Fire Protection Philosophy and Design Guide

FIRE PROTECTION PHILOSOPHY AND DESIGN GUIDE
PROCEDURE NO.
PTD-DGS-133
REV
0
DATE
Nov. 11, PAGE OF 50
APPENDIX 6
HDPE PIPE
Polyethylene materials for pressure piping are identified by an ASTM Material Code.
HDPE (high density polyethylene) is coded PE 3408.
HDPE pipe has a maximum allowable pressure rating as given by the formula P = 2 HDB f
E
x f
T
/(DR-1)
P = Internal pressure, psi
HDB = Hydrostatic Design Basis @ 73 F (1600 for PE) f
E
= Environmental Design Factor (0.5 for water)
f
T
= Service Temperature Design Factor (1.0 for 73 F 0.78 for 100 FDR = OD / thickness (t)
DR 11 has a nominal service pressure rating of 160 psi, but fora design temperature of
100 F, the maximum coincidental design pressure rating is 125 psig. Thus it would not satisfy the minimum design temperature and pressure conditions for most firewater systems. DR 9 has a nominal service pressure rating of 200 psi, but fora design temperature of
100 F, the maximum coincidental design pressure rating is 156 psig.
DR 7 (7.3) has a nominal service pressure rating of 255 psi, but fora design temperature of 100 F, the maximum design pressure rating is 198 psig.
HDPE pipe is generally sized based on the OD For DR 9 a 12” line has an ID of 9.746 in. and for DR 7, a 12” line has an ID of 9.046 in. Be sure to input the ID when doing hydraulic calculations or determining linear velocity.
ASME B – 2002 Section A Allowances for Pressure and Temperature Variations indicates that fora) Nonmetallic Piping. Allowances for variations of pressure, or temperature, or both, above design conditions are not permitted. The most severe conditions of coincident pressure and temperature shall be used to determine the design conditions fora piping system.
The following table provides pressure ratings for DR and DR 9 HDPE at several temperatures, some of which would be inapplicable to firewater systems except in special situations.

FIRE PROTECTION PHILOSOPHY AND DESIGN GUIDE
PROCEDURE NO.
PTD-DGS-133
REV
0
DATE
Nov. 11, PAGE OF 50
SDR7
f
E
0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 T (deg C 44 41 40 38 33 30 26.2 23
f
T
0.5 0.698 0.739 0.753 0.78 0.853 0.897 0.953 DR 7.3 7.3 7.3 7.3 7.3 7.3 7.3 P (PSI 177.27 187.68 191.24 198.10 216.63 227.81 242.03 P (KG/CM
2
)
8.93 12.46 13.20 13.45 13.93 15.23 16.02 17.02 17.86
SDR9
f
E
0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 T (deg C 44 41 40 38 33 30 26.2 23
f
T
0.5 0.698 0.739 0.753 0.78 0.853 0.897 0.953 1
SDR9 9
9 9
9 9
9 9
9 P (PSI 139.60 147.80 150.60 156.00 170.60 179.40 190.60 P (KG/CM
2
)
7.03 9.82 10.39 10.59 10.97 11.99 12.61 13.40 The advantages of HDPE are its resistance to internal or external corrosion, which is important since it is used underground. It will not become brittle in cold environments. It is flexible and not likely to crack with gradual settlement of the site. It is smooth and does not support the growth of organisms it has high c and would be expected to retain it for the life of the pipe. It has year life expectancy.

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