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67 Cards in this Set
- Front
- Back
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Automatic Valve |
(automatic control valve) a valve which is activated by an automatic controller by way of control lines. Sometimes called a remote control valve. Two types of automatic valves are: Electric (normally closed) and Hydraulic (normally open)
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Backflow prevention device
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a device which prevents water from being drained or sucked back into the water supply lines from an irrigation line. Common types include:
atmospheric vacuum breaker double check valve dual check valve pressure vacuum breaker reduced pressure back flow prevention assembly (used to protect water system from highly hazardous substances) |
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Check Valve
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a valve which permits water to flow in one direction only, using a weight or spring tension to remain closed against reverse flows.
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Class (of pipe)
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a method by which pipe is grouped according to the working pressure at which it can be used. (ex. class 160 pipe can be used where the working pressure does not exceed 160 psi)
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Gate Valve
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a valve used to manually cut off the water supply
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What is the standard measurement of flow in irrigation design?
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GPM gallons per minute
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What is the standard measurement of flow in drip or trickle irrigation systems?
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GPH gallons per hour
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Lateral line
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a pipe which branches off from the main line to supply water to a zone. The lateral is often, but not always, smaller than the main.
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Loop
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A piping method which allows more than one path for the water to flow from the supply to the demand.
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Main line
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A large pipe designed and sized to carry water from the supply point to the lateral lines or zones. In most systems the main line is always under pressure.
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How is sprinkler overlap expressed?
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overlap is the amount one sprinkler's pattern overlaps another's. Expressed as a percentage of the radius by the spacing (e.g. 40' radius, 50' spacing=80% overlap)?? not sure if right???
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What does P.E.T stand for with regards to irrigation?
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Potential evapotranspiration: it is the max. average rate of water use (estimated) for plants in a give climate. The PET considers temperature and humidity levels during the summer.
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Pressure
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the force of water measured in pounds per square inch (psi) or foot head.
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Pressure loss
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the loss of pressure under flow conditions caused by friction or elevation
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Pressure Regulator
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a device which controls the available pressure to a pre-set max under static or flow conditions. Pressure regulation is a feature on many automatic valves and may also be achieved by separate devices installed in the system. Excessive pressure may damage piping and cause sprinklers to fog (atomize)
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PVC Pipe
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Polyvinyl chloride pipe.- a common pipe material for irrigation systems. it is light weight, durable, inexpensive and uses external solvent -weld fittings. All classes and schedules of PVC pipe have uniform outside dimensions to facilitate the use of common fittings.
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Rate of application
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aka precipitation rate: the rate at which water is applied to the landscape area by the sprinklers in a zone. Measured in inches/hour
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Static pressure
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the pressure of water when it is not moving.
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Velocity of Water
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the speed at which water travels in the piping system. to avoid excessive friction loss (pressure loss) pipe velocities should not exceed 5 fps (feet per second)
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Working pressure
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the actual pressure available at any given point when the system is in operation, usually taken at the base of the sprinkler head.
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What is hydraulics?
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The study or the behaviour of fluids both at rest and in motion.
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What is the equation for water pressure?
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P=F/A
P= Pressure (psi) F= Force in lbs A= Area in sq. inches Force is the weight of the water above the point where it is being measured. When the area is constant (1 sq. in) the force is dependent on the height of the water. The greater the height the greater the weight or force. |
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What is the weight of water?
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8.3 lbs/gallon
62.4 lbs/cf 0.036 lbs/cu.in. |
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What is the pressure on the surface of a container 1 sq. in. in area filled to a height of 12 in?
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P=0.036 lb/ci x 12 cu. in./1 sq in.=.433psi
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What is the relationship between pressure and elevation called?
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feet of head. 1 foot head=.433psi
One psi=2.31 feet of head |
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In what two ways is static water pressure created?
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1. elevating the water in tanks, reservoirs, etc
2. by a pump forcing water into a pipe. |
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What are the two types of irrigation systems?
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Sprinkler and Drip/Trickle
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What is the most efficient way to lay out sprinkler head spacing?
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Triangular spacing
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Describe the drip/trickle system of irrigation.
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susceptible to clogging, require filters in system.
More efficient water use than sprinklers Measured in GPH More difficult to determine if a problem exists |
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What is the min size for direct burial wiring of electrical systems?
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No. 14 guage.
Smaller wire diameter, the greater the voltage loss Wires smaller than No. 14 are susceptible to damage and shorting out. Max length=7500 linear feet. |
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What is the standard tubing size for hydraulic systems?
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1/4". Systems are normally open, so if tubing is cut, the valve will remain open.
1000ft MAX recommended run. |
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The precipitation rate of an irrigation system is measure in units of?
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in/hr
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A zone in your irrigation system is covered by quarter, half and full circle heads with matched precipitation rates. if the head spacing is 12.5' x 14' and a full circle in the zone distributes 3.5 rpm, what is the precipitation rate of the zone?
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1.925 in/hr
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How is precipitation rate calculated?
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Total Area Method Formula:
Pr = 96.25 X Total GPM/Total Area Pr - Precipitation rate in inches per hour. 96.25 - A constant that converts gallons per minute (GPM) to inches per hour. It is derived from 60 minutes per hour divided by 7.48 gallons per cubic foot. times 12 inches per foot. Total GPM - The cumulative flow from all sprinklers in the specified area, in gallons per minute (refer to sprinkler charts) Total Area - The area being irrigated, in square feet. |
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At 60 psi, 80gpm flowing in a 2 inch, class 200 PVC pipe will lose how many psi per 100ft?
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4.10 (check manufacturers table for friction loss?)
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If the static pressure on a site is 120 psi, what size should the water meter be to handle a flow of 78 gpm?
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2"
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a small rectangular area on a project site will be covered by 4 irrigation heads, each throwing a 1/4 circle arc pattern. If each head has a flow of 3.5 gpm, and the size of the area is 32'x35', what is the precipitation rate of this area?
If the are needs 1.5in/wk of water, how long must the heads in that zone run if operated 4 times/wk? |
1.20 in/hr
18.75 minutes |
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The velocity in a pipe is measured in..
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ft/sec.
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The available water supply to an office building is 90gpm at 80psi static pressure. What is the max amount of flow you would design the system to have an any one time?
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67.5gpm
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The rule of thumb for specifying an automatic valve or meter is to size the device so that no more than ____psi is lost.
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5
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The water main on a street in front of a residence has a static pressure of 85 psi and an available flow to site of 58gpm. What is the largest flow allowed on an one zone?
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43.5gpm
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The rule of thumb for calculating pressure loss to your critical head is to total all of the friction loss through the pipes, meter, valves, etc and add ____% to account for the loss through these fittings.
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10
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The loss of water pressure in a system due to friction is measured in units of _____
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lbs/sq. in.
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How much water will soil typically accept per hour before runoff occurs?
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1/3inch (8mm)
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What is the objective of a conventional sprinkler system?
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to apply water at a rate that the soil can accept, without causing runoff.
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List three plants that prefer to be watered from an overhead system.
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Azaleas, rhododendrons and camellias
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What are the two categories of drip system emitters?
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1. Compensating emitters: designed to compensate for pressure differences and will emit a predetermined amount of water through each emitter a uniform rate within a particular pressure range.
2. Non-compensating emitters: release a set amount of water at a given pressure. |
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Each foot of elevation change creates what amount of change in irrigation water pressure?
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0.433 psi (2.986kPa)
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In piped irrigation systems, what are the units for:
1. hydraulic pressure 2. velocity 3. flow |
1. psi
2. fps 3. gpm |
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What is the max velocity of water recommended for irrigation?
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5 fps
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What is a main concern when sizing valves?
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determining how much pressure (friction loss) can be lost while still achieving the desired working pressure at the last sprinkler head. **common to use a valve smaller than downstream pipe, which keeps pipe velocities under 5fps.
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What are the two PVC pipe designations?
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1. Schedule pipe- means the wall thickness is the same as in steel pipe at the same schedule and pipe size. (used primarily for precut threaded nipples for sprinkler risers and shrub beds)
2. Class pipe: designated by pressure ratings |
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What is PE pipe?
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Polyethylene pipe - easily pulled into ground, very flexible, great for cold climates because not as subject to damage from freezing.
uses internal barbed fitting, resulting in flow characteristics worse than PVC |
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When is copper pipe usually used?
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Type K copper pipe, thickest of all copper pipe sizes. Used when pipe is exposed to sunlight.
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Why isn't galvanized steel pipe used very often in irrigation?
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it is highly susceptible to deterioration caused by minerals in the water.
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What are the two categories of backflow preventors?
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Anti-siphon devices and back-pressure devices.
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What legislation requires backflow preventors to be installed when working with potable water?
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Clean Water Act.
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What is the rule of thumb when designing drip irrigation?
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always design water applications so that at least 50 percent of the plant root zone will be wet.
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What are the 4 basic guidelines for drip irrigation systems?
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1. Lateral lengths should not exceed 200ft.
2. Flow should not exceed 3.33gpm 3. Max working pressure should be 40 psi (pressures over this amount should be regulated) 4. Line used should be 1/2inch PVC or polyethylene tubing |
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What is the minimum recommended depth for protection from pipes and frost damage?
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3 feet.
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What is the rational method formula?
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q=CiA; used to predict the size drainline needed to drain a give area by generating a prediction of HOW MUCH runoff will be generated by a specific storm event of a give duration.
q= Quantity of runoff in cu. ft/sec C= Runoff coefficient i= Intensity of rainfall in in/hr A= Area in acres |
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What are the roughness coefficients for the following pipes?
1. concrete 2. cast iron 3. corrugated metal 4. plastic (smooth) 5. vitrified clay |
1. concrete 0.012
2. cast iron 0.013 3. corrugated metal 0.024 4. plastic 0.012 5. vitrified clay 0.010-0.015 |
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What is q(p)?
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The peak rate of runoff
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What does Manning's equation describe?
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Uniform flow in a conveyance to which runoff is delivered at a steady rate and where the size, shape, gradient and direction of the conveyance are uniform along its length.
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What is Manning's Equation?
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V=(1.49/n)R^.67 x G^.5
V=velocity (fps) n=roughness factor (no units) R= hydraulic radius (A/Wp) or r/2 for full circular pipe G= slope along conveyance length |
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What is the equation for Rate of Flow?
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V=q/A
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What is the typical required velocity range for pipes?
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2-5 fps. velocities lower than 2fps will result in sedimentation.
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