:::RHMT::: Real Home Made Turbo

General Category => Fabrication => Topic started by: Logan76 on April 16, 2009, 02:06:59 AM

Title: Backpurging
Post by: Logan76 on April 16, 2009, 02:06:59 AM
Is there anything beneficial to backpurging when you Mig? or is that only for Tig? And while I've got your attention can anyone reccomend a good auto darkening welding helmet? I'm thinking of miller.
Title: Re: Backpurging
Post by: slappynuts on April 16, 2009, 02:59:20 AM
Is there anything beneficial to backpurging when you Mig? or is that only for Tig? And while I've got your attention can anyone reccomend a good auto darkening welding helmet? I'm thinking of miller.

Ok so the question all comes back to what you are doing and what material you are using. If you have any more questions you should include what equipment you have and what you are trying to do.
Title: Re: Backpurging
Post by: t_cel_t on April 16, 2009, 03:41:50 AM
you might get a better weld with mig if your are actually getting full penetration, it couldnt hurt.
Title: Re: Backpurging
Post by: Logan76 on April 16, 2009, 08:15:48 AM
Its just a hypothetical question, pretty much im a big noob. The purpose of backpurging is to keep the inside of your weld clean correct? So say im welding a joint on two stainless pipes soon to become intercooler pipes, I want the inside of my pipe to look perfect and be smooth as to I cannot reach it with a grinder to clean it up. That would be the correct situation for backpurging? Maybe it was just a dumb question.
Title: Re: Backpurging
Post by: dvst8r on April 16, 2009, 10:13:10 AM
An easy way to visualize the need for back purging.

We have all seen welds where someone forgot to turn on the gas, and the weld just shits on its self. We some materials: SS, Ti, ect... Are sensitive enough to atmosphere that if they don't have shielding on both sides of the weld, and in some cases while they cool. They will shit on themselves where they are not covered.

NOTE: When you don't back purge a weld, it does not physically look the same as when you forget to turn on the gas on a mig when welding mild steel, I just used that metaphor as most people have seen that form of fail.


Title: Re: Backpurging
Post by: slappynuts on April 16, 2009, 10:17:19 AM
If your going to mig you should be using mild steel. This greatly reduces the need to backpurge.

I use a speedglass helmet. Its cheaper than the miller and very nice unit.
Title: Re: Backpurging
Post by: dvst8r on April 16, 2009, 10:24:20 AM
If your going to mig you should be using mild steel. This greatly reduces the need to backpurge.

I use a speedglass helmet. Its cheaper than the miller and very nice unit.

You don't ever need to back purge mild steel.
Title: Re: Backpurging
Post by: turbob16hatch on April 16, 2009, 07:18:43 PM
You don't ever need to back purge mild steel.

hey hold on there chief.....

do you even know what back purging does?



Title: Re: Backpurging
Post by: dvst8r on April 16, 2009, 08:59:16 PM
You don't ever need to back purge mild steel.

hey hold on there chief.....

do you even know what back purging does?


Yes it applies shielding gas to the back side of the weld.

The only couple places I can think where back purging would be used with mild steel, is in HIGH pressure steam, or natural gas lines. Not rHMT sort of welding.
Title: Re: Backpurging
Post by: Hotrodlincoln on April 16, 2009, 09:02:59 PM
You don't ever need to back purge mild steel.

hey hold on there chief.....

do you even know what back purging does?


Yes it applies shielding gas to the back side of the weld.

The only couple places I can think where back purging would be used with mild steel, is in HIGH pressure steam, or natural gas lines. Not rHMT sort of welding.
The pipe line welders I know All tig weld and they are welding stainless so they have to backpurge
Title: Re: Backpurging
Post by: dvst8r on April 16, 2009, 09:35:35 PM
You don't ever need to back purge mild steel.

hey hold on there chief.....

do you even know what back purging does?


Yes it applies shielding gas to the back side of the weld.

The only couple places I can think where back purging would be used with mild steel, is in HIGH pressure steam, or natural gas lines. Not rHMT sort of welding.
The pipe line welders I know All tig weld and they are welding stainless so they have to backpurge

Most of the pipe welders I know, and used to work with, weld in the bush in Alaska, northern BC, northern AB, and northern SK. They weld either Oil pipeline or natural gas. All mild, vast majority welded with stick.
Title: Re: Backpurging
Post by: Logan76 on April 16, 2009, 09:55:36 PM
I'm an industrial pump mechanic, and all the pipe work we do, which isnt much but our welder welds alot of impellers, pump cases, etc and its mostly stick welding also. Seems like stick welding is super old school, but still relied on heavily in the industrial application.
Title: Re: Backpurging
Post by: dvst8r on April 16, 2009, 11:14:09 PM
That is because you can do it anywhere, wind, rain (a little sketch in the rain) outside in, any position, and still get an x-ray quality weld, for pressure vessels. Stick welding makes the world go round.