The art of machining high density polyethylene pipe & Screen

There are material and production factors to consider when specifying and ordering HDPE pipe and slotted collection screen.

HDPE pipe expands and contracts, in both diameter and length, in response to temperature changes. In addition, the carbon black added tp protect against UV degradation absorbs heat and expands the pipe when it is exposed to sunlight.

Our BarbVark fittings are tested to assure fluid-tight performance at temperatures to 73 F. However, joints can loosen when outside temperatures approach 100 F because of uneven material expansion. For this reason, we recommend that piping be assembled and installed during cooler morning hours, particularly at trenchless drilling sites.

We machine pipe that has normally been stored outdoors. It may slightly bowed, out of round or otherwise deformed by factors beyound our control. the flexibility of HDPE pipe, so desirable in the field, makes control of tolerances difficult during slotting.

We do not use solvents, water or other liquids to lubricate our slotting blades. Our screen is delivered free of contaminants and machining residues. But dry slotting does heat the pipe, and when cutting arbors are lifted, slots tend to close up slightly, as the surrounding material cools. For example, a slot width of .128", when checked with a Starret Gauge, can measure between .115" and .125" depending upon pipe temperature at the time of measurement. Slot spacing may also vary, but to a lesser degree.

We slot using one, two, or three 6" arbors, with blades and spacers set to meet specifications. After each pass, arbors are raised and the pipe is advanced. Linear spacing between groupsof slots along the pipe can vary, depending upon arbor setup.

Studies indicate that slot length does not materially affect collapse strength of HDPE screen under heavy loads. Small variations in the slot dimensions have no bearing upon performance, so long as suffient open area has been built into the system.

We invite engineers, hydrologists and other ground water professionals to contact out customer service department for more information and answers to specific questions