Complementary Condition Monitoring Boosts Reliability

January 10, 2017

As Published by COMPRESSORtech2 Magazine October 2016 issue
by Karl Hoffower – Condition Monitoring and Reliability Expert for Failure Prevention Associates

Combining ultrasound and vibration sensing adds precision to recip valve analyses

Over the past decade, ultrasonic condition monitoring of reciprocal compressor valves has become more widely known. However, it does not seem to be widely used.

Ultrasonic testing measures high-frequency sound waves, well above the range of human hearing. These ultrasound devices record the high-frequency signals for analysis later. Trending valve cap temperatures is the most common condition monitoring technique for monitoring
compressor valve health.

Ultrasonic testing of compressor valves and vibration monitoring of rotating components are an informative, preventative-maintenance practice. Compressor valve deficiencies with opening, closing or leaking may be diagnosed using the ultrasound recording functions.

Steven Schultheis, a Shell Oil Co. engineer, addressed the issue in a paper presented at the 36th Turbomachinery Symposium in Houston in 2007.

“Trending valve temperatures have proven to be valuable in identifying individual valve problems, but are most effective if the measurement is made in a thermowell in the valve cover.” Schultheis wrote. “Ultrasound has proven to be the preferred approach to analysis of valve condition.”

Failure Prevention Associates completed an experiment with a major midstream gas transmission company to see if this type of condition monitoring tool can effectively find fault conditions well before other technology used.

Ultrasound meters (such as the SDT270 from SDT Ultrasound Solutions) have digital readouts that indicate the level of ultrasound detected. These devices have been used for decades to “hear” air, gas and vacuum leaks. The intensity or amplitude of the signal is expressed in decibels — microvolts. (dB[A] μV). The dB(A) is a common intensity unit for sound intensity; μV designates the engineering reference unit being used with a piezoelectric sensor.

Converting an airborne ultrasound detector with a contact sensor allows a technician to monitor what is happening inside a machine, whether it is a bearing, steam trap, or valve.

Ultrasound detectors are designed operate in a specific and narrow frequency band. Then through “heterodyning” step high frequency sounds down into an audible format that the technician can hear though headphones. During the heterodyning process the quality and characteristic of the original ultrasound signal is preserved.

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Do No Harm in 2017! The Hippocratic Oath Applied to Reliability

January 3, 2017

As Published by Uptime Magazine December/ January 2017 issue

Do No Harm: The Hippocratic Oath Applied to Reliability

The Greek physician Hippocrates (c.460 BC – c.370 BC) is credited with an oath that was meant to provide certain ethical standards a physician was to uphold. While maintenance is not of the magnitude as being a doctor, organizations would do well to apply portions of the Hippocratic oath to their maintenance practices. Two such examples are: “…to teach them this Art, if they shall wish to learn it, without fee or stipulation; and that by precept, lecture, and every other mode of instruction, I will impart a knowledge of the Art to my own sons, and those of my teachers, and to disciples…” and “I will follow that system of regimen which, according to my ability and judgment … and abstain from whatever is deleterious and mischievous.” This article focuses on the latter, “and abstain from whatever is deleterious and mischievous,” or in 21st century vernacular: Do no harm.”

Maintenance reliability professionals have a responsibility to their superiors to deliver results that improve the bottom line via increased uptime and productivity. But they also have a responsibility to those technicians who are expected to assist them in the process of increasing asset uptime and improving reliability. Regardless of your certification or the acronym attached to your signature block, without the technician’s solid understanding and performance of the basics, you will not achieve either goal. Two key ingredients of any reliability effort are precision installation and maintenance practices. Without them, you will find yourself replacing the same motors, pumps, etc., repeatedly.

From the reliability-centered maintenance (RCM) teachings of Stanley Nowlan and Howard F. Heap, both engineers at United Airlines, and John Moubray, the originator of RCM2, it is learned that there are six distinct failure curves. Furthermore, as many as 68 percent of failures can be attributed to infant mortality or failure induced at start-up/installation.

Figure 1: Failure patterns

Figure 1: Failure patterns








the full article to learn how precision installation and maintenance practices are two key ingredients of any reliability effort.

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Improve your machine performance by eliminating pipe strain

December 27, 2016
Premature machine failure can easily lead to high maintenance costs and operational losses. Misalignment is a leading cause of premature failures. An often-overlooked contributor to misalignment is pipe strain.

Premature machine failure can easily lead to high maintenance costs and operational losses. Misalignment is a leading cause of premature failures. An often-overlooked contributor to misalignment is pipe strain.

Reposted from EASY-LASER® blog

There are basically two types of pipe strain: static and dynamic pipe strain. Static pipe strain occurs both when the machines are operating and when they’re not running. This is most likely the type you’ve been trying to eliminate. Dynamic pipe strain, on the other hand, is a condition that only takes place when the machines are operating.

Strain, which is the deflection and positional change resulting from pipe stress, comes from the suction and discharge piping, and creates stresses on the machine frame or casing that that in turn spread to the equipment body. A result of this is often a change in the alignment of the shaft. It also results in distortion of the machine casing which misaligns the bearings within the machine, resulting in very harmful vibration and increased radial loads on the bearings. So, before attempting shaft alignment, you should ensure that suction and discharge piping are not causing strain on your machines.

Static pipe strain and its effects are fairly simple to control, and you can use any of the Easy-Laser® shaft alignment systems to measure the strain and help eliminate it. Here’s how: simply mount the system in the normal manner as when you perform the shaft alignment. Then:

  1. Position the measuring units at twelve o’clock. Use the Values program and set both units to zero.
  2. Rotate the shafts to the three o’clock position, and note if the values are not zero. Rotate the shafts back to twelve and confirm the zero setting.
  3. Now connect or disconnect the piping. Any changes to the values for the twelve and three o’clock positions is the result of pipe strain and should be corrected, which will require careful pipe fitting. What you are seeing is movement transmitted though the casing to the bearings and shaft.

Dynamic pipe strain is more difficult, because it only occurs when the machines and piping are at operating conditions. And a good proportion of this type of pipe strain may be a consequence of thermal expansion of the piping and the weight of system fluid. This explains why the dynamic pipe strain is not a fixed state and why it might be difficult to handle.

We understand that this can be quite a challenge, however, we believe you have a lot to gain from minimizing dynamic pipe strain. And there are effective tools for this purpose: Our Easy-Laser measuring program has a great feature that registers measurement values automatically for a specified amount of time and frequency of measurement. This is very useful for looking at differences between a machine that’s up and running and one that’s down. The data can also be transferred to the EasyLink™ software, where you can see the results more clearly, in the shape of a graph to scale.

The existence of pipe strain indicates that more than just alignment is needed for optimal machine performance; there are other important factors to take into consideration. This requires flexible measurement systems that will support you and help you reach your goal. You need more than a shaft alignment system; you need a total alignment solution.

We invite you to watch our Pipe Stress Know-How video to learn more about the effects of running equipment with pipe stress.

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A clean and balanced approach to equipment maintenance

December 20, 2016

Proper equipment function requires a properly aligned and balanced machine.  Allowing a machine to operate with an unbalance condition can result in bearing damage, cracks, loose components and many other costly maintenance issues.  Loose debris can dislodge and impact the balance quality of a machine. Debris buildup on the impellers/blades, and other rotating parts can create unbalance conditions. Before balancing the machine it is very important that the rotating surfaces (blades, etc.) are cleaned of any debris. Removing buildup will help ensure that the machine can be properly balanced and remains in a balanced condition.

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Turbine Alignment made Easy with Easy-Laser® E960 System

December 15, 2016

Steam turbine internal alignment applications require high precision, ease of use and reliability. The Easy-Laser® E960 system is used to align diaphragms and internal components and delivers all these things.












Setup is fast and simple. There is no need to precisely center your detector to the bore or the laser to the rotor to perform position checks. Simply orient the sensor into laser range, and the display unit does the rest to calculate the center. Your rotor positions are entered digitally for greater accuracy and speed of setup. Wireless components streamline the setup—no cables to get in the way!

Take three points over 180 degrees on a bore just as you would with a tight wire, or use the multipoint measurement to find the center of bores and check for ovality.








The Easy-Laser E960 features an optional reference control sensor for greater reliability and precision.  No more guessing whether your reference line (the laser beam), moved during measurement—you are in control of its position at all times. Even if the beam moves over time due to environmental factors, the reference control sensor allows the system to automatically adjust for such movement to ensure all your readings stay highly accurate.









Need to measure the flatness of the shell?  Simply add the D22 rotating laser and flatness readings can be taken using the same sensor as the one you  use for internal bore alignment. Both the top and bottom shell can be measured without having to remove the bolts.












This system works with your existing processes. The Easy-Laser E960’s intuitive display allows for entry of diaphragm positions into your excel spreadsheets or take advantage of the included Easy-Link software to present, process and document the turbine alignment in one complete and easy to use package.








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