A rotary screening bucket is driven by a hydraulic motor, so unlike a riddle bucket it needs the right hydraulic supply from your excavator. Get it wrong and the drum turns slowly, stalls under load or, worst case, damages its motor. Most modern excavators can run one, and the checks are straightforward once you know what to look for.
What a Screening Bucket Needs from Your Machine
- An auxiliary hydraulic circuit with a feed and a return line, like the pipework many machines already have for a breaker.
- Enough oil flow, measured in litres per minute, to turn the drum at the right speed.
- The right working pressure, so the motor has enough power without being overloaded.
- A case drain line running back to the hydraulic tank.
Oil Flow and Pressure by Size
| Bucket | Oil flow | Working pressure | Empty weight |
|---|---|---|---|
| 4–6 tonne screening bucket | 20 l/min | 80–120 bar | 450kg |
| 6–10 tonne screening bucket | 20–30 l/min | 80–120 bar | 620kg |
| 10–16 tonne screening bucket | 30–50 l/min | 210 bar | 1,020kg |
| 17–22 tonne screening bucket | 30–50 l/min | 210 bar | 1,620kg |
Your excavator's auxiliary flow is listed in the operator's manual or spec sheet, usually under auxiliary hydraulics or the hammer circuit. On many machines the flow can be adjusted through the display or by a dealer. Too little flow and the drum turns slowly and screens less. Too much and the motor runs too fast and wears quicker.
Why the Case Drain Matters
Every hydraulic motor leaks a small amount of oil internally. That oil collects inside the motor casing and needs a way out. A case drain line carries it straight back to the tank at low pressure. Without one, pressure builds up inside the casing and can blow the motor's shaft seal, which means downtime and an expensive repair.
Our excavator screening buckets have three front-facing ports: flow, return and drain. Many excavators already have a case drain fitted for other hydraulic attachments. If yours doesn't, a dealer or hydraulic engineer can usually add one, so it's worth pricing that before you buy.
Couplings and Hoses
Check which quick-release couplings your machine uses and make sure the hoses reach through the full range of dipper and bucket movement without stretching or rubbing. Connect the drain line first and disconnect it last, so the motor casing always has somewhere for oil to go.
Don't Forget Weight and Lift Capacity
A screening bucket is much heavier than a standard bucket of the same width, and the weights in the table above are before you add any material. Check your excavator's lift chart at the reach you'll be working at with a full bucket, and make sure your quick hitch is rated for the combined weight.
Getting the Best from Your Screening Bucket
- Choose the right screen. Interchangeable Hardox screens from 20mm to 80mm let you change the grade. Smaller holes give a finer product but screen more slowly.
- Don't overload the drum. A drum filled to the brim tumbles less and screens slower.
- Let the drum do the work. There's no need to shake the machine, which is one of the big advantages over a riddle bucket.
- Warm the oil up first on cold mornings so the motor isn't working against thick oil.
- Check screens and bearings regularly and replace worn screens before the holes wear oversize.
Can't Meet the Requirements?
If your excavator can't supply the flow or doesn't have a case drain, a riddle bucket needs no hydraulics at all and still pulls stones and rubble out of soil. Our comparison of riddle buckets and screening buckets will help you decide, or browse the full excavator sorting buckets range.
Frequently Asked Questions
Can I run a screening bucket off my breaker circuit?
Often, yes, provided the circuit delivers the flow and pressure in the table above and you have a case drain. Check with your dealer, or send us your machine details, before connecting.
What happens if I don't connect the case drain?
Pressure builds inside the motor casing and can push out the shaft seal. The motor then leaks oil and stops turning properly. Always connect the drain.
What screen size should I use for topsoil?
A 20mm to 30mm screen gives a fine, even topsoil for turfing and planting. Larger screens, from 40mm to 80mm, suit hardcore, stone and demolition material.
Do I need a screening bucket rated for my exact machine?
Yes. Each size is matched to a weight class for its flow, pressure and weight. Running a bucket built for a bigger machine can overload your hydraulics and your lift capacity.
Send us your excavator make, model and year through our quote form and we'll confirm whether it can run a screening bucket and which size to choose.
