In a word, vibration. In addition to fatigue, vibration is also a major drawback. This is because cyclic fatigue loads cause parts and equipment to bend until they rupture. Here are some important innovations in vibration theory, along with examples of introducing vibration and pump damage. Sir Riley explained vibrations in his “Theory of Sound”, published in the late 19th century, but resonance was only fully explained recently. To do this, the authors solved Newton’s equations of differential motion and created a new theory in the Vessels & Tubes 2017 conference paper (Shock Waves, Vibrations, Echoes of Linear Elastic Beams). Basically, any structure or machine and all its parts oscillate at multiple frequencies, also known as higher natural frequencies. You can now graphically display these frequencies. Especially when the motor speed of the device is close to the normal frequency, the vibration at this frequency will increase and damage the device.
Vibration is a mechanical phenomenon in which vibrations occur around the equilibrium point. The word comes from the word vibrashanum (“vibration, wave”). Vibrations can be periodic, such as the movement of a pendulum, or random, such as the movement of a tire on a dirt road. Vibration may be desirable. For example, vibrating forks, straws, harmonicas, mobile phones, speaker cones, etc.
Consider bearing failure on a 150hp motor driving the included pump. Engine noise was reported more frequently than usual and was audible up to 15 meters from the engine. The engine ball consists of an inner and outer ring on which the ball rotates, and a cage that separates the ball. Each ball, cage, and match have a specific frequency, and the frequency range reflects the number of times the ball has spun since the injury. The resistance, one of the bearings, was completely destroyed, and the bearing and several baskets were destroyed. The bearing no longer vibrates at the rotational frequency of the ball and the bearing is not broken. The vibrations exceeded 0.1 inches per second and the bearings were also damaged. In the case of thrust bearings, the breaking bearings vibrated at a speed of fewer than 0.1 inches per second. There was no longer any vibration associated with the thrust bearings not touching the shaft. This means that the bearings underwent vibration failure because the measured vibrations were not caused by bearing assembly failure, but due to bearing assembly failure. What about the noise level? Bearing vibration occurred at the frequency of the mesh-mounted on the steel platform and was not sufficient to produce low-frequency audible noise. In other words, the vibration of the altitude shook the scene so much that it could be felt 50 feet away. This resonance problem, as with many complex vibration failures, was not clear when it came to troubleshooting. The invention of the new principles described here provides engineers with new tools to better understand vibration disturbance.
The service provider verifies that the operating system/installed pump operating frequency is abnormal within ±20% of the pump operating frequency/frequency. Operating frequency is defined by, but is not limited to, shaft speed, blade shaft, gear network, power, etc. This system is defined as, but not limited to, motors, pumps, bearings, clutches, motors, pumps, and bearings. , composite cable ties, pedestals, pedestals and stairs/platforms, fittings, and power lines. The supplier will provide to the Buyer or a third party designated by Buyer the design, manufacturing, modeling data, calculations, and analysis for the specific storage location purchased for review. After installation, the natural frequency is determined and measured by an independent contractor using an acceptable modular analytical test. Once the normal rate is determined to be approximately 20% of the operating rate, the supplier will immediately initiate a root cause analysis.
As part of the new installation, two new pumps rated at 2,682 horsepower, 448 rpm, and 92,600 gallons per minute (GPM) were installed vertically (see Figure 1). One pump ran smoothly and the other had 45 miles of point-to-point oscillation at 1x operating speed. Experience has shown that the normal speed of a regular pump is 17% faster than the operating speed, and the 28ml pump is 8% faster (see Figure 1). Both natural frequencies have a lot of gains. The 28 ms oscillation exceeded the tolerance limit and required a normal frequency parameter at the node. In this case, the problem was finally resolved by the EPC and the frequency operator making a significant change to the contract language.
A new 5,500 hp, 3,581 rpm pump motor was purchased to replace a larger frame 1960s vintage motor. Due to the more efficient smaller frame of the new motor, an adapter was fabricated to mount the new motor to the old base. The motor vibration was high due to resonance (see Image 2). There was no natural frequency requirement written into the purchase agreement, but after significant time, testing and educating the provider, a new adapter was provided under warranty. Resonance-specific contract language and design oversight could have avoided the problem.
A good contract/PO language, engineering, modeling, monitoring, and commissioning are good guarantees of reducing the risk of resonance problems. If you lack in-house expertise, consider hiring an external inspection consultant for each project. You need to work on planning and forecasting that will be useful in the future.