More UHMW PE info please
Please take this as it is intended as additional information to make decisions based upon.
The washers in Van's kit are UHMW PE, NOT nylon. UHMW will swell a little when submerged in fuel and because of this will stain, but I'm not sure its mechanical properties degrade enough to worry about?
While delrin is a great product and machines superbly, I would be hesitant to declare it better than UHMW in this application until I saw enough evidence that it is undoubtedly better than UHMW. I've seen delrin fracture into pieces in this type application and think that if we are looking for something better then there are other engineered plastics out there more suitable for this application.
Brad,
Glad to hear that they aren't using Nylon. I got my kit many years ago. Are they still supplying import BNC bulkhead connectors? I did a quick Google search on UHMW Polyethylene. It appears that it has good resistance to gasoline. Could you direct me to a more definitive site regarding it's chemical properties?
In the link I provided in my post above, I noted that none of this company's auto manufacturing clients was interested in considering using UHMW PE for fuel system parts. Excerpt from that link below
Ticona began the study by asking its auto OEM and Tier I fuel system customers what fuels and plastics they wanted to see studied. They chose seven plastics: acetal copolymer, acetal homopolymer, PPS, PBT, aliphatic polyketone, nylon 6/6, and high-temperature nylon (HTN).
I didn't mean to alarm anyone into thinking that they should immediately remove their capacitance spacers. If they are already installed, don't fix what isn't broke. I "certainly" would not go to the trouble of building new fuel tanks. Future repair access can be had by removing the tanks and cutting access holes as needed in the rear baffle ( if you have a problem in the future).
I have another question for you guys. Does Van now make the spacers out of one piece? When I got my kit, you had to stack three 1/8" thick washers together to create the spacer. This is NOT what I would consider good engineering practice (my opinion). Beyond that, the washers I received had a 1/4" inside diameter. This required the insertion of a piece of soft vinyl tubing into the washers to take up the "slack" between the 1/4" ID of the washers and the .160" diameter of the #8 mounting screws. Has the design changed in the ensuing years?
I admit that there is a low probability of the sender plate mounting screws loosening up in their nut plates. That said, I have no faith in that .040" thick vinyl tubing being able to insulate the knife edge of the sender plate from the mounting screw for very long IF the screw was to loosen. If the any part of the sender plate contacts any other metal part of the fuel tank [such as the mounting screw], your very accurate fuel gauge will no longer work.
I would also like to hear your views as to the short comings of Delrin {aka Acetal Homopolymer} in this application. It's been used in automotive fuel systems with great success for over 15 years. I like to learn as much as the next lister.
Charlie Kuss
FYI, the link I provided considered that PPS was the best choice, regarding chemical resistance. However, it is very expensive. Also, it's superiority is that it holds up much better at temperatures above 200+ degrees. This is well above the expected maximum temperatures you might see in an RV wing [ 140 degrees ]
