13 Hydraulic Fittings You Should Know

Hydraulic fittings connect hose, pipe and tube to components such as hydraulic manifolds, cylinders, various components or other hoses- you already knew that, otherwise you wouldn&#;t be on this blog! BUT did you know the different types and applications of hydraulic and certain pneumatic fittings?

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1. NPT (National Pipe Taper) and NPS (Nominal Pipe Size) fitting thread are at a 60° angle and have flattened crests and roots. Having been around for over 100 years, this pipe thread style is one of the most popular in North America. NPT male threads mate with the female to create a mechanical wedge essentially crushing the threads together. NPT fittings are commonly used in construction, agricultural and industrial equipment as well as plumbing and automotive applications.

2. JIC (Joint Industry Council) SAE J514 fittings are a compression style and often considered the most popular hydraulic fittings in fluid power. Their 37° flare seating surface incorporates straight, parallel threads to form the seal, rather than tapered threads or O-ring use. They can withstand pressures of up to 10,000 PSI and are often used in the aerospace, military and automotive industries as well as in construction, agricultural and other heavy equipment.

3. ORB (O-ring boss), also known as SAE J Straight Thread O-ring Boss fittings, have straight threads and seal using an O-ring located at the base of the male thread on the wrench flats. The O-ring seals between the male and a machined seat in the female port to provide minimum spotface, which is an adequate depth to allow sufficient wrench grip when tightening the fitting. O-ring boss fittings are used in many industries to join hoses, tubes and pipes for fluid transfer. They are frequently used for connection to valves, cylinders and pumps where a leak tight seal is required.

4. ORFS (O-ring Face Seal) SAE J fittings have an O-ring recessed into the face of the fitting and are ideal for hydraulic system leak prevention in vibration and impulse conditions and are capable of handling operating pressures up to 6,000 PSI. ORFS fittings are widely used in off-road, construction, and agricultural equipment which experience high vibration or shock, and are also common in petrochemical and shipbuilding industries.

5. Tube Fittings and Adapters encompass a wide variety of connections referred to in this article, including NPT, JIC and O-Ring Boss fittings. Plus, adapters, caps and plugs that range from applications of connecting hose barb to NPT or JIC SAE 37° reducers and many others.

6. Flanges are typically larger in size, from ½&#; to 2&#; and used to connect pipes, valves, pumps and other system equipment that experience very high pressure and vibration, where the flange is used to connect two pipes. Of the two most common types, SAE Code 61 flanges are used in lower pressure applications requiring between 3,000 and 5,000 PSI, and Code 62 is used in higher pressure applications of up to 6,000 PSI. Comparatively, Caterpillar OEM equipment uses similar 4-bolt flanges of their own, which are NOT interchangeable with SAE flanges- primarily due to their variation in thickness.

6. Instrumentation Fittings, also known as compression fittings, are used in control and process measurement systems, as well as cryogenic applications. They are available in two styles: single or double &#;bite-type&#; ferrules and are used to connect tubing and convey gases or liquid. There are three components: the body, nut, and ferrule; which, when assembled, slide onto the tubing and seat (or &#;bite&#;) into the tube. The nut is turned a specified amount to properly grip the tube to ensure a leak-free connection. The pressure rating of instrumentation fittings is equal to the maximum allowable working pressures of the tubing, withstanding temperatures from cryogenic to very high heat- again dependent on the tubing specification. For more information, check out Essential Instrumentation Content.

8. BSP Fittings (British Standard Pipe) threads are the UK&#;s most popular fitting. JCB, one of the world&#;s largest manufacturers of construction equipment, uses BSP fittings almost exclusively. BSP fittings have their own unique seat and thread angles and are not to be interchanged with other similar style of fittings. BSP male fittings incorporate a conical 30° seat, which mates with the associated 30° conical cone seat female port or fitting. The 55° thread angle of BSP fittings are available in two thread types for differing applications.

• BSPP fittings have parallel threads and seal with an O-ring or bonded washer.
• BSPT fittings have tapered threads that create a metal-to-metal wedge to seal the threads. It&#;s also important to use a thread sealant with BSPT connections.

9. Bite Type Fittings follow the SAE J514 24° inch measurements flareless compression fitting specification and are also available in DIN metric sizes. The fitting body has a 24° tapered throat, where the tightening of the nut presses a ferrule into the tube.

10. Flare-O Fittings incorporate a SAE 37° flare to NPT adapters. Their elastomeric O-ring seal provides a leak free connection and are a perfect drop-in replacement for SAE 37° flared tube fittings. Their exceptionally tight seal is ideal for connecting hose or tubing in high temperature and/or pressure applications.

11. Weld Fittings are used to join components to pipe, hose or other fittings for extra protection against leaks. They are also used when structural integrity or permanent piping connections are required, for ASME pipe applications, as well as where there is conveyance of toxic or flammable liquids, gases or steam.

12. Metric Fittings are the most commonly used around the globe, primarily in Europe and Asia. There are three most frequently used styles, each principally used by different OEMs and in separate regions.

• Metric DIN fittings are the most widely used bite-type fitting globally. The seal is established simply by tightening the nut on the male fitting, wedging the bite sleeve onto the standpipe tube without the need for an O-ring.
• JIS (Japanese Industrial Standard) metric hydraulic fittings are used primarily in Japan and throughout Asia.
• Komatsu, a Japanese multinational OEM that manufactures heavy equipment from construction to military and industrial machinery, uses a specialized metric 30° flare fitting which provides superior performance in their equipment applications.

13. Push to Connect Fittings are normally made of nickel-plated brass or a glass-reinforced thermoplastic. They serve as quick connect and release fittings simply by pushing the collar back and sliding the tube into the fitting. Though they are used in many water and air/pneumatic transmission applications, they are best known for their use as D.O.T. (Department of Transportation) air brake fittings for trucks, buses and other large vehicles. There are many additional applications too, such as adapter styles like fractional inch tube to male NPT.

Whatever your application, it&#;s imperative to select the proper components- because your hydraulic system is only as good as the fitting!

SOURCE: https://blog.brennaninc.com/13-hydraulic-fittings

Connection Types

British Connections

British Standard Pipe (BSP) and BSPT (tapered) connections are common fitting types in the UK. Sealing takes place via distortion of the threads. Thread sealants are recommended when securing connections; they are most comparable to NPT fittings.

BSPP (parallel) is a parallel thread fitting that uses a bonded ring seal. A captive seal can be made using metal-to-metal angled surfaces or with a combination of metal-to-metal and an O-ring. The male connection is similar to, but not interchangeable with, the American male NPSM. The female swivel BSPP has a tapered nose flareless swivel, where the seal occurs on the cone seat of the male connector.

German Connections

DIN series is a metric style connection found in hydraulic systems. The male connector has a straight metric thread with a 60° angle on the recessed cone, where the female has a straight thread with a seat and tapered nose. The seal takes place on the contact cone of the male and the tapered nose of the female flareless swivel

DIN series is a male with three possible female halves. The straight metric thread male has a 24° angle. The recessed counter-bore matches the tube OD it connects to. The following can be one of the female fittings

• A tube, nut and ferrule (compression style)
• A tapered nose flareless swivel
• A tapered nose flareless swivel with DKO style O-ring in the nose

DIN is a male connector and female port. Although It is made to German specifications, it can sometimes be a reference to connectors and port designs by other countries.

American Connections

NPT (National Pipe Tapered) pipe threads have been used for over a hundred years. NPT is a standard for tapered threads on pipes and fitting sin the United States of America. The most common use of NPT fittings is to seal pipes for fluid and gas transfer. The nominal pipe size can be identified by measuring the thread diameter and subtracting ¼&#;.

NPT fittings are available in iron or brass for low-pressure applications andcarbon steel and stainless steel for high-pressure.

NPTF (National Pipe Tapered Fuel) style connections are commonly used influid power systems. They have a tapered thread by which a seal is made by the deformation of the threads. NPTF threads are measured at the thread diameter and by subtracting ¼&#; to establish the nominal pipe size.

NPSM (National Pipe Straight Mechanical) connections are commonly used in fluid power systems. The female component incorporates a straight thread with an inverted 30° seat. The male component has a straight thread and a 30° internal chamfer. A seal is made by compression of the 30° seat on the chamfer; this is considered a mechanical connection. If an NPTF male is properly chamfered, it will also seal with an NPSM female connection.

Are you interested in learning more about BSPT Male Tapered Hydraulic Hose Fittings? Contact us today to secure an expert consultation!

Society of Automotive Engineers Thread (SAE)

SAE J straight thread O-Ring Boss (ORB) is recommended by the National Fire Protection Association (NEPA) for leak prevention in medium and high-pressure hydraulic systems. The male connection is a straight thread with an O-ring. The female port has a straight thread and a machined surface to provide a smooth, flat surface (minimum spotface), along with a chamfer where the O-ring seats. It seals when the O-ring is compressed into the chamfer when mating the male connection. This is also considered a mechanical connection.

SAE J514 JIC/37° hydraulic connections are common in most fluid power systems. Both male and female components have 37° seats. The seal is made by establishing contact between the male flared and female coned seat. This is also considered a mechanical connection.

Please note, sizes -02, -03, -04, -05, -08 and -10 of SAE 37° and SAE 45°have the same threads but NOT the same seat angles. Intermixing two different types of fittings will result in leaks. Please take care when measuring seat angles.

SAE J (ORFS) O-ring Face Seal connections are considered the best for leak control. The male connector has a straight thread and an O-ring in the face. The female has a straight thread and a machined flat face. The seal occurs when the O-ring compresses onto the flat face of the female, similar to the split flange type fitting. The threads maintain the connection mechanically.

SAE J512 inverted connections are typically used in automotive systems. The male connector is usually a 45° flare within the tube fitting or a 42°seat in the machined adapter. The fittings are sealed at the flared surfaces. These threads also maintain a mechanical connection.

SAE J518 4-bolt flange*. There are two pressure ratings for these connections: Code 61 (the standard series) and Code 62 (the psi series). The design is the same for each series; however, the flange head diameters and bolt hole spacing are larger for the psi high-pressure Code 62 connection. The female port of the fitting is a smooth, unthreaded port with four bolt holes set in a rectangular pattern around the port. The male is a flanged head with a groove for an O-ring and either split or captive flange halves and bolt holes which match the port. The seal is made where the O-ring is compressed, between the flanged head and the flat surface of the port. The connection is held in place by threaded bolts.

*Excluding bolt sizes, SAE J518, JIS B , ISO/DIS and DIN are interchangeable.

ISO Connections

ISO/DIS 4-bolt flange is a common connection found in fluid power systems. There are two pressure ratings for this connection: Code 61: PN35/350 bar (standard series) and Code 62: PN 415 bar (high pressure). Both connections maintain the same design, yet the bold hole spacings and flanged head diameters are larger on the PN 415. Inch or metric bolts are found in these connections. However, there is an &#;M&#; stamped on the port if metric bolts are to be used. The female port of the fitting is a smooth, un-threaded port with four bolt holes set in a rectangular pattern around the port. The male is a flanged head with a groove for an O-ring to seat and split or captive flange halves and bolt holes which match the port. The seal is made where the O-ring is compressed between the flanged head and the flat surface of the port. The connection is held by threaded bolts.

ISO port and stud ends with ISO 261 threads and O-ring seal is similar to the SAE J514 straight thread O-ring Boss (ORB). This connection incorporates metric threads. The male connector has straight threads with an O-ring. The female port is straight threads machined surface to provide a smooth, flat, accurately located surface with minimum spotface. This also applies to the O-ring seats which seals when the O-ring is compressed into the chamfer while mating with the male connection. This is considered a mechanical connection.

Japanese Connections

JIS Tapered Pipe (PT) has metric threads per JIS B . This connection is comparable to the design of the BSPT connections in their dimensions and appearance. The connections are also interchangeable with BSPT connections.

JIS 30° male inverted seat connections are parallel pipe threads per JIS B. JIS parallel connections are comparable and interchangeable with BSPP connections.

JIS 30° female (cone) seat are parallel threads per JIS B . Japanese JIS 30° flare connections are comparable to American SAE 37° flare connections in application and sealing. However, JIS 30° flare angle and dimensions are different with the threads being similar to BSPP.

JIS B 4-bolt flange connections are frequently used in fluid power systems. There are two pressure ratings for JIS B 4-bolt flange fittings:

1. Type I Code 61 (standard series 4-bolt flange).
2. Type II Code 62 ( psi series).

The flanged head diameters and bolt hole spacing are larger for Type II psi connections. Metric and inch bolts are each used with these connectors. The male connector has a flanged head with a groove for seating an O-ring and either a captive flange or split flange with boltholes to correspond to the port. The female port of the fitting is a smooth, un-threaded port with four bolt holes set in a rectangular pattern around the port. The seal is made when the O-ring is compressed between the flanged head and the flat surface of the port. The connection is held in place by threaded bolts.

JIS 210 Kgf/cm2 4-bolt square flange incorporates a JIS 4-bolt square flange connection which is comparable to SAE 4-bolt flange connections with the only difference being the flange and the JIS bolt pattern being square.

Instrumentation Fittings

Double and single ferrule instrumentation fittings are widely used in fluid or gas transfer. The most common applications are in refineries, chemical and food processing plants. The male end of a double-ferrule instrumentation fitting has a recessed counter-bore which matches the tube OD being used, plus an inner cone. The seal is made between the front ferrule and the cone. The tubing is held in place by the swaging action caused by the tightening of the nut. This forces the front and back ferrules to bite into the tubing, firmly holding it in place. This allows for the use of an un-flared tubing with these connectors.

The single-ferrule instrumentation fitting is similar but has a larger front ferrule and no back ferrule. The sealing method is also similar. Both types of instrumentation fittings are commonly available in stainless steel and brass.

Instrumentation fittings have UNEF (extra fine) threads and sizing is determined by the outside diameter of the tubing being used.

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