Buying Guide

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Revised 7/20/2018
How Ductile Iron Compares to Cast Iron and Cast Steel
Minimum Mechanical Properties
Pressure/Temperature Ratings Comparing
Cast Iron, Ductile Iron and Cast Steel
ASTM A126 ASTM A395 ASTM A216 WCB
Cast Iron *Ductile Iron Cast Steel
°F/°C Temperature Class 125 Class 150 Class 150
2"-12" 14"-24" 2"-24" 2"-24"
-20°F-100°F 200 psi 150 psi **285 psi 285 psi
150°F/66°C 200 psi 150 psi 243 psi
200°F/93°C 190 psi 135 psi 235 psi 260 psi
250°F/121°C 175 psi 125 psi 225 psi
300°F/149°C 165 psi 110 psi 215 psi 230 psi
350°F/177°C 150 psi 100 psi 210 psi
400°F/204°C 140 psi 200 psi 200 psi
450°F/232°C 125 psi 185 psi
500°F/260°C 170 psi 170 psi
550°F/288°C 155 psi
600°F/316°C 140 psi 140 psi
650°F/343°C 125 psi 125 psi
* These ratings apply when temperature exceeds 450°F and the valve has 316 SS trim. When ASTM B584 trim is used, maximum temperature limit is 450°F.
** ENGINEERING NOTE: NIBCO ductile iron valve wall thickness is designed to ASME B16.1 Class 125 standards, exceeding the wall thickness requirements of
ASME B16.42 Class 150. NIBCO ductile iron valves are rated for susstained operation of 285 CWP when connected to Class 150 flanges.
Chemical Analysis
Cast Iron ASTM A126 Ductile Iron Cast Steel
Class B* ASTM A395 ASTM A216 WCB
Iron and Residuals% 94.0 94.5 98.1
Carbon% 3.3 3.0 0.3
Silicon% 2.0 2.5 0.6
Manganese% 0.7 1.0
* Typical composition, ASTM Standard does not specify materials to this detail.