Shutdown solenoids are expensive?

[sos]

I'm going to build a ribbon burner forge. A solenoid shutoff on the gas flow in case of power loss sounds like a great idea.

How large do the inlet/outlet ports need to be for gas flow rate? I've got 11" WC propane (plenty of flow rate). Right now, the forge is 700 cubic inches, so maybe 300k BTU?

The solenoid valves I've been looking at are north of $100, which I was not expecting.

Advice will be greatly appreciated.

Steve

[Frosty]

Welcome aboard Steve, glad to have you. I can't help you with your question. I run (Naturally Aspirated) NA, ribbon burners and never leave the running unattended much longer than it takes to relieve myself or get something out of the fridge. 

What's going to happen if the blower shuts off while it's burning? Big yellow billowy flames rolling out of the forge's doorways and burner ports. Right? I could let that go on until the propane bottle was empty without doing worse than covering everything in the shop in condensation. 

Propane produces nominally 91,333 btu per gallon. What you need to know is how many BTUs per HOUR are required for your application. 300,000 BTU/second could be a Star Wars weapon. 300,000 a day would make an okay small house heating system for a warm climate. 300,000BTU/hr should be a nice amount of too much for a 700 cu/in forge.

Depending on how you build the forge that is.

I'm not trying to mess with you here Steve but there are a lot of factors to account for. It's one reason we fid ourselves trying to talk beginners into making much smaller forges for their first. You have't told us what you want a forge that large for yet so I have to guess assuming that IS what you really want/need

Still no help regarding solenoids though. Maybe talk to somebody who does HVAC service and repair to see if you can salvage one off a gas appliance that's been replaced? They'll be able to explain the hows and whys if they like you. Be careful what you tell them about needing one for though, liability issues can cause them to clam right up regarding home made gas burning appliances. 

Frosty The Lucky.

[sos]

Thanks Frosty. Been a long time since corresponding with you on TheForge.

BTU/hour I should have said. I wanted something larger; I've had trouble fitting scrolls into a forge based on a 5 gallon bucket shell.

Steve

[Frosty]

I'm still subscribed to TheForge there just isn't much traffic, a bit more than a month since the last post. 

We tend to go into those details if they're excluded from the question, even if we know the asker knows. There are more than 56,000 members on IFI and we're answering these things for thousands of folk who may not know.

What shape are you making the forge? How are you making it, from what, etc.?

What have you been up to? Long time no talk.

Frosty The Lucky.

 

[sos]

Details (even extraneous) are much appreciated, that's why I asked here.

I have the base from a forge I made years ago. The top was intended to unbolt and be raised up on firebrick as needed; the sides didn't seal well, leaked the hot stuff. The base has legs and end shelves (firebrick doors), might as well use it.

The body will be a bit more than half a cylinder; I like to go past half on the cylinder to gain some height without a lot of loss in width. 13" diameter, 16" long. A friend has a roller, I've already got the 16 gauge. I'm still thinking on the size, if I really want it that large.

Two layers of 1" 2600F wool, spray with rigidizer and dry. Kasto-lite 30 over the wool. I like 1/4-3/8" to keep the thermal mass down. All stuff I have on hand, which is nice. I lay a floor of insulating brick and then put 1/2" or so of Kasto-lite over the top. I haven't done any welding for a long time; if I did, I'd get some kiln shelf to protect the floor.

My forging slowed down a lot 10 years ago, when we moved into a 90% complete house. I made large strap hinges for the saloon doors on the shop and barn, then many other tasks took over. I was laid off in 2015--more time, right? except hard to focus on anything except finding work. I found work 2018 in Seattle for 2 years, Massachusetts for 1 year and as of April, I'm retired! I am greatly enjoying being retired.

Steve

[Irondragon Forge ClayWorks]

How often do you loose power? I would think just a manual 1/4 turn ball valve would suffice. Unless like Frosty said you are planning on leaving the forge running unattended for long periods of time.

[sos]

I think you two are right. The only time I'd worry is if the forge was unattended--that's easy to fix. If I leave the room, turn off the forge first. It should reheat pretty quickly.

[Frosty]

Steve: Have you kept up on Insulating Fire Brick (FB)? The current consensus is Morgan Thermal Ceramics K-26 IFBs are the way to go. They have a working max temp of 2,600f and withstand the rapid thermal cycling of propane forges without crumbling. They also remain reasonably hard at temp. The price in Anchorage is less than 1/2 the old type IFBs. 

A good kiln wash like Plistex 900 will make them reasonably flux proof and provides a surface that is a poor thermal conductor with a high working rating, 3,000f+ so it provides a strong IR er-radiating interior surface. The fire heats the kiln wash which passes it to the rest of the liner poorly so it radiates it back to the forge interior strongly. 

It's the icing on the forge liner layer cake. 

Your forge sounds good to me so far. The circular top helps circulate the flame and in my opinion forms a radiating surface with a focus near the center of the floor. I could be wrong about the last I haven't checked but it sounds good to my voices so I'll think its possible if not probable.

Frosty The Lucky.

[sos]

I'm finding all kinds of stuff in the shop, now that I have time to look. Yesterday I opened a box of 12 Thermal Ceramics IFB. Note that the box does not say Morgan, just TC. Looks like the merger was in 2010. The bricks have 28 stenciled on them, so I suspect 2800F. No labels or identifying numbers on the box. I did see your posts on the K-26 bricks, will keep them in mind when I use these up.

Did you get anywhere making an IR coating? I happen to have a bag of zirconia. I remember reading a lot of posts on the idea but didn't find conclusions.

I think your idea about the focus is good. At forge temps, most of the heat transfer is radiative from what I've read.

The forge plan changed somewhat tonight when on the back of a shelf I found a blown ribbon burner that has never seen significant heat. It's made from a hard firebrick, so I'm not sure how long it will last. 24 holes, 5/16 dia that steps to 1/2" for the last 1/2". I should be able to cobble that to the old forge--it's all there, I just need to make cut outs for the burner and coat the exposed wool with refractory. I can also seal up the edges with some additional wool and refractory. The wool used to have maybe 1/16" of Satanite over it, falling to bits now. I understand the part about wool fibers being even worse to breath after they've been at heat. When I work on refractories, I do it outside, with a mask and I shower / wash clothes immediately after. Wind at my back if there is any.

So the new forge plan is to experiment with the existing ribbon burner / revived forge body and see how it works.

[Latticino]

6 hours ago, sos said:

11" WC propane

That's quite low pressure for propane.  I use around 7" WG Natural gas in my forced air burner and I have a 1" line leading up to it.  Forge size is approximately 6.5" diameter by 14" length (around 465 cubic inches interior).

Gas rated solenoid valves can be pretty expensive, but you can find them cheaper than $100+.  If you drop the size down, or go with a lower voltage valve and a relay/transformer rather than line voltage you may be able to get them cheaper, or steal one from a broken furnace (as was suggested).  YOu may be able to drop the size down if you put your safety valve in the higher pressure location (before the drop to 11" WC)

[sos]

I would have to change a not cheap regulator to raise the pressure, so I'm trying to see what I can do with 11". Good ideas, let's see what happens.

[Frosty]

The problem running such low pressure will be getting flow into the static pressure generated by the blower in the mixing tube. 

I'd experiment with the burner block you found before fitting it to the forge. Better to find out if and how it works beforehand, yes?

Frosty The Lucky.

[sos]

Frosty, I think it's worse than fighting the blower. Just getting the cubic feet of gas through connections at that low pressure looks pretty limiting. I found a 3/8" stainless flexible hose online that will only do 114k BTU/hour at 11" WC. That's pretty limiting for a gas forge.

Friday the propane guy is going to come out to look at what would be involved in changing the shop from 11" WC to 10 psi propane. Then I will be able to get into much more trouble.

Steve

[Frosty]

I can't be of much help I'm afraid. I can't imagine building a propane forge, NA or gun with only 11" WC available. 

I'll be following along to see what you have to do and how it works. 

Frosty The Lucky.