Views: 0 Author: Ruihua Hardware Publish Time: 2026-09-02 Origin: Ruihua Hardware
Hydraulic fittings may look similar from the outside, but small differences in thread form, sealing surface and connection geometry determine whether two components can work together safely. Selecting a fitting by diameter alone can result in leakage, damaged threads or an assembly that appears tight but cannot maintain a reliable seal.
This guide explains the main hydraulic fitting types, how they seal and what information buyers should check before ordering. It covers common JIC, ORFS, NPT, BSP, metric and flange connections, as well as adapters, hose fittings and tube fittings.
Important: A fitting should be identified from its applicable standard, thread profile, dimensions and sealing method. A photograph or approximate outside diameter is useful for screening, but it is not enough for final specification.
A hydraulic fitting connects hoses, tubes, pipes, valves, cylinders and other components in a fluid power system. Depending on its design, a fitting may:
join two connections of the same type;
adapt one thread or sealing system to another;
change the direction of a line;
divide or combine flow;
pass through a panel;
terminate a port; or
provide a detachable hose or tube connection.
The term hydraulic fitting therefore describes a broad product family. The most useful way to understand it is to separate fittings by function, connection standard and sealing method.
Straight adapters connect two ports in the same flow direction. They may join identical ends or convert between different standards, such as a metric tube connection and a BSP port.
Reducing adapters have different sizes at the two ends. When selecting one, check both connection specifications rather than describing it only by the larger size.
Typical uses: pumps, valve blocks, cylinders, test equipment and transitions between imported and locally sourced components.
Elbows redirect the hydraulic line, commonly through 45 or 90 degrees. They are useful where a straight hose bend would consume too much space or place unnecessary stress near the connection.
Some elbows have a fixed orientation. Adjustable stud elbows can be positioned before final tightening, but their sealing method and installation procedure must be followed correctly.
Typical uses: compact machinery, cylinder ports, mobile equipment and installations with limited hose-routing space.
Tee fittings connect three flow paths, while cross fittings connect four. They can have equal-size ends or include reducing and mixed-thread combinations.
Because branch connections affect system layout and flow, the port orientation and end specification should be shown clearly on the drawing or order list.
Bulkhead fittings pass a hydraulic connection through a panel, frame or enclosure. A locknut secures the fitting at the mounting surface.
Selection should account for panel thickness, available thread engagement, orientation and access for tightening.
Plugs close female ports; caps close male ends. They may be used as permanent closures, temporary protection or service points.
The closure must match both the thread and the sealing system. A thread that screws into the port is not automatically a compatible pressure seal.
Hydraulic hose fittings connect a hose to another hose or to a component port. A typical crimp fitting includes a connection end, a stem or insert, and a ferrule selected for the hose construction.
Hose fittings must be matched as a system. Hose type, inside diameter, reinforcement, fitting series, ferrule, crimp diameter and assembly procedure all matter. Mixing unverified hose and fitting components can lead to premature failure.
Flange connections are widely used for larger line sizes, high flow rates and demanding hydraulic service. A flange head is clamped to the port, with an O-ring forming the seal.
The flange series, nominal size, pressure class, bolt pattern, flange-head dimensions and O-ring details must all agree with the mating component.
JIC connections use a 37-degree flared sealing surface and straight UN/UNF threads. The threads provide clamping force; the metal flare surfaces form the primary seal.
JIC fittings are common in mobile equipment, industrial hydraulics and many North American systems. They are valued for availability and serviceability, but the flare must be clean and correctly aligned. Over-tightening cannot repair a damaged sealing surface.
Identification clues: straight thread, visible 37-degree cone or flare seat, and inch-based thread dimensions.
ORFS fittings seal with an O-ring located in a groove on the flat face of the male connection. The mating face compresses the O-ring when the nut is tightened.
This design is commonly selected where strong leak control and resistance to vibration are priorities. The sealing face must remain clean and the O-ring material must be compatible with the fluid and operating temperature.
Identification clues: flat face, visible face-seal O-ring and straight UN/UNF thread.
ORB stud ends use a straight thread and an O-ring near the base of the male thread. The O-ring seals in a machined port rather than on a flare.
Adjustable ORB fittings may include a locknut and backup washer that allow the fitting to be oriented before final tightening.
Identification clues: straight thread and an O-ring positioned at the port end of the male fitting.
NPT and NPTF connections use tapered threads. The thread flanks engage more tightly as the fitting is installed. Depending on the specification and application, an approved sealant may also be required.
NPT and NPTF should not be identified from nominal size alone, and they should not be confused with BSP tapered threads. Similar-looking tapered threads can have different thread angles, pitches and profiles.
Identification clues: visibly tapered male thread and an inch-based thread pitch. Confirm with a thread gauge and the applicable standard.
BSPP connections use parallel British Standard Pipe threads. Because the threads are parallel, the pressure seal is normally created by a separate feature, such as a bonded seal, O-ring, retaining ring or metal sealing face.
The exact seal depends on the port and fitting design. Calling a fitting simply “BSP” is therefore incomplete; buyers should specify whether the thread is parallel or tapered and how the joint seals.
BSPT connections use tapered British Standard Pipe threads. They are not interchangeable with NPT solely because both are tapered. The thread form and pitch must be checked.
Identification clues: tapered profile and BSP thread pitch. Use gauges rather than visual comparison for final confirmation.
Metric 24-degree cone systems are common in industrial and mobile hydraulics. Depending on the design, the connection may seal through a cutting ring, a formed tube end, an O-ring-assisted cone or another specified arrangement.
Metric tube fittings are often organized into light and heavy series. Tube outside diameter, thread size, series and sealing components must be considered together.
Identification clues: metric thread, 24-degree internal cone and a tube-size relationship defined by the relevant standard.
Not all metric threads indicate a 24-degree cone connection. Metric threads are also used with bonded seals, port O-rings, flat faces and specialized tube systems.
For this reason, the thread designation must always be paired with a description or drawing of the sealing face.
SAE-style flange connections use a flange head, O-ring, clamps and bolts. Code 61 and Code 62 are common series, but they have different dimensional and pressure-related requirements and must not be substituted without verification.
The mating port, flange head and clamp set should be specified as a complete connection.
Understanding the sealing method is more important than simply recognizing the thread.
JIC flares and some cone connections seal when two accurately machined metal surfaces meet. Scratches, incorrect angles, contamination and misalignment can prevent a reliable seal.
ORFS, ORB, flange and some metric connections use an elastomeric O-ring. Check the O-ring size, material, hardness where specified, installation position and compatibility with the hydraulic fluid and temperature.
Some parallel-thread ports seal against a washer or bonded seal beneath the fitting shoulder. The port spotface and washer condition are part of the sealing system.
NPT, NPTF and BSPT rely on controlled engagement of tapered threads. Thread damage, incompatible profiles and incorrect installation can cause leakage or damage to the female port.
JIC and ORFS connections both use straight inch threads, but their sealing methods are visibly different.
Feature |
JIC 37° Flare |
ORFS |
|---|---|---|
Primary seal |
Metal flare surfaces |
O-ring on a flat face |
Sealing face |
37-degree cone/flare |
Flat face with O-ring groove |
Common advantage |
Widely available and serviceable |
Strong leak control in vibration-prone systems |
Inspection focus |
Flare angle, scratches and alignment |
O-ring condition, groove and face cleanliness |
Interchangeable? |
No |
No |
The thread alone is not enough to distinguish them. Always inspect the sealing end.
Use a structured process instead of guessing from appearance.
Measure the male thread diameter near the first and last full thread. A meaningful change may indicate a tapered thread. Confirm with the relevant gauge or standard.
Use a caliper on the male outside diameter or the female inside diameter. This measurement is a clue, not the nominal size by itself.
Use metric and inch thread-pitch gauges. Several families have similar diameters but different pitches.
Look for a 37-degree flare, 24-degree cone, flat face, face O-ring, port O-ring, bonded-seal shoulder or tapered-thread sealing area.
For tube fittings, measure the tube outside diameter. For hose fittings, identify the hose size and construction. Connection size and hose or tube size are separate order parameters.
Use a fitting chart, manufacturer drawing or applicable standard to confirm the identification. When dimensions remain uncertain, send a sample or a dimensioned sketch to the supplier.
Specify the complete connection at both ends: thread designation, size, sealing surface and any required seal.
Pressure, temperature, fluid type, vibration, impulse cycles and external environment can affect the suitable material, sealing method and product series. The system designer should confirm the final rating of the complete assembly.
Carbon steel is widely used for hydraulic fittings, often with a protective surface finish. Stainless steel may be selected for corrosion resistance or particular operating environments. Other materials may be required for specialized systems.
Material selection should consider both mechanical requirements and compatibility with the fluid and surrounding environment.
Straight, elbow, tee, bulkhead and adjustable designs solve different routing problems. Allow space for tools, hose movement and future maintenance.
For crimped hose assemblies, confirm the hose specification, fitting stem, ferrule and crimp data together. Do not assume that visually similar components from different systems are compatible.
Threads and sealing faces should be protected during transport and storage. Cleanliness requirements should be agreed for applications where contamination control is important.
Ordering from a photograph without confirming dimensions.
Using the outside thread diameter as the nominal size.
Describing a connection as only “metric” or “BSP.”
Confusing NPT with BSPT.
Matching the thread but overlooking the sealing face.
Reusing a damaged O-ring or sealing washer.
Mixing hose, fitting and ferrule components without validated assembly data.
Assuming Code 61 and Code 62 flange components are interchangeable.
Applying extra tightening force to compensate for damaged or incompatible parts.
For an efficient technical review, provide:
drawing, standard number or existing part number;
connection type and size at each end;
sealing method;
hose inside diameter or tube outside diameter;
straight, elbow, tee, bulkhead or flange configuration;
material and surface-finish requirement;
working fluid, pressure and temperature where relevant;
required quantity;
inspection, marking, cleanliness and packing requirements; and
a sample or clear dimensioned photographs for unidentified parts.
Ruihua Hardware supplies hydraulic adapters, hose fittings and related connection components in multiple standards and configurations. For product matching, send the full connection details rather than a general fitting name. You can also review our hydraulic adapters, hydraulic hose fittings and stainless steel hydraulic fittings.
For additional reference, see our hydraulic fitting catalog, hydraulic fitting chart and metric hydraulic hose fitting guide.
Common families include JIC 37-degree flare, ORFS, ORB, NPT/NPTF, BSPP, BSPT, metric 24-degree cone and SAE flange connections. Straight adapters, elbows, tees, bulkheads, hose fittings, plugs and caps describe the fitting's function or shape.
“SAE fitting” is a broad description and may refer to different SAE-standardized connections. JIC normally refers specifically to a 37-degree flare connection with straight UN/UNF threads. Confirm the exact standard and sealing surface.
They should not be treated as interchangeable. Although BSPT and NPT are both tapered systems, their thread forms and pitches can differ. Use a correctly specified adapter when two systems must be joined.
Measure both the thread diameter and pitch, then inspect the sealing surface. Diameter alone is unreliable because different thread families can be close in size.
There is no single best fitting for every system. Reliability depends on the connection design, operating conditions, installation, component quality and maintenance. ORFS is often chosen for demanding leak-control applications, while correctly selected and assembled flare, cone, O-ring and flange systems can also provide reliable service.
Ruihua Hardware can review a drawing, standard, part number, sample or dimensioned photographs. Final identification requires enough information to confirm the thread, size and sealing method.
The safest way to specify a hydraulic fitting is to describe the complete connection. Thread family, dimensions, sealing surface, material and operating conditions all affect compatibility.
If you are comparing JIC, ORFS, BSP, NPT, metric or flange fittings, send Ruihua Hardware your drawings or fitting list. Our team can review the requested connection details and help organize suitable standard or custom configurations for quotation.
