Page 42 - HVAC Pump Handbook

Rishel_CH03.qxd 20/4/06 5:35 PM Page 39

Piping System Friction
Piping System Friction 39

TABLE 3.3 Rating of Cast Iron Pipe Fittings
(Threaded Fittings, ANSI B16.4)

Working pressures,
nonshock, psig
Temperature, °F Class 125 Class 250
20 to 150 175 400
200 165 370
250 150 340
300 140 310
350 125 280
400 NA 250
NOTE:NA not acceptable.

TABLE 3.4 Rating of Cast Iron Pipe Fittings (Flanged Fittings, ANSI B16.1)
Working pressures, nonshock, psig
Class 125 Class 250
Temperature, °F 1–12 in 14–24 in 30–48 in 1–12 in 14–24 in*
20 to 150 200 150 150 500 300
200 190 135 115 460 280
225 180 130 100 440 270
250 175 125 85 415 260
275 170 120 65 395 250
300 165 110 50 375 240
325 155 105 NA 355 230
350† 150 100 NA 335 220
375 145 NA NA 315 210
400‡ 140 NA NA 290 200
425 130 NA NA 270 NA
450 125 NA NA 250 NA
NOTE:NA not acceptable.
*For liquid service, these ratings are for class 250 flanges only, not for class 250 fittings.
†353°F to reflect 125-psig steam pressure.
‡406°F to reflect 250-psig steam pressure.

The pressure and temperature ratings of steel pipe, fittings, and
flanges are beyond the scope of this book, since there are a number of
codes for specific applications. Tables 3.3 and 3.4 list the temperature
and pressure ratings for cast iron fittings that are in common use in
HVAC water systems. The cast iron data are included in this book
because of cast iron’s greater reduction in allowable pressure with
higher temperatures.

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