Epoxies versus Heat Shrink Sleeves Cost AnalysisThis is a fairly common question that comes up from contractors: which is cheaper epoxies or shrink sleeves? As with just about every question that comes up, the question really deserves a close, in depth analysis. The truth is, I distribute two part epoxies (Powercrete and Denso) and I distribute heat shrinkable sleeves (Covalence formerly called Raychem). I am very familiar with both products including their installation procedures and their material costs. For the sake of this comparison I'm looking at our standard wrap around shrink sleeve designed for ambient temperature pipelines. I'm also looking at a one of the most commonly used, hand applied two part epoxies on the marketplace.
Quick disclaimer: each product technology has its own unique set of technical advantages and strengths -- and each has its own unique set of challenges. This article is dealing purely with the cost aspect.
In both cases I'm going to look at something simple like a 12" pipe. I'm also going to assume an FBE coated line where the standard cutbacks are around 2-3 inches per side.
So the basics first, Material Cost:
List price of 2 part epoxy in a 25-30 mil thickness: ~$11.80 per field joint
List price of a standard WPCT shrink sleeve in a 100 mil thickness: ~$11.60 per field joint
In addition, that epoxy cost is based on getting several field joints out of a single two part epoxy kit. If there were factors that led to the inability of the installer to be efficient with the epoxy, that cost per field joint could double or even triple. What are the factor that could cause an inefficient use of the epoxy (and thus a dramatic increase in material cost)?
- a right of way that doesn't allow for multiple field joints to be coated within a window of a few minutes
- hot temperatures that cause reduced pot life of the mixed epoxy
- crews not working quickly enough to use epoxy prior to cure
- ambient conditions requiring multiple coats of epoxy to meet specification
WPCT can be installed on a wire brushed pipe surface in order to create a surface that is free of oils, greases and foreign material.
Epoxies must be installed on a grit blasted surface with the proper anchor pattern in the steel.
Wire brush vs grit blasting - I have to believe the cost advantage here goes to shrink sleeves
This one can get a bit tricky as there are so many factors. Looking at preheating the steel and wrapping and shrinking the sleeve properly, I'd estimate an installation on 12" pipe at ~4 minutes.
Installation time for the epoxy? I honestly can't say as it will be heavily dependent on installer skill, ambient temperature, cure times, thickness applied per coat and how well that specific epoxy is hanging on the pipe.
Install time - Again, I have to believe the cost advantage goes to shrink sleeves here.
With shrink sleeves there are certainly things that can be (and should be) on an inspectors radar. The inspector needs to be certain the pipe is being properly preheated prior to wrapping the sleeve. The inspector needs to give a visual inspection to make certain there are no cold spots and that the sleeve shows adhesive flow on all edges. If there are cold spots or if there is a lack of adhesive flow, the crew will need to reheat that shrink sleeve and correct those issues which can take 2-3 minutes.
With epoxies, the inspector needs to make sure that the coating thickness is correct and meeting the specification. The inspector needs to be certain that any icicles are within the end users tolerance levels. The inspector needs to be certain there is no cracking. In cases where corrective action is required, the crews will need to remix more material, reapply it properly and if necessary add more than one coat to bring that field joint up to spec.
Inspector issues: Red flags on a shrink sleeve require a few minutes of time. Red flags on epoxy are generally going to require more material (cost) and time. The cost advantage here must go to shrink sleeves.
Shrink sleeves by their very nature are very, very tough. Beyond that, installers require no special equipment or training in order to properly apply them. Every box includes a detailed installation instruction and all of the most important aspects of the coating (thickness, seal ability, etc) are outside of the installers control. Shrink sleeves are very difficult to accidentally damage, and as a result, repairs are incredibly rare.
Epoxies can require repairs more often. Jeeping the field joint can cause previously unseen holidays to appear. Bugs can fly into the epoxy prior to cure. Brushing up against the field joint prior to cure can cause damage. Grass or pine needles or dirt or dust can be blown into the coating by the wind. Any of those can require repairs. Every repair requires more material be mixed which results in a higher material cost and a higher labor cost.
Repairs: Advantage has to go to shrink sleeves on this one.
So there you have it. By my estimation, looking at a standard 12" pipeline, shrink sleeves are going to be less expensive in every single aspect; including material cost, labor cost, repair cost and surface prep cost. I'm trying to figure out: why does it seem like a 'commonly accepted' fact that two part epoxies are a more cost effective option than shrink sleeves? I do not know (though I would say that when spray applying epoxies; this picture might look a bit different, but that is outside of my own personal expertise so I can't honestly comment on it).
Keep in mind, I understand completely that there are some specifications out there that allow ONLY heat shrinkable sleeves. I also know there are specifications out there that allow ONLY two part epoxies. My focus here is simply to say: if you are working on a project that contains an allowance for either technology; it is absolutely, positively worth your time to consider how each product technology (shrink sleeves and epoxies) will impact your profits on the line. Looking at all of these considerations, one option could make for a job that is dramatically more profitable than the other.