The Perfect Hydraulic Couplers – Sometimes You Can Have Too Much Choice

Published 12 May 2021
Quick-connect hydraulic couplings

Speak to any couplings manufacturer or couplings supplier specialising in automotive, aerospace, manufacturing, or heavy industry and it’s likely they’ll agree – choosing the right hydraulic connectors and fittings can be a complicated business.

The lack of consistent international standards for hydraulic coupling connector threads and diameter dimensions causes confusion, and the sheer variety of use cases and working environments mean that you need to be careful in selecting the right hydraulic connectors.

You need to choose the connector made of the material best able to safely handle the corrosion, vibration, temperature, and pressure of your working environments.

It’s important to take a look at the different types of hydraulic connector fittings available and also the range of materials they’re made from, so the next time you speak with your hydraulic connector and hydraulic hose supplier, you’ll know exactly what to look out for.

Why Use Hydraulic Connectors?

Hydraulic connectors connect hoses, pipes, and tubes to pumps, valves, or cylinders so that hydraulic fluid can flow through the system without leaking.

Ideally designed to withstand high pressures and remain completely leak-resistant it’s essential that hydraulic hose fittings are long-lasting, flexible, and reliable.

Anything other than high quality, high reliability, and long-life connectors can lead to unnecessary repairs and downtime, suboptimal tool and machinery performance, and a limited hydraulic system life expectancy.

Put simply – you need your coupling to be ultra-reliable. Anything less than the exact fitting made from exactly the right material and you’re running unnecessary risks.

Selecting the right connection type

Despite the lack of universal convention, when it comes to threads and seals there are a number of commonly used connector types each offering pros and cons depending on where they need to be deployed:

  • Joint Industrial Conference (JIC) flares and National Pipe Thread (NPT) connections have been in use for decades. A big advantage of both is the great volume and variety of products available. They’re popular across pneumatic and hydraulic systems, as leaks can be easily fixed by simply tightening fits. However, that does run the risk of causing cracks if the fittings are overtightened.
  • O-Ring Face Seals: Seal surfaces with an embedded seal that mates to flanged tubing or hose fittings to minimise leakage. As required pressure ratings have increased so has the popularity of O-Ring Face Seals, as neither JIC fittings or NPT threads are recommended for higher pressures, especially in high vibration applications.
  • Inch Compression Fittings: Quick, easy connection with minimal tooling. Despite the very limited range of hose connections, inch compression fitting is the most common and versatile connection – and the most suitable in extreme temperature and pressure.
  • Metric Din Hydraulic Fittings: Europe’s most common hydraulic fitting style is ideal for use with metric-sized tubing and when reuse is important. Newer versions of the Metric DIN 24⁰ Bite Type included an elastomeric seal for better sealing, reusability and an ability to work at higher pressures.
  • Four-Bolt Flange: Flange connections are especially suited to conditions with large hose sizes, pressures over 3 ksi and limited working room. Outstanding vibration resistance and reusability. A trusted, reliable flange

As well as ‘fitting type’ it’s also important to consider what the fitting is made of and how durable it will be in the context of operating pressure and temperature, the hydraulic fluid used, corrosive environmental conditions, and the hydraulic hose size and flow.

Of course, you’ll want your fitting to be as strong and long-lasting as possible.

While plastics have higher resistance to corrosion than metals, the fact that they’re weaker and less durable makes them less suitable for hydraulic systems in manufacturing, engineering or heavy industry.

This is why most fittings you see in the industry are made from stainless steel, brass, aluminum alloys, and carbon steel.

Choosing the right material for your hydraulic connectors

The four common metal materials used in hydraulic coupler manufacture are:

Stainless Steel: Stainless Steel is excellent at resisting corrosion either from fluids or the external environment. An alloy of steel that contains more than 10.5% chromium, with a temperature range of –254°C to 649°C and with fittings often rated to 10,000 psi (up to 20,000 if specially designed) stainless steel is a tough and long-lasting option.

Though steel fittings are usually more expensive than hydraulic connectors made from other materials, their reliability in a wide range of environments has made it the ideal choice in oil, gas, and offshore equipment, marine, chemical processing, food manufacturing, and a whole host of other industries.

Carbon Steel: Carbon steel is durable, strong, and has high heat resistance. An alloy of iron and carbon, and often alloyed with other metals to improve its strength, carbon steel has a temperature range of –54°C to 260°C.

A Trivalent Zinc external coating is used to enhance protection from salt and fertilizers in agricultural applications.

A lower-cost option, carbon steel is commonly used across arduous, high pressure, high such as agriculture, construction and heavy industry.

Brass:  An alloy primarily of copper and zinc, brass has moderate strength and toughness.  With a temperature range between  –198° and 204° C, it also has good corrosion resistance with good ductility at high temperatures, though it’s not recommended for temperatures over 200° C as it softens and weakens. Only able to stand pressures to 3000 psi, most brass fitting applications are rated for lower pressures.

Aluminum: Deployed where a lightweight is critical – such as in aerospace, the military, and automotive industries – corrosion-resistant aluminium has a temperature range between –198°C to 204°C.

Untreated aluminum has low tensile strength and tends to be used for its corrosion resistance and lightweight in low-pressure applications. To improve strength and hardness it is alloyed with zinc, copper, silicon, and manganese for strength. Heat-treated aluminum alloy fittings can reach a pressure rating higher than brass of 4000 psi.

Technological Advances and Technical Advice

Typically, and sensibly, most industry verticals have tended to stick with the fittings and connector materials they’re always been familiar with. And why not? Who wants to stock every connector option, in every material, just in case?

When it comes to new designs and products through the introduction of innovative new design and new high performance, low-cost materials has got to be a good thing.

For advice on the hydraulic connectors and the hydraulic hoses and fittings right for your business, now and in the future, it’s best to speak with a proven and professional international couplings manufacturer.

Call today and we’ll tell you exactly what you need to know to get the toughest, most durable, and most precise hydraulic connectors for your business.

Share news article