LIGHTING O2 AND PROPYLENE

By Lawrence (*****)

Date 03-28-2012 13:39 Edited 03-28-2012 13:59

Welcome to the forum Metal Smith!

Who, besides you recommends lighting oxygen and fuel (propylene) together?

I'd like to know myself as I've never been instructed in the lighting sequence you mention.

There are several different kinds of fuel gas hoses... Some can carry Acetylene and the alternative gasses.. Some cannot.
Your hose should be marked. You need to check those markings and make your decision based on the standard.

See this

http://www.crosshose.com/Tech_Bulletin_Welding_Hose-What_hose_is_needed_42904.pdf

Edit: The potential problem I see in lighting fuel and gas together is that it would be very difficult for the operator to sense the a correct proportion of each gas before the torch is lighted.

Edit edit: I stand corrected (learn something every day)]

Jody Collier from Welding Tips and Tricks (Welding instructor for Delta Airlines) is somebody I hold in highest regard and explains about lighting propylene oxy-fuel torches and provides good instruction.
http://www.weldingtipsandtricks.com/oxy-fuel-cutting.html

'

By METALSMITH37 Date 03-28-2012 14:00

Thank you , well ive read this on several web sites as maurfacturers recomendation to light the torch this way , but i just dont know why . I personaly just assumed this as ive worked with other gases such as Chemtane that also recomend lighting the torch this way .

By Lawrence (*****)

Date 03-28-2012 14:04

It appears you are right!

Thanks for the post... It made me look further into it myself and my students will benefit too :)

By Northweldor (***)

Date 03-28-2012 14:45

I would think it might be because of the higher flow rate and slower burning rate of the propylene makes it desirable to add some oxygen to the mix in order to get quicker lighting.

By METALSMITH37 Date 03-28-2012 14:03

Once i light the o2 then fuel I walk them upo to the desired neutral flame .

By waccobird (****)

Date 03-28-2012 14:38

METALSMITH37

I was going to say Shouldn't you research this so that you are assured you are instructing the kiddo's correctly?

But I see you did some

But I believe it is mainly to contain the flame so it doesn't blow out in the wind.

Just experience and my ¢¢'s

Marshall

By Tommyjoking (****)

Date 03-30-2012 01:36

I had issues lighting propelyne without a touch of oxygen. Even with an open flame. I thought that was how you were suppose to do it.

By Sourdough (****)

Date 03-30-2012 03:30

I have lit my gas first then added o2 for so many years, I wouldn't ever change it. I know exactly what kind of juice I'm dealing with by the gas flame and smoke, before I add o2.

Lighting them both seems to me, like filling a bathtub before testing the water with your hand........but of course, I do everything backward from the norm. :lol:

By jpill

Date 03-30-2012 13:06

That would be correct Waccobird the O2 is to keep the flame from blowing out upon lighting.

Metalsmith37 Another method is to lay the tip at about a 20 deg angle on a piece of plate, turn on propylene, strike torch, add a small amount of O2, then lift the tip and alternately adjust gases until torch is set. This does the same thing to keep the torch from blowing out when O2 is initially added.

Now if you can come up with a way to convince HS kids that propylene actually cuts better and cleaner than Acetylene....IF....you take the time to properly set the torch let me know!!!

By eekpod

Date 03-30-2012 13:26

I was taught to light both acetylene and O2 because when you light just the acetylene the black soot makes a mess. When you light both you don't get that soot.
Now the propylene I have never heard of never mind used, so that may or may not be a reason.

By Lawrence (*****)

Date 03-30-2012 13:29

Eeeeek!

Propylene became popular a few years ago when MAPP gas became unavailable. Operationally Propylene and Mapp are very similar.

By jpill

Date 03-30-2012 14:09

Not only that Lawrence, but the multitude of different propylene based gases are staggering. In my area alone we have Chemtane (Praxair), Pro-Flame (Matheson ETOX), and a brand I am not familiar with from Red Ball; all three have additatives to make it burn hotter than straight propylene (What MAPP was originally designed for). It seems that every LWS has a different propylene based cutting fuel now to replace MAPP, and all have a different brand name.

By DaveBoyer (*****)

Date 03-31-2012 01:38

Chemtane is propane based, don't know about the others. What are You using, and how do You like it ? What is Your preference ?

By jpill

Date 04-02-2012 13:04

We are currently using Pro-Flame it is a Propylene/Propane mix with some other "proprietary" chemicals added to make it hotter than either straight propylene or propane. Personally I like it, with a torch set correctly, a clean tip, and a steady hand it can make cuts that rival machine cuts with virtually no slag. My students complain about it though they don't understand no matter how much you explain lower temp means more preheat and a slower cut. They want it to cut as fast as acetylene.

By DaveBoyer (*****)

Date 04-03-2012 02:02

I saw a demonstration with propalene. The guy made amazing cuts, I should have tried it to see if I could do any better than with acetylene. One of My friends gave it a try, He liked it, but can't get it on St Croix, where He lives.

By Tommyjoking (****)

Date 04-03-2012 07:30

Dave I have no idea of the "brand" but I was sold on propylene in the demo.....I cut with it and it was far cleaner then acet/oxy. The shop that was buying it did a lot of heating.....there monthly bill was cut significantly but oxy went up a good bit. Overall they saved money but I reckon they could have done a lot with PG/LG and done the same. As far as cutting goes it is less grinding.

By waccobird (****)

Date 03-30-2012 15:16

jpill

About 8 years ago our gas rep brought in a man probably 65-70 who told me that and I scoffed.

He said do you have some 3/8 plate that is scrap that I can demonstrate with.

I found a piece of plat bar 3/8"x 8"x@ 3' and he proceeded to show me and make a believer of me.

With a bit more oxygen in the flame than I would of had he took and started making a house key about 5" long and 3/4" wide.
when he got to the kerf where he began the piece fell to the floor and there was no slag on the steel.

As I said he made a believer of me and we have been running it here in the shop ever since.

I also place my torch as you stated in the web to contain the flame in case I don't have enough O2 to begin with as we have an open shop here in Florida and pray for breezes.

Good Luck

Marshall

By Northweldor (***)

Date 03-30-2012 18:33

Metalmaster37

The reason why the lighting procedure you mentioned is recommended by suppliers is that propylene requires about 4.5 x the volume of oxygen required by acetylene for efficient combustion, and when used at high velocities as in cutting or heating, the slower rate of flame propagation (about 1/2 that of acetylene) requires that some oxygen be added to increase this speed to prevent the flame from blowing away from the tip, or failing to ignite. (This is essentially what I wrote above but more specific).

Btw, since you are teaching, you might want to look at Chapter 29, of Larry Jeffus' excellent on line text where he provides many diagrams and tests of flame behaviour that your students can perform.

http://books.google.ca/books?id=iXAmL8HEMfkC&pg=PA736&lpg=PA736&dq=Oxy-Propylene+torch+Flame+propagation&source=bl&ots=J-x9dX0z0W&sig=P2-JyMxwEGhbxTH3dEyxAiwCuaU&hl=en&sa=X&ei=c8N1T5qvFqTaiQK4saCnDg&sqi=2&ved=0CEAQ6AEwBQ#v=onepage&q=Oxy-Propylene%20torch%20Flame%20propagation&f=false