API 688 was introduced as a companion standard to API 618, covering pulsation and vibration control for all positive displacement machinery — not just reciprocating compressors. Understanding the relationship between the two standards and when each applies is increasingly important as positive displacement machinery in non-compressor applications becomes more common.
API 618 Scope
API 618 applies specifically to reciprocating compressors for petroleum, chemical, and gas industry services. Its pulsation analysis requirements — Design Approaches 1, 2, and 3 — are the industry standard for gas compression applications.
API 688 Scope
API 688 covers pulsation and vibration control in positive displacement machinery systems more broadly, including reciprocating pumps, screw compressors, and other positive displacement equipment. It provides general principles and methodology that can be applied to equipment types not explicitly covered by API 618.
For reciprocating compressors, API 618 remains the primary standard. API 688 provides supplementary guidance but does not replace API 618 for gas compression applications.
For reciprocating pumps, API 674 provides specific requirements for pulsation control. API 688 provides supplementary methodology.
The Practical Implication
When a project involves multiple types of positive displacement machinery — for example, a gas processing facility with both reciprocating compressors and high-pressure pump systems — API 618 governs the compressor analysis and API 674 governs the pump analysis. API 688 provides the unifying framework.
The practical implication for analysis scope and documentation is that the applicable standard should be explicitly identified at the start of each analysis, along with the specific edition and any project-specific deviations.
