Vibration Control System at High Speed Elevator Banyan Garden Phase II

The Problem

Fig2. Typical Floor Layout at Block 8

Fig1. Banyan Garden at Lai Chi Kok

Banyan Garden, a prestigious residentialdevelopment located nearby LaichikokMTR station. It is made up of seventowers with height between 46 to 56storeys. The development was dividedinto two construction phases andcompleted in April, 2004.

Banyan Garden is a high-risedevelopment, traveling speed for someof the elevators in this development arehigh speed elevator and reaching4.5m/s at speed. As noise and vibrationgeneration due to operation ofelevators is proportional to their speed,nuisance to the residences at building isa concern at the very beginning ofdesign stage.

Figure 2 is a typical layout for Block 8 ofthe captioned development. Lift shaftwall is the partition wall betweenelevators and residential premisesadjacent to it. Space saving concepthas driven the architect to trim shaft wallthickness to maximize the usable areaat adjacent dwellings.

As thinner walls and lighter concretestructure are more effective intransmission of vibration and noiseenergy, consequent re-radiation ofnoise to sensitive zones, e.g. bedrooms,would be an inherent problem. Fromour measurement at past cases, forelevator moving at some 2.5m/s speed,the re-radiated noise at shaft walls tosensitive zone would be as high as40dB(A) to 45dB(A) that may causedtremendous complaints.

System Employed

Fig3. Sylomer® Special PUR Pad at Lift Tractor Machine Base

Fig4. Close view on Sylomer ® Special PUR Pad at Lift Tractor Machine Base

Fig5. Sylomer® Special PUR Pad at Lift Rail Brackets

Basically the system could be dividedinto two parts, (1) Elevator MachineVibration Isolation; and (2) Guide RailsVibration Isolation.

(1) Elevator Machine Vibration Isolation

Figure 3 shows the use of 50mmthickness Sylomer® material at liftmachine base support.

Sylomer® is a mixed cell PUR-Elastomerthat offers Quasi-Static Load Deflectioncharacteristic. When the material issubjected to load higher or lower todesign range, its mechanical behaviorbecome stiffer that exhibit smallerdeflection, i.e. higher stability. While atdesign load range, the materialbecome softer and yields a higherefficiency in vibration control.

(2) Guide Rails Vibration Isolation

The higher the elevator speed, themore vibration generated at liftguide rails. For lift speed upto4.5m/s, guide rail vibration becomesa significant factor to the noisegenerated due to vibrationtransmitted at lift shaft walls. TheSylomer® PUR-Elastomer pad again isused at rail support bracket, itdecouples the mechanical contactsbetween upper and lower bracketsand for the reduction of highfrequency vibration transmission ontoinner lift shaft walls. Figure 5 showshow this pad is inserted.

System Performance

Measurement position

Fig7. Measurement Results at Vertical Wall 47/F

At machine base 80 Hz 82dBV R.M.S. (0.32mm/s)

On Lift room floor 80 Hz 45dBV R.M.S. (4.52x10-3mm/s)

Measurement position

Fig6. Measurement Results at Lift machine Room

1/3 Oct. Freq

Measured Vibration Level Location

We have enaged the Wilson, Ihrigand Associate- Hong Kong Limited(WIAHK) to conduct vibrationmeasurement at lift machine roomsand at residential premises adjacentto lift shaft on 47th Floor at Block 8.

The significant reduction in vibrationlevels between the measurement onbase support and on floor of liftmachine room has given us a prooffor the effectiveness of Sylomer® PUR-Elastomer.

Base Support Pads

Significant reduction was recorded atfrequency higher than 12Hz. At mostcritical frequency, the reduction wasalmost 40dBV re µin/s (over 98%vibration isolation) for the lift machinebase isolation (See Figure 6 formeasured vibration level variouscheck points).

Measured Vibration Level :

Guide Rail Pads

Measured Vibration Level :

< 50dBV R.M.S. (max.)from 1Hz to 2000Hz

( < 8.03 x 10-3 mm/s R.M.S. )

Measured Noise Level :Less than 40dB(A) at residential premises