pipes and fittings

Sure Union International Ltd. is a supplier of various piping related products as well as sanitary items(include toilet seat and other bathroom accessories). Its business scope includes Pex-Al-Pex Pipe (or multilayer pipe ), pex pipe, PPR pipe, fittings and tools for these pipes, valves, faucets, drainage systems, bathroom shower, woven flexible hoses and other PVC and/or PE hoses.

Wednesday, June 22, 2005

Polyethylene Pipe and Fittings Manufacturing part 1

This chapter describes the production of extruded solid wall and profilewall pe pipe and the molding and fabrication of pe fittings. Qualityassurance and control tests that are required under typical ASTM specificationswill also be discussed.

The principles of pipe and fitting production are to melt and conveypolyethylene into a particular shape and hold that shape during the coolingprocess. This is necessary to produce solid wall and profile wall pipe as well asinjection molded fittings.
The smaller diameters of solid wall polyethylene pipe are continuouslyextruded through an annular die. For large diameter profile wall pipes, the profileis spirally wound onto a mandrel and sealed along the seams.
Solid wall polyethylene pipe is currently produced in sizes ranging from1/2 inch to 63 inches in diameter. Spirally wound profile pipe may he made up to10 feet in diameter or more. There are several specification standards that governthe manufacturing processes for polyethylene pipe, but the main standards forsolid wall and profile pipe include:

ASTM D2239 Standard Specification for Polyethylene (PE) Plastic Pipe(SIDR-PR) Based on Controlled Inside Diameter
ASTM D2447 Standard Specification for Polyethylene (PE) Plastic Pipe,Schedules 40 and 80, Based on outside Diameter
ASTM D2513 Standard Specification for Thermoplastic Gas PressurePipe, Tubing, and Fittings
ASTM D3035 Standard Specification for Polyethylene (PE) Plastic Pipe(SDR-PR) Based on Controlled Outside Diameter
ASTM F714 Standard Specification for Polyethylene (PE) Plastic Pipe(SDR-PR) Based on Outside Diameter
ASTM F894 Standard Specification for Polyethylene (PE) LargeDiameter Profile Wall Sewer and Drain Pipe
Generally, thermoplastic fittings are injection molded, fabricated using sections ofpipe, or machined from molded plates. Injection molding is used to produce fittings upthrough 12 inches in diameter, and fittings larger than 12 inches are normally fabricatedfrom sections of pipe. The main ASTM specifications for injection molded fittingsinclude:

ASTM D2683 Standard Specification for Socket-Type PolyethyleneFittings for outside Diameter-Controlled Polyethylene Pipe and Tubing
ASTM D3261 Standard Specification for Butt Heal Fusion Polyethylene(PE) Plastic Fittings for Polyethylene (PE) Plastic Pipe and Tubing
ASTM F1055 Standard Specification for Electrofusion-TvpePolyethylene Fittings for Outside Diameter-Controlled Pipe and Tubing

Currently, there is not an ASTM specification for fabricated fittings, but an ASTM task group is working on this matter. The industry recognizes the need for thisnew specification due to the rapid growth of demand for large diameter pipe.
All of these standards specify the type and frequency of quality control tests thatare required. There are several steps during the manufacturing process that are closelymonitored to ensure that the product complies with these rigorous standards. Some ofthese steps are discussed in the section of this chapter on quality control and assurance.

History of PVC

Polyvinyl chloride was discovered late in the nineteenth century. Scientists observing the newly created chemical gas, vinyl chloride,also discovered that when the gas was exposed to sunlight, itunderwent a chemical reaction (now recognized as polymerization) resulting in an off-white solid material. But, the solid material was so difficult to work with that it was cast aside in favor of other materials. Years later in the 1920s, rubber scientist Waldo Semon was hired by BFGoodrich to develop a synthetic rubber to replace increasingly costly natural rubber. His experiments eventually produced polyvinyl chloride. Although product developers began to use PVC in a variety of ways ? in shoe heels, golf balls, and raincoats, to name just a few ? its application increased significantly during World War II.PVC turned out to be an excellent replacement for rubber insulation in wiring and was used extensivelyon U.S. military ships. After 1945, its peace-time usage exploded.