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Tuesday, April 29, 2014

Road Bore Field Joint Coating with Fastest Cure Time

Which road bore pipeline coating has the fastest cure time?

    When considering cure times, there are a number of factors (which are often uncontrollable) that affect cure times.  These include humidity levels, ambient temperatures, substrate temperature and design parameters of the curing material itself.  If you are in the field, or if you are writing a specification for a pipeline project - it won't take you long to realize that you cannot control any of those factors! 

     As a result, the only way you can influence installation and cure times is by focusing on what you can control:  product selection.  If you're selecting a curable material to coat the field joints (girth welds) on your pipeline which will be involved in a road bore or directional drill; I'm guessing you already understand that extreme conditions through which you are going to put that pipe.  I'm assuming you're also aware that once it enters the hole; the pipeline is never going to be seen again.  You're going to have one shot to get that pipe properly coated and that is it.  Add in the requirement that you need a fast curing material and you might have real problems on your hand.....or will you?

     Looking through published data of one of the leaders in the two part epoxy pipeline coating business, it is very easy to determine the manufacturer predicted cure times.  Of course, they vary based on the temperature of the substrate and (mostly) the temperature of the Earth at the time and place that coating is occurring.  It is my understanding that 'force curing' most stand alone two part epoxies is a bit sketchy.  But in any case, right here in the data of "one of the fastest curing epoxies" I can see that if the temperature outside if 60 degrees F; the epoxy will need 6-9 hours before it hits its reported Shore D value of 80-85. 

     If the outside temperature is 80F, you are looking at 3-4 hours before reaching Shore D hardness of 80-85.  If it is 90F outside, that number drops to 2-3 hours.  Still a long time if you're dealing with a road bore and a limited right of way for stringing up pipe.  Another interesting fact though:  at that 90F - the epoxy doesn't reach "tack free" until 30-40 minutes have passed.  That can mean 30-40 minutes of working, reworking and re-reworking the epoxy to minimize drips, icicles and coating inconsistencies.  Tough challenge.

     So, say you are a fan of many of the physical properties of two part epoxies.  You like good cathodic disbondment.  You like the improved abrasion resistance, shear, peel, etc.  But, you can't live with the cure times.  Well I have good news for you.  Our DIRAX product utilizes a two part epoxy as the primary corrosion coating of the system (use history).  Over that, the DIRAX system offers unparalleled protection for your field joint.  Even better though is the cure time.  Since the epoxy in this scenario is not a stand alone epoxy...the option to force cure it becomes technically sound.  Given that you're preheating the pipe surface to 140F -- and then the DIRAX is contracting at 260F -- there is plenty of heat getting into that epoxy so that this system is installed in 7 minutes or less (for typical pipe sizes) and completely cured and ready to pull within about 30 minutes (ready for pull as soon as installation is completed and cooled back to ambient temperatures which could include a quench of some kind).

     So - several hours and lots of labor....or thirty minutes and minimal labor.  I don't think its close -- especially when you're dealing with a right of way issue.

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