Hydraulic hose guide: selecting the right hose with STAMPED

Hydraulic hose guide: selecting the right hose with STAMPED

Choosing the wrong hose not only carries serious safety risks but can also result in preventing premature failure and expensive downtime. To avoid these issues, get it right the first time. Use the STAMPED acronym to make sure you get the right hose assembly.

STAMPED stands for:
Size
Temperature
Application
Material
Pressure
Ends
Delivery

Here’s a look at each of these critical areas of information that you’ll need:

Size

Understand dash numbers. This is a measuring system specific to hydraulics. The dash indicates the hose I.D. in sixteenths of an inch, though there are exceptions, as noted in the table.

Hydraulic hose identification

* SAE100R5, SAE100R14, SAEJ51 and SAEJ2064

** SAE100R5, SAE100R14, SAEJ51 and SAEJ2064 only (hose I.D. is equal to O.D.)

What you should know:

• Using the wrong hose inside diameter (I.D.) will cause pressure loss and create excessive heat.
• The flow rate of the system, coupled with the inside diameter of the hose, will dictate the hose’s fluid velocity.
• The correct I.D. should be determined for the hose demanded by the application. If the flow rate of the system allows two options for a suitable I.D., select the larger if pressure allows. (Be aware that high-fluid velocities can generate excessive noise and heat to hydraulic systems and diminish efficiency.
• Your inside diameter (I.D.) should be the same as the hose you’re replacing. You’ll find this on the layline printing on the side of the original hose. If it’s worn off, then cut the original hose and measure the I.D. for size.

Temperature

Temperature in this context refers to the fluid being used and its environment. You must consider these factors:

• Maximum Intermittent Ambient Temperature

When exposed to extreme hot or cold, hoses with a rubber inner tube and/or cover can have significant change in properties. These conditions may require some hoses to be rated to a lower operating pressure.

• Fluid temperature

This refers to the temperature of the fluid being conveyed inside of the hose during use.

• Ambient temperature

Think about the temperature of the hose assembly’s environment.

• Maximum temperature

What is the highest temperature that the fluid or environment might reach, even in short durations? The hose you choose should be rated at or above the maximum ambient and maximum fluid temperature.

• Minimum temperature

What is the lowest temperature the hose assembly will endure? For a hydraulic system, consider the minimum ambient temperature. Make sure your hose is rated at or below the minimum ambient temperature of the assembly’s environment.

Note that maximum assembly working pressures will decrease as temperatures increase.

Application

This is about the conditions of use. The hose assembly you use will be determined by its application, which may be:

• High Impulse: When a hydraulic system is subjected to frequent pressure spikes.
• Low Impulse: When a hydraulic system is rarely subjected to pressure spikes.
• Non-flexing: There is no bending or flexing from articulation of the equipment.
• Flexing: You know there will be bending or flexing due to articulation or movement of the equipment.
• Vacuum: The hose assembly is exposed to negative pressure (less than atmospheric).

Other points to consider:

• If your application is outside, be aware that UV rays, salt water, air pollutants, temperature, electricity, abrasion, paint application will shorten the life of your hose assembly.
• Static charge discharge will perforate the hose tube. Use conductive tube solutions when conveying non-polar, or mixtures of non-polar, liquids.
• If your hose assembly will be around electrical lines, use hoses rated as non-conductive. Otherwise, your hoses and the fluids being conveyed will have electrical conductivity issues.
• Are there any regulatory standards your hose must meet, such as SAE, USCG, EN/DIN, or ABS?
• Never place hoses in a place where they can be pulled. Exposing hoses to axial loads when they’re designed to hold pressure and convey fluids will cause premature failure. If you have any, unusual applications get the hose manufacturer’s approval. Additional independent testing may be needed.

In addition to the points above, ask yourself these questions:

• Where will the hose be used?
• What is the equipment type?
• Is the hose material compatible with the conveyed fluid, as it should be?
• What is the type of thread end connection?
• What about working and surge pressures?
• Will the hose need to stand up to:

– Abrasions?
– Vibrations?
– Oil, and if so, which type?
– Acids?
– UV rays?
– Salt water?

• Will you have permanent or field attachable couplings?
• Does your application involve suction?
• Do you have any routing requirements?
• What is your minimum bend radius?
• Will your hose be subjected to excessive abrasion?

Material/Media

Material or media, as it’s also called, refers to what is flowing through the hose, the type and the concentration. The hose inner tube and cover material must be compatible with the conveyed material you’re using. That’s not all. Every component of your hose assembly – ends, O-rings, for example – must be compatible with the material you’re using.

Note, concentration, pressure, and temperature can impact the compatibility of the hose and fluid.

The result of failing to ensure compatibility is permeation, or effusion. This happens when a substance moves through the hose tube walls, causing the hose to degrade, blister and possibly worse. This is especially a problem if the material being conveyed is compressed gas.

Maximum Operating Pressure

What is the maximum pressure that your system will be subjected to in normal operating conditions? Determine the pressure by the system’s relief setting. Make sure the hose and hose end are not rated to a pressure less than the system’s maximum operating pressure.

Pressure Spikes

• Frequent pressure spikes that exceed the maximum working pressure will significantly lessen the life of your hose.
• Pressure spikes occur when a system has to handle a large load in a short time frame. This causes the hydraulic system’s pressure to exceed the relief setting and surpass the maximum operating pressure.
• Hose assembly working pressures must be equal to or greater than the system pressure, including pressure spikes.

Ends

This refers to termination end style, type, orientation and your attachment methods.

• Tolerances vary among manufacturers. Hydraulic hose couplings are not interchangeable. If you use the wrong coupling, then expect leaks.
• Choose the appropriate end termination for a system working pressure.
• Consider any requirements, such as vibration resistance.

Delivery

This isn’t just about receiving your hose assembly. Follow manufacturer recommendations for the hose’s maximum fluid velocity. Too much fluid velocity can result in excessive pressure loss, heat, the hose moving or whipping, and system noise.