Leakproof Joints in Cast Iron Panels

"The gasket material used at the panel joints was asbestos rope impregnated with a mixture of red and white lead. As white lead is no longer in production due to its toxicity, we are looking for an alternative material as the sealing compound. . ."

The toxicity of asbestos and red lead apparently aren't yet problematic for food production? Yikes!

I would urge you to consider new process new materials approved for food grade.

Lead contamination into the porous cast iron is likely not remediable.

I'm not a sky is falling kind of person, but elevated blood levels have been strongly correlated with brain damage.

That's my best "protect the customer" advice.

milo

goretex rope is often used as a packing, or gasket

that, or a similar "plastic" rope or fabric may be a solution

(nylon, kevlar, teflon, etc.)

You need to consider :

1.Leak due to improper gasketing at the mating surfaces ,

AND

2.Leak due to propogation of porosities in the castings if any as the castings are pretty old.

If the porosities in castings are too bad , then just replacing the gasket may not be very effective.

You may try to block leakage due to porosity by impregnating any thin viscosity anaroebic (check with Loctite) OR even a layer of expoxy sealant or a ceramic filled epoxy or putties also known as cold welding compound (check Devcon Or Belzona Or any similar ).As the original gasket was 3 mm thick , it should allow enough room for applying any of these putties.The layer can then be ground to desired finish for putting a new gasket.

After sealing the porosities you may choose to go for gasketing with any High Temperature RTV silicone sealant (check with Loctite, Dow Corning ,GE silicones etc) or any of the materials such as Kevlar or even a PU sealant.

In continuation to previous posting.

Cleaning the castigs will have to be looked in if plugging of porosity is required, as unclean and improper sufaces do not allow proper bonding of the sealing materials mentioned in the reply. Suitable enviro-friendly chemicals are available for degreasing and scale removals (Check Chemsearch) etc. Alternate procedures such as pre-heating , abrasive cleaning etc MAY have to considered depending on the actual conditinos of the castings.

Viton rubber is also a good gasket material

Why not find or have "T" shaped silicone gasket made to fit your application? There are many gasket manufacturers listed on Global Spec that you can surely find one. The top of the "T" would lay flat on the inside of the panel and the upright of the "T" would fit into the gap between panels. Joints at corners could be sealed with silicone rubber as mentioned by sb. I hope the gaskets in use now still don't have lead in them.

http://www.terpco.com/products_gaskets.php

Hi Tissa,

I believe various sorts of "cast iron panels" have been used to construct many major vehicular and other tunnels around the world for more than a hundred years (notice an early New York Times article apparently referring to early practice at

http://query.nytimes.com/gst/abstract.html?res=9906E3DD1F3BE533A25756C2A9679C94609ED7CF), and leading up to even present day uses in e.g. some challenging areas of the Channel Tunnel.

Perhaps one of the more famous historic examples is the "Holland Tunnel", reportedly nearly 100 feet deep in New York City, and with a cast iron shell and fire protection main that reportedly withstood a kind of major fire (temperatures talked about of 1,000 deg. F., see e.g. http://www.nycroads.com/crossings/holland/ and many other sites) in heavy traffic in 1949 with remarkable results. [I noticed from reports that the tunnel was re-opened in just a very few days!]

I happened to also notice while on a family shopping trip to NY/NJ before last Christmas that our trains etc. traveled through apparently many such tunnels (and many that I suspect could be quite old), and I guess you might find from the authorities/folks who maintain such infrastructure what works best for them. Incidentally, while I guess appearances might be deceiving the tunnels I saw didn't look like they were in too bad shape (and I guess it remains to be seen if what some might think are more "modern" materials/constructions will do as well).

If you decide to use "silicone" sealant, then please check and check again with the supplier as to suitability of silicone with high heat water/sugar mixtures.

While many silicones can easily withstand the temperatures mentioned, the introduction of water/steam into the discussion very quickly causes a change to opinion.

We've had three of the major silicone suppliers baulk at situations where water vapour (as steam) was in contact with their products.

What a coctail you currently have. Asbestos, red and white lead. I've still got the recipies at home for manufacture of red and white lead in an old "farm machinery maintenance handbook" published in the 1920's.

Is the heating flame in direct contact with the exterior surface? (That would explain the use of asbestos instead of jute or some other organic fiber.) If not, then could you use impregnated jute rope, or maybe an extruded tube of high heat santoprene/welvic (A type of compliant thermoplastic that behaves like hard rubber.

Maybe it's time for a more thorough refurbisment including replacing the cast iron portion.

We thank all of you for the contributions. From what we have gathered from the discussions we will try PTFE tape and RTV silicones in consultation with the manufacturers. However, we appreciate any further advice from you.

I am just now a little curious based on your conclusion thus far, do you know if the sides of your panels are by original design basically flat (while you noted sme irregularity) , or do they e.g. employ some sort of mating/facing grooves. If the latter, it may help folks more knowledgeable than I to help you to at least roughly describe any grooving.