Six numbers that decide fitment

Two models can share a mounting flange and still not be interchangeable. When a buyer sends us two candidate units, these are the figures we compare, in this order, before quoting either one:

1. Displacement (mL/r) — sets the oil flow delivered per revolution. Matching it is what keeps cycle times and travel speed where the machine was designed for.
2. Rated and peak pressure — the relief setting of the machine must sit inside the unit's rated band. A unit that is pressure-capable but not speed-capable still fails in the field.
3. Maximum speed — self-priming and continuous limits differ between the DT, DTP and DTH variants of the same series, so the order code has to be read with it.
4. Input torque — the engine has to be able to turn the large unit at full displacement; a larger displacement is not automatically a better answer.
5. Shaft end and mounting — spline count, flange bolt circle and pilot diameter decide whether the unit bolts on at all. This is the part of the comparison a photo of the old unit settles fastest.
6. Control variant — the regulator, the servo piston and the pilot arrangement decide how the machine responds. Two units with the same displacement and different control behave differently in the operator's hands.

Where a figure is not in the catalogue, we measure it from the unit in the workshop and record it, rather than guessing from a neighbouring series. Numbers that cannot be verified are marked as such on the model pages.

The comparisons