Piping vibration is a common problem in processing plants due to dynamic loading normally from connected equipment. Measuring and evaluating piping vibration can be challenging because there are no clear standards for vibration limits and once vibration is documented it is difficult to evaluate to determine if the line is at risk. A summary of common methods to document and evaluate piping vibration are provided here and the full paper will be presented at the Vibration Institute Triplex Chapter's Annual Seminar on Tuesday, April 9th 2019.
Ray Kelm is a Sr. Consultant for Kelm Engineering, LLC located in Houston. He has a BSME degree from Texas A&M and a MSME degree from University of Virginia. Ray has spent the last 35+ years working with machinery dynamics and vibration analysis primarily in the petrochemical, power, and refining industries. He has investigated numerous cases where severe piping vibration has existed including a variety of situations where pipes fatigued and resulted in loss of containment.
Vibration Institute Triplex Chapter Annual Seminar
This paper will be presented in full at the Vibration Institute Triplex Chapter's 30th Annual Rotating Equipment, Reliability, and Vibration Analysis Seminar will take place Tuesday, April 9th. The seminar will be held at the MCM Elegante Hotel in Beaumont, Texas. Please visit the Triplex Chapter’s website to register and get more information.
How to Measure and Evaluate Piping Vibration
Piping vibration is a challenging problem to evaluate and can result in pipe fatigue failures when excessive. The biggest problem for the vibration analyst is trying to decide if the vibration amplitudes are acceptable or not!!! There are numerous references and standards that define acceptable vibration limits for rotating or reciprocating machinery, but on limited resources to help the vibration analyst evaluate measured piping vibration.
This paper attempts to describe some basic methods for measuring and evaluating vibration to determine if the amplitudes are acceptable. Analysis methods are also provided for a more detailed analysis when required.
How Much is Too Much?
This is the question that is at the heart of every case where piping vibration is measured. Normally, pipe that is vibrating excessively is connected to either rotating or reciprocating machinery so that the vibration is transmitted from the associated equipment. In some cases, the vibration is more of a forced response due to pressure pulsations in the process fluid. For either case, the vibration response is frequently amplified due to the dynamics of the piping system that is connected to the equipment.
The main challenge with deciding on what the practical limits are for piping vibration is that the limit is actually a stress limit on the pipe wall and not directly a vibration limit. So the challenge becomes finding a way to relate vibration to stress limits for a specific piping system layout.
For example, a system with a very flexible pipe would have very high allowable vibration because the flexibility of the pipe will allow large motion without producing a lot of pipe stress. Alternatively, lower piping vibration for more rigid piping systems can produce higher stresses and result in failure at lower vibration amplitudes.
The most general relationship between piping vibration velocity and stress can be found in ASME OM3 that was originally developed for the nuclear power industry. ASME OM3 describes how to relate piping vibration velocity to allowable stress, or more specifically what the maximum vibration velocity is on a section of pipe to comply with ASME piping code. ASME OM part 3 defines a pipe vibration screening methodology that can be used to assess severity by estimating pipe stress for a given vibration level. ASME OM3 defines a first screening level of 0.5 in/s peak and an allowable vibration equation that incorporates a given pipe layout and construction details.
How to Measure Piping Vibration
The easiest way to screen piping for acceptable vibration is to start at one end of a “run” and document the overall vibration velocity about every foot or so. The purpose of this screen is to identify the maximum vibration velocity on a specific run or section of pipe. Generally, this can be done by using a pipe route on a data collector, where you measure the vibration in two directions perpendicular to the pipe direction along the pipe to identify the maximum in any direction.
Once the maximum vibration and frequency have been identified, it can be compared to screening criteria to assess severity. ASME OM part 3 defines a common first screening criterion as 0.5 in/s peak. If the vibration exceeds this criteria, then a more detailed assessment is required to determine the actual vibration velocity limit.
Pipe Vibration Example
The vibration of this pipe system was documented every 3-5 feet to identify the maximum vibration and frequencies. The maximum vibration was evaluated to identify the locations of high relative movement. The small pipes interconnecting the larger ones are the at-risk lines due to these being where the highest stresses will be located.
Vibration that is steady and periodic is relatively easy to document, since any measurement will have often one or two peaks in FFT’s with obvious cause. Most common causes will be transferred vibration from connected equipment (pumps/compressors/etc.).
In some cases, the vibration is related to flow. When that occurs, it is often necessary to record the data an identify the “maximum” peak vibration over some period of time. An example of this is shown in here which resulted from two phase flow in a line downstream of a control valve.
Kelm Engineering team members have led training courses for the Vibration Institute, presented papers and case studies at multiple conferences, and taught countless clients about the ins and outs of machinery vibration analysis in the normal course of business. During a recent visit to his Alma Mater, Sr. Consultant Dustin Pavelek had a chance to provide Texas A&M University Mechanical Engineering students a look at what life is like as a mechanical engineering consultant.
TAMU MEEN 459/659 Guest Lecture Series
The Texas A&M University Mechanical Engineering department is known worldwide for producing outstanding engineers. Mast-Childs Professor Luis San Andrés, PhD has been a leader in developing these engineers since joining the TAMU faculty in 1991. As the instructor for the senior and graduate level Sound and Vibration Measurement course (MEEN 459/659) during the Spring 2019 semester, Dr. San Andrés has invited multiple industry experts to relay their experiences to students to reinforce the concepts they are learning. Dustin Pavelek had the honor of being invited by his former professor to kick off the guest lecture series that includes presentations by industry luminaries such as John Whalen (TCE-retired), Joe Moreno (LyondellBasell), Ed Wilcox (Chevron), and others.
Adventures in Field Vibration Testing
Pavelek’s lecture, titled “Adventures in Field Vibration Testing”, included several case studies from his 7+ years as a member of the Kelm Engineering team. The lecture started with a review of the contents of a typical field test kit, including vibration sensors, impact hammers, pressure sensors, data acquisition hardware, and PPE. While the focus of the talk was on measurement techniques and machinery troubleshooting in the “real world”, Pavelek made a point to discuss the importance of safety, flexibility, communication, and preparation as key aspects of succeeding as a practicing machinery engineer.
Texas A&M Turbomachinery Laboratory
During the visit, Pavelek also had the opportunity to return to the Texas A&M Turbomachinery Laboratory where he spent four and a half years as an undergraduate student technician and a graduate research assistant for a tour conducted by Dr. San Andrés. The Turbo Lab is the leader in conducting research to promote the reliability and performance of turbomachinery and hosts the annual Turbomachinery and Pump Symposia in Houston. Kelm Engineering has been an exhibitor and contributor to TPS and will be presenting a Tutorial during the 2019 Symposium.
Planning to go to the annual Turbomachinery and Pump Symposia this week? Kelm Engineering will be there ready to answer all of your questions as well as provide information about our techniques, services, and equipment.
From Sept. 17-20 at the George R Brown Convention Center there will be a constant influx of information regarding the latest trends, techniques, and machinery in the industry from some of the industry’s brightest minds and biggest leaders. We look forward to all that will be happening during the conference.
During the four-day conference, Kelm Engineering will be located at Booth Number 1519. Be sure to come see us and discover all that our engineering firm can do your business. Our firm works primarily with industrial companies and corporations. Kelm has worked with some of the world’s largest oil and gas corporations and industrial companies.
Find out about our company and meet the team at our booth. Also, we will have our new coffee mugs available. Come get one. Engineers have to have their coffee. Why not have yours in one of our mugs?
While at the conference, be sure to utilize the LinkedIn hashtag that we will all be using: #TPS2018. Also, be sure to tag us at our LinkedIn account.
Effective vibration analysis is essential to maximizing machinery uptime. However, vibration analysis is a complex subject that requires detailed technical training and years of experience. The right vibration analyst can save you tens of thousands of dollars by detecting machinery faults prior to failure. Having our vibration analysts involved with analyzing your machinery can help identify complex issues. This reduces or even eliminates the need for unscheduled down time or failures, which can be extremely costly.
UNDERSTANDING CERTIFICATION LEVELS FOR VIBRATION ANALYSIS
Certifications in vibration analysis are a great way to understand more about what an analyst can do. Each certification level defines the training received. The levels also define what tasks the analyst is qualified to perform. The categories are ranked I-IV, with category I being the introductory technician level certification, and category IV being the most advanced consultant level. Here at Kelm, all of our engineers are certified at a level III or higher, and qualified to perform most or all tasks associated with vibration analysis. All our certification was attained through the Vibration Institute, the leading organization in Vibration Analysis.
WHAT DOES IT TAKE TO BE A CATAGORY IV VIBRATION ANALYST
Each category, I through IV, defines not only what tasks your vibration analyst is qualified to perform, but also the amount of experience that must be attained before achieving certification. Those with Category IV certification are able to diagnose and solve some of the most complicated problems, and fully qualified in all tasks related to vibration analysis.
Based on the definition provided by the Vibration Institute, “Category IV Vibration Analysts are individuals who understand the theory of mechanical vibrations, advanced vibration analysis techniques, and signal analysis. They shall be qualified to direct condition monitoring programs, perform major diagnostic efforts, and perform and recommend corrective actions and design modifications.”
This certification requires a recommended 60 months of experience in vibration analysis, and 130 hours of training. Training includes receiving certification in categories I-III plus an additional 64 hours of work. At the completion of the training, a vibration analyst certification exam will be administered. This is the final step in receiving certification.
CONTINUING VIBRATION ANALYSIS EDUCATION
Here at Kelm, our team is not only certified to at least category III, but also offers training courses for others to receive certification in categories I-IV. This something we do annually through the Vibration Institute, and our work ranges from teaching basic to advanced courses. Outside of our vibration analyst certification training, we also offer technical training courses on subjects within machinery dynamics around the Greater Houston area. Whether you are in search of a qualified team with category III or higher certification, or are looking to provide continuing education to your own team, give us a call today.
Since 1999, Kelm Engineering has been providing industrial clients with the most effective and innovative field testing and analytical engineering services. Through our services, we ensure our clients are able to maintain and extend the life of their equipment and machinery.