2 Channel Non Destructive Testing Equipment Data Collector Transfer Function Analysis Handheld Vibration Monitor

2 Channel Data Collector / Analyzer / Balancer HG904 Data Collector Transfer Function Analysis

Imbalance is one of the main causes of machine vibration. It is estimated that about 50 percent of all the faults are caused by imbalance of rotors. The best mean for getting rid of mechanical imbalance is on-site balancing. HG904 Machinery Analyzer/Balancer is especially useful for this purpose. It can measure the intensity of the vibration; diagnose vibration cause by analyzing the frequency spectrum. It can also be used to measure the rotation speed and vibration phase, and to calculate the imbalance weight and location.

Features:

• Easy to use
• Vector illustration, the balancing process and result are shown clearly at a glance
• Storage of 10 rotors balancing data
• Selectable of trial mass remove or remain
• Decompose of balancing result to two assigned location
• Trial weight range calculated according to the weight of rotor, rotation speed, radius and required balance grade
• Trial mass validity judged automatically
• Measuring RPM, amplitude and phase
• On-site 400 lines FFT spectrum and diagnosis function
• Dual-channel simultaneous data collection
• Hardware envelop demodulation for bearing and gear diagnosis
• Transfer function for measuring natural frequency
• Waveform and spectrum display by large LCD
• Storage of vibration values and vibration waveform

Operation condition

• Temperature range: from 5°C to 50°C
• Relative humidity: < 85%, unsaturated
• Without caustic gases
• Without strong electric-magnetic field & strong impact

Safety

The HG904 are not permitted to contact with running part of machine.

Specifications:

• Rotation speed range for dynamic balancing: 70-60,000 r/min
• Auto-range and manual-range selectable
• Measuring accuracy of vibration: 5 %

l Sensors: Piezoelectric accelerometer, Magnetoelectricity velocity, Eddy displacement and etc.

• 8^th-order ellipse anti-aliasing filter, RPM band-pass filter
• Input signal: Accelerometer, and voltage

• Amplitude spectrum analysis: 100 lines to 400 lines (zoom), Hanning windowed
• Frequency span of spectrum analysis: 100, 200, 500, 1K, 2K, 5K, 10KHz(only for 1-channel sampling)
• Data storage: 400 waveforms of 1024-points and 400 data sets

• Amplitude ranges & Frequency Response for overall vibration measurement:

• Notepad: 10 condition codes for visual inspection
• Output: USB for communication with PC
• Power: Ni-MH rechargeable battery for 8 hours continuous operation, low battery warning
• Operating Environment: 0~55 ^oC, 90% humidity non-condensing
• Rotating speed measurement with photocell sensor
• Dynamic Range: 60dB with 48dB adjustable gain range
• Dimensions: 21×13×4 cm; Weight: 1.2 kg (Include batteries)

HG904 Pack List

HG904 Vibration Data Collector 1
Accelerometer 2
Magnetic Mount 2
Steel Extension Probe 1
Battery Charger 1
Accelerometer Cable 3
RS232c Communication Cable 1
Balancing Module 1

Tacho/Trigger Sensor and cable 1
Reflector Paper set 1
Quick Start Guide 1
Software CD 1
Certificates of HG904 and sensors 3
Carrying Case 1

BALANCE PRINCIPLES

What is 1-plane rotor imbalance?

Rigid rotor works under the speed far less than its first-order critical rotate speed and its deformation can be neglected. When the quality of the rigid rotor nearly focuses on a disc, namely the ratio of its axial length and its diameter is less than 0.5; we can do 1-plane balance on it and gain satisfactory result.

But for the flexible rotor, the deformation cannot be neglected. So its method of balance differs from rigid rotor. However, the rotor with single imbalance plane can also be balanced according to the method of 1-plane balance of rigid rotor. For above, whether the rigid or flexible rotor, its quality of imbalance always focuses on one disc, so both of them can be balanced according to the method of 1-plane rotor balance. In the plant and manufactory, such rotating machines are ubiquitous, such as pump, ventilator etc.

Principle of 1-Plane Balancing

HG904’s 1-plane balance adopts the method of influence coefficient, which is also called balance method of 1-plane phase measuring. Just as its name implies, it’s desirous to do the measurement with the phase of rotation-speed vibration when measuring the vibration amplitude of rotor. The rotation-speed vibration can be indicated as vector. The process of 1-plane balance is as follows:

1. Measure and gain the initial rotation-speed vibration vector (A0) under the normal operation condition.
2. Load the proper trial mass (M) on the rotor and then measure vibration vector (A01) under the condition of the same rotate speed.
3. Calculate the balance mass (Q) which should be load on the rotor according to the following formula:

Q = - M x A0 / (A01 – A0)

During the balancing, all the vibration should be measured under the same rotate speed because of the imbalance force of rotor relates with the rotate speed.

Principle of 2-planes balancing

Almost all the balance of single span rotor can be achieved through the method of 2-planes dynamic balance. As a matter of fact, 1-plane dynamic balance is only one special example of 2-planes dynamic balance.

When doing 2-planes dynamic balance, two planes of adding mass and two points of vibration measure are needed. HG904’s 2-planes dynamic balance also adopts the method of influence coefficient. But the difference from 1-plane dynamic balance is that the vibration of two measurement points should be measured when adding trial-mass to one of the planes. That’s so-called interact effect. 2-planes dynamic balance has four influence coefficients.

The steps to do 2-planes dynamic balance is as followings:

1. Measure initial value of two measurement points.
2. Load trial mass to first plane, then measure the vibration of two measurement points respectively.
   Load trial mass to second plane, and then measure the vibration of two measurement points respectively.
3. Get conclusion of the correction mass.

If the influence coefficient is known, it can be input directly and the above step (2) can be omitted.

APPENDIX

BALANCE GRADE OF RIGID ROTORS

(Abstracted from ISO 1940/1-1986 Requirement of balance grade of rigid rotors—machine vibration)