bed with
satisfactory results.

Fittings--For saturated steam under pressures up to 160 pounds, all
fittings 3-1/2 inches and under should be screwed. Fittings 4 inches and
over should have flanged ends. Fittings for this pressure should be of
cast iron and should have heavy leads and full taper threads. Flanged
fittings in high pressure lines should be extra heavy, and in low
pressure lines standard weight. Where possible in high pressure flanges
and fittings, bolt surfaces should be spot faced to provide suitable
bearing for bolt heads and nuts.

Fittings for superheated steam up to 70 degrees at pressures above 160
pounds are sometimes of cast iron.[78] For superheat above 70 degrees
such fittings should be "steel castings" and in general these fittings
are recommended for any degree of superheat. Fittings for other than
high pressure work may be of cast iron, except where superheated steam
is carried, where they should be of "wrought steel" or "hard metal".
Fittings 3-1/2 inches and under should be screwed, 4 inches and over
flanged.

Flanges for pressures up to 160 pounds in pipes and fittings for low
pressure lines, and any fittings for high pressure lines should have
plain faces, smooth tool finish, scored with V-shaped grooves for rubber
gaskets. High pressure line flanges should have raised faces, projecting
the full available diameter inside the bolt holes. These faces should be
similarly scored.

All pipe 1/2 inch and under should have ground joint unions suitable for
the pressure required. Pipe 3/4 inch and over should have cast-iron
flanged unions. Unions are to be preferred to wrought-iron couplings
wherever possible to facilitate dismantling.

Valves--For 150 pounds working pressure, saturated steam, all valves 2
inches and under may have screwed ends; 2-1/2 inches and over should be
flanged. All high pressure steam valves 6 inches and over should have
suitable by-passes. All valves for use with superheated steam should be
of special construction. For pressures above 160 pounds, where the
superheat does not exceed 70 degrees, valve bodies, caps and yokes are
sometimes made of cast iron, though ordinarily semi-steel will give
better satisfaction. The spindles of such valves should be of bronze and
there should be special necks with condensing chambers to prevent the
superheated steam from blowing through the packing. For pressures over
160 pounds and degrees of superheat above 70, all valves 3 inches