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Fume and dust extraction processes with high vacuum.

 

 

In engineering and applied physics, vacuum refers to any area where the pressure is significantly lower than atmospheric pressure.

The quality of a partial vacuum refers to how close it is to a perfect vacuum. All other things being equal, lower gas pressure means higher quality vacuum. For example, a typical vacuum cleaner produces enough suction to reduce the air pressure by about 20 per cent.

Vacuum quality is divided into ranges according to the technology required to achieve or measure it. These ranges are defined in ISO 3529-1:2019 as shown in the table below:

Pressure range	Description	The rationale for defining ranges is as follows (typical situations):
The rationale for defining ranges is as follows (typical situations): Current atmospheric pressure (31 kPa to 110 kPa) to 100 Pa	Low vacuum	Pressure can be achieved with simple materials and positive displacement vacuum pumps; viscous flow regime for gases
<100 Pa to 0,1 Pa	Medium vacuum	Pressure can be achieved with complex materials and positive displacement vacuum pumps; transitional flow regime for gases
<0,1 Pa to 1 × 10 −6  Pa	High vacuum (HV)	Pressure can be achieved with complex materials, elastomer seals and high vacuum pumps; molecular flow regime for gases
<1 × 10 −6  Pa to ​1 × 10 −9  Pa	Ultra high vacuum (UHV)	Pressure can be achieved by elaborate materials, metal seals, special surface preparation and cleaning, baking and high vacuum pumps; molecular flow regime for gases
below 1 × 10 −9  Pa	Extremely high vacuum (XHV)	Pressure can be achieved with complex materials, metal seals, special surface preparation and cleaning, baking and additional degassing pumps; molecular flow regime for gases

 

Suction is the everyday term for the forces experienced by objects subjected to the movement of gases or liquids travelling along a pressure gradient. However, contrary to popular belief, the forces acting in this case are not caused by low pressure (vacuum) but by high pressure.

When the pressure in one part of a physical system is reduced relative to another, the liquid or gas in the higher pressure region will exert a force relative to the lower pressure region, called the pressure gradient force. If all gas or liquid is removed, the result is a perfect vacuum where the pressure is zero. Therefore, negative pressure forces cannot be generated. Accordingly, from a physics point of view, objects are pushed, not sucked.

The pressure reduction can be static, as in the piston and cylinder arrangement, or dynamic, as in the case of a vacuum cleaner, where the air flow reduces the pressure zone.

When living beings breathe, the muscles around the diaphragm and rib cage cause a volume change in the lungs. The increased volume of the thoracic cavity reduces the pressure inside, creating an imbalance with the ambient air pressure, which causes suction. Similarly, when a liquid is drawn into the mouth using a pipette, atmospheric pressure pushes the liquid through the pipette along the pressure gradient.

In accidents involving spacecraft or aeroplanes, a common mistake is made when objects are ejected in the event of an uncontrolled depressurisation, incorrectly referred to as objects being sucked out. This is not suction, but pushing.

 

The performance of a high vacuum suction unit can be measured by several parameters:

Air flow, in litres per second [l/s] or cubic feet per minute (CFM or ft 3 /min)
Air speed in metres per second [m/s] or miles per hour [mph]
Suction, vacuum or water lift, in pascal [Pa] or inches of water
Suction (Pa):

Suction is the maximum pressure difference that the pump can create. For example, a typical household vacuum cleaner has a suction value of approximately negative 20 kPa. This means that it can reduce the pressure inside the hose by 20 kPa from normal atmospheric pressure (about 100 kPa). The higher the suction rating, the more powerful the cleaner. 1 inch of water equals about 249 Pa; therefore, the typical suction is 80 inches (2,000 mm) of water.

Input power (W):
The power consumption of a unit in watts is usually the only figure stated. Some manufacturers only give the current in amperes (e.g. ‘6 amps’) and the consumer has to multiply this by the mains voltage to obtain approximate power ratings in watts. (Watt=Voltage x Amps) 
The rated input power does not indicate the effectiveness of the unit, but only how much electricity it consumes.
After August 2014, due to EU rules, the production of vacuum cleaners with a power consumption of more than 1600 watts was banned within the EU, and from 2017, the production of vacuum cleaners with a power consumption of more than 900 watts was not allowed.  
Output power (AW):
The amount of input power converted into airflow at the end of the suction hose is sometimes specified and measured in airwatts. The units of measurement are simply watts. The word ‘air’ is used to clarify that this is output power, not input electrical power.
Airwatt is derived from British units. ASTM International defines an airwatt as 0.117354 × F × S, where F is the air flow rate in ft 3 /min and S is the water pressure in inches. 
Peak horsepower:
The peak horsepower of a unit is usually measured by removing the cooling fans and calculating the power based on the motor power plus the rotational inertia energy stored in the motor armature and centrifugal blower. The peak horsepower rating is usually an impractical figure and is only valid for a very short time. Continuous power is usually much lower.
Air flow rate:
Typical units for expressing air flow rate are  
By volume
- m 3 /min (cubic metres per minute)
- m 3 /h (cubic metres per hour)
- ft 3 /h (cubic feet per hour)
- ft 3 /min (cubic feet per minute, also known as CFM)
- l/s (litres per second)
In mass
- kg/s (kilograms per second)
Air flow can also be defined in terms of air change per hour (ACH), which indicates that the volume of air filling the area in question is exactly replaced.
The simplest formula for volumetric air flow is Q=V.A. Q=flow rate, V=air velocity, A=sectional area through which air passes.
The formula m=p.v.a is used for mass air flow rate. m=mass flow rate (kg/s), p=density (kg/m³), v=velocity (m/s), a=sectional area (m²)

 

 

High vacuum units are used in many areas of industry. 
The main parts of particular interest to us are the following:
- Fume extraction via manual welding torch
- Fume extraction via automation welding torch
- Fume extraction via robotic welding torch
- Dust extraction from grinding machines
- Dust and chip extraction from machining centres
- Suction of cutting dust from the source
- Suction of stone/marble dust from the source
- Suction of machining burrs at source
- Industrial cleaning processes

We manufacture and import specialised high vacuum units for the above and more.
We also supply auxiliary equipment for dust and fume extraction.
These can be suction equipment mounted on torches, dust suction caps for angle grinders and more.

 

HiVent Technology, 03/12/2024, Ankara