Polyethylene pressure pipes

Another feature of an extruder is the presence of a gauze filter after the screw and before the die. This effectively filters out any inhomogeneous material which might otherwise clog the die. These screen packs as they are called, will normally filter the melt to 120-150 fim. However, there is conclusive evidence to show that even smaller particles than this can initiate cracks in plastics extrudates e.g. polyethylene pressure pipes. In such cases it has been found that fine melt filtration ( 45 p.m) can significantly improve the performance of the extrudate. 

The development of medium and high density polyethylene pressure pipes over the last thirty years has led to an extensive database on their stress-rupture behaviour, with associated standards for their testing and the interpretation of results [1, 2], Various forms of PVC are also used. The accelerated testing of gas and water pipes is introduced as an example of a field where there is a large database of pressure testing on which current regulations are based, the number of polymers is limited and accelerated tests are widely used (unusually, with two accelerating parameters). 

ISO 8796 2004 Polyethylene PE 32 and PE 40 pipes for irrigation laterals - Susceptibility to environmental stress cracking induced by insert-type fittings - Test method and requirements ISO 9625 1993 Mechanical joint fittings for use with polyethylene pressure pipes for irrigation purposes... 

ISO 13460 1998 Agricultural irrigation equipment - Plastics saddles for polyethylene pressure pipes... 

ISO 14236 2000 Plastics pipes and fittings - Mechanical-joint compression fittings for use with polyethylene pressure pipes in water supply systems ISO 14616 1997 Plastics - Heatshrinkable films of polyethylene, ethylene copolymers and their mixtures - Determination of shrinkage stress and contraction stress ISO 14632 1998 Extruded sheets of polyethylene (PE-HD) - Requirements and test methods... 

ISO 1872-1 1993 Plastics - Polyethylene (PE) moulding and extrusion materials - Part 1 Designation system and basis for specifications ISO 1872-2 1997 Plastics - Polyethylene (PE) moulding and extrusion materials - Part 2 Preparation of test specimens and determination of properties ISO 1969 2004 Fibre ropes - Polyethylene - 3- and 4-strand ropes ISO 3458 1976 Assembled joints between fittings and polyethylene (PE) pressure pipes -Test of leakproofness under internal pressure ISO 3459 1976 Polyethylene (PE) pressure pipes - Joints assembled with mechanical fittings - Internal under-pressure test method and requirement ISO 3501 1976 Assembled joints between fittings and polyethylene (PE) pressure pipes -Test of resistance to pull out... 

ISO 3503 1976 Assembled joints between fittings and polyethylene (PE) pressure pipes -Test of leakproofness under internal pressure when subjected to bending ISO 3663 1976 Polyethylene (PE) pressure pipes and fittings, metric series - Dimensions... 

ISO 4059 1978 Polyethylene (PE) pipes - Pressure drop in mechanical pipe-jointing systems - Method of test and requirements ISO 4427 1996 Polyethylene (PE) pipes for water supply - Specifications ISO 4437 1997 Buried polyethylene (PE) pipes for the supply of gaseous fuels - Metric series - Specifications... 

The general definition of CRC in Subsection 24.1.2 does not specify a quantitative measure. Such a measure has to be defined for each specific problem. As an example, we shall now consider rapid crack propagation (RCP). RCP is a dangerous process. Velocities of 100-400m s (that is 300-1,400 feet s ) have been observed in polyethylene (PE) pipes. Since such pipes are being used for fuel gas distribution within localities RCP might be accompanied by an explosion of the gas pressurized inside. 

EN 12106 Polyethylene (PE) pipes - test method for the resistance to internal pressure after application of squeeze-off. 

ISO 3458 1976 Assembled joints between fittings and polyethylene (PE) pressure pipes -Test of leakproofness under internal pressure. 

ISO 3663 1976 Polyethylene (PE) pressure pipes and fittings, metric series - Dimensions of flanges. 

ISO 4059 1978 Polyethylene (PE) pipes - Pressure drop in mechanical pipe-jointing systems - Method of test and requirements. 

ISO 14236 2000 Plastics pipes and fittings - Mechanical-joint compression fittings for use with polyethylene (PE) pressure pipes in water supply systems. 

Pipes such as polyethylene (PE) and rigid polyvinyl chloride (PVC), pressure pipes in chemical plant. 

Polyethylene, HDPE, MDPE. Applications injection molding for domestic parts and industrial parts blow molding for containers and sports goods extrasion for pressure pipes, pipes, electrical insulating material, bags, envelopes, and tissue. 

According to the comparison curves of the new DUST 8075 1999 Polyethylene (PE) Pipes - PE 63, PE 80, PE 100, PE-HD - General Quality Requirements, Testing even an internal pressure strength of 5.8 N/mm might be assumed. 

The HMW-HDPE with a bimodal MWD is primarily used in film applications to fabricate grocery bags (T-shirt bags) and other merchandise bags. However, polyethylene with a bimodal MWD is also used in premium blow-molding markets and high-pressure pipe applications such as natural gas distribution pipe. 

Creep failures such as those illustrated in Fig. 11.12 are often called static fatigue and are not uncommon in practical applications such as pressurized piping applications. Kinloch and Young (1983) gives data on the creep rupture of high-density polyethylene pipe (HDPE) and an excellent discussion of the mechanisms associated with static fatigue. 

TABLE 5 Physical and mechanical properties of polyethylene gas pressure pipes... 

Alhnan, W. B., Determination of Stresses and Structural Performance in Polyethylene Gas Pipe and Socket Fittings Due to Internal Pressure and External Soil Loads, 1975 Operating Section Proceedings, American Gas Association, 1975. 

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