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Grinding Carbide- Health and safety risks

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Grinding Carbide- Health and safety risks


 From the book Building Superior Brazed Tools     Buy the Book

Contents

The Metals

Explanation for Non-scientists

  • Air Collection Information and Equipment

  • Hardmetal Disease - Giant Cell Pneumonitis Induced by Cobalt

  • Hard Metal Disease - Properties

  • Cobalt Test Strips

  • Controlling Exposure By Filtering Coolant

  • Filter Units – Best Choices For Carbide 

  • Benefits of managing coolants 

  • Removing Cobalt (free & chelated) From Saw Grinding Coolant 

 

The Metals

Cadmium, Chromium, Cobalt and Nickel are all metals used in tungsten carbide brazing and grinding.  

1.  If you breathe in chunks of these materials they get into your lungs and can tear up the lung tissue.   This is pure physical damage.  In wet grinding it is chunks in the grinding fluid droplets.  In dry grinding it is airborne chunks. 

2. Cadmium, Chromium, Cobalt and Nickel are all chemicals as well as metals.  They can chemically react with your body to damage you.  Everything is chemical.

 3.  These metals also have different effects on different people.  This is like an allergy.    Everybody has different tolerances to different materials. 

All three of these have to get on or into your body to hurt you.

Cadmium

Cadmium is found in braze alloys.  It lowers the temperature and creates a stronger bond.  It also does something to the braze alloy to help keep the tip from breaking during impact.

Cadmium boils at 1409 degree F.   The solder melts from 1170 to 1270 F.  The torch runs considerably hotter than this.   One other factor is that Cadmium fumes before it boils just as water does.   When carbide saws are ground the solder gets hot enough to cause the Cadmium to come out and collect in the grinding coolant. 

Chromium or chrome   

Chromium is dangerous.  It is found in certain carbides in very small amounts.  It is a major part of some alloys such as Stellite.  Chromes have a very high boiling point.   It is mostly a danger during the welding of Stelliteä onto saws.  The welding process is a metal melting process.   Melting these alloys causes the fumes to get into the air.  

Cobalt

Cobalt is the matrix that holds carbide grains together.  It gets into the coolant when saws are ground.  It is in the coolant as chunks and it also dissolves into the coolant.  A lot of the Stelliteä type metals also contain cobalt.  It is not so dangerous here because it is alloyed with the other metals and does not come out as easily. 

Nickel

Nickel is also dangerous but it is maybe not as dangerous as cobalt. The State of Washington permits higher levels of nickel than it does cobalt.  Both are higher than the levels for Cadmium. 

Here are WISHA (Washington Industrial Safety and Health Act) and OSHA (Federal occupational Safety and Health Act) permissible exposure limits in mg/cu.m (milligrams per cubic meter) 

Permissible levels in air measured as milligrams per cubic meter 

Cadmium                                            

OSHA

WISHA

fume

.005

.005

dust

.005

.005

 

 

 

Chromium

 

 

metal

1

0.5

Salts

1

0.5

Cr2

0.05

 

Cr3

0.05

 

Cr6

 

0.05

 

 

 

Cobalt

 

 

metal

0.1

0.05

dust

0.1

 

fume

0.1

 

 

 

 

Nickel

 

 

insoluble

1

1

soluble

1

0.1

 

By WISHA standards .0025 is an action level.  If you exceed this level you are legal but you must take steps to reduce the exposure.  

Which is most dangerous or least dangerous depends on which agency you are dealing with.  The point is that these are all dangerous.  Nickel is maybe safer than cobalt unless you are allergic to nickel and not to cobalt.  

Breathing Cadmium, Chromium, Cobalt and Nickel as fumes, as dust form grinding or as material in grinding coolant can and will hurt you.  Breathing coolant and breathing coolant with metals in it causes short-term health problems and long term health problems.  

Cadmium, Chromium, Cobalt and Nickel in grinding mist bother everybody.   Dr. Susan Kennedy of the University of British Columbia did a study on filing rooms.  She measured saw filers against bus mechanics because the work areas were similar and the people doing the work were similar.  Saw filers cough and wheeze and generate phlegm (thick stringy mucous) two to three times as much as bus mechanics do.  In addition saw filers wet grinding tungsten carbide and filers welding StelliteÓ had reduced lung capacity.  They could not breathe as deeply or as easily.  This part bothers everybody the way smoke from a campfire bothers everybody. 

A certain percentage of the population has an allergic reaction to Cadmium, Chromium, Cobalt and Nickel.  When inhaled, these metals can kill people slowly and horribly.   Cadmium, Chromium, Cobalt and Nickel get into the lungs and scar the lungs.  They tear up the lung tissue.  The lung tissue then forms scars like scars form on the outside of your body.   Lung tissue scars do not allow for breathing.  Eventually more and more of the lung gets scarred and it is harder and harder to breathe until the person dies.   This is more like the way that smoke from a campfire bothers someone with asthma.  

Chromium, Nickel and Cobalt get into your lungs when you breathe in grinding coolant or welding fumes.  Chromium, Nickel and Cobalt are in grinding coolant in two ways.  They get in as really little particles in size from one -- one thousandth (1/1,000 or 25 microns) of an inch down to one --twenty five thousandth (1/25,000 or one micron) of an inch.  They also dissolve in grinding coolant and get into your lungs that way.  

It is pretty easy and simple to get much cobalt out of grinding coolant.  If you run coolant through a clean filter you can get out up to 90% of all cobalt.  This depends on the filter, the coolant and the whole system.  The 90% figure is what we found in our actual tests. 

Do not splash grinding coolant any harder or further than you have to.  What happens is that grinding coolant is sprayed onto the work as a liquid then the splashing breaks the liquid up into very small drops (aerosols) and this is what you breathe. 

Keep the coolant away from the operator.  Screens, shields, air intakes and cabinets can all be used to collect mist and prevent it from getting to an operator.  

There are other materials in grinding coolant that can be dangerous.  There are bits of diamond or CBN from the wheel; there is resin from the wheel and chunks of broken carbide as well as just general grit and dirt.  We found that there could be up to 75,000,000 or 80,000,000 pieces of crud in a cubic centimeter.  This would be 150,000,000,000 (150 billion) particles in a two liter soda pop bottle.  Filtering can get out over 99% of these particles. 

Explanation for Non-scientists

The situation

1.  No one really knows how any particular chemical will affect any particular individual

2.  The laws may or may not make sense but they are the law 

Laws change for reasons that have very little to do with science, commonsense or anything but popular opinion.  However they are still laws.  

Twenty years ago I could put my kids and the neighborhood kids in the back of the pickup and take them for ice cream.  Not only was it legal but I was a good Dad for doing it.  Now the state of Washington requires that all dogs in the back of a pickup be anchored to both sides of the bed.   Dogs and kids and pickups haven’t changed but the attitude of society and thus the law have changed.  

Legal Rule #1 - Do Not Fight With The Official

The inspector who visits you may or may not know how stupid some of the laws and regulations are however he or she did not make them but they have to enforce them. 

Science

People come in an amazing varsity of sizes and shapes.  This reflects their internal chemistry and gives some idea of the range of individual sensitivities to things like sunburn and industrial chemicals.   

How the Government sets standards

You take 200 rats.  100 you leave alone.  The others you start testing.  You feed them a chemical, subject them to a loud noise or fumes or heat or almost anything.  When you find a dose that reliably kills half the rats you have an LD50 (lethal dose of 50%)  This is sort of how they get the LD50 figure on MSDS sheets and other. 

Problem 1

There is a special strain of lab rats that are bred to be biologically identical.  (Think identical twins by the millions.)   However just as ‘identical twins’ are different so is each rat.  

Problem 2

Lab rats aren’t people.  However you can gain meaningful data anyway.  If you hit your hand with five different hammers and they all hurt then you can pretty well guess that the sixth hammer will hurt as well.  Something that kills rats is more likely to be dangerous to people than something that doesn’t kill rats.   

Problem 3

It is statistics and statistics works best in large numbers.   Statistics makes almost no sense in an individual case.  You can pretty well bet that a coin flip will come up heads half the time if you flip it often enough.   

Safety Rule #1

You Won’t Get Hurt If It Doesn’t Get To You 

Chemicals have to be breathed, eaten or absorbed through the skin to hurt you.  You can control breathing by face masks or by air collection.  Personally I prefer air collection.  The initial cost is higher but it works much better and it protects the equipment as well as he operator.  Clean air can well pay for itself by extended equipment life.  

Air Collection Information and Equipment

Equipment Suppliers:

 

Coppus (508) 756-8391 Millbury, MA – unique, portable dust collection systems – also employee coolers for hot areas.  Unique products.   http://www.coppus.com/ 

Dust Vent, Inc.  (630) 543-9007 Fax: (630) 543-1407  100 W. Fay St., Addison, IL 60101, Wide range of equipment and good literature.  Recommended for literature.   www.dustvent.com 

Eurovac  – Central vacuum cleaner systems and other dust collection equipment.   http://www.eurovac.com 

MAC Equipment, Inc.  (800) 821-2476 – Huge, complete catalog.  Excellent information, great source to build your own system.  Recommended for literature.  http://www.macequipment.com 

Nederman (313) 729-3344 Westland, MI –Nice literature –looks like nice overhead arm extraction equipment –good information on Do It Yourself. Recommended for literature.  http://www.nedermanusa.com/ 

Plymovent (732) 417-0808 New Jersey –good equipment –great free booklet “My Pocketguide to Clean Fresh Air”.  Recommended for literature.   http://www.plymovent.com/ 

Sly, Inc. (216) 891-3200 Cleveland, OH –Shop size central collection systems to huge industrial systems.  Recommended for literature.    http://www.slyinc.com 

United Air Specialists (800) 551-5401 Cincinnati, Ohio –Invented the original smoke eaters for bars, etc. –Good equipment –good literature and great technical help.  Recommended for literature.  http://www.uasinc.com/ 

Hardmetal Disease - Giant Cell Pneumonitis Induced by Cobalt

This gets all the publicity but it is just a very small part of the story. 

Dr. Susan Kennedy, at the University of British Columbia has recently done industrial hygiene surveys that indicate that the problems with cobalt exposure in coolants are much greater than the government recognizes.  

There is a problem with dissolved cobalt. It causes hard metal disease. (Hard metal diseases are different from heavy metal diseases although both are often linked to industrial practices.). According to Ed Chessor of the British Columbia Workers’ Compensation Board, about 1 or 2 % of the population is particularly susceptible to cobalt.  Others have put the figure much higher. They are in much greater danger than the average person is. This is somewhat similar to the fact that some people are much more susceptible to damage from bee stings. 

The safety and health issues are incredibly important and very complex. If you have any concerns you should call in a consultant from the government or a private consultant to do a hypersensitivity reaction to inhalation of particles of hard metal. Hard metal is a material composed predominantly of tungsten carbide (WC) and cobalt (Co). Hard-metal lung disease occurs mainly in workers engaged in the manufacture of hard metal, but also in workers engaged in resharpening hard metal tools (saws, drilling tips, etc.). Hard metal lung is sometimes labeled as cobalt lung, because cobalt is probably the critical offending agent in hard metal and because the same disease has also been described in diamond polishers who use polishing disks made of diamond cobalt (i.e. not really hard metal).  

Unlike most other mineral pneumoconioses, hard-metal lung does not appear to be caused principally by the reaction of excessive dust accumulation in the lungs, but it presents many features of a hypersensitivity reaction. Consequently, hard-metal lung may occur in young subjects with relatively short exposure histories. It may present (sub)acutely, with work-related clinical and radiological features similar to those of hypersensitivity pneumonitis (extrinsic allergic alveolitis). However, hard metal lung differs from hypersensitivity pneumonitis in its pathology, which is characterized by the presence in the lung interstitium and the alveolar spaces (and hence in the bronchoalveolar lavage) of 'bizarre' multinucleated giant cells with 'cannibalistic' features thorough analysis. 

Hard Metal Disease - Properties

Category           Interstitial Lung Disease

Acute/Chronic   Chronic

Synonyms         Giant cell interstitial pneumonitis (GIP)

Comments        Hard metal disease is a "giant cell interstitial pneumonitis" that affects a small minority of workers who manufacture or use high-speed tungsten carbide saw tips, drill tips, or discs. These tools are used to polish diamonds and to cut hard materials such as metals, hardwoods, and cement. The workers are exposed to fume or dust from the cobalt used as a binder in the cemented tungsten carbide metal. The usual symptoms are dyspnea on exertion, cough, and fatigue. The chest x-ray may show infiltrates, and the pulmonary function test may reveal a restrictive defect. The same workers are at risk for cobalt-induced asthma. 

Symptoms/Findings associated with this disease: chest tightness, clubbing, cough, diffuse infitrates, interstitial pattern, dyspnea, exertional fatigue, inspiratory rales, restrictive defect, sputum production, weight loss 

High risk job tasks associated with this disease:

Heat or machine cobalt alloys

Manufacture cemented carbide materials or tools

Use cemented carbide materials or tools  

Hazardous agents that cause this disease:

Cobalt

Tungsten carbide 

http://hazmap.nlm.nih.gov/cgi-bin/hazmap_generic?tbl=TblDiseases&id=256

http://hazmap.nlm.nih.gov/ 

An Explanation for non-scientists 

Cobalt In Tungsten Carbide Is Different Than Cobalt In Talonite ®, Stellite ®, Etc.  Cobalt is the same in both uses but in Talonite ® it is chemically locked up to other elements while in tungsten carbide it is unlocked and can move freely. 

In old tungsten carbide grades it was used as an element.  In welding alloys and modern carbide grades it is used as an alloy and is chemically locked up. 

Atoms have electrons that work sort of like the hooks and loops in Velcro.  If the two halves of Velcro as separate then it can pick up fuzz, etc.  If the two halves of Velcro are pressed together then it won’t pick up anything.  

If an atom has eight electrons in the other shell then it won’t bond.   If it has fewer than eight then it will bond.  (Hydrogen won’t bond if it has two but will bond if it has one.) 

Hydrogen and Oxygen are gasses.  Once they bond together they become water which has entirely different properties than either gas. 

In tungsten carbide cobalt is used as a binder as pure cobalt.  It melts and glues the carbide grains together like hot melt glue holding marbles together.  It never reacts with anything so it still has the capacity to react. 

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