Posted tagged ‘rotation’

Oscillating Conveyor System

September 8, 2011

Selection of vibratory conveyor:

01-vibrating conveyor-vibrating conveyor applications-vibrating conveyor belt-vibrating conveyor motor-oscillator-reciprocating conveyor-shaker conveyor-inertia conveyor

The oscillating motion of the trough is achieved via specially designed inclined arms and an eccentric shaft driven by a motor through V-belts. The eccentric shaft is mounted on anti friction bearings and has V-pulleys at both ends with weights on them to counteract the unbalancing force. The rotation of the eccentric shaft provides a forward and backward motion to a connecting arm attached to the trough through a rubberized pin. The trough motion is predominantly horizontal with some vertical component, which causes it to oscillate with a pattern conductive to conveying material. A retaining spring assembly at the back of the trough absorbs shock load. All components including drive motor are mounted on a rigidly constructed base frame.

Advantages:

· Hot and abrasive materials can be handled

· Cooling, drying and de-watering operation can be done during transport

· Scalping, screening or picking can be done

· Units can be covered and made dust tight

· Simple construction and low head room

· Can be made leak proof

Disadvantages:

· Relatively short length of conveying ( about 50m Maximum)

· Limited capacity, about 350 tons per hour for length of conveying of 30 m.

· Some degradation of material takes place.

Applications:

Vibratory conveyors find wide spread application in the transportation of dusty, hot, toxic, and chemically aggressive bulk material through a closed trough or pipe in chemical, metallurgical, mining industries and manufacturing of building materials.

Vibratory conveyors are also employed for transportation of steel chips in machine shop, hot knocked out sand, wastes and small castings in foundry shop. Vibratory feeders are also in use for delivery of small machine parts like screws, rivets etc.

Sticky materials like wet clay or sand are unsuitable for vibratory conveyors. In handling finely pulverized materials, like cement etc., the performance of such conveyors are reported to be poor.

Vibratory conveyors are hardly employed for handling common bulk loads, such as sand, gravel, coal etc as the same can be done more efficiency by belt conveyors.

MAGNETIC BEARING TECHNOLOGY

August 22, 2011

01-Magnetic_Bearing-magnetic bearing technology-active non contact position sensors

Magnetic bearings have been utilized by a variety of industries for over a decade with benefits that include non-contact rotor support, no lubrication and no friction.

Conventional mechanical bearings, the kind that physically interface with the shaft and require some form of lubrication, can be replaced by a technology that suspends a rotor in a magnetic field, which eliminates friction losses.

01-floating rotors-magnetic bearing technologies-SKF compressor drive-advanced drive system

There are two types of magnetic bearing technologies in use today – passive and active.  Passive bearings are similar to mechanical bearings in that no active control is necessary for operation. In active systems, non-contact position sensors continually monitor shaft position and feed this information to a control system.  This in turn, based on the response commanded by the system, flows to the actuator via current amplifiers.  These currents are converted to magnetic forces by the actuator and act on the rotor to adjust position and provide damping.

Additional benefits of magnetic bearings include:

  • No friction
  • No lubrication
  • No oil contamination
  • Low energy consumption
  • Capacity to operate within a wide temperature range
  • No need for pumps, seals, filters, piping, coolers or tanks
  • Environmentally friendly workplace
  • Impressive cost savings

In practice, these attractions are balanced in order to maintain a gap between the shaft (rotor) and static parts (stator). The function of the magnetic bearing is to locate the shaft’s rotation axis in the center, reacting to any load variation (external disturbance forces),


01-typical examples for Floating rotors to run a heavy machineries-magnetic bearing systems to run shaft without friction

Floating rotors could boost compressor efficiencies

Traditional centrifugal compressors are based on low-speed drives, mechanical gears and oil-film bearings, resulting in high running costs because of their high losses, wear, and need for maintenance.

This new compressor drive (above) uses a permanent magnet motor, operating at an efficiency of around 97%, to drive a rotor “floating” on magnetic bearings, which spins the compressor impeller at speeds of around 60,000 rpm. These drives experience almost no friction or wear, and need little maintenance. They also minimize the risk of oil contamination, and result in compressors that are about half the size of traditional designs.


How they work

 

01-general-magnetic-principles-monitoring the air gap of shaft and bearings contact and position-position sensor-closed loop system-controlling of shafts in center position-position controller
Magnetic bearings are basically a system of bearings which provide non-contact operation, virtually eliminating friction from rotating mechanical systems. Magnetic bearing systems have several components. The mechanical components consist of the electromagnets, position sensors and the rotor. The electronics consist of a set of power amplifiers that supply current to electromagnets. A controller works with the position sensors which provide feedback to control the position of the rotor within the gap.

01-magnetic-5 axis shaft control-radial bearings-air gap- advanced bearing technologies

The position sensor registers a change in position of the shaft (rotor). This change in position is communicated back to the processor where the signal is processed and the controller decides what the necessary response should be, then initiates a response to the amplifier. This response should then increase the magnetic force in the corresponding electromagnet in order to bring the shaft back to center. In a typical system, the radial clearance can range from 0.5 to 1 mm.

This process repeats itself over and over again. For most applications, the sample rate is 10,000 times per second, or 10 kHz. The sample rate is high because the loop is inherently unstable. As the rotor gets closer to the magnet, the force increases. The system needs to continuously adjust the magnetic strength coming from the electromagnets in order to hold the rotor in the desired position.