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A High Volume, Low Pressure Oxygen System for Propane Glassworking Torches

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This is my plan for a high volume, low pressure oxygen system for operating propane glassworking torches.

[Disclaimer: I know next to nothing about glassworking, and I am not an engineer.]

My only original bit on this system is a combo vacuum/pressure gage at the outputs of the oxygen generators. The generators (concentrators) contain sieve beds (for nitrogen removal) that can be damaged by a vacuum condition.

The concentrators are rebuilt home medical units.

I haven't built it yet but this system will run a GTT brand Phantom torch at full blast.

 

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The compressor is an oil-free design. Gast 86R123 Flow vs Pressure graph:

 

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The system will be assembled in a rack of 2x4 foot wire shelves.

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Detail of the Condor brand four-port pressure switch.

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Right now, I'm waiting for some parts and I need to clear my install space.

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I've decided to move to another location before I build a glass studio.

This is a commercially available HVLP system:

 

If you want to know more about the concentrators:

 

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In case anyone is wondering why I'm posting this here, it is because the president of the High Volume Oxygen company has threatened to sue people (including serving papers, I guess).  The (BS) HVO patents are here: https://www.highvolumeoxygen.com/patents/

Background: http://www.talkglass.com/forum/showthread.php?64885-oxygen-frog-verses-high-volume-oxygen-pro-and-con-im-leaning-toward-frog-thanks-craig

I've made two changes to my design after watching the Torch Talk videos.  I was planning to let the concentrators run continuously.  This would be wasteful but manageable, the wall exhaust fan would prevent excess pooling of oxygen in the work area, I think.  The solenoid bleed valve on a timer is a more elegant solution. (What is needed is for the sieves to purge for a minute or two before the oxygen reserve tank is filled.)

I was planning to purge the holding tanks at the start of each shift but would need a flow restrictor for the initial part of the fill.  My new plan will slow the compressor down until the pressure is about 45 PSI.

The speed control will be accomplished with an autotransformer from Parts Express (with a fuse added to the secondary).  A PWM fan control would likely work but the transformer should be smoother.  I would guess Oxygen Frog uses variable PWM.  My design is a two-speed arrangement after the initial adjustment.

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Edit: I love zoro.com (a division of Grainger).  They run this discount several times a year (good through the 24th):

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I've seen this compressor used most often by DIY people: https://www.zoro.com/gast-piston-air-compressor-16hp-115v-1ph-1hab-44-m100x/i/G1222715/ You will find the flow/pressure curve at gast.com.

 

Edit2: A good explanation of autotransformer motor starting: Theory Of Operation - Autotransformer Starter.pdf  (but not really the same thing as the use in my design.)  I'm quite sure the Gast 86R uses a PSC (permanent split capacitor) type motor.

And I can de-rate the primary fuse in the Parts Express variac to protect the secondary circuit.

Edit3: The timer contacts need to be rated to handle the inductive load of the solenoid.  If not, the timer should operate a power relay coil instead.

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This some good shit. Been thinking about glassblowing for while but startup just seems unrealistic for another artsy hobby :) gonna have to sit down with some time later

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I've delayed posting because the patent situation seriously angered me.  One of my grandfather's patents was stolen by DuPont.  My professor of a business law class was a partner in a law firm specializing in IP (intellectual property).  My uncle held several patents.  I have a very firm idea of what a US patent is.  There was a pdf of an earlier decision in Nebraska but I couldn't find it when I posted the material above.  Here is the decisive ruling: http://www.talkglass.com/forum/showthread.php?67570-OxyFrog-VS-Hvo

Getting back to my own stuff, I have decided to stay where I am and build my studio in the outboard half of my two-car garage.  Ventilation is critical; I will be replacing a window with a commercial fan and louvered shutters.  The O2 concentrators each draw 600W and the compressor is an inductive load so my house electrical system needs to handle the equivalent of a set of traditional HPS lights.  Ideally, a glass studio should be in a detached building for safety.  The propane tank needs to be outside and should enter the studio via rigid pipe like the black iron used for natural gas.

My torch is a GTT Mirage, something I can grow into.  It has separate input ports for the center fire and outer ring of fire.  I have a foot pedal to turn the outer ring on and off.  The center fire is the same as a GTT Lynx.  The Lynx will run best on a 10 lpm concentrator that has been modified to provide 20 PSI (10 PSI is typical).  When you add an annealing kiln, this all adds up to major money.  I chose to call lampwork alternative therapy when it became clear I would not be getting what I wanted from the healthcare system.

There are two major divisions of lampworking: soft and boro.  The borosilicate has a COE (coefficient of expansion) of around 33.  Soft glass requires less flame heat and has a COE of 99 (and the less popular 104).  Boro is used for "functional" glass: pipes, bongs, rigs, etc.  Soft glass is typically used by beadmakers (although boro can be used (but never together, they would crack)).  Beads can be made with a "hot head" torch, no oxygen needed.  Like many forums these days, the glassworking ones are pretty dead but beadmakers are at http://lampworketc.com/forums/  I've never gone to reddit before but there is https://www.reddit.com/r/lampwork/ 

If I were to recommend a budget boro setup I think I'd say:

Torch: GTT Bobcat $195  https://www.mountainglass.com/GTT-Bobcat (MGA is often considered the best flamework supplier; I've been very happy with them.)

Oxygen: the simplest system is a welding tank with a regulator but this becomes an ongoing expense in terms of dollars and convenience.  So I'd say look at craigslist for a used concentrator, preferably a 10 lpm but the 5 lpm are more common.  The 5 lpm models use almost as much electricity.  (A pisser is, new medical concentrators require a prescription because they are considered durable medical equipment by US regulations.)  I bought my concentrators from here but they are still in the shipping box so I can't vouch for the quality of refurb. https://saltcityglass.com/products/platinum-10-flash-sale/ (They seem to have sales during the winter.)  $600

Hoses: they need to be "T" rated for propane, standard oxy/acetylene hoses will break down chemically.  Propane regulator $85 https://www.mountainglass.com/Single-Stage-0-30-psi-Fuel-Gas-Regulator-National

Annealing kiln: you need this to prevent your work from cracking after you make it, also used for preheating.  I bought a bigger model but here is one with a 9 x 9 x 9 inch interior: https://www.theglasshive.com/collections/aluminum-body-kilns/products/short-deep-and-tall-guy  $975 delivered. (beadmaking kilns are shorter and cheaper)

For boro, it is recommended to work with clear glass first before moving on to color.

Major cities have glass blowing classes but they are usually the glory hole furnace type.  Boro classes are typically secondary but you can find references for one-on-one instruction.

Edit: this table is from Mountain Glass Arts:

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