A safety alert has gone out about wheels flying off school mobile dental clinics.
The mobile dental clinic, minus a wheel, is loaded on to the back of a truck near Cromwell. Photo: Supplied
Twice a wheel has sheared off the heavy trailers and gone flying across the road.
The alert has only gone out now, though the first time a wheel flew off was at 90km/h on a highway near in Cromwell in 2017, and the second on Tauranga's main Cameron Rd in 2020.
In that case the wheel flew over a car and smashed into a building. No one was hurt in either case.
RNZ was sent the alert separate from Health New Zealand, which put it out internally two days ago.
"This situation is clearly unacceptable," a spokesperson told RNZ last night.
Health NZ is telling health districts to check all 23 trailers across the country and to consider taking some off the road entirely to check their wheel assemblies.
The large caravans sit on double five-tonne axles.
A photo from the Cromwell scene showed all the wheel studs had been completely shorn off - the wheel flew over the road and into Lake Dunstan.
A certifying engineer who checked the wheel wrote, "Wheel studs on stud-centered set-ups are prone to failure from loose wheel nuts.
"They are subject to cyclic stress from every wheel revolution and fail from fatigue quickly."
Health NZ has not said when it was made aware of the wheels flying off.
All the wheel studs were shorn off at the Cromwell dental van accident in 2017. Photo: Supplied
"Enquires and subsequent incident investigations concluded that the incorrect wheel assemble was attached to the hub resulting in the sheering [sic] of the wheel studs while being towed," its alert said.
Anyone towing the clinics should be "vigilant", was among its advice.
After the Tauranga case, the operator in charge of the move who saw the aftermath, raised the alarm with NZTA, over 18 months ago.
Since then the operator, fearing another failure, only moves the clinics by putting the whole trailer up on to a separate truck.
RNZ has approached NZTA for comment.
The manufacturer of the two trailers, who RNZ is not naming at this stage, said last night they "absolutely" stood by their trailers.
The trailers had been cleared in two investigations already, but a third investigation had begun, they said.
They were not aware of the Health NZ safety alert until RNZ contacted them, they said.
The clinic vans are about nine years old. They are moved regularly between schools but do not do many kilometres.
Health New Zealand this afternoon said it found out in July about the failures.
"We have prioritised establishing the exact nature of the problem, and issued this advisory as soon we were able to provide a full update to the relevant districts."
Health NZ said it expected all districts to make sure "appropriate actions are taken" and that it would follow up with them.
"Our advisory demonstrates a number of actions already taken, including remedial actions already carried out by districts, and notifications to police and NZTA."