Reciprocating Compressor - Pulsation, Design Approach, API 618

Pulsation Study for Reciprocating Compressor

The pulsation study for reciprocating compressor could be performed as per API 618, and INERTANCE has a capability to perform below kinds of acoustic analysis , shaking force estimation and mechanical study as per Design approach procedure.

Pipe Mechanical Analysis, Surge Volume — [ Pipe Mechanical Analysis ]

Pulsation Study as per API 618
Pulsation Suppression Device
Surge Bottle Sizing as per API 618 & API 11P
Shaking Force (Unbalanced Forces)
Acoustic Simulation
Calculation of Peak-to-Peak Amplitude Levels
Piping Vibration Criteria
Piping Modification
Mechanical Review and Piping Restraint Analysis
Mechanical Study for Natural Frequency
Separation Margin Requirements
Acoustic Controls by Orifice
Acoustic Resonance
Acceleration Head
Surge Volume and Acoustic Filter
Helmholtz Frequency Estimation

The objective to perform this study is to avoid problems with vibration, performance, reliability, and flow measuring error caused by acoustical interaction between the compressor and the relevant piping system.
Pulsation study procedure has been determined as per API 618 guideline.

Here, INERTANCE shows the brief procedure for related study of reciprocating compressor as follows;

Pulsation Study : Design Approach 1

Design Approach 1 is to perform the empirical pulsation suppression device design using proprietary and empirical analytical techniques to meet line side pulsation levels and the maximum pressure drop based on compressor normal operating condition.

Design Approach 2

Design Approach 2 is to perform the acoustic simulation and piping restraint analysis, which include the control design through the use of pulsation suppression devices and proven acoustic techniques. In case the detail design of piping system is finalized, the acoustic simulation has to be performed for system reliability. Then, the separation margin based on mechanical natural frequency has to be checked to avoid the mechanical resonance.

Pulsation study : Design Approach II as per API 618 — Design Approach II as per API 618

Design Approach 3, API 618

Design Approach 3 is to perform the mechanical analysis with forced mechanical response analysis in addition to Acoustic study. The forced mechanical response analysis for compressor cylinder as well as associated piping systems has to be performed as results of previous analysis results.

INERTANCE has a capability to select the sizing of surge volume as well as low pass filter, and the related pipe support design, where necessary.

Pulsation control, Vibration — Pulsation Controls for Reciprocating Compressor

Mechanical Study of piping system, Shaking Force — [ Mechanical Study of piping system ]

Recent Project – Pulsation Study of reciprocaitng compressor

INERTANCE recently performed a pulsation analysis of a reciprocating compressor.

These three (3) stage reciprocating compressors has been running for 25 years, since these compressors had been initially commissioned after construction. With consideration of improved process demand, it was necessary to revamp the process and pipe condition for these compressors, and this was due to perform new pulsation study. This pulsation study was performed as per Design Approach 3 procedure in accordance with API 618, API 688, and this page shares the analysis status of Design approach 2.

Scope of this analysis

The scope of service for this pulsation study as Design approach 2 below activities;

Review for Existing Pulsation Study
Acoustic Modeling
Vibration Site Survey
Case Study as per Cylinder Phase Difference
Design Approach 1, Surge Volume Sizing as per API 618
Design Approach 2 for Acoustic Simulation
Pulsation Limit & Criteria Assessment
Pressure Drop by Surge Volume and Orifice

Pulsation for Existing condition

Pulsation study for existing condition was carried out, so that we can confirm if there is no design issue with high pulsation amplitude.

peak peak pulsation level — [Peak-Peak Pulsation Level]

Site Vibration Survey

Vibration survey and measurement was done at Site, and INERTANCE engineers checked if there was no high vibration issue for piping system with existing condition. And, the measured vibration levels were compared with related vibration criteria such as EFRC (European Forum for Reciprocating Compressors), ISO 10816-8 and Wachel chart, etc.

Measurement for pipe vibration
Vibration check for Crank case, Cylinder flange, Pulsation bottle, Piping system, etc.
Assessment for vibration criteria listed in below
EFRC (European Forum for Reciprocating Compressors)
ISO 10816-8
Wachel chart

Vibration for Piping System, Shaking Force, orifice — [ Wachel chart ]

Case Study

When these compressors are to be operated in conjunction with other compressor units and their associated piping system, the additive effect of pressure pulsations from multiple units shall be addressed. It was planned to run these compressors with parallel operation, hence, Case study was necessary to find out the worst case scenario as per each compressor cylinder phase difference.

Possible operation case to be checked
Step operation for reciprocating compressor (25%, 50%, 75%, 100%)
Single acting (SA) and Double acting (DA) operation
Cylinder phase difference for parallel operation
Multiple unit additive effects
Start-up operation with Nitrogen gas

Pulsation Amplitude

Design approach 2 was to perform the acoustic simulation and piping restraint analysis, which include the pulsation control design via the use of pulsation suppression devices and proven acoustic techniques.

Pulsation control device design
Surge volume, Pulsation bottle, Pulsation suppression device
Orifice at compressor cylinder flange
Pipe support span table for separation margin
Pulsation induced shaking force
Shaking force assessment and criteria by API 618
Pulsation at cylinder flange, Surge volume and piping system

Reciprocating Compressor
Pulsation
Acoustic
API 618, API 688
Vibration measurement, survey
Surge Volume, Orifice
Shaking Force
Vibration

INERTANCE has a capability regarding noise and vibration engineering, and our experts are familiar with assessment of API 618 study & Mechanical study. For further information, contact us at (mountain@inertance.com).

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