25 May 2005
5. Based on real-time, continuous
measurement of chemical
concentration in the water
2. Telecommunications (wired,
wireless, or internet)
Chemical Pumps. Chemical pumps are selected by the specific
application for which they will be used, considering materials of construction, head
pressure capacity, and volume capacity.
Feed Pumps. Feed pumps tied to pulsing makeup meters or some other
type of proportional feed system are recommended for most systems, especially large
steam and cooling water systems and unmanned small systems. The most desirable
feed method is to turn on the feed pumps when the continuous real-time measurement
of the inhibitor indicator indicates that the inhibitor level is below the desired treatment
level. Pumps that turn on in response to continuous real-time measurement can
provide control to within 3 ppm of the desired treatment level.
Pumps of Various Types. Pumps of various types can take suction from
chemical solution tanks and inject a solution of a chemical into a line, a boiler drum, or a
cooling tower basin. Pump types include piston pumps, spring-loaded diaphragm
pumps, hydraulically actuated diaphragm pumps, peristaltic pumps, and gear pumps.
Piston pumps and, to a lesser degree, diaphragm pumps, have trouble with valves
sticking or plugging if there are solids in the stream being pumped. Peristaltic pumps do
not have this problem since they have no valves. They are especially recommended for
feeding sulfuric acid, but they cannot pump against much pressure. Pumps configured
for flooded suction produce a more reliable delivery than pumps that must hold a
suction prime via a foot valve.
Water Meters, Automatic Valves, and Timers
Water Meters. Water meters are selected by the specific application for
which they will be used, considering materials of construction, temperature rating,
pressure rating, and volume capacity. Water meters fitted with an electrical contact
head are used to send low-voltage signals to timers and pumps.
Automatic Valves. Automatic valves are selected by the specific
application for which they will be used, considering materials of construction,
temperature rating, pressure rating, and volume capacity. Cooling towers normally use
solenoid-actuated diaphragm valves. Boiler surface blowdown normally uses a
motorized ball valve.