If you're purchasing hydraulic hoses, the chances are that you're going to need their associated hydraulic hose end fittings or couplings as well. That's because different hoses come in different lengths, diameters, pressure ratings and need to be compatible with the fluid they carry. Fittings help you adapt hoses to your hydrostatic system, allowing you to extend a hose range and attach them to different hydraulic pumping and actuation components.
: Hydraulic hose end fittings for hydraulic systems
Materials used for Fittings
Hydraulic hose end fittings are manufactured using a variety of materials. The one you choose depends on your application and the desired performance.
You'll find that metals are the most common material chosen for manufacturing fittings owing to their durability, strength, and heat resistance. Steel is the most widely used metal as it satisfies the requirements mentioned above, suitable for high-pressure applications. If you're looking for more resistance, then you might want to consider stainless steel variants for fittings. Brass and aluminum are also used to combat chemical resistance but don't have the strength that steel brings. However, you can use them for low to medium-pressure applications. They have the advantage of being inexpensive, allowing you to minimize the cost of hydraulic assemblies.
Plastics will provide the best corrosion resistance; however, they are not as strong or durable as metal fittings. They are the least expensive out of all the fittings but can only be used for low-pressure applications.
Types of Fittings
Like hoses, fittings also come in different sizes and are made of different materials. Most commonly used fittings include those made from plastics, stainless steel, and brass. The one you choose depends on your application, the durability you desire, the operating temperature, and the strength of the sealing you require. The two most common types of hydraulic hose end fittings are permanent and reusable.
Permanent Hydraulic Hose Fittings
As its name implies, this type of fitting permanently attaches to a hydraulic hose. They consist of two parts: the stem and the ferrule. The stem is inserted into the inner tubing of a hydraulic hose while the ferrule encloses the outer cover. The assembly is then placed in a crimping tool that applies even pressure on the outer ferrule, deforming it and sandwiching the hydraulic hose end between the two components.
The fitting can come in two different variants. It can be a two-part component with the stem and ferrule separate from each other, or it can be a single component where the ferrule is a permanent part of the stem. Additionally, you'll have to consider if your hose requires skiving or not. That's when part of the outer cover is shaved off so that serrations inside the ferrule can bite into the metal wire mesh or spiral for a tighter seal.
Reusable Hydraulic Hose Fittings
Reusable or field attachable fittings become a part of hose assemblies without the need for a crimping tool. They are most commonly used in cases when access to a crimping tool is not available, the hose assembly does not require such a strong seal to withstand pressures, or the hose is customized to cater to a specific application. Instead of a ferrule, they have a collar placed on the hose end. The stem gets threaded into the collar and tightened to create a seal. The stem and collar can be unscrewed to retrieve the fitting for future use.
Factors to Consider When Selecting Hydraulic Hose Fittings
There are many standards like the NPT/NPTF, BSPT, SAE, ISO, DIN, Metric, among others, that define how the fittings get attached to hydraulic components. For example, the NPT/NPTF standard, the most commonly used in North America, outlines that the threads need to be tapered for a strong, leak-proof seal. Make sure you identify which standard fitting is required. You may need to consider flare angles, O-ring type and size, and seat diameter before selecting the appropriate fitting.
The fittings' temperature rating depends on the material the fitting is made out of and the seal type. O-rings also have a temperature rating. If you operate at higher than that temperature, the O-ring deforms, causing leaks around the fitting.
Different fittings are rated for different pressures. Fittings that seal with an o-ring provide a higher pressure rating than metal-to-metal contact fittings, given that the medium they carry is compatible and the operating temperature does not exceed the rating of the O-ring. When tightening fittings, make sure you don't over-torque them, as this may damage the threads and cause leaks.
The medium the hose assembly carries has to be compatible with the fittings you choose. Petroleum or synthetic media can erode o-rings if they're not compatible, causing hydraulic hose failure. Make sure you read all the technical specifications for them before installing them.
Popular Hydraulic Hose Fittings Manufacturers
There are many manufacturers out there that provide reliable and durable hose end fittings. Some of the most popular are mentioned below.
Parker is one of the leading hydraulic hose end fittings manufacturers in the world. The company boasts a range of products that are applicable for numerous assemblies.
Eaton is a mega-conglomerate with many subdivisions. Two of its subdivisions, Aeroquip and Weatherhead, specialize in manufacturing hydraulic hose ends for the aerospace industry and general use, respectively.
The good thing about Gates is that they are fluid transfer accessories manufacturers and a solutions provider for their clients. They have a massive catalog of various hydraulic hose end fittings as well as complete hose assemblies.