Hydraulic Fittings Confusion (2024)

FAQs

Can you over tighten hydraulic fittings? ›

Properly sealing a hydraulic fitting is crucial during assembly. Over-tightening can damage the seal, stripping threads or crushing an O-ring, causing the fitting to crack.

Missing or damaged O-ring, or over/under-torqued fittings can also cause leaks as the seal will not align properly. Over/under torquing can lead to damaged threads, which almost certainly leads to leaks.

Measuring the Outer Diameter of the thread - place the ID/OD caliper around the threads so as to obtain a snug fit. Measuring the Inner Diameter of the thread - insert the caliper into the fitting so you can obtain the correct measurement, and match it to the data charts provided by the manufacturer.

SAE and JIC fittings are similar in that they are both flared fittings. However, they are not the same, and the primary difference is their seat angles. While SAE flare fittings have a 45-degree angle, JIC flare fittings have a 37-degree angle.

Once aligned, tighten the nut until it is "firm" against the washer and o-ring, with the nut becoming snug with a feel of metal-on-metal in less than one revolution. Over-tightening causes as many leaks as under-tightening.

Instead, among the short or mid-term effects of hydraulic oil contamination one of the most frequent is the failure of O-rings and seals hit by contaminant particles which flow into the fluid under pressure: this is a typical root cause for leaks.

Most causes of seal failure are the use of the wrong size seal, inappropriate clearances between the seal and the surface, corrosion of the seal, excessive wear because of abrasive fluid contamination, poor alignment between the rod seal and the rod, and improper installation.

For pinhole leaks or slightly larger, or if you have a leak at a fitting joint, plumbers putty is the simplest way to plug it and is widely available both online and in-store at DIY and home improvement stores. Generally speaking, it consists of two components that when mixed together form a strong waterproof seal.

JIC (or Joint Industry Council) fittings, defined by SAE J514, are compression fittings machined with a 37 degree flare seating surface and parallel threads. They are commonly manufactured in nickel alloys, brass, carbon & stainless steel. JIC Fitting hydraulic connections are common in most fluid power systems.

Society of Automotive Engineers Thread (SAE)

What is the difference between L and S hydraulic fittings? ›

What are the differences among S, L and LL series? They distinguish themselves from the working pressures that they can tolerate. The S series fitting can withstand pressures ranging from 315 to 630 bar. The L series fitting can withstand pressures of up to 315 bar.

JIS stands for Japanese Industrial Standard and is used for threads on hydraulic fittings. To assist with identifying this type of thread we have compiled the following guide: JIS Toyota has a JIC type seat with a BSP thread.

Connecting AN fittings JIC damages the advantages built into the AN, degrading performance back to the level of JIC and resulting in a wasted investment.

Thread the hose end or adapter nut onto the fitting until it cannot be tightened by hand any further. Lightly tighten the nut with a wrench (approximately 30 in. lbs.) making sure it does not bind; this is also known as tightening until wrench resistance.

Once disassembled, if the tubing is yet married to the fitting, inspect that union for signs of over-tightening. The tubing will bulge and stick inside of the fitting if the ferrules are overly secure.

Under-crimping can cause the end to blow off during operation, and over-crimping can crush the hose blocking fluid and weakening the construction. Crimping errors might not always be visible to the naked eye, so always check the crimp specs with a caliper before approving the finished product.

Over-tightening your valves or tube fittings is, quite simply, not good for them. It stretches and warps them beyond the limits of their intended tolerances.

Most importantly, however, high fluid levels could disrupt flow, an action needed to transfer energy through a hydraulic system. Fluid flow cools system components, lubricates surfaces, removes contaminants, and can seal running clearances to minimize internal leakage.