Hydraulic Hose Fitting Types (Fitting types and Characteristics)
Authored by: Eric Malo 11/21/23
If you work with hydraulic systems, you know the importance of using the correct hydraulic hose fittings for your hoses and tubes. Hydraulic hose fittings are connectors that allow fluid to flow from one component to another in a hydraulic circuit. Depending on the application and industry standards, they
come in different types, sizes, and configurations.
But how do you identify the correct hydraulic hose fittings for your needs? How do you know which type of fitting will provide a reliable seal and hold under pressure? How do you avoid leaks, damage, and downtime caused by using the wrong fittings?
In this blog post, we will guide you through the process of identifying hydraulic hose fittings using some simple tips and tools. We will cover the following topics:
👷The main types of hydraulic hose fittings and their characteristics
👷 The standard methods of sealing and connecting hydraulic hose fittings
👷 The tools and measurements you need to identify hydraulic hose fittings
👷 The best practices for choosing and installing hydraulic hose fittings
The Most Common Types of Hydraulic Hose Fittings
Hydraulic hose fittings can be classified into three basic categories: metal seal, soft seal, and tapered thread.
Metal Seal Fittings
Metal seal fittings use a tapered thread combined with a machined face to provide a seal capable of handling high pressure. The thread helps to hold the fitting in place while the machined face manages the sealing. Metal seal fittings are easier to orient than tapered thread fittings, and they generally provide a better seal without the need for any additional sealant. However, they still require welding or
soldering to the tube.
Examples of metal seal fittings are:
👷 JIS-B2351 30° Flare (BSPP): These fittings have a 30° flare on the male end and a BSPP (British Standard Pipe Parallel) thread on both ends. They are commonly used in Japanese
👷 NPT/NPTF 37° Flare: These fittings have a 37° flare on the male end and an NPT (National Pipe Tapered) or NPTF (National Pipe Tapered Fuel) thread on both ends. They are widely used in North America.
👷 BSPT (JIS-PT) 30° Flare (Metric): These fittings have a 30° flare on the male end and a BSPT (British Standard Pipe Tapered) or JIS-PT (Japanese Industrial Standard Pipe Tapered) thread on both ends. They are also used in Japanese equipment.
👷 DIN Metric O-Ring Face Seal (ORFS): These fittings have an O-ring on the flat face of the male end and a metric thread on both ends. They are designed to meet the DIN (Deutsches Institut für Normung) standards.
Soft Seal Fittings
Soft seal fittings use an elastomeric seal that prevents leakage even under high-pressure situations. They are easy to install and remove and can resist the heavy vibrations that many systems are subject to. They do not require welding or soldering to the tube.
Examples of soft seal fittings are:
👷 SAE Straight Thread: These fittings have an O-ring on the straight thread of the male end and an SAE (Society of Automotive Engineers) straight thread on both ends. They are also known as O-ring boss or ORB fittings.
👷 Flat-Face O-Ring Seal: These fittings have an O-ring on the flat face of the male end and a straight thread on both ends. They are also known as flat face or ORFS fittings.
👷 O-Ring Flange: These fittings have an O-ring on the flange of the male end and a flange on both ends. They are also known as flange or Flange fittings.
Taper Thread Fittings
Tapered thread fittings use a tapered thread that changes in diameter along the length of the fitting, making the connection tighter as it is screwed in. These fittings do not require a sealer, such as a chemical sealant or a tape sealant, to ensure no leakage around the fitting.
Examples of tapered thread fittings are:
👷 NPT/NPTF: These fittings have an NPT or NPTF thread on both ends. They are similar to NPT/NPTF 37° flare fittings, but without the flare.
👷 BSPT (JIS-PT): These fittings have a BSPT or JIS-PT thread on both ends. They are similar to BSPT (JIS-PT) 30° flare fittings, but without the flare.
👷 Metric Taper: These fittings have a metric taper thread on both ends. They are similar to DIN metric O-ring face seal fittings, but without the O-ring.
As we have seen, hydraulic hose fittings use different methods of sealing and connecting to prevent leaks and ensure a secure fit. The most common methods are:
👷 O-ring seals: These are elastomeric rings that fit into a groove on the fitting and create a seal when compressed by the mating part. They are effective at preventing leaks and can handle high pressure and temperature. They are also easy to replace if damaged or worn out.
👷 Flare seals: These are conical surfaces that mate with a corresponding flare on the fitting and create a seal when tightened. They are also effective at preventing leaks and can handle high pressure and temperature. However, they can be damaged by over-tightening or misalignment.
👷 Mated angle seals: These are straight or parallel threads that mate with a corresponding angle on the fitting and create a seal when tightened. They are less effective at preventing leaks than O-ring or flare seals, and they require additional sealant to ensure a proper seal. They are also prone to damage by over-tightening or misalignment.
Tools For Fitting Identification:
The Tools and Measurements You Need to Identify Hydraulic Hose Fittings to identify hydraulic hose fittings, you need some basic tools and measurements.
👷 A caliper or a ruler: These are used to measure the inner diameter (ID), outer diameter (OD), thread size, and thread pitch of the fitting. The ID is the distance across the opening of the fitting, the OD is the distance across the widest part of the fitting, the thread size is the nominal diameter of the thread, and the thread pitch is the distance between two adjacent threads.
👷 A thread gauge: This is used to determine the type of thread of the fitting. It has
different profiles that match different thread standards, such as NPT, BSPP, BSPT, JIS, SAE, DIN, etc. You can use it to compare the fitting thread with the gauge profile and find the matching one.
👷 An angle gauge: This is used to measure the flare angle or the fitting mated angle. It has different angles that match different flare or mated angle standards, such as 30°, 37°, 45°, etc. You can use it to compare the fitting angle with the gauge angle and find the matching one.
The Best Practices for Choosing and Installing Hydraulic Hose Fittings
Once you have identified the correct hydraulic hose fittings for your hoses and tubes, you need to follow some best practices to choose and install them properly. These include:
👷 Choose the correct size, pressure, temperature, material, style, and fitting orientation for your application. Ensure the fitting is compatible with your hose or tube type, diameter, length, bend radius, working pressure, temperature range, fluid type, etc. Also, make sure the fitting matches your system configuration, layout, direction of flow, etc.
👷 Determine the insertion depth of the fitting and mark it on the hose or tube. The
insertion depth is how far you need to insert the hose or tube into the fitting to ensure a proper seal and hold. You can find it in the manufacturer's specifications or instructions.
Marking it on the hose or tube will help you avoid over-inserting or under-inserting it into the fitting.
👷 Lubricate the hose or tube before inserting it into the fitting. Lubrication will make it easier to slide it into the fitting and prevent damage to the hose, tube, or the fitting. You can
use compatible lubricants such as oil, grease, soap, etc.
👷 Align and tighten the fitting according to the manufacturer's specifications or instructions. Confirm you align the fitting correctly with the hose or tube and the mating part before tightening it. Use a torque wrench to tighten it until it reaches the required torque. Do not over-tighten or under-tighten, as this can cause leaks, damage, or failure.
👷 Test the connection for leaks and performance. After installing the fitting, you must test it for leaks and performance. You can use a pressure gauge, a flow meter, a leak detector, etc., to check for any leaks or problems with the connection. If there are any issues, you need to fix them before using your hydraulic system.
Hydraulic hose fittings are essential components of any hydraulic system. They allow fluid to flow from one component to another in a hydraulic circuit. Depending on their application and industry standards, they come in different types, sizes, and configurations.
To identify hydraulic hose fittings correctly, you need to follow some simple steps:
👷 Check their ends and port connections
👷 Find out if they are reusable or not
👷 Look at their sealing method
👷 Examine their design
👷 Measure their ID, OD, thread size, thread pitch, and angle
👷 Compare them with a thread gauge and an angle gauge