In many areas of the industrialized world, natural gas transmission and distribution companies provide gas to commercial and industrial users, as well as many of us in our residences. For commercial users, such as apartment complexes, and industrial users, stable pressure is critical for operations.
A 6-page whitepaper, Solving Instability Issues in Commercial and Industrial Natural Gas System Applications, explores some of the causes of instability and ways effective pressure regulation technology can address these challenges. Once challenge is resonance. Pressure regulators have moving parts which can oscillate at resonant frequencies causing noise and wear.
Resonance occurs when the set of a vibrating system’s characteristics cause it to oscillate at much higher amplitudes in a specific frequency range.
The most common mode of instability is harmonic instability. It:
…is caused by a collection of system characteristics during normal operation which results in a “humming” or “buzzing” sound emitting from the regulator due to the vibration of the diaphragm or other parts.
Changes in flow rate or piping & regulator system components may:
…also change the frequency required to excite the regulator to a resonance condition.
Another condition leading to instability is hunting. It:
…is a condition in which a regulator’s outlet pressure slowly fluctuates on either side of the set point. In this condition, the regulator will “hunt” for a desired pressure but certain factors may prevent it from quickly reaching equilibrium.
Turbulent flow can lead to hunting conditions. In gas systems this turbulent flow can be caused by:
…elbows, swages, valves and meters.
Other causes include piping characteristics, effective flow area, flow characteristics, and regulator size. Flow meters in the line can have operating frequencies near the pressure regulators inducing instability from feedback. Effective spacing between these elements in the flow stream can eliminate this feedback condition.
Some ways to address these pressure regulator instability issues include proper sizing and selection of the pressure regulator, properly sized vent piping, proper placement of control lines, and use of regulators with internal or dual registration instead of those with external registration.
A Fisher CS800 Series regulator stabilizer cartridge can increase:
…system stability with no piping and/or minimal specification changes and can be installed quickly in the existing installation and without using any special tools. Ultimately, it eliminates most instances of regulator noise from system instability and minimizes end user complaints.
Read the whitepaper for specific recommendations in each of these ways to reduce instability. The best pressure regulator installation is the one the quietly performs its duties without disturbing everyone around it.
Visit the Regulators catalog area on Emerson.com for more types of pressure regulators best suited for your applications. You can also connect and interact with pressure regulation experts in the Valves, Actuators & Regulators group in the Emerson Exchange 365 community.
