Hidden Failures can expose your facility to increased risks and serious consequences

February 24, 2015

A hidden failure is not obvious under normal circumstances. Hidden failures can expose your facility to increased risks that may have serious consequences. The sources within your facility for hidden failures may be many. A good reliability program will give special consideration to these types of potential failures and their associated risks.

Have you considered that the software used within your facility may lead to hidden failures in a sense? Your software may lack documentation, reporting and analytical capabilities. Data may be hidden, improper diagnostics made, or corrective action not taken based upon the information, etc., all of which can lead to equipment failures. Intentional misuse of the information may be possible as well without the ability to apply proper oversight.

Make sure the software you use properly collects, stores and reports information of value that can be used to drive your maintenance and reliability efforts. Make sure that the information is correctly analyzed and appropriate action taken. Otherwise, your software tools may give you indications of problems that go unmitigated until costly failures occur.

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3 Easy Steps for Quality Vibration Data Collection

February 17, 2015

Grease, excess paint, etc. can affect the quality of collected vibration data. The below 3 steps will ensure that the best possible data quality is always collected:

  1. Always carry a rag, scraper, brush, etc. to clean each measurement location before acquiring vibration data.
  2. Make sure that the measurement surface is flat and the sensor is not rocking during data collection.
  3. Hold the cable during data acquisition to prevent movement that may induce electrical noise and affect measurement quality.

Learn about the Triboelectric effect on vibration accelerometers

 

 

 

 

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Gas Turbine Positional Change Monitoring and Measurement

February 10, 2015

A large gas turbine-compressor system experienced high vibration when load approached 92%. Customer demanded the promised 98% from the manufacturer. These compressors are used along a gas pipeline that moves natural gas from Texas to South Florida.

LUDECA was contracted to determine the stability (or lack thereof) of the turbine structure at 16 different locations on the turbine. 16 PERMALIGN triple prisms capable of simultaneously detecting vertical and horizontal displacement were affixed to strategic locations on the turbine (see Figures 1 and 2.)

Permalign Monitors Gas Turbine

Fig 1: PERMALIGN Triple Prisms Mounted on Gas Turbine

Permalign Triple Prisms Gas Turbine

Fig 2: Close-Up of PERMALIGN Triple Prisms Mounted on Gas Turbine

The absolute move of these locations was recorded by 16 separate PERMALIGN monitors mounted on sturdy pedestals rigidly affixed to the floor (see Figure 3.) One monitor was used per triple prism.

Permalign Mounted Sturdy Columns

Fig. 3: PERMALIGN Monitors Affixed to Sturdy Column Pedestals

After continuous monitoring and measurement over several hours, it was found that the front turbine supports were not stable when the extra load was demanded.

Based on the findings, the manufacturer re-designed the front supports of the turbine to withstand the increase in loads.
With the successful solution obtained with the help of the exact positional change information supplied by the PERMALIGN system, the manufacturer was able to secure an order for several of these turbine-compressor systems.

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Size Matters! Proper Pump Equipment Specifications and Design are Critical in Ensuring Long Term Reliability

February 3, 2015

Centrifugal pumps come in a variety of shapes and sizes and are used in diverse ways to fulfill many different applications. These pumps deliver a life sustaining liquid directly to our homes that is required for our very survival. For example, during emergencies these pumps provide fire departments with the water needed to extinguish fires. Their value is critical, but their importance is often taken for granted.

Centrifugal pumps are designed to deliver a specific flow and pressure as dictated by the application. Centrifugal pump curves typically show the design rated flow (usually expressed in gallons per minute or GPM) across the X axis of the curve and the pumps total pressure (total head) along the Y axis. Different size impellers can be installed on these pumps depending upon the design requirements. The engineer must accurately calculate the required operational parameters, because once installed the pump will operate at the point where the system head intersects the pump curve.

Based upon the pump curve below, several different impeller diameters can be utilized for this specific pump ranging from 7½ to 9½ inches. In our hypothetical system we have calculated a total system head of 100 ft. and we need 50 GPM for sufficient cooling in our manufacturing process. Based on our calculations an 8½ inch diameter impeller would result in the pump meeting our design point of 50 gpm @ 100 ft. head @ 73 % efficiency.

Pump Selection

So far everything is working out perfectly for our project, but if the system head is not calculated correctly or the pump is ordered with the wrong diameter impeller we will have process and reliability problems.

If the correct diameter impeller (8½ inches) isn’t specified, then the pump manufacturer may simply supply the pump with the maximum diameter impeller (9½ inches). If we installed our new pump with the wrong size impeller it would operate well to the right of the required operating point of 50 gpm @ 100 ft. head. This would result in excessive vibration levels, motor overload, reduced bearing life, seal problems and cavitation problems. As a result, we would experience higher maintenance costs, higher operational costs, reduced MTBF and reduced pump efficiency.

The chart below shows that centrifugal pumps are usually most reliable when operated from 80% to 110% of their best efficiency point (BEP). Outside of this range unwelcome reliability problems will occur.

Pump Reliability Curve

The scenario above occurs more often than realized! Many pumps are operated outside of their best efficiency range and unwanted consequences are experienced. A good reliability program will always seek to determine the root causes of failures. Simply replacing failed components such as worn impellers, damaged bearings, etc., does little to address the root cause of the problem. Not understanding why a component failed will doom you to replace it again in the future and true reliability gains are not made. Proper equipment specifications and design are critical in ensuring long term reliability. It is very difficult or impossible for maintenance to overcome poor design or specification. Centrifugal pumps that are specified properly for the application, correctly installed, aligned and balanced will increase your pumping system reliability. This will lead to reduced maintenance costs, improved uptime and other valuable results.

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Accurate Conveyor Drive Alignment Solves Vibration and Bearing Temperatures Issues at Texas mine

January 27, 2015

At a mine in Texas unacceptably high vibration levels and high bearing temperatures were being observed on an 1800 RPM Marathon electric motor coupled to a Lufkin gearbox needed to drive the world’s second longest conveyor system (21 miles). Good shaft alignment is crucial. Obviously the alignment has to be done uncoupled since the gearbox shaft cannot be rotated manually. Alignment was originally attempted with dial indicators; however, the shaft and coupling surfaces where the indicators could mount were not in the best condition and this was causing significant repeatability problems with the alignment readings.

Uncoupled Alignment

Fig 1: Rotalign mounted on uncoupled shafts

Their main issue was that the gearbox could not be rotated by hand. We suggested to the customer that he use a ROTALIGN ULTRA system, taking advantage of the Pass Mode measurement capability. The customer purchased the ROTALIGN ULTRA and a specially designed ALI 2.230 magnetic sliding bracket. Readings were taken in pass mode as suggested. In this mode, hundreds of readings are taken at many different shaft rotational positions, hence improving the chances of getting repeatable readings. The excellent repeatability obtained can be seen in the ROTALIGN’s Measurement table in Figure 2 below.

Uncoupled Alignment Measurement Table

Fig. 2: ROTALIGN Measurement Table

Another huge advantage of using the ROTALIGN ULTRA in the Pass Mode mode is that thanks to the standard deviation value obtained from the readings a very clear picture emerges of the quality of the data obtained while taking the readings. Any rogue measurements caused by surface imperfections in the gearbox coupling can be eliminated without compromising otherwise good data. The ROTALIGN ULTRA’s Technical Note # 12 – for Non- Rotating Shafts was provided to the customer to better guide the process.

Accurate readings were obtained quickly and efficiently, resulting in many man-hours saved on this critical alignment job. By achieving good alignment the customer was able to solve both the vibration and bearing temperatures issues and was henceforth able to move the desired amount of coal from the mine to the power plant 21 miles away.

 

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Data collection in a computer aided machine like a CNC machine

January 20, 2015

Today’s manufacturing facilities increasingly depend on Computer Aided Machines (CAM) and robotics in their many processes. This highly technologically advanced machinery is designed with many failsafes and protection systems capable of shutting down the machine to maintain the integrity of the part being machined and the equipment itself.

As these machines typically run at very high speeds, it is of great importance to perform condition monitoring on their bearings, motors and gearboxes. Large amounts of debris and fluids can accumulate inside these machines during normal operation. This can complicate the use of a regular sensor and cable assembly to collect vibration data.

Consider using a small sensor with an integral cable and an armored jacket along with a vibration analyzer like the VIBXPERT or an online condition monitoring system such as VIBNODE. This combination of technology, sensor(s) and cable will allow your facility to reliably monitor the health of your CAM machines and maintain both performance and reliability.

Sensor-with-integrated-cable
Sensor with integrated cable

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