AGRICULTURE
Measuring pumping เครื่องมือวัดความดันคือ for electric irrigation pumps
by Brenna ShumbamhiniJune 10, 2022
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If the incorrect pump is chosen or is worn out, this will increase pumping prices and scale back productiveness. In the second of a series of truth sheets, the NSW Department of Primary Industries describes a simple way to work out the pumping prices and vitality efficiency of your electrical pump.
Tests of irrigation pumps throughout New South Wales have discovered that many were not performing efficiently, both as a outcome of the wrong pump had been chosen for the job, or because the pump was worn.
To comprise costs, you need to monitor your vitality utilization, repair and keep the pump and work out what your pumping prices are.
When you have determined the working cost you’ll find a way to carry out fast checks to detect any change, and when you’ve determined the pump efficiency, you’ll find a way to examine it to the manufacturer’s figures to decide when repair or alternative is cost-effective.
Measuring operating prices
One way of tracking pumping prices is to work out how a lot it prices to pump a megalitre of water. To do that, you should measure:
The energy consumption fee in kilowatts (kW)
The circulate rate in litres per second (L/s).
Combining these measures with the price of electricity offers you the pumping cost.
Step 1: Measure the ability used
You can measure the power utilized by studying your electricity meter. Electronic meters are mostly used but single and a quantity of meters proceed for use on many farms.
Electronic meters
Electronic meters often measure and record the electrical energy used for the primary fee, shoulder price and the off-peak rate in separate registers. The numerous rates are switched ‘on’ and ‘off’ by the inner clock on the applicable instances.
Electronic meters document your electricity consumption in a time-of-use format. They may have registers for the date, the time and for testing the display.
Each register has a 3 determine identification quantity. For instance, the current off-peak kilowatts may be given register quantity ‘126’. You should check together with your local energy authority what the display register numbers are for each of your charges.
The meter scrolls by way of every register at 4 to six second intervals.
The register number seems, usually in smaller numbers, on the LCD display screen (in the diagram, within the top left-hand corner) and should have a short description beneath (for example: 126 = off-peak)
The usage in kilowatt-hours appears within the bigger main show. It is normally a six-figure quantity (for example: 1253.64).
When the time fee that is presently being measured is reached, the number may flash. Record this quantity. If none of the shows flash, document the readings from all of the shows.
Let the pump run for a minimum of 15 minutes before taking the following studying.
In methods that devour giant quantities of electrical energy, there may be a multiplier programmed into the electronics.
If so, it goes to be famous on the electrical energy supplier’s bill for this meter as ‘Mult’ or ‘M’ and the display could learn to a few decimal places. If there is a multiplier, run the pump for no less than half-hour before taking the second register reading.
If the second reading has not modified, you would possibly be studying the mistaken register.
Reading an electronic meter
First reading (register 126) = 1253.64 kWh
Second studying (register 126) = 1254.sixteen kWh
Multiplier acknowledged on power bill = 40
Power utilization =
Reading a disc meter
Note the rating determine, the revolutions per kilowatt hour (r/kWh), marked on the electricity meter.
R (r/kWh as marked on meter) = 266.6
Next, with the irrigation system set up in a median position and running, time the spinning horizontal disc on the power meter for a minimal of 10 per cent of R (In this instance, R is 266.6, so 10 per cent is about 30 revs).
N (number of disc revolutions) = 30 T (time of test) = 386 seconds
In systems that consume giant amounts of electricity, the disc could also be geared down so it doesn’t run too fast. If so, you will discover a multiplier ‘M’ is marked on the meter.
M (multiplier as marked on meter) = forty
From this knowledge you’ll find a way to calculate the power utilization in kilowatts.
Power utilization =
In this instance, the pump makes use of 42kW.
Perform this take a look at frequently, over a season or between seasons, to examine the pump’s energy consumption. If you discover that it takes much less time for the same number of disc revolutions than when you first tested the pump, the ability use is higher, and you will want to seek out out why.
This comparison is only potential when the irrigation is set up in the same position as the initial check, with the identical number of sprinklers, and with the pumping water stage roughly the same.
Multiple disc meters
If there are three meters, for example, one for every phase of a three-phase energy provide, measure the three meters individually and add the kW figures together.
Measuring each meter separately gives an accurate answer as hardly ever are three meters exactly the identical. If a very correct result’s needed, you have to monitor the system over all of the irrigation positions for one complete cycle.
In this case you have to record the total electricity used, the entire hours of use and the total quantity pumped over the interval.
Step 2: Measure the move rate (Q)
The second measure needed to calculate pumping price per megalitre is the flow fee of the system (Q).
The flow rate is the quantity (or quantity) of water pumped in a certain amount of time, usually given in litres per second (L/s). It must be measured after the system has had adequate time from startup to be running normally.
Measure the move fee by reading your water meter at the pump for ideally the whole irrigation cycle or a minimum of half an hour and dividing the litres pumped by the point in seconds.
Water meter studying at start: 1108.345 kL
Water meter studying after 35 minutes: 1230.a hundred forty five kL
Q =
Estimating move fee by discharge
If no water meter is fitted or it is shedding accuracy, the circulate fee of a sprig irrigation system where all the sprinklers are the identical mannequin and size can be estimated by measuring the sprinkler discharge. Use a quantity of sprinklers: no much less than one firstly of the road, one in the middle and one on the finish.
Record how long every sprinkler takes to fill a container (for example, a 10L bucket or a 20L drum). To find the move price of each sprinkler in litres, divide the container quantity (in litres) by the time required to fill it (in seconds).
You can then find the typical for the sprinklers you measured. To calculate the whole circulate rate of the system, multiply the typical by the number of sprinklers operating.
For example:
First sprinkler takes nine seconds to fill a 10L bucket = 10 ÷ 9 = 1.11L/s
Middle sprinkler takes eight seconds to fill a 10L bucket = 10 ÷ 8 = 1.25L/s
End sprinkler takes seven seconds to fill a 10L bucket = 10 ÷ 7 = 1.43L/s
Average circulate = (1.11 + 1.25 + 1.43) ÷ three
= 1.26L/s
There are 46 sprinklers working, so the entire move price is = 1.26 x forty six = 58L/s
Step three: Calculate the ability per megalitre pumped
From the facility usage and the flow rate, the kilowatt-hours per megalitre (kWh/ML) for your pump could be calculated.
This known as the ‘calibration’ worth (the worth used where no water meter is installed and electricity meter readings are learn to deduce the amount of water used).
Pump calibration (kWh/ML)
= kW ÷ (Q x zero.0036)
= forty two ÷ (58 x 0.0036)
= 201.1kWh/ML
(Note: 0.0036 converts kilowatt-seconds per litre to kilowatt-hours per megalitre.)
Step 4: Calculate the pumping value
Having calculated the facility used to pump a megalitre, if you know the fee per kWh, you possibly can calculate the value of pumping.
The costs per kWh could also be tough to work out exactly in case your supplier has completely different charges for day or night, weekends, and so forth so you must contact your provider for help to work this out.
Pumping prices
If provide costs 25 cents per kWh then:
Pumping price = 201 kWh/ML x $0.25
= $50.25 per ML
Measuring pump effectivity
Irrigation pump efficiency is a measure of how properly the pump converts electrical vitality into helpful work to move water.
The purpose of careful pump selection and common pump maintenance is to have the pump performing as efficiently as attainable (ie transferring probably the most water for the least power required). Efficient pump operation minimises operating costs per megalitre pumped.
Pump efficiency of 70 per cent to eighty five per cent ought to be achievable in most circumstances. An acceptable minimal for a centrifugal irrigation pump is sixty five per cent, and 75 per cent for a turbine pump.
An effectivity figure below these means both the wrong pump was chosen for the job, the pump is worn and needs restore or upkeep is required.
The key to containing your pumping costs is to regularly monitor your vitality utilization and verify on any significant change that means attention is needed.
To calculate pump efficiency, you want to know the flow fee (Q) and the pump stress, or total head (H or TH) of the system. The strain and circulate that a pump is working at is called the duty or duty level. Pump effectivity varies over the vary of possible duties for any specific pump.
An enough estimate of total dynamic head for floor techniques is the vertical peak in metres from supply water degree to the tip of the discharge pipe, or, if the discharge is submerged, to the peak of the water above the discharge, that is, water degree to water stage, plus the losses due to friction in the suction pipe.
Measure the discharge (or delivery) head
This is the pressure learn from the gauge fitted on the pump when the system is at full operating strain. This reading needs to be transformed to equal metres of head, this is also generally referred to as Pressure Head.
New pumps usually have a pressure gauge put in but they often suffer bodily injury shortly. A better method is to suit an entry level on the supply side of the pump where you can quickly install a strain gauge everytime you want to take a reading. The gauge may be simply detached when not needed.
A change in the pump operating stress through the season or throughout seasons, when irrigating the identical block or shift, immediately tells you something has changed.
A sudden reduction usually signifies a new leak or a blockage on the suction facet; a gradual discount normally indicates wear of the impeller or sprinkler nozzles; and a rise usually suggests a blockage someplace in the system downstream of the pressure gauge.
Pressure could be thought of as equal to a pipe of water of a certain height in metres. This is known as ‘head’ (H). At sea degree, the strain on the bottom of a pipe of water 10m high is about a hundred kilopascals (kPa).
If your stress gauge reads solely in psi, convert to kPa by multiplying by 6.9.
For instance: 40 psi = 40 × 6.9 = 276k Pa = 27.6 m head
Determine the suction head
Suction head is the distance between the centre line of the pump and the supply water degree, plus losses in the suction pipe if the pump is positioned above the water stage. Typical suction head figures for centrifugal pumps are three to five metres.
Most problems with pumps positioned above the water stage occur within the suction line, so ensure every little thing appropriate. Common issues embrace blocked inlet or foot-valve or strainer, pipe diameter too small, pipe damaged or crushed, suction top too nice, or air trapped at the connection to the pump.
Turbine and axial move pumps have to be submerged to function, in order that they normally don’t have any suction head.
For example:
Pressure Head = 27.6m
Suction head = 4.0m
Total Head = 31.6m
Another useful determine that can now be calculated is the pumping price per ML per metre of head. This allows a meaningful comparability between different pump stations.
Pumping price per ML per metre head: = price ($/ML) ÷ TH (m)
= $50.25/ML ÷ 31.6m
= $1.fifty nine / ML / m head
Step 6: Determine motor efficiency (Me)
Electric motors have an efficiency worth. That is, they lose a variety of the energy going into them as heat. This energy loss changes with the dimensions of the motor. The desk under is a suggestion for motors working at full load.
Submersible motors lose about 4 per cent more than air-cooled electric motors (for example, where Me is 88 per cent for an air-cooled motor it might be eighty four per cent for a submersible). Voltage losses through long electrical cables may be important so this must be checked with an electrical engineer.
Step 7: Determine transmission losses (Df)
If the engine isn’t directly coupled to the pump, there is a loss of energy through the transmission. This loss is taken into account by what’s termed the drive issue (Df).
Step 8: Calculate pump effectivity (Pe)
Pe = (Q × H) ÷ (power consumed × Me × Df)
This instance includes the data from the earlier steps discussed. The drive from the motor to the pump is a V-belt on this case.
Pe (87a03eb4327cd2ba79570dbcca4066c6d479b8f7279bafdb318e7183d82771cf) = (Q × H) ÷ (power × Me × Df)
= (58 × 31.6) ÷ (42 × zero.9 × 0.9)
= 1832.eight ÷ 34.02
= fifty three.9 per cent
Step 9: Calculating potential financial savings
Most centrifugal pumps are designed to operate with a minimal of 75 per cent efficiency, and most turbine pumps are designed to operate with a minimal of eighty five per cent effectivity.
The pump in our example is only about fifty four per cent efficient, so how much would be saved by improving the efficiency from fifty four per cent to seventy five per cent?
Take this example:
If our pumping value is $50.25 per ML, the development is calculated as follows:
Cost saving per ML:
= $50.25 – (50.25 x (54 ÷ 75))
= $50.25 – (50.25 x zero.72)
= $50.25 – 36.18
= $14.07
If 900ML are pumped during a season, the whole price saving is $14.07 × 900 = $12,663.
If impeller wear is the issue and the price of alternative is $10,000, it would be paid for in lower than one season. After that, the savings are all elevated revenue.
Notice that a discount within the pump efficiency determine of 21 per cent (75 per cent to fifty four per cent) causes a rise in pumping price of 39 per cent ($36.18/ML to $50.25/ML).
Other elements that affect value and pump efficiency
There are two other variables have an effect on price and pump effectivity: pump velocity and impeller size.
Pump speed
You should know the pump pace in order to learn the pump curves. The curves are often prepared for particular pump speeds and impeller sizes.
If the pump is directly coupled to the electrical motor, the velocity is mounted by the pace of the motor: two-pole motors run at 2,900 rev/min and four-pole motors run at 1,440 rev/min. However, as a end result of the pace of electric motors varies somewhat, it will be good to examine your motor speed with a rev counter.
If the motor isn’t instantly coupled to the pump, the speed is altered by the gearing ratio of the transmission. Gear drives usually have the ratio stamped on the identification plate.
The ratio for a V-belt and pulley drive may be calculated from the diameter of the pulleys on the motor and the pump (see the diagram under – ensure the pump is stopped earlier than measuring the pulleys).
A complication that can happen when figuring out the fee and effectivity revolves round Variable Speed Drives (VSD), also called Variable Frequency Drives (VFD).
VSDs have gotten more and more well-liked as their price reduces because of the benefits they provide. These units are added to electric motors and allow the pace to be altered by changing the frequency of the alternating present. They enable electrically pushed pumps to have their speed set at exactly what is required for the pump responsibility and they remove the necessity for throttling the irrigation system using valves.
Savings of one quarter of the similar old power consumption are sometimes reported by irrigators, and could also be as a lot as half relying on the scenario. For determining the cost and efficiency of a pump, the measurements outlined on this article ought to be made a quantity of occasions with the pump set at different typical speeds.
Impeller size
Impeller put on has the same impact as a reduction in impeller dimension so you have to know the dimensions of impeller fitted to your pump to work out which efficiency curve applies to your pump.
Sometimes the impeller measurement is stamped on the pump’s ID plate. If not, you should discover out the size by dismantling the pump and measuring it, or asking the person who made the change.
Sometimes an impeller is intentionally reduced in diameter to adjust the pump’s performance and acquire a particular duty.
To give a variety of duties, producers may supply impellers of various diameters for the same pump casing. Available impeller sizes are proven on the pump curves.
Power factor
Power issue may also substantially affect your operating costs and perhaps the operation of your pump as properly.
Measuring efficiency
Keeping observe of your pump’s performance and prices just isn’t troublesome. It may save you some big cash and hold your irrigation system performing correctly.
If you identify your pump is operating below the acceptable minimum stage, check the internal condition for wear or maintenance and the suitability of the pump for its current responsibility, or take steps to enhance the drive or replace it with a VSD.
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