API St 670-2025 PDF

Full title and description

St API St 670-2025 — Machinery Protection Systems. Specifies minimum requirements for machinery protection and monitoring systems used on rotating and reciprocating machinery, including vibration, axial position, overspeed and temperature monitoring, plus requirements for hardware, installation, documentation and testing.

Abstract

This standard (API Std 670:2025) establishes functional and performance requirements, sensor and monitor characteristics, recommended installation practices, test procedures, and required documentation for machinery protection systems (MPS) used to detect hazardous conditions and initiate alarms or trips. It updates previous editions to reflect current practice for vibration, shaft position, speed, phase/crank reference, temperature monitoring, and mandatory datasheets.

General information

• Status: Active.
• Publication date: July 2025 (Sixth edition, published 2025).
• Publisher: American Petroleum Institute (API).
• ICS / categories: 17.160 — Vibrations, shock and vibration measurements / Condition monitoring and diagnostics of machines.
• Edition / version: Sixth edition (API STD 670: 2025).
• Number of pages: 225 pages.

Scope

Specifies minimum requirements for machinery protection systems (MPS) that monitor radial shaft vibration, casing vibration, shaft axial position, shaft rotational speed and overspeed, crosshead and piston-rod motion, phase and crank-angle reference signals, surge detection on compressors, and critical machine temperatures (bearing metal, motor windings). The standard addresses transducer and monitor hardware, installation practices, required datasheets, documentation, verification and testing procedures, and alarm/trip logic for safeguarding critical rotating and reciprocating equipment.

Key topics and requirements

• Measurement points and sensor types: radial probes, proximity probes, accelerometers, temperature sensors, keyphasor/phase sensors.
• Performance and accuracy requirements for transducers and monitor channels, including ranges, resolution and failure detection.
• Alarm and trip setpoint definitions, automatic alarm suppression during startup/shutdown and testing, and fail-safe behavior.
• Overspeed and speed-sensing requirements, including independent overspeed protection where required.
• Installation and wiring practices: mounting, cable routing, grounding and isolation to minimise noise and ensure signal integrity.
• Documentation and mandatory datasheets (standard includes standardized datasheet templates to accompany the MPS).
• Factory and site acceptance testing, commissioning checks, periodic testing and maintenance recommendations.
• Requirements for interfaces to control and protection systems, HMI requirements and diagnostic outputs.

Typical use and users

Applied by rotating-equipment engineers, reliability and maintenance teams, control and instrumentation engineers, OEMs and suppliers of machine protection/condition monitoring systems, and procurement/specification authors in oil & gas refineries, petrochemical plants, power plants and other industries with critical rotating machinery.

Related standards

Commonly referenced with other rotating-equipment and condition-monitoring standards such as API 610 (centrifugal pumps), API 614 (lubrication, control and seal systems), ISO 10816 (vibration severity evaluation) and ISO 17359 / ISO TC 108 documents on condition monitoring and diagnostics. These related documents provide complementary guidance on vibration measurement locations, severity zones, and diagnostic practices.

Keywords

machinery protection, MPS, API STD 670, vibration monitoring, shaft position, overspeed, bearing temperature, transducers, proximity probes, keyphasor, commissioning, datasheet, condition monitoring.

FAQ

Q: What is this standard?

A: API Std 670:2025 (published as St API St 670-2025 in some catalogs) is the American Petroleum Institute standard that defines minimum requirements for machinery protection systems used to monitor and protect rotating and reciprocating machinery.

Q: What does it cover?

A: It covers required sensor types and locations, performance and failure-detection requirements for monitors, alarm and trip logic (including overspeed), installation and wiring practices, mandatory datasheets and documentation, and testing/commissioning procedures for MPS.

Q: Who typically uses it?

A: Reliability, rotating-equipment and instrumentation engineers; OEMs and suppliers of monitoring systems; maintenance and operations teams; and procurement/specification writers in oil & gas, petrochemical, power generation and other industries with critical rotating machinery.

Q: Is it current or superseded?

A: Current and active. The 2025 sixth edition supersedes earlier editions (for example the 2014 edition) and is the authoritative edition as of its July 2025 publication.

Q: Is it part of a series?

A: It is part of API's family of rotating-equipment and machinery-related standards and is often used alongside other API and ISO standards for pumps, compressors and condition monitoring (for example API 610, API 614 and ISO vibration/condition-monitoring standards).

Q: What are the key keywords?

A: Machinery protection, vibration monitoring, shaft position, overspeed, bearing temperature, transducer, keyphasor, MPS, commissioning, datasheets.