Environmental Engineering Reference
In-Depth Information
the name of the contents. In addition, the code requires that informa-
tion relating to temperature and pressure be included. Stencils, tape, or
markers can be used to accomplish the marking. To identify the charac-
teristic hazards of the contents, color should be used, but its use must
be in combination with legends.
4.8.4.2 Types of Piping Systems
Piping systems consist of two main categories:
process lines
and
service lines
. Process lines convey the flow medium used in a manufac-
turing process or a treatment process such as fluid flow in wastewater
treatment plants; for example, a major unit process operation in waste-
water treatment is sludge digestion. The sludge is converted from bulky,
odorous, raw sludge to a relatively inert material that can be rapidly
dewatered with the absence of obnoxious odors. Because sludge diges-
tion is a unit process operation, the pipes used in the system are pro-
cess lines. Service lines (or utility lines) carry water, steam, compressed
air, air conditioning fluids, and gas. Normally, all or part of the general
service system of a plant is composed of service lines. Service lines cool
and heat the plant, provide water where it is needed, and carry the air
that drives air equipment and tools.
4.8.5 Metallic Piping Materials
In the not too distant past, it was not that difficult (relatively speak-
ing) to design certain pipe delivery systems; for example, several hun-
dred years ago (and even more recently in some cases), when it was
desirable to convey water from a source to point of use, the designer
was faced with only two issues. First, a source of fresh water had to be
found. Next, if the source was found and it was determined suitable for
whatever the need, a means of conveying the water to the point of use
was necessary.
When designing early water conveyance systems, gr av it y wa s t he key
player. This point is clear when we consider that, before the advent of the
pump, a motive force to power the pump and the energy required to pro-
vide power to the motive force were developed, gravity was the means by
which water was conveyed from one location to another (with the excep-
tion of humans or animals physically carrying the water). Early gravity
conveyance systems employed the use of clay pipe, wood pipe, natural
gullies or troughs, aqueducts fashioned from stone, or any other means
available to convey the water. Some of these earlier pipe or conveyance
materials are still in use today. With the advent of modern technology
(electricity, the electric motor, the pump, and various machines and pro-
cesses) and the need to convey fluids other than water came the need to
develop piping materials that could carry a wide variety of fluids.
Modern wastewater plants have a number of piping systems made
up of different materials. One of the principal materials used in piping
systems is metal. Metal pipes may be made of cast iron, stainless steel,
