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Becht Engineering Blog

In this section of the site contributing authors submit interesting articles relating to the various services, industries and research & development efforts of Becht Engineering.

Equipment Nozzle Loads

Equipment Nozzle Loads
by Greg Hollinger and George AntakiOne of the qualification requirements for a piping system is to keep the loads imparted by the piping on equipment nozzles within certain allowable limits. These loads consist of sets of three forces and three moments, for the various load combinations. There are basically two types of nozzle load limits: (1) nozzle loads applied to active equipment, and (2) nozzle loads applied to passive equipment.Active Equipment Nozzle LoadsActive mechanical equipment consist of equipment with moving parts, such as pumps, compressors, and fans. The pipe nozzle load limits are developed by the equipment manufacturer and are intended to prevent malfunction, such as shaft misalignment, or distortion of the casing that could impede the movement of impellers. These limits are typically based on actual testing of the equipment, and not on analysis.Some standards have published standard pump nozzle loads, but these are only valid for the particular pumps for...
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Process Centrifugal Compressor Oil Seals

Process Centrifugal Compressor Oil Seals
Ingersoll Rand Cone Oil SealsCompressor 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.PurposeThe purpose of this article is to outline the basic components of a compressor oil seal and support system, with a brief description on how they function, and a...
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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 female...
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Recent Comments
stanley fussell

Reciprocating Compressor Cylin...

Jimmy thanks for your question. The flywheel should have been balanced by the OEM at the time of manufacturing. The flywheel shoul... Read More
Monday, 18 November 2019 16:35
Guest — Jimmy

Tolerance

Hi Randy & Stanley, Is there any rule of thumb on tolerance of cylinder alignment depends on size of the compressor (cylinder lin... Read More
Monday, 21 October 2019 06:58
stanley fussell

Reciprocating Compressor Cylin...

Jimmy, there are some rules of thumb for this tolerance, I have found it best to use the tolerances established by the Original Eq... Read More
Friday, 25 October 2019 17:58
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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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