A pallet stacker is the machine that fills the gap between a pallet truck and a forklift: it lifts a full pallet to height, but the operator walks with it rather than rides on it. That middle position is exactly why it gets used badly. Most people who are handed one have used a pallet truck before, and a good deal of what they learned there is actively wrong on a stacker.
This guide covers how a pallet stacker works, how to operate one safely, the four mistakes that cause almost all of the incidents, and what UK law actually requires in terms of training. We supply the stackers themselves — manual hydraulic, semi-electric and fully powered — and we are not a training provider, so where the honest answer is "get your operators onto an accredited course", the guide says so and points you at the right bodies.
One thing to get straight before anything else, because a good deal of the material online blurs it: a pallet stacker is not a pallet jack, and instructions written for one do not transfer to the other. If what you actually have is a pallet truck, read how to use a pallet truck safely instead. If you are not yet sure which machine the job needs, start with pallet stacker vs pallet truck.
How a pallet stacker works
Every stacker has the same four elements: a mast, a set of forks that run up the mast, a chassis with supporting legs or a counterweight, and a tiller — the steering and control handle the operator walks behind. The load is lifted by a hydraulic ram, either pumped by hand or driven by an electro-hydraulic power pack.
The part that matters operationally is the chassis, because it decides what the machine can reach. Broadly there are three arrangements:
- Fixed-leg (fork-over) stackers have two supporting legs running forward underneath the forks. Stable and compact, but the legs sit under the load, so the pallet has to be one the legs can pass beneath, and the machine cannot deposit a pallet flat on the floor against a wall or into a low rack position where the legs have nowhere to go.
- Straddle stackers have wider legs that straddle around the pallet rather than under it. That solves the closed-board and floor-level problem, and on adjustable models the leg spread can be set to the pallet — but the overall width goes up, so gangways and rack apertures need checking.
- Counterbalance stackers have no forward legs at all; the battery and chassis weight balance the load, exactly as on a counterbalance forklift. That lets the machine drive straight up to a rack face or a bench, at the cost of a longer, heavier truck and a higher price.
In our range that maps onto real machines. The VULCAN Hydraulic Stackers (STHI21Y, STHI23Y, STHI24Y) are fixed-fork units, 1000 kg to 1600, 2500 or 3000 mm lift, with lifting controlled by a hand-pumped hydraulic ram and mobility on 180 mm swivel rear castors and 75 mm front rollers. The VULCAN Hydraulic Straddle Stackers (STHI26Y, STHI27Y, STHI28Y) are the same capacities and lift heights with manually adjustable forks and straddle legs. Both conform to EN 1757-1.
Step up and the lift becomes powered while the travel stays manual. The VULCAN Semi Electric Stacker (SESCT10) is a 1200 kg, 1600 mm machine with a 12 V/150 Ah battery and built-in charger, on 180 mm steering wheels with foot guards and 74 mm tandem rollers. The Semi Electric Straddle Stacker (PSS16E, PSS20E, PSS30E, PSS35E) adds adjustable forks and straddle legs giving an overall width of 1100 to 1380 mm, a 1150 mm fork length, a 600 mm load centre, a 1350 mm turning radius and a 1500 W electro-hydraulic power pack, to EN 1757-2. Fully powered VULCAN stackers, straddle stackers and counterbalance stackers take both travel and lift onto the battery.
Before you start: the pre-use check
This takes a couple of minutes and it is a legal expectation, not good practice. Under the Provision and Use of Work Equipment Regulations 1998 the equipment has to be maintained in efficient working order, and a daily check is how that gets evidenced on the shop floor.
- Forks and mast — no cracks, no bent or splayed fork tips, chains evenly tensioned and not obviously stretched, guarding in place. Tandem lift chains on our straddle stackers are fully guarded; if a guard is missing, the machine is out of service.
- Hydraulics — no weeping at the ram or hoses, and the forks hold their height when raised rather than creeping down.
- Wheels and rollers — free-running, not flat-spotted, nothing wound round the axles. Foot guards present where fitted.
- Brake and tiller — the tiller returns to the braked position when released, and the brake actually holds on the gradient you work on.
- Battery and charge state on powered machines, plus the discharge indicator.
- Capacity plate — legible, and matched to the load you are about to lift.
Anything that fails, the machine is tagged and taken out of use. A stacker with a slow-creeping ram is not "a bit tired", it is a machine that will lower a pallet on its own while somebody is underneath it.
Operating a pallet stacker: the sequence
- Check the load first, not the machine. Weight against the capacity plate, pallet in sound condition, load stable and within the footprint. A damaged pallet is the single most common cause of a load shifting during a lift — our guide to stacking and storing pallets safely covers what to reject.
- Square up. Approach the pallet straight on, not at an angle. A stacker has far less fork clearance to play with than a forklift and correcting a skewed entry at height is not an option.
- Set the forks. On adjustable models, set the fork spread as wide as the pallet allows — the wider the forks, the more of the load is supported and the less it can rock. On straddle models, set the legs to clear the pallet before you move in, not after.
- Enter fully. The forks go in to the heel, so the load sits back against the mast. A load carried on the fork tips is the classic overload: the same pallet at the wrong load centre is a different, much heavier lift as far as the machine is concerned.
- Lift just clear. Raise the load only enough to clear the floor — normally 50 to 100 mm — and stop. Check the load has not shifted.
- Travel with the load low. This is the rule that gets broken most and matters most. See below.
- Stop square at the destination, then lift. Bring the machine to a complete stop, apply the brake, and only then raise to the deposit height. Never raise and travel simultaneously.
- Deposit gently. Lower the load onto the beams or the stack until the forks are free, pause, then withdraw slowly and straight. Do not use the mast to shove a pallet further into a rack bay — that loads the beams sideways and it is how uprights get knocked out of plumb.
- Lower fully and park. Forks down, brake on, key out on powered units, machine parked clear of gangways, fire points and pedestrian routes.
The four things that actually go wrong
1. Travelling with the load raised
A loaded pallet at 2500 mm sits a long way above a chassis that is only a metre or so wide, and the whole assembly becomes something that wants to fall over sideways. Every stacker is designed to travel with the forks at travel height and stack from a standstill. The habit that causes the problem is imported directly from pallet-truck work, where the load never leaves knee height and "just nudging it across while it's up" carries no penalty. On a stacker it is the main mechanism of a tip-over, and the operator is on foot beside the machine when it happens.
The corollary is turning. Turn with the load down. A turn is where lateral force is highest, and it is the moment a raised load is least forgiving.
2. The straddle-leg geometry mismatch
This is the fault that traces back to the purchase rather than the operator. A fixed-leg stacker needs the legs to pass under the pallet, so it will not take a closed-board pallet or a pallet standing on the floor with a solid deck. Operators who meet that wall usually solve it by lifting from the tips, or by wedging the pallet up on a second pallet — both of which are worse than the original problem.
If the site handles mixed pallet types, specify straddle legs from the start. Our adjustable-leg models set to an overall width of 1100 to 1380 mm, which covers standard UK and euro pallets, and the counterbalance machines remove the constraint altogether by having no forward legs at all. Getting this right at specification is why it is worth reading UK pallet sizes explained before you order rather than after.
3. Reading the capacity plate as a single number
A stacker rated at 1000 kg is rated at 1000 kg at its stated load centre — 600 mm on our semi-electric straddle models. That figure assumes the centre of gravity of the load sits 600 mm forward of the fork face. Push it further forward, with a deep load or an overhanging one, and the safe capacity falls away, and the plate will not tell you by how much. Several machines also derate with lift height.
The honest position is that this is a manufacturer's load chart question, not something to estimate on the floor. If your loads are deep, long or unevenly packed, ask us for the load chart for the specific model before you commit to it. Our guide to load ratings explained covers how these figures are constructed across the whole range.
4. Floor condition and gradients
Stackers run on small wheels — 180 mm steering wheels with 74 to 100 mm load rollers is typical of the range. That gives a compact machine with a tight turning radius, and it also means the machine is far less tolerant of a broken floor joint, a drainage channel or a raised expansion strip than a forklift on pneumatic tyres. A wheel dropping into a joint at travel speed transfers the shock straight into a raised load.
Gradients deserve their own rule. Travel with the load on the uphill side and take slopes straight, not at an angle. Where the route involves a loading bay level change, the right answer is usually a proper access ramp or a level loader, not a stacker asked to work on a slope it was never rated for.
Stacking into racking
Two extra points once the destination is a rack rather than a floor stack. First, deposit onto the beams so the pallet bears on both beams evenly, with the load lowered rather than pushed. Second, be honest about the reach: a stacker's usable stacking height is the lift height minus the free lift you actually have and the clearance the load needs above the beam, so a 3000 mm machine does not put pallets into a 3000 mm beam level.
Impact damage to uprights is the predictable long-run cost of pedestrian stacker work in racking, because the operator's sightline down the mast is poor at height. Upright protection at the aisle ends and column guards on the first bay pay for themselves; see pallet racking protection. Any impact — however minor it looks — goes into the rack damage report and gets checked, per warehouse racking inspection under SEMA and HSG76. If you are still specifying the racking itself, our pallet racking buying guide and the pallet racking range cover beam levels and load ratings.
Batteries, charging and the lift cut-out
On semi-electric and fully powered machines the battery is a daily operational item, not a background one. Our semi-electric models carry a 12 V/150 Ah battery with a built-in automatic charger; the fully powered stackers run 2 × 12 V/85 Ah as standard, with larger 2 × 12 V/106 Ah packs available, and a built-in charger with a battery discharge indicator. The fully powered counterbalance machines use an external charger, which means the truck can be charged from any convenient UK three-pin socket, on a heavy-duty traction battery giving eight to nine hours of continuous work.
There is one behaviour worth briefing operators on explicitly, because it reliably catches people out: the discharge indicator has an automatic lift cut-off. The machine stops lifting before it stops driving. An operator who finds the mast will not raise has not broken the stacker — the battery has reached its cut-off point and the truck has protected itself, and the correct response is to put the load down, drive it to the charger and plug it in, not to keep pumping the control.
Charge in a designated, ventilated area, and if you are consolidating charging for several machines, look at proper battery charging and storage provision rather than an extension lead in a gangway.
Training: what UK law actually requires
There is no such thing as a pallet stacker licence. That is the short answer to the question everybody asks, and it is where a lot of people stop reading — which is a mistake, because the actual requirement is stricter than a licence in one important way.
Regulation 9 of PUWER 1998 requires that anyone who uses work equipment has received adequate training in its use, the risks and the precautions. The duty sits with the employer, it applies to every operator including agency and temporary staff, and it is not discharged by a colleague showing somebody the controls for ten minutes. HSE's approved code of practice for lift-truck operator training, L117, sets out the recognised structure — basic training, specific job training and familiarisation on the actual site and machine — and while it is written around rider-operated trucks, employers commonly apply the same three stages to pedestrian-operated stackers because it is the benchmark an inspector will recognise.
Training is delivered by accredited bodies, not by us. In the UK the recognised accrediting organisations for lift-truck operator training include ITSSAR, RTITB, AITT, NPORS and Lantra; any of them will confirm the correct course category for the specific machine you are buying. Refresher training is normally recommended on a three-to-five-year cycle, and sooner after an incident, a change of machine or a change of duties.
Separately, a stacker is lifting equipment, so LOLER 1998 applies alongside PUWER: thorough examination by a competent person at the statutory interval, in addition to your own maintenance and daily checks. Your insurer's engineering surveyor will usually be the competent person, and they will confirm the interval that applies to your machine and duty.
When a stacker is the wrong machine
Worth saying plainly, because it argues against a sale we would otherwise make.
- Long horizontal runs. A stacker travels slowly and, on manual and semi-electric models, is pushed. If the job is mostly moving pallets across a big floor with only occasional lifting, a powered pallet truck will do more work per shift — see manual vs electric pallet trucks and the electric pallet truck buying guide.
- High-throughput racking work. Above a certain pick rate and beam height, a rider-operated truck is the right tool. We do not sell forklifts, and we will say so rather than sell you a stacker that will be run beyond what it is comfortable doing.
- Repetitive lifting at bench height. If the real problem is people bending to a pallet all day, a scissor lift table or level loader solves it better and cheaper than a stacker being used as a hoist.
- Lifting people. Never. A pallet stacker is not an access machine under any circumstances. Where people need to work at height from a truck, that is a purpose-built cage on a suitable forklift — see forklift man cages and the UK rules on lifting people — or, more often, a set of mobile safety steps.
Frequently asked questions
How does a pallet stacker work?
A hydraulic ram, pumped by hand or driven by an electro-hydraulic power pack, raises a pair of forks up a mast. The operator walks behind and steers using a tiller handle. The chassis is stabilised either by supporting legs that run under or around the pallet, or by a counterweight in the case of counterbalance stackers. Travel is either manual push, powered, or manual with powered lift on semi-electric machines.
Do you need training to use a pallet stacker?
Yes. Regulation 9 of PUWER 1998 requires that anyone using work equipment has received adequate training in its use, its risks and the precautions to be taken, and that duty rests with the employer. It applies to permanent, temporary and agency operators alike.
Do you need a licence or certificate to operate a pallet stacker?
There is no legal licence for a pallet stacker in the way there is for driving on the road. What employers use instead is a certificate of basic training from an accredited body — ITSSAR, RTITB, AITT, NPORS or Lantra — followed by specific job training and site familiarisation. That certificate is the evidence that the PUWER duty has been met; it is not a licence and it is not transferable between machine types without checking the category.
What is the proper procedure for stacking a pallet with a stacker?
Approach square, set the fork spread to the pallet, enter fully to the fork heel, lift just clear of the floor, travel with the load low, stop completely and apply the brake at the destination, then raise to the deposit height, lower the load onto the beams or stack until the forks are free, and withdraw straight and slowly before lowering the mast fully.
How high can a pallet stacker lift?
It depends on the model. Our manual hydraulic and hydraulic straddle stackers are available at 1600, 2500 and 3000 mm lift heights at 1000 kg; the semi-electric straddle range covers 1600, 2000, 2500 and 3000 mm raised height. Remember that usable stacking height is lower than the quoted lift height once you allow for the clearance the load needs above the beam.
What is the difference between a stacker and a forklift?
The operator walks with a pedestrian stacker rather than riding it, which makes the stacker lighter, narrower, cheaper and better suited to confined spaces and lower throughput. A forklift carries a rider, travels faster, handles heavier loads at greater heights and is far more productive over a shift. A counterbalance stacker sits between the two: no supporting legs, but still pedestrian-operated.
Specifying the right machine
If you are choosing rather than operating, the order of questions is: what pallets do you handle (which decides fixed-leg, straddle or counterbalance), what is the heaviest load and where is its centre of gravity, what is the highest beam level you must reach, how many lifts per shift (which decides manual, semi-electric or fully powered), and what condition is the floor in. Browse the full pallet stacker range or talk it through with us — our team are former engineers, and we would rather specify the machine correctly than sell you a lift height you will not use.