Let's start with the oil hoses. Excavator oil hoses typically come in two types: two-layer and four-layer. The two-layer and four-layer designations refer to the number of layers of wire mesh within the hose. A cross-section of the hose makes it easy to identify the number of layers. If the cross-section isn't cut perfectly flat, making it difficult to clearly see the number of layers, you can also check the markings on the outside of the hose. The standard for two-layer hose is R2AT, while the corresponding standard for four-layer hose is 4SH. So, if you see R2AT printed on the outside of the hose, it's a two-layer hose, and if you see 4SH printed on the outside, it's a four-layer hose.
Common sizes for excavator oil hoses include 1/4", 3/8", 1/2", 5/8", 3/4", and 1". These sizes are expressed in inches and correspond to the inner diameter of the hose. Another way to indicate hose size is by dash number or dash size. This is actually another way to express tubing size, somewhat similar to how angles are expressed. You can express an angle in degrees or in units of degrees. While they appear completely different, they are actually completely equivalent. How do you convert 1/4 to -04? Convert 1/4 to 4/16. -04 means there are four 1/16 units, and -06 means there are six 1/16 units.
Now that we have an understanding of tubing sizes, we can move on to connector standards. Excavator tubing connectors generally come in five different standards: BSP, JIC, ORFS, Metric, and JIS. A relatively simple way to identify the standard is to look at the sealing surface. For example, the sealing surface of the female end of a BSP (British Standard Pipe) connector is an external cone. (Since oil pipe connectors are generally female, the sealing surfaces described here refer to the sealing surfaces of the corresponding standard female end.)
The sealing surface inside a BSP connector is mostly hidden inside the connector, but if you look closely, you can still see that it has an external cone. Some people call this a convex beak or a volcano beak, which is quite descriptive. The sealing surface of a JIC (Joint Industry Council) connector is exactly the opposite, with an internal cone. Some people call this a concave beak or a bell beak.
The sealing surface of an ORFS (O-Ring Face Seal) connector is completely flat. The name ORFS means O-ring plus flat surface, so its sealing surface is flat. The O-ring is on the male end, and since we are only discussing the female end's sealing surface, the O-ring is not visible.
Thus, the three standards mentioned above can be quickly distinguished based on the sealing surface. Next, let's look at Metric.
The nuts on metric fittings are usually removable, making it easy to see the full sealing surface. Metric fittings also have an external cone and an O-ring on the outer cone.
Finally, let's look at JIS (Japanese Industrial Standard). JIS and JIC share a similar name and appearance, with both featuring internal cones, or concave or flared nozzles. Distinguishing the two types visually is difficult. Therefore, it's important to have a complete set of thread test heads for JIS fittings and a complete set of thread test heads for JIC fittings. Tightening the test heads is essential to accurately determine whether a fitting is JIS or JIC.
To summarize, there are five types of oil pipe fittings used in excavators. Based on the sealing surface, it's easy to distinguish between BSP (external cone), ORFS (flat nozzle), and Metric (external cone + O-ring). Fittings with internal cones or flared nozzles can only be JIC or JIS. Testing the fittings reveals the difference.
