National Instruments Products for Oil and Gas Condition Monitoring

1. Overview of Oil and Gas Condition Monitoring Systems

The oil and gas industry is at the forefront of technology adoption as it looks for new ways to access and refine ever more hard to reach oil supplies. With this increase in technology, however, comes an increase in the number of critical machines used in exploration, production, transport, and refinement. Condition monitoring offers the ability to reduce cost of ownership for these critical machines by predicting failures before they occur, which allows proper maintenance to be effectively scheduled.

An oil and gas condition monitoring system is built around the asset being monitored, with the measurements chosen based on the parameters most likely to indicate failure. A typical block diagram for an oil and gas condition monitoring system is shown in Figure 1. Sensors and hardware are used to acquire physical signals, and then software is used to analyze these signals into a meaningful machine condition and predict failure.

Figure 1. Block Diagram Showing a Typical Oil and Gas Monitoring System

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2. Hardware - Measuring the Physical Signals

You can measure a variety of physical signals off your assets of interest, from vibration and strain to temperature and oil quality. By measuring these different signals together, you can generate a better picture of the assets state.

National Instruments offers two main platforms for reading in the signal from these different sensors: C Series and PXI. C Series is an industrial, portable form factor that is ideal for distributed monitoring or portable diagnostics. PXI offers a higher-performance, higher-channel-count system for use in test setups or much larger monitoring systems.

C Series	PXI
Rugged operating spec (temperature and shock) 4- to 32-channel systems Portable or fixed implementation USB or Ethernet based (NI CompactDAQ or CompactRIO) Embedded processing, storage, and control Sample rates at more than 50 kS/s per channel	High performance and processing High-channel-count systems (500+) Solid-state hard drives for rugged data storage Ethernet, Modbus, RS232, and many other industrial buses Sample rates at more than 200 kS/s per channel

• Use the CompactRIO Advisor to build your own embedded system
• Use the NI CompactDAQ Advisor to build your own portable system
• Use the PXI Advisor to build your own high-performance, high-channel-count system

Vibration

Vibration monitoring is one of the most important aspects in oil and gas monitoring because it helps determine the condition of rotating equipment. This is especially important for pumps, compressors, drills, and various types of turbomachinery. Depending on the application's frequency range, you can use either position sensors (0 to 36,000 CPM), velocity sensors (36,000 to 60,000 CPM), or accelerometers (60,000+ CPM) for measuring vibration. These sensors are rigid mounted to the asset and return an analog voltage signal proportional to the instantaneous motion they sense. For more information on accelerometers, read the Sound and Vibration Transducers Guide.

For rotating equipment, the sensor data must undergo order analysis to display vibration signals in terms of the harmonics of the asset being monitored. These harmonics provide insight into the performance of various components of the machine and allow for easier diagnosis. For more information on order analysis and signal processing, read the Software section below.

Additionally, vibration measurements can be made on nonrotating equipment, usually to indicate unexpected movement on pipelines or other static assets. By measuring vibration, you can predict, be alerted to, and quickly react to any changing conditions that may threaten your asset.

To measure a vibration sensor, your data acquisition device should have 

• High sampling rates to fully capture the vibration signature
• High dynamic ranges to detect small vibration changes
• Simultaneous sampling on all channels so data can be directly compared and phase matched
• Antialiasing filters to prevent unexpected vibration measurements

For measuring vibration, National Instruments offers two major platforms that meet all of the above requirements.

*Note: You can choose from a variety of PXI modules for these applications. For higher-channel-count and even better performance options, click here.

Oil Lubrication Quality

Oil is a key component in wind systems because improper lubrication can reduce efficiency and cause increased friction, resulting in heat and increased vibration that lead to mechanical failure. Most bearing and gear wear results from incorrect oil lubrication. Monitoring of oil lubrication usually consists of oil contaminant particle counting and moistness measurements.

You can use oil particle counting to determine the quality of oil and verify the existence of contaminants. These contaminants can come from either dirt and grit introduced into the system or from metal shavings and other particles that corrode and break off internal machine parts. Contaminant particles cause excessive wear, initiate rolling element bearing fatigue, and clog filters. Particle counters usually communicate with the RS232 protocol. 

Moisture measurements indicate the amount of water contamination in oil lubrication, which causes premature component failure and oxidization of the oil lubricant. Oil moisture sensors return their measurements through either an analog voltage or current or, similar to the particle counters, through RS232.

For measuring oil quality with both RS232 protocol and voltage input, National Instruments has the following offerings.

*Note: You can choose from a variety of PXI modules for these applications. For higher-channel-count and better performance options, click here.

Strain

Strain measurement is largely used for structural monitoring in the oil and gas industry. The large structures holding up various oil and gas assets are critical to the performance of the machines they carry and can serve as a warning of an out-of-balance machine.

For measuring strain, National Instruments offers two major platforms that meet all of the above requirements.

*Note: You can choose from a variety of PXI modules for these applications. For higher-channel-count and even better performance options, click here.

Acoustic

Acoustic monitoring is increasingly used to detect gas leaks in pipes. When high-pressure gas leaks into the atmosphere, the pressure differential creates a high-velocity flow with a unique acoustic signature both in the air and in the solid material making up the pipe. There are measurable frequencies created in both the audible frequency band (12 to 20 kHz) and in ultrasonic frequencies above the normal range of human hearing. Being able to detect these leaks and respond to them quickly not only saves product but also is a significant safety issue.

A microphone sensor has many of the same data acquisition requirements as an accelerometer:

• High sampling rate to fully capture the vibration signature
• High dynamic range to detect small vibration changes
• Simultaneous sampling on all channels so data can be directly compared and phase matched
• Antialiasing filters to prevent unexpected vibration measurements

For measuring acoustics, National Instruments offers two major platforms that meet all of the above requirements.

*Note: You can choose from a variety of PXI modules available for these applications. For higher-channel-count and even better performance options, click here.

Temperature

Temperature is another measurement that you can use for preventive and predictive maintenance. When machines begin to fail, they often have increased friction, which is converted to heat. Heat is not only a signature of machine failure but also a contributor to further failure.

You can measure temperature with a variety of sensors, but the most common sensors are thermocouples and resistance temperature detectors, or RTDs. These sensors often require signal conditioning because of their low output ranges. An ideal data acquisition device for temperature sensors should have

• Amplification to increase the low output range of the sensor
• Cold-junction compensation to convert the relative sensor readings to an absolute temperature
• 50/60 Hz noise rejection, which eliminates environmental noise

For measuring temperature, National Instruments offers two major platforms that meet all of the requirements above.

Summary

The following is a summary of the recommended NI C Series and PXI modules for the various measurements that could be required by an oil and gas condition monitoring system.

• Use the CompactRIO Advisor to build your own embedded system
• Use the NI CompactDAQ Advisor to build your own portable system
• Use the PXI Advisor to build your own high-performance, high-channel-count system

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3. Software - Data Recording and Processing

LabVIEW

For oil condition monitoring, NI LabVIEW software combines advanced signal analysis with a user-defined GUI (graphical user interface). Additionally, LabVIEW provides the tools for all of the data acquisition from the various NI hardware platforms and can even perform data logging and database communication.  

LabVIEW offers the flexibility of creating a monitoring system that is perfect for your application while providing all of the standard processing features you find in any other analysis environment, such as statistical analysis, fast Fourier transform (FFT), and root-mean-square (RMS) measurements.

To learn more about using LabVIEW for condition monitoring, view the webcast Using LabVIEW for Embedded Condition Monitoring and Machine Protection.

Sound and Vibration Measurement Suite

For more advanced analysis than that provided by LabVIEW, take advantage of the NI Sound and Vibration Measurement Suite. This suite offers order analysis, waterfall plots, envelope analysis, and more add-ons to LabVIEW. To learn more about the Sound and Vibration Measurement Suite, click here.

Figure 2. Orbit Plot and Analysis in LabVIEW

Figure 3. Waterfall Plots for Run-Up and Run-Down Analysis