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Gr0wer
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Registered: 09/16/03
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single 55 gal low pressure steam sterilizer
#22311059 - 09/29/15 09:24 PM (8 years, 3 months ago) |
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I'm considering to convert my 55 gal open top drum pasteurizer for dual purpose hot water bath and low pressure steam sterilization. I'm at 3600 feet so i feel i would really need the pressure to get any effective steam sterilization. My water boils at 205, at 2-3 psi im around 212-215F. I already have an adjustable pressure relief valve i can use for the relief, just need a good low pressure gauge and the manometer tube which will be welded on steel most likely. I plan to run it around 2-3 psi mostly for kings and LM sawdust bags prep. Any input?
Edited by Gr0wer (09/29/15 09:25 PM)
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solarity
mm... my favourite food



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Re: single 55 gal low pressure steam sterilizer [Re: Gr0wer]
#22312425 - 09/30/15 04:41 AM (8 years, 3 months ago) |
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So if the valve gets clogged you get a fountain of scalding hot water followed by a jet of steam. Unless of course you lower the water to the level of the manometer outlet at which point you get a shower of scalding hot water and steam together.
-------------------- Commercial exotics farmer for 8 years - now sold up!
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drake89
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Re: single 55 gal low pressure steam sterilizer [Re: solarity]
#22313198 - 09/30/15 09:53 AM (8 years, 3 months ago) |
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DO NOT do this. these drums are not constructed to hold pressure. I use stainless steel barrels that are much much stronger. You will simply have to run your steamer longer. I know folks that steam at 70s for 24hrs...you'll be fine. A good way to cut down your cook time would be to use wood pellets. They only require 1/3 of the time for me.
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moonlightmushrooms
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Re: single 55 gal low pressure steam sterilizer [Re: drake89]
#22315619 - 09/30/15 06:32 PM (8 years, 3 months ago) |
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Quote:
drake89 said: DO NOT do this. these drums are not constructed to hold pressure. I use stainless steel barrels that are much much stronger. You will simply have to run your steamer longer. I know folks that steam at 70s for 24hrs...you'll be fine. A good way to cut down your cook time would be to use wood pellets. They only require 1/3 of the time for me.
Would you recommend a 12 hour steam sterilization at normal pressure? Have steam enter from a larger diameter pipe than it leaves by and cook them until internal temperature gets to the boiling point? Would his 1.5Kw element be enough?
Edited by moonlightmushrooms (10/01/15 11:27 AM)
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Gr0wer
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I suppose i could play it safe and try a no pressure steam batch using my current setup with cinder blocks and some expanded steel. I plan to sterilize aspen shavings which i would imagine take the same heat treatment as wood pellets, or are wood pellets cleaner from the heat from forming of the pellets? I should also be able to pre seal my bags if i'm not using any pressure which is another bonus.
If i was to need more heat I've seen 55 gal steel drums used by a few people with low pressure, to include Roger Rabbit. Solarity, good point, i probably would want a turndown and a runoff tube to a nearby rock garden. That tube is a failsafe and would function exactly as described rather than blowing the lid or buckling.
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t3chnobily
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Re: single 55 gal low pressure steam sterilizer [Re: Gr0wer]
#22317733 - 10/01/15 07:50 AM (8 years, 3 months ago) |
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Steel drums work fine at that PSI. Mine runs around 4 with no problem. I run a 220F for 10 hrs. Grain, Supp. Sawdust no problem. The blow off tube will need to have about 6 feet of water in it to hold 2 PSI. Otherwise you'll just vent steam constantly.
What you want is a Mercoid pressure switch and a contactor operating the heating element. Otherwise it will run flat out, suck a ton of juice and burn out quickly.
Instead of welding your connections use brass bulk head fitting. Here Cheaper and easier. Welds tend to rust out and leak.
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drake89
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Re: single 55 gal low pressure steam sterilizer [Re: t3chnobily]
#22318626 - 10/01/15 11:12 AM (8 years, 3 months ago) |
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Quote:
t3chnobily said: Steel drums work fine at that PSI. Mine runs around 4 with no problem. I run a 220F for 10 hrs. Grain, Supp. Sawdust no problem. The blow off tube will need to have about 6 feet of water in it to hold 2 PSI. Otherwise you'll just vent steam constantly.
What you want is a Mercoid pressure switch and a contactor operating the heating element. Otherwise it will run flat out, suck a ton of juice and burn out quickly.
Instead of welding your connections use brass bulk head fitting. Here Cheaper and easier. Welds tend to rust out and leak.
yes, the relays and vaporstats are the way to go. rather expensive though. i think the pressure switch is like $200-300 depending on the model.
but you are one brave mofo running your barrels at 4 psi! if they decide to let go, the lid alone has like 1600lbs behind it!
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moonlightmushrooms
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Re: single 55 gal low pressure steam sterilizer [Re: t3chnobily]
#22318685 - 10/01/15 11:27 AM (8 years, 3 months ago) |
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Quote:
t3chnobily said: What you want is a Mercoid pressure switch and a contactor operating the heating element. Otherwise it will run flat out, suck a ton of juice and burn out quickly.
What about using a temp controller with a shut off at 212F?
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moonlightmushrooms
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Re: single 55 gal low pressure steam sterilizer [Re: drake89]
#22318697 - 10/01/15 11:29 AM (8 years, 3 months ago) |
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Quote:
drake89 said: yes, the relays and vaporstats are the way to go. rather expensive though. i think the pressure switch is like $200-300 depending on the model.
but you are one brave mofo running your barrels at 4 psi! if they decide to let go, the lid alone has like 1600lbs behind it!
Would one of these work with a relay to the element?
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Gr0wer
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http://www.google.com/search?q=Mercoid+pressure+switch&client=ms-android-verizon&hl=en&source=android-browser-type&v=141338691&prmd=sivn&source=lnms&tbm=shop&sa=X&ved=0CAcQ_AUoAWoVChMImseV9cahyAIVRjmICh0bfQHU#spd=7283762332135984859
This item would fit the bill since it has a 15a switch built in. That eBay item posted looks like its a 3a switch. My 1500w element draws about 12a so it would need a 15a switch or relay. And yes I don't see why you couldn't use a PID to control via temperature, temperature and pressure wold go hand in hand. You would want a PID with a SSR to control your load.
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drake89
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Re: single 55 gal low pressure steam sterilizer [Re: Gr0wer]
#22319993 - 10/01/15 04:44 PM (8 years, 3 months ago) |
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i use a honeywell vapor stat. a 5500W heater and a contactor relay keeps you from waiting all day. though if you arent using a seperate boiler then it should be sufficient.
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Gr0wer
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Registered: 09/16/03
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Re: single 55 gal low pressure steam sterilizer [Re: drake89]
#22321320 - 10/01/15 09:30 PM (8 years, 3 months ago) |
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t3chnobily, so with the switch would i still want a pressure relief valve to bleed off pressure constantly at 2-3 psi?
Drake, I'll be limited to a standard 15A 120V outlet. Im in a rental and the wife wont let me run a 240V cord through the house and out a window or door. We move out in February hopefully rent or buy a more grow friendly home. My calculator says 3.5 hours from 80F to 205 with 15 gals of water with 1500W which isn't too bad. I think 15 gals should be more than enough factoring less than .5 gal an hour boil off for say 12 hours. That leaves me with plenty of water still around the element so im not dry firing. I could turn it on at 0700 when i wake up and be done around 2300 when i go to sleep. The next day when i get home from work i can unload.
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drake89
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Re: single 55 gal low pressure steam sterilizer [Re: Gr0wer]
#22322404 - 10/02/15 07:23 AM (8 years, 3 months ago) |
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Quote:
Gr0wer said: t3chnobily, so with the switch would i still want a pressure relief valve to bleed off pressure constantly at 2-3 psi?
a pressure relief valve is to keep you from blowing you and your neighbors to hell! It's a safety mechanism. the vaporstat turns the element on and off at certain pressure points. cuts off at 0-5 psi and on at 0-16oz less than your cut off. Oh and they can fail, I've had my fail in the ON mode. Which is when I was really glad my pressure relief valve was working/not clogged.
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t3chnobily
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Re: single 55 gal low pressure steam sterilizer [Re: drake89]
#22323102 - 10/02/15 11:09 AM (8 years, 3 months ago) |
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55 gallon drum is unlikely to fail catastrophically. Starting at 5 psi you'll blow the lid gasket or one of the rolled edges will deform and you'll vent steam. I actuate my relief valve before every run. Its my fill indicator.
Mercoid controllers are serious industrial equipment. Mine has worked flawlessly for years. Ebay has loads for less than $50. Make sure you get one that measure low psi.
After 3 years of living with the beast I have found that anything less than 220F, even if your extended cooking time, results in contamination. I use chainsaw mill sawdust and supplement at 25% bran.
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Gr0wer
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Re: single 55 gal low pressure steam sterilizer [Re: t3chnobily]
#22324613 - 10/02/15 04:46 PM (8 years, 3 months ago) |
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Dang so even if i go to 4 psi im still only at 218F due to 3600ft elevation. Hopefully i have good results with long cooks.
I wish i had a mill nearby. Back in MD
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drake89
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Re: single 55 gal low pressure steam sterilizer [Re: Gr0wer]
#22325089 - 10/02/15 06:28 PM (8 years, 3 months ago) |
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Quote:
Gr0wer said: Dang so even if i go to 4 psi im still only at 218F due to 3600ft elevation. Hopefully i have good results with long cooks.
I wish i had a mill nearby. Back in MD 
will you be using dust or pellets? either way you should never need to steam more than 18hrs as long as you're above 180F.
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Gr0wer
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Re: single 55 gal low pressure steam sterilizer [Re: drake89]
#22330369 - 10/03/15 09:27 PM (8 years, 3 months ago) |
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I have a bale of aspen bedding
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drake89
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Re: single 55 gal low pressure steam sterilizer [Re: Gr0wer]
#22330395 - 10/03/15 09:34 PM (8 years, 3 months ago) |
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Quote:
Gr0wer said: I have a bale of aspen bedding
i think you should be fine at 12hrs. really even 8, but 12 should certainly be good. you're starting with dry substrate. whereas raw sawdust technobilly uses is microbiologically active.
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moonlightmushrooms
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Re: single 55 gal low pressure steam sterilizer [Re: drake89]
#22347745 - 10/07/15 09:21 PM (8 years, 3 months ago) |
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It seems like a larger (or two smaller) elements running for 12+ hours at natural pressure would do the same as shorter time/higher pressure sterilizer?
Would it be better to vent the steam half way up, or at the top? Half-way would help keep the temp up and pressure a little higher than atmosphere? Or maybe vent it just above water level, as Gr0wer has it?
I read that some DIYers use a bulkhead with aluminium foil ziptied over the top as a cheap fail safe. Any obvious issues with this idea? Maybe using a 90 degree elbow after the bulkhead to direct any overpressure failure safely?
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Gr0wer
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That design i made was venting at the top under pressure. The manometer tube is a failsafe as to not damage equipment.
I asked my friend how big of a PRV i would need on the drum and here is his response, got to love engineering friends.
"Here's a swag: The latent heat of vaporization (amount of energy required to boil, assuming it's already at 100C) of water at that pressure is about 2260 kJ/kg. I assume 5000 BTU means BTU/hr, which is roughly 1.5kW. So, you would get 1500/2260 = 0.66 grams/s steam. Hmm. Doesn't sound like much... At that pressure, the steam should have a specific volume of around 1.3 m3/kg, giving roughly 0.05 cubic meters per minute. (1.8 cfm) http://www.engineeringtoolbox.com/saturated-steam-properties-d_457.html
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