Metric Hydraulic Fittings

Metric hydraulic fittings are key hydraulic components used in hydraulic systems to connect piping, valves, actuators (e.g., cylinders, motors) and other components, and their dimensions and thread specifications follow the Metric system (Metric) standard, which is widely used in Europe, Asia, and the global standardization of demanding industrial fields. Compared with the imperial (such as SAE, NPT) fittings, metric fittings in millimeters (mm), with uniform thread parameters and sealing form, suitable for high-pressure, high-precision needs of the hydraulic system.

Core features of metric hydraulic fittings

1. Standardized design
Conforms to international standards (e.g. ISO 6149, ISO 8434) to ensure global universality.
– Thread type: Common metric threads include M thread (metric common thread) and metric taper thread (e.g. ISO 228-1).
– Seal forms: metal-to-metal seals, O-rings (e.g. ISO 1179) or flat seals (e.g. flange joints) are mostly used.

2. High pressure resistance
The working pressure ranges from 16MPa to 63MPa, and some high-pressure models can reach over 100MPa.

3. Material and Process
Material: carbon steel, stainless steel (e.g. 304/316), brass, etc., with high corrosion resistance.
Surface treatment: zinc plating, nickel plating, phosphating, etc., to enhance durability.

the main types of metric hydraulic fittings

1. Metric threaded fittings (M series)
– Straight thread fittings: direct screwing connection through the thread, need to be matched with gasket or O-ring.
– Tapered thread fittings (e.g. ISO 8434-1): self-sealing using tapered threads, suitable for medium and high pressure systems.

2. ferrule fittings (DIN 2353)
– It consists of fitting body, ferrule and nut, sealing is realized by pressing the pipeline through the ferrule, widely used in industrial equipments.

3. Flanged fittings
– The flange is fixed by bolts, suitable for high flow and high pressure system (such as hydraulic pipeline of construction machinery).

4. Quick-change couplings (ISO 16028)
– Allow rapid connection/disconnection, reduce fluid leakage, commonly used in applications requiring frequent disassembly.

5. Transition fittings
– Used for conversion between metric and imperial systems (e.g. M → NPT), to solve the compatibility problem of different standard interfaces.

metric hydraulic fittings international standards and specifications

1. ISO 6149: Standard for metric threaded ports and fittings, covering thread dimensions, sealing forms and test methods.
2. ISO 8434-1: 24° taper fitting (metric ferrule type) standard for high pressure systems.
3. DIN 2353: German Industrial Standard defining dimensional and performance requirements for ferrule fittings.
4.JIS B2351: Japanese Industrial Standard, similar to DIN 2353 but some parameters are different.

Metric 24° Taper Fitting Connection

Metric Hydraulic Fitting Size Chart

DIN 2353

Metric Hydraulic Fittings Price List by Size

Metric hydraulic fittings purchasing selection guide

1. Pressure level: select according to the maximum working pressure of the system (e.g. 25MPa, 40MPa). 2.
2. Temperature range: high temperature environment needs to choose stainless steel or special coating material.
3. Fluid compatibility: oil, water-based media or chemicals need to match the sealing material (such as NBR, FKM rubber).
4. Size matching: Confirm the pipeline outer diameter (OD) and thread specifications (such as M12 × 1.5, M16 × 1.5).
5. Installation space: Compact space can choose right angle or compact fittings.

Metric hydraulic fittings installation and maintenance points

1. Installation steps
– Clean the pipelines and fittings to avoid impurities into the system.
– For ferrule fittings, tighten the nut according to the standard torque to ensure the sealing of ferrule deformation.
– When using thread sealant or raw material tape, avoid blocking the flow path.

2. Common Problems
– Leakage: mostly due to damaged seals or untightened threads.
– Damaged threads: installation is not aligned, resulting in “misalignment”.
– Pressure drop: Improper fitting selection or internal clogging.

Metric Hydraulic Fittings Sourcing Summary

Metric hydraulic fittings have become a core component of modern hydraulic systems due to their standardization and high reliability. Correct selection and installation can significantly improve the efficiency and life of the system, and with the development of industrial intelligence, its design and function will continue to be optimized to meet the higher demand.

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