Hydraulic Calculations Flashcards
What is pressure?
How is it measured?
Pressure is a form of energy
Expressed in psi(pounds per square inch), or kPa(kilopascals)
What is elevation pressure?
How do you calculate it?
Height of water above a specific reference point
Calculated by 0.433 x feet in a change of height.
What is static pressure - non-flowing?
The pressure of a fluid on a body when the fluid is at rest
What is residual pressure-flowing?
Force exerted on the inside walls of a pipe when water (or any fluid) is flowing through it
Think of pressure as ___
energy
What is C value?
What are the C value of black steel and plastic piping?
Hazen Williams C Value Table
Lower C values mean more friction higher C values mean less friction.
Black steel (wet system) C value 120
Plastic pipe C value 150
What is laminar, or streamline flowing?
The water particles move in straight-line paths
What is turbulent flow?
the pattern is highly irregular, with a constant churning of the water
What is friction?
resistance to flow, between the fluid and the walls and the fluid particles themselves.
How do we overcome friction within a piping system?
Energy must be spent; this is called pressure.
What is total equivalent length?
Fitting pressure losses are represented as how much pressure would be lost if the water were to flow through a straight piece of pipe.
What are the three basics of hydraulic calculations?
- Sufficient water flow from every sprinkler if they were all to open.
- Water supply must be capable of developing enough flow, at the correct pressure.
- minimize cost.
The procedure for a hydraulically calculated system:
- Hazard classification
- Spacing of sprinklers
- Piping arrangement.
- Amount of water needed at each sprinkler
- Determine number and location of the most demanding sprinklers.
- Start at most remote location and work backwards towards the water supply, calculating the flow and pressures necessary to make sure that each sprinkler head has sufficient water flow.
- Compare demand calculated with water supply
What are the three methods used to determine how much water is needed at every sprinkler head?
- Density/Area method
- Specially listed sprinklers. Contains minimum flow requirements.
- Following NFPA 13 tables or sections. This method is applied to the large drop sprinklers, the EFSR sprinkler and was originally applied to residential sprinklers.
Most residential sprinklers fall under the specially listed category.
Q = K√P
Q=the flow necessary from the sprinkler in GPM
k= the k factor for the sprinkler
P = the pressure necessary at the sprinkler in PSI
N= Ac/As
N = the total number of sprinklers to calculate Ac = the area from the density/area curves As = the area of coverage for the typical sprinklers in the system
NBL= 1.2(square root of area) / s
NBL= number of sprinklers to calculate on a branch line area= the value selected from the density/area curves S = distance between sprinklers on the branch line
Where is the most remote/ most demanding sprinkler head usually located?
It’s usually the first head on the furthest away branch line from the water supply.
The physics of water flowing through the piping actually make the sprinklers closer to the water supply more demanding because they are exposed to a higher pressure and will therefore discharge more water if they open
It is important to make sure that the actual ___ area covered by the sprinklers is at least equal to the ___ area.
the sum of the sprinkler head coverage has to exceed the area of the actual floor area.
Area adjustments may be necessary depending on the following systems/situations.:
- dry-pipe sprinkler system
- double interlock pre-action systems
- high temperate sprinklers(extra hazard occupancies only)
- sloped ceilings
- un-sprinklered combustible concealed spaces.
For dry-pipe sprinkler systems, the design area selected from the density/area curves is required to be increased by 30% due to ___
time delay- to account for the delay of getting the water to the sprinklers. The fire could grow 30% during that time.
Double interlock pre-action sprinkler systems require the same area adjustments as a ___ _____ system
dry pipe system. For the same reasons.
High temperate sprinklers in extra hazard occupancies the design area can actually be decreased by ___% but never below the minimum threshold of ____ sqft
25% but never below the threshold 2000 sqft.
1) fewer sprinklers tend to open in extra hazard fires when high temperature sprinklers heads are used.
2) the heat affects just the heads at the fire location
3) higher densities of water
Quick response sprinklers in light and ordinary hazard occupancies the design area can be reduced by a figure between __% and __% depending on the ceiling height.
What conditions need to be met?
___ pipe system only
___ ft maximum ceiling height
No ____ ceiling pockets
Although the design area can be less than ___ sqft it can be less than _ sprinklers.
Can be reduced by 25-40% only if the following conditions are met:
1) It is wet pipe system only
2) 20 feet maximum ceiling height
3) no unprotected ceiling pockets
4) design area cannot be less 1500 sqft and no less than 5 sprinklers.
Area adjustments for light and ordinary hazard occupancies using quick response sprinklers:
ceilings height <= \_\_' = \_\_% reduction ceilings height = \_\_' = \_\_% reduction ceilings height >\_\_' = no reduction ceilings heights between \_\_' and \_\_'= y= -3x/2 + 55
ceilings height <= 10' = 40% reduction ceilings height = 20' = 25% reduction ceilings height >20' = no reduction ceilings heights between 10' and 20'= y= -3x/2 + 55
y= the percentage reduction in the design area
x= the ceiling height in feet
For light, ordinary and extra hazards where the roof or ceilings above the sprinklers is sloped more than 2 in 12 the design area needs to be increased by __%
30%
To account for the additional sprinklers that open remote from the fire as heat runs up the slope and along the ridge.
When there are multiple reductions/increases in design area calculations must be ____
compounded
1500 x 1.3 x 0.75 = design area
30% increase
25% reduction
What is necessary to qualify for the Room Design Method?
1) The room must be a compartment surrounded by walls and a ceiling.
2) Walls have the appropriate fire-resistance rating according to the hazard classifications.(NFPA 13 tables)
Room design method
Compartments are allowed to have ____ to other compartments as long as there is a lintel over the opening at least ___ inches deep.
There can be opening between compartments as long as there is a lintel(header) over the opening 8 inches deep.
To collect smoke + heat
Room design method
For ___ hazard occupancies, the doors must have some sort of closing capabilities(automatic or self-closer), or the calculations must include ___ sprinklers in the adjoining space.
Room design method
For light hazard occupancies, the doors must have some sort of closing capabilities(automatic or self-closer), or the calculations must include 2 sprinklers in the adjoining space.
Room design method
There is a special set of rules that exist for corridors.
A maximum of __ sprinklers are calculated regardless of the number of sprinklers in the corridor.
maximum of 5 sprinklers.
Room design method
If the room is narrow enough to be protected by a single row of sprinklers the number of sprinklers that are required to be calculated is ___
7
Room design method
*this is no ___ increase or ___ in area calculations
*the ___ sqft rule has to be followed if there are unsprinklered type that require the ___ sqft rule
If there.
* If there is one room that has the highest ___ demand and another that has the highest __ demand then both rooms are considered the most demanding and sets of ___ calculations would need to be performed.
*The water supply would also have to be capable of supplying both of the rooms(individually, not added together)
no increase or decrease.
3000 sqft rule
two rooms
1 highest flow
1 highest pressure
2 hydraulic calculations
water supply must be capable of supplying both individually.
For single hose connections, total water allowance must be at least ___ gpm
50 gpm
For multiple hose connections, total water allowance must be at least ___ gpm
100 gpm
If using k11 or larger sprinklers in EHG1 or 2 design area can be reduced by __ but not below ____ sqft
25% but not below 2000 sqft
