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Instrument Air Quality

in Nuclear Power Production and Pneumatic Instrument Use

Nuclear Power Production

The quality standard for instrument air is ANSI/ISA-S7.0.01-1996. The American National Standards Institute’s (ANSI) Instrument Society of America (ISA) recognizes the importance of clean dry air (CDA) and the role it plays in running pneumatic controllers and pneumatic instruments. Instrument air that is not clean and dry can have devastating effects on the instruments it controls resulting in system inaccuracies or failures.

ANSI/ISA-S7.0.01-1996 addresses 4 elements of instrument air quality; dew point, particle size, lubricant, and contaminants. The compression process dramatically increases condensation and contaminants in the air once it is compressed. Learn more about Compressor Contamination here. Compressed gas contaminants while possibly harmless prior to compression, can have devastating results once they have been compressed. The instrument air quality standard lists the following items to help monitor these elements of concern: Monitored alarms or per shift monitoring for dew point control and filters for particle control. Automatic oilers are discouraged due to the potential for fire and scrubbers or absorbers are suggestions provided, and proper intake placement is suggested for corrosive and gas contaminants. Particulate contaminants can be introduced by any number of sources including the intake or the compressor itself. Desiccant dryers while very helpful and necessary, create particle dust that is often overlooked. Particulate contaminants can clog and corrode orifices in the system. So, how do you determine if you need to make any of these adjustments or determine if your proactive measures are working? It’s simple — conduct regular instrument air quality standard testing.

Industry-Wide Standards

In order to ensure safety and improve nuclear power plants’ efficient production of electricity, instrument air systems require regulation, improvement, and monitoring. In 2014, the nuclear industry came together to make improvements to compressed air quality, efficiency, and safety. The Nuclear Regulatory Commission (NRC) and the Institute of Nuclear Power Operations (INPO) issued regulations; the Electric Power Research Institute (EPRI) set maintenance standards; and the Compressed Air Nuclear Users Group (CANUG) improved air system design.

By setting industry-wide standards, INPO promotes excellence in the operation of nuclear electric-generating plants and speaks to compressed air evaluations in their Significant Operating Event Report (SOER). SOER 88-1 (Instrument Air Systems Failures) stresses the importance of Instrument Air Quality and combines limits from ISA-7.0.01-1996 and analytical methods from ISO 8573 to create a comprehensive standard that addresses an air system’s potential for contamination.

Trace Analytics’ sampling kit provides an easy solution to satisfying ANSI/ISA, ISO 8573, and SOER requirements.

At Trace Analytics, our team of experts is dedicated to providing safe, clean air at the highest quality standards. Our A2LA accredited laboratory specializes in compressed air and gas testing, and our experts have participated in educational endeavors to improve pneumatic tools and instrument air quality safety by attending and speaking at the Air-Operated Valve Users’ Group (AOVUS Group) Conference and Compressed Air Nuclear Users Group (CANUG) Meetings.

Instrument Compressed Air & Gas Testing Specifications

Trace Analytics, LLC can test to a wide variety of specifications. The most commonly-used specification for Instrument Air Quality is shown below:

ANSI / ISA—S7.0.01-1996

Particles Water Lubricant Content
By Particle Size
maximum number of particles per m3
Vapor Pressure Dewpoint
>40 µm °C °F ppm
NONE < 4 < 39 ≤ 1
A maximum 40 micron particle size in the instrument air system is acceptable for the majority of pnuematic devices. Pneumatic devices that require less than 40 micron particle size shall have additional filtration. Pressure dew point at the dryer outlet shall be at least 10°C (18°F) below the minimum temperature to which any part of the instrument air system is exposed. It shall not exceed 4°C (39°F) at line pressure. Should be as close to zero as possible, and under no circumstance shall it exceed 1 ppm.
For Nuclear industry - INPO requirements include ensuring that air testing and sampling methods are performed in accordance with the most current ISO-8573 for solid particle content (particulates), humidity (dew point), oil aerosol content, and oil vapor and organic solvent content. At the optical microscope magnification used to determine compliance, the entire filter is scanned with 5 µm being the minimum particle size determined. If no particles are detected, a <5 µm value is entered. Contact Trace for details.
Air & Gas Specifications referenced above may be viewed and/or purchased from: ANSI - American National Standards Institute