By Tim Daly
Since the dawn of the industrial age, pipefitters and welders have been closely linked together in both the building and metal trades. The fact is, as much as plastic pipe is becoming more common in the plumbing trade, most pipe is metal, and where there is steel there is welding. So with that in mind, here are ten things you need to know in order to achieve quality welded joints.
In order to get good adherence in the mating surfaces—as well as the welding medium you’ve got to have nice, clean surfaces. If you are having black iron or steel pipe welded, use a wire brush, wire wheel and/or emery cloth to remove rust and oxidation. Steel tends to rust quickly, so you will want to clean your joints as close to the time you’re going to weld as possible.
If you’re welding copper nickel pipe and are using a consumable ring, or a backing ring, do not expose the ring to the atmosphere any longer than necessary. The ring will become discolored, and the welder may refuse to weld the joint. Use lint free rags when cleaning such joints
Safety and Fire Watch
As in all professions—and life itself—safety is priority one for the pipefitter and welder. Welding creates extreme breathing and eye hazards. When it comes time to buy a welding mask, do not go for a cheap model. Welding masks have improved in both safety aspects, as well as quality aspects, in recent years.
They now have shields that will adjust the eye tint so that you can keep the same mask on for welding or grinding, and many masks are built to accommodate hard hats and respirators. It is important that you are aware of any and all breathing hazards associated with the materials that you are welding on, as well as the materials you are welding with.
It is also imperative to maintain a safe working environment for other people in and around your work area. It is the welder’s job to ensure that all required safety barriers and curtains, as well as warning signs, are erected before the welding or grinding begins.
In many settings you will need a hot work permit from the local fire department, or shipboard watch station, before you are allowed any hot work.
Competent, trained, and certified fire watches with properly working fire extinguishers, are required for any welding operations, both in shop settings or at a remote job site.
Generally speaking, the best welded joints are the best fit-up joints. You need to take enough time during fit-up to ensure that butt weld surfaces are straight and tight, and that socket joints are nearly bottomed out (in many instances a print, or engineering memo, or diagram will tell you how much clearance you need) and that the pipe end is straight. Occasionally you may require a funky angle on your fitting, and in these cases especially, you need to ensure a good fit-up.
End prepping goes in conjunction with cleanliness and fit-up. If your joints are to be butt-welded, you will need a taper. These are usually “J” bevels or “V” bevels. If you are working on a high pressure system, or with pipes requiring the consumable ring, you will have blue prints or strict engineering guidelines telling you what sort of bevel to have, what angle to have, and any tolerances referring to the bevel and also the fit-up.
You will probably have to “sell the joint” to an inspector before the welding commences, and if you have a consumable ring that has been sitting out too long and becomes discolored, the welder may refuse to weld and you’ll be starting from scratch to get the fit-up a second time.
Support Your Pipe and Joints
You may need to add support for your pipe and joints, or build—what is known as a bird cage—around your joint to hold it together through the tacking phase of the weld. If you cannot achieve this with mechanical means, then welding strong backs to your pipe may be necessary. When such cases involve inspectors, you may be required to remove the bird cage, or strong backs, after tacking and before the actual welding takes place.
Bolt Arrangements for Flanges and Slip Flanges
Obviously, the most important part of welded flanges is ensuring that the bolt holes on both flanges line up with one another. If at all possible, line your flanges up with the bolts installed—no gaskets during the welding process please—to ensure proper fit-up.
Two important terms to know here are, One Bolt Up and Two Bolts Up. This refers to the alignment of the bolt holes in regards to a horizontal pipe. A flange one bolt up will have one of its bolt holes at the exact top of the flange circle, and a two bolts up flange will have two bolts sitting exactly the same distance above the center line of the flange.
Hangers and Supports
Pipe hangers are generally stick welded to permanent foundations within the building or vessel you are working in. It is important that you, as the welder, are aware of what the particular foundation you are going to use is made of.
If you are working on a system that is being built with sound or vibration dampening in mind, you may have some strict guidelines to follow for the hangers, as well as the pipe. Your job plan will have those guidelines spelled out for you.
Different types of welding
The welding industry is forever evolving to keep up with the changing technology of the systems that require the welding. It is quite common these days for welding shops to be set up with computers and robots doing the welding that can be done off site.
Fortunately, welding done in the trenches or the bilges is still being performed by quality tradesmen. The skills needed for stick welding, arc welding, tig welding, mig welding and the like are still abundant, and the age of computers and robots should not scare people away from this vital trade.
All welding on high temperature or high pressure applications needs to be certified. Sometimes maintenance managers like to brush this under the rug when they can get away with it.
When a boiler inspector is called upon to inspect work done on a boiler, every joint must have the proper stamps indicating the welder was certified, knew what procedures needed to be followed, and did indeed follow them. The inspector may actually require to see the welder and his certifications in person.
. Welder Certifications
Many tradesmen—especially pipefitters—familiarize themselves with basic welding. It’s only natural, and any extra skill learned makes the tradesman more valuable to a company; and if he’s proficient enough, he can command more money for his services.
A pipe welder, or boiler equipment welder, has been trained and certified for specialized welding operations. Such skills allow a pipe welder to be among the highest paid of all tradesmen. Once you have earned these certifications, it is important to keep up with future training and refresher courses, so you can maintain them.
Plastic is taking a hard run at replacing metal in the plumbing world, and computers and robots are inching their way into many trades including welding, but as long as there are metal piping systems and structures, there will be welding jobs that need to get done. Educated and highly skilled pipefitters and welders will continue to stay in demand, and command top dollar from those in need of their services.