The commonly used simple status monitoring methods mainly include auscultation, touch, and observation.
When the equipment is operating normally, the accompanying sounds always have a certain melody and rhythm. As long as one is familiar with and masters these normal melodies and rhythms, abnormal noises that are heavy, mixed, strange, or chaotic can be compared through human hearing to determine whether there are hidden dangers such as looseness, impact, or imbalance inside the equipment. Tapping parts with a hammer can help detect any cracking noises, which indicates the presence of cracks.
An electronic stethoscope is a type of vibration acceleration sensor. It converts the vibration status of the equipment into electrical signals and amplifies them, allowing workers to listen to the vibration sounds of the operating equipment through headphones for qualitative measurement of the sounds. By measuring the signals at the same measuring point, at different times, under the same rotational speed and working conditions, one can determine whether the equipment has faults. When the headphones emit a crisp and sharp noise, it indicates a high vibration frequency, usually caused by local defects or small cracks in relatively small and high-strength parts. When the headphones emit a murky and low noise, it indicates a low vibration frequency, generally caused by larger and lower-strength parts with larger cracks or defects. If the noise from the headphones is louder than usual, it indicates that the fault is developing; the louder the sound, the more serious the fault. If the noise from the headphones appears intermittently and chaotically, it indicates that there are loose parts or components.
The sense of touch can monitor the temperature, vibration, and gap changes of equipment. The nerve fibers in human hands are sensitive to temperature and can accurately distinguish temperatures within 80°C. When the machine part’s temperature is around 0°C, it feels cold, and prolonged contact can cause a piercing pain. At around 10°C, it feels cool but generally bearable. At around 20°C, it feels slightly cool, and as contact time increases, it warms up. At around 30°C, it feels slightly warm and comfortable. At around 40°C, it feels hot with a slight burning sensation. At around 50°C, it feels very hot, and prolonged pressure can cause sweating. At around 60°C, it feels very hot but can generally be tolerated for about 10 seconds. At around 70°C, it feels burning and painful, generally only tolerable for about 3 seconds, and the touched area will quickly turn red. When touching, one should first test lightly before applying more pressure to estimate the temperature rise of the machine parts.
Shaking the machine parts can detect gaps of 0.1mm to 0.3mm. Touching the machine parts can feel variations in vibration strength and whether impacts occur, as well as the crawling situation of sliding boards.
Using a thermometer equipped with a surface thermocouple probe to measure the surface temperature of rolling bearings, sliding bearings, spindle boxes, motors, etc., can quickly and accurately identify thermal anomalies and is convenient for the touch measurement process.
The human eye can observe whether there are looseness, cracks, and other damages on the machine parts of the equipment; it can check whether lubrication is normal, whether there is dry friction, and whether there are signs of running, leaking, or dripping; it can check the amount, size, and characteristics of metal wear particles in the sediment of the oil tank to assess the wear condition of related parts; it can monitor whether the equipment operates normally and whether there are abnormal phenomena; it can view various instruments installed on the equipment that reflect the working status of the equipment to understand changes in data; it can use measuring tools and directly observe surface conditions to detect product quality and assess the working condition of the equipment. By comprehensively analyzing various information from observations, one can determine whether the equipment has faults, the location of the faults, the severity of the faults, and the causes of the faults.
Through instruments, a simple method for monitoring wear status is the magnetic plug method, which observes wear particles collected from the equipment’s lubricating oil. Its principle is to insert a magnetic plug into the lubricating oil to collect iron wear particles generated from wear, and then using a reading microscope or directly observing with the naked eye to assess the size, quantity, and shape characteristics of the wear particles to determine the wear level of the mechanical parts’ surface. The magnetic plug method can observe larger wear particles appearing in the later stages of mechanical parts’ wear. During observation, if small wear particles with fewer quantities are found, it indicates that the equipment operates normally; if larger wear particles are found, attention should be paid to the equipment’s operating state; if large particles are repeatedly found multiple times, it is a precursor to an impending fault, and immediate shutdown and inspection should be conducted to identify and eliminate the fault.
