By Paul Badowski, CFPS, Cross Company – Mobile Hydraulics & Control Systems Group
Industrial hydraulic valves are available in mainly four sizes, D03, D05, D08, and D10. Specialty sizes are less common but available. Each size designates a particular flow requirement, D03 – @10 GPM or less, D05 – @20 GPM or less, D08- @80 GPM or less, D10 – @200 GPM or less; there are many exceptions but these are general ranges.
In an industrial parallel manifold, there is a pressure passageway which sends oil flow through the P-Port gallery. This passageway supplies oil flow to each individual valve station. The manifold is machined as one block and adding another station requires a new manifold. There is a T-Port which is used for return oil, allowing a path for the oil to get back to the tank.
An industrial manifold can also be machined as a serial manifold. This would plumb the oil to the first valve station; flow to the next station would be routed through the first valve, rather than into a common passageway.
The valves are mounted at each station and the valve could have multiple spool types, specifying where the oil goes in each condition of the valve. These valves are normally solenoid operated as mechanical and hydraulically piloted valves are infrequently used. Flow controls, check valves, and pressure reliefs can be stacked as a module underneath each valve as needed.
Consider a hypothetical, similar to the above image. A hydraulic pump supplies 10 GPM flow to a circuit which has six functions.
My first choice is a D03 sized – six station parallel “industrial” valve manifold. The flow from the pump goes in the P-Port and flows back to tank goes through the T-Port. D03 size hydraulic valves are mounted to the manifold to control each of the functions.
Another choice would be a “mobile” hydraulic valve. These valves are similar to the industrial valve but have some distinctively different features and options. Where the industrial valve is based on a valve mounted on a manifold, the mobile valve will have the valve and manifold combined into one body.
These valves can be mechanical, solenoid, or hydraulically piloted. In many cases, you may have a solenoid operated valve that also has a mechanical lever. Valve stations can be added as needed with bolts sandwiching the stations together. This valve package can be parallel or serial, depending on the valve model and ordering codes.
Mobile valves have spools which are designed to allow controlled flow as you move the spool, sometimes referred to as feathering. Industrial valves are referred to as “Bang-Bang” valves denoting the full open and full closed states of the valve.
Special spools and proportional operation eliminate the “Bang-Bang” effect in both industrial and mobile valves.
There are custom features included with mobile valves such as load sensing, pre and post-compensation of the workflow, flow-specific passages, load holding checks, or work port pressure reliefs can be built in each valve station.
Mobile valves tend to be flow-specific with a series of valves for the particular flow required in a circuit: 6 GPM, 12 GPM, 22 GPM, 75 GPM, etc…
In my next hypothetical, we are getting our flow from the auxiliary ports on a tractor.
The tractor has cab controls connected to one or several sets of hydraulic remotes and each set has two connections at the back of the tractor. We don’t know whether the remotes are pressure or tank lines as this is not dedicated and is controlled from the cab. The remotes are used to control lift cylinders, hydraulic motors, or other devices which are included with tractor implements. The implement is hooked to the tractor with hoses and quick disconnects and then controlled from the tractor.
The user needs to control several operations with one set of tractor remotes. The functions never operate at the same time. We need to position the implement in a high position for road travel and then lower it into place to do work – but the user has a hydraulic motor that only spins when in the work mode.
All of the available hydraulic remotes on the tractor are being used. In this application, I recommend a hydraulic diverter valve. This valve will take the flow from the hydraulic remotes and “divert” it to my choice of flow paths.
You can manifold several diverter valves together if you have more conditions. The user can switch from Position A to Position B electrically, manually, or with a hydraulic pilot signal (least likely).
The best part of the diverter valves is that you still use the cab controls to control the work function. By switching the tractor controls, the C and D-Port will switch from C-Pressure and D-Tank to C-Tank and D-Pressure and reverse the motion.
When switching the Diverter Valve to Position B, the C and D-Ports are now blocked. The hydraulic remote lines are now hooked to the E and F-Port and the tractor controls another motion.
Here’s another example: you have a track driven excavator which moves around a collection yard for large felled trees. After using the tracks to move the excavator into the required work position, the vehicle will stay in the same position most of the day and load the logs onto trucks.
Once in position, manually controlled diverter valves are switched into Position B. Position A powers the tracks. Position B powers an auxiliary device.
Both of these motions are controlled by the excavator operator in the cab. We are able to utilize the pump flow capability of the excavator to do auxiliary work without supplying an additional hydraulic power unit.
To help decide what type of valve, size, shape, and configuration, call Cross Company. We can help find the correct product and engineer a control solution which is optimized for your machine.