Page 56 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

PIPING

2.6 CHAPTER TWO

ACID-RESISTANT CAST IRON (AR)

Commonly referred to as high silicon iron pipe, acid-resistant CI is an alloy of gray cast iron
containing between 14.25 and 15% silicon, and small amounts of manganese, sulfur, and
carbon. It is available only in extra heavy pattern, with the same dimensions as CI piping.
Joints require two types of pipe ends: hub and spigot or hubless. The hub and spigot
ends can be joined by caulking. Rubless pipe is joined by a compression coupling.
Acid-resistant cast iron pipe shall conform to ASTM A 861 and ASTM A 518.
This specialty piping material is used for drainage of various corrosive liquids, and since
it is stronger than glass, it is recommended for exposed or underground applications where
there is a possibility of physical damage.

CARBON STEEL (ST)

Steel is a very broad category of piping because of the large number of alloys that have been
produced. It is divided into two broad categories according to the method of manufacture:
mill pipe and fabricated pipe. Mill pipe is produced to meet finished pipe specifications.
Fabricated pipe is manufactured from steel plate with spiral or straight welded seams.
Steel pipe is manufactured by either the seamless (extruded) or welded method, and is
available either plain (black) or galvanized (zinc plated inside, outside, or both). Wall thick-
ness is expressed as “schedule,” and ranges from schedule 5 (lightest) to schedule 160. The
wall thickness varies with the size of the pipe. The larger the schedule number, the thicker
the pipe wall for a specific pipe size.
Steel pipe, depending upon type, can be obtained with threaded ends for screwed fittings,
plain ends, and flanged and beveled ends for welding.
There is an extremely large number of steel pipe alloys available. The selection depends
on the intended service. The steel pipe alloys most commonly used for service and utility
systems conform to ASTM A-53: Steel Pipe, Welded or Seamless, Black or Galvanized and
ASTM A-106: Steel Pipe, Welded or Seamless, Black or Galvanized.
Steel pipe is generally used for pressure piping. Its advantages are long laying lengths,
high internal and external strength, and the availability of varying pipe thickness to meet
almost any design pressure. It has good flow characteristics and fire resistance and is low
in initial cost. The most serious disadvantage is low corrosion resistance. This requires
internal and external protection, with galvanizing the most commonly used method.

COPPER

Copper tubing is seamless, made from almost pure copper (99.9 percent), and is available
in hard (annealed) and soft (drawn) form. It is manufactured in sizes ranging from 1/8 to
12 in, but sizes over 6 in are not generally available. All tubing is manufactured with plain
ends only. Joints are made by soldering, and brazing, and with flared and flanged fittings.
The six types of copper tubing used most often are:
1. ASTM B-88 is the grade used most often for potable water, and also for compressed
gases and vacuum systems where high purity is not a factor. It is seamless, available in
nominal pipe sizes from 3/8 to 12 in, in hard and soft temper, and in three wall thickness
grades—K (thickest wall), L, and M (thinnest wall). If patented flare fittings are used,
the pipe must be obtained without outside diameter (O.D.) embossing, which would
interfere with the sealing of the pipe wall against the side of the fitting.

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