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FAQ on Explosion Proof Vacuums

FAQ on Explosion Proof Vacuums

Get answers to your questions regarding explosion proof vacuums.  If you do not find the answer to your question, we are more than happy to assist.  Give us a call today at 800.736.6288.

Why would I need an explosion proof vacuum?

While Ruwac has been supplying explosion proof vacuums for the past 30 years there have been many incidents within the last 5 years that have increased awareness on the hazards of combustible dust. OSHA has a new Combustible Dust Emphasis Program, Directive #CPL 03-00-008 dated 3/11/08 that clearly identifies the risks of combustible dust build up and the urgency to maintain a clean work environment. The only safe approved way for cleaning combustible dusts is with an approved explosion proof vacuum.  

What makes an explosion proof vacuum different from the vacuums we have been using?


In order for a vacuum to be approved for use in explosive environments it must be tested and certified by a third party NRTL (National Recognized Testing Laboratory). While there are many necessary components to consider, below are a few of the most important features. The vacuum must be manufactured out of a non sparking material. The vacuum must have a redundant grounding method to properly conduct any static build up during use. The vacuum must have approved electrical components for use in explosive atmospheres. All of the hoses and tools must be manufactured out of conductive, anti static components. The vacuum must not be able to create a spark from impact.

Can I use just any Explosion Proof Vacuum for my application?


Just because a vacuum has been certified as Explosion Proof, it does not guarantee that it can be used for all explosion proof applications. There are many factors to consider prior to choosing the safest explosion proof vacuum for your application. It is required that every application be reviewed and documented to insure that the correct machine is used for your application.

I am told that an Air Powered Vacuum can be used because it had no moving parts?


It is true that an air powered vacuum uses compressed air forced through a venture to produce vacuum. This process doesn’t contain any electronics or moving parts therefore it is often mislead as being suitable for explosion proof applications. Some companies even go a bit further and add some external grounding wires to try to avoid static buildup. There are still many considerations beyond a simple ground wire that must be given to insure proper safety. Items such as impact resistant materials, grounded filters, redundant internal grounding systems, conductive casters, conductive accessories and hoses, stainless steel venturies, and velocity impingement diffusers are just a few examples of safety components required according to UL. It is not a matter of opinion whether a machine can and can not be used in Explosion proof applications. Check with your local OSHA office or insurance company for a list of approved vacuum manufacturers.

Are Ruwac vacuums UL and CSA approved?


In order to offer explosion proof vacuums it is mandated by OSHA that they be third party tested for use in the appropriate designated areas. This is regulated by Classes in the US and Zones in European countries. All of Ruwac electric explosion proof vacuums have undergone thorough testing by an NRTL and are legally certified for use in Class I Div 1,2 Group D and Class II Div1,2 Group F and G atmospheres to both UL and CSA standards.

Are Ruwac Air powered Vacuums also Certified to UL and CSA standards?


Air powered vacuums contain no electronics therefore do not have a UL or CSA standard that they can be tested to. That does not mean that there are not specific guidelines on proper construction. All of Ruwac’s air powered explosion proof vacuums are built to the very same UL and CSA standards as the certified electric vacuums. The only difference is that the motor deck and switch gear is replacement with a stainless steel, grounded, anti sparking, impact resistant venturi system. We also go one step further and register each machine as self certified to ATEX standards. Only approved accessories and hoses are used with our explosion proof air powered vacuums. As previously noted air powered vacuums can often be misrepresented as explosion proof without containing any of the many necessary components required to maintain operator safety. The fact that there are no moving parts is not enough to be approved for explosion proof applications, they must be intrinsically safe.

Can I use any hoses and accessories with a certified explosion proof vacuum?


There are many different styles of hoses and tools available for all different types of applications. It is important to remember that not all accessories can be used for all explosion proof applications. It is necessary to review each specific application to maintain operator safety. Standard guidelines to be considered include: All tools must be manufactured out of conductive non sparking materials. All tools with bristles must have static conductive bristles. All hoses must have a resistance of less than >1meg ohm. It is important to understand that the longer the length of hose the more resistance that occurs. Caution should be taken when connecting several hoses together to create longer hose lengths. It is also important to make sure that your hose is conductive and not dissipative. Static dissipating hoses are not suitable for explosion proof applications. The use of proper hoses and accessories have also been tested and approved for use by a NRTL to UL and CSA standards.

Can a dry explosion proof vacuum be used for conductive metals?


Conductive metals such as Aluminum, Titanium, Magnesium, and Zirconium pose hazards that make standard dry explosion proof vacuums unsuitable for the application. Five factors (oxygen, heat, fuel, dispersion and confinement) make up what is known as the "Dust Explosion Pentagon." If one element of the pentagon is missing an explosion can not occur. When dealing with these materials, the hazard lies within the vacuum a.k.a. the confinement element of the pentagon. When you capture metallic dust into a dry vacuum, you in essence create a confined dust cloud inside. While a certified dry explosion proof vacuum does guarantee that a spark can not be generated by the vacuum, it doesn’t rule out any ignition source that may be sucked up into the vacuum. This could be a glowing ember, rusty nuts or bolts, or static build up from the misuse of a vacuum hose. The only safe way to insure that an explosion could never reach the captured combustible dust is by neutralizing 100% of the intake air. This is achieved by using a wet collector with immersion technology.

How is a Wet Immersion System appropriate for combustible metals?


By neutralizing 100% of the intake air and material in a water bath, it eliminates the hazard of an ignition source ever reaching the combustible dust. Due to the fact that combustible metals are so violently explosive, the smallest amount of static could ignite the smallest amount of material and resulting in a violent explosion. Wet systems capture and submerge the material in either an oil or water bath. The pressure of the material that enters the vacuum penetrates the turbulent water, quenching any possible ignition source. Special dispersion screens and demisting filters are used to eliminate any moisture from escaping the vacuum system. These filters return only clean dry air to the workplace.

I have aluminum fines that react with water. Is a wet system safe for use?


It is true that aluminum fines are one of the most common combustible metals used today. It is clearly defined by many associations that if the aluminum is 420 microns or smaller the only way to properly collect aluminum is with a wet collector. There are concerns that must be given when mixing aluminum with water. Aluminum gives off Hydrogen gas when submerged in water. This is a slow process that when overlooked can create a very hazardous environment. When using a wet system it is important to insure that there are safety measures such as Hydrogen venting incorporated into the main storage vessel. Dry explosion proof vacuums can never offer the guarantee that an outside ignition source would not ignite the captured material and therefore can not be used safely for the process of vacuuming aluminum fines.

What is meant by Dust Ignition Proof and is that the same as Explosion proof?


Dust ignition-proof can mean two things: That only the device used to power the unit will not generate a spark to ignite dust, such as an explosion-proof motor or a venturi on an air vac, or that the entire vacuum needs to be built so that there is no possibility of generating a spark from both internal and external sources. That said, all air vacs are dust ignition proof at the venturi, but not necessarily so inside the vacuum where clouds of combustible dust accumulate. Those clouds can be ignited if a metal object, like a nut, bolt, washer, scrap, etc. impacts the inside of a steel drum or any metal component inside the vacuum (filter caps, metal rings, steel intakes, etc.) unless the inside of the vacuum has been made to prevent this from happening. Even if the vacuum is grounded, a piece of metal sucked into the vacuum can generate a spark and ignite the dust contents.

Can a central vacuum system be used for explosion proof application?


While many times it seems to be more convenient to use a central vacuum system, there are many factors that must be considered prior to installing them for explosion proof applications. If the unit is 7 cubic feet in an inside area or larger, then it must be located outside. The central vacuum system must be manufactured out of impact resistant and anti static components. The vacuum system must include explosion suppression or explosion venting. The tubing system must be non sparking and requires frequent maintenance to insure that there is no build up of explosive dusts. There are also concerns as to the proper grounding methods used to secure each component of the system. Although central systems are extremely favorable, it is important to review all of the necessary requirements with an experienced sales engineer.

Can I run longer hoses to do overhead cleaning?


Overhead cleaning of dust is often overlooked in manufacturing facilities. While dust has migrated to the most inconvenient areas, the rule of thumb "out of site out of mind" normally comes into play. This overlooked area is often the source of secondary dust explosions, and most commonly sited by OSHA as a combustible dust hazard. When using an explosion proof vacuum for overhead cleaning it is important to maintain proper safety. Extension wands must be permanently connected so they can not come apart during use. Longer hoses must pass the minimum resistance requirements. Only conductive tools and hoses can be used.

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