Flashcards in CHW Central Plant Design Deck (20)
When are motorized isolation valves required?
When there are more than 3 cooling towers
By code, all cooling towers must be capable of at least __% water turn-down
What is flow turn down?
The range in which a flow meter or controller can accurately measure the fluid.
What is the turndown ration?
Turndown Ratio = maximum flow / minimum flow
Open cooling towers must maintain their lower basin water level at an elevation that is always ______
than the condenser water pump
CT’s, regardless of brand, typically require continuous support along ___ sides
Vibration isolation is required for CTs located ____?
On the roof
When there are multiple CTs, why is it important to keep inlet and outlet piping symmetrical?
So that piping losses are the same. Uneven pressure drops could result in different flows through towers affecting sump levels.
What is the purpose of an equalizer pipe?
to allow the water in all sumps to attain the same level
Makeup water is....
ICW that's piped to all CT's to replenish water that is constantly being evaporated and bled from the system.
Makeup water rate equals...
Bleed Rate + Evaporation
What is a type of chemical water treatment?
Three chemical tans consisting of 2 biocides (to prevent biological growth) and 1 corrosion inhibitor to maintain pH.
What is a type of non-chemical water treatment?
An ionizing tube, centrifugal separator, and sump sweeper system.
What is an ionizing tube?
a 2 inch long tube attached directly to the the main CW piping that emits electro-magnetic fields into the water. Requires 120v connection.
How does an ionizing tube work?
It neutralizes the natural static charge on the water particles making them the minerals in the water more attracted to the particles than the CT surface, preventing scale formation.
What are the disadvantages of using recycled water for CT makeup?
consistency of quality, availability, amount needed, and control setpoints for TDS levels and the required chemical treatment are different for the two different water sources.
What is TDS?
Total dissolved solids
Why can a single thermowell be used on the common discharge header downstream of all CTs?
Because Title 24 states that all operating fans must be controlled to the same speed.
What two switches are required on CT's?
Vibration and and overflow switches