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10.20 CHAPTER TEN

purities in the chlorine that would be detrimental to the chlorine gas feeder. Evaporators
should be equipped with an automatic shutoff valve interlocked to the evaporator opera-
tion to prevent liquid chlorine from passing to the chlorine feeder.
When possible, all portions of the chlorine feed system that contain liquid chlorine
should be designed and operated with all the liquid in the system as a continuous medium.
To shut down the evaporator, it is necessary only to close the effluent valve on the evap-
orator. No other valves between the evaporator effluent valve and the liquid chlorine con-
tainer should be shut. Long liquid chlorine lines should be avoided, but if they are un-
avoidable, chlorine expansion chambers should be provided. It should be emphasized that
liquid chlorine has a high temperature expansion coefficient. Unless expansion is permit-
ted, the temperature increase in trapped liquid will result in pressure high enough to rup-
ture the pipes. As such, any sections of liquid chlorine piping that can be isolated should
be fitted with an expansion chamber. Economical design should limit the number of ex-
pansion chambers, and as such isolation valves should be used only as strictly necessary.
In chlorine system design, the storage media, evaporators, and vacuum regulators are
generally kept in a dedicated room and the balance of the equipment in a separate room.
Because of the extreme health hazard associated with exposure to concentrated chlorine,
individual exposure to chlorine should be limited as much as possible. Chlorine storage
rooms should have controlled entry points, and access to these rooms should be limited
to qualified individuals. To prevent chlorine release to the surrounding area and to limit
exposure to individuals, some building codes require either that the chlorine storage area
have a chlorine gas scrubber or that the cylinders or ton containers be kept in a secondary
vessel or "coffin."
For very large chlorine systems, tank trucks are often used. In this case, automatic
shutoff actuators should be installed to isolate the truck by closing the truck valves in the
event of a chlorine leak. This requirement is dictated by recent changes to the law en-
forced by the Department of Transportation. This requirement is only enforceable if the
truck cab is connected to the trailer; however, it is still recommended that these automatic
shutoff systems be installed. These automatic shutoff systems are also recommended if
the storage medium is railroad tank cars. Equivalent shutoff systems are available for
cylinders and ton containers. The systems for tank trucks and railroad tank cars must be
pneumatically driven. The systems for cylinders and ton containers are generally electri-
cally driven. While chlorine leaks or releases from 150-1b cylinders and 1-ton containers
can be contained or scrubbed relatively easily, releases from tank trucks and railroad tank
cars are difficult to contain. This should be considered when addressing security needs.
Vacuum regulators come in various sizes and configurations. In general, they are usu-
ally wall-mounted, but for small systems where gas withdrawal is used, vacuum regula-
tors can be mounted directly on the cylinder or ton container. These regulators are suit-
able only if a single cylinder or ton container is used at a time. Because of small differences
in the physical construction when multiple vacuum regulators are used in parallel, they
will open to different degrees. As a result, it becomes possible to pull chlorine at unequal
rates from the multiple containers, and liquid chlorine can be pulled through the vacuum
regulators. As stated above, the piping materials generally used downstream of the vac-
uum regulators cannot withstand contact with liquid chlorine and will rapidly degrade and
fail under those conditions.

Gas Feeders and Injectors/Gas Induction Units

Chlorine gas feeders are commonly called chlorinators. Often this includes the injector
(shown in Figure 10.9), but sometimes it does not. For clarity, rather than the term chlo-
rinator, the term chlorine gas feeder is preferred.