View Full Version : Equation for welding pipe
10-12-2009, 10:43 AM
I've got a large job including pipes sizing from 76mm x14mm to 273mm x 48mm. There are several hundered pipes and several thousand welds to be accomplished. Now for the fun part. I need to come up with an equation or table to estimate the amount of time that each weld takes. Has anyone had to do this before? Each pipe will be have a TIG root pass and filled and capped with stick.
Any suggestions and thoughts would be great.
10-12-2009, 12:57 PM
It needs way more info.
Time to get a stop watch out and go to the shop. That will give your welding time. Add a move to next weld time. etc. It could be double, triple or more the welding time depending on the job. Add probably 1 hour per day setup/cleanup. Add 10% for interruptions of work flow, Then add 20%, because nothing ever happens as it should. :laugh::laugh:
How I estimate here is to take your pounds per hour deposited for the process (a number of sources for this, but it depends on electrode type, diameter, etc), factor in your approximate efficiency (also available from a number of sources), and then multiply by your cross sectional area of the weld joint and circumference of the pipe. You're basically taking the amount of weld metal needed to complete the joint, and applying an efficiency factor to it.
This will get you in the ballpark, though sample welding data is often more accurate. Of course, this doesn't factor in fit up time, preheat, weld prep, etc.
10-12-2009, 04:45 PM
Thanks for the suggestions. I've got some soft numbers that were taken from previous projects, but they aren't very accurate when it gets out to some of the bigger pipe. These figures show welding schedule 160 pipe with 3/32 rod with a TIG root pass that the example did about an inch of pipe an hour.
Ex. 2" sch. 160 = 2 hours per weld joint + 1 hour to fit pipes.
10-15-2009, 02:16 PM
i found a website that offers a more defined equation with pictures. Just wanted to share this with the group in case anyone ever needs to quote a job.
the welding institute offeres a logical calculatiog method for weld volume and weight.
That's basically what I was describing in taking the area to determine the lbs/hr deposited. I usually use CAD to model the joint configuration and let it calculate the area for me. Then you factor in deposition efficiency of both the electrodes and the workers. With SMAW, 35% arc time vs hours worked is a rule of thumb, as is a deposition efficiency of 65% or so.
10-17-2009, 04:04 PM
Most basic arc welding courses/classes will teach you estimating of welding costs. It's very good stuff to know and understand.
10-17-2009, 04:11 PM
How much will you pay me to estimate the job for you?
11-16-2009, 09:31 AM
I've put together a excell spread sheet that allows easy calculation of weld volume by just entering the pipe diameter, wall thickness, gap, and angles used on the weld. This is the easiest and most accurate way for me to get an estimate on how much filler is used. Thanks for the suggestions again.
Just remember, larger wall thickness pipes will often use a 20/10, 37/10, or j prep, at which point it becomes a lot more complicated than just your standard bevels.
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