Environmental Engineering Reference
In-Depth Information
(e.g., stainless steel) can accommodate very high pressures (>5000 psi).
As the diameter of the tubing increases, the wall thickness increases
accordingly (slightly).
Ranging in size from 1/32 to 12 in. in diameter, the smaller sizes
are most commonly used. Standard copper tubing ranges from 1/32 to
10 in. in diameter, steel from 3/15 to 10-3/4 in., and aluminum from 1/8
in. to 12 in. Special alloy tubing is available up to 8 in. in diameter.
Typically, in terms of initial cost, metal tubing materials are more
expensive than iron piping; however, high initial cost vs. the ability to
accommodate a particular application as designed (as desired), is a con-
sideration that cannot be overlooked or underemphasized. Consider, for
example, an air compressor. Typically, while in operation, air compres-
sors are mechanical devices that not only produce a lot of noise but also
vibrate. Installing a standard rigid metal piping system on such a device
might not be practical. Installing tubing that is flexible, however, may
have no detrimental impact on its operation whatsoever. An even more
telling example is the internal combustion engine. A lawnmower engine,
like the air compressor, also vibrates and is used in less than static
conditions (i.e., the lawnmower is typically exposed to various dynamic
stresses). Obviously, we would
not
want the fuel lines (tubing) in such a
device to be made with rigid pipe; instead, we would want the fuel lines
to be durable but also somewhat flexible. Thus, flexible metal tubing is
called for in this application, because it will hold up. Simply put, initial
cost can be important; however, considerations such as maintenance
requirements, durability, length of life, and ease of installation often
favor the use of metallic tubing over the use of metallic pipe.
Although it is true that most metallic tubing materials have rela-
tively thin walls, it is also true that most are quite strong. Small tub-
ing material with thin walls (i.e., soft materials up to approximately 1
in. O.D.) can be bent quite easily by hand. Tubing with larger diame-
ters requires special bending tools. The big advantage of flexible tubing
should be obvious: Tubing can be run from one point to another with
fewer fittings than if piping was used.
Note:
Figure 4.11 shows how the use of tubing can eliminate several
pipe fittings.
The advantages of the tubing type of arrangement shown in Figure
4.11 include the following:
•
It eliminates 18 potential sources of leaks.
•
The cost of the 18 90
° elbow fittings required for the piping instal-
lation is eliminated.
•
The time required to cut, gasket, and flange the separate sections
of pipe is saved (obviously, it takes little time to bend tubing into
the desired configuration).
•
The tubing configuration is much lighter in weight than the sepa-
rate lengths of pipe and the pipe flanges would have been.
