4. RAUPEX PEXa PIPE
4.1 Pipe Properties
Crosslinked polyethylene is polyethylene (PE) which has undergone a
change in molecular structure whereby the polymer chains are
chemically linked, crosslinked (X), with each other to form a three-
dimensional network. The result is a
fl
exible thermoset polymer with
improved mechanical, thermal and chemical properties.
There are three methods of manufacturing PEX:
- The peroxide method (PEXa), ASTM requires a minimum of 70%
crosslinking
- The silane method (PEXb), ASTM requires a minimum of 65%
crosslinking
- The radiation method (PEXc), ASTM requires a minimum of 65%
crosslinking
RAUPEX pipe is manufactured using the peroxide method (PEXa),
which yields the highest, most consistent level of crosslinking. PEXa
technology enhances
fl
exibility and thermal memory, providing ease of
handling and kink repair compared to PEXb and PEXc.
PEXa has distinct advantages over other polymer pipes and metal:
- Resists pitting and stress corrosion
- Resists scaling and deposit build-up when used with both hard and
softened water
- Minimizes noise that is transmitted through pipes
- Resists notching and abrasion damage
RAUPEX is manufactured by REHAU in a facility whose quality
management system is ISO 9001 certi
fi
ed. In addition, RAUPEX
production is independently monitored annually by NSF International,
CSA Group and Underwriters Laboratories Inc. (UL).
Table 4.1: RAUPEX Properties
Speci
fi
cation
English
SI
Standard
Minimum
Density
58 lb/ft
3
926 kg/m
3
ASTM F876
Minimum
Degree of
Crosslinking
70%
70%
ASTM F876
Max Thermal
Conductivity
2.84 Btu in/(ft
2
˚
F
•
hr)
0.41 W/(m
˚
K)
DIN 16892
Coef
fi
cient of
Linear
Expansion
9.33 x 10-4 in/ft
˚
F
@68
˚
F
1.33 x 10-3 in/ft
˚
F
@212
˚
F
0.14 mm/(m
˚
C)
@20
˚
C
0.2 mm/(m
˚
C)
@100
˚
C
Mean @
20-70
˚
C per DIN
16892
Modulus of
Elasticity
87,000-130,500 psi
@ 68
˚
F
43,500-58,000 psi
@176
˚
F
600-900 N/mm
2
@20
˚
C
300-400 N/mm
2
@80
˚
C
Minimum @
20
˚
C per DIN
16892
Speci
fi
cation
English
SI
Standard
Tensile
Strength
4194-4355 psi
@68
˚
F
2610-2900 psi
@176
˚
F
per ASTM D638
26-30 N/mm
2
@20
˚
C
18-20 N/mm
2
@80
˚
C
per ASTM D638
--
IZOD Impact
Resistance
No Break
No Break
--
Roughness
e=0.00028 in.
e =0.007 mm
--
Temperature
Working Range
-40 to 200
˚
F
-40 to 93
˚
C
--
Maximum
Short-term
Exposure
150 psig @ 210
˚
F
(48 hr)
1035 kPa @ 99
˚
C
(48 hr)
ASTM F876
UV Resistance
See TB218
ASTM 2657
4.2 Pipe Dimensions and Weights
RAUPEX white UV shield pipe for residential
fi
re sprinkler systems is
available in nominal sizes ranging from 3/4 to 2 in., and is in accor-
dance to the dimensional standards de
fi
ned in ASTM F876 and CSA
B137.5. RAUPEX is copper tube size (CTS) outside diameter (OD),
which means that the actual OD of the pipe is 1/8 in (3.18 mm) larger
than the nominal size.
Wall thickness is de
fi
ned by the standard dimensional ratio (SDR).
RAUPEX UV shield pipe is SDR9, which equates to the outside
diameter being approximately nine times the wall thickness. Since
PEX pipe has a thicker wall than copper tube, the inside diameter (ID)
is slightly smaller. However, since PEX pipe is not susceptible to the
erosion and corrosion issues of copper tube, systems can be designed
at higher velocities which allow for comparable sizing of a system.
Table 4.2: RAUPEX White UV Shield Pipe Dimensions and Weights
Pipe Size
Average OD
in (mm)
Min Wall Thickness
in (mm)
Weight
lb/ft (kg/m)
3/4 in
0.875 (22.22)
0.097 (2.47)
0.10 (0.15)
1 in
1.125 (28.58)
0.125 (3.18)
0.17 (0.26)
1 1/4 in
1.375 (34.92)
0.153 (3.88)
0.25 (0.37)
1 1/2 in
1.625 (41.28)
0.181 (4.59)
0.35 (0.52)
2 in
2.125 (53.98)
0.236 (6.00)
0.60 (0.90)
4.3 Pipe Markings
RAUPEX pipe markings are repeated every 3 ft (0.9 m), list all
certi
fi
cations and approvals, and include an incremental footage
marking to assist with installation.
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