|
QUALITY ALERT
1.SEAMED OR WELDED LINERS
Plastic lined pipe comes in standard spool lengths of 10 and 20 feet. PTFE lined pipe from some manufacturers is only available in 10- foot spools. This is not usually a problem unless the manufacturer tries to weld or seam together two 10-foot liners to make a 20-foot spool. The stress on that seam could cause it to fail in normal service conditions. The ASTM for plastic lined pipe, F-1545, calls for all plastic lined piping systems to pass a steam cold water cycling test. These seamed liners may not pass this test. When seamed liners are placed in service and cycled, they could fail catastrophically. Seaming, welding, or expanding of liners also occurs in some manufacturers fittings, usually where a PTFE preform liner is not available or where the manufacturer does not have the proper molding equipment or tooling to mold the fitting. All fittings in a plastic lined piping system should have a one piece homogeneous liner that is molded in place after all the metal fabrication has been done to the fitting. Anything less is not Quality construction. Remember, plastic lined pipe and plastic lined fittings are generally used where other materials won't work. It is very important that they be made of the best materials available due to the severe service conditions they are used in.
2.VIRGIN UNPIGMENTED RESIN
Ultra high purity water or chemicals require a plastic lined piping system that will not reduce product purity through leaching of contaminates from the liner. Manufacturers of plastic lined pipe and plastic lined fittings offer them with virgin unpigmented liners. Some are not really virgin or unpigmented. If purity is a concern in your process, verify that your supplier of plastic lined pipe is really giving you a virgin unpigmented resin. Some manufacturers use resins that are reprocessed from other processes in their companies and are not really virgin. In unpigmented polypropylene some manufacturers add titanium dioxide to help hide the stress whitening that occurs when polypropylene is processed. Titanium dioxide is a white pigment. These are important considerations when determining who should supply the plastic lined pipe when extractables are critical in your application.
|
