downdraught table v extraction arms

[eggs]

Hello all, today i was servicing a clients wallmount again, which is installed in a very, very dusty environment.
When we started chatting, i got into full salesman mode telling him, he needed to get rid of the air conditioning and have us install a full fresh air ventilation system insted. With local extraction for the dust source
As is the norm for salesmen i promised the earth, yet to deliver the goods i need to decide whether to install a downdraught work table or a high velocity/vacuum extraction arm to take away the dust created from the grinding/sanding process used in the lab.

Another thought for dusty environments.
If we were to use an Evaporative Cooling system, would this saturate the air enough to weigh down the airbourn dust?

What are your ways of cooling dusty environments?

cheers

eggs

[US Iceman]

Eggs,

This is getting into very specialized design requirements. I have not been involved in exhaust/fume hoods; but have seen some of the implications.

You should be aware that these can be very difficult to balance on the air side. The air entering the sash must provide a uniform velocity to draw fresh air past the person, without contaminating their breathing supply.

Cooling is a separate issue, for the make-up air, that must be addressed to eliminate any moisture problems in the lab.

Try these links for additional information.

http://www.northwestern.edu/research...labsafe/hoods/

http://www.labconco.com/manual/hood/index.shtml

http://www.esmagazine.com/CDA/Articl...101075,00.html

If you are trying to ventilate an entire area (instead of a specific lab stand) you may have to treat it much the same way you would with a clean room system. You will probably not require extreme cleanliness (like PC chip manufacturing) but you may be able to configure a cost effective system by following some of their examples.

Hope this helps.

[eggs]

Thanks for the reply, this is my solution!!

Lets se if it works

I am going to propose, rip out the wallmount. Install a ducted split in a non-dusty office away from the lab, with a remote temp sensor (in the dusty lab) and a fresh air intake on the inlet side.This will stop the coil and filter blocking up with dust and keep the temp in check.
Next a local exrtraction arm for the gringing dustas www.nederman.co.uk

cross my fingers and offer it on a leasing deal

thanks for the links

cheers

eggs

[frank]

I am going to propose, rip out the wallmount. Install a ducted split in a non-dusty office away from the lab, with a remote temp sensor (in the dusty lab) and a fresh air intake on the inlet side.This will stop the coil and filter blocking up with dust and keep the temp in check.
Next a local exrtraction arm for the gringing dustas www.nederman.co.uk

Thats fine if you are going to balance the air volumes, i.e. air in = air out or maybe even slightly less extract to keep the lab at positive pressure, but you will have to size the cooling load on full fresh air input (27C external in summer - UK conditions).
How will you control the room temperature? Most cassettes or ducted units are designed for a dt of 6K so with an ambient of 27C you will not get much room cooling.
During low ambients the compresor will be off as the room will be calling for heating. How will you provide heating? How will you stop the indoor fan overcooling the room when the stat is satisfied?

If you are going to use a dedicated air extract system then you will have to consider where the make up air is coming from. A ducted unit may not be the best way to provide this and I feel that you may be more sucessful with a small AHU with electric heat and thyristor control and a DX coil. The controls will need to be a little more advanced, possible like the Mitsi Alpha range.


You can't apply a heat pump to deal with full fresh air input.

[eggs]

thanks for the interest Frank

The air on the inlet is based upon "10% fresh air is better than no fresh air" principle.
The extract arm is not running all the time, only when the grinder is grinding.

And for the delata t, Please Mr Parry Close You Eyes, i am looking at siteing the fcu in an unoccupied,un-heated, shaded office, chilling a work area of appx 33degC, ie almost always calling for cooling.

as for air extract, well my final proposal is a chip shop type canopy over the bunson burners, to take the heat away.
Mr Parry, read it and weep.

cheers

eggs

[US Iceman]

and a fresh air intake on the inlet side

Are you planning on using 100% outside air, or using the room air as the return, plus the 10% (??) outside air?

I think Frank brings up some very good points.

You should carefully evaluate the requirements and design the system to do what you want, rather than modifying a standard system.

Your chances for success and a happy client could be much better than crossing your fingers.