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Articles: Alignment and Balancing

Balancing of an FD Fan at a Refinery

Presented by Troy Feese

There are several commercially available software packages, such as SMS Star and ME’Scope, that can be used to perform operating deflection shape (ODS) measurements.

This article provides a case history of a forced draft (FD) fan that experienced high vibration due to unbalance and an impeller resonance near the operating speed. The common balancing method of influence coefficients was unsuccessful due to varying phase data. However, vibration was reduced to an acceptable level using the four-run method without phase data.

Balancing Out the Root Cause

As anyone who has practiced vibration analysis knows, vibration signatures obtained on routes are often far from the wall chart examples. The reason for this is that the vibration signatures collected and analyzed represent the response of a system due to a variety of different forces that act simultaneously to produce one signature. Unfortunately, vibration analysts are actually interested in determining the individual forces that cause the response. Once the forces are accurately identified, only then can they be reduced or eliminated.

By Chad Wilcox

Balancing Weights: Radius Changes & Splitting

By Dennis Shreve

Oftentimes in real-world balancing applications, you will come across a way to get a quick measurement and make and verify an unbalance correction via a temporary solution with clamp-on weights or some type of balancing compound (like modeling clay or bee's wax).

Do You Do the Verti-Zontal?

By David Zdrojewski

The use of lasers in measuring misalignment has improved the shaft alignment process. Literally thousands and thousands of laser-based measuring tools have been sold over the past 20-some years. No doubt, laser systems have eliminated many errors and simplified the process used to measure misalignment. However, after all these years, we haven’t dramatically changed or improved the basic process used to correct misalignment. The way we have been correcting misalignment is inefficient, time consuming, and frustrating to those who have to move machines to make proper alignments.

Dynamic Movement White Paper

By VibrAlign, Inc.

This paper addresses a vexing problem that has plagued machine reliability professionals for decades. Despite the best efforts to precisely align rotating machinery shafts, dynamic movement (mostly manifested by the thermal growth of the machine casings) has resulted in machines operating at less than optimum alignment conditions.

Field Balancing Standards - How Good Is Good Enough?

By Victor Wowk, P.E.

Historically, 1.0-mil peak-to-peak displacement has been quoted by many field balancers as the desired goal. This is a good number to strive for, but may be overbalancing in some cases. The 1.0 mil came from balancing rebuilt motors on a soft-bearing balancing machine with velocity transducers integrated to displacement. The 1.0 was an easy number to remember and the vibration was barely perceptible. The shop balancer then applied this same 1.0 mil when taking his instruments out to a field balance job.

Machine Train Alignment

by Damian Josefsberg

Machine train alignment doesn't have to be a complicated, mind boggling task. There is a basic step by step procedure to follow which will allow you to maximize all of the benefits of aligning a machine train. When you follow this procedure and adhere to its principles, you will find that machine train alignment can often be easier to accomplish than a one coupling "vanilla" alignment.

Q&A on Angular Soft Foot

With Jason SteedWhat is Angular Soft Foot?

Angular Soft Foot is a condition that occurs when a gap under a motor's foot is "non-parallel" to the mounting base. Because of this gap, the foot, when tightened, is forced to seat itself to whatever angle allows it to make total surface contact. As a result of this seating, stresses are created in the motor's foot that transfer through the motor "leg" and into the housing.

Rim & Face Alignment Method

You can use the Rim & Face Method to perform a calculated precision alignment process. You may use a variety of shaft alignment fixtures. We recommend that you use a commercial package designed to accommodate a variety of shaft diameters. The fixtures should include an assortment of rods to span various coupling lengths. These packages expedite the precision alignment process. Also, sag values can be pre-determined for the standard rod
assortment.

Rolling-Element Bearing Analysis (REBA) Techniques and Practices

By Dennis H. Shreve, Commtest Inc.

When it comes to diagnosing common machinery problems with the tools offered with vibration measurements and monitoring, there are typically 5 major areas requiring correction: (1) unbalance, (2) misalignment, (3) looseness, (4) resonance, and (5) rolling-element bearing faults. This paper will examine modern-day techniques for early detection of faults in rolling-element bearings.

Shaft Alignment, Soft Foot & Energy Savings

By Alan Luedeking

"Does misalignment waste energy?" is a question often asked. The answer, emphatically, is yes! General Motors Corporation and Ludeca Inc. performed and published a study on this issue in 1993 which showed conclusively that energy savings (Real Power savings) of 2.3 percent could be obtained on loaded machines. On unloaded machines, the savings ranged as high as 9 percent! At ICI Chemicals, a UK chemical plant in the north of England, a carefully controlled doctoral research project revealed even higher savings. Other studies suggest averaged savings of 4 to 5 percent.

Sheave Alignment and Maintenance

Alan Luedeking of Ludeca Inc.

Good sheave alignment will increase efficiency by reducing premature wear or failure of belts, pulleys and bearings. This can be accomplished by several different alignment methods, such as the labor-intensive string and straightedge method (most common), or by laser. The latter, in the form of the DotLine Laser^TM Pulley Alignment Tool, is new to the sheave alignment field, but has proven itself in greatly reducing downtime and the manpower needed to do the alignment, while simultaneously achieving far greater accuracy. This results in great labor savings and increased production uptime.

Stress: The Silent Killer - Part 1 of a 2 part series

By John Lambert

To properly install machinery, you must look at the whole process. Each component is necessary. Each technology has its place. Detecting faults plays a critical role in maintenance, but first you must install…and you must install properly.

The Expected and the Unexpected

The Ever Increasing Benefits of Modern PdM Technologies

by Bill Hillman, CMRP

When dial indicators, straight edges, and taper gauges were the only tools available for doing shaft-to-shaft alignment, machines were often left in a rough alignment condition.  This happened because either too much time would need to be invested in order to obtain the required degree of precision or human error entered into the calculations. 

The Impact on Bearing Life of Overtensioned Belts

by Jeremy Davis and Hunter Golden

One of the leading causes of premature bearing failure can be attributed to overload and overstress conditions.  A common catalyst for this type of condition is improper belt tensioning.  Increasing the radial load on a bearing will drastically reduce the expected bearing life span and can be graphically illustrated as y=1/x (0<x<infinity).  In order to achieve optimal design expectations, procedure based, precision maintenance practices must be utilized.

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