Sunday, May 2, 2010
High frequency acoustic excitation downstream of pressure reducing device potentially results downstream piping failure due to Acoustic Induced Vibration (AIV). Earlier post "Principle in Eliminating & Minimizing AIV Impact" discussed about common principles in minimizing Sound Power level (PWL). Several type of low noise trim in control valve is typical device used to reduce Sound Power Level. There are multi-stage type, multiple path type and Labyrinth-disk type. Details can be read found in "Measures & Technique In Eliminating / Minimizing PWL" and typical low trim trim e.g. WHISPER trim from EMERSON FISHER and V-LOG from DRESSER MASONEILAN are included. This post is to include another two more low noise trim from FLOWSERVE VALTEK.
Two type of low noise trims are provided by FLOWSERVE VALTEK. They are MEGASTREAM and TIGERTOOTH.
MEGASTREAM trim eliminates the problem of control valve noise by dealing effectively with gaseous pressure reduction, and by controlling turbulence carried into the downstream piping using multi-stage expansion and distribution. Each stage is designed to take a small pressure drop and prevent high velocities present in single-throttling-point trims.
Below is the typical noise reduction / Sound power attenuation curve for MEGASTREAM low noise trim. Maximum attenuation can be as high as 28 dB.
Read more in "VALTEK MEGASTREAM".
TIGER TOOTHTIGER TOOTH design involves concentric grooves (or teeth) machined into the face and backside of a series of circular stacked discs (called a stack), which also acts as a seat retainer. Flow passes from the center of the stack through the teeth undergoing a series of sudden contractions and expansions. Pressure decreases progressively in steps via series of teeths and stacks.
Below is the typical noise reduction / Sound power attenuation curve for TIGER TOOTH low noise trim. Maximum attenuation can be as high as 30 dB.
Read more in "VALTEK TIGER TOOTH"
- Measures & Technique In Eliminating / Minimizing PWL
- Principle in Eliminating & Minimizing AIV Impact
- Energy Input or E-method In Assessing AIV
- Assess AIV with "D/t-method" with Polynomial PWL Limit Line
- Assess AIV with "D/t-method" with Logarithm PWL Limit Line
- Extra Attention to Common Point and Similarity on AIV Failure
- Piping Excitation When Expose to Acoustic Energy
- Acoustic Induced Vibration (AIV) Fatigue