Page 64 - Fluid mechanics, heat transfer, and mass transfer

FRICTION AND PIPING 41

& Material of construction. & Type 316L and other stainless steels or better alloys
& Pipe specification. make them suitable from electropolishing.
& Insulation specification. & For inert or nonreactive gases, using copper is as
expensive as 316L stainless steel, making replace-
& Piping and instrument diagram (P&ID).
ment of copper by the later as an attractive choice,
& Line sequence number.
due to its many advantages: it is generally suitable for
& From and to information.
even corrosive or reactive gases, the leakproof char-
& Pipe code.
acteristics of compression fittings or welded joints is
& Heat tracing. far superior, with its less installation costs.
& Operating pressure. & For extremely corrosive or reactive sample or process
& Design pressure. lines, high nickel alloys may be a good choice.
& Operating temperature. & Piping materials and installation for oxygen deserve
special care. At concentrations above 23%, oxygen
& Design temperature.
can be extremely hazardous. Even a small amount of
& Type of cleaning.
a contaminant that is ignition proof in air will ignite
& Piping test pressure test fluid and type of test.
or explode when exposed to a pure oxygen atmo-
. What is a duplex tube? sphere. Therefore, the piping system and components
& Duplex tube is a bimetallic tube involving a combi- must be certified as cleaned and suitably installed for
nation of two different materials. Used where corro- oxygen service.
sive environments are involved with respect to one of & Many facilities require piping systems carrying high-
the fluids in a heat exchanger. pressure oxygen (20 bar) to be made of Monel, which
. Can copper be used for piping and fittings for handing strongly resists promoted ignition in pure oxygen.
acetylene? Give reason. & Fluorine, fluorine mixtures, and certain fluorine com-
& Copper can never be used for an acetylene piping pounds such as hydrogen fluoride require high nickel
systembecausetheacetylenewillreactwiththecopper alloys or, for some components, pure nickel.
to form hazardous and explosive compounds such as & All components and piping must be passivated for
copper acetalide that explodes on contact with copper. fluorine service. This involves slowly increasing the
. What are the options available in selection of materials concentration of fluorine in the system until the
for modern piping systems, with special reference to internal surface reaction sites of the piping and its
gaseous systems? components have a metal fluoride layer that prevents
& New alloys have greatly extended the life of lines in further reaction with fluorine. Any system modifica-
corrosive service. tion or addition necessitates repeating this process.
& Improvements in welding processes, joining techni- & Glass-coated stainless steel often is an attractive
ques, and fittings have reduced the maintenance tasks option for highly reactive samples, which imparts
on many types of installations while reducing inertness and corrosion resistance.
chances of leaks and purity of the resulting systems. & Besides tubing, many components including valves,
& Consideration of properties of the fluid and the pressure control regulators, and different other parts
process or instrumentation. can be glass coated.
& For process and instrumentation gases, maintaining . What are the advantages and applications of plastic
purity is a key requirement. piping?
& It is of no good to purchase high purity grades of & In general, one of the greatest advantages of plastic
instrumentation gases if the delivery pipeline con- pipe is its corrosion resistance.
taminates them. & Different types of plastic piping can be buried in
& All materials selected should be cleaned to very high alkaline or acidic soils without requiring any paint or
levels, delivered to the site capped and installed by special coating.
persons using processes capable of maintaining that & Plastics containing titanium oxide for ultraviolet
level of purity. protection strongly resist weathering.
& Copper tubing or pipe should be of a standard suitable & Most plastic pipe also is not susceptible to scaling.
at least cleaned for oxygen service that guarantees it Such piping systems maintain their full fluid han-
as free of hydrocarbon contamination as possible and dling capability throughout their entire service life.
safe for use in oxygen piping systems. This means that it is often possible to reduce the