A gallery of home built hoods and fume scrubbers _hood_

[4metals]

With a 10 cfm venturi and 3 tubes 48" long and 6" diameter you should achieve good fume scrubbing efficiency and the pH in the reservoir will be influenced by any inefficiency of the scrubbing. Keep the water as neutral as practical and put a pound or 2 of marble chips in the bottom of the reservoir to help buffer the pH.

The tube is because the venturi will spit all of the scrubbed air into the reservoir which includes a lot of bubbles. What can happen is the intake to the pump may suck in air if you do not redirect those bubbles. If that happens the pump will run in cavitation and stop pumping. The pipe simply re-directs the bubbles upward and the water flows out under the pipe which is not attached to the bottom, it just sits there. You can add a few holes towards the top in case your reservoir water level gets low but the concept is simply to redirect upward the air entrained by the venturi.

 

[geoffrod]

With a 10 cfm venturi and 3 tubes 36" long and 4" diameter you should achieve good fume scrubbing efficiency and the pH in the reservoir will be influenced by any inefficiency of the scrubbing. Keep the water as neutral as practical and put a pound or 2 of marble chips in the bottom of the reservoir to help buffer the pH.

The tube is because the venturi will spit all of the scrubbed air into the reservoir which includes a lot of bubbles. What can happen is the intake to the pump may suck in air if you do not redirect those bubbles. If that happens the pump will run in cavitation and stop pumping. The pipe simply re-directs the bubbles upward and the water flows out under the pipe which is not attached to the bottom, it just sits there. You can add a few holes towards the top in case your reservoir water level gets low but the concept is simply to redirect upward the air entrained by the venturi.

Ah got it, thanks for the detailed explanation.
so marble chips you mean calcium carbonate?

 

[4metals]

Yes here in the states garden centers sell bags of chipped marble, small stones crushed into gravel size, for use in gardens or ponds. Marble is calcium carbonate and the larger pebble size will slow any dissolution.

 

[geoffrod]

Yes here in the states garden centers sell bags of chipped marble, small stones crushed into gravel size, for use in gardens or ponds. Marble is calcium carbonate and the larger pebble size will slow any dissolution.

I couldnt get marble chips, but i found the pet place down the road is using decomposing coral for that same purpose in his fish tanks. so i got some of it

 

[4metals]

I couldnt get marble chips, but i found the pet place down the road is using decomposing coral for that same purpose in his fish tanks. so i got some of it

New South Wales, Australia, coral makes sense.

 

[geoffrod]

So a bit of an update
I have a 170 litre drum, fitted a plywood platform to the bottom by cutting a hole in the plywood and slipping the barrel thru, then attached struts to the platform which are then attached to the upper retaining ring (plywood)
the new pump was fitted to the platform and plumbed into the bottom drum bulkhead fitting. from the outlet of the pump we run to the venturi fitting then the water returns to the drum thru a 20mm pipe standoff which sits inside a loose DN40 pvc pipe, video shows the pump working and i attached a vacuum gauge to it to measure the strength of the suction, not quite 10 InHg vac, im not too sure if this is relevant or not and would appreciate if those cleaver people here could enlighten me as to whether this will be what is required to draw fumes from a single 2000ml reaction beaker thru my wet scrubber.
cheers
Geoff

 

[geoffrod]

@4metals, i wonder if you could elaborate on this photo.
What is the cap made from please.
Kind Regards
Geoff

 

[Yggdrasil]

@4metals, i wonder if you could elaborate on this photo.
What is the cap made from please.
Kind Regards
Geoff

It do not need to be this fancy.
An inverted funnel i bit wider than the beaker will do.

 

[geoffrod]

It do not need to be this fancy.
An inverted funnel i bit wider than the beaker will do.

yes i have those coming, but was worried about the suction from the water aspirator being strong enough to get all the fumes.
BTW i hooked the water aspirator up to 1 of my scrubber canisters and can here the fluid inside bubbling so i assume it is working.

 

[Yggdrasil]

yes i have those coming, but was worried about the suction from the water aspirator being strong enough to get all the fumes.
BTW i hooked the water aspirator up to 1 of my scrubber canisters and can here the fluid inside bubbling so i assume it is working.

It is important the there is a flow so it need to be slightly open in the reaction end.

Edit due to cell phone writing.

 

[geoffrod]

It is important the there is a flow so it need top be slightly open in the reaction end.

Ok i understand, if i stick a cap in the beaker and it seals i wont moove anything. thanks for the clarification @Yggdrasil