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Randy Passman is a Sr. Machinery and Vibration Advisor for Becht Engineering and Stanley Fussell is a Sr. Machinery Advisor.

Resolution of Chronic Cooling Tower Fan Vibrations

Resolution of Chronic Cooling Tower Fan Vibrations
Traditional rotating equipment mounted at grade use the mass of a foundation and grout to reduce vibration and provide support and stiffness. However, cooling tower fans must be elevated many feet above a basin of water which sometimes puts them “out of sight and out of mind”. Cost and practicality prohibits concrete and grout, thus most cooling towers are constructed by bolted wood and / or fiberglass elements with a fabricated steel sub base supporting motor, gearbox, and blades. As a result, cooling tower foundations are much less stiff than traditional rotating equipment. This is usually not an issue because the low speed of the fan (usually 60 rpm to 140 rpm) does not usually produce large forces. Motors and gearboxes used are generally made to the same precision levels as other general purpose machinery regarding balance, runout and dimensional tolerances, so the imbalance and forcing functions are usually low.  As...
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Process Centrifugal Compressor Oil Seals

Process Centrifugal Compressor Oil Seals
Ingersoll Rand Cone Oil Seals Compressor process shaft end seals are designed to seal the rotating assembly in the stationary compressor case to prevent the process gas in the compressor from escaping to the atmosphere and to prevent the atmosphere from getting into the process gas.   Shaft end oil seals, as compared to the relatively new dry gas seals, have been in the machinery world since the inception of centrifugal compressors.  A comparison of advantages and disadvantages for each type of compressor shaft end seal (gas or oil) will not be covered in this article.  It is safe to say that today’s trend is to purchase new centrifugal compressors with dry gas seals, and where feasible, to retrofit existing oil seals with dry gas seals. Purpose The purpose of this article is to outline the basic components of a compressor oil seal and support system, with a brief description on how...
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Reciprocating Compressor Cylinder Alignment (Often overlooked as a failure root-cause)

Reciprocating Compressor Cylinder Alignment (Often overlooked as a failure root-cause)
Compressor cylinder bore misalignment can cause failures that are often not attributed to misalignment. Crosshead shoes uneven wear, compressor piston rod failure at both the crosshead and at the piston, compressor piston rod coating failure, piston wear and compressor cylinder bore wear can all be attributed to cylinder misalignment. The objective of this article is to highlight the importance of cylinder alignment and expose the problems associated with cylinder alignment so the next time you experience one of these types of failures, checking the cylinder alignment is included in your failure investigation. Assumptions often lead to bad results. In the case of reciprocating compressors, I have found that there are two assumptions about the cylinder bore to crosshead bore alignment that have caused unexpected problems. The first assumption is “if the compressor rod runout is in tolerance then the cylinder bore alignment is in tolerance”. The second is “the male and...
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stanley fussell

How can I help you.

Johanna, this is Stanley Fussell the Author of this article. I would be happy to help you anyway I can. Please contact me on my em... Read More
Wednesday, 28 February 2018 16:41
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No Detail or Procedure is Trivial, or, Sophisticated Vibration Analysis is a VERY Cost Effective Diagnostic Tool

No Detail or Procedure is Trivial, or, Sophisticated Vibration Analysis is a VERY Cost Effective Diagnostic Tool
Today it is common practice in overhauls of large rotating equipment to spend many man hours in detailed planning, coordination, writing procedures, reviewing documentation, reviewing past photos, procuring and inspecting spare parts etc. We also review our past experience and put steps in place to mitigate past problems or errors.   Now that we have a detailed plan, have purchased and inspected all necessary spare parts and have mitigated all potential known problems we simply give the plan to the machinery contractor to execute, right? If you have been responsible for large machinery repairs long enough, you have definitely learned to say one thing: “I have not seen everything,” and never to say another “Oh that could never happen here.” No matter how thorough we think our plan is, going in, missing even the slightest detail in the field can result in a failed start up or worse. Experienced oversight is essential...
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