Pressure is usually the first thing considered when selecting a hose.
And for good reason.
Pressure ratings are clearly defined, easy to compare, and often treated as the primary indicator of hose capability.
So when a hose matches the required pressure specification,
it is assumed the application is properly covered.
But in real operating conditions, pressure alone rarely tells the full story.
Because there is another factor constantly affecting hose performance — often silently and gradually:
Temperature.
Temperature changes how the hose behaves
Unlike pressure spikes or visible leaks, temperature does not usually create immediate warning signs.
The system continues running.
The hose appears normal.
Performance seems stable.
But internally, the material is already changing.
As temperatures increase, the physical properties of the hose begin to shift.
Rubber compounds can begin to soften.
The hose tube becomes brittle over time as plasticizers are leached out of the tube.
The structure becomes progressively more vulnerable to pressure stress.
This is why hose pressure ratings are directly affected by operating temperature.
The Jason Hydraulic Hose Product Guide specifically states:
“As temperatures go up, pressure ratings go down.”
That single statement defines one of the most overlooked realities in hydraulic systems.
Pressure capability is not constant.
One of the biggest misconceptions in hose selection is assuming that the rated pressure remains the same under all operating conditions.
It does not.
Pressure ratings are established under specific temperature conditions.
As operating temperature increases,
the hose’s ability to safely withstand pressure decreases.
This process is known as pressure derating.
And in many applications, it becomes critical long before operators realize it.
What pressure derating really means
The pressure derating chart shown in the Jason guide demonstrates how dramatically hose capability can change as temperatures rise.
For example, some hose types operating at elevated temperatures may retain only a fraction of their original working pressure capacity.
That means a hose originally selected with an apparently safe pressure margin may actually be operating much closer to its limits than expected.
And this changes everything about long-term reliability.
The dangerous part: the system may still appear normal
This is what makes temperature-related failures so difficult to predict.
The hose usually does not fail immediately after exposure to elevated temperatures.
Instead, degradation develops progressively.
At first:
- flexibility begins to decrease
- internal tube material “age” faster
- reinforcement experiences additional stress
Over time, this leads to: - cracking
- hardening
- reduced fatigue resistance
- loss of structural integrity
And eventually, the hose may fail under pressures it was originally designed to handle.
From the outside, the failure often appears sudden.
But internally, the degradation process has been happening for a long time.
Temperatures have an effect not only during service, but also during storage.
The integrity of the hose might be changing if stored in excessively hot environments (especially over 100°F) or in excessively cold environments below 32°F, in which the hose would need to be thawed prior to use.
Storage away from radiators, manifolds, ozone sources, etc. comes into play.
Why this becomes critical in industrial applications
In many industrial environments, elevated temperature is not occasional.
It is continuous.
Applications involving:
- steel processing
- steam transfer
- hydraulic systems
- heavy-duty industrial equipment
often expose hoses to sustained heat for long periods.
The derating table included in the Jason guide clearly shows how certain hose types progressively lose pressure capability as temperatures increase.
In some cases, applications eventually reach conditions classified as “Not Recommended.”
And yet, many systems continue operating in these environments without reassessing hose capability.
The mistake usually starts during selection
In many cases, the hose selection process focuses primarily on:
In many cases, the hose selection process focuses primarily on:
- working pressure
- fitting type
- diameter
- routing
While temperature is treated as secondary information.
But temperature is not just an environmental detail.
It directly affects:
- pressure capability
- material durability
- fatigue resistance
- service life
Ignoring temperature during hose selection means evaluating only part of the operating condition.
Correct pressure does not always mean correct application
A hose may technically match the pressure requirement.
But if operating temperature is not properly considered,
the assembly may already be functioning beyond its safe long-term operating condition.
And in many hydraulic systems,
that difference is what separates predictable performance from premature failure.
Because in real applications,
temperature is not just a number on the specification sheet.
It changes the entire behavior of the hose.