EXPANSION TANKS –
Every closed-loop system must have an expansion tank because it is sized to manage excess water resulting from temperature changes and water expansion. Either hot water, cold water, condenser water or both. Expansion tanks are not necessary in open systems. Like a water loop in a cooling tower. A makeup area is also provided by an expansion tank. For automatic water replacement of the system is lost due to many reasons including Leakage due to pump glands or maintenance.
Types of Expansion Tanks: There are 4 types of Expansion Tanks:
A. Vented or Open Steel Tank
B. Closed Steel Tank
C. Diaphragm Tank
D. Bladder Tank
A. Vented or Open Steel Tank
open or vented steel tanks. Open tanks must be placed at the system’s highest point since they must be vented. The open air/water contact leads in a constant migration of air into the system, which causes corrosion. Water temperature cannot be above 212°F (100°C). As a result, this style is hardly ever utilized today.
B. Closed Steel Tank
The vent on this tank is covered, but it is otherwise identical to the vented tank. This enables the tank to operate at higher temperatures and at any location within the system. However, they still have the air/water contact that promotes corrosion, and occasionally the air in the tank slowly leaks out as it is assimilated into the water. This type of tank also needs to be bigger than precharged tanks unless it has been precharged to the minimum operational pressure before being connected to the system. (See the sidebar titled “Expansion Tank Sizing Formulas.”) As a result, this style is likewise hardly rarely utilized today.
C. Diaphragm Tank
This was the first compression tank design that was precharged (to minimize tank size) and had an air/water barrier (a flexible membrane, to prevent air migration). The tank must be replaced if the flexible diaphragm ruptures since it is normally attached to the side of the tank towards the centre and cannot be replaced in the field.
D. Bladder Tank
In bladder tanks, the inflated water is received by a bladder resembling a balloon. In order to prevent harm to the bladder in the event that it becomes saturated, bladders are frequently sized for the entire tank contents, or a “full acceptance” bladder. Usually, bladders can be changed on the battlefield. These days, the most popular kind of huge commercial expansion tank is one like this. (For an example pipe diagram, see the sidebar titled “Typical Expansion Tank Piping”).
Calculate the Required Tank Volume (V_tank)
The formula to calculate the required expansion tank volume is:
V_tank = (V * ΔT) / (β * ΔP)
- V_tank = Required expansion tank volume (in gallons or liters)
- V = Total system volume (in gallons or liters)
- ΔT = Maximum temperature change (in °F or °C)
- β = Fluid expansion coefficient (1/°F or 1/°C)
- ΔP = Allowable pressure increase (in psi or kPa)
