The Perfect Fit: A Guide to Hydraulic Hoses and Fittings
In the scheme of an entire hydraulic system, the hose and fittings you choose may not seem like a big deal. They’re an afterthought to the rest of the machinery, right?
If that’s the case, why does OSHA issued bulletins that are designed to address the risks associated with hoses and fittings?
Picking the correct hose and fitting for your job is not an afterthought for OSHA and it shouldn’t be an afterthought for you either.
Need help deciding which hoses and fittings you need for your job? Keep reading for a quick guide to picking the right equipment.
Pick Your Hydraulic Hose
You need to pick the hose independent of the fitting. Make sure that the hose is designed for your industrial needs. Then make sure that the hose and fitting are a perfect match.
So first, get the right hose.
Consider the following five criteria when picking a hose:
The hose you choose needs to adhere to federal safety standards.
In the United States, we most commonly follow the SAE standards. These standards provide specifications for the dimension and performance of your hose.
Other standards that may be used internationally include ISO, BSI, DIN, API and EN. Your hose to should adhere to one of these standards. If it doesn’t, there will be problems down the road.
No two ratings are the same. Make sure you know what each standard means. For instance, SAE-compliant hose will have a lower pressure rating than an EN-compliant hose.
It goes without saying that a hose failure, or hose whip, is dangerous. Best case scenario, a hose failure will cause production downtime for the repair. Worst case scenario, a hose failure could serious hurt or kill a worker.
When choosing a hose, the priority should always be safety.
There are a couple different pressure ratings that you need to be on the look out for.
The working pressure rating defines the normal operating pressure of your machine. You want to choose a hose that has a maximum pressure rating above your normal working pressure.
This provides a cushion. If your pressure surges, your hose will not malfunction.
You will also want to account for the burst pressure rating of the hose. The burst pressure rating is often four times the working pressure rating.
Inside diameter plays a huge role in linear velocity.
Make sure you choose a hose that has a large enough inside diameter for your needs. Smaller diameter increases linear velocity, which may increase friction.
Depending on the system you are running, a lot of friction could cause excess heat and an increase in pressure for your machinery.
Neither is good.
You’ll also need to keep inside diameter in mind when you decide on the length of your house. To help reduce friction over a long piece of hose, you’ll need to increase inside diameter.
If you buy a long piece of hose and don’t increase the inside diameter, you could have the same problems of friction, heat and pressure.
Other considerations for hose length include shrinkage under pressure, and the hose’s ability to move.
Hoses come in several different materials. Which material you choose should be dictated by the conditions where you will use the hose.
Rubber is great for hoses that experience abrasion. They don’t bend easily and are very heavy but can withstand abrasive environments. Rubber hoses have a shelf life of about ten years and should be used at temperatures less than a couple hundred degrees Fahrenheit.
Neoprene is a more flexible option than rubber. Like rubber, neoprene functions well in a wide range of temperatures.
Thermoplastic blows rubber and neoprene out of the water if the weight of your hose is a concern. A thermoplastic hose is made up of a braided nylon inner tube. This hose is not electrically conductive.
If your machine is a mobile unit, you may also need to consider outer diameter and the weight of a particular hose. A heavy, bulky and large hose will not be easy to move around.
Pick Your Hydraulic Fittings
Now that you know which hose you need for your project, let’s pick the hydraulic fittings that pair well with your hose.
Fitting are sized by the outside diameter of your hose. That’s why it’s important to pick your hose first and then match your fitting to it.
The fitting you choose for your hose should be determined by the following four criteria:
A fitting is an umbrella term for the end piece on the hose that attaches a hose to anything else. A fitting could be an adaptor, connector or coupling.
A connector is a specialized fitting that attaches your hose to a valve, cylinder, motor, pump, or other piece of active equipment.
An adaptor allows you to connect your hose of one size to a port, hose or fitting of a different size.
A coupling is a fitting that attaches two hydraulic hoses to each other.
There are seven common types of connections that you can choose from. Knowing what you need to connect your hose to will help determine the fitting.
If you aren’t sure where to start, check out the JIC fitting. They are flared fitting and were the standard for decades. They will be the most readily available and versatile fittings.
The pressure rating of your fitting needs to match the pressure rating of your hose. If you choose a fitting with a lower pressure rating, you have effectively reduced the pressure that your entire hydraulic system is rated for.
If you pick a fitting with a lower pressure rating than your hose, and then run your system at a pressure that the hose can handle, you risk popping your fitting off.
It’s a waste of time and money to pick a fitting with a pressure rating that doesn’t match the pressure rating of your hose.
Media and Material
These two criteria need to be considered simultaneously.
What media you are running through the fittings and what the fitting is made out of need to be compatible.
Carbon-steel, and all its alloy steels, are good general-purpose fittings. Stainless steel, brass, and aluminum are other common options. An agricultural sprayer that distributes fertilizer may opt for carbon-steel, but a corrosive saltwater environment could call for a stainless steel fitting.
More Help Deciding Hoses and Fittings
Remembering all these criteria can seem daunting. Use the STAMP acronym to help you remember key factors for deciding which hoses and fittings are right for your job:
Leaving hoses and fittings to an afterthought is not worth a malfunctioning system.
Need more help deciding on the hose and fitting for you? Talk to one of our product experts today and get all your questions answered.