Introduction
Shangri-La Hotels and Resorts is a Hong Kong-based multinational hospitality company. Shangri-La Hotel Singapore is the first so-called pioneer property of the Shangri-La group, with 792 rooms and suites spanning three distinct wings, such as the Tower Wing, Garden Wing, and Valley Wing, and serviced apartments and residences in four-story villas.
Since 2015, SPM Instrument Asia has been providing condition monitoring measuring services as part of the Predictive Maintenance (PM) in Hotel Shangri-la. During that service, SPM has successfully detected equipment problems, helped to correct equipment faults, and prevented unplanned or sud- den breakdowns.
SPM Instrument works together with the hotel’s facility maintenance engineering team, conducting alternate monthly routine monitoring of various equipment, including chillers, air handling units, ex- haust fans, cooling towers, pumps, and motors.
This report describes how SPM Instrument Asia performed vibration analysis and on-site dynamic balancing for one of the Air Handling Units (AHU) for Shangri-La Hotel Singapore.
Conclusion and summary
During the routine condition monitoring measuring service, it was found that the AHU was not in an acceptable balance condition. The maximum vibration level of the running speed at the Fan Drive End (vertical) location was 20.60 mm/sec RMS, and Fan Non-Drive End (vertical) location was 19.18 mm/sec RMS.
This symptom is associated with the dynamic imbalance condition of the Fan Drive End (refer to spectrum in Image 6) and Fan Non-Drive End (refer to spectrum in Image 8). Final masses of 247 grams were added to the external radius of the fan impeller to correct for the out-of-balance force.
The vibration level at the same fan location after balancing for Fan Drive End (Vertical) was 3.54 mm/sec RMS (refer to spectrum in Image 12), and Fan Non-Drive End (Vertical) was 4.58 mm/sec RMS (refer to spectrum in Image 14). Dynamic balancing has improved the condition of the equipment. After the balancing job was done, vibration levels are within the acceptable facility and ISO standards.
Application description
The main function of the air handling unit TW-AHU-24-1 is to take in outside air, re-condition it, and supply it as fresh air to the Tower Wing corridors from levels 6 to 24 in the Shangri-La Hotel. All ex- haust air is removed, thus creating acceptable indoor air quality. The unit is one of the critical pieces of equipment for the hotel, operating 24/7. There is no redundancy for this particular unit.
Background
The challenge is that the unit operates 24/7 and can only be turned off after 10:00 pm for 2-3 hours. Hence, it is very difficult to schedule any necessary balancing correction jobs.
Figure 1 The Shangri-La Hotel and location of the AHU in this case study.
System setup
Measuring equipment
Three DuoTech transducers are installed (shown in Figure 2 below):
- at the motor drive end (MDE) – horizontal direction,
- at the fan drive end (FDE) – vertical direction,
- and the fan non-drive end (FNDE) – vertical direction
The handheld instrument Leonova Diamond instrument was used to take the SPM HD and vibration readings via a remote monitoring junction box.
Figure 2 Transducer positions and the measured parameters.
Measuring techniques
For measurement, the handheld Leonova Diamond instrument with HD condition monitoring tech- nology was used; SPM HD for bearing (SPM Spectrum) and lubrication condition, and vibration ve- locity for finding and trending the development of mechanical faults such as imbalance, misalign- ment, and looseness, etc.
Due to the overhung centrifugal fan, balancing was carried out with the dual-plane method using two SLD144 vibration transducers and a tachometer for a portable RPM reference.
Figure 3 Example of an Air Handling Unit fan.
Image 1 Two-plane balancing setup in Leonova Diamond.
Dual plane method procedure
The standard operating procedure for dual-plane balancing with Leonova Diamond is as follows;
Figure 4 Dual plane balancing procedure.
Before applying the correction weights, the rotational direction and number of blades must be de- fined (in this case, there are eleven blades).
Image 2 Two-plane balancing setup in Leonova Diamond.
Equipment information and balancing weights
- Motor specifications: Shandong Huali electric motor, 30 kW and 1470 RPM
- Fan blade: 11 blades, fan running speed 780 RPM
- Trial weights at planes 1 and 2: 50 g at blade no.1
- Mounted weights and locations,
- Fan drive end: 59 g at blade no.
- Fan non-drive end: 1 149 g at blade no. 11 and 39 g at blade no.1
Image 3 Balancing weights on the drive and non-drive ends.
Before and after balancing results
The vibration results for the original condition prior to balancing are as follows.
Table 1 Summary of vibration levels before and after balancing.
The imbalance 1st order level at the MDE, FDE, and FNDE condition prior to balancing are as fol- lows.
Table 2 Summary of imbalance levels (1st order) before and after balancing.
Spectrum and time signal readings
Before balancing
Measuring point location: Motor Drive End (MDE)
Measuring date: 09.06.2021
Overall vibration RMS value = 7.13 mm/s
Image 4 Spectrum of MDE before balancing.
Image 5 Time signal of MDE before balancing.
Measuring point location: Fan Drive End (FDE)
Measuring date: 09.06.2021
Overall vibration RMS value = 20.60 mm/s
Image 6 Spectrum of FDE before balancing.
Image 7 Time signal of FDE before balancing.
Measuring point location: Fan Non-Drive End (FNDE)
Measuring date: 09.06.2021
Overall vibration RMS value = 19.18 mm/s
Image 8 Spectrum of FNDE before balancing.
Image 9 Time signal of FNDE before balancing.
After balancing
Measuring point location: Motor Drive End (MDE)
Measuring date: 13.10.2021
Overall vibration RMS value = 3.82 mm/s
Image 10 Spectrum of MDE after balancing.
Image 11 Time signal of MDE after balancing.
Measuring point location: Fan Drive End (FDE)
Measuring date: 13.10.2021
Overall vibration RMS value = 3.54 mm/s
Image 12 Spectrum of FDE after balancing.
Image 13 Time signal of FDE after balancing.
Measuring point location: Fan Non-Drive End (FNDE)
Measuring date: 13.10.2021
Overall vibration RMS value = 4.58 mm/s
Image 14 Spectrum of FNDE after balancing.
Image 15 Time signal of FNDE after balancing.
