ISO 5781-2016 PDF

Full title and description

Hydraulic fluid power — Pressure-reducing valves, sequence valves, unloading valves, throttle valves and check valves — Mounting surfaces (ISO 5781:2016). This International Standard specifies the dimensions and related data for mounting surfaces used with the listed valve types to ensure mechanical interchangeability across manufacturers and equipment.

Abstract

ISO 5781:2016 defines the geometry, port locations, fixing-hole patterns, tolerances and surfacequality requirements for mounting surfaces of pressure-reducing, sequence, unloading, throttle and check valves used in hydraulic fluid-power systems. The standard provides figures and tables for several main-port size families and includes code identification conventions (reference to ISO 5783) and normative references (for example ISO 1219-1 and ISO 3601-2) to support interchangeability in industrial equipment.

General information

• Status: Published (3rd edition, confirmed).
• Publication date: August 2016 (ISO 5781:2016).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 23.100.50 (Hydraulic fluid power / Control components).
• Edition / version: Edition 3 (2016).
• Number of pages: 24 pages.

Additional authoritative details (confirmation status and committee): the standard was reviewed and confirmed in 2021 and is maintained by ISO/TC 131 (subcommittee SC 5).

Scope

Specifies dimensions and related data for mounting surfaces of hydraulic pressure-reducing, sequence, unloading, throttle and check valves so that valves and mating subplates/manifolds are mechanically interchangeable. It applies to mounting surfaces that represent current industry practice and are generally applicable to industrial hydraulic equipment; specific mounting patterns and tables are provided for several main-port diameter families.

Key topics and requirements

• Standardized mounting-surface geometries and port layouts for valve interchangeability (figures and tables for main-port diameter groups: e.g., ≈4.5 mm, 7.5 mm, 14.7 mm and 23.4 mm families).
• Dimensional tolerances and position tolerances — examples: locating pin holes tolerance H12; position tolerances relative to origin: pin holes ±0.1 mm, screw holes ±0.1 mm, main ports ±0.2 mm.
• Surface requirements — surface flatness (0.01 mm over 100 mm) and surface-roughness references (normative reference to ISO 3601-2).
• Identification and coding of mounting patterns — code system defined by ISO 5783 (used for marking/identification).
• Figures and tables giving fixing-hole sizes, thread recommendations, corner radii, locating-pin arrangements and port callouts to support manifold/subplate design and manufacture.
• Notes on modular configurations and references to other ISO standards where alternate modular mounting conventions apply (see related standards such as ISO 4401 for certain modular stack valves).

Typical use and users

Used by hydraulic valve designers, manifold and subplate manufacturers, OEM product engineers, system integrators, maintenance and service engineers, and certification/standards personnel to ensure mechanical compatibility of valves and manifolds, reduce redesign effort, and simplify spare-parts interchange. It is commonly consulted during product design, procurement specifications and manufacturing of hydraulic control blocks and valve subplates.

Related standards

Commonly referenced and complementary standards include: ISO 5783 (code system for valve mounting identification), ISO 1219-1 (graphical symbols and circuit diagrams), ISO 3601-2 (surface and sealing references), ISO 4401 (modular stack valve mounting), and other ISO/TC 131 series standards that cover valve and mounting conventions for hydraulic components.

Keywords

mounting surfaces, hydraulic valves, pressure-reducing valve, sequence valve, unloading valve, throttle valve, check valve, interchangeability, port dimensions, subplate, manifold, ISO 5781:2016, ISO/TC 131/SC 5

FAQ

Q: What is this standard?

A: ISO 5781:2016 is an international standard that specifies dimensions and related data for mounting surfaces used with specific hydraulic valves to ensure mechanical interchangeability across manufacturers.

Q: What does it cover?

A: It covers mounting-surface geometry, port and fixing-hole layouts, tolerances, surface-quality requirements, and identification/coding conventions (codes per ISO 5783), with figures and tables for several main-port size families.

Q: Who typically uses it?

A: Valve and manifold/subplate designers, hydraulic OEMs, system integrators, maintenance engineers and procurement/specification writers who need guaranteed mechanical compatibility of hydraulic control components.

Q: Is it current or superseded?

A: ISO 5781:2016 is the 3rd edition (published August 2016). The edition was reviewed and confirmed in 2021 and remains the current published version. It replaced earlier editions (for example the 2000 edition).

Q: Is it part of a series?

A: Yes. It forms part of the ISO/TC 131 suite of fluid-power standards addressing valves, mounting surfaces and related conventions. It is used alongside related documents such as ISO 5783 (coding), ISO 1219-1 (symbols), ISO 4401 (modular mounting) and other TC 131 publications.

Q: What are the key keywords?

A: Mounting surfaces; hydraulic valves; interchangeability; port layout; fixing-hole pattern; surface flatness; tolerances; ISO 5781:2016.