The use of cylinders or containers is depends primarily on
the average daily consumption of chlorine, and it depends
on the type of chlorine withdrawal (liquid or gas), the rate
of withdrawal, and the period of withdrawal. Other things
being equal to the purpose of economic, and considering the
practical aspects of an installation, 150 lb cylinders are
the containers of choice when the average daily consumption
of chlorine does not exceed 50 lb. These cylinders are readily
handled by one man using a special two wheel hand truck and
are not necessary to prepare the special handling equipment
like, electric hoist, mono rail for hoist, lifting bar and
container trunnions. Also, the expensive weighing scale is
no need.
The number of
containers or cylinders must be decided considering the chlorine
feeding rate at one shock dosing in advance and exchange period
of empty containers or cylinders. Normally two weeks change
out is recommended.
1) 150 lb Cylinders
As previously
discussed, the maximum gas withdrawal rate per cylinder is
limited to 40 lb per day. It is common practice to maintain
the storage room at a minimum temperature of 0oC.
Cylinders should never be stored in direct sunlight. For systems
using more than five cylinders, a switchover system or a change
to ton containers should be considered.
2) Ton Containers
At room temperature
the maximum gas withdrawal rate from a ton container is approximately
400 lb/day. If the maximum chlorinator capacity is 400 lb/day,
then one container in service will suffice. If it is a 500
lb/day unit, two ton containers must be in service simultaneously.
Theoretically, gas withdrawal can be used up to any capacity
if enough containers are connected to the manifold header.
Switching from gas withdrawal to liquid withdrawal utilizing
an evaporator is necessary when a continuous rate of 1500
lb/day is reached.
The one exception
to this rule of thumb is in intermittent operating installations,
no employed on cooling water circuits. At such installations
it is customary practice of withdrawal rates up to 1000 lb/day
for 30 minutes if the temperature of the storage area never
goes below 50oF. In warmer areas 1500 lb/day gas
withdrawal is safe up to one hour from a single ton container.
This assumes a temperatures-pressure restoration period of
no gas withdrawal of at least twice the length of time as
the withdrawal period.
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