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Posted By MICHAEL T
We have to strip down a large (20 tonne) engine / generator which contains viton seals. I understand that viton when burnt gives off hydrocloric acid in a gas or liquid form. As the engine has now obviously cooled would the viton still present a significant risk.
- Mike
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Posted By MICHAEL T
I forgot to mention that the engine has been involved in a serious fire.
MT
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Posted By Chris G Hydrofluouric acid could still be present when cooled and would still be a significant hazard given the nature of HF. Look at the MHDS for HF somewhere such as the www.vwr.com website to get an idea of the hazard. Even at a couple of percent concentration serious chemical injuries can occur and treatment is by antidote gel (as 1st Aid) and injections (painful) by a A&E department. Worst case injuries can require amputation or even prove fatal, so treat suspected HF contamination seriously. Also beware that HF and HCl fluoride & chloride sound similar to a tired A&E intern. The treatment for the two though is completely different. Chris
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Posted By Merv Newman
Sorry, but lets be sensible. HF (admittedly an extreme nasty) is one of the components involved in the initial polymerisation to make Viton. The basic synthetic rubber is then mixed and milled with other components and then cured for many hours at high temperature.
Just handling Viton carries, in my humble opinion, zero risk of HF exposure. I've done it many times. Raw, uncured and cured. And I still have all my fingers.
However, waste Viton should not go for incineration. That could (could) release residual HF.
Merv
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Posted By Jim Walker You can get HF where seals have been burnt (heated in reduced O atmosphere). Known hazard in the scrap car industry -or it should be!! Seriously nasty stuff as you don't get much pain until too late. See http://www.hse.gov.uk/pubns/chindex.htm and then relevant PDF file
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Posted By Bill Parkinson
As a chemical engineer and also a chartered safety & health practitioner who has worked with HF you should be wary of direct skin contact with any flurolastomers or substances containing HF. This is especially the case of those substances which have been involved in a fire. There is a risk of HF being formed due to the uncontrolled heating effect from fires and therefore you would err on the side of caution.
You may want to speak to the chemical hazards division (or whatever they are called now) in the HSE (think they are based on merseyside still).
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Posted By Heather Collins
As someone who works in the rubber industry in a company which manufactures viton products, I feel I might know something about this!
As Merv says there is little or no risk from handling viton (or other fluoroelastomers - viton is Du Pont's tradename) uncured or cured under normal circumstances. However the curing temperatures used in the industry are not likely to be anywhere near that reach in a fire.
Considerable experimentation has been done by those who manufacture these polymers to study the breakdown products at the temperatures reached in a fire. Du Pont certainly publish results of such tests in their product data sheets. They have concluded that HF formation is a definite risk. Therefore I would certainly say that there could still be a residual risk with these O-rings and proper precautions will be necessary.
Viton is a relatively expensive polymer and will only be used where high temp/high pressure conditions demand it - O-rings and seals is a typical application - so you will not find it in widespread use. However its use is more common in cars now than it ever has been and the comment above about scrap cars is very relevant.
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Posted By Chris Packham
Viton is used for certain types of glove - expensive but necessary when handling certain hazardous chemicals. In fact Viton is the only material that will provide long term protection against solvents such as xylene and trichloroethylene (but is useless for acetone!).
So Viton as such is safe. The problem arises when it is heated beyond a certain temperature (I believe this is >200 deg. C) when it decomposes and hydrofluoric acid is produced. This is why Viton gloves should never be incinerated.
This means that any seal, o-ring etc. where it is suspected that exposure to high temperature has occurred must be treated with caution.
For dilute (10% and less) concentration a relatively thick nitrile glove will provide adequate protection. For anything above this the correct glove material is butyl.
Chris
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Posted By John Murgatroyd
HUMAN HEALTH EFFECTS OF OVEREXPOSURE TO VINYLIDENE FLUORIDE-HEXAFLUOROPROPENE POLYMER
Skin contact with uncured polymer may cause skin irritation with discomfort or rash. Significant skin permeation and systematic toxicity after contact appears unlikely. There are no reports of human sensitization.
Eye contact with uncured polymer may cause irritation with discomfort, tearing, or blurring of vision.
Inhalation of fumes from burning polymer may cause temporary lung irritation effect with cough, discomfort, difficulty breathing, or shortness of breath. Higher exposures to fumes from burning material may cause pulmonary edema (body fluid in the lungs) with cough, wheezing, abnormal lung sounds possibly progressing to severe shortness of breath and bluish discoloration of the skin. Symptoms may be delayed. Prompt medical attention is required.
Smokers should avoid contamination of tobacco products with polymer and should wash their hands before smoking.
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