What is a Pipe Bushing? Uses, Benefits, and Types Explained

Pipe bushings are essential components in fluid handling systems as a connection point between two pipes of different sizes with each other in order for systems to run smoothly. These small yet important fittings allow you to easily add piping connections with different diameters to existing pipes without loss of strength and integrity of the system.

At Redhorse Performance, we know selecting the correct fitting can make or break a high performance system. And whether you are dealing in automotive performance hose assemblies, power steering assemblies, oil lines, hydraulic systems, electronics, or science and laboratory systems, you must first know the basics of pipe bushings and why you need them in your applications to ensure no leaks, and the most reliable connections.

What Is a Pipe Bushing?

A pipe bushing is a threaded fitting designed to reduce the size of a pipe connection, allowing a smaller pipe or fitting to be securely connected to a larger threaded opening. The bushing has threads that fit the larger connection, and inside threads that fit the smaller connector, allowing for a seamless transition between different sizes.

The simple idea is a hollow, cylindrical body with two different thread diameters on the outside and inside. This two-threaded configuration provides a bushing with a connection for two pipes of different sizes.

Pipe bushings are unlike solid plugs since they allow flow passage through the fitting. Npt pipe plug seals at the threads, but since the hole is larger than the threads, a bushing is needed to allow liquid to flow through. This through-flow structure of bushings is crucial in active systems with required size change.

Key Uses of Pipe Bushings

Reducing Pipe Sizes Efficiently

Pipe bushings primarily serve as devices for smooth transitions between pipe sizes in the same system. This easy sizing flexibility provides engineers an ability to size pipe to various system sections by considering flow, space, cost and flow velocity.

In performance applications, for example, bushings permit smaller performance hose assemblies to be connected to larger system ports without the need for complex custom adapters. In racing and performance automotive applications, where weight and space are at a premium, the flexibility is invaluable.

Size transitions are often needed in industrial systems to meet different equipment requirements or to achieve proper flow velocity in different system sections. Bushings offer an inexpensive, relatively simple way to make such transitions without compromising system integrity.

Preventing Leaks and Improving Seal

Properly selected and installed pipe bushings create reliable sealing interfaces that prevent costly leaks and system failures. The threaded design offers a number of points of seal and controlled pre-load upon installation.

Thread engagement distributes sealing forces evenly around the connection circumference, reducing stress concentrations that could lead to seal failure. This distributed loading is of particular importance in high-pressure applications where seals are key to safety and performance.

Applications Across Plumbing, Gas, and Hydraulic Systems

Bushings are used in both residential and commercial plumbing systems when changing pipe sizes or modifying their water systems. The flexibility to be deployed across various pipe diameters streamlines installation and minimizes reliance on custom fittings.

Bushings are used in gas distribution systems for the connection of various pipe sizes and components in a safe and leak-tight manner. The fact that this then has correct threading and seals reliably is critical for keeping up with safety codes and keeping dangerous gas from escaping.

Bushings connect one component to another with different port sizes in hydraulic-system industrial and mobile equipment. High-pressure hydraulic applications demand bushings capable of withstanding extreme pressures while maintaining seal integrity throughout the operating cycle.

Race and high performance hose systems use special bushings to allow lightweight construction and maximum flow. Many of these applications rely on tailored materials and designs in order to meet specific performance targets.

Types of Pipe Bushings Explained

Threaded vs. Slip Bushings

Threaded bushings have standard pipe threads on the exterior and interior, and can be connected directly for most applications. The threads provide a positive lock and help prevent backing out due to vibration and the hoisting process, as well as resistance to heat and loosening over time.

We can already tell that the tapered thread joint, which is created by standard NPT (National Pipe Thread) bushings, seals naturally with the amount of thread engagement we have. This self- sealing characteristic also means secondary gaskets are not required for most applications, making installation easier and reducing the chances of leaks.

Slip bushings are for use with smooth bore pipe or tube with internal compression fitting or other permanent retention method. Less commonly used than threaded varieties, slip bushings have benefits in situations where disassembly is frequent or where threading is not possible.

Combination bushings with a threaded and slip type connection offer the most versatility for tough jobs. These enable the connection of threaded and non-threaded components.

Metal vs. Plastic Bushings

Metal bushings are stronger and resist heat better than plastic bushings for long life in tough applications. Steel, stainless steel and brass models provide various levels of strength, corrosion resistance and economy.

Plastic bushes are used in certain applications due to their chemical resistance, electrical resistance or light weight. PVC, CPVC, engineered plastics etc have properties that cannot be achieved with metallic materials.

Hex Bushings, Flush Bushings, and Specialty Variants

Hex bushings have an added hex nut for easy wrench hold and are made for use with a box or socket wrench. This structure is also particularly favorable for use in narrow environments and for high torque applications.

Additionally, the hex design of the housing makes it easy to visually detect proper orientation and installation torque resulting in more consistent proper installation. Also a user can confirm visually that the threads of the screw are winding around the netting. It is particularly advantageous in a production situation where assembly steps are being performed by several technicians.

Flush bushings feature a lower profile exterior so as to minimize flow disturbance and to provide compact dimensions. Such special forms are often encountered in applications where high performance is of interest, and aerodynamic or hydrodynamic efficiency is to be taken into account.

How Pipe Bushings Differ from Other Fittings

Pipe bushings specifically enable size reduction while maintaining flow passage, distinguishing them from plugs, caps, and other closure fittings. An npt pipe plug plugs up a port, while a bushing does so with different dimensions.

Couplings pair pipes of the same diameter, while bushings join small pipes to large ones. It is this change in size that is the reason bushings are important to applications that need diameter changes without flow stop.

Reducers perform the same size change operation, only there is normally a different means of connection and different setup. Threaded connections are primarily used with bushings and existing spaces are reduced accordingly.

Adapters change the connection type, with the same one-size end connecting to the pool. Bushings on the other hand change the size, not the connection type. This specialization enables bushings to be ideal for selective size decrease.

Choosing the Right Pipe Bushing

Thread Compatibility

The most critical dimension when selecting a pipe bushing is the compatibility of the threads. NPT (National Pipe Thread) is only suitable for North American uses, while BSP (British Stand Pipe) threads are widely used internationally.

Thread pitch, taper, and engagement must correspond to system requirements for effective sealing and strength. Combining thread standards may discourage proper tightening, leading to insufficient sealing and unsafe conditions.

Material Selection

The material choice can be made depending on the operating environment to ensure better durability and long life. Material demands are affected by the extremes of temperature, chemicals and the mechanical stresses.

The pressure rating difference between materials is substantial, and higher strength alloys allow smaller cross-sections for the same strength. This optimization of material can be important in weight-sensitive or space-limited applications.

Cost/benefit analysis must weigh the cost of initial fitting against long-term performance and maintenance. High-end materials like stainless steel usually cost more but may offer better total cost of ownership.

Pressure and Temperature Considerations

The pressure rating of the system shall be higher than the maximum operating pressure and a proper safety margin shall be applied. Transient conditions such as pressure surges, water hammer and other conditions should be considered, in addition to steady-state pressure considerations.

The influence of temperature on the material is linked directly to performance pressure ratings. Material strength can be affected by elevated temperatures, but you also have significant loading on your threaded connections from thermal cycling.

Performance hose systems often operate under extreme conditions that demand specialized bushings designed for high-pressure, high-temperature service. Standard plumbing-grade fittings may be inadequate for these demanding applications.

Size Reduction Guidelines

A reasonable reduction ratio brings better flow properties of the entire system. Excess reduction in size can result in obstructions to flow and increased pressure drop in a system which decreases system efficiency.

The size reduction ratio is related to flow velocity in a given application. The presence of high-velocity flows may necessitate the use of tapered segments to avoid turbulence and energy losses.

Multiple small reductions generally do better than a single large reduction, from both flow and structural viewpoints. This staged method allows smoother changes of flow and better distributes the applied stress.

Conclusion

Pipe bushings are important parts in a fluid-handling system, allowing a fluid-handling system to transition between sizes without degrading the integrity or performance of the system. All types, material and optional can be used dry or lubricated, best performance for plumbing, hydraulic and gas systems.

Redhorse fitting has high performance hose ends, hoses and adapters. Our range of pipe bushing products come in a variety of sizes and specifications to ensure that there is a specific one perfect for your needs. When you need help selecting the right bushings for your specific system requirements, our experienced team is here to help.