OMEF CPT180 excavator compactor

A 2 to 5 tonne excavator can dig a service trench, lay bedding, and then stand there while somebody else compacts the backfill. The OMEF CPT180 closes that gap: 170 kg, 12 to 20 L/min at 100 to 120 bar, and a plate on the end of the dipper that reaches the bottom of a trench nobody should be standing in. It is the smallest of the three CPT models, and the one most often bought by a business that owns exactly one excavator.

The stated force figure, and what it is not

Every plate in this series is published with a stated force to ground. On the CPT180 it is 18 t, on the CPT425 50 t and on the CPT910 110 t. Because this is the page for the model buyers meet first, the caveat belongs here in full.

That number is a supplier comparison figure produced under the manufacturer’s own test method. It expresses, in a single value, how hard the plate strikes under the conditions of that test. It ranks the three models against each other reliably, and that is what it is for.

It is not a density guarantee, and it cannot be. Field density is a property of the soil in the trench, not of the machine on top of it. What you actually achieve depends on the material, its grading and plasticity, its moisture content relative to optimum, the thickness of each lift, the number of passes, how evenly the plate contacts the surface, and what the plate is sitting over. Two sites compacted by the same machine on the same day to the same pass count can test differently, which is precisely why specifications are written in terms of density achieved rather than plant used.

Three practical habits follow. Set the lift thickness from the specification and the material, not from the plate rating, and reduce it when the material is wet, plastic or poorly graded. Budget field testing on any job with a specified density, because the test result is what gets paid on and no attachment rating substitutes for it. And treat moisture as the variable that actually decides the day: material well outside its optimum moisture range will not reach density under any plate, and adding passes mostly wastes time.

There is one further trap with a figure quoted in tonnes. It describes a dynamic impact under a test, not a static load that the ground, the trench wall or a buried service experiences at rest. Vibratory compaction directly over shallow services is governed by the asset owner’s cover and lift requirements, and those rules apply whichever plate is fitted.

Working at the bottom of a trench on a small machine

What the CPT180 offers a mini excavator owner is reach into places a person or a walk-behind plate should not go. A 1.5 m deep service trench in unstable ground is the standard example: the excavator sits on the surface, the plate goes down, the trench stays unoccupied, and the backfill is compacted in lifts without anyone entering an unsupported excavation.

At 170 kg the plate is roughly what the machine would carry in a loaded bucket, so it is rarely a lift chart problem at normal working radius. The exception is worth checking rather than assuming. Reaching across a trench to compact the far shoulder, or working at full stick extension into a deep trench with the boom low, puts the mass a long way out, and on a 2 tonne machine that is where the chart tightens. Check it at the geometry the job actually uses, following the lift chart guide, and remember to add the hitch.

The other thing that reach costs is cycle time. Compaction itself is quick; stepping the plate along a trench is not. On a narrow trench the operator is placing the plate, running it, lifting, moving perhaps 300 mm, and placing again, and the rate for the day is set by how smoothly that sequence runs rather than by the plate’s output. Position the machine so the whole run is inside a comfortable slew arc and the cycle tightens noticeably.

Circuit, vibration and the hitch

Twelve to 20 L/min is a low requirement that most compact carriers already deliver on the hammer circuit, and 100 to 120 bar leaves headroom on any modern mini excavator. More is not better here: excess pressure or flow into a vibratory motor shortens its life rather than improving compaction, so the relief and flow settings should be set to the published windows rather than left wherever the breaker wanted them.

Ask Machinery Specialist, for the current build, whether the plate runs on a single-acting line with a free return or needs a double-acting circuit, whether a case drain is fitted, and what return back pressure the motor tolerates. Those three answers determine how the carrier is plumbed, and the hydraulic matching guide covers the general method. The 1 to 5 tonne class page covers what compact carriers can run continuously.

Vibration is the part buyers underestimate on a small machine. A plate compactor feeds shock straight up the dipper into the pins, the hitch and the boom, hour after hour, which is a duty an excavator was not designed around. Isolation buffers in the attachment absorb most of it, and their condition is what stands between the vibration and the machine. Specify a hitch rated for vibratory duty, include its weight in the figures, and make buffer inspection part of the routine rather than something done after a crack appears.

The jobs it pays for

Service trench backfill on subdivisions, pathway and kerb bedding, landscaping fill, small footings, and reinstatement around pits and structures. In every case the commercial argument is the same and it is about people rather than plant: the machine that dug the trench closes it, the labourer with the walk-behind plate is not needed, the manual handling disappears, and nobody enters the excavation to compact the lower lifts. On a small residential or council job where the crew is two people, that can be the difference between a job that needs a third and one that does not. See subdivision and civil clearing and council parks and urban vegetation.

Where the plate does not belong is open ground. A wide pad or a length of road base is roller work, and the reasons are set out on the CPT425 page. Ground still full of roots and stumps after clearing is not ready for any compactor, since compacting over woody material builds in voids that settle later; deal with it using a stump cutter or stump grinder first. And where the fill is deep and structural, a larger plate on a larger carrier is the right answer. The tillage and ground preparation guide explains where excavator compaction sits against rollers and against true forestry site preparation, and the TRV auger drive covers the other end of the ground-preparation range.

At quotation, settle the bracket and hitch including whether a quick hitch is used and what it weighs, the circuit type and any drain, hose lengths for the dipper, the flow and relief settings to be programmed, plate width options, and whether rotation or tilt is offered. Get the delivered weight in the ordered configuration and the current hydraulic requirement in writing. The wear items are the base plate, the isolation buffers, the motor seals and the bracket pins, with the frame around the vibration mounts as the place to look for cracking. Price a buffer set and a seal kit with Machinery Specialist, confirm Australian stock, and use the wear parts guide.

Confirm before ordering

• Lift thickness and pass count taken from the geotechnical specification and the material, not from the 18 t figure
• Field testing budgeted on any job with a specified density
• Asset owner's cover and lift rules checked before compacting over shallow services
• Hammer circuit set to 12 to 20 L/min and relief inside 100 to 120 bar, not left at breaker settings
• Circuit type, case drain and return back-pressure limit confirmed in writing for the current build
• Chart checked at the worst geometry on the job, reaching across or into the deepest trench, with the hitch included
• Hitch rated for vibratory duty and buffer inspection scheduled
• Buffer set and motor seal kit priced with Australian stock

Frequently asked questions