Resistive Load Banks Power Generation Testing Load Banks Industry trade organizations and manufacturers both agree that a well planned preventive maintenance program is vital to the reliable operating of a standby generator. Load Banks are a essential part of such a program. Load Banks provide a practical means to test the system without interruption to the critical loads. The primary cause of diesel engine failure is “wet stacking” (”wet” unburned fuel accumulating in the engine “stack”). It is caused by under-loading of the generator. Diesel engines that are lightly loaded, or allowed to idle for long periods, never reach their recommended operating temperature. Over time, unburned fuel coats the combustion chamber, reducing engine rating, efficiency, and life span. A preventive maintenance plan that includes load testing of a diesel generator set, will reduce the harmful effects of “wet-stacking” and increase engine life. BOBWHITE Load Banks are devices designed to provide electrical loads for testing power sources such as generators. Load banks are also used to reduce “wet stacking” problems in diesel engines of backup generating systems. The load bank should be used in conjunction with a good preventive maintenance schedule. A resistive load bank is equipped with elements that “heat”, which provide a large amount of resistance to the flow of electrons. The Effects of West-Stacking on a Diesel Engine RENTALS PO Box 2472 | Victoria, TX 77902 P: 361.570.5000 | F: 361.578.4456 bobwhiterentals.com Load Banks For Prevention Of Wet-Stacking in Diesel Generator Sets This information is general in nature and intended to give the reader a overview of the issues involved. Specific recommendations can only be made after a review of the equipment involved, installation parameters, applicable codes and national standards by competent personnel. Please consult Avtron Manufacturing, Inc. with comments or questions about the information contained herein. Wet-Stacking “Wet-Stacking” - The buildup of unburned diesel fuel and carbon residues in the engine and exhaust system causing 65% of maintenance problems in generator sets! PRINCIPLE CAUSE The UNDERLOADING of the generator. Operating at less than 50% of rated load. Reduce the problem by increasing power consumption above 70% of the rated load. Periodic maintenance should include load banking. Not only does wet stacking damage the engine but to much carbon buildup in the exhaust can cause flameout (Flame shooting out the top of the exhaust). Wet-Stacking is a common problem with diesel engines which are operated for extended periods with light or no loads applied. When a diesel engine operates without sufficient load it will not operate at its optimum temperature. This will allow unburned fuel to accumulate in the exhaust system, which can foul the fuel injectors, engine valves and exhaust system, including turbochargers, and reduce the operating performance. Our Preventive Maintenance Program can save thousands of dollars in costly repairs. Providing additional load from the building load may not be practical with critical computer, life safety or communication equipment. Any interruption of power to these loads may cause a loss of data, operations or jeopardize personal safety. In order for a diesel engine to operate at peak efficiency it must be able to provide fuel and air in the proper ratio and at a high enough engine temperature for the engine to completely burn all of the fuel. The proper load can be achieved by adding additional building load or by providing supplemental load through the use of a resistive load bank. These can be small portable load banks designed to be rolled up to the generator under test or they may be larger trailer mounted load banks for generator sets in the 1-3 MW range. Wet-Stacking does not usually cause any permanent damage and can be alleviated if additional load is applied to relieve the condition. In extreme cases it can cause the engine to run backwards at shut down due to excess fuel buildup in the exhaust system causing costly damage. It can reduce the system performance and increase maintenance. Applying an increasing load over a period of time until the excess fuel is burned off and the system capacity is reached usually can repair the condition. This can take several hours to burn off the accumulated unburned fuel. BOBWHITE RENTALS Load Banks Use: Diesel engine “Wet Stack” Prevention Applies full KW load to engine Bring to full load temp to burn out carbon/fuel build up 35 Minutes 1 Hour 3 Hours Operating diesel engines at low load will cause increased lubricating oil consumption and oil/fuel leaking from the exhaust. Engine internal parts are designed to run under fully loaded conditions. When an engine is run on low to light load the proper engine temperature is never reached. The tolerances of internal part are bigger because the engine is not at full temperature. This leads to lubricating oil passing thru the tolerances in valves guides, stems, pistons and liners. Heavy carbon buildup on pistons, in piston ring grooves, valves and turbocharger 1. Heavy carbon buildup on pistons and in ring grooves can cause piston seizure when operating later at full load. 2. Low combustion temp will result in insufficient burnt fuel, which will cause diluting of the lubricating oil. 3. Bore polishing 4. Due to the low combustion temp, unburnt fuel and lubricating oil will enter the exhaust manifold and eventually leak out through the joint in the exhaust manifold.