Overview
ISO 8927:1991 - Earth‑moving machinery - Machine availability - Vocabulary defines a standardized vocabulary to describe the availability of earth‑moving machinery (as defined in ISO 6165). The standard provides clear, bilingual (English/French) terms and definitions to improve communication between manufacturers, operators, maintenance teams and procurement specialists. It groups terminology and gives an informative Annex A that clarifies relationships between terms.
Key topics
The standard organizes terms into logical categories and provides commonly used availability metrics and relationships:
- Availability terms
- Availability: probability that a repairable item is operable when required.
- Instantaneous availability: probability an item functions at a specified moment.
- Mean availability: ratio of accumulated operating time to total possible operating time.
- Formulas shown in the standard include inherent and operational availability, for example:
- Inherent availability Ai = MTBF / (MTBF + MTTR)
- Operational availability Ao = MUT / (MUT + MDT)
- Reliability terms
- Reliability, inherent reliability, operational reliability (including a condition factor relating operational to inherent reliability).
- Failure terms
- Failure, failure mode, early (warranty) failure, random failure, wear‑out failure, sudden failure.
- Classifications such as primary/secondary, single‑cause/combined‑cause, misuse failure, inherent weakness failure.
- Serviceability terms
- Serviceability, maintainability, repairability, accessibility, repairable item, storage‑ability.
- Time terms
- Key time metrics used in availability assessment (e.g., MTBF, MTTR, mean up time, mean down time).
Practical applications and users
ISO 8927 is practical for anyone involved in the lifecycle of earth‑moving equipment:
- Equipment manufacturers and design engineers - to use consistent availability and reliability vocabulary in specifications and testing.
- Fleet managers and contractors - to interpret maintenance records and availability metrics for operational planning.
- Maintenance planners and reliability engineers - to standardize reporting, root‑cause analysis and maintainability assessment.
- Procurement and contract authors - to write clear service level agreements (SLAs), warranty clauses and availability requirements.
Using ISO 8927 improves clarity in specifications, performance reporting, failure analysis and helps align teams on metrics such as MTBF, MTTR, inherent availability and operational availability.
Related standards
- ISO 6165:1987 - Earth‑moving machinery - Basic types - Vocabulary (normative reference cited by ISO 8927).