Stainless Steel pipe needs a good purge on inside of the root pass in order to keep it from getting crapped up.
Pipe welders called it “sugaring” and the technical term is oxidation or “granulation”.
Either way its ugly stuff. It not only inhibits flow of liquid, but it provides a place for bacteria to grow. For food grade piping, that is not cool.
For food grade and other sanitary stainless steel pipe welding applications, getting the root purged right is a must.
The inside of the weld must be silver and shiny or the inspector aint gonna let it ride. And even if there is no inspector when the weld is made and you get away with a sugared weld, later on when the swab tests are done and little critters are seen under a lab microscope, the company gets shut down and you don’t get any more work from them.
That should be incentive to do it right.
Seriously, when stainless steel pipe is purged right, it’s fun to weld and flows like honey.
If it’s not purged right, all the fun is gone and it’s like welding in a bowl of cornflakes.
I did another story recently about a contractor who was installing stainless steel pipe in a wash station for trucks that hauled chocolate milk and other food products. It falls right in line with this page about purging stainless pipe.
See the page about Bryan Milam and polished
stainless steel food grade welds here
His welds looked great and he got his purge using aluminum tape and a lot of hard work, but he definitely could have saved some time and aggravation if he had these slick little purge plugs.
OK, Let’s talk about the built in diffuser for a minute.
Why do you need a diffuser? Why can’t you just stick the argon hose in the end of the pipe and crank up the flow?
Here’s why… Remember that argon is heavier than air and fills a container much like water would. If you stuck a fire hose in a pipe, you never would get all the air bubbles out. But if you ran a soft stream of water from a garden hose, it would fill every nook and cranny and completely displace the air.
That’s a rough analogy but I think you get the point.
A diffuser actually helps to purge faster and at a lower flow rate.... Still Don’t believe it? It’s true.
When argon is pumped into a pipe too quickly, it can be very turbulent. A diffuser lets the argon gas do its job better by letting it flow more evenly while displacing all the oxygen inside the pipe and pushing it right out the vent hole.
and BTW, You always need a vent hole when purging stainless steel pipe. Those of us who have learned the hard way are embarrassed to say why.
Ok I’ll tell you… number one, if you don’t have a vent hole, you won’t get a perfect purge because all the oxygen cant escape.
number two, when you close up the weld, unless you have a vent hole, pressure will build and blow a hole…or at least cause suck back on the root. Anyway, back on task.
If your job calls for welding stainless steel pipe and you are currently using duct tape or purge paper, you need help.
John Mccarthy and Phillip Espinoza of FLOWDYNAMICS INC have 25 years combined ‘hands on’ work experience in the sanitary processing industry serving such entities as food, beverage, dairy, and pharmaceutical.
They don’t just sell purge equipment. They have used it.
Give these guys a call or go to their web site and check out their purge plugs.
Don’t forget to click on the dragon to see the slide show.
Or just call their Toll Free Number: 1-877-plug-060
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