February 2019 Design Notes

Tough transducers ensure preciseroad maintenance while reducingmachine downtime

Rota Engineering’s EL external and LA internal transducers are being used on Roadtec’s SX Reclaimer machines for road maintenance and repair.

Roadtec manufactures a variety of road building and asphalt paving equipment, relying on hydraulics for the power density and precision control it provides in cutting, paving and more. The company’s soil stabilizers and road reclaimers are well balanced and constructed with a sealed box frame to make them as durable and versatile as possible.

Used for road rehabilitation, cold recycling, or soil stabilization, different models feature hydraulically driven cutters, hydraulically driven suspension for precision cutting depths which is done easily via a push button, hydraulically adjustable doors to allow for easy access to the engine compartment, and hydraulically adjustable front and rear doors combined with optimal drum position in the cutter housing to provide sizing and material flow.

When servicing the magnetostrictive sensor buried inside the main lift of its SX model reclaimer/stabilizer machines became too difficult and time-consuming, Roadtec turned to Rota Engineering for a simpler solution. The company replaced all magnetostrictive transducers mounted on the main lift cylinder with Rota’s internal or external transducers where it was difficult to replace and maintain the transducer.

Rota’s external transducer allows for fast on-site maintenance and minimum machine downtime. This is particularly useful when the cylinder is large and well integrated into the machine, said Michael Moore, Technical Sales for Rota.

“Prior to switching to Rota Engineering sensors in 2010, Roadtec had less than satisfactory experience with magnetostrictive sensors buried inside cylinders that turned out to be difficult and time-consuming to service. To service a sensor, they had to fully remove the hydraulic cylinder from the machine using a mobile crane or skid steer loader. Servicing the sensor in the field turned out to be unfeasible in practice as the hydraulic cylinder had to be returned to a cylinder repair facility,” Moore said. “Minimizing downtime was and still is a priority in terms of Roadtec competing for market share. Another aspect to minimizing downtime is sensor reliability. With Rota designs, Roadtec has met their service level expectations.”

A look at Rota Engineering's ELA transducer installed on Roadtec's SX-4 elevation-cylinder.

Roadtec first installed Rota sensors on its SX models of its reclaimer/stabilizer, where hydraulic cylinders with linear sensors are used on elevation, cutter door height and gate, and steering. Rota sensors were later retrofitted on its cold planers and material transfer vehicles (shuttle buggies).

The elevation cylinder supports the mass of the entire machine on its cylinder pins. As such, unpinning one end of the cylinder to gain access to the sensor was not practical as either a mobile crane or skid-steer loader would have to be used to relieve the force on the pin to remove it. For the elevation cylinders, Roadtec elected to go with the Rota external linear (EL) series sensor. The Rota EL sensor allows the user to replace the sensor element without touching the hydraulic cylinder at all. Protection of the sensor is afforded by the elevation support box beam, which surrounds the elevation cylinder and sensor.

Rota’s EL sensor is suitable for steering and long cylinder applications. It uses Rota’s non-contact, Hall-effect technology, which does not require gun drilling and allows for easy on-site replacement. In this design, an internal magnet communicates with the externally mounted sensor.

Side view of Roadtec’s SX7 cutter cylinder.

In other instances, Roadtec opted to use Rota’s LA series internally integrated sensors wherever possible as the cylinder tube provides best physical impact protection for the sensor. However, serviceability of sensors was also a priority, as downtime must be kept to a minimum.

“The Rota LA series sensor provided the best solution for accommodating both protection and serviceability requirements. Where the LA sensor is used on the machine, the hydraulic cylinder can be unpinned on one end to gain access to the sensor for service and/or replacement, which is easily supported in the field,” Moore said. “Rota’s Hall Effect sensor has flexibility in mounting design to accommodate this requirement. The other primary benefit to Roadtec was superior reliability of the Rota Hall Effect sensor compared to Roadtec’s prior sensor designs. Shock and vibration are virtually constant when the machines are in operation. Rota has field proven reliability in high shock, high vibration applications.” FPW

Rota Engineering | rota-eng.com

Roadtec | roadtec.com

Environmentally friendly plug-and-playelectrohydraulic braking system

Plug-and-play electrohydraulic braking systems from Dellner Brakes were introduced to the US market at this year’s International Workboat Show in New Orleans.

Combining the very best of Swedish and German engineering from Dellner Brakes and sister company Pintsch Bubenzer, the new BUEL STL system provides a compact, self-contained solution for stopping, turning and locking ship propeller shafts on vessels of all sizes, as well as for industrial applications.

As the name suggests, the system combines elements from Dellner Brakes’ stopping, turning and locking (STL) systems with Pintsch Bubenzer’s patented BUEL electrohydraulic thruster/power package. According to Edgar Roca, VP for Dellner Brakes, “It functions as an HPU, but it requires about 70% less hydraulic oil than an HPU. It’s fully enclosed; therefore, we do not need to have any external hydraulic lines running to the system. And it allows us to power a complete stop, turning and locking system with a full enclosed hydraulic thruster.”

Because it needs no external piping, the system is compact, easy to install and, with the BUEL using only half a liter of high-performance synthetic oil (compared to as much as 30 l of hydraulic oil in standard hydraulic power units), it is cheaper to run and environmentally-friendly too. “You don’t have to worry about any hydraulic fluid leaking. In the marine industry there’s a lot of concern — normally a lot of the brakes take their fluid from the water system — and there’s a concern there that they think the brake might take too much fluid and then you may have a steering problem,” Roca said. “So this eliminates that, cuts out the concern, and you have a fully enclosed hydraulic system directly to our braking.”

Dellner’s BUEL STL system provides a compact, self-contained solution for stopping, turning and locking ship propeller shafts on vessels of all sizes, as well as for industrial applications.

At its simplest, the new system combines a Pintsch Bubenzer BUEL Model G, delivering up to 240 bar of pressure, with a powerful Dellner disc brake offering stopping force of up to 517 kN per unit. Customers can then choose to add a Dellner locking device that, available with hydraulic, electric or manual power, can deliver locking force of up to 1,300 kN. Customers requiring a full STL system can then also add a Dellner electrical continuous turning device, which uses an electric gear wheel to move the brake disc and attached shaft to any position – forwards and backwards – or turn the disc continuously, all with variable speed and turning force of up to 157 kN. A system with the above configuration and a 2.25 m diameter brake disc will provide 550 kNm stopping torque, 1,450 kNm locking torque and 155 kNm continuous turning torque (intermittent breakaway 233 kNm).

The stopping, turning and locking functions can be operated individually or as a fully automated system. There is also a wide range of options for the system interface, from manual hand operation to electronic control panels and even remote wireless operation through a smartphone or tablet — whatever the customer needs.

Roca said the BUEL STL is ideal for workboats, such as tugboats, icebreakers, and military vessels. “We really see it being a game changer for us on the work boats because of the fact they want small, compact shaft braking systems, yet they don’t want to do any modifications to the external hydraulic system,” he said. “They want to have a fully enclosed system, without having to take fluid and pressure from the motor system.”

Dellner Brakes’ STL systems fit around the ship propeller shaft to enable faster directional changes with maximum maneuverability. They also help lower fuel consumption, reduce the load on propulsion systems and make routine maintenance quicker, easier and safer. Securing the propeller prevents damage to the shaft and bearings if the vessel is drifting or buffeted by waves.

It also allows ROVs and divers to operate around the propeller blades in safety. When in the harbor, using the turning function to rotate the propeller can also help to reduce marine growth on the blades and lubricated shaft bearings. Roca said the BUEL STL can also be used in oil and gas, mining, port, and paper as well as any other type of industry that might require any type of emergency stopping, braking, turning solutions.

Dellner Brakes | dellner-brakes.com

Dellner’s BUEL STL functions as an HPU but uses70% less hydraulic oil than a standard HPU. Thethe self-contained system also eliminates leakage.