Heat Shrink Sleeves and PP CoatingsPolypropylene factory applied line coatings have seen significant growth in recent years. Polypropylene has better abrasion resistance than PE coatings tend to and PP has a higher maximum temperature threshold than polyethylenes usually do. This makes them sometimes optimal coatings for some deep water, high operating temperature pipelines. Generally the PP is installed on top of a fusion bonded epoxy and an adhesive layer of some kind; resulting in a three layer polypropylene plant applied system. This can sometimes create a challenge when it comes to the field joint coating. Field applied three layer PP coatings can be difficult apply; particularly if looking at some form of flame spray option. There are a few heat shrinkable sleeve systems available as well, but they too can be a bit more labor intensive than standard heat shrink sleeve systems since they will often require induction heating coils for multiple steps during the installation process.
So what is the answer? Well, when you're dealing with a pipeline that will be operating at temperatures in the 250F plus range; you don't have a lot of options...you're probably going to be installing one of those labor intensive three layer PP shrink sleeve systems.
In cases where your operating temperature is going to be significantly lower than the 250F PP limitation; you do have a few options though. First of all; one of the challenges of polypropylene is that it is quite difficult for many things to stick to! PP just doesn't readily accept bonds from most other polyethylene based adhesives. That presents a real challenge in the field.
So step one, if you are not required to use (or wanting to use) a PP field joint coating system, then your first area of consideration needs to be: what can I get that will bond well to PP? Two part epoxies are not going to bond to the PP. Hot melt adhesives are not going to bond to the PP. You are going to need to look for a mastic sleeve of some kind in order to achieve a strong bond to the PP, and if you install something that does not form a strong bond, you are going to be in trouble anyway!
Which of our products utilize a mastic adhesive that will bond properly to polypropylene? We have a few.
WPCT: an ambient temperature shrink sleeve (designed for use on pipelines operating at or below ~104F.
WPC65M: a mastic temp shrink sleeve with a mastic designed to be used on pipeline operating at or below 65C.
WPC100M: a higher performance mastic shrink sleeve designed to be installed on pipelines that will operate at or below 176F (212F in some circumstances).
Any of those shrink sleeve options can be installed on polypropylene coated pipe - and any of those options can be installed on wire brushed pipe surfaces. As with any coating application - though wire brush is sufficient and acceptable; the cleaner the substrate is, the better the bond is. That is a simple fact of life.
So if you find yourself with a PP coated line that will operate at ambient temperatures and you are looking for a field joint coating solution that is simple to install and offers excellent corrosion prevention; look no further. WPC100M is likely just what you've been looking for.