Thermoplastics pipes, fittings and assemblies for the conveyance of fluids. Determination of the resistance to internal pressure

The combination of cyclic thermal stresses and sustained internal pressure in a vessel is shown to be a source of progressive expansion of the vessel if the stresses are sufficiently high. Criteria presented allow determination of limits to be imposed on stresses in order to prevent progressive expansion or to allow estimation of the expansion per cycle where stresses are sufficient to produce growth. The effect of strain-hardening of the metal on progressive reduction of the growth rate is discussed.

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The Influence of Internal Pressure on Pipeline Natural Frequency

Volume 3: Pipeline and Riser Technology ◽

10.1115/omae2009-79666 ◽

2009 ◽

Author(s):

Andre´ Luiz Lupinacci Massa ◽

Nelson Szilard Galgoul ◽

Nestor Oscar Guevara Junior ◽

Antonio Carlos Fernandes ◽

Fa´bio Moreira Coelho ◽

...

Keyword(s):

Internal Pressure ◽

Natural Frequency ◽

Axial Force ◽

Natural Frequencies ◽

Pipe Wall ◽

Element Model ◽

Straight Pipe ◽

Temperature Expansion ◽

Force Concept

Galgoul et al. (2004) have written a previous paper in which they have pointed out the conservatism of the latest recommendations for pipeline freespan evaluations, associated to the way the axial force is considered in the determination of the pipeline natural frequency. First because it fails to consider the fact, that the axial force of a sagging pipe, subject to temperature expansion, is much smaller than that of a straight pipe. Second because the effective axial force caused by internal pressure should not be used to determine the pipeline natural frequency. Fyrileiv and Collberg (2005) also discussed this aspect. In order to back up their previous arguments the authors decided to perform some tests an axially restrained pipeline at both ends, which was pressurized in order to justify their claims that these pipelines are not only under tension (and not compression), but also that their natural frequencies increase instead of reducing, although they do bend out because of the pressure, reaching a point of instability. The authors understand the effective axial force concept and the enormous simplifications, which it brings to an otherwise cumbersome problem, but wish to emphasize that these advantages are not unlimited and that this is one of these restrictions. To back up the text results a finite element model has been produced, in which the internal pressure is taken into account as it actually is (and not as an axial force) to show that the pipe wall stresses can only be obtained correctly in this manner.

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Evaluation of ASME Class 3 HDPE Flanged Joints

Volume 6B: Materials and Fabrication ◽

10.1115/pvp2017-65990 ◽

2017 ◽

Author(s):

Thomas M. Musto ◽

Glenn R. Frazee ◽

Michael P. H. Marohl

Keyword(s):

Internal Pressure ◽

Joint Analysis ◽

Special Design ◽

Design Considerations ◽

Piping Systems ◽

Torque Values

In the design of piping systems, there are many options for transitioning between HDPE and metallic piping. One common option is the use of flanged joints. As a result of the visco-elastic nature of HDPE, the use of HDPE-to-metallic flanged joints requires special design considerations. When HDPE-to-metallic flanged joints are used in ASME Class 3 systems, the design is further complicated by the requirements provided in the ASME B&PV Code, Section III for flanged joint analysis. This paper examines the differences between HDPE piping flanged joints and metallic piping flanged joints, including consideration of industry guidance and available industry testing results. The paper provides a proposed methodology for evaluating ASME Class 3 HDPE-to-metallic flanged joints and HDPE-to-HDPE flanged joints, including the determination of required bolt torque values and the determination of the maximum internal pressure that the joint can resist without experiencing leakage.

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