« Roll up the map of Labor Britain - We will need it not (paraphrase of the younger Pitt)) | Main | "Can the US win in Afghanistan?" IQ Squared Debate - 2009 (Republished 12/15/2019) »

14 December 2019

Comments

Feed You can follow this conversation by subscribing to the comment feed for this post.

Just some guy

Fiberglass composite is very strong. In this case it is most likely it is an epoxy resin with a silane coupling agent added to bond to the glass.

Immediate technical issues I can see:

Moisture over the long term can permeate through the resin, and where there is too much water plus mechanical stress, slowly break the molecular bonds made by the coupling agent from the glass to the epoxy (or whatever resin is used). Polymers can take up a surprising amount of water, don't be surprised to find as much 0.01 % by weight water for some resins.

Polymers degrade under UV radiation (sunlight), get oxidized, and weaken. This is true even of polymers which were cured with ultraviolet radiation. You can add UV protective additives such as carbon black to extend the service life. But it does not seem to be the case in this example.

The composite will be totally inert to propane, and the permeation rate will be negligible.

So. These are fine, but I would not store these examples permanently outside in the sunlight, or floating in water for months at time. I would obey the expiration date religiously.

walrus

Watch the videos of hexagon ragasco composite tanks - perfectly safe, light, convenient but pricey.

Fred

They are generally a multi-layer composite and blow molded liner. They've been around for some time and are DOT approved. Not sure of the cost difference with aluminum or steel tanks. They aren't going to have corrosion issues, other than non-stainless fittings.

Andrei Martyanov (aka SmoothieX12)

They should be OK, because fiberglass parts, granted cured differently, are widely used in aerospace--either pure fiberglass, or sometimes inter-layered with polyaramids (aka Kevlar)--and withstand surprisingly high loads. Let's put it this way--in high thousands PSI. Any B-737, 777 or Airbus 320 or 350, or Bombardier or any other modern aircraft contain very many fiberglass parts which are subjected to the extreme conditions of flight and I never heard of them failing.

J

There was a recall of composite tanks back in 2013, the company in question out of Tennessee called Lite became insolvent, and had the only recall. Its competitors didn't seem to have the same safety issues.

The 2013 article was updated in 2017

https://www.passagemaker.com/trawler-news/lite-composite-gas-tanks-recalled-company-insolvent


J

Here was the original recall notice by DOT back in 2013

http://static-passagemaker.s3.amazonaws.com/wp-content/uploads/2013/07/Emergency_Recall_Order_The_Lite_Cylinder_Company_Inc.pdf

Fred

Just some guy,

How's moisture getting in when the tank is under pressure?

J

Are you considering using them in your patio grill setup?

Barney

I would be concerned about fire safety..here is what Viking says...

Ours are by far the safest propane gas cylinders available. Unlike a metal gas tank, a Viking Cylinders tank will not BLEVE in a fire. BLEVE is the technical abbreviation for Boiling Liquid Expanding Vapor Explosion. In layman’s terms this means the cylinder with not explode in a fire. Instead, the resin will burn off and the plastic liner and casing will melt. The LPG will then “breathe” through the cylinder wall and burn in a controlled manner.

SAC Brat

Fiberglass parts on the aircraft you listed are in low stress applications such as fairings, which occasionally depart the aircraft. For stressed applications such as pressure vessels (fuselage) and wings carbon fiber layups are used. Every aircraft mentioned has a Structural Repair Manual that identifies all the materials used, their locations and typical repairs. Every scratch and dent has to be inspected and tracked in maintenance records.

A problem with any of these composite materials in aircraft is if moisture gets inside the material and freezes at altitude the material will disbond. With the A350 Airbus came up with some clever damage inspection tools.

PavewayIV

Safe, tough, but only 15-year life. Can see propane level (kind of) through translucent fiberglass tank. Requires quick reinspection (visual only) and sticker every five years, but does not involve valve removal/replacement like metal tank. 17 lb Viking tank is 10 lbs empty, 22lb tank is 12 lbs empty. Compare: Steel 20# tanks are 17 lbs empty.

You could get a Viking 22# tank filled for more propane/less weight than steel 20#, but slightly taller. Plastic handle more ergonomical and nice in cold weather, plastic base is flat and won't rust. Problem in some tank holders expecting rounded base. Con: cost, refill only today. COSTCO was considering exchange program using composite cylinders but have heard nothing yet. Hexagon/Viking the only ones I've heard of.

17 lb. $120, 22 lb. $134 avg. good retail price, e.g. Bigshrink (big boat wrap & supplies) never used - no endorsement.

India and China will be pushing their versions soon.

Marginally useful detail:

People don't seem to report any UV problems. (Just some guy: Hexagon/Viking uses Ashland DERAKANE 8090 polyurethane-modified epoxy vinyl ester resin. Same resin I use on my dog to keep its coat shiny and waterproof.)

The video you linked above, Col, is for the now-defunct Lite Cylinders of Tennessee. Note the fiberglass two-piece construction, with top and bottom glued together - that was the source of their problems that drove them out of business. Lite did not use tank liners - it was just the wound fiberglass. They also had corrosion problems with the steel valve seat and many Q/C and testing 'issues'. Lite used distinctive tall, rounded rectangular cutouts in their cheap outer cases - all were recalled.

Lite bought the North America manufacturing and marketing rights to that design from Composite Scandinavia AB, who made them in Sweden. Composite Scandinavia was later bought out by Hexagon (Norway) who closed the Swedish plant in 2012 and manufactured them in Norway from then on based on their proven designs of their other pressure tanks: tough HDPE plastic tank liner, polar-wrapped with layers of fiberglass (1-piece construction). Much more robust, tougher outer casing with leaf-like cutouts. Same basic translucent fiberglass shell, allowing you to kind-of see liquid level with the right lighting and a little sloshing.

Hexagon still makes them for worldwide distribution, but Viking (Ohio?) is their North American manufacturer and distributor and sells same product under that brand today. They're unrelated to Lite or it's 2-piece design. Viking also sell to remarketers that add their label to Viking tanks. Handle should still show Viking as manufacturer. Some kind of static electricity problems when filling a long time ago and long since resolved by fill valve redesign - no longer an issue.

Carbon fiber is overkill for a simple propane tank and would make it opaque and even more expensive. Aluminum tanks are almost as light as composites, cost slightly less, have own set of quirks.

turcopolier

J

I might but the availability is small as yet.

John Minnerath

All
I don't know, but given the cost differences and known dependability, I think I would stick with the full metal cylinders.

Just some guy

Fred @ 14 December 2019 at 10:32 PM

Moisture permeates by diffusion, the thermodynamic driving force is the osmotic pressure due to differential water content from the inside to the outside, until the polymer is saturated. So I would not let them sit in a puddle for great lengths of time. Otherwise, the moisture content of the resin will slowly equilibrate with the local relative humidity, which is to be expected.

In a fiber glass application for a sailboat's hull for example, this not much of a deterioration issue as there I think the mechanical stresses are relatively low, whereas in this application we’d cycle gas pressure from ~50 to ~320 psig from a cold winter day to hot summer day. The material is much stronger than this, so a service life of 10-15 years is believable.

Andrei Martyanov (aka SmoothieX12)

Yes, I know--I test them.

Bubba Schwartz

I worked on testing composite pressure vessels vs 12.7 many moons ago. After initial failure and subsequent redesign, they held up well. I suspect there is testing and certification documentation on the propane tanks.....somewhere.

Agro

I never had the pleasure to use one, but I'm pretty excited about the idea. Sounds like a better option.

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Working...
Your comment could not be posted. Error type:
Your comment has been saved. Comments are moderated and will not appear until approved by the author. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.

Working...

Post a comment

Comments are moderated, and will not appear until the author has approved them.

Your Information

(Name and email address are required. Email address will not be displayed with the comment.)

My Photo

November 2020

Sun Mon Tue Wed Thu Fri Sat
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30          
Blog powered by Typepad