Process of Elimination When Identifying Hydraulic Hose Fittings

Thursday, August 24, 2017 by Fluid Gas Handling Team

Identifying Hydraulic Hose Fittings - Product group of hose and fitting connections - Parker Hose Products Division

Industrial machines and equipment are designed and manufactured in every corner of the world. The hydraulic systems alone use countless different types of fittings and adapters with different sealing methods and thread forms. While the sealing method can often be distinguished by appearance, thread forms all seem to look the same, making it difficult and time-consuming to identify them when equipment modifications or repairs are needed. Identifying a fitting can be easily done, however, through the process of elimination after uninstalling the fitting.

First, determine the type of fitting – is it permanent or reusable?

Hydraulic hose fittings can be one of two types – permanent or reusable. Permanent or crimped hydraulic fittings are widely used in the fluid power industry because they are easier and quicker to attach than reusable fittings. Crimped fittings are also more reliable. To attach a crimped fitting, you will need crimping or swaging equipment. These fittings are squeezed onto the hose at assembly and are discarded when the hose assembly fails.

Reusable or field attachable hydraulic hose fittings are not commonly used today since they are considered "old technology." A reusable fitting is easily identifiable because it fits right onto a hose by using only a wrench and a vise. Reusable fittings typically cost more than crimped fittings and are more time consuming during the assembly process.

Identify fitting ends and port connections

Accurate identification of ports and connectors in a hydraulic system is necessary before the correct hose or tube assembly can be assembled and installed.

Port Connections

Tube/Hose Connections

NPT/NPTF
BSPT (JIS-PT)
Metric Taper
SAE Straight Thread
ISO 6149
JIS-B2351
DIN Metric
BSPP (JIS-PF)
4-Bolt Flange

37⁰ Flare
30⁰ Flare (Metric)
45⁰ Flare
24⁰ Flareless (SAE)
24⁰ Flareless (DIN)
30⁰ Flare (BSPP)
O-Ring Face Seal (ORFS)
60⁰ NPSM Swivel
60⁰ Cone (BSPP)
60⁰ Cone (Metric)

Next, identify the sealing method

Types of hydraulic fittings vary depending on their sizes, configuration, and thread types. The three most common types of hose fittings are O-ring, mated angle and threaded. However, there are several more types of hydraulic hose fittings available.

O-Ring: The three types of O-ring seal designs are O-ring boss, flat face O-ring seal and O-ring flange. With these types of couplings, there is an O-ring seal that is the main component in creating the seal.

Mated Angle: An example of a mated angle is SAE 45° or JIC 37° but there are others as well. Fittings with an angle seat have straight or parallel threads for sealing. When the male and female counterparts are threaded together, the threads themselves do not actually form the seal. Instead, they function mechanically to bring the two mating angle seats together which ultimately forms the seal.

Tapered Threads: These types of fittings have two types of threads: male or female. Male fittings feature their threads on the outside and female fittings have threads on the inside. When the male and female counterparts are threaded together, the tapered threads deform which applies pressure on the couplings ultimately making a tight seal. Tapered threads can be imprecise but never use tape to ensure the seal. Tape is often banned in hydraulic and pneumatic systems because of its tendency to shred and contaminate sensitive areas. Its lubricity has also been known to induce over-torquing.

Then, look at the fitting design

After you have determined the sealing method, visually look at the location of the O-ring, nose seat, seat angle and fitting termination. You can visually see the O-ring location as well as the type of nose seat. However, you will need to use a seat gauge to determine seat angle.

Mated Angle Seat with O-ring:

O-Ring Location	Nose Seat	Seat Angle	Fitting Termination
Inside	Inverted	60⁰ Inclusive	British Standard Pipe Parallel
Inside	Inverted	24⁰ Inclusive	DIN 24⁰ Cone

O-Ring Face Seal:

O-Ring Location	Nose Seat	Seat Angle	Fitting Termination
In Flange Groove	Flat Face	N/A	SAE O-Ring Flange (Code 61 or 62)
Outside	Flat Face	N/A	SAE O-Ring Boss
At Nose Seat	Flat Face	N/A	O-Ring Face Seal

Mechanical Joint or Mated Angle:

O-Ring Location	Nose Seat	Seat Angle	Fitting Termination
None	Standard	37⁰	JIC 37⁰ Flare
None	Standard	45⁰	JIC / SAE 45⁰ Flare
None	Standard	30⁰	Japanese Industrial Standard & Komatsu
None	Inverted	N/A	Metric Stand Pipe
None	Inverted	30⁰	National Pipe Straight
None	Inverted	45⁰	SAE Inverted Flare
None	Inverted	24⁰	Inclusive French Gaz 24⁰ Cone
None, except -20	Standard	24⁰	Inclusive French Gaz 24⁰ High-Pressure Flange

Thread Interface:

O-Ring Location	Nose Seat	Seat Angle	Fitting Termination
N/A	N/A	N/A	National Pipe Tapered
N/A	N/A	N/A	British Standard Pipe Tapered

Identifying Hydraulic Hose Fittings - Parker Hose Products Division - Visual Fitting Index

Lastly, measure the thread

With the caliper, measure the thread diameter of the largest point (Outside Diameter (O.D.) of male threads; Inside Diameter (I.D.) of female threads). Using the thread gauge, determine the number of threads per inch. Comparison of gauge and coupling threads against a lighted background will ensure an accurate reading.

Parker’s Hose Products Division has shadow images to easily determine thread, cone and hex size. Click on these images to print out a useful guide to assist in identifying hydraulic fittings.

Identifying Hydraulic Hose Fittings - Parker Hose Products Division - Male Pipe Thread Sizes

Identifying Hydraulic Hose Fittings - Parker Hose Products Division - SAE Nut and Nipple Chart

After you have determined the hydraulic hose fitting you need to replace, Parker Hannifin is an ideal supplier of choice. Parker offers the largest selection of hydraulic hoses plus more hydraulic fitting sizes than any other manufacturer. Parker’s Hose Products Division offers steel, brass, and stainless steel fittings from 3/16" to 3". Styles include O-ring face seal, flare, male pipe, metric designs and much more. Custom tube and hose fittings are also available in various configurations including NPTF, JIC, SAE, GAZ, ISO, DIN, JIS and BSP. Many manufacturers offer fitting wall charts as well to assist in the identification process.

Kyri McDonough, Hose Products Division, Parker Hannifin Article contributed by Kyri McDonough, marketing services manager at Hose Products Division, Parker Hannifin.

Other related topics on hydraulic hose, hose application, and selection criteria:

An Effective Way to Identify Hydraulic Fitting Orientation
Decoding a Hydraulic Hose Layline
Five Most Important Factors You Need to Consider for Hydraulic Fittings
Hydraulic Hose 101: Fast Facts
Successful Hydraulic Hose Assembly Starts Here
Going to Extremes: A Closer Look at Hydraulic Hoses

Comments for Process of Elimination When Identifying Hydraulic Hose Fittings

Kevin Krizan

Hello, I have been trying to identify the correct part number for two fittings. I have parker # 13943-8-8 and 10643-8-8 a 90deg elbow and straight 43 series fittings which are made from steel. I need to replace them both with the same style but made from stainless steel. Can you please provide the correct part number to order for each? Also would the hose material be the same for stainless steel, if not please also provide part number for the correct hose.
Thank you in advance for the help.

Kyri McDonough

Stainless steel fittings have the exact same part number except that it ends in a C. For instance, 10643-8-8C would be the stainless part number.

Sushma Shetty

Nice and very informative blog, will also like to add that there is also a product known as hose clamp which also provides additional holding power and grip.

Thank you!

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