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Regular Contributor

Re: Safety comparison of diesel generator over natural gas generator systems - 2-5MW range

I i live in italy and we have this question all time, and our clients normaly he look a machine and fuel cost for decision, different if wen we the job of generator is CHP  or  net conection i go to gas generators,pollution is not realy the problem we have realy strcly laws, so catalyst and more all time, now for esample in italy the fuel cost is big ivoice, and 60% of decision to go by diesel or natural gas, manutance cost or more is 10% , the more is not considerate becouse all cost more from anywere here, yes the gas engines cost 30% more but for CHP job still are the best, but small sale, stan by diesel only the cip, not loook manufacturing or more, and in italy we have tho most assembly generators company of europe more 40 company, is realy caos and big competition on for our cat dealer to make goot sale,  end of story, my uggestion is to use natural gas maeby more big of diesel but gas engine, we have some istalliation for stanby use without problem, need more investigation and electrical engineering, for realy powerfull needs, sorry for mi english, regards gordini

New member

Re: Safety comparison of diesel generator over natural gas generator systems - 2-5MW range

Hello, I am a university student working on the 'comparison of diesel and natural gas/propane generators' as my final year project. I'm considering such criteria as initial setup costs, annual maintenance and operation costs, pollution (fumes), noise level of operation, safety, and so on. Could you help in the comparison. I'ld also appreciate if you direct me to similar studies that have been done in the past. I live in Nigeria and private power generation is a big deal. thanks.

New member

Re: Safety comparison of diesel generator over natural gas generator systems - 2-5MW range

The gas engine generator is used primarily in distributed generation and connected to the grid for continuous operation.   The diesel engine generator is used primarily in standby systems for limited operation.

 

A diesel engine can take up to 100% load in one step.  A gas engine cannot and may stall if you attempt this.  When connected to the grid, the engine controls ramp up the kW to pre-set level (usually 100% load.)

 

Gas engines in this size range have better fuel economy and lower emissions than a diesel which makes them easier to permit for continuous, full load operation required for distributed generation..

 

Regular Contributor
Employee

Re: Safety comparison of diesel generator over natural gas generator systems - 2-5MW range

Gentlemen,

The only known explosion in a gas Engine is that of the exhaust stack due to the residual gas left due to failure to start attempts. These days Engines have sufficient exhaust purge systems and purge cycles to prevent these explosions from occuring. Larger Engine (>5MW) have exhaust stack explosion relief valves. The most important design is to have the Exhaust piping properly routed so that it does not trap the unburnt gas in the pipe. Lean burn gas Engines have upto 8 - 10% Exhaust Oxygen after combustion so when the temperatures are 400 + C and you have NG trapped it can ignite.

Hope this will be of help..

Cat Dealer
Dealer

Re: Safety comparison of diesel generator over natural gas generator systems - 2-5MW range

Liquid diesel fuel is very hard to ignite. Look on you tube, there is a demo where you can drop a lit match into a cup of diesel, and it will quench. Now if you vaporize the diesel, that is a different story.

 

You will also find that every municipality will require that you store the fuel a certain distance from the building. This will depend upon the fire marshall locally. Most places in IL will require that you put the tank at least 10 feet from a non-fire rated wall. Or you can place it closer if the tank or the wall is fire rated. If you want a fire rated tank look at the UL 2085 rated tanks. These are concrete encased tanks with a ballistic capability.

 

Natural gas needs a certain fuel to air ratio to ignite, and NG is light, so it will rise. If you design your room right, and you even have a leak, you should not have an explosion.

 

So basically both types of engines are safe. Unless there is some crazy catastrophic failure of the controls they will not blow up. More of a slow fizzle.

Tony Yang
Systems Engineer
Patten Power Systems
Contributor
Employee

Re: Safety comparison of diesel generator over natural gas generator systems - 2-5MW range

NJC1979 had some good points to make. 

 

I'd suggest that an engine that operates on diesel fuel is no more or less likely to explode than an engine that operates on natural gas.  I'd suggest that the chance of any engine exploding based on a fuel system failure is remote.  Most industrial grade natural gas engine generators of the ratings you are referring to have safety mechanisms to prevent problems like overspeed or detonation that could be related to fuel system problems.  More of a concern would be the ability to detect or announciate a situation where you have a fuel leak.  There are systems available that can detect and annunciate these conditions for both diesel and gaseous systems.

 

Regarding your comment about 'medium pressure supply', many 500kW - 2MW Cat gas gensets can operate on low pressure gas from 1-5 psi (pounds per square inch) at the engine fuel inlet, which is no more than the gas supply pressure that is supplied to many industrial and commercial buildings by natural gas utilities.

Trusted Contributor

Re: Safety comparison of diesel generator over natural gas generator systems - 2-5MW range

I think either diesel or gas would be fine.  Few things I would consider if this is backup set.

 

1- storage tank location for diesel fuel- spill contamination risk, etc.

2- emissions requirements for gas or diesel set- does it need aftertreatment?

3- access for service needs and installation

4- transient response needs for power acceptance in power outage- diesel will be faster than gas

5- power density will be greater for a diesel set as well- larger footprint needed for gas applications usually

 

As for your safety concerns, you will will most likely have to have a fire marshal or equivalent sign off on the application for permits, etc... 

 

Just my two cents,

 

Nick C.

New member

Safety comparison of diesel generator over natural gas generator systems - 2-5MW range

I would like some opinions and facts on the safety/risk comparisons between a natural gas generator over a diesel generator. I am not talking about the risk of losing a gas supply, but I am looking for very very basic answers to questions like.. 1. Is a gas genny with its medium pressure supply any more likely to explode than a diesel genny and its fuel tank? 2. What broad measures can be taken to mitigate the risks associated with the risks.. Looking at generators in the 500KW-2MW range, to be located in or very near a large office buiding.