B In The Know

The Cutting Edge 2024

Do you know all the hydraulic demands that an air seeding system requires from your tractor? Here are some details to consider.

Hydraulic Metering Drives

The hydraulic metering drive used across the 7000, 8000, and 9000 I Series Air Carts is a ‘series’ system, which means each meter is connected together such that the output from one meter is the supply for the next in the chain. Therefore it doesn’t matter if you have 1 meter or 5, the system always requires 5.5 GPM to operate. If the full flow isn’t required by a meter because it is turning slower, it simply bypasses some of the oil, and then all of the flow continues on to the next meter. This series metering circuit requires 5.5 GMP even when all meters are turned off electronically.

Fan Selection

Bourgault offers four different fans on the 9000 A/C:

Standard (optional only on the TriMax™ seed run),
High-Speed,
High-Capacity, and
High-Pressure.

Higher application rates require a larger volume of air at an increased pressure to carry the product, which coupled together means more hydraulic power is required to meet the need. When high rates aren’t required, it is simply inefficient to use more hydraulic flow than is required. If your maximum urea rate is 275 lb/ac, then a high-speed fan is all that is required; if you want to push 400+ lb/ac then a high-pressure will be needed. A high-speed fan requires 20 GPM of hydraulic oil to turn at the maximum 6000 RPM, a high-capacity 26 GPM, and a highpressure fan requires 32 GPM.

Drill Hydraulic Requirement

The number of openers and MRB’s on your drill directly impacts the hydraulic flow required by the depth circuit. So although smaller width drills and units without MRB’s may require less, a good rule of thumb is to plan for 30 GPM for the drill alone. Since the drill requires this flow at a low pressure, in a sense it “steals” it from the fans! However, this required flow is only needed on the headlands when the openers are lifting and lowering. Having adequate flow available will ensure that the fans can maintain required RPM’s and openers can raise / lower quick enough on the headlands.

Total System Requirement

The hydraulic demand for a typical seeding system is as follows:

Fan 1 = 26 GPM (High Capacity Fan)
Fan 2 = 26 GPM (High Capacity Fan)
Metering Circuit = 5.5 GPM
Drill = 30 GPM
TOTAL = 87.5 GPM

Ensuring your tractor has this minimum amount of continuous flow available will ensure good operating performance.

Tractor RPM

Most of today’s modern tractors require a minimum engine RPM to be able to meet the pressure and flow demands of a seeding system. Although you may be able to pull the drill and operate successfully when seeding a typical fullwidth pass, when the seeding system requires a spike of hydraulic demand (closing or open ASC valves for example) the tractor may not be able to keep up. Ensure you know the required engine RPM to reach peak hydraulic capacity because you may need to throttle up for success!

Maximum Demands

The maximum hydraulic demand occurs when your air seeding system is reentering the ground following a turn at the headlands. The fans will ramp up to operating speed as product reenters the distribution system. The openers need a high flow rate of oil as they are lowered and fully engage into the ground. Plus, the Auto Sectional Control gate valves all actuate from closed to open! The maximum electrical demand occurs when you are filling your air seeding system at night when you are parked over seeded ground. The large solenoid valves require power to divert oil to the conveyor and to hold the openers in the raised position. Additionally, all of the work lights will be on and the solenoids for all of the Auto Sectional Control gate valves will be powered in the closed state.