What To Look For When Buying Diesel Generators?

In industrial facilities, diesel generators provide supplemental or emergency power to pumps, blowers, elevators and other equipment throughout the facility in the event of an unexpected power outage. As a result, the temperature in the diesel generator exhaust rises rapidly from ambient to 700°F or higher - some manufacturers even report that the temperature in the exhaust can approach 1,000°F.

However, these temperatures are not consistent. Because diesel generators are used as a temporary solution to power loss, they undergo many heating and cooling cycles throughout the life of the unit as the generator is started up, shut down and restarted.

Diesel generator exhaust ducts combine these temperature extremes with a high-vibration environment that tends to damage less robust insulation materials. For example, at such high temperatures, mineral wool will burn off the adhesive and silica aerogel will thermally displace, compromising the thermal properties of both insulating materials. 

Similarly, the harsh and demanding physical conditions of a diesel generator exhaust duct can physically damage expanded perlite. Depending on the location of the generator exhaust duct (indoor or outdoor), the system designer may also need to consider whether corrosion under insulation (CUI) is a variable to be considered.

Given these extreme conditions, selecting an insulation material that has the performance criteria needed to withstand the rigors of a diesel generator exhaust can help optimize system performance and life-cycle costs.

Configuration of Diesel generators

When selecting a diesel generator, the first question is what is the size of the load it will provide and what is the amount of running load (KW) and starting load (KVAr). What type of load will be supplied? Is there, for example, a UPS load or a heavy motor load? Is the load a steady load or an intermittent switching load? This is known as diesel generator sizing for site loads. The second question is whether the generator will operate as a backup power source or whether it will operate as the primary power source. The third question is how long will this investment last?

 In other words, are we going to choose a heavy duty generator set that will last more than 5 years or will it last a few years. The location of the generator set and the environmental conditions. Are there noise restrictions? Are there space limitations? What voltage and frequency will this generator produce? 

All these considerations will influence the final decision on which diesel engine will start, which alternator will be driven, what is the KW rating of this generator set, how it will be installed, what control system will be installed, protection level, cooling system, acoustics... etc. This is referred to as the diesel generator configuration for the site load. Acoustics... etc. This is known as the diesel generator configuration for the field load. Acoustic... etc. This is known as the diesel generator configuration for field loads.

Installation Recommendations

Best practice recommendations for diesel generator exhaust piping suggest using two layers of insulation 1. This allows for the exhaust piping to expand and contract during heat up and cool down without exposing the pipe directly to the surface through gaps in the insulation. In order to apply the layers appropriately, they should be offset from each other both circumferentially and longitudinally such that the outer layer covers the joints of the inner layer.  

When installing insulation on long, vertical runs, use insulation support rings to support the weight of the insulation as well as expansion joints. As with all insulations, the system should be covered with a metal jacketing to protect the insulation and add an additional layer of defense against CUI.