Degradation of Glycerin

[aspearin1]

I am in the process of designing a flow test loop using glycerin as a standard fluid. The stand will be dedicated for pure glycerin only, so the plan is to leave lines and tanks filled when not in use. Should I expect significant degradation of the fluid or line components from prolonged exposure? Is there a metric showing if or how much water pure glycerin can scrub from the air in humid conditions? Microbial growth? To maintain the stand properly, viscosity and density need to be readily controlled. If I can predict a degradation of these properties, then I can devise a fluid change-out plan and cost estimate.

aspearin1

 

[nbucska]

Yes, glycerin can adsorb water. You have to define what is
acceptable and design the measures to assure that the
water adsorption is controlled.

I experienced microbal contamination of diluter glycerin --
I don't know if it may be a problem in the case of higher concentration.


<nbucska@pcperipherals.com>

 

[25362]

nbucska is right, glycerol (aka glycerin or glycyl alcohol) is hygroscopic and it could absorb atmospheric humidity. The viscosities of glycerol-water solutions at 25^oC are given in the CRC Handbook of Chemistry and Physics. This book also shows the viscosity variations of pure glycerol with temperature.
It has been reported that glycerol is so hygroscopic that when having a film on the skin and the air's humidity is less than 65%, it may absorb the moisture from the skin drying it.

 

[aspearin1]

Thanks for the input. Is there chart or reference eluding to a rate of water absorption for glycerin at a range of relative humidities? I'll be looking at long term storage of nearly 80 gallons, so I'll need to size appropriate environmental controls.

aspearin1