Thermoplastic piping is a general term applied to a variety of different plastics. A user of plastic piping should select the kind of plastic best suited for his use.
Special care must be used to apply proper engineering, design and installation procedures.
GF Harvel recommends against the use of its thermoplastic piping systems for transport or storage of compressed air or gases. Trapped air must be removed from liquid piping systems so that no air remains locked in the system when pressure is applied to the liquid. Excessive surge pressure must be avoided. Surge pressure can develop if liquid movement through the pipe is near maximum velocities and valves are closed abruptly. Maximum velocity is generally considered to be five feet per second.
Failures can occur at the joints connecting the pipe and the fittings. For example, threaded joints have a diminished wall thickness because of the cut of the thread into the wall. Also, improperly cemented joints will leave the strength of the joint impaired.
Temperature extremes, both hot and cold or changes in temperature can result in failures of plastic pipe in the following cases:
- Breakage or other damage on the job site in cold weather can be caused by impact with tools, vehicles or rocks.
- Heat of solution of chemicals or heat from other sources can cause failure because the piping systems will be distorted.
- Wide variations in temperature when the pipe is restrained as in concrete or is otherwise anchored can lead to cracking and breakage.
- Freezing of pipe contents when the line is full can lead to breakage.
- When heat is introduced by a pump especially when on recirculation, the pipe or joints can fail.
- Expansion and contraction can cause leakage or breaks at joints.
Crush strength of the plastic pipe and fittings should not be exceeded. Similarly, excessive suction or vacuum must be avoided. Since plastics are relatively soft they can be damaged using pipe wrenches on threaded connections. Pipe should not be used as a "ground" for electrical systems and conditions of "static electricity" should not be created through excessive friction. Welding or torch cutting operations near plastic pipe can cause damage to the pipe due to burning by sparks or overheating. High chrome acid solutions and high nitric acids can lead to stress cracking; also, when certain chemicals and solvents are absorbed into the pipe and fittings surfaces, a softness will develop in the plastic which can lead to weeping or rupture.
Proper trenching and backfilling procedures will provide a level and clean bed and will avoid impact and cutting from large or sharp rocks.
When using cement in making pipe joints, follow in detail the instructions in the solvent cement pamphlet.
SAFETY INFORMATION ON PRIMERS AND SOLVENTS
Over a period of 30 years, millions of solvent cemented joints have been made with only rare cases of mishap. However, since these products are flammable and contain chemical solvents, appropriate safety precautions should be taken.
Virtually all solvent cements and primers for plastic pipe are flammable and should not be used or stored near heat, spark or open flames. Do not smoke during use. Cement should be stored in closed containers at temperatures between 40°F and 110°F. They should be used only with adequate ventilation. In confined or partially enclosed areas, a ventilating device should be used to remove vapors and minimize their inhalation.
Respirators especially designed to minimize the inhalation of organic vapors can also be used, They are commercially available.
Containers should be kept tightly closed when not in use and covered as much as possible when in use. Use of an applicator can with applicator attached to a lid is especially recommended.
Avoid frequent contact with skin and eyes. May be absorbed through the skin. May cause eye injury. In case of contact, flush with plenty of water for 15 minutes. If irritation persists, get medical attention. If swallowed, call a physician immediately and follow precautionary statement given on side panel of cement container. Keep out of reach of children.
USE CAUTION WITH WELDING TORCHES
At construction sites where plastic pipe is being installed or has recently been solvent welded, special caution should be taken where using welding torches or other equipment where sparks might be involved. Flammable vapors from cemented joints sometimes linger within or around a piping system for some time.
Special care must be taken when using a welding torch in these application:
- Well casing installations
- Installing pumps in irrigation water lines
- Installation of plastic pipe systems in industrial plants
In all cases, lines should be purged to remove solvent vapors before welding.
USE CAUTION WITH CALCIUM HYPOCHLORITE
Do not use a dry granular calcium hypochlorite as a disinfecting material for water purification in potable water piping systems. The introductions of granules or pellets of calcium hypochlorite with solvent cements and primers (including their vapors) may result in violent chemical reactions if a water solution is not used. It is advisable to purify lines by pumping chlorinated water into the piping system – this solution will be nonvolatile.
Furthermore, dry granular calcium hypochlorite should not be stored or used near solvent cements or primers.
Actually, solvent cementing is no more dangerous than putting gasoline in your automobile. People have learned they must be careful with gasoline. Although solvent cements are not as flammable as gasoline – users must learn to be careful. Again, accidents and injuries have seldom occurred in the use of our products. Help maintain and improve this excellent record by following the above recommendations.