ISO 3661:1977

Overview

ISO 3661:1977 specifies basic baseplate and installation dimensions for end-suction centrifugal pumps, covering baseplate reference numbers 2 to 9. The standard is intended primarily for pumps manufactured in accordance with ISO 2858 and for installations where pumps are coupled to foot-mounted electric motors and mounted on a foundation. It provides alternative fixing-hole arrangements and guidance to support consistent pump-motor coupling and foundation design.

Key Topics

• Baseplate reference numbers (2–9): The standard defines reference numbers for baseplates and links those numbers to the relevant dimensional data.
• Baseplate and installation dimensions: Figures and tables in the standard give the basic working-surface sizes, mounting-hole locations (A, B, C, D, E) and the installation dimensions used to design foundations and alignment procedures.
• Alternative fixing-hole arrangements: Options for three- or four-hole patterns are described to suit different manufacturer practices and installation constraints.
• Height limits and centre-line considerations: Maximum permissible baseplate heights (hmax, Hmax) are defined to account for packing, centre-line heights of pumps and motors, and installation sub-structures.
• Referenced standards: Clearance hole sizing is aligned with ISO/R 273 and motor frame/flange compatibility is cross-referenced to IEC Publication 72.

Applications

ISO 3661:1977 is practical for engineers, installers and specifiers who need to:

• Ensure interchangeability of end-suction centrifugal pump installations across suppliers.
• Design concrete foundations and baseplate anchor layouts using standardised installation dimensions.
• Select compatible electric motor frames and flange connections when coupling to foot-mounted motors (reference mapping is provided between baseplate numbers and motor frame numbers).
• Accommodate alternative fixing-hole positions to match site constraints or bespoke mounting arrangements.

Typical users include pump manufacturers, OEMs, mechanical engineers, plant installation teams and maintenance personnel who require consistent dimensional data for procurement, site layout and retrofit projects.

Related Standards

• ISO 2858 - End-suction centrifugal pumps: designation, duty point and nominal dimensions (primary pump dimensional reference used with ISO 3661).
• ISO/R 273 - Clearance holes for metric bolts (used for clearance hole specification in baseplates).
• IEC Publication 72 - Dimensions and ratings for rotating electrical machines (referenced for motor frame and flange compatibility).

By applying ISO 3661:1977, organizations achieve reliable pump-motor alignment, reduced installation errors, and faster equipment interchangeability while ensuring that baseplate and foundation designs adhere to internationally recognised dimensional practices.