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The Basic Principle Of Diesel Generator Maintenance Method

Nov. 30, 2021

The basic principles and characteristics of the ultrasonic and radiographic methods for physical testing of diesel generators are as follows:

 

The ultrasonic method for physical inspection of diesel generators uses the phenomenon of refraction and reflection caused by ultrasonic at the interface of two different media to detect hidden defects in parts. This method can be divided into the following categories.

 

1. Pulse reflection method. The voltage from the pulse oscillator is applied to the probe wafer, and ultrasonic waves are generated after vibration, which passes through the workpiece at a certain speed. When the workpiece is defective and the bottom is reflected, the probe receives it and displays it on the fluorescent screen of the oscilloscope. The abscissa of the screen represents the distance, and the ordinate represents the sound pressure intensity of the reflected wave.

 

2. The above shows the penetration method. Penetration method is also called sound and shadow method. It can be seen that the high-frequency oscillator is connected to the transmitting probe A, and the ultrasound transmitted by the probe A is transmitted internally on the working side. When the workpiece is completely defect-free, the ultrasonic wave can be obtained from the workpiece smoothly through the probe B, and it will be displayed on the oscilloscope after being enlarged. If there is a defect on the way, part of the sound waves will be blocked and "sound shadow" will be formed in the future. At this time, the received ultrasonic energy will be greatly reduced, and the indicator will show the defect accordingly.

 

3. Resonance method. The ultrasonic wave is injected into two parallel workpieces with adjustable frequency, so that the ultrasonic reflected from the bottom surface and the incident wave are in contact with each other in the opposite direction on a straight line. When the wall thickness of the workpiece is equal to half of the ultrasound or an integer multiple of the half wavelength, add them together, that is, the incident wave and the reflected wave resonate within this time. Through the measurement of the resonance frequency, the thickness of the workpiece can be judged or the existing defects can be detected. When the workpiece is completely defect-free, it corresponds to the thickness of the entire workpiece. If there is a defect parallel to the surface of the workpiece, the corresponding defect depth produces resonance, and the resonance frequency is different. For irregular-shaped defects, since two inverse waves cannot be generated, no resonance can be generated by changing the ultrasonic frequency, so that the existence of the defect can be judged.

 

The above three methods are suitable for different occasions. It has high sensitivity, can detect small defects, can accurately know the location and size of the defect, but it is not suitable to detect too thin workpieces or defects close to the surface. This method is simple and easy to use, and is currently the most commonly used ultrasonic inspection method. The perforation method requires parallel on both sides of the workpiece, low sensitivity, and high requirements for the relative position of the two probes. It is often used for the detection of plate interlayers and non-metallic materials such as rubber and plastics. The resonance method can accurately measure the thickness of the workpiece, and is especially suitable for detecting internal defects such as thin-walled parts, pipe fittings, container walls, metal bonding structures, etc., and requires high surface roughness.

 

In short, ultrasonic testing mainly involves the organization structure, ultrasonic frequency, probe structure, contact state, surface quality and geometry of the workpiece, sensitivity adjustment, etc. of the component material to be tested. The system can detect defects in the deep part of the workpiece, many different types of defects, without material restrictions, the equipment is light and handy, it can be detected on-site, the cost is low, and it is easy to realize the automation of the detection. However, it is difficult to detect workpieces with complex shapes.

 

diesel generator


4. Ray method. There are many types of light, among which there are three main types that can easily penetrate objects: X-rays, gamma rays and neutron rays. The difference between light and gamma rays is only in the way they are generated. They are both electromagnetic waves with very short wavelengths, and they are essentially the same. The particles that make up the nucleus are neutrons and protons. When it undergoes a nuclear reaction, the neutrons fly out of the nucleus and produce neutron rays.

 

Since the three rays will be absorbed and scattered when they penetrate the object, their intensity will decrease after passing through the object, and the attenuation degree depends on the thickness of the object, the type of material, and the type of ray. The board of the same thickness contains pores, this part does not absorb light, and it is easy to pass through. Conversely, if foreign objects that easily absorb light are mixed in, it will be difficult for light to pass through these places. Therefore, the intensity of the light is used to determine whether the object is defective.

 

(1) The difference in the intensity of X-ray irradiated objects is reflected by the radiometer. X-rays are divided into: X-ray imaging film method, X-ray fluorescent screen observation method, X-ray fluorescent screen observation method, and X-ray fluorescent screen observation method. The basic principles are the same as those of general industrial closed-circuit television systems. At present, X-ray photography is the most widely used in production.

 

(2) The nature and basic properties of gamma rays produced by gamma-ray radioisotopes are the same as X-rays, so the detection principle is the same, and the source of the reflected rays is different. Compared with X-ray photography, ordinary radiography has many outstanding advantages, such as: strong penetrating ability, light equipment, high transmittance, detecting multiple workpieces at a time, can work for a long time without interruption, suitable for field use.

 

(3) Neutron rays are different from the above two types, and are mainly used for photographic inspection. This technology is often used in the trial production of materials such as hydrogen-containing lithium, borides, heavy metals, ceramics, rocket fuel, projectiles, and reactors.

 

In addition, methods such as vortex inspection, laser holographic inspection, acoustic resistance inspection, infrared nondestructive inspection, and acoustic emission detection are limited to space, so I won't repeat them here.

 

Jiangsu Starlight Electricity Equipments Co.,Ltd. is a manufacturer of professional generators, diesel generator sets, non-moving generator sets, Cummins generator sets, Volvo generator sets, etc. It has 64 sales and service departments across the country, providing users with design, supply, debugging, and maintenance at any time. Welcome customers to come to consult and visit. Looking forward to your inquiry, please send email to us for details sales@dieselgeneratortech.com


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