What are the types of commonly used hydraulic joints in hydraulic systems?

1、 Classify by connection method (this is the most core classification method)

1. Threaded connection joint

This is a common connection method that achieves sealing and connection by tightening internal and external threads.

Metric Thread: such as M14 × 1.5, M18 × 1.5, etc., are very common in domestic and European equipment.

Inch Thread:

NPT (National Pipe Tapered): American standard tapered pipe thread, sealed by the taper of the thread, usually requires the use of raw tape or sealant.

BSP(British Standard Pipe):

BSPT (British Standard Pipe Tapped): British Standard taper pipe thread, similar to NPT.

BSPP (British Standard Pipe Parallel): British standard straight pipe thread (cylindrical thread), sealed on the end face of the joint body by a sealing ring or gasket (such as a combination sealing gasket).

UN/UNF (Unified National/Unified National Fine): American standard thread, straight thread, usually requires an O-ring or metal washer for end face sealing.

2. Flange connection joint

Used for working conditions with large diameter and high pressure, the two flanges are fastened together with bolts, which has good sealing performance and vibration resistance.

SAE Flange: Following the SAE J518 standard, commonly known as "method flange" and "round flange", with specifications such as 4 bolts or 2 bolts.

DIN/ISO flanges: comply with European standards such as DIN 2353, ISO 6162, etc.

3. Card sleeve connector

Composed of a connector body, a sleeve, and a nut. When tightening the nut, the front end of the sleeve bites into the oil pipe, forming a seal, and the rear end plays a role in preventing loosening. Installation requires one-on-one tools and techniques.

Two ferrules: They are quite common and have good sealing and anti loosening effects, such as popular products with good reputation such as Parker and Swagelok.

Single Ferrule:

4. Expansion joint

Expand the end of the pipe into a bell mouth (usually 37 ° or 74 °), and use a nut to press the bell mouth onto the joint body to form a seal. Commonly used in aircraft and low-voltage industrial systems.

37 ° expansion (JIC standard): Joint Industry Council standard, very common in North America.

74 ° expansion (SAE standard): commonly used in low-pressure applications such as automotive braking systems.

45 ° expansion (SAE standard): Another less common standard.

5. O-Ring Face Seal ORFS

The joint end face has an O-ring groove, and during installation, the O-ring is tightened onto another flat end face by tightening the nut or bolt to form a seal. This is currently recognized as one of the connection methods with good sealing effect and ingenious anti vibration technology, widely used in high vibration occasions such as construction machinery.

6. Quick change connector/suitable speed connector

No tools are needed to quickly connect and disconnect the oil circuit, and it can automatically seal when disconnected to prevent oil leakage and contamination. Commonly used in situations that require frequent loading and unloading.

Plug and Socket:

Single valve type: One end has a one-way valve.

Double valve type: There are one-way valves at both ends, and when disconnected, the oil circuits on both sides are automatically closed.

Advection type: Low pressure loss during connection.

2、 Classified by joint structure and function

1. Direct connector/terminal connector

Used for connecting the ends of hoses or steel pipes directly to the ports of valve blocks, oil cylinders, pumps, and other components.

2. Right angle joint/90 ° joint

Change the direction of the fluid to save installation space.

3. Three way connector/four-way connector (T-shaped, X-shaped)

Used for diversion or merging.

4. Variable diameter joint/transition joint

Used to connect oil ports of different diameters or standards.

5. Rotary joint/rotary joint

Allow the pipeline to rotate 360 ° in the connected state to avoid hose twisting.

6. Blockage/blockage

Used to seal unused oil ports.

7. Hat cover

Used to protect unconnected oil ports and prevent contamination.

3、 Classified by the type of connected pipeline

Hard pipe joint: used to connect seamless steel pipes, usually in the form of a sleeve, welded, or flared joint.

Hose connector: used to connect rubber or thermoplastic hoses, usually a detachable crimping type (requiring one-to-one equipment crimping) or a repeatable assembly type.

Transition joint: used to connect hard and soft pipes, or to connect components of different standards.