Sorting grab buying guide: choosing a sorting grab for 2–11 t excavators

A sorting grab turns an excavator into a handling machine: it picks, sorts, loads and places material with control, instead of digging it. For a contractor, recycler or landscaper on a 2–11 t carrier, the right grab cuts manual sorting and double handling. The wrong one is either too heavy for the arm, too small for the material, or cannot be run properly on the machine's hydraulics.

This guide explains how Thunderline matches a sorting grab to an excavator: what the tool is used for, how grab size, weight and opening relate to the carrier class, what the rotation and hydraulic circuits need, how mounting is checked, and what wears. Thunderline is an independent dealer of excavator attachments from selected European manufacturers. Where we quote figures, they come from the datasheets of the two rotating sorting grabs in our range, the Promove SG 3.4 and the Promove SG 6.11.

What a sorting grab is used for

A sorting grab has two shells that open and close hydraulically, usually on a rotator so the grab can be turned to line up with the material. Typical work:

• Demolition sorting and light demolition – strip-out of sheds, walls and small structures, then separating concrete, timber, metal and mixed waste on site.
• Recycling – sorting mixed construction and demolition waste, feeding screens and crushers, picking out timber, steel and plastics.
• Forestry and land clearing – handling brush, branches, stumps and logs, clearing plots and loading the material for removal.
• Loading and placing – loading trucks and containers, handling stone, kerbs, pipes and scrap, and placing rock with control.

A sorting grab is a handling tool. For the SG 3.4 and SG 6.11, Promove names sorting, loading and light demolition work as the intended uses. Heavy demolition, crushing and breaking are jobs for dedicated demolition tools.

Match the grab to the excavator class

The carrier class stated by the maker is the first filter. A grab hangs at the end of the arm, often with a load in it, so its own weight, its size and its opening have to suit the machine. Too heavy and the excavator loses lifting capacity and stability at reach. Too small and you lose cycle time on every pick.

The two models in our range are published for these carrier classes:

Figures from the Promove datasheets. Promove states that technical data are non-binding and may change without notice; the final specification is confirmed with your order.

How that translates to common excavator classes:

• 2–4 t – the SG 3.4 is published for 3–5 t carriers, so it covers the upper part of this band. For machines under 3 t, send us your machine model and we tell you plainly whether we can quote a grab for it.
• 4–7 t – up to 5 t, the SG 3.4; from 6 t, the SG 6.11. Between 5 and 6 t the machine sits between the two published classes, so we check lifting capacity and hydraulics against your machine data before we recommend either model.
• 7–11 t – the SG 6.11 is published for 6–11 t carriers and is the model for this band.

Always use the excavator’s actual operating weight as configured, not only a class label. At the light end of a class, add the grab weight, the quick coupler and the heaviest load you plan to lift, and compare that with the machine’s lifting capacity at the reach you work at.

Rotation and hydraulic requirements

A rotating sorting grab needs two auxiliary hydraulic circuits: one to open and close the shells, one to turn the rotator. With a single circuit the grab cannot both open/close and rotate. Both SG models have separate circuits for these functions:

The rotation circuit is the one to watch. Its flow and pressure window is small, and many excavators deliver more oil and pressure on their auxiliary lines than a rotator is built for. Where the machine delivers more, flow – and on the rotation circuit also pressure – has to be limited to the datasheet values. Too much flow makes the grab turn too fast and overloads the rotation drive.

Before you ask for a quote, note what your machine has: how many auxiliary circuits, whether they are double-acting, the flow and pressure settings available for each, and the hose coupling sizes at the dipper. If the machine has had its hydraulics retrofitted, the factory spec sheet is only a starting point. Our guide on oil flow and pressure explains how these values are read and checked; the same principles apply to a grab’s circuits.

Both SG models have a safety valve to prevent the load from dropping, per the Promove catalogue.

Quick coupler and mounting

Most fleets run a quick coupler, and the coupler or pin-on dipper on your machine decides how the grab is connected. Both SG models come with a bolt-on top mount. How that mount connects to your coupler, or to a pin-on dipper, depends on the coupler type and the pin dimensions of your machine, so it is confirmed against your machine data before we quote.

Send us the coupler type, or the pin measurements if the grab goes directly on the dipper. If you are not sure which coupler is on the machine, “not sure” is a valid answer – a photo and the machine model usually settle it. Our coupler and pin-on measuring guide shows what to measure.

Wear parts and maintenance

A sorting grab works in abrasive material all day, so wear is normal. On the SG series, Promove lists Hardox jaws, bolted wear-resistant reversible blades, and a single through pin with double connecting rod. In practice:

• Blades – check the cutting edges regularly. Reversible bolted blades can be turned before they are replaced; check the bolts while you do it.
• Pins and bushings – look for play in the main pin and the connecting rods. Play grows quickly once it starts and costs precision when sorting.
• Greasing – grease the points named in the maker’s manual at the intervals it gives.
• Hoses and couplings – check hoses for chafing on the arm and rotator, keep couplings clean and cap them when the grab is off the machine.
• Rotation – if the grab turns too fast or unevenly, check the rotation circuit settings against the datasheet before anything else.

Both models carry a 12-month warranty from delivery, with claims handled through Thunderline.

Checklist before you request a quote

1. Excavator make, model and operating weight as configured
2. Main work: sorting, recycling, light demolition, land clearing or loading
3. Quick coupler type, or pin dimensions for a pin-on dipper
4. Number of auxiliary circuits, and flow and pressure for each
5. Hose coupling sizes at the dipper
6. The heaviest loads you plan to handle and the reach you work at
7. Delivery country and your EU VAT number

FAQ: sorting grabs

Can a sorting grab be used for demolition?

For light demolition, yes. Promove names sorting, loading and light demolition work for the SG 3.4 and SG 6.11. Heavy demolition, crushing and breaking need dedicated demolition tools.

Why does a rotating sorting grab need two hydraulic circuits?

One circuit opens and closes the shells, the second turns the rotator. On the SG 6.11 that is 30–40 l/min at max. 300 bar for open/close and 10–15 l/min at max. 150 bar for rotation; on the SG 3.4, 30–40 l/min at max. 300 bar and 5–10 l/min at max. 100 bar.

Which grab suits a 5–6 t excavator?

That weight sits between the published classes of the SG 3.4 (3–5 t) and the SG 6.11 (6–11 t). Send us the machine model, operating weight and auxiliary circuit data, and we check lifting capacity and hydraulics before recommending either one.

My excavator delivers more oil flow than the rotation circuit needs. Is that a problem?

Only if it is not limited. Flow, and on the rotation circuit also pressure, has to be set to the datasheet values. Too much flow makes the grab turn too fast and overloads the rotation drive.

What wears on a sorting grab?

Mainly the blades, pins and bushings, and hoses. On the SG series the blades are bolted and reversible, so they can be turned before they are replaced.

What warranty applies?

A 12-month warranty from delivery, with claims handled through Thunderline.

Next step – ask for your quote

Competitive prices – ask for your quote. Send us your machine data from the checklist above and we reply with a written quote. Same-day reply, usually within 2 hours.

Request a quote → · Promove SG 3.4 (3–5 t) · Promove SG 6.11 (6–11 t) · Sorting grabs for 6–11 t excavators · or email hello@thunderline.eu

More buyer guides are on our Guides page.