Gas Forge Safety

[brian]

Just finished building an lpg gas forge with blower .Tried it out today and it works fine ,red-yellow heat very quickly at 5 psi but have read that there is a safety risk if the blower cuts out while the forge is going .
Has anyone had experience with this or know about it?
Can I do anything to make the forge safer?:confused:

[ThomasPowers]

You just get a large plume of burning gas out the front; not a problem in my experience as I stay back from the dragon's breath anyway so as to not forge trim my beard, hair or eyebrows.

I'd suggest you try it and see what happens when you are ready for it.

Now if the blower is re-started and the forge is still hot it can pop as it self ignites.

[matt87]

I saw an article on a blown gas-fired glass-blowing kiln a little while ago where they spent quite some time discussing this and similar problems. I think they decided to use a solenoid-actuated gas control valve, so if the power went off so would the gas. They also had a therocouple so if the power came back on while the kiln was hot enough to ignite the gas, the gas and blower would come on, else not.

[Ice Czar]

Gas Control & Ignition

because a glass furnace get turned on for often months at a time
(my former neighbor's furnace only got turned off for rebuilds)
gas controls and saftey are a major concern

excerpt

From the point of view of the safety engineers, the following are desired
- The furnace must be clear of gas when ignition is attempted so that the volume of gas is not ignited and exploded and the burning occurs at the burners;
- The flame must ignite within an appropriate time after the gas is turned on and something must determine that there is a flame and not just a lot of heat.
- During operation there must be a sensing that gas is flowing, that air flow is adequate, and that temperatures are neither too high or too low.
- If the electricity fails, the system must shut down the flow of gas
- If the electricity comes back on, the system must do a start up procedure if safe to do so.
- If the gas fails, the system must detect that and do a safe shut down while setting an alarm.
----------------


* There must be a manual cutoff valve near the supply (tank or exit from the main) and if the supply line penetrates a wall, a shut off just inside the wall.
* There must be an electrically controlled cutoff valve that will automatically shut down on power failure.
* There must be an individual control valve for each furnace/gloryhole
* There must be a gas/air mixing method - which may just be a pipe injecting gas into the air stream
* There should be a pressure switch to detect that gas is available
* There should be an air flow detector to insure flow is occurring
* There must be a method of igniting the gas/air at the burner and/or a method of determining that the furnace is hot enough to ignite the gas/air mix
* There should be a method of detecting the flame - either a purple peeper that detects the UV in the flame or a flame detector that works because the flame is ionized and plain hot air is not.
* For temperature control, there should be a sensor in the chamber, usually inside a shield to avoid oxidation or physical damage.

A typical ignition sequence, whether controlled by a microcomputer or a person is this:
- Turn the air on or check that it is on and flowing
- Delay to allow the chamber to clear of any gas
- Check the gas pressure
- Turn on the gas
- Turn on the ignition system
- Delay and check that a flame has formed
-If not, try again a specific number of times, then shut down and sound alarm.
A typical control cycle would be
- If the flame has gone out - shut down and try to start ignition cycle
- If the temperature in the chamber is low, increase or turn on the gas flow, doing ignition if turned on.
- If the temperature in the chamber is high, decrease or turn off the gas flow.

IMO overkill for a forge
unless its unattended, for instance long annealing, case hardening ect
some sort of simple indicator the blower is running (which you also see in the flame front anyway) is all that paranoia dictates


BTW the RegO Products LP-Gas Service Manual link in tha article is dead, unless you know where to look ;)

[Jymm Hoffman]

Depending on the blower and orifice size you are using, but you should not need that much gas pressure. I use barbeque regulators that puts the pressure around 1/2 pound and an orifice of 1/8", and blowers from Kayne & Son that produce 36 ounces of pressure at 112 CFM. Blacksmiths Depot. I just spoke to them, this blower is currently out of stock, but on order. I also have a ball valve at the forge and the tank (which is outside of the shop and CO2 detector in the shop.