Selecting the Right Pump
Diaphragm Pumps (positive displacement)
Diaphragm pumps are designed to isolate abrasive and corrosive solutions being pumped from its
mechanical drive components through the use of synthetic diaphragms.
Diaphragm pumps are compact, self-priming and produce low-to-high pressures 0 to 725 psi
(0-50 bar) with flow rates of 3.8 to 65.7 gpm (14.5 -260 lpm). Driven by 540 rpm PTO, gas engine,
or hydraulic motor, diaphragm pumps are used for a variety of agricultural, horticultural and pest
control spraying applications.
SHURflo pumps are efficient, 12 VDC electric motor driven low pressure diaphragm
pumps designed for smaller spray applications with pressures 0-150 psi (0-10 bar)
and flows 0-5.3 gpm (0-20 lpm). SHURflo pumps fit uniquely into mobile applications
on ATV, home lawn care, fertilizer and pesticide equipment.
Roller Pumps (positive displacement)
The Hypro line of roller pumps are
an economical choice by farmers
throughout the world. The rollers
revolve inside the pump housing on
an eccentric profile to force spray
solution through the pump which then
develops pressure and flow. The roller
pump offers a compact design with
mechanical simplicity to provide a low initial cost pump that
is extremely versatile. They operate efficiently at PTO speeds
of 540 and 1000 rpm and have a wide pressure range of up to
300 psi (20 bar) and flow rates of 2 to 62 gpm (7 to 235 lpm).
Roller pumps are self-priming and easily adapt to PTO or gas
engine drives. Specific seal, roller and casting materials can
be selected for compatibility with certain herbicides, pesticides, fungicides and fertilizers.
Piston and Plunger Pumps (positive displacement)
Piston/Plunger pumps have a shaft, pistons or plungers and “inlet” and “outlet” poppet valves. The
design of the pump converts the rotational drive into a oscillating vertical motion. On the downstroke, the inlet valve opens, filling the chamber with solution. On the up-stroke, the outlet valve
opens, and the piston forces the solution to the nozzle. Piston pumps deliver relatively low flow
rate, less than 10 gpm (40 lpm), at pressures up to 1000 psi (69 bar). Plunger pumps are designed
with ceramic plungers which can operate at higher pressures up to 2000 psi (138 bar) at flows up
to 4 gpm (15 lpm). The main difference of construction is in a piston pump the sealing material
moves with the piston while in a plunger pump the sealing material (u-cups) are stationary with only
the plunger in motion. The replaceable piston cups can be of leather, fabric or Buna-N rubber, depending on the type of
solution to be sprayed. They can be driven by 540 rpm PTO, gas engine, hydraulic or electric motor. Their low volume/ high
pressure capability permits use in general spraying as well as task-oriented applications such as spraying fence rows and
ditches, and hydrostatic testing. Plunger pumps are used primarily for cleaning operations.
3
Selecting the right pump
Selecting the Right Pump
Selecting the Right Pump
2. Pump Drives
How a pump is to be driven is often a primary consideration in selecting the proper type of pump. If the power source has
already been determined, the following chart may be of further help in selecting the type of pump that is best suited to your
needs.
How do you plan to drive the pump?
If your power source is:
Roller
direct coupled:
540 rpm PTO
X
through gear drive:
X
through belt/pulley:
X
direct coupled:
1000 rpm PTO
Centrifugal and Transfer
X
X
X
X
X
X
X
X
X
X
X
X
X
X
through belt/pulley:
X
12 Volt DC Motor
X
Electric Motor
Piston/Plunger
X
through gear drive:
Hydraulic Motor
Gas Engine
Diaphragm
X
direct coupled:
X
through gear reduction:
X
X
through belt/pulley:
X
X
direct coupled:
X
X
through belt/pulley:
X
X
4
3. Flow and Pressure Requirements
Pump pressure required is often dependent on the application. Whether it be low pressure band spraying or high pressure
tree spraying, it is the application that dictates what pressure is needed to get the right performance at the spray nozzle. Once
you know what pressure is desired choose a pump with extra pressure capacity due to losses in pressure as it goes through
the system components (strainer, valves, elbows, hose, etc.) out to the nozzle.
How Much Pressure Do You Need?
Pressure
Flow
0-150 psi (0-10 bar)
Pump
0-1078 gpm (0-4080 lpm)
0-150 psi (0-10 bar)
0-5 gpm (0-20 lpm)
0-300 psi (0-20 bar)
0-60 gpm (0-225 lpm)
Roller
0-725 psi (0-50 bar)
0-60 gpm (0-225 lpm)
HYPRO Diaphragm
0-1000 psi (0-69 bar)
0-10 gpm (0-38 lpm)
Piston/Plunger
0-1000+ psi (0-69+ bar)
0-4 gpm (0-15 lpm)
Plunger
Centrifugal
SHURflo Diaphragm
Pump flow required is dependent on several factors. Application rate, width of boom or size of nozzle, speed of travel and
agitation. To review your pump flow requirements follow through the calculations presented on the following pages. As
with pressure you will want to choose a pump that has additional flow so that it meets your application needs over time as
performance drops due to component wear.
How Much Flow Do You Need?
Flow
Pressure
0-4 gpm (0-15 lpm)
0-1000+ psi (70+ bar)
0-5 gpm (0-20 lpm)
0-150 psi (0-10 bar)
SHURflo Diaphragm
0-10 gpm (0-38 lpm)
0-1000 psi (0-70 bar)
Piston/Plunger
0-60 gpm (0-225 lpm)
0-300 psi (0-20 bar)
Roller
0-60 gpm (0-225 lpm)
0-725 psi (0-50 bar)
HYPRO Diaphragm
0-1078 gpm (0-4080 lpm)
0-150 psi (0-10 bar)
5
Pump
Plunger
Centrifugal
Selecting the right pump
Selecting the Right Pump
Selecting the Right Pump
Determining Pump Flow and Pressure Requirements
Every pumping task has an optimum volume and pressure requirement. Determining that optimum (and selecting the pump
that delivers it) is key to an efficient and economical spraying system operation.
Pressure requirements for agricultural pumps are dependent on both the material to be applied and application targets. Soilapplied herbicides generally require a relatively low pressure pump rating of 30-60 psi with foliar-applied herbicides at the
top end of that range and slightly higher. Insecticides and fungicides can require higher pressure ratings of 100 to 500 psi.
Pressure must be sufficient, in the case of heavy foliage field crops and orchard crops, to penetrate the leaf foliage. In the
case of orchard crops, pressure must also be sufficient to carry material up and over as well as into the canopy.
A number of factors must be considered to properly determine the total flow you will need from your pump. They
include:
- Type of spray operation (broadcast, banding, low-level, etc.)
- The chemical’s application rate, ground speed, boom width, hose length, tank agitation, etc.
The spray task is the first consideration in determining flow rate and pressure needs. The following formulas and
calculations may help.
Calculating agitation requirements
The pump must produce enough flow for both the application rate and tank agitation requirements. Too little
agitation will not keep the solution in proper suspension and too much agitation may cause foaming. Here are rule of thumb
formulas for calculating how much additional pump flow you will need for agitation.
Liquids:
Tank volume (gallons) x .05 = total agitation in gpm
or Tank volume (litres) x .05 = total agitation in lpm
Wetable Powders and Flowables:
Tank volume (gallons) x .125 = total agitation in gpm or
Tank volume (litres) x .125 = total agitation in lpm
EXAMPLE: If you will be spraying a wettable powder from a 100-gallon tank, proper agitation will require 12.5 gpm
additional flow from the pump.
Reducing agitation flow requirements
Agitation flow requirements can be reduced by using jet agitation in the tank. Jet agitators use a venturi design to
multiply agitation output. Depending on the jet agitator model and pressure, one gallon per minute input can provide two
to ten gallons per minute agitation output. If your sprayer is equipped with a jet agitator, consult the operator’s manual or
documentation to find the output to input ratio and adjust your flow required for agitation accordingly.
Agitation Flow with Jet Agitation:
required gpm x input
or
output
required lpm x input
output
For example: If you calculate a requirement of 63 gpm of agitation and your jet agitator produces 3 to 1 output to input ratio,
your pump would only need 1⁄3 of 63 gpm, or 21 gpm.
6
Factor in an “Excess Flow” Requirement
It is wise to have some excess flow capacity so you will not end up with an undersized pump because actual operation
conditions may cause changes in spray system performance (such as normal pump wear, operating at less than rated speeds,
etc.). Hypro recommends you add an additional 20% to your calculated total pump flow requirement to compensate for these
variables. Plumbing systems have a number of restrictions that will result in a pressure drop from the pump to the actual
spray point. These must be taken into account and minimized.
Calculating pump flow for broadcast boom sprayers
Chemical application is measured in gallons per acre (gpa) or litres per heactres (l/ha), whereas pump flow is stated in
gallons per minute (gpm) or litres per minute (lpm). To calculate the pump flow required by a broadcast boom sprayer,
multiply the application rate (from the chemical label) by the sprayer ground speed. Multiply the sum by the boom width on
your sprayer. Then, divide that number by 495 for US units or by 600 for metric units. As a formula, it is written like this:
Flow required for boom:
gpm = gpa x mph x boom width (ft.)
or
495
lpm =
l/ha x km/hr x boom width (m)
600
The result will be the pump flow required to deliver the proper application rate at the boom’s nozzles. Then calculate your
total pump flow requirement (broadcast):
Flow required for boom:
gpm Flow required for boom:
lpm
Flow required for agitation: +
gpm Flow required for agitation: +
lpm
Sub-total =
gpm
=
lpm
Excess flow requirement: x
TOTAL PUMP FLOW NEEDED:=
or Sub-total 1.20 Excess flow requirement: gpm TOTAL PUMP FLOW NEEDED:
x
1.20
=
lpm
Calculating pump flow for banding sprayers
First, multiply the band width by the number of rows to determine the total width (w). Then, multiply the application rate (from
the chemical label) by the ground speed. Multiply that result by the total width (w) calculated earlier, then divide the result by
5940 for US units or 60,000 for metric units. Here’s how the formula appears:
Total band width of sprayer:
w = rows x band width (inches) or w = rows x band width (cm)
Flow required for banding nozzles:
gpm = gpa x mph x w or 5940
lpm =
l/ha x km/hr x w
60,000
The result will be the pump flow required to deliver the proper application rate at the boom’s nozzles. Then calculate your
total pump flow requirement (banding):
Flow required for boom:
gpm Flow required for boom:
lpm
Flow required for agitation:
+
gpm Flow required for agitation:
+
lpm
Sub-total
=
gpm
or
Sub-total
=
lpm
Excess flow requirement:
x
TOTAL PUMP FLOW NEEDED: =
1.20 Excess flow requirement:
gpm TOTAL PUMP FLOW NEEDED:
7
x
1.20
=lpm
Selecting the right pump
Selecting the Right Pump
Selecting the Right Pump
Calculating pump flow for hand gun spraying
For low-level spraying with a hand gun, such as for lawn and turf care, professional applicators typically “walk” the
lawn at about 1,000 sq. ft. per minute or 100 sq. m per minute. That means the “gpm” or “lpm” rate of the hand gun will
generally be the same as “gallons per 1,000 sq. ft.” or “litres per 100 sq. m.”
To determine your total pump flow requirement:
Flow required for gun/nozzle: gallons per 1,000ft2 (same as gpm)
Flow required for agitation: + gpm
Sub-total = gpm
Excess flow requirement: x
1.20
TOTAL PUMP FLOW NEEDED: = gpm
or
Flow required for gun/nozzle: Litres per 100 m2 (same as lpm)
Flow required for agitation: + lpm
Sub-total = lpm
Excess flow requirement: x
1.20
TOTAL PUMP FLOW NEEDED: = lpm
Use this same method for calculating the pump flow requirement for high pressure spraying, such as trees. Even though the
application “rate” is usually a visual saturation of the tree, the known gpm or lpm factor will be the hand gun nozzle output,
which is the rate you use for the calculation.
Calculating pump pressure for hand gun spraying
For most hand gun chemical spraying, 40 psi (3 bar) at the nozzle is typical. To properly select a pump that can deliver the
right nozzle pressure, you must consider the normal “pressure drop” that occurs within the length of hose. The amount of
pressure drop through the hose depends on hose length, hose diameter and flow rate. For example, 300’ (90 m) of 1⁄2” hose
spraying at 6 gpm (23 lpm), will have a pressure drop of approximately 120 psi (8 bar). That means you need a pump delivering
at least 160 psi (12 bar) in order to ensure 40 psi (3 bar) at the nozzle.
Desired pressure at gun nozzle: psi
Hose pressure loss:
+
psi
TOTAL PUMP PRESSURE NEEDED: = psi
or
Desired pressure at gun nozzle: bar
Hose pressure loss:
bar
+
TOTAL PUMP PRESSURE NEEDED: = bar
NOTE: When determining the total pump pressure requirement for high tree spraying, you must also consider the spray
height (or reach) you need to attain. Generally, pumps of up to 700 psi (50 bar) are used for this purpose.
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