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Barcol hardness of in-serivce FRP equipment

Barcol hardness of in-serivce FRP equipment

Barcol hardness of in-serivce FRP equipment

I am attempting to evaluate Barcol hardness results from a FRP tank that has been in sodium chlorate solution service since 1995. The tank was constructed with inner corrosion barrier of DERAKANE 411 reinforced with (2) ply C-glass surface Mat.

From what I can ascertain the barcol hardness was approximately 35 when originally constructed and my average barcol hardness at this time is 39.78

What hardness value would indicate a potential problem for  this type of equipment and service?

Thanks in advance for any assistance

RE: Barcol hardness of in-serivce FRP equipment

The normal problem of corrosion is shown in part by a reduction in Barcol hardness (I assume you are undertaking the inspection to the appropriate standard). I would check the expected hardness against the manufacturers data for the cure system that was used. However it is known that full cure is not always achieved during construction and depending on the tank temperature the VE can continue to cure and achieve higher results once in service. (You can get higher results by hitting glass fibres). You don't say what the concentration or temperature is, providing it is low temperature <50DegC and the Sodium Chlorate is stable then I would expect there to be very little attack on the liner. In which case 32-40 Barcol could be a reasonable result.

RE: Barcol hardness of in-serivce FRP equipment

Having personally inspected numerous chlorate tanks, I can tell you that it is common for the barcols to increase after being put into service.  

Most chlorate tanks are not post cured prior to being placed into service.  Most Sodium Chlorate tanks (and especially those used for unloading crystal from rail cars) operate at temperatures > 165F.  This will provide a post cure during the first few days of service.

Because the chlorate is not typically agressive to the resin the post cure from service increases the barcol as there is further crosslinking that is taking place.  It appears that you are not having corrosive attack of the resin, which typically lowers the barcol rather than the increase you have seen.

RE: Barcol hardness of in-serivce FRP equipment

I agree: state of cure is dependent on time and temperature.
unless specific post-cure has been applied (in which case the records should show the Barcol value)

Note. All laboratory Barcol values are taken on a cast resin, unless the needle hits pure resin on the laminate a false value is created. Best to do many tests


Ed Clymer
Resinfab & Associates

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