The standard provides comprehensive guidelines on preventing catastrophic mechanical failures, piping fatigue, and structural damage caused by the intense pressure pulsations and mechanical vibrations inherent to positive displacement machinery (primarily reciprocating compressors).
Positive displacement (PD) machines, by their nature, do not produce a continuous, steady flow of gas. Instead, they operate via cyclical, pulsating flows that can aggressively excite piping systems and mechanical components. If left unmanaged, these acoustic pulsations and mechanical vibrations lead to high-cycle fatigue, weld failures, and severe gas leaks.
: Installed at strategic piping junctions to create acoustic resistance and break up standing waves.
: Clarifies how high-frequency pulsations can distort flow measurement devices. api 688 pdf
Volumetric vessels placed close to the cylinder nozzles to absorb pressure surges.
Acoustic simulation. This requires digital or analog modeling of the piping system to predict pulsation levels and shaking forces, ensuring they fall within API-specified allowable limits.
Strategically sized restrictions placed in the flow path to introduce acoustic resistance and dampen pressure waves. The Relationship Between API 618 and API 688 If left unmanaged, these acoustic pulsations and mechanical
API 688 provides the critical engineering framework for controlling pulsation and vibration in positive displacement piping systems. Mechanical engineers, piping designers, and plant operators use this document to prevent catastrophic fatigue failures. What is API 688?
| | Consequences | |--------------------------------|------------------| | Missing pages or poor scan quality | Incorrect design limits | | Old draft version | Fails audit; rework required | | Hidden malware or ransomware | Company data breach | | No access to future revisions | Perpetual noncompliance |
: Mandatory for high-pressure, high-horsepower critical assets. Volumetric vessels placed close to the cylinder nozzles
: Required for medium-risk systems with varying gas compositions or wide speed ranges.
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