Introduction: A Welder's Guide to HDPE Pipe Fusion
A guide primarily for men and women working with HDPE pipe, whether in landfill gas systems, domestic water supply or otherwise.
Step 1: General Information on HDPE Pipe Welding
High Density Polyethylene, or HDPE, pipe is a heavy-duty style piping used in physically demanding environments to transport things from water to natural gas on landfills. HDPE pipe is extremely durable, and relatively expensive compared to other pipe, such as PVC. HDPE pipe is generally used underground and with a high rate of flow of whatever is being transported. It would not typically be used in a small scale system, like a home or a school or other general building. Because of its value, it is very important to weld pipe together properly to get the most value out of a length of pipe. This guide will explain how to most efficiently weld HDPE pipe and get the most out of an investment and to have sturdy, solid fuses in the field.
Step 2: Pre-Weld- Safety Warnings
Before beginning any pipe fusions, keep in mind that potentially dangerous equipment will be used in this guide. Be sure that you know how to operate all equipment safely BEFORE attempting any fusions. Also remember that just because a piece of equipment is not in use does not mean that all dangers associated with that equipment are gone.
· DO NOT STICK YOUR FINGERS BETWEEN PIPES WHEN SLIDING.
· DO NOT FORGET TO LOCK SHAVER IN PLACE BEFORE USING. UNLOCKED SHAVERS WILL SPRING LOOSE OF THE PIT BULL AND CAN BE HAZARDOUS.
· DO NOT TOUCH THE SHAVER WHILE IN USE. SERIOUS INJURY MAY OCCUR, INCLUDING LOSS OF DIGITS.
· ONLY TOUCH HOT PLATE BY THE HANDLE. SERIOUS INJURY MAY OCCUR FROM DIRECT CONTACT.
· Some equipment requires the use of power cords with relatively long length. Keeping a clean working environment includes keeping things out of the way and tied up as much as possible. Loose electric cords may lead to tripping and falling, which is already unsafe, even more so when dealing with 350° hot plates and pipe shavers.
Step 3: Pre-Weld- Preparation Directions
Before beginning a weld, make sure all of the material and equipment is laid out and easily visible.
General equipment for a generic weld includes
· McElroy Pit Bull
· Hot Plate
· Pipe shaver
· Electricity source
· Time keeping device
NOTE: Before beginning the weld, plug in the hot plate, and have it turned onto 350° F. This is so that no waiting is involved when the hot plate is needed later. WARNING: Do NOT touch the hot plate face.
General materials for a generic pipe weld include
· HDPE pipe
· HDPE pipe/fittings of equal diameter of first pipe
Once all of these things are together, the welding process can begin
Step 4: Welding- General Fusion Directions
1. Place one pipe in the McElroy Pit Bull and fasten it down tightly. One turn after the pipe is clamped is tight enough. Make sure the pipe is not angled in any direction when it is being placed into the Pit Bull.
2. A) Place another pipe of equal diameter into the other side of the McElroy Pit Bull. Fasten the pipe so that it is tight enough to slide with the sliding tool on the Pit Bull.
B) Place an HDPE pipe fitting of equal diameter into the other side of the McElroy Pit Bull. Fasten the fitting so that it is tight enough to slide with the sliding tool on the Pit Bull.
3. Slide the pipes/pipe and pipe fitting together to where they look attached. Look at the connection from both sides and from the top to see if one or both pipes needs to be adjusted before the weld.
4. When the pipes look flushed together, slide them back apart and attach the pipe shaver to the McElroy Pit Bull, with each arm of the shaver fitting neatly onto the bars of the Pit Bull. When the second arm is attached, it will lock into place automatically.
5. When the pipe shaver is locked into place, place it in the middle of the two pipes, not touching either of them. At this point, turn the shaver on and slide the pipes into the pipe shaver. Small strands of pipe will begin to appear from the shaver, but continue shaving until very long strands appear, about the circumference of the pipe. This insures that the each side has been shaved cleanly and flat.
6. When longer strands appear, KEEP THE SHAVER TURNED ON and slide the pipes away from the shaver. When the shaver is no longer in contact with the pipe, the shaver may be turned off. THE PRESSURE OF THE PIPES PUSHING INTO THE SHAVER IS WHAT CREATES CLEAN SHAVES.
7. After the pipes have been shaved, slide them flush together again to make sure the shaver has done its job.
8. If the pipes are indeed flush, slide them apart again. NOTE: This step must be done quickly to ensure efficiency and quality. Remove the hot plate from the glove and place it where the shaver was on the McElroy Pit Bull. Slide the pipes so that they are flush to the hot plate, lock the Pit Bull into place, and wait 2:00 for pipes between 1" and 4", which encompasses all sizes that fit into a generic McElroy Pit Bull.
9. Around 1:30, a small bead will begin to appear from the pipe at the point of contact with the hot plate. NOTE: This step must be done quickly to ensure efficiency and quality. At 2:00, unlock the Pit Bull, remove the hot plate, and slide the pipes/ pipe and fitting together and press so that one bead rolls onto the pipe from each side, resembling a pair of lips. Lock the pipe into place using the same feature as the hot plate step and wait 3:00 for the pipe to cool down and fuse together.
10. After 3:00, unlock the Pit Bull and remove the fused pipe (Or the Pit Bull, in some cases!) The weld has been completed.
Step 5: Welding- Extensive Welds
Some welds may have to be done in the field. The same welding procedures will be generally used, but there will be some tweaks.
In- Ground Welds
In-ground welds are between two pipes that are already locked into place, or dug into the ground. They usually occur when another branch needs to be added or when a stub-up needs to be installed. In the scenario of a stub up, this is what generally happens:
1. THIS IS THE MOST IMPORTANT PART OF THIS SECTION. Before an in-ground weld is done, THE SYSTEM MUST BE SHUT OFF. FUSING ON ACTIVE PIPES CAN BE DANGEROUS, EVEN FATAL.
2. After the system is shut off, the pressure from the pipes must be released through a stub-up valve.
3. To install a stub up, a T shaped fitting is used, just as in the figure below.
4. The most difficult part of an in-ground weld is cutting the pipe to the proper length. Generally, in-ground welds try to take off as little pipe as possible, opting instead to have some slack instead of the possibility of having the pipe being too short.
5. After the pipe is cut, the T fitting and one of the cut ends are placed into the McElroy Pit Bull and fused normally, because the T fitting can be adjusted to the user's needs.
6. When fusing the loose ends together, the Pit Bull may be contorted in different angles to get the pipe to fit correctly. As long as the two ends are flush together before a hot plate is added and the ends are stuck together, the weld should come out perfectly fine.
Step 6: Post Weld- Equipment and Material Preservation and Protection
· DO NOT allow pipe to be in contact with hot plate beyond 2:00. Faulty welds may occur, and hot plate may be damaged.
· If pipes are not flush together before welding, the welded pipe may fuse at a cockeyed angle, which is less secure than a regular straight weld.
· When finished using hot plate, place back into mitten, metal on metal on the side to prevent direct contact between hot plate and mitten.
· After using hot plate and shaver, neatly wrap the electric cords and drape them from the hangers. DO NOT have the cords pulled at an awkward angle, as leaving them for a long period time can lead to equipment damage.