Hydraulic Fitting Types and Their Applications: A Complete Guide

We see sanitary pipes in our bathrooms, gas and petroleum pipelines, etc., daily. So, what do these pipes do? These pipes transport fluids or gases from main points to further subpoints. So, this system is called a hydraulic system, and these pipes and connectors are called hydraulic fittings. In this article, we provide comprehensive information regarding hydraulic fittings, their types, standards and applications, etc.

What Are Hydraulic Fittings?

We often see the complete structure of pipes in daily life. The most common example is in our homes, i.e. in our bathrooms, kitchen etc. These fittings are the passage of fluids in the systems. They make connections between the pipes to provide smooth transportation of fluid with leak-proof joints.

The Importance of Hydraulic Fittings in Fluid Systems

These pipes are crucial parts of hydraulic systems. They are important because they ensure smooth transportation by preventing leaks and pressure drops. Their applications can be found in automotive, heavy machinery and industrial equipment hydraulic systems.

What Is a Fluid System?

A fluid system is a complete network composed of many parts such as valves, pipes and tubes, pumps, etc. This fluid system is responsible for controlling and transporting the fluids or gas from the main point to the subpoints. It is used in cars, cranes, airplanes, etc. It is used in high or low pressures.

What Makes Hydraulic Fittings and Couplers Fail?

There are many reasons why hydraulic fittings and couplers fail. Such as:

1. Improper Installation
2. Material incompatibility
3. Excessive Pressure
4. Wear and tear in the joints

Key Components of Hydraulic Fittings

The following table shows the function of each part in a hydraulic system:

What Are the Most Common Types of Hydraulic Fitting Connections?

As we know, hydraulic fittings are used as connectors between the pipes to make hydraulic systems. There are various types of connectors, a few of which are discussed in this article.

What Are the Different Types of Threads on Hydraulic Fittings?

The following are the types of hydraulic fitting connection types.

NPT (National Pipe Thread)

NPT stands for National Pipe Thread. This type of thread on the hydraulic fittings is tapered and creates a seal through deformation. North America uses such tapered threads, and its types include National Pipe Thread Fuel (NPTF) and National Pipe Straight Mechanics (NPSM).

BSP (British Standard Pipe)

These threads have a 55^o V-thread with round roots and crests. Its common types include BSPP and BSPT. Such threads are used for sealing purposes in Europe and Asia.

JIC (Joint Industry Council)

These threads contain a 37^°flare on the surface, which provides strong leak-proof connections. You can use such threaded hydraulic fitting for high-pressure applications.

SAE 45° Thread

A 45^° flare on the surface of a thread makes these joints strong and leak-proof. You can use threaded hydraulic fittings for automotive and industrial applications.

BSPT (British Standard Pipe Tapered)

These threads on the hydraulic fittings are tapered and used for high-pressure applications. These threads provide a stronger and tighter seal to the connections.

Flanged Connections

Multiple flanges are used to make a tight seal in the connections. These connections are leak-proof and used in high-pressure applications. Its types are welded and bolted flanges.

Welded Flanges

To connect two or more pipes permanently, welded flanges are used.

Bolted Flanges

Some applications require frequent maintenance, assembly or disassembly. Bolted flanges are used for this purpose.

Quick-Connect Couplings

For making quick connections, these couplings are used.

Couplings for Low Pressure

Applications like pneumatic systems are low-pressure applications; in this case, these couplings are used.

High-Pressure Couplings

Applications like hydraulic systems bear extreme pressure; that's why high-pressure couplings are suitable for such applications.

Types of Hydraulic Fittings: Designs & Applications

Various hydraulic fittings are available with their designs. These designs are the base of their applications. The following are some common hydraulic fittings.

Crimped Fittings

Crimped Fittings are permanently connected to hoses through a crimped tool. This hydraulic fitting is used for high-pressure applications.

Push-Lock Fittings

The designs of these fittings make them fit to assemble and disassemble easily. These fittings are considered ideal fittings.

Field Attachables

Easy to install and use for on-site repairs and maintenance.

Crimped Fittings VS Field Attachable Fittings

Crimped Fittings: Non-Detachable

• High strength and Durability
• Suitable for high-pressure applications

Attachable Fittings: Re-Detachable

• Ease of Assembly and Disassembly
• Useful when frequent maintenance is required

Bite-Type Fittings

• This fitting uses a ferule to bite into a hose
• Used for medium-pressure applications
• Stronger and leak-proof joint

Ferrule Fittings

• Use a metal ring to compress the hose = Tight seal
• Used in hydraulic and pneumatic systems

Tube Fittings

Two main types: Compression and flare tube fittings

Used to connect two or more pipes in the Hydraulic System

Compression Tube Fittings

The design of these fittings is such that there is a ferule which compresses the tube. Well-suited fittings for high-pressure applications such as hydraulic cylinders in heavy machinery.

Flare Tube Fittings

• Flared tube end is used to create a seal
• Used in automotive and hydraulic systems

Hydraulic Fitting Materials and Their Benefits

Hydraulic Fittings are made of multiple materials. These materials are different in terms of mechanical and chemical properties. Their atomic structure affects their properties, so, ultimately, their applications. Some of the common materials are given below:

Steel Hydraulic Fittings

Steel is a very durable and strong material, good for harsh conditions. Steel often faces an issue of corrosion in difficult conditions, but this can be managed by coating. We use steel in oil and gas pipelines.

Stainless Steel Hydraulic Fittings

Stainless steel contains 15-20% Cr in the composition, which makes it very resistant to corrosion and oxidation. Its extremely good corrosion resistance, strength and durability make it able to be used in the marine and chemical industries.

Brass and Bronze Fittings

• Good wear and corrosion resistance
• Use for low-pressure applications
• Good Conductivity

Aluminum Hydraulic Fittings

Al contains a passive layer of Al₂O_3, which makes it resistant to corrosion and oxidation even at high temperatures. Other properties include its light weight and high strength-to-weight ratio. Al hydraulic fittings are used in aerospace and automotive industries due to light weight.

Plastic Hydraulic Fittings

Plastic is a lightweight and weak material, but one good thing is its corrosion resistance. Plastic hydraulic fittings are often used in sanitary systems.

How to Select the Right Hydraulic Fitting for Your Application

It is not wise to choose any hydraulic fitting without considering important factors. These factors are briefly discussed below. If you ignore these factors, it will strongly affect the ultimate applications.

Size and Pressure Rating Considerations

• Most important factor
• Because a mismatch in the sizes will lead towards leakage issues
• Inappropriate hydraulic fittings for pressure ratings will result in explosive disaster

Matching Fitting Types to Hose and Equipment

Hoses and other equipment such as valves, etc., of a hydraulic system are important components. The hydraulic fittings we choose for these components must match their sizes to prevent leakage issues and system failures.

Choosing Fittings Based on Fluid Type

There are multiple fluid types such as Newtonian fluids (water, air, etc.), non-Newtonian fluids (toothpaste, etc.), super fluids, etc. So, it is important to consider the fluid type before you choose a hydraulic fitting. The main reason is the type of pressure in these fluids.

Hydraulic Fitting Sealing Types and Their Applications

In this section, we are going to discuss different types of selling and their applications. The design of these seals is the main difference in these sealing types.

O-Ring Seals

O-ring seals are circular in design and have elastomeric gaskets. You can use these seals for a very strong and leak-proof connection in hydraulic and pneumatic systems. These seals can be made of nitric rubber, Si or Viton because of their chemical, temperature and pressure resistance. These seals block escapes of gases and liquids.

Metal-to-Metal Seals

Metal-to-metal seals are made of two metal sheets which are directly connected. This connection is so tight that even gases can't escape from this kind of seal. No additional material like elastomer is required because these sheets are prepared so precisely. These metal-to-metal seals are used in oil & gas pipelines and in the aerospace industry.

Flat Seals

These seals are very simple, like flat gaskets. These seals are not expensive, which is why they are used in cost-effective and low-pressure applications. The common materials used to make flat seals include rubber and Si. Other applications include pipe flanges, engine components, etc.

Compression Seals

Compression Seals are a sealing mechanism which uses mechanical force to compress a sealing material. Their real-life applications include pipe joints and valve systems. Best for durable, reliable and leak-proof connections.

Hydraulic Fitting Standards and Certifications

Here, some common fitting standards and certifications and their user countries are briefly discussed.

International Standards for Hydraulic Fittings

Many international standards such as ISO, SAE, etc. govern properties and safety criteria, etc. Multiple crucial industries, such as aerospace, automotive, etc., use these standards according to their countries.

ISO Standards

ISO standard is a universal standard and is used in every country. This standard governs factors like compatibility and quality for hydraulic fittings.

SAE Standards

North America uses SAE standards. SAE is a society of automotive engineers which developed multiple standards. For instance, a standard, SAE J1453, is used for O-ring face seal fittings. Another standard is “SAE J514”, which is used for hydraulic tube fittings. These standards govern the safety and efficiency of industrial machinery in vehicles, etc.

JIS Standards

JIS means Japan Industrial Standards, these standards are used as a guide for quality and safety requirements of hydraulic fittings. Japan uses these standards mainly. JIS B 2351 is the main standard of these standards, which specifies materials and dimensions in hydraulic flanges. Its other applications include robotics and manufacturing industries.

Certification and Quality Assurance

Any component made in the industry must meet these certification and quality assurance requirements to perform well in the applications.

Troubleshooting Hydraulic Fitting Problems

During hydraulic fitting, multiple issues can occur. If you know some troubleshooting for these issues, you can stop the disasters.

Identifying Common Issues with Fittings

You should have an idea about the common issues, like what are the common issues that can occur during fitting. The common issues include leaks, installation and materials compatibility. If you have regular inspections, these issues can be tackled.

Causes of Leaks and How to Fix Them

Poor thread connections or leakage at seals cause leaks in the fitting. Proper installation and maintenance are helpful to this issue.

• Leaking at Threaded Connections
• Use proper thread engagement and thread sealant
• Leaking at Seals
• Inspect the seals daily and replace them on time

Installation Errors and How to Prevent Them

Installation errors commonly occur due to unskilled labour. Inappropriate materials and sizes are the other causes. Use appropriate tools and fitting sizes.

How To Install Hydraulic Fittings and Maintain Them?

Some important guidelines are given below to install hydraulic fittings and maintain them:

Step-by-Step Installation of Hydraulic Fittings

• Choosing the Correct Tools

Choose suitable tools during installation to avoid issues like poor connections, etc.

• Proper Tightening Procedures

Multiple tightening procedures are available on the internet. You should follow these procedures carefully.

Routine Maintenance Tips for Fittings

In the routine maintenance, the main thing is the surface cleaning to resist wear and corrosion. So, surface treatments should be suitable for the fittings' material.

FAQs

What are the different types of hydraulic fittings?

Flanged, threaded, quick-connect couplings, etc., are the different types of hydraulic fittings.

What is the difference between SAE and NPT hydraulic fittings?

SAE

• 45^o flare on the surface of fitting
• Used in automotive applications

NPT

• Tapered threads
• Useful for plumbing and industrial systems

What materials are best for hydraulic fittings?

1. Choose stainless steel for high-pressure applications
2. Choose copper or brass for low-pressure applications