By Gregg Schneider, Vice President, Gateway Products Group, Inc. —
Much has been written about automotive spark plugs and how to select the best one. Some blogs focus on extending plug life, others on improving performance, and still others on providing answers to the top questions on the minds of many spark plug buyers: What metallurgy makeup is best? What about the design? Should I use multi-ground, J-gap, angular gap, or pre-chamber?
If you find yourself in the industrial sector, you might also be asking if the same information is applicable to industrial applications, and what else should you consider when selecting industrial spark plugs?
Gas quality and performance
In general, precious metal plugs will provide longer life than J-gap or nickel multi-ground designs, (I plan to cover the advantages of materials in future posts), but when selecting industrial spark plugs, there are other factors to consider. We have all heard stories of spark plug life reaching up to 8,000+ hours. This is achievable in some applications, but maybe not yours. Why? It might be your gas.
Stationary natural gas engines differ from automotive engines, and even mobile CNG engines, in one key area, Gas Quality! When you go to fill up your car you know the octane and can be assured of the quality from the pump. However, wellhead gas, transmission, landfill gas, and digester gas all have different methane contents and BTU numbers, as well as different levels of contaminants. Wellhead can have High H2S and landfill Siloxane, and all untreated systems can have high moisture content in the gas. All these factors can impact spark plug performance. So which plug is correct for your application? In short, it depends on the conditions at your site and how the engine is operated.
Better life vs better value
Let’s think this through further. If you have an application with High Siloxane or High H2S, and you are experiencing short spark plug life, is it reasonable to believe more precious metal, at a higher cost, will yield better results? In many cases the answer is no.
Most manufacturers, including Denso, Champion, Bosch and GPG, offer multiple designs for the same engine! You’ll find more than three designs for Caterpillar 3500 series and Waukesha engines alone! Why would they do that? The simple answer is that all manufactures, GPG included, want to provide a product offering that fits your operational needs at the best possible cost. Just because a product is potentially long life, does not mean it provides the best value!
High Precious Metal Plug vs Alternate
To illustrate, let’s take a look at a hypothetical example of a location with High Siloxane.
High Precious Metal Plug
- Maintenance interval: 500-700 hours
- Spark plug life: 1400 hours
- Cost per plug: $100 each (price used for easy math)
- Runtime cost per hour: $100/1400 or .0714 per operating hour.
Alternate Low Precious Metal Plug
- Maintenance interval: 500-700 hours
- Spark plug life: Single use of 700 hours
- Cost per plug: $45
- Runtime cost per hour: $45/700 or .064
- Operating hour savings: .007
- 8,000 hour service interval savings: $56 per cylinder (.007 x 8000)
That’s a savings of $56 per cylinder—without changing any operational planned shutdowns or maintenance!
So which spark plugs are better?
This is not to say higher cost premium plugs or lower cost standard plugs are better, but if you have short life on plugs, you may have opportunities to reduce overall cost, with no impact to PM scheduling, by using lower cost products. The same is true if you are running high quality methane. New designs are entering the market that provide longer life and better engine stability at a lower runtime per hour cost.
If you would like to find out if an alternate plug might be right, GPG is here to help.