Importance of Hydraulic Fittings
Fittings are one of the most important components in a well-designed hydraulic system. The correct fitting allows hydraulic components to be plumbed together in an easy, leak-free fashion. The fitting selected should match the system’s pressure requirements, the environmental conditions the system will operate in, and be compatible with the fluid that is being used in the system. This article will help give you insight into how to properly choose the correct fitting for the application.
How to select the correct hydraulic fitting?
When selecting a fitting for your hydraulic system pay attention to the following factors:
Pressure requirements: Fittings are rated for the maximum operating pressure they can withstand. Using a fitting that doesn’t match the pressure that is going to be used in the system will result in fitting failure.
Fluid compatibility: Knowing what type of fluid you are going to run in your system is necessary for optimal performance and durability. Some fluids are not compatible with the fitting material and will cause premature corrosion.
Environmental conditions: Some fitting materials, like stainless steel, have better corrosion protection than others. If your system is consistently being operated in a wet, salty environment, make sure your fittings will withstand those harsh conditions.
System design conditions: The wrong fitting orientation and size can cause your system to heat up faster and higher than designed, potentially causing failure of system components. Selecting fittings that promote a smooth, laminar fluid flow helps protect the hydraulic system.
Vibration and shock: Over time, vibration and shock can cause fittings to loosen up and result in leaks. When picking a fitting, consider the fitting’s function within the system and choose one that is isn’t susceptible to loosening while the machine is running.
Thread type and sealing mechanism: Before purchasing any fittings, it’s crucial to know the thread size of ports in hydraulic components. Using two fittings with unmatched thread size and pitch will result in a leak, or system failure. Make sure the thread sizes match so that the fitting will tighten properly.
How to determine what hydraulic fitting type you need
The first step is to determine the type of fitting you currently are using in your system or the type of fitting that will work best for your system. The following section will explain how to recognize a hydraulic fitting and what applications it is best used for. One of the biggest obstacles is figuring out what type and size of fitting you are currently using on your system. A set of Fitting Gauges is a helpful tool to have to be able to determine the size and thread pitch of your current fittings.
Joint Industry Council (JIC)
The JIC (Joint Industry Council) fitting is an extremely common type of fitting. The end is beveled at 37°. The female end is the opposite shape 37⁰ angle. When they are tightened together, they form a leak free connection.
JIC fittings are desirable for high temperature applications and can be connected and disconnected repeatedly without failure. These fittings work with a range of operating pressure from 0-5000 psi depending on size.
O-Ring Boss (ORB)
The ORB (O-ring Boss) fitting is also an extremely common type of hydraulic fitting. The female side has a flat shoulder cut above the threads that mates with the O-ring that is placed around the underside of the nut.
When the fitting is tightened, the O-ring is forced against the boss and provides a leak free connection. This fitting is excellent for medium to high pressure applications with a working pressure rating from 0-5000 psi depending on size. This fitting is not good in high temperature applications because of the location of the O-ring. The O-ring can be cut during improper installation which will cause a leak.
National Pipe Tapered (NPT)
The NPT (National Pipe Tapered) fitting is the traditional hydraulic fitting of choice. With advances in fitting technology, it has become a less-than-ideal fitting in most applications. The threads of an NPT fitting are tapered making the male and female parts an interference fit. This is what creates the sealing surface of the fitting.
This fitting requires a sealing substance to ensure it won’t leak. We suggest using Loctite 545. Teflon tape shouldn’t be used with this type of fitting. Small pieces of Teflon can break off and enter the system clogging small orifices. NPT fittings are commonly found on low pressure parts of hydraulic systems, especially coming out of a reservoir. The pressure rating for an NPT fitting is from 0-2500 psi. Overtightening can cause cracking in the fitting and will cause a leak in the system.
O-Ring Face Seal (ORFS)
The ORFS (O-ring Face Seal) is a fitting that is excellent for high temperature, high pressure applications being rated for up to 6000 psi. The end of the male fitting has a machined groove that contains an O-ring. The female side is a machined flat surface. When tightened, the fitting creates a solid leak free connection.
The ORFS fittings are also very tolerant of high vibration applications and are extremely easy to install and tighten correctly.
Installation best practices
Whichever type of fitting that you choose, following these guidelines for installation will greatly ensure a leak-free connection.
Ensure cleanliness: Inspect and clean both the male and female end of the fitting. Dirt and debris trapped between the two parts will not allow the fitting to seal properly.
Inspect components: Make sure both ends aren’t damaged or deformed. Small nicks and cracks will guarantee a leak, especially under pressure.
Proper alignment: Fitting threads should be started by hand to make sure the threads are aligned. Cross threading a fitting will cause a leak.
Follow torque specs: Most fitting manufacturers have published torque specs depending on the size of the fitting. Both overtightening and under tightening a fitting will result in a leak.
Paying attention to these simple guidelines will ensure that your fittings are installed properly.
If reading this gets you close to choosing the correct fittings, but you still have questions. The knowledgeable sales personnel at FORCE America can help answer any questions.
Please call 1-888-993-6723 to get in touch with us to help you will all your hydraulic questions.