April 14, 2015
I recently spoke to a reliability engineer who was rolling out our alignment and vibration equipment to 15 plants across the U.S. This customer got us involved early on in the process. They didn’t just set aside budget money for the equipment purchase, but also enough to properly train their field service personnel on the proper use of the new technologies. We didn’t just address the use of the alignment tools, but also issues like proper equipment installation, lubrication, etc.
One of the topics of discussion was alignment tolerances. Since this customer has high speed ammonia compressors, they wanted to ensure their equipment was properly aligned and therefore adopted our alignment tolerances as their corporate standard. Since these tolerances are built into the alignment tool, it was not only easy for the user to determine if the equipment met their established corporate alignment standards, but also for management to review the work to ensure it was correctly completed. This oversight is easily accomplished via software we provide that allows complete storage of all alignment results on your network and allows easy report generation of the field results for review.
I was told that their vibration analysis program still identified equipment that was out of their alignment tolerances. How could this happen? It turned out that contractors were performing work without being held to the standards as plant personnel, including alignment tolerances or requiring the use of specific equipment to perform the work. In addition, the contractor was not required to provide a copy of the results for review and digital storage.
How could this happen? Unfortunately, it is not so uncommon. Many facilities or corporations do not require that maintenance activities be performed to standards or use equipment they can trust for the results. Additionally, they do not clearly write job plans that are issued to internal maintenance employees or contractors specifying how the acceptable results are to be achieved (what steps are required, what tools are required, what documentation of results is required, etc.) In addition, the Maintenance Scheduler does not review the results of the completed work to confirm that it was satisfactorily completed within acceptable specifications. Oversight failures as well as failure to include these items in your job plans and work orders can easily result in continued maintenance issues and repeated or wasted efforts to keep your equipment running.
April 7, 2015
Recently, while assisting a customer in setting up a vibration database, the subject of creating the best trending template for a boiler feed water gearbox came up. This particular application requires trending templates to monitor a complex machine train consisting of four separate machines. For the purpose of this discussion we’ll concentrate only on the gearbox in the machine train. The gearbox is a speed increaser. It is a little unusual in that a hydraulic torque converter allows the speed of the main boiler feed water pump to be varied. This gearbox is designed with three individual shafts (an input shaft, intermediate shaft and output shaft), all enclosed within a single gearbox housing.
The speed of the input shaft is constant at 29.93 Hz (1796 rpm) and attached to this input shaft is a pinion gear with 88 teeth. The pinion gear runs in mesh with another gear mounted on the intermediate shaft with 27 teeth. This results in a gear mesh frequency of 2,633.84 Hz. We must determine the required frequency range (Fmax) by multiplying our calculated gear mesh frequency by 3.25 resulting in an Fmax of 8559.98 Hz. In the software we can’t select 8559 Hz so we’ll need to select the next higher value, 10kHz.
The next step in the process is to determine the speed of the intermediate shaft by using the following formula:
Intermediate shaft speed = 29.93 Hz × 88 teeth = 2,633.84 Hz / 27 teeth = 97.54 Hz or 5,852.4 rpm.
We must now determine the required lines of resolution (LOR) since we have two fairly closely spaced running speeds. We have the intermediate shaft speed, running at a constant speed of 97.54 Hz and the output shaft speed which is variable.
When the boiler feed water pump is operated at 100% the output shaft running speed of the gearbox is 94.33 Hz or 5660 rpm. There are only 3.21 Hz or 192.6 cpm between the two shaft speeds within the gearbox. Therefore, our lines of resolution setting will need to be high enough to provide separation while performing analysis. With an Fmax setting of 10kHz we will need a minimum of 3200 lines of resolution to distinguish between the two shaft speeds. 10kHz Fmax / 3200 LOR = 3.125 Hz bin width, but to be on the safe side I would recommend selecting the next higher resolution setting (6400 LOR). This will provide a 1.56 Hz (96.3 cpm) resolution to easily see the two different shaft running speeds for accurate analysis.
Below is an example of improper resolution for accurate analysis:
Improper resolution settings resulting in a flat top 1× for the output shaft speed. Proper resolution settings:
Correct resolution settings allowing clear distinction of the output shaft speed.
The lesson here is that proper vibration analysis requires understanding the machine design. Additionally, it is critical that the proper maximum frequency (Fmax) and lines of resolution (LOR) be determined. Improper Fmax settings will result in data being missed. Inadequate lines of resolution (LOR) can cause closely spaced peaks to merge together making it impossible to distinguish between them. These errors will result in poor vibration analysis results. Pay close attention to the details when setting up the equipment in your vibration database.
March 31, 2015
Purchasing a condition monitoring tool is one step in your journey to implementing a reliability program. Proper training on how to use the new technology, planning the work correctly, ensuring the work is completed on schedule and done so correctly is critical to success. Just as important is understanding the risks associated with your equipment, especially when it fails. A criticality assessment along with failure modes and effects analysis will help you understand those risks and determine where to focus your maintenance activities.
I recently spoke to a plant engineer that had purchased alignment and vibration equipment from LUDECA. He had performed several alignments and collected baseline vibration data. The decision was made to start aligning machines that required maintenance and this was a wise choice to ensure failure modes were not inserted into equipment during routine maintenance activities. Unfortunately, this facility had not performed a criticality assessment on their machinery! It turns out that the plant had a catastrophic failure on a piece of equipment that was vital to the overall production processes of the plant. The first comment made was “why did we have this failure when we recently invested in alignment and vibration equipment?”
You must fully understand the risks to safety, production, environment, and profits that your equipment imposes on your facility. As you can see from the example above, not understanding these factors may lead to continued equipment failures and their undesired consequences. To ensure that you do not continue to experience maintenance failures requires that you fully comprehend the risks that each piece of equipment entails. Had this facility understood the failure modes and the (criticality/risk) impact each machine posed, they would have been able to focus their maintenance efforts where they were most needed to keep the plant efficiently operational.
As part of this endeavor, it is important to apply condition monitoring (vibration analysis and properly targeted alignment, among other things) on the equipment within your plant, because it is extremely difficult to be reliable without doing so. However, you must understand how and where to direct those efforts to ensure that unwanted risks are reduced. Understanding how your equipment can fail (FMEA), the consequences of those failures (RCM or risk assessment), what equipment is most important to keep your plant operational (criticality assessment) are all important to ensure that your maintenance efforts are properly focused. These efforts may avoid the experience this facility had and prevent your plant from experiencing the same unwanted effects.
March 24, 2015
You should regularly back up any active database to guard against data loss and to protect the investment made in your database design. A backup allows you to easily restore an entire database without the hassle of rebuilding everything from scratch. Backups help protect a database from system failures and help protect against mistakes. As the size of your database grows, you should consider archiving the older data. Archiving is the process by which you periodically move older records from one database to an archive database. If you want to automate creating backups of database files, consider using a product that performs automated backups of a file system, such as file server backup software or a USB external backup device. To decide how often to make backups, consider how often your database changes: • If your database is an archive, or if it is used only for reference and rarely changes, you should make a backup every time that your data changes. • If your database is active and your data frequently changes, you should back up your database on a schedule. The more active the database or greater the number of changes, the more often you should schedule the backups. The easiest way to back up an OMNITREND database is to use the copy and paste function within Windows Explorer. Locate your Access database within Windows Explorer and left click on the file to highlight it; next right click on the file and select copy. While in Windows Explorer navigate to the location that you would like to copy the database and right click on the location and select paste. You have now created a backup of your database. If you are uncertain as to where the database file is located; open OMNITREND and the top bar will inform you of the location and name of your database. It is recommended that the backup database be stored on a different computer as the original. If that computer crashes it will result in the loss of both the original and the backup database. A few suggestions as to where to store a backup database would be a CDROM/DVD, USB stick, network drive, the cloud, or another computer.
March 17, 2015
Now, more than ever flatness checks for main bearing bore alignment in reciprocating compressors are critical to bearing and crankshaft life. Ariel Compressors have a strict tolerance for the top rail alignment and the ER-82 document provided by Ariel discusses this in detail. There are many ways to perform a flatness check so long as the equipment meets the Ariel guideline for accuracy. Many people have chosen the INCLINEO but the LEVALIGN EXPERT adds a new dynamic in versatility.
In Midland, Texas, Shamrock Field Services performs these alignments with the LEVALIGN EXPERT. When checking a large frame like an Ariel JGZ the LEVALIGN EXPERT gives the user consistent, reproducible measurements they can trust to make critical adjustments. During a recent job in Odessa, Texas the Shamrock group used their ROTALIGN ULTRA IS and LEVALIGN EXPERT to check both the coupling alignment and the top rail flatness of an electric drive motor and JGZ compressor in less than an hour.
My experience is with both the INCLINEO and LEVALIGN EXPERT; let’s just say I am glad we purchased the right tool for the job. The LEVALIGN EXPERT is quick and very easy to operate. It cuts time and makes for a more proficient report. Hands down the LEVALIGN EXPERT is the way to go.” —Geoffrey Jameson, Shamrock Field Services
The initial setup of the LEVALIGN EXPERT for a top rail measurement is simple. Because the LEVALIGN EXPERT’s self-leveling laser adjusts to the surface plane automatically – the system can be put anywhere within line-of-sight for the rails to be measured. Either a magnetic plate or a tripod may be used to position the laser. Before placing the sensor on the rail via magnet, you want to make sure the rails are clean and clear of debris or excess oil. Once the rails have been cleaned the LEVALIGN EXPERT automated sensor is placed at the first point to be taken. The motorized sensor will lock into the laser and allow each point to be measured. Eight total points should be taken in no particular order.
I would recommend that if you are going to check the top rail of your compressor to use the LEVALIGN EXPERT, it will save time and headache in the long run.” —Dewayne Atwood, Shamrock Field Services
Taking measurements with the LEVALIGN EXPERT takes less than 5 minutes on JGZ and other large scale compressors due to the freedom of a powerful Bluetooth. With the measurement data recorded, adjustments can be made by viewing the information in the rugged ROTALIGN ULTRA computer. Several options are available for scale, 3-D view or Table view. These numbers can be plugged into the ER-82 spreadsheet or used in the Alignment Center software. Reporting may also be done in the field through the USB option.
Versatility in many work environments is a key factor to the completion of a job and the ease of use with the LEVALIGN EXPERT sure outshines the INCLINEO.” —Robert Beck, Shamrock Field Services
Special thanks to the team at Shamrock Field Services, a gas compression service company, for sharing with us their success with our products.
March 10, 2015
Being a successful condition monitoring (CM) analyst requires qualities such as intelligence, dedication, a thick skin, willingness to help others, ability to focus, and more. Success in this profession is not easy. In fact, it can be argued that success is a constant struggle. The most successful CM analysts will have certain traits that are keys to their success; however, possibly the most important is the drive to “know” – to know what is causing that anomaly, defect, or early failure.
Read my entire article at PLANT SERVICES: Keys to Condition Monitoring Success