Thermal Expansion RATE

[mmmbacon]

Let me preface by saying that I do not intend to recreate any of the other coefficient of thermal expansion threads available on this site...

I am looking for information pertaining to the RATE of thermal expansion of differing materials - aluminum and nylon/plastics in particular.

I am using a small hydraulic pumping system that frequently has oil leaks during installation. These are supposedly "tested" systems that had no leaks. After pressurizing "bad" systems overnight and seeing no leaks, I suspect temporary leaks due to changes in temperatures and presssures during shipping (air cargo mostly).

There is currently a molded 1L plastic tank that is fit over a machined aluminum boss with an O-ring seal. The tank neck is secured by way of a 6" hose clamp (not my design).

Since cooling would cause the plastic neck to contract more than the aluminum boss, I would expect the seal to perform better at colder temps. This leaves a difference in thermal expansion rates during aircraft decent that could cause leaks.

Does anyone have any insight as to how to calculate the rate of change of these materials?

Many Thanks,

Matt

 

[rmw]

The rate of dimensional change is going to be a function of the rate of change of the temperature of the materials. Short of shipping a printing strip recorder or similar device with the product, I don't think you can know.

It pretty cold in the cargo hold of a jet airliner. Some cargo is shipped in cargo holds that are at the same climate as the passengers (pets for example). Can you stipulate that it be shipped in a climatized cargo hold?

Not related to your product, but similar problem, it was not uncommon at all on over the road transport vehicles for them to open up "cold weather leaks" in the water connections to the 'rubber' hoses at the first really cold snap. Once retightened during the cold weather, they wouldn't leak any more unless further exposed to even colder temperatures where the tightening had to be repeated.

rmw