Sprayer

What is spraying?

Spraying consists of spreading a liquid in the form of droplets, the size of which is adapted to the work objectives. The smaller the droplet size, the greater the coverage. The risk of droplet drift and/or evaporation also increases with droplet fineness.
Vineyard spraying differs greatly from field crop spraying, partly because of the diversity of vineyard management methods, but also because of the different objectives of the work to be carried out. The main tasks are

Wood treatments outside the vegetative period (now virtually non-existent since the ban on sodium arsenite in November 2001)
Cover treatments
Localised treatments in the fruit-bearing zone

Memo on good sprayer maintenance practices

Sprayer in the vineyards

Spraying technologies

There are three main spraying technologies used in viticulture:

the projected jet (mainly used for weed control),
airblast
pneumatic (both used for general coverage treatments).

The different types of sprayer have a number of features in common.
In chronological order of progression of the liquid in the sprayer, we find :

The tank
The filter (suction)
The pump
The regulator
Distributor(s)
Boom sections
Filter(s)
Nozzles or pellets

Common sprayer components

Components of a sprayer

Chassis, tank and axle

The chassis

Generally of welded design, the chassis of a vineyard sprayer is made up of a "U" or "tube" section. The U-section offers a number of advantages, in particular resistance to corrosion

When the chassis is made up of a "tube" section, it is important to ensure that the ends of the chassis are sealed to prevent internal corrosion.

The coupling system

There are 3 main types of hitch.

Mounted

the sprayer is hitched to the tractor via the lifting arms. This configuration is generally preferred when a small volume of spray liquid needs to be loaded or when manoeuvres at the end of the row need to be carried out in a confined space.

Mounted sprayer (on the 3-point linkage) - Nicolas

Semi-mounted

the sprayer consists of 2 assemblies. The first is attached to the tractor via the lifting arms. It includes the pump, regulation, ventilation and spray boom. The second comprises the tank, which is pulled by the first assembly.

Semi-mounted sprayer (3 points + hitch) - Clemens

Trailed

this is the most common configuration. Generally attached to the tractor via a bar with holes on the lifting arms, manufacturers now offer an interface. This stabilises the unit and allows the linkage to rotate on 2 axes.

Trailed sprayer (hitch) - Nicolas

The tanks

The main tank is the spray liquid reservoir. A second tank contains the water needed to rinse the circuits and dilute the tank contents. Finally, a third tank is used for rinsing hands and/or nozzles.

They are generally made of polyethylene or laminated polyester , but you can also find 'home-made' tanks in stainless steel, mainly on high-clearance tractors when you're looking for a 'made-to-measure' solution.

Materials	Advantages	Limitations
polyethylene	▪ Easy to clean ▪ Resistant	▪ Difficult to repair
polyester laminate	▪ Easy to repair	▪ Internal roughness makes cleaning difficult ▪ Sensitive to shock and vibration

Note: The different tank volumes

Tanks generally have a capacity of between 300 and 2000 litres.
When we talk about vat volume, we need to distinguish between nominal, total, dilutable residual and total residual volume.

Nominal tank volume
maximum capacity of the vat.

Total tank volume
nominal volume + 5% safety volume

Dilutable residual volume
volume of liquid remaining in the bottom of the tank after the pump has been de-primed + in the tank return circuit + in the compensated returns + in the filters + in the agitation system + in the pipes of any product incorporation tank.

Total residual volume
dilutable residual volume + volume of spray liquid remaining in the pipes from the tank to the diffusers.

+ The volume of the rinsing tank must be at least equal to 10% of the volume of the main tank.

The axle

There are three types of axle on the market:

Single axle
Double axle
Bogie axle

The choice of axle type is based on various objectives:

volume to be loaded
stability required during treatments
limiting soil compaction.

The positioning of the axles on the chassis is important. They must provide good weight distribution while limiting rear offset.
Double or bogie axles offer good stability during spraying operations, limiting pressure on the ground and, consequently, soil compaction. On the other hand, they have the disadvantage of reducing the turning radius.

The pumps

These are the heart of the sprayer. The pumps move the liquid not only for spraying but also for agitation in the tank. They are characterised by a characteristic curve that represents the pump's ability to move the spray liquid as a function of the required pressure.

Table of pressure and sprayer output

CAUTION: a pump rated at 60 litres per minute (often at a PTO speed of 600 rpm) will only deliver this flow rate at atmospheric pressure. An increase in working pressure causes a reduction in flow, which can be very significant. Centrifugal pumps are the most sensitive to this phenomenon, while piston pumps are the least sensitive.
Although there are a few centrifugal pumps, the vast majority of pumps used are of the piston-diaphragm type.

There are several types of pump on the market:

Centrifugal pumps

These are relatively simple in design. They have the distinctive feature of delivering high flow rates at low operating pressures. This type of pump is non-volumetric and tends to deflate easily.
How a centrifugal pump works:
The liquid is drawn in at the impeller shaft. The liquid flows through the impeller at high speed. The centrifugal force sends the liquid towards the discharge, causing it to acquire kinetic energy, which is converted into pressure.

Piston pumps

Piston pumps are used on many sprayers because they offer a wide range of working pressures. However, the complexity of design and the cost (purchase and maintenance) mean that these pumps are being abandoned in favour of piston diaphragm pumps.
How a piston pump works:
The piston moves in a straight line with a reciprocating motion in order to pressurise the liquid. A suction valve and a delivery valve allow the liquid to enter and leave the pump. To regulate the flow, the pump is fitted with an air bell to smooth out the pressure (clipping low and high pressures).

Piston diaphragm pumps

These are used on most sprayers. Their design limits maintenance costs, as the liquid is no longer in contact with the pump's components. However, these pumps do require minimum maintenance (checking diaphragms, valves and oil level).
How a piston diaphragm pump works:
The piston is framed by two diaphragms. The reciprocating movement of this piston is in phase with the suction or discharge diaphragms. A suction valve and a discharge valve allow the spray liquid to enter and exit the pump. Like piston pumps, they are generally combined with an air bell.

The air bell

Air bell

This accessory is fitted to piston or diaphragm pumps. It is used to limit pulsation in discharge circuits. The air bell is essential on two-piston diaphragm pumps.

The internal pressure is determined by the working pressure. Generally, it varies between ½ (for "low" pressures) and 1/3 (for "high" pressures) of the working pressure.

Filters

The filtration system must comprise several filters:

the first filter (sieve) is located at the manhole. It is used to retain coarse elements such as lumps formed during poor preparation of the spray liquid
a filter protecting the pump, located between the tank and the pump
the second level of filtration is located between the pump and the control system. This level of filtration is optional.
a third level of filtration is positioned after the section cut-off valves and the nozzles
finally, a last level can be positioned just before the diffusers (nozzle filter)

Sprayer filling sieve

The fineness of filtration is indicated by the number of meshes, which corresponds to the number of wires per inch (1 inch = 25.4 mm). The higher the number, the more thorough the filtration.

Indication of filter fineness:
- intake filter: 32 to 50 mesh
- section filter: 50 to 80 mesh
- nozzle filter: 80 to 100 mesh

As a reminder:
The filtration capacity of the last filtration levels must be adapted according to the risk of clogging the nozzles and the recommendations given by the suppliers.
It is possible to adjust the filtration fineness but also the volume of the filtration bowl if the filters become clogged.

Filtration that is too loose can lead to clogged nozzles!
Filtration that is too tight can lead to clogged filters!

There is an international colour code (which is generally respected) for identifying the filter's filtration capacity.

Tableau des correspondances des buses : filtration - mesh

MESH correspondence table

Some suppliers offer filters with a transparent bowl. This is particularly useful for checking the cleanliness of the filter without having to dismantle it.

Regulation

The regulator

This is an essential part of the sprayer, used to regulate the working pressure. It causes a greater or lesser proportion of the pump flow to return to the tank, to ensure a regular flow to the boom.

TANK RETURN FLOW = PUMP FLOW - BOOM FLOW

Sprayer regulators

Two control systems are used:
- Constant pressure regulation.
- Calibrated return flow regulation (also known as DPM: flow proportional to engine speed).

Constant pressure regulation
The regulator consists of a variable-load spring (by-pass) which, by modifying the pressure on the spring, which acts on the valve, makes it possible to obtain the desired pressure in the spray circuit. Part of the pump flow is diverted and returned to the tank. The quality of the regulator spring is of vital importance. It must be adapted to the working pressure.

Calibrated return flow control
Regulation is achieved here by diverting part of the pump flow back into the tank, either via an orifice whose cross-sectional area can be varied continuously, giving infinite possibilities for adjustment. Or via multi-calibration adjustment knobs.
The major advantage of this type of regulation is that the flow rate is virtually proportional to the forward speed at a given gear and within a range of 150 revs of PTO speed (450 to 600 rpm).

DPAE

These systems regulate the flow rate according to the forward speed in order to maintain the same volume/ha. these are consoles connected to a pressure sensor and/or flow meter and a speed sensor (GPS or sensor positioned on the wheel). The system regulates the pressure according to the volume/ha chosen in relation to the tractor's forward speed, once the working width has been set in the system. These consoles can also be used to control the opening/closing of sections, and to display and adjust the various spraying parameters (flow rate, pressure, volume/ha, etc.). Beware, some of the parameters displayed on the console are sometimes (often) calculated and not measured, giving the user the illusion of precision/reactivity that they cannot possibly achieve!

Distributors or valves

These are known as 'taps'.
A sprayer is generally fitted with a general cut-off valve and valves for each boom section.

For safety reasons (no spray liquid in the cab), manually-operated spool valves are not permitted in closed cabs. They are replaced by solenoid valves or motorised valves. Motorised valves are preferred to solenoid valves for reasons of reliability and maintenance, although solenoid valves have the advantage of closing almost instantaneously.

A motorised valve can take up to 1 second to close. Both closing devices must be adapted to the operating pressures in the circuit, otherwise they will deteriorate rapidly. Adjustable compensated return valves enable a stable pressure to be maintained when a boom section is closed.

Sprayer distributors

Nozzles holer

Booms

These support the nozzle holders or nozzles, the number of which varies according to the equipment. Their configuration varies considerably depending on the type of equipment.

Nozzle holders

These support the nozzle or the pellet, and are generally fitted with anti-drip devices that stop spraying when a valve is closed.
The opening pressure of the anti-drip devices is around 0.3 to 0.8 bar.

The pressure gauge

This is anything but an accessory. A pressure gauge, like a speedometer, is essential not only for setting up the sprayer, but also for monitoring it during use. The pressure gauge indicates the pressure at the point where it is installed, which can be very different at the nozzles depending on the pressure drops in the circuit. These will be correlated to various parameters such as the length of the hydraulic circuit, the diameter of the hoses, the flow rate of the liquid and the presence of obstacles to the flow (elbows, anti-drip devices, etc.).

For sprayers fitted with a digital pressure gauge, it is recommended to fit the sprayer with a needle pressure gauge, which will make it easier to check the information given and detect a problem.

Digital pressure gauge

Two types of pressure gauge are used:
- Bourdon tube devices, which use the deformation of a bent brass tube to move the needle and indicate the pressure.
- Electronic gauges use a strain gauge to measure the pressure and a digital display.

Needle pressure gauges

The manometer must be adapted to the pressures to be measured, but a safety margin is essential to avoid the devastating effects of false manoeuvres that damage the brass tube (exceeding the elasticity limit).

Expanded scale pressure gauges give good accuracy at low pressures, with a reading over 2/3 of the needle's travel; the last third allows high pressures to be reached with poor accuracy, but with protection for the mechanism (see illustration).

Needle pressure gauges are not allowed in the cab, but they can be placed outside the cab, behind the cab window and within sight of the driver.

Ventilation

Air flow is a very important parameter for successful spraying. For pneumatic sprayers only, air speed breaks up the stream of liquid (spray solution) into droplets and also plays a role in mixing the leaves and penetrating the product into the vegetation.

In air-blast sprayers, the main function of the air flow is to carry the droplets towards the vegetation, stirring it so that the spray mixture is evenly distributed throughout the canopy.
The air flow is generated by one or more fans.

Settings and uses

There is no standard setting for all types of sprayer. However, the calculation formulas remain the same.

Adjustment formula

Formula for calculating the volume of spray mixture applied per hectare:

Vol (L/ha) = 600 x Flow rate (L/min)
V (km/h) x L (m)

Volume: quantity of spray mixture to be applied in litres per hectare
Flow rate: total sprayer flow rate in litres per minute
V: working speed in km/hour
L: working width in metres (the distance between 2 passes of the tractor)

This formula may seem complex, but if you break down its parameters you can understand its origin better.

Here's how it works
Number of rows treated per pass: 4 complete rows planted at 2 metres apart
Width between rows: 2 m.
Total flow rate of sprayer: 12 L/min
Working speed: 5 km/h.

The volume of spray liquid per hectare planted will be :
Vol (L/ha) = (600 x 12) : (5 x 8) = 180 L/ha

Measuring flow through nozzles

This method is to be preferred when it can be carried out (ventilation shut-off) because, although it takes longer, it can be used to detect flow rate differences between the different nozzles. Simple to carry out, all you need is a test tube and a stopwatch, then measure the volume of liquid flowing from each nozzle (or diffuser) for one minute. It should be noted that, in some cases, a heterogeneous flow rate may result from a technical choice.

Measuring total flow

Given the design of pneumatic equipment, which uses not only (low) pressure for droplet formation but above all high air velocity at the diffuser, it is impossible to measure the liquid flow rate at the diffuser outlet if the fan is engaged (it cannot be disengaged on some models).
In this specific case, where the previous method is not applicable, the total flow measurement, which is faster but less accurate, can be used.

Procedure

Fill the spray tank to the brim.
Switch on the sprayer while the hose that fills it continues to flow, causing the liquid to overflow the tank. This operation primes the sprayer circuits perfectly.
Remove the hose and let the sprayer run for 5 minutes.
Fill the sprayer with a graduated container until it is completely full again.

The flow rate (expressed in litres per minute) will be equal to the volume of water required for readjustment divided by 5, as the flow rate was measured over 5 minutes (to limit errors).

Adjusting an air-assisted sprayer

When adjusting a machine fitted with mixed devices (e.g. hands and guns), you need to ask yourself the question "who does what", i.e. which part of the foliage will be treated by which element. This kind of thinking can lead to different choices of nozzles depending on the height of foliage treated by the nozzles, or the number of nozzles needed to treat the same height of foliage.

Example
The accuracy of the PTO speed sensor is checked using a tachometer at the PTO.
The combination of a gearbox ratio enabling the desired forward speed to be obtained at a PTO speed of 540 rpm is determined.

Generally speaking, spray quality tends to deteriorate with increasing forward speed. The choice of speed is therefore a compromise between work rate and application quality.
Generally between 5 and 7 km/h, the choice of forward speed should take into account the following factors, among others:

the technology used (tyres are often more sensitive to increases in forward speed)
the volume of air displaced (the greater the volume, the less impact an increase in forward speed will have)
the distance between the diffuser and the foliage
the state of the ground in the treated plots (uneven ground -> risk of boom swing)

Preferential spray circuit

What is a preferential circuit?
It's a hydraulic circuit that offers less resistance than another and on which the liquid flow will be directed. It leads to heterogeneous flow rates between the nozzles or the fingers of the same nozzle.

What causes a circuit to have preferential liquid flow?

different discharge heads.
different pressure drops (circuit length, pipe diameter, presence of bends or crushing of the pipe)

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Technical and economic selection criteria

Selection criteria

Adaptation to traction equipment

power available at the power take-off
oil flow available, if required
tractor balance for mounted sprayers

Vineyard configuration

width of plantation
height of foliage
thickness of foliage
topography

The zone of the plant to be reached

in the open
localised

Application period
adjustment options
purchase price and work rate

When it comes to spraying, we can really talk about targets that need to be reached. Appropriate means will have to be implemented to reach them while respecting the environment.
Clearly, the success of a treatment is the result of a synergy between knowledge of the disease or pest, control processes and a good application technique.

Particular points to watch out for

Vessel shape:
The presence of a diamond tip effectively limits tank bottoms.

Tank gauge:
A dry gauge (no contact with the spray liquid) will remain legible from a distance after several years. Its visibility from the cab is obviously a plus.

Rinsing tank:
Legally, it must have a capacity greater than or equal to 10% of the volume of the main tank.

Hand-wash tank :
Present and easily accessible.

Pressure gauge :
Suitable for the working pressure. Positioned so as to be easily seen by the tractor driver.

Drip guard :
Present.

Filters :
Number and ease of cleaning, respect for graduation.

Diffuser adjustment:
Being able to give them a vertical angle (inclination) and/or a horizontal angle (orientation) is often an important point for improving plant coverage.

Regulations and the environment

Machine design: Operator safety

When a sprayer is placed on the market, it must meet a number of technical requirements in line with Machinery Directive 2006/42/EC, which came into force in January 2010.

This directive lays down design rules to meet operator safety requirements.
This directive lays down the design and construction rules to meet the essential health and safety requirements for the operator. The Machinery Directive (2006/42/EC) will be replaced by Machinery Regulation 2023 (1230), which was published on 29 June 2023 but will not come into force until 20 January 2027.

Machine design: Environment

Sprayers must also comply with Directive 2009/127/EC (Amendment to the Machinery Directive which imposes environmental requirements on new sprayers in addition to the safety requirements as defined in Machinery Directive 2006/42/EC)

The main requirements are

Accuracy of application and prevention of drift
Ease of maintenance and cleaning
Easy connection of measuring devices such as pressure sensors and flow meters (particularly for technical inspection)

Note: the harmonised standards relating to these Directives/Regulations are currently being revised. These include EN/ISO 4254-6 on sprayer safety and the ENISO 16 119 series on the environment.)

Technical inspection of sprayers

Checks on agricultural sprayers have been compulsory in France since 1 January 2009. The inspection is periodic and must be repeated every 3 years.

During the technical inspection of the sprayer, a number of points are checked:

The general condition of the equipment
The presence of safety devices
The condition of the plugs and the operation of the filling and emptying systems, etc
Condition of pipes, hoses, circuits, etc
Proper operation of measuring instruments: pressure gauges, etc
Condition of filters
Flow rates of nozzles, pellets, etc

The list is not exhaustive.

ZNT in the vicinity of watercourses

"Untreated zone": zone characterised by its width at the edge of a water point, corresponding for watercourses, outside flood periods, to the limit of their minor bed, defined for a use of a product used under the conditions provided for by its marketing authorisation decision or by this decree and which may not receive any direct application, by spraying or dusting, of this product.

By default, a ZNT is 5m; it may be extended to 20 or 50 m depending on the plant protection product's marketing authorisation. Source: DRAAF Nouvelle Aquitaine.

It is possible to benefit from reductions in the ZNT under certain conditions:
1. Presence of a permanent vegetation cover at least 5 metres wide at the edge of water points:

shrubby for tall crops (arboriculture, viticulture, hops and tall ornamental crops), the height of the hedge must be at least equivalent to that of the crop
herbaceous or shrubby for other crops

2. Implementation of measures to reduce the risk to aquatic environments
These means must appear on a list published in the Official Bulletin of the Ministry of Agriculture. Each method selected must make it possible to reduce the risk to aquatic environments by at least a factor of three compared with the normal conditions under which the products are applied.

The list of equipment can be downloaded from
info.agriculture.gouv.fr/gedei/site/bo-agri/instruction-2023-282

DSR and DSPPR (Riparian distances)

The Order of 27 December 2019 introduced the concept of DSR (Distance Sécurité Riverains). This order was amended by the order of 25 January 2022.
The result is a set of regulations governing the use of plant protection products in the vicinity of local residents and bystanders.
Safety distances for phytopharmaceutical treatments near dwellings | Ministry of Agriculture and Food Sovereignty

These distances can be reduced by using certain equipment on an official list.

New technologies & spraying

Although not yet fully developed in the field of spraying, new technologies are slowly appearing to facilitate treatment and/or traceability work. These are usually sensors/actuators linked to GPS. They can be used to modulate the dose on an intra-parcel scale and/or automatically cut off sections at the end of the row (which is particularly useful in the case of narrow vines where the rows are not all the same length).
PWM nozzles may provide new technical solutions for taking another step towards precision spraying, but their high cost is likely to penalise any commercial development in viticulture.
Finally, traceability tools (keyfield, etc.) have also appeared in an attempt to automate and simplify the recording of agricultural work and spraying in particular.

Other tools have also been developed to provide easy access to past and/or forecast weather data (weather stations, spatial data, etc.). They are often combined with models or Decision Support Tools
(https://decitrait.vignevin-epicure.com/login) to help the winegrower/advisor position treatments more effectively and choose the right product dose. Some allow simplified traceability of treatment operations.

Quality of spraying

Projet Eval'pulvé - Qualité de pulvérisation

Eval'Pulvé project

The aim of the project (funded by the Nouvelle Aquitaine Region) is to develop a tool for assessing the quality of spraying. It is being carried out by the Gironde Chamber of Agriculture, CTIFL andIFV as part of the Eval'Pulvé project .

How it works

the tool consists of a stand equipped with UV lighting. The smartphone is attached to this support to take the image.

The vines are sprayed with a fluorescent tracer supplied by our partner Jean-Louis Talon, which fluoresces even when dry.
Images are acquired in the field using a smartphone and its acquisition medium, following a sampling plan.

Image analysis and interpretation

Conventional image processing for the following measurements:

The number of impacts per cm²
An estimate of the median drop size (vmd)
An estimate of the coverage rate on the leaf and the volume/ha
The data is processed retrospectively by computer.

The final objective is to develop an application that will enable users to self-assess the quality of their application and provide recommendations on settings.

Recuperator panels

In addition to the spraying technology used, some equipment is equipped with recuperator panels.

Historically used for winter treatments with sodium arsenite, sprayers with recovery panels had, since the ban on this product in November 2001, returned to the obscurity of sheds. However, new environmental concerns and the ECOPHYTO plan have given them a second lease of life. While the equipment used for winter treatments with sodium arsenite was simple in design (generally a single panel spray), the use to which they are now put (treatments throughout the season) has seen them evolve considerably, with the addition of a blower in particular. Most of these are fitted with a carrier jet (a droplet production method more suited to recovery), although some pneumatic equipment is fitted with panels. There are various systems for recovering the spray liquid from the bottom of the panels. These generally involve a dedicated piston pump, but peristaltic pumps or hydro-injectors are not uncommon. While they can save around 30% of spray mixture over an entire campaign, they have a number of drawbacks (cost, space requirements, work rate, etc.) which have considerably limited their use. The Cognac vineyards (wide vines, moderate slopes) have by far the highest proportion of sprayers fitted with panels.

Most manufacturers now include at least one piece of equipment fitted with recovery panels in their range.