Environmental Engineering Reference
In-Depth Information
Example 2.5
Problem:
A tank is mounted at a height of 90 ft. Find the pressure at the
bottom of the tank.
Solution:
90 ft × 0.433 psi/ft = 39 psi (rounded)
Note:
To convert psi to feet, divide the psi by 0.433 psi/ft.
Example 2.6
Problem:
Find the height of water in a tank if the pressure at the bottom
of the tank is 22 psi.
Solution:
22 psi
0.433 psi/ft
Height in feet
=
=
51 ft (
rounded)
Note:
One of the problems encountered in a hydraulic system is storing
the liquid. Unlike air, which is readily compressible and is capable of
being stored in large quantities in relatively small containers, a liquid
such as water cannot be compressed. It is not possible to store a large
amount of water in a small tank, as 62.4 lb of water occupies a volume of
1 ft
3
, regardless of the pressure applied to it.
2.4.1 hydrostatic Pressure
Figure 2.2 shows a number of differently shaped, connected, open
containers of water. Note that the water level is the same in each con-
tainer, regardless of the shape or size of the container. This occurs
because pressure is developed within a liquid by the weight of the liq-
uid above. If the water level in any one container is momentarily higher
than that in any of the other containers, the higher pressure at the bot-
tom of this container would cause some water to flow into the container
with the lower liquid level. In addition, the pressure of the water at any
level (such as line T) is the same in each of the containers. Pressure
increases because of the weight of the water. The farther down from the
Liquid
level
T
figure 2.2 Hydrostatic pressure.
