External Vibrators

External concrete vibrator — how it works and where it is used

An external vibrator (trailer vibrator, form vibrator) is a unit fixed to the outer wall of formwork, shuttering or a steel precast mould. Unlike a poker (internal) vibrator, which is immersed directly in the mix, an external vibrator transmits vibration through the wall of the mould — an eccentric weight spinning inside the housing sets the whole structure vibrating at high frequency, and those vibrations travel through the metal or formwork into the concrete filling the mould. This lets the mix compact evenly even in elements with complex shapes and dense reinforcement, where fitting a poker between the bars would be impossible.

An external vibrator's drive can be pneumatic (compressed air from a compressor) or electric (a motor powered from a 230 V single-phase or 400 V three-phase mains supply). Both types are bolted permanently to the mould structure using screw brackets, so the choice is made once — at the stage of equipping the mould, not before every pour. External vibrators are standard equipment in precast concrete plants, but they also work well on large-format formwork on site, where a whole wall or column needs vibrating without access for a poker from above.

Types of external vibrators — pneumatic or electric

The choice of drive mainly depends on the infrastructure of the plant or jobsite. Where a compressed-air network is already running — most often in precast plants — a pneumatic vibrator makes sense: light, with high frequency regulated by air pressure. Where a plain power socket is all that is available, an electric vibrator wired directly into the mains is the simpler installation.

Pneumatic vibrators, such as the Wacker Neuson PEV series, run at a working pressure of around 5–6 bar and cope well with continuous duty, because the air stream cools the mechanism on every cycle. An electric vibrator, such as the Wacker Neuson AR 26/3/230 W, only needs a mains connection, but for long continuous runs it is worth checking the datasheet for whether the motor carries a continuous-duty class S1 rating — otherwise it can overheat. External vibrators of both types are in the concreting equipment department at NORWIT.PL, alongside poker vibrators and vibrating screeds for surface compaction.

Popular external vibrator models at NORWIT.PL

Below is a cross-section of the range, from the smallest pneumatic class up to the electric model. Exact parameters — centrifugal force, air consumption, motor power — are given on the individual product pages.

The range is complemented by Husqvarna Construction external vibrators — a full overview of variants and parameters is on the product pages for this brand. For compacting the mix directly in the concrete rather than through a mould wall, see poker vibrators — the difference between the two methods is explained in the FAQ section below.

Matching external vibrator power to slab thickness and mould size

The thicker and heavier the concrete element, the greater the centrifugal force needed to compact the mix effectively through the mould wall. The Wacker Neuson pneumatic series steps up through classes from the PEV10, through the PEV14 and PEV27, to the PEV45 and PEV60 — successive models are matched to progressively larger moulds and thicker elements. Thin slabs and elements with a cross-section of up to around 8–10 cm are handled by the smallest class, while thick floor slabs, precast walls or structural elements need a higher force class.

With large moulds, one vibrator usually is not enough — manufacturers recommend distributing several units across the mould surface so the vibration covers the whole area without dead zones. Under-sizing extends vibration time and risks incomplete compaction at the mould edges, while over-sizing wastes energy and accelerates wear on mounts and bearings.

Mounting an external vibrator on formwork or a precast mould

An external vibrator is mounted at the stiffest point of the mould structure — usually a reinforced rib, frame or bracket welded or bolted to the steel mould. Mounting it on thin, flexible sheet metal wastes vibration energy and risks cracking or permanent deformation of the panel. The position is chosen close to areas of dense reinforcement and complex shapes, where the vibration needs to reach most effectively.

A pneumatic vibrator connects to the compressed-air installation through a pressure regulator usually set to around 5–6 bar, while an electric vibrator connects to a power socket matching the unit's voltage (230 V or 400 V), ideally through a residual-current device. Mounting bolts need periodic re-tightening, because working vibration loosens them over time — a loose vibrator loses effectiveness and accelerates bearing wear.

Frequently asked questions about external concrete vibrators

Why buy an external concrete vibrator at NORWIT.PL

We specialise in concrete compaction equipment: our external vibrators come primarily from Wacker Neuson — the pneumatic PEV series and the electric AR model — with the range complemented by Husqvarna Construction. We advise on drive type and force class for a specific mould or formwork, and provide servicing and parts availability. The full concreting equipment department also includes poker vibrators for work on site. Orders are fulfilled online, with delivery across the whole country.