Corporate Buyers Guide

Downdraft tables come in square and rectangular shapes in many sizes. The working surface, downward air velocity and type of particle filter depend on the desired application. The air velocity is depending on the fan size and area of the table. A important factor to consider is the wind noise created by the air.

Industrial tables usually have a metal grating. It may be aluminum or steel. Often it is coated with plastic or rubbery material. Fiberglass, plastic or wood composites may be available as options.

To trap particulates, cartridge filters are the most common filter media because they are available in different porosities. For low volume activity and hobby use, bag filters may be sufficient. This depends on the volume of particles produced and the acceptable throughput from the filter into the air. Bag filters do not have the removal efficiency of cartridge filters, however, they are easily cleaned for repeated use. For this reason, bag filters are also used, often as pre filters for high volume particle removal.

In industry, downdraft tables are used where grinding and welding produce dangerous fumes. Here the trapping of fumes is equally as important as trapping particles. The same is true for soldering electrical components and wires by hand.

The particles created by the grinding of certain metals such as aluminum can cause fires when left collected in filter media in open air. Tables which draw the metal fines into a water bath are used for this application. The postal service uses downdraft tables to handle material that may be contaminated with chemicals dust or bacteria.

Most tank mounted air compressors are piston compressors and usually are splash lubricated. Screw compressors are gaining more popularity because of their reliability and smooth pressure output. The piston compressor needs a tank to dampen the pressure pulsations created when the output valve opens and releases the air. Also, for all compressors, the storage time in a tank allows the air to cool and to release oil and water droplets to the bottom of the tanks to be drained off. It is, therefore, advisable to get the biggest tank possible.

Oil free tank mounted piston compressors come in single phase only. The cooling of the compressor can be with water or air.  

Piston compressors can be single or two phase. In the single phase, models having two cylinders, both cylinders work independently drawing in and releasing the compressed air. In the two phase configuration, the output from one cylinder is fed into the input of the second cylinder giving a higher pressure output, but at a lower capacity. For the two phase compressor the output temperature will be very high and most likely will need an after cooler.

With single phase compressors the maximum pressure is about 70 psig (5 atm). With two phase models the maximum pressure is about 175 psig (12 arm). The air capacity depends on the size of the system.

Capacity FAD is the measure of free air delivery which is the air volume drawn into the compressor and psig is psi gage. Gage pressure is zero at sea level.