Shaft Alignment.docx

Shaft alignment is the process of aligning two or more shafts with each other to within a tolerated margin. It is an absolute requirement for machinery before the machinery is put in service. When a driver like an electric motor or a turbine is coupled to a pump, generator, or any other piece of equipment, it is essential that the shafts of the two pieces are aligned. Any misalignment between the two increases the stress on the shafts and will almost certainly result in excessive wear and premature breakdown of the equipment. This can be very costly. When the equipment is down, production might be down. Also bearings or mechanical seals may be damaged and need to be replaced. Flexible couplings are designed to allow a driver (electric motor, engine, turbine, hydraulic motor) to be connected to the driven equipment. Flexible couplings use an elastomeric insert to allow a slight degree of misalignment. Flexible couplings can also use shim packs. These couplings are called disc couplings. Tools used to achieve alignment may be mechanical or optical, like the Laser shaft alignment method, or they are gyroscope based. The gyroscope based systems can be operated very time efficient and can also be even used if the shafts have a large distance (e.g. on marine vessels). Before such a shaft alignment can be done, it is also essential that the foundations for the driver and the driven piece are designed and installed correctly. If that is the case, then shaft alignment can be started. The resulting fault if alignment is not achieved within the demanded specifications is shaft misalignment, which may be parallel, angular, or both. Misalignment can cause increased vibration and loads on the machine parts for which they have not been designed (i.e. improper operation). A major part of keeping equipment running smoothly involves regular maintenance and upkeep and ensuring that the machinery is kept lubricated and properly aligned. When shafts or belts on rotating equipment are misaligned, the risk of costly, unplanned machine downtime rises dramatically. Misalignment also damages seals and couplings. Lubrication problems often can be traced to seals that have been compromised by shaft or belt misalignment. Simply replacing a seal will not stop future seal failure and associated loss of lubricant — only correcting the misalignment will solve the problem. Failure to align the shafts or belts properly will increase the amount of stress on the units, resulting in a range of potential problems that ultimately can seriously impact a company’s bottom line:      

Increased friction, resulting in excessive wear, excessive energy consumption, and the possibility of premature breakdown of equipment Excessive wear on bearings and seals, leading to premature failure Premature shaft and coupling failure Excessive seal lubricant leakage Failure of coupling and foundation bolts Increased vibration and noise

Onsite Balancing and Analysis Fan balancing and fan vibration analysis are essential to improving efficiency & extending the life of your industrial fan. ProcessBarron has a fan balancing and vibration analysis field service team dedicated to field fan balancing, solving field fan vibration problems, fan start up and technical field installation services.

Our service engineers are heavily experienced in analyzing fan bearing issues and fan catastrophic failures.

Fan Balancing Fan balancing can minimize a host of problems. All wheels manufactured or repaired by ProcessBarron are balanced in accordance with A.N.S.I. S 2.19 using a quality grade of G6.3 (G2.5 or G1 grade upon request), and the IRD Mechanalysis 290T Balancing Instrument Operating Manual. In-shop fan balancing is conducted at operating speeds of approximately 240-300 RPM, with the IRD computer analyzer compensating for the actual operating speed of the industrial fan. Our service team will balance your fan wheel to the correct manufacturer’s tolerance specification, and provide a Certified Wheel Balance Report.

Rotor balancing under operating conditions Unbalance is the most common cause of damage in rotating machines. It can be found in fans, ventilators, belt pulleys and couplings. The enormous centrifugal forces resulting from the uneven mass distribution generates high vibrations during rotation, which affects the entire machine construction. This can cause bearings, seals and couplings to wear prematurely or even fail. An unbalance is easy to detect in the vibration spectrum because it vibrates in sync with the shaft rotational speed. Its energy is concentrated at the first harmonic spectral line. This can be remedied by balancing the installed rotor with a portable balancer, a process known as field balancing. Balancers from PRUFTECHNIK are optimized for detecting and eliminating unbalance in just a few steps. Besides standard applications, such as industrial fans of all sizes and shapes, the balancing devices are also ideal for special requirements, such as field balancing of rotor blades on wind turbines.

One common definition of balance is when the mass centerline and the rotational centerline of a rotating part are equal. Another definition is when zero vibratory force or vibratory motion is imparted from the rotating part to the bearings. Field balancing is a technique used to balance a rotating part in place without removing the part from the machine. The advantages of field balancing are apparent, in that time can be saved by not removing the rotating part from the machine and sending it to a

shop for balancing. An additional benefit is realized in ensuring that the rotating part is balanced as installed. When field balancing, one must have access to the rotating shaft and have an area to place trial weights and correction weights. As seen in Figure 1, the access requirements for field balancing eliminate many machines as field balancing candidates.