Power take-off (PTO) driven equipment may not be always in daily use by most landscapers but it poses a significant risk when tractor-driven implements, such as wood chippers or flail mowers, are in action, writes Adam Hubbard, product specialist at parts and accessories technical wholesaler Kramp.
And when accidents involving them occur, results can be catastrophic, he cautions.
A 2015 US study found that 40% of PTO entanglements resulted in fatalities and a further 40% involved amputations.
“A strong person can generate about three-quarters of a horsepower, whereas a tractor transmits nearly all of its horsepower into the PTO shaft,” Adam explains.
“Even with a compact tractor generating just 40 hp, if entanglement occurs, a PTO shaft can wrap an arm or leg around it nine times in less than a second.”
Adam is one of a team of product experts based at Kramp’s Biggleswade head office that supports end users and dealers with tailored training courses and technical queries. “Several of us have operated the same machinery, so we understand the practicalities and can offer these to landscaping contractors on request,” he says.
Adam’s specialism in transmissions and PTOs has allowed him to develop steps that those working with PTOs in landscaping can take to keep themselves safe while working with them.
Starting point
To alleviate risk, he recommends starting with the tractor. Before working on a PTO, ensure it is made safe, set the handbrake fully on, put all controls and gears in neutral, stop the engine, and re
move the key. Most PTO accidents occur because operators fail to take these safety measures, Adam reports.
“It’s always best to maintain a PTO before and after it is last used, before taking a break, or at the end of the day. A quick visual check of the guard and chain, to ensure it is sufficiently greased, may be all that’s needed mostly. Also, check that the PTO guard is secured to the PTO,” he adds.
To protect the PTO guard from unnecessary wear, Adam has a tip for landscapers that’s often overlooked.
“When hooking up the chain, double it back through the D-link and hook it on to itself. This will shorten the chain length and prevent it from being wrapped around the guard tube.
“The guard should then only be able to turn 90 degrees with the available slack on the chain. If it is much more than that, it will wrap around the shaft and eventually wear through it, requiring replacement,” he explains.
New regulations for PTO connections
Landscapers should be aware of the EN12965 standard, Adam advises. The EU legislation came into force shortly before Brexit and was copied into UK law. Only collar locks are allowed on the primary drive shaft connected to the tractor, meaning push-pin or certain collar locks with exposed springs are prohibited on new machines.
“Push pins may be used on second-hand machines but it is imperative for new machines or repairs that an authorised collar lock is fitted. If a new machine is delivered, I recommend that a landscaper verify the PTO connection is compliant. They can contact their local dealer or Kramp for advice if unsure which is legal for a replacement.
“The other statutory requirement to be aware of is for the PTO guard to overlap the joint by a minimum of 50 mm when in a straight position to ensure the guard covers moving parts,” adds Adam.
Reducing wear
The most common cause of PTO failure is an insufficient overlap of the PTO profile tubes, Adam says. “When the PTO is correctly installed, the overlap should be ISEKI – Stowe School – SXG 326 2 less than 33% longer than the shaft length. In practice, a closed shaft measuring 1,000 mm should have a working length of less than 1,330 mm. I recommend that the maximum closed centre length is at most 1,410 mm due to vibration.”
If the PTO is installed and there is insufficient overlap, excessive vibration will result when the PTO is operating, he says, producing a whipping motion, which adds stress to the universal joint. “In the most extreme cases, heat generated from this force can cause catastrophic failure.”
Avoid using PTO adaptors on the main drive and limit the maximum power they transmit to less than 30 kW, Adam urges. “An adaptor is an additional point in the drivetrain and can cause excessive vibration. Instead, to be safe, change the PTO yoke to suit the implements it needs to operate.”
All new operators driving a tractor powering a PTO must be fully briefed on PTO safety, Adam states, “because otherwise, they may not know any different and how dangerous a PTO can be.
“This is especially important in the landscaping sector, where regular PTO use may be uncommon. Even more experienced operators should also be wary of complacency and treat a PTO seriously and with their full attention,” he concludes.
