Can you fuse different SDR’s together?

Yes, the general rule is that you can fuse different DR’s together if they are “one step” apart. If they are more than one DR difference, boring the end of the thicker one is recommended.

In what pipe sizing dimensions is HDPE available?

IPS (Iron Pipe Size) and DIPS (Ductile Iron Pipe Size). CTS (Copper Tube Size), Metric dimensions and ID controlled pipe.

How do you connect HDPE to ductile iron?

With an MJ adapter or with flanges.

What are the different methods for connecting HDPE pipe and fittings?

Butt fusion, socket fusion, electro fusion, sidewall fusion, compression couplers, and flange adapters.

What specifications are used in the manufacturing of HDPE fittings?

Rahn fittings are manufactured according to ASTM Standards D3035, D3350, D3261 and others, with NSF/ANSI 61 (2” IPS – 12” IPS HDPE PE4710). Our Gas line is also CSA B137.4 compliant. Contact us for complete details on particular products.

How does the use of HDPE pipe save money for a utility?

HDPE pipe provides the lowest life cycle cost when compared to other systems due to significantly reduced or no leakage, increased billable dollars, water conservation, fewer new water-treatment plants, reduced maintenance crews, reduced seasonal water-main breaks, and no loss in flow capacity over the long term. Refer to paper by CSIRO, Life Cycle Analysis of Water Networks, presented at Plastics Pipe XIV, Budapest, 2008.

Is HDPE pipe a green solution for piping?

Yes. It is safe when manufactured, used, or incinerated. It helps preserve water and electricity as there is no loss of water through the fused joint.

Why is a fusion joint better than a gasket joint?

A fusion joined pipeline may be thought of as a continuous pipeline without joints. On the other hand, gasket joints are a potential source of leakage and lost water in many water systems. Leaks may occur if the gasket is improperly installed, if dirt or grit sticks to the gasket, if the gasket is not properly lubricated, if negative pressure (vacuum) occurs in the pipeline, if ground movement or sub-trench consolidation occurs, if significant thermal change occurs and if gaskets are blown out due to surge pressures. Fused joints are far superior to gasket joints for leak prevention.

Is thermal expansion and contraction of HDPE pipe a problem?

No. All pipes expand and contract with change in temperature. The key is management of the resultant thermal strain. As with all materials, expansion and contraction must be taken into consideration when designing a HDPE piping system. Buried pipelines usually do not move due to soil friction. However, thermal effects must be considered for above grade applications. The unrestrained coefficient of thermal expansion for HDPE pipe is approximately 9×10-5 in/in/oF. Information regarding thermal calculations for restrained and unrestrained above-ground and slip-lined pipelines can be found in PPI’s Handbook of Polyethylene Pipe, 2nd ed.

Why and how are HDPE fabricated fittings de-rated? Are molded fittings de-rated?

Fabricated Fittings are de-rated due to their geometry, resin properties and wall thickness. Moulded fittings are designed with a thicker body wall (which can handle water hammer and surge pressures). Fabricated fittings do not have a thicker body, so these fittings must be made from thicker pipe in order to handle higher pressures.
Industry standard derating factors for Fabricated Fittings (depending on the geometry of the fitting) have been used for some time now. Elbows were typically derated 25%, Tees at 50% and Wyes were only derated 40%. Recent modeling has led the American Society of Engineers (ASME) to assign increased de-rating factors according to fitting geometry, resin properties (Hydrostatic Design Stress – HDS) and even wall size. For example, Lateral Wyes were typically derated at 40%, but recent modeling confirms that Wyes are much weaker and must be de-rated at 67%.
Moulded fittings are not de-rated.
Consideration must also be applied to the ambient temperature and fluid media temperature when de-rating the PE pipeline system. As the temperature to which the PE pipe and fitting is exposed increases above the reference temperature (20°C) the long-term hydrostatic strength decreases. Consequently, the pipe and fitting pressure rating must be also be de-rated to suit the operating temperature as required.

What is the difference between 3608 and 4710?

The Hydrostatic Design Stress (HDS) is different. When calculating for pressure ratings, the HDS of the resin is used to determine the Working Pressure Rating (WPR) of the fitting. For example, a fitting made from PE4710 and SDR 11 would be calculated as follows:

2 x HDS / SDR -1
2 x 1000 / 11 – 1

Conversely, a fitting made from PE3608 and the same SDR 11:

2 x HDS / SDR – 1
2 x 800 / 11 – 1
1600 / 10

Two different pressure ratings and the Resistance to Slow Crack Growth and Stiffness is much improved vs. PE3608. You can use a PE4710 DR 11 fitting or pipe to replace a PE3608 DR 9 fitting or pipe and still have the same pressure rating of 200psi (so you can save on cost as well).