Preventing Explosions by Properly Equipping Engines for Use in Hazardous Locations

by New member iefox on ‎04-26-2012 03:37 AM

It has long been known that special precautions must be taken when engines are to be placed in areas where flammable atmospheres may occur. Among the more common protection methods are special wiring and emergency air shutoff valves. Over the years, a number of standards have been developed to help engineers, inspectors, and other people responsible for selecting equipment to determine what risks exist in a given area and best practices to mitigate those risks. There are many standards to help classify the risk associated with types of locations, and there are many more standards describing design techniques for hardware used in these classified locations. There are even several standards specifically written around protecting engines, but these standards seem to be less-commonly implemented than some of the more general standards related to hazardous locations, often to the detriment of safety. In this post I intend to briefly explore some of these standards regimes and the risks they address, particularly with respect to engines.

 

Where do explosions come from?

An explosion can occur where the right mixture of a fuel (dust, gas, fiber) and an oxidizer (air) exists in the presence of a source of ignition. Take away one of those three, the fuel, the air, or the ignition source, and you can avert the explosion. Equipment designs for hazardous locations - those locations where a potentially flammable atmosphere may exist - typically focus on removing one or two of those three ingredients. I'll get to that in a moment, but first, a discussion of how hazardous locations are identified.

 

Risk Assessment and Area Classification

One of the first steps in appropriately protecting against explosions is to assess the risk associated with a particular area. There are published standards to assist engineers and inspectors in performing this task. Simply put, an assessment is made of what fuels may be present in a location, how often an explosive atmosphere is likely to occur in a particular location, and how long the atmosphere is expected to remain when it occurs. With this information, areas are classified into Classes and Divisions, Classes and Zones, or Zones, depending on which standards regime is accepted in the region where the facility resides.

 

As examples,

 - A Class I division 2 location, per NEC 500, or Class I Zone 2 per NEC 505, is a location in which flammable gases, liquids, or vapors may be present but are normally confined within closed containers or systems, where ignitable concentrations of flammable gases are normally prevented by ventilation, or are nearby areas with more frequently occurring flammable atmospheres if the flammable mix may occasionally be communicated from that area.

 - A Zone 2 area, according to IEC 60079-10, is an area in which an explosive gas atmosphere is not likely to occur in normal operation but, if it does occur, will persist for a short period only.

 - Under ATEX (1999/92/EC), A place in which an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, vapour or mist is not likely to occur in normal operation but, if it does occur, will persist for a short period only.

 

Besides the frequency of occurrence, it is important to know the type of flammable atmosphere that may exist (gas or dust, both, what kind of gas, etc). The various hazardous area standards (IEC, NEC, ATEX, etc) describe different methods of quantifying and describing the characteristics of these potentially explosive mixes. In particular, gases are grouped by how easy it is to light them, what temperature it takes to cause them to ignite, and how well they continue to burn once lit. These factors are used to select Groups and Temperature Classes that selected equipment must be designed for. These assessments are typically made by the engineers laying out a plant or facility, or by representatives of the company responsible for operations at a particular site, and are later approved by the authority having jurisdiction in that region. Classification of an area allows the proper selection of equipment for that area.

 

*** Note that I mentioned more than one area classification with the words "Zone 2" in it. While the rules for area classification are generally aligned such that Zone 2 and Division 2 mean the same thing around the world, as I'll discuss in a moment, the specific equipment protection measures that are required by the standards and regulations vary significantly. When requesting a quote for equipment, it is not enough to simply specify "Zone 2," as ATEX requirements for that area are much different than NEC or IEC requirements for the same area classification. "Zone 2" by itself could even refer to a UBC seismic zone!

 

Equipment selection

Once we know what the classification of an area is, we need to select equipment appropriate for the area. This process can be fairly simple for the end user - he can look for equipment that bears appropriate marks indicating that it is suitable for the area, and he can specify his hazardous area requirements when he puts out RFQs. The temperature class, equipment group, equipment category, and the types of areas for which the equipment is designed may all be indicated on a placard. The equipment manufacturer will have placed these marks on the product in accordance with the relevant regulatory requirements for the region(s) where the product will be sold. The manufacturer typically must follow a series of design, test, and manufacturing standards, and in many cases will need to have the compliance with these standards assessed by an authorized third party, including random inspections of the product and/or production facilities.

 

Equipment Design & Risk Mitigation

Before a manufacturer places marks on a product to say that it is appropriate for an area, the product must have been designed and manufactured in accordance with the relevant standards. These standards will in most cases dictate methods of mitigating the ignition risks associated with the piece of equipment. On a diesel engine, typical (potential) sources of ignition include hot gases, hot surfaces (especially the exhaust system), sparks from electrical components, static discharge, and engine runaway or catastrophic failure due to unintentionally ingested fuel from the surroundings. There are standards from API, ANSI, IEEE, UL, FM, CSA, and IEC addressing methods of mitigating ignition risk from electrical systems, and under most hazardous location standards regimes the electrical components are required to be protected. Intake air shutoff valves are required on diesel engines, and anti-static fan drives typically are too. The big differences in equipment protection methodologies arise with respect to mechanical systems' potential ignition sources. Under NEC and IEC standards, at present, there are no protection methods described for hot exhaust systems, hot exhaust gases, or sparking gears. Under the requirements of the ATEX directive (and EN 1834-1), these potential ignition sources must be addressed. The requirement for reduced surface temperatures typically drives the inclusion of exhaust gas coolers, water-cooled manifolds, water-cooled turbochargers, and special gas-tight insulation to reduce surface temperatures. The inlet and exhaust systems are typically fitted with flame traps. Under the NEC/CEC and IEC systems, these features would typically not all be required.

The laws of physics are certainly no different between regions where ATEX compliance is mandated and regions where NEC or IEC requirements apply, and the area classifications are reasonably consistent between the standards, so what do the differences in protection mean? It seems the easiest answer is that simply adhering to the NEC and IEC schemes result in reduced safety compared to what is achieved under the ATEX scheme. This is not to say that there is anything stopping customers from requesting compliance with additional standards like EN-1834, the EN-13463 series or ASTM F2876, but there is not a mandate for them to do so and the equipment cost is higher. The higher cost of the additional protective equipment is likely offset by the reduced risk of fire or explosion, since the cost of those rare events is so high.

 

My conclusion from the above discussion is that protection of mechanical components, as described in EN-1834, the EN-13463 series, and ASTM F2876 is reasonable design practice and follows good engineering practices for equipment operating in classified (hazardous) locations. It is not clear to me how the mitigation of electrical ignition sources would offer any significant reduction in the frequency of mishaps if the mechanical systems were not also protected.

 

My questions to you are the following:

 - Have I missed something? Is there a reason why it would be a reasonable design practice to protect against the (potential) electrical ignition sources but not the mechanical ones?

 - When you are purchasing equipment, do you require that the equipment meet additional protection standards not specifically required by law in the regions where you operate? Why or why not?

 - Do your customers ask you to meet additional equipment safety standards?

 

Comments
by Nikolay
on ‎12-17-2016 03:10 AM

 

Hello.

Our company looking for ATEX certified equipment (Air compressors, Generators, Light towers). Equipment to be operated on land.

 

Could you let me know if you able to provide such and if yes I will send more details.

 

Best regards

Nikolay Solovyev

by Nikolay
on ‎12-17-2016 03:12 AM

Hello.

Our company looking for ATEX certified equipment (Air compressors, Generators, Light towers). Equipment to be operated on land.

Could you let me know if you able to provide such and if yes I will send more details.

 

Best regards

Nikolay Solovyev

by Dinesh
on ‎02-26-2017 01:26 PM

Dear Sir,

 

we procured two catapiller gas engine for a project.  one for power generation (indoor) and another for out door application. also we have classified both area as hazarodous area. 

 

 

please confim above statement is ok. also please advise what are measures need to be taken care.

by New member iefox
on ‎02-27-2017 08:40 AM

 

Hello Dinesh,

 

I cannot answer your question from the information provided, but if you are placing equipment in a classified hazardous area then the equipment needs to have appropriate certifications and protection for the area.  If you contact your Cat dealer he may be able to provide more help with your question.

 

Regards,

Isaac

by New member iefox
on ‎02-27-2017 08:43 AM

Hello Nikolay,

 

I would recommend that you contact your local Cat dealer to learn about what equipment may be available for your situation.  If needed, there is a dealer locator tool on Cat.com to help you find an appropriate contact.

 

Regards,

Isaac

 

 

by New member NMboomhand
on ‎08-25-2017 09:38 PM

Your comment was very interesting to read most definately. The most interesting aspect that I am aware of is fuel from foreign sources. Of course this would be a mechanical issue and not electrical, but still something to be considered.

About the Author
  • In 2005, I started my career at Caterpillar as an intern in Kiel, after that I worked as a student and then a temporary employee. I finally became a permanent employee in 2008, working at the Marine World headquarters in Hamburg. Through all these years I was supporting and leading Marketing projects from various areas, including Electronic Sales Tools, Shows, Novelties etc. By May 01, 2011 my job role changed to the current one. In this position I am leading several Electronic Marketing projects such as all Marine and Oil & Gas Social Media activities.
  • I have been in the oil and gas industry for 34 years, primarily in technical sales and support roles for natural gas compression equipment. I have been with Caterpillar for 13 years managing application and service support for Caterpillar’s gas compression product group, managing technical service support for Caterpillar engines in Oil & Gas applications and managing product definition for Caterpillar’s Petroleum marketing unit. I am currently based in the Global Petroleum headquarters in Houston, Texas and am responsible for developing a worldwide Condition Monitoring solution for Caterpillar products used in the Oil & Gas industry. Prior to working with Caterpillar, I was with Halliburton Company’s gas compression rental business unit. There I provided technical support for applications and service in a variety of roles with the last 4 years as Manager of Compression Engineering. I have a degree in Mechanical Engineering from Texas A & M University. I am currently a member of the Gas Machinery Research Council’s (GMRC) Project Supervisory Committee and active in the GMRC’s Gas Machinery Conferences.
  • I began tinkering with engines at age 9 when I built a radio controlled airplane and took the engine apart .  Then at age 12, my dad bought me my first motorcycle, a 1979 Honda XR80.  Several modified motorcycle engines and a few broken bones later my career in developing emissions complaint engines began. Now, I have over 20 years experience addressing CARB and EPA engine emissions and safety regulations in a variety of roles. From gasoline and LPG fueled  LSI engine testing, prototype development, calibration, and field testing to NRTL approvals with Underwriters Laboratory for use in hazardous locations . My career at Caterpillar as Emission Manager  began in December 2011 and I'm enjoying my transition to the industry.
  • I have been working in engineering since 1998, primarily in different aspects of engine design . I joined Caterpillar in 2005 to work on the design of internal engine components. I have been based in Houston and have worked on products specifically for the oil and gas industry since 2008.
  • I began my career at Caterpillar in 2003, developing marketing communications for many different groups including machine, product support and technician recruitment. Since 2008, I have been working as a Marketing Consultant with Global Petroleum to develop effective marketing communications materials and events.
  • As a native of Jakarta, Indonesia, I joined Caterpillar Jakarta District Office as marketing trainee in 1985. A mechanical engineer by education, I spent my early years in Machine, Product Support field assignments before joining the Engine Division as Jakarta District Sales Representative in 1990. In 1995 I relocated to Singapore as Marine Consultant, and later as Sr Sales Representative in Caterpillar Marine Power Systems Division, where I made the breakthrough sales of Cat 3600 propulsion engines to the booming AHT market in Singapore and Malaysian shipyards. In 2005 I moved to the Global Petroleum Asia Pacific as Sales & Marketing Team Leader, and promoted to Sales and Marketing Supervisor position in 2007. In GPAP, I secured several breakthroughs including the first collaborative sales (joint effort with CMPS) of 2x6M25 engines to Keppel Singmarine for Lukoil FSO (2006), and a rigset of 8 x 3616 to Jurong's first Cat-powered Semisubmersible 'West Sirius' (2007). In 2008, I led my India team in securing the largest contract with India's Oil & Natural Gas Corp (ONGC) to repower their fleet of 185 x D399 engines with 3512B ($57M), followed with ONGC Parts and Service Agreements and initiation of India Petroleum Strategy with our India dealers in 2009. In ASEAN I led the breakthrough sales of the C175-16 in the Singapore Jackup rigs market with 19 units booked in 2011 and another 41 to be shipped in 2012 and 2013. Since 2010 I have been working on nurturing Caterpillar network and partnership with other National Oil Companies in Indonesia, Malaysia, Vietnam and Myanmar. I believe that NOC will continue to provide Caterpillar and its dealers good business for prime product and support services in years to come.
  • I started with Caterpillar in 1993 at the Lafayette Large Engine Facility. Currently I am a New Product Defintion Manager for Land Drilling and Land Production Products. I am responsible for managing new product programs for diesel, gas and dual fuel products. I am experienced in Engine development and installation in Generator sets, On-Highway trucks, Motorgraders, Well Service Equipment, Oil and Gas Drilling Equipment.
  • I joined Caterpillar after 4 years in the USArmy Field Artillery. After assignments in fuel system and engine control system design, engine test and development, manufacturing, and gas engine/genset project management, I am presently responsible for large gas compression engine marketing functional requirements and launch of these new products.
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