Following are the various acoustical/mechanical piping design calculation procedures offered by MLB Engineers, Inc. to control gas pulsation induced vibrations for reciprocating compressor units:

  • MLB Design Ia - Analytical Analysis (API 618 Design Approach 1)
  • MLB Design Ib - Digital Analysis
  • MLB Design IIa - Active Acoustical Analysis (Abridged API 618 Design Approach 2)
  • MLB Design IIb - Active Acoustical Analysis (API Design Approach 2)
  • MLB Design IIIa - Active Acoustical/Mechanical Analysis (Abridged API 618 Approach 3)
  • MLB Design IIIb - Active Acoustical/Mechanical Analysis (API Design Approach 3)

All of the above design procedures offered by MLB Engineers, Inc. utilize the same basic gas pulsation control concepts (surge volumes, choke tubes, filter volumes, acoustical filters, etc.) with the proposed major gas piping designs (in most cases) similar in sizes, lengths and configuration regardless of the calculation procedure used. A brief description of the above listed calculation procedures are as follows:

  • MLB Design Ia - The design procedure as outlined in the ASME Paper No. 71-Pet-3 consists of locating the major acoustical resonant frequencies analytically for maximum attenuation of gas pulsation amplitudes for the attached piping systems. Gas pulsation amplitudes are not predicted for this analysis.
  • MLB Design Ib - This design procedure is identical to MLB Design Ia except the analytically calculated major acoustical resonant frequencies are verified and adjusted if required by passive digital analysis.
  • MLB Design IIa - Active acoustical analysis per abridged API 618 Design Approach 2 guidelines without a summary report.
  • MLB Design IIb - This design procedure is identical to MLB Design IIa except a summary report is provided.
  • MLB Design IIIa - Active acoustical/mechanical analysis per abridged API 618 Design Approach 3 guidelines without a summary report.
  • MLB Design IIIb - This design procedure is identical to MLB Design IIIa except a summary report is provided.

The calculation procedures for MLB Design Ia and Ib have been used successfully for many compressor installations particularly for lower horsepower high speed reciprocating compressor units in normal gas services. MLB Design IIa and IIb calculation procedures consists of simulating the unit piping from the inlet scrubber through the final aftercooler including station piping (scrubber inlet / aftercooler outlet piping) if available for the study. The recommended piping designs are based on the data predicted by the simulation and our experience with acoustical piping analysis for over 35 years. The results are submitted on piping sketches without a summary report for MLB Design IIa; whereas, MLB Design IIb includes a summary report with predicted acoustical characteristics (pulsation amplitudes, shaking forces, pressure-volume diagrams, etc.). The summary report contains sufficient data to describe the acoustical characteristics of the proposed and recommended piping systems and how the predicted pulsation amplitudes compare to API's suggested guidelines at critical points in the piping system. MLB Design IIIa and IIIb calculation procedures are identical to MLB Design IIa and IIb respectively except mechanical analyses are included.

If there is a question as to what calculation procedure is appropriate for your particular compressor unit(s), let us help you determine the desired analysis to conduct.

MLB Designs II or III calculation procedures will consist of the following:

  1. Simulate the client's proposed (or MLB's pre-simulation) piping system to determine the acoustical characteristics (pulsation amplitudes/shaking forces) for the compressor units operating under design operating conditions (pressures, temperatures, gas compositions, flows, compressor cylinder loading, etc.).
  2. Provide a pre-simulation piping design (if required) indicating bottle/piping sizes and lengths and the preferred layout of the onskid piping so that long delivery items can be ordered.
  3. Adjust the pre-simulation piping design where required due to acoustical modeling and layout considerations as determined by client.
  4. Mechanically analyze (MLB Design III) appropriate portions of the recommended piping systems to establish if any critical mechanical natural frequencies are coinciding with predicted pulsation frequencies as determined by the acoustical simulation.
  5. Provide a final report (for MLB Designs IIb & IIIb) including sufficient data to define the acoustical and mechanical characteristics of the recommended piping system.

An acoustical analysis normally requires approximately one (1) to (2) weeks to complete depending primarily on the number of compression stages. Usually the pre-simulation design (if required to order long delivery items) can emailed for review/comments within one (1) to two (2) days into the study. The final portion of the mechanical analysis for an API 618 Design Approach 3 will be completed when layout drawings incorporating the results of the acoustical analysis with pipe supports located are received.
MLB Design Procedures
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