Hydraulics Flashcards
(178 cards)
1
Q
One cubic foot contains……cubic inches
A
1728 cubic inches Pg 6
2
Q
One cubic foot contains……gallons
A
7.5 gallons Pg 6
3
Q
One cubic foot of fresh water weighs……
A
62.5 pounds Pg 6
4
Q
One gallon contains……cubic inches
A
231 cubic inches Pg 7
5
Q
One gallon of fresh water weighs……
A
8.33 pounds Pg 7
6
Q
A column of water 1’ high exerts a pressure of……at its base
A
0.434 psi at its base Pg 7
7
Q
A column of water 2.304’ high exerts a pressure of…..at its base
A
1 psi at its base Pg 7
8
Q
50’ length of 1.75” hose contains……gallons of water
A
6.24 gallons of water Pg 7
9
Q
50’ length of 1.88” hose contains…..gallons of water
A
7.20 gallons of water Pg 7
10
Q
50’ length of 2.5” hose contains…..gallons of water
A
12.74 gallons of water Pg 7
11
Q
50’ length of 3” hose contains……gallons of water
A
18.35 gallons of water Pg 7
12
Q
100’ length of 4” hose contains…..gallons of water
A
65.25 gallons of water Pg 7
13
Q
100’ length of 5” hose contains…..gallons of water
A
101.94 gallons of water Pg 7
14
Q
NP for handlines with SB is … PSI. Pressure can be increased to …. PSI to achieve a higher flow.
A
50 PSI…..65 PSI to achieve a higher flow Pg 7
15
Q
NP for master streams with SB is…..PSI but can be increased to……PSI to achieve a higher flow.
A
80 PSI…..100 PSI to achieve a higher flow Pg 7
16
Q
AAN are designed for….PSI nozzle pressure and flows….GPM with the fog nozzle and…..GPM with the ….. “ slug.
A
50 PSI…..175 GPM fog nozzle…..185 GPM with 15/16 slug Pg 7
17
Q
The nozzle pressure for all other fog nozzles is….PSI unless otherwise indicated
A
100 PSI Pg 7
18
Q
Rectangular Shaped Containers formulas for gallons
A
L’ x W’ x D’ x 7.5……or……L’ x W’ x average depth’ x 7.5 gallons/cubic ft. Pg. 10
19
Q
Cylindrical Containers formulas
A
π x r^2 x H’ (L’) x 7.5 gallons Pg. 11
20
Q
Theoretical Calculations Hand Line 50 PSI 1/2” tip size -….GPM
A
53 GPM Pg 14
21
Q
Theoretical Calculations Hand Line 50 PSI 7/8” tip size -….GPM
A
161 GPM Pg 14
22
Q
Theoretical Calculations Hand Line 50 PSI 15/16” tip size -….GPM
A
185 GPM Pg 14
23
Q
Theoretical Calculations Hand Line 50 PSI 1” tip size-….GPM
A
210 GPM Pg 14
24
Q
Theoretical Calculations Hand Line 50 PSI 1 1/8” tip size-…..GPM
A
266 GPM Pg 14
25
Theoretical Calculations Hand Line 50 PSI 1 1/4" tip size-.....GPM
328 GPM Pg 14
26
Fire Ground Calculations Hand Line 50 PSI 1/2" tip-....GPM
50 GPM Pg 14
27
Fire Ground Calculations Hand Line 50 PSI 7/8 " tip-....GPM
150 GPM Pg 14
28
Fire Ground Calculations Hand Line 50 PSI 15/16 tip-....GPM
185 GPM Pg 14
29
Fire Ground Calculations Hand Line 50 PSI 1" tip-.....GPM
200 GPM Pg 14
30
Fire Ground Calculations Hand Line 50 PSI 1 1/8" tip-.....GPM
250 GPM Pg 14
31
Fire Ground Calculations Hand Line 50 PSI 1 1/4" tip-.....GPM
325 GPM Pg 14
32
Theoretical Calculations Master Stream @ 80 PSI 1 1/4" tip-.....GPM
415 GPM Pg 15
33
Theoretical Calculations Master Stream @ 80 PSI 1 3/8" tip-......GPM
502 GPM Pg 15
34
Theoretical Calculations Master Stream @ 80 PSI 1 1/2" tip-.....GPM
598 GPM Pg 15
35
Theoretical Calculations Master Stream @ 80 PSI 1 3/4 tip-......GPM
814 GPM Pg 15
36
Theoretical Calculations Master Stream @ 80 PSI 2" tip-.....GPM
1062 GPM Pg 15
37
Fire Ground Calculations Master Stream @ 80 PSI 1 1/4" tip-.....GPM
400 GPM Pg 15
38
Fire Ground Calculations Master Stream @ 80 PSI 1 3/8" tip-.....GPM
500 GPM Pg 15
39
Fire Ground Calculations Master Stream @ 80 PSI 1 1/2" tip-.....GPM
600 GPM Pg 15
40
Fire Ground Calculations Master Stream @ 80 PSI 1 3/4" tip-......GPM
800 GPM Pg 15
41
Fire Ground Calculations Master Stream @ 80 PSI 2" tip-.....GPM
1000 GPM Pg 15
42
Rectangular Shaped Containers formulas for volume
L x W x H or D Pg 10
43
Cylindrical Containers formulas for volume
π x r^2 x H' (L') Pg 11
44
Smooth Bore Nozzle Discharge formula
GPM = 29.7 x D^2 x √NP Pg 14
45
1" adjustable gallonage fog nozzle is an adjustable flow nozzle that can be set to deliver.....GPM
12-60 GPM Pg 15
46
The 1 1/2" AAN flows....GPM
175 GPM Pg 15
47
The 2 1/2" Akron Fog Nozzle is an adjustable flow nozzle that can be set to deliver ..... GPM
125-250 GPM Pg 15
48
The Akron Quick - Attack Mercury Monitor flows.....GPM
500 GPM Pg 15
49
Master Stream fog nozzles have an operating range of....GPM
150-2000 GPM Pg 15
50
Booster reel lines are usually a ..... ' long, with a ...." rubber line with an adjustable gallonage fog nozzle that can flow between ...-... GPM with a .... PSI
150' long, 1" rubber line, 12-60 GPM, 100 PSI Pg 16
51
Forestry hose comes in ... and .... sections. A 1" adjustable gallonage fog nozzle that can flow between ... and ... GPM or the ... GPM red fog nozzle can both be use at .... PSI
50' and 100' sections, 12 to 60 GPM, 22 GPM, 100 PSI Pg 16
52
Decon shower flows ...GPM at ...PSI
270 GPM @ 75 PSI Pg 17
53
Piercing Nozzle can flow ....GPM @ .... PSI
125 GPM @ 100 PSI Pg 17
54
The 2 1/2" distributer nozzle flows....GPM @....PSI
250 GPM @ 100 PSI Pg 18
55
The 1 1/2" distributer nozzle flows.....GPM @....PSI
95 GPM @ 50 PSI Pg 18
56
The 2 1/2" cellar nozzle flows......GPM @......PSI
350 GPM @ 100 PSI Pg 18
57
The 1 1/2" cellar nozzle flows......GPM @......PSI
160 GPM @ 100 PSI Pg 18
58
How many different monitors are used in Fairfax County?
3 different types (Smooth Bore Break Away Nozzle, Task Force Tip Automatic Nozzle, Akron Adjustable Flow Nozzle) Pg 18-19
59
Smooth Bore Break Away Nozzle flows between ....-....GPM
500-1000 GPM Pg 18
60
Task Force Tip Automatic Nozzle flows between ...-....GPM
150-1250 GPM Pg 19
61
Akron Adjustable Flow Nozzle flows between ...-....GPM
150-1250 GPM Pg 19
62
Fairfax County utilizes the ....... monitor as its portable monitor
Akron Quick Attack Mercury Monitor Pg 19
63
The Akron monitor offers firefighter multiple options, including .......... as well as ...... and ........ attack
Exposure protection as well as exterior and interior attack Pg 19
64
Akron Quick Attack Mercury Monitor flows ..... GPM.... from either the .... or ...... nozzle.
500 GPM from either the Fog or smooth bore nozzle Pg 19
65
Master Stream: Smooth bore 1 3/8" tip requires .... PSI nozzle pressure
80 PSI Pg 19
66
Master Stream: Fog Nozzle requires .... PSI nozzle pressure
100 Pg 19
67
A single ..." supply hose is used to supply the device (akron quick attack mercury monitor) but a ..." supply hose shall not be used.
A single 3" supply hose is used to supply the device, but a 4" supply hose shall not be used Pg 19
68
Maximum inlet pressure for the Mercury monitor is ... PSI
150 PSI Pg 19
69
Appliance loss for Akron quick attack mercury monitor is ... PSI
10 PSI Pg 19
70
The mercury monitor has a ..... inlet and a ..... outlet with a ..... shut-off, Enabling firefighters to extend off a hose line if desired.
2 1/2" inlet and 2 1/2" outlet with a ball-valve shut-off Pg 19
71
.............. monitors are fixed to the pumper but can be detached and connected to a ground mount to be used as a .......... monitor.
Combination monitors, can be used as a portable monitor Pg 19
72
Master Stream: Smooth bore nozzle flowing between ....-.... GPM at .... PSI NP
500-1000 GPM at 80 PSI NP Pg 19
73
Master Stream: Fog nozzle flowing between ....-.... GPM at .... PSI NP
350-1250 GPM at 1000 PSI NP Pg 19
74
Common causes of friction loss are...... (7 reasons listed)
Kinks or bends in hose, nozzles, appliances, protruding gaskets in the couplings, delaminating hose, pump piping, diameter restrictions Pg 20
75
Which Principle - All variables being the same, friction loss will vary directly with the length of hose or pipe.
1st Principle Pg 20
76
Which Principle - All variables being the same, the friction loss varies approximately with the square of the increase in the velocity of the flow. If the flow rate is doubled the friction loss will be four times greater
2nd Principle Pg 20
77
Which Principle - When the flow remains constant the friction loss in a hose will decrease when the diameter of the hose is increased.
3rd Principle Pg 21
78
Which Principle - For any given flow velocity, friction loss is independent of pressure. The velocity of the water through a hose line, not pressure, causes friction loss.
4th Principle Pg 21
79
Friction loss coefficients:
```
1" = 150
1 3/4" = 10 per fairfax, 15.5 per IFSTA.
1.88" = 10
2" = 8
2 1/2" = 2
3" = 0.8
3 1/2" = 0.34
4" = 0.2
5" = 0.08
Pg 21
```
80
Formula for calculating friction loss is
FL=CxQ^2xL Pg 22
81
1.75^2 is...... (for 1 3/4" hose @ 175gpm)
3.06 Pg 22
82
Add for Appliance Loss: Less than 350 GPM
AL is insignificant so 0 PSI will be used in your calculations Pg 24
83
Add for Appliance Loss: Over 350 GPM
10 PSI appliance loss Pg 24
84
Add for Appliance Loss: Ladder Pipes
25 PSI Pg 24
85
Add for Appliance Loss: Master Streams (except for mercury monitor)
25 PSI Pg 24
86
Add for Appliance Loss: Standpipes
25 PSI Pg 24
87
When hose line discharge location is located above or below the pump, an additional factor must be considered. What is this factor?
Head Pressure Pg 25
88
For fire ground operations, round off 4.34 to 5 PSI for every .....' of elevation or e....f..... above or below the pumper
every 10' of elevation or every floor above or below the pumper Pg 25
89
Formula for elevation pressure
H x 0.434 psi/foot Pg 25
90
PDP stands for what
Pump Discharge Pressure Pg 28
91
PDP is comprised of the following items
Basic Pumper Operator's Formula PDP = NP + TPL Pg 28
92
TPL = ?
Total Pressure Loss (TPL) = FL+ AL + EP Pg 28
93
Maximum safe PDP is?
250 PSI (during normal operations) Pg 28
94
1.85^2 is
3.42
95
The National Foam JS-10 air aspirating nozzle has a rating of .... GPM @ .... PSI at the tip
100 GPM @ 100 PSI Pg 31
96
The National Foam JS-10 air aspirating nozzle can be used in variable ....... or ........ stream control position.
Spray or straight stream Pg 31
97
If not using the JS-10 is not able to be equipped, what other nozzle may be used for foam?
Our Akron Assault break-away nozzle bale may be utilized to provide the firefighter flow control of the hose line. This nozzle can be used with all low expansion foam concentrates. Pg 31
98
Fairfax County Portable Foam Eductor's flow...to....GPM with a pump discharge pressure of.... PSI at the eductor.
95 to 125 GPM, 200 PSI Pg 31
99
The foam eductor must be place how many feet from the pump panel and within how many feet of the nozzle?
must be placed 50' from the pump panel and within 200' of the nozzle. Pg 31
100
Foam operations: The nozzle should be no higher than how many feet above the eductor?
5 feet Pg 31
101
Some pumpers are equipped with the ......., which is a by-pass proportioning system. This is basically an in-line eductor pre-piped into the front bumper discharge.
Akron Truck Mount Pg 32
102
Akron Truck Mount as with the in-line eductor this line must be pumped at what PSI at the eductor?
200 PSI at the eductor Pg 32
103
What is the main benefit to Around the Pump systems during foam operations?
Allow foam solution to flow from all discharges. Pg 32
104
While using Around the Pump system and being supplied from another source, the tank to fill valve must be kept in the what position? and why?
Tank to fill valve must be kept in the closed position during operation to prevent the water tank from becoming contaminated with concentrate. Pg 32
105
The intake pressure must not exceed what? while using the Around the Pump system?
10 PSI Pg 32
106
Some Pierce Pumpers are equipped with the Husky Foam system. What type of system is this?
Electronic Direct Injection Foam System. That injects foam into the front bumper discharge. Pg 32
107
Relay Operations, All 3" lines should be charged to a minimum stating pressure of what?
100 PSI Pg 34
108
Husky Foam system is capable of injecting foam from ....% to ....% with a rated capacity of ....GPM of foam concentrate at .... PSI
Husky Foam system is capable of injecting foam from 0.1% to 3% with a rated capacity of 3 GPM of foam concentrate at 150 PSI. Pg 32
109
Husky Foam system has the capability to fill the foam tank using a....?
pick up tube Pg 32
110
All Fairfax County pumpers carry a minimum of .... gallons of foam
40 gallons of foam Pg 32
111
Which stations have a CAFS engine?
Engines 412, 416, 420, 441 Pg 32
112
What type of apparatus have the unique ability to flow only water; water and class B/class A foam, and air from the pre-connected hand lines discharges.
CAFS Engines Pg 32
113
Fairfax County CAFS pumpers each hold .... gallons of water, .... gallons of class B foam, and .... gallons of class A foam
750 gallons of water, 40 gallons of class B foam, 40 gallons of class A foam Pg 32
114
CAFS Operations: Water is mixed with air supplied from an air compressor on the pump and class A foam to create........
The finished product Pg 32
115
CAFS Operations: CAFS for fire attack: This application consists of .... water and .... air with a foam application rate of ....%
2/3 water and 1/3 air......application rate of 0.3% Pg 32
116
CAFS Operations: CAFS for overhaul and exposure protection: this application consist of.....air and .... water with a class.... foam application rate of.....
2/3 air, 1/3 water, Class A foam and application rate of 0.5% Pg 33
117
CAFS Operations: The amount of water required to create an effective stream is decreased by .....%
25% Pg 33
118
CAFS Operations: Fairfax County CAFS pumpers can flow class A foam or CAFS from five discharges, which five discharges??
Leader Line, Blitz Line, Both cross-lays, and the Bumper Line Pg 33
119
CAFS Operations: The CAFS air compressor can be operated for how long without overheating????
Two Hours Pg 33
120
CAFS Operations: CAFS pumpers have the ability to supply other pumpers and trucks with what 3 options????
Water, Class A Foam Solutions, or CAFS Pg 33
121
CAFS Operations: Hose lines used with CAFS are ..... in weight than hose filled with 100 percent water and are very maneuverable
are lighter Pg 33
122
CAFS Operations: What smooth bore tip creates the best finished product for fire attack??
15/16" Pg 33
123
CAFS Operations: What is the best nozzle/nozzle setting to achieve the best finished product for exposure and overhaul???
CAFS pumpers have the same Akron Assault nozzles but also have the ability to remove the 15/16" slug. Use of the "gated butt" without the smooth bore nozzle creates the best finished product for exposure and overhaul. Pg. 33
124
CAFS Operations: True or False - Hose lines will need to be bled out longer (than lines with only water) prior to beginning the fire attack to ensure the proper mixture.
True Pg 33
125
CAFS Operations: Hose lines need to be kept cracked open at all times when charged to avoid what?
To avoid the build-up of air pressure in the line. Pg 33
126
CAFS Operations: True or False - while utilizing CAFS, hose lines kink more readily than hoses flowing no air. The driver/operator should be aware of this and assist checking for kinked lines and correct to ensure proper flow.
True Pg 33
127
CAFS Operations: Pierce recommends that CAFS only be used in lines up to......in length for maximum effectiveness.
250' Pg 33
128
Relay Operations: Relays are defined as ...... that are in line between the water source and the nozzle.
Two or more pumpers Pg 34
129
Relay Operations: What is the most commonly encountered relay operation?
Attack pumper to supply pumper evolutions Pg 34
130
Relay Operations: What is the initial minimum starting pressure for all 4" supply lines?
50 PSI Pg 34
131
Relay Operations: What is the initial minimum starting pressure for all 3" lines?
100 PSI Pg 34
132
Relay Operations: If a 4" and a 3" supply line are used together they should be charged to a minimum starting pressure of what???
100 PSI Pg 34
133
Relay Operations: True or False - Supply Pumpers under normal operations should not gate down their discharges.
True Pg 34
134
Relay Operations: Once what of the supply line is determined, the proper PDP shall be determined and applied.
Once the flow and length of the supply line is determined. Pg 34
135
Relay Operations: PDP is comprised of what?
PDP = RP + TPL Pg 34
136
In a relay operation, the maximum amount of water being delivered to the fire scene is limited by what???
The water source and the pumping capacity of the smallest pumper in a relay. Pg 36
137
Most Fairfax County pumpers are rated at ...... gpm at ...... PSI pump pressure
1500 GPM and 150 PSI pump pressure Pg 36
138
Where can the pump rating for a pumper be found on the rig??
The pump rating can be determined by reading the pump specification plate. Pg 36
139
True or false - The pump pressure and the flow are inversely proportional
True Pg 36
140
Most hydrants in Fairfax County can deliver a minimum of ...... GPM
1000 GPM Pg 36
141
Multiple Supply Lines Coefficients: Two 3" lines
0.2 Pg 38
142
Multiple Supply Lines Coefficients: One 4" and one 3" line
0.09 Pg 38
143
Multiple Supply Lines Coefficients: Two 4" lines
0.05 Pg 38
144
How do you find the percentage drop??
(SP-RP) 100/SP Pg 40
145
Percentage drop ranges and additional water available for Like Volumes
0-10% with 3 times the original amount, 11-15% 2 times the original amount, 16-25% 1 times the original amount, >25% Less than one of the original amount
Pg 40
146
Standpipe Operations: During standpipe operations the PDP must be sufficient to???? (5 items listed)
1. Overcome friction loss in the attack line
2. Provide the proper nozzle pressure
3. Overcome the elevation pressure in the standpipe
4. Overcome the friction loss in the hose lines to the Fire Department Connection (FDC).
5. Overcome the friction loss in the Siamese, standpipe, and riser valve.
Pg. 40
147
Standpipe Operations: Upon arrival at the scene, after securing a water supply from a hydrant, what should be done???
One line should be connected to the FDC and charged to 150 PSI PDP Pg 40
148
Standpipe Operations: What must be ensured when supplying an FDC?
Ensure that the FDC connection you are supplying feeds the correct address or area. Pg 40
149
Standpipe Operations: Once water is flowing, the operator needs to determine and add the following items together to deliver the correct pressure (5 items listed)
1. The nozzle pressure
2. The Friction loss in the attack line (including any appliances used if the flow is over 350 GPM)
3. 25 PSI for appliance loss in the standpipe and Siamese connection
4. Friction Loss in the supply line from the pumper to the standpipe
5. The height the attack line is above the pumper.
Pg 41
150
Standpipe Operations: If the connection cannot be made at the FDC, a line can be deployed.......???
a line can be deployed to the closest accessible floor and connected to standpipe riser in order to supply the rest of the system. Pg 41
151
Sprinkler Systems: What is the starting PDP for sprinkler systems?
150 PSI Pg 44
152
Sprinkler Systems: When dose the driver/operator charge the sprinkler system??
When there is smoke or fire showing or upon confirmation of a working fire Pg 44
153
Combination Systems: Fire protection systems that use the same supply piping for what 2 systems???
Standpipe and sprinkler systems
154
Combination Systems: How are these systems to be treated/considered upon arrival on scene?
These systems should be considered as a standpipe and supplied and charged immediately upon arrival on the scene and without orders. Pg 44
155
Combination Systems: What is the starting pressure for a combination system??
150 PSI Pg 44
156
Elevated Master Streams: Should aerial devices be provided with their own supply pumper??
Yes, if possible Pg 45
157
Elevated Master Streams: A minimum of what supply line(s) should be used to supply an aerial device?
A minimum of one LDH line or two 3" supply lines should be used
Pg 45
158
Elevated Master Streams: What are the four factors that will determine the correct PDP when supplying an aerial device?
-NP
-AL in appliances (aerial device and the connection) 25 PSI
-EP (nozzle height)
-FL in hoses between the aerial device and the pumper
Pg 45
159
Elevated Master Streams: What will dictate the maximum distance between the aerial and the supply pumper?
The TPL along with the number and size of the supply lines Pg 45
160
Elevated Master Streams: What is the starting pressure for all aerial devices?
150 PSI Pg 45
161
Elevated Master Streams: Name the list of procedures that are common to all aerial device operations, regardless of the type of aerial device.
-Charge lines on orders of the truck OIC or truck driver
-Waterway drains or nozzle must be opened prior to retracting the ladder
Pg 45
162
Blitz Attack: What is a Blitz Attack?
The Blitz Attack is a tactic of rapidly placing a large volume of water on the fire to extinguish the bulk of the fire so it can be easily mopped up using a handline.
Pg 47
163
Blitz Attack: Name 8 procedures the driver/operator needs to utilize to accomplish this tactic
-Temporarily or permanently position the pumper in a location where the deck gun can reach bulk of fire
-Having a firefighter manually operate the deck gun or use the remote controls.
-Adjust the deck gun so it is aiming at the target
-Engage the pump and throttle the pumper up to the proper operating pressure for the deck gun.
-Open the operating valve for the deck gun and flow the water on the bulk of the fire.
-Once the bulk of the fire is extinguished, or the pumper runs out of water, shut down the deck gun
-If needed, move the pumper to the proper fire ground position(i.e., do not block truck access or position)
-Establish a water supply and supply hand lines as required.
Pg 47
164
Drafting: Which intake is ideal for a pumper?
side intake Pg 47
165
Drafting: What do you want to switch the pressure governor to??
Throttle rpm control mode Pg 47
166
Drafting: what do you want to increase the throttle to??
1000 to 1200 rpm or manufactures recommendation and engage primer Pg 47
167
Drafting: Once pressure develops on the master pump gauge, what are the next 2 steps?
Disengage the primer, and slowly open a discharge Pg 47
168
Drafting: While opening the discharge you may lose the prime, what are the steps you must follow to regain it?
Close the discharge and re-prime the pump Pg 47
169
As water leaves a nozzle under pressure, it causes a force in the opposite direction; this is called what?
Nozzle reaction
| Pg 48
170
Smooth Bore NR = ??
SB NR = 1.57 x d2 x NP
| Pg 48
171
Fog Stream NR = ??
Fog Stream NR = .0505 x Q x √NP
| Pg 48
172
Fog Stream NR = ??
Fog Stream NR = .0505 x Q x √NP
173
When hitting a hydrant, what is the recommended set up on the hydrant?
It is recommended that driver/operator connects two hydrant gates using 4" Storz couplings in the closed position tot the 2 1/2 spuds prior to charging the LDH supply line attached to the streamer.
Pg 49
174
What are the expected maximum flows that can be expected from a pumper at draft using the following inlets to the pump? Side intake? Rear intake? Front intake?
Side intake - 1750 gpm
Rear intake - 1500 - 1750 gpm
Front intake - 900 gpm
Pg 49
175
Any time incoming pressure exceeds 50 PSI, how should the pump be operated?
In Pump Gear Pg 50
176
For safety reasons, after a water supply has been established, the tank to pump valve shall be closed. How does this help the pump operator?
This enables the pump operator to immediately identify when a water supply is lost. Pg 52
177
Once the driver/operator has opened the tank to pump valve, what shall be notified?
they shall notify the interior crew and command that they are off of tank water Pg 52
178
What is hydraulics?
Hydraulics is the study of fluids at rest and in motion. In the fire service, the scope of this definition is limited to the study of water for firefighting purposes 
