Working with hydraulic systems can be a complicated task. More often, you will encounter various choices for parts that all look the same. To make your job more complicated, most of these fittings are more or less of the same quality. If you are not familiar with their difference, you tend to get whatever fits the tube that you have to connect. To appreciate their differences, here are the necessary information about ORFS, AN fittings, and flareless fittings to help you distinguish one from the other:
O-ring face seal fitting, or ORFS, is an adapter featuring a machined groove and a straight thread. It generally keeps the machine from leaks caused by an increase in pressure up to 6,000 PSIG. The O-ring is compressed between the flat surface of the tube and its body, thus acting as a tight sealant.
Many technicians prefer using an O-ring because of its zero-clearance characteristic. It means that it can be inserted and detached from the system without flexing or cutting the tubes. As such, it is perfect for valves that are frequently maintained or replaced. The sizes available in the market is between ¼-2 inches of the outside diameter.
The AN fitting is a piece of military-grade equipment used to connect rigid metal tubing to flexible hoses. Its name is an abbreviation of Army and Navy since they are the first ones to use them in the compression fitting. They are initially intended for the aeronautical industry, but through time, it was adopted as a crucial part of sea and land transport equipment as well.
Eventually, it got adapted for common industrial usage. The popular term for this industrial-grade AN-like fittings is called JIC. Despite their similar purpose and look, there is a slight difference in their shape and thread class. For instance, AN fittings have a higher tolerance for fatigue and shear strength. It also has a broader root thread radius than JIC. Another difference is that the military fitting is manufactured to meet MIL-F-5509 standards, while the industrial type is tested to meet SAE J514/ISO-8434-2.
Aside from their outside diameter and nominal hose ID, each size differs in terms of the measurement of its actual hose ID, SAE thread, and pipe thread. In theory, they can be used interchangeably, though the latter is not recommended for projects that require exact specifications.
Flareless fittings are known for their ingenious ring design, which can withstand extreme vibration and high pressure like the ORFS. They are called that way because they are often used in systems that cannot be flared or dilated.
When you buy this in the store, you will find that they often come assembled with ferrules and tube nuts made from carbon or stainless steel, thus making them anti-corrosive. Their classification is based on the amount of pressure that they can withstand. Just like ORFS, its most reliable form should be able to tolerate stress up to 6,000 PSIG.
Pressure build-ups and leaks are common problems that the installation of proper tube fittings can quickly solve. Figuring out which one to use takes experience and a keen eye. While they may be small, they are instrumental in ensuring that the machine is running smoothly. If you are unsure which one to get, ask a dependable mechanic for advice.