

• ¿What is vacuum?
• Units
• Vacuum levels
• How to power a vacuum generator
• Head losses in vacuum circuits
• How to size the vacuum circuit

 

 

¿What is vacuum?

By definition, vacuum is the total absence of matter in a space or place, or the lack of content inside a container.

On a practical level, any volume whose air pressure is below atmospheric pressure is considered to be in a vacuum state.

 

 

 

Units

Vacuum corresponds to a state in which air pressure is below atmospheric pressure. Therefore, the units used are the same as those for pressure.

The pressure unit of the International System (SI) is Pascal (Pa), although the bar or KPa are also commonly used, among others.

 

Conversion table

 

bar	Pa(N/m2)	atm	PSI	kgf/cm2	mm Hg	mm H20
1	100000	0,987	14,504	1,02	750,064	10197,11
0,00001	1	9,869·10-6	1,5·10-4	1·10-5	0,007	0,102
1,013	101325	1	14,696	1,033	760,002	10332,22
0,069	6894,759	0,068	1	0,07	51,715	703,06
0,981	98066,52	0,968	14,223	1	735,561	9999,95
0,001	133,322	0,001	0,019	0,001	1	13,6
0,0001	9,807	0,0001	0,0014	0,0001	0,073	1

 

 

Vacuum levels

Depending on the pressure that's reached, the vacuum can be classified as low, medium or high. In the applications referred to in this catalogue, a high vacuum is never used because in no case is it necessary, and the energy required to achieve it would be extremely high.

 

 

 

 

Absolute vs. Relative pressure

 

 

 

 

How to power a vacuum generator

 

Air pressure port

Connect an air tube/hose from the compressor to the generator's air pressure port. The tube must have the appropriate internal diameter for the generator's pressure port (never one that's smaller). To do so, observe the input element assembled by AR or consult the pages of this catalogue or the corresponding technical manual.

 

 

Recommended working pressure

To get the best performance out of the AR vacuum generators, an actual feed pressure of 5.5 bar or higher is recommended. This measurement must be taken at the generator input, since, at other points in the installation, the measurement could be misleading.

 

 

 

 

 

Head losses in vacuum circuits

 

Several factors cause head losses (drop in pressure level) as air moves through the line from the compressor to the generator:

 

• Tube length. SOLUTION: try to reduce the distances. In the event of long lines, install a tube diameter greater than the recommended one, and finally reduce it at the generator input.
• Impediments to air circulation, such as necking and elbows. SOLUTION. Try to reduce the number of elements of this type. Always check the nominal internal diameter of the joints and auxiliary elements, and make sure it's not less than the overall diameter chosen for the condition. Choose the correct size for the auxiliary components such as filters and regulators.

 

 

 

How to size the vacuum circuit

 

Puerto de vacío del generador

Connect a vacuum-suitable tube/hose of the same internal diameter as the generator's suction port. A tube diameter smaller than required reduces the generator's performance. A larger diameter than required lengthens evacuation times, also increasing response time.

Hoses suitable for vacuum where Ø ≥ 20 mm

 

 

Recommended tubes for different suction ports:

 

Vacuum distribution

Starting from the main vacuum line connected to the generator, the different branches must be sized so that the tube sections go from bigger to smaller until reaching the suction cups.

Avoid "T" type bifurcations with the same input size as both outputs. The input area must be approximately the sum of the output areas so that the flow can be distributed.

A good solution in the case of several suction cups is to have a vacuum distributor (rigid strip) with an internal cross-section equal to that of the main vacuum line. This distributor connects to the main line (vacuum hose) and has as many outputs as suction cups we want to connect to.

Example: 40 x 40 mm square cross-section tubular distributor, G1" input and 6 G1/4" outputs.