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Gas Nozzle Pressures

Friday, 11th December 2020
Graham (Tech Advisor)
The Welders Warehouse Online Shop

The correct Gas Pressures are important. Incorrect pressure can increase the risk of Flashback and make Flame Adjustment difficult.

The following Guides should help you

Lightweight & Heavy Duty Swagged Oxy/Acet Gas Welding Nozzles

Lightweight include DH type Oxy Acetylene Nozzles (not pictured)

Heavy Duty includes type 3, 4 & 5 Torches

Nozzle Size – Gas Nozzle Pressures

  • No1 – Metal Thickness = 1.0mm – Oxy/Acet Pressures = 0.15bar each
  • No3 – Metal Thickness = 2.0mm – Oxy/Acet Pressures = 0.15bar each
  • No5 – Metal Thickness = 2.5mm – Oxy/Acet Pressures = 0.15bar each
  • No7 – Metal Thickness = 3.2mm – Oxy/Acet Pressures = 0.15bar each
  • No10 – Metal Thickness = 4.0mm – Oxy/Acet Pressures = 0.20bar each
  • No13 – Metal Thickness = 5.0mm – Oxy/Acet Pressures = 0.30bar each
  • No18 – Metal Thickness = 6.5mm – Oxy/Acet Pressures = 0.40bar each

Multi-Jet Oxy Propane/Propylene Nozzles

Nozzle Size – Gas Nozzle Pressures

  • No1 – Metal Thickness = 1.0mm – Oxy/Prop Pressures = 0.20bar each
  • No3 – Metal Thickness = 2.0mm – Oxy/Prop Pressures = 0.20bar each
  • No5 – Metal Thickness = 3.0mm – Oxy/Prop Pressures = 0.25bar each
  • No7 – Metal Thickness = 4.0mm – Oxy/Prop Pressures = 0.25bar each

AHT Heating Nozzles

Nozzle Size – Gas Nozzle Pressures

  • AHT25 Oxy/Fuel Pressures = 0.30bar each
  • AHT50 Oxy/Fuel Pressures = 0.40bar each
  • AHT100 Oxy/Fuel Pressures = 0.70bar each

Oxy/Propane Super Heating Nozzles

Nozzle Size – Gas Nozzle Pressures

  • 1H Oxy Pressure = 0.7-2.0bar + Propane Pressure = 0.15-0.5bar
  • 2H Oxy Pressure = 0.7-2.0bar + Propane Pressure = 0.15-0.5bar
  • 3H Oxy Pressure = 1.8-5.0bar + Propane Pressure = 0.3-1.1bar
  • 4H Oxy Pressure = 1.8-5.0bar + Propane Pressure = 0.30-1.1bar

Oxy/Acetylene (ANM) Cutting Nozzles

Nozzle Size – Gas Nozzle Pressures

  • 1/32″ Cuts 3-6mm Steel – Pressures = Oxy 1.5bar / Acet 0.15bar
  • 3/64″ Cuts 5-12mm Steel – Pressures = Oxy 2.0bar / Acet 0.15bar
  • 1/16″ Cuts 10-75mm Steel – Pressures = Oxy 2.5-3.5bar / Acet 0.20bar
  • 5/64″ Cuts 70-100mm Steel – Pressures = Oxy 3.0bar / Acet 0.30bar
  • 3/32″ Cuts 90-150mm Steel – Pressures = Oxy 3.0bar / Acet 0.30bar
  • 1/8″ Cuts 150-300mm Steel – Pressures = Oxy 4.5bar / Acet 0.35bar

Oxy/Propane (PNM) Cutting Nozzles

Nozzle Size – Gas Nozzle Pressures

  • 1/32″ Cuts 3-6mm Steel – Pressures = Oxy 1.5bar / Prop 0.15bar
  • 3/64″ Cuts 5-12mm Steel – Pressures = Oxy 2.5bar / Prop 0.15bar
  • 1/16″ Cuts 10-75mm Steel – Pressures = Oxy 3.0-3.5bar / Prop 0.20-0.35bar
  • 5/64″ Cuts 70-100mm Steel – Pressures = Oxy 3.5bar / Prop 0.4bar
  • 3/32″ Cuts 90-150mm Steel – Pressures = Oxy 4.0bar / Prop 0.4bar
  • 1/8″ Cuts 150-300mm Steel – Pressures = Oxy 5.5bar / Prop 0.6bar

I hope you found this blog article about Gas Pressures useful.

Please let me know what you thought by leaving a comment.  

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  1. John Macdiarmid says:

    Hi is there a torch that can be used with propane and compressed air for small brazing work?

    1. Graham says:

      Hi John
      I regret that’s not somethi9ng we offer and I don’t know of a Torch I can suggest/recommend. I wouldn’t have thought Compressed air would give you the precision flame that Oxygen produces and it certainly won’t produce the heat.
      Sorry I couldn’t help further.
      Cheers Graham

  2. Dave says:

    Hi, I’ve recently brought the heavy duty heating/multi jet brazing torch. I’ve decided to switch the flashback arrestors and have decided to go for torch mounted. Would it be much of a problem having reg mounted as well as? I read about how that can cause problems with restricting flow? Just thought have a set each end would be a good idea. Cheers

    1. Graham says:

      Hi Dave
      UK Hoses have a Check Valve at the Torch End (built into the Hose Fitting).
      These Check Valves are your first line of defence against Flash Backs.
      Flash Arrestors on the Regulators are the fallback in case a Flash Back gets passed the Check Valve.
      In 30 years of selling Flash Arrestors, I’ve only ever sold ONE to a customer who had a Flash Back reach the Arrestor, so Check Valves do a good job!
      American systems do not have Check Valves, so they fit Flash Arrestors to the Torch to protect the hoses from Flash Back damage.
      The downside to Flash Arrestors on the Torch is they add quite a bit of weight and bulk.
      To get to your question, I would not have Flash Arrestors on the Torch and Regulator. As you almost certainly have Check Valves on your Hoses, this would be 3 devices in the system, so flow issues become a very real possibility.
      Hope that all helps
      Regards Graham

  3. Nigel G says:

    I note your recommendation of 0.20 bar or 0.25 bar oxygen and gas pressures (depending on size) for multijet nozzles. However, how do you set this with any accuracy? For example the outlet pressure gauge on your propane regulator has a full scale deflection of 6 bar, so trying to set 0.2bar is hardly going to move the needle and isn’t going to be very accurate. I can’t locate any propane regulators with pressure gauges that would allow 0.20 bar to be set accurately.

    1. Graham says:

      Hi Nigel
      Our Propane Regulators have an output range of 0-4 bar. Outlet pressure gauges nearly always show 2 bar above the max of the Regulator for technical reasons.
      0.25 bar is the first black mark on the outlet pressure scale of our Propane Regulator. I set this pressure regularly when I do brazing with Oxygen + Propane, using a Muti-Jet Torch and have not had any issues with pressure accuracy or flame stability.
      The challenge for Regulator manufacturers is that Propane is regularly used for Cutting and Heating. These applications can require pressure of 2-4 bar, so it is important that Propane Regulators can handle this.
      I hope that helps.
      Cheers Graham

  4. Stephen Whymant says:

    Many thanks Graham. It sounds as if I will need two torches. The propane regulator I have been sold is a bog standard caravan type one. Is this suitable or do I need a regulator with gauges so that I can alter the pressure to suit the tip in use? Yours, Steve.

    1. Graham says:

      I wouldn’t use a Regulator designed for Caravan use!
      Pressure adjustment and at least a Delivery Pressure Gauge are pretty fundamental, have a look at our Propane Regulator. For safety, you should also use a Flash Arrestor!
      If you need any more detailed advice, give me a call, the numbers on our website.
      Hope I’ve helped, Graham

  5. Stephen Whymant says:

    Hi. I’ve been sold AFN nozzles for cutting with propane. Is that correct? I can’t get them to light. I can’t find information on the propane pressure for these nozzles. I purchased a light duty cutting attachment but can’t stop flame leakage around the nozzle holding nut. I’m new to gas cutting and primarily want to do some brazing as well. Thanks, Steve.

    1. Graham says:

      Hi Stephen
      You can get away with using an AFN Cutting Nozzle with Oxy/Propane, but it’s not ideal. There is not a readily available Nozzle on the market for Lightweight Torches I’m afraid, so you will either need to do the best you can, or buy a Heavy Duty Torch and Cutting Attachment that ARE designed for Oxy/Propane.
      The flame leakage around the Head Nut sound like a poor sealing surface on either the Nozzle or the Cutting Attachment. Contact your supplier for advice on this and pressures.
      Hope that helps (at least a bit!)
      Cheers Graham

  6. Robin Wills says:

    Hi Graham
    Im just changing to Oxy-Propylene. Can I use my BOC saffire torch and existing nozzles for brazing and bronze welding? If so do I use a different pressure?

    1. Graham says:

      Hi Robin
      Short answer is Yes you can, slightly longer answer is Acetylene Nozzles are not very good with Propylene!
      We offer a Propane Neck and Propane Nozzles that would fit your Saffire Torch. You would need to check if your Saffire is a Lightweight, or Type 3. If it’s type 3 you will also need the Neck Adaptor. If your not sure, give me a call.
      IMPORTANT, make sure you change your Regulator and Hose to a Propane type, DO NOT use Acetylene equipment with Propylene!!! If your Flash Arrestor is labelled “Acetylene” you will need to change that as well, if it’s labelled “Fuel” it will be OK.
      If you haven’t already read it, you might find my blog article Can I Use Propane or Propylene Instead of Acetylene useful
      Hope that helps
      Cheers Graham

  7. Brian says:

    Thank you for your reply. Very clear and exactly the information I requested. It’s so important to handle this equipment safely and to be sure of the correct procedures. The additional link to the setting up a gas kit was spot on. Once again many thanks.

    1. Graham says:

      Thanks Brian, glad to be of help, Graham

  8. brian says:

    Having not used oxy/propane before (only oxy/acetylene) can you explain the lighting up and setting the flame procedure please. I have just purchased your GK25 Torch and Reg set along with GHD08 Super Heater and want to get this right (I understand it may be different to Oxy/Acetylene)

    1. Graham says:

      Hi Brian
      Lighting and shutting down procedure is the same as for Oxygen + Acetylene.
      Light the Propane first (ensure there is no visible gap between the end of the Nozzle and the Flame or the flame will blow out when you turn on the Oxygen).
      Slowly turn on the Oxygen until you get the desired flame.

      You may notice that the central “Cone Flame(s)” is longer than with Acetylene, this is quite normal and is because Propane is slower burning than Acetylene.

      I’ve written a blog article on setting up a Gas Kit that includes lighting etc (it does cover Propane as well).

      If you need any further help, please call (numbers are on our main website).
      Hope I’ve helped
      Kind Regards

  9. Peter Barnsby says:

    Hi what pressure would you recommend for the oxy3000 kit to weld lead, the same as above ? Thanks

    1. Graham says:

      Hi Peter
      Thanks for the question. Outlet Pressure for both Oxygen and Fuel gas should be no higher than 0.25bar.

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