Rotating unions are used to convey various media into and through rotating machine parts. Media such as water, hydraulic or thermal oil, compressed air, vacuum and coolants can be conveyed.
In the case of current rotating unions, sealing between the rotating element, the rotor, and the stationary part, the stator, is almost always achieved using suitable mechanical seals.
Despite extremely precise production and the use of highly wear-resistant materials, each rotating union is inevitably subject to wear.
Over and above the technical parameters which limit the service life of a rotating union, such as speed, pressure, temperature, flow, volumes and flow velocity of the media, other factors have considerable impact on service life.
Correct mounting is also an important factor influencing the service life of a rotating union. To prevent damage to the bearing it is important that the union can be easily rotated in mounted condition without any warping. Improper hose length or threaded parts may cause warping of the bearings.
The installation of the hoses is very important. The flexible hose should be attached to the rotating union and then connected to the shaft end and tightened to the prescribed torque. When connecting the flexible hose to the solid pipe, avoid twisting of the hose. Never connect the rotating union to a solid pipe. The hoses should be installed with a bow and without torsion and should be connected to the stationary pipe in a pressure-tight manner. The rotating union should also be connected to the machine part in a pressure-tight manner and at the torque prescribed by the manufacturer. It is important that the retainer for the rotating union is free from burrs or chips.
If required, the drainage must always be laid downwards (at least 15°) and with a free cross-section which is as large as possible. In the case of a rotating union installed vertically, the drainage must be guided downwards. For rotating unions which are mounted horizontally, the vent for controlled leakage must point downwards, in 6 o’clock position.
If the drainage is located higher than the vent, the rotating union will be flooded by the occurring leakage causing improper operation.
Listening to and observing a rotating union immediately after the initial operation quickly reveals incorrect installation. If it runs untrue or tumbles, the centring is not within the tolerance. This may be the result of wear of the screw thread or of a mounting failure. If the rotating union is noisy, vibrates or is hot in the area of the bearing it indicates that there is warping caused by the installation and that the rotating union is not running freely.
If these installation errors are avoided or are eliminated immediately the user benefits from an extended service life which is not reduced as a result of poor assembly.
This precision part operates highly effectively and helps to reduce machine downtime and maintenance costs in most cases.
For more information contact Pneumatic Electric Control Systems (PECS), +27 (0)31 303 3701, [email protected], www.pecspower.co.za
© Technews Publishing (Pty) Ltd | All Rights Reserved
printer friendly version