There are three different types of boom valves that are commonly fitted to sprayers: solenoids, ball valves and plunger valves.

Solenoid boom valves with diaphragms

Solenoid boom valves with diaphragms are a common boom valve used on sprayers with narrow booms and are also used to control the nozzle output on the WeedSeeker® (target-selectable sprayer).

Examples include TeeJet® DirectoValve®, Goyen solenoid valves and Texas Industrial solenoid valves.

Most solenoid boom valves generally operate based on a ‘two-wire system’ comprising a ‘signal wire’ and a ‘ground wire’.

Solenoid valves allow the liquid flow to turn on and off very rapidly.

Some possible limitations of solenoid valves are:

• they must have power to remain open, which can generate heat in the solenoid;

• they may continue to draw current from the battery if the boom switches are left on; and

• the solenoid’s diaphragm may be affected by the formulation type of the products used, which can limit the flow rate.

Ball boom valves

Ball boom valves are commonly supplied with either nylon or stainless-steel balls. Examples include TeeJet® DirectoValve and Banjo electric valves.

Most ball boom valves only need power to open or close the valve, so there is no need for constant power when the valve is off (they will not flatten the battery if the controller panel is left on).

Tip

• It is important to match the material that the ball is made of to the product being used, e.g. stainless-steel balls for liquid fertilisers.

Plunger boom valves

Plunger boom valves are very common on many spraying systems due to their speed of operation and the accuracy of regulation that can be achieved with some models.

Examples of plunger boom valves include: Hardi boom section valves, GEOline® electric section valves and the ARAG® Electrovalve.

Two-way boom valves

Two-way boom valves are the most common boom valve fitted onto sprayers. 

With a two-way boom valve, the flow simply comes into the boom valve and can only go out to the boom (or boom section). When using two-way boom valves with a manual control system, the pressure in the boom may spike when a boom switch or section is turned off, causing the automatic rate controller to spike briefly. However, the pressure will return to normal once the regulating valve can adjust the flow to match the new overall width.

Three-way boom valves

Unlike two-way valves, where flow coming into the boom valve can only go out to the boom (or section), with a three-way valve installed when a boom switch is turned off, the flow from the valve goes to a return line back to the top of the tank.

When using three-way boom valves with a manual system, the pressure will remain the same when a boom switch is turned off, provided the correct adjustments have been made to the manual return valve.

When using an automatic spray rate controller with a three-way boom valve, the pressure will remain the same (if adjusted correctly) when a boom switch (or section) is turned off. As a result, the regulating valve does not have to make any adjustments to the flow.

Installing three-way boom valves is a good option for most sprayers, provided the controller is able to operate them. However, they may not be directly compatible with chemical injection systems.

Three-way boom valves are very good when using small boom sections, or for systems that have individual nozzle shut-off, because the flow meter does not have to work at the minimum flow it is capable of reading.

When using three-way boom valves, the flow meter reads the total flow, but the controller ‘knows’ to work out the litres per hectare based on the boom sections or nozzles that are actually turned on.

By setting up the spray system with three-way boom valves, the workload on the regulating valve is reduced, as it only has to respond when there is a speed adjustment.

Flow-back boom valves

Flow-back boom valves are located on the boom itself. When a boom section is turned off by closing the boom valve (e.g. a two-way boom valve), the flow-back boom valves open to release the pressure from the boom line, returning the liquid flow back to the top of the tank. This type of boom valve allows the non-drip check valves on the nozzles to shut off the spray very quickly.

Tips

• Always have a can of contact cleaner on hand, for servicing connections and to troubleshoot electrical faults.

• Most boom valve manufacturers use DIN connectors on their boom valves, which makes them easy to install, service and to maintain the electrical connections.