Dear Editor,
I read with amazement the article in Saturday’s Stabroek News `GPL shuts down Garden of Eden plant over fears of major explosion -outages planned as national grid loses 46.5MW’ which stated inter alia “Fearing a massive explosion after the detection of fuel in the exhaust of a generator, the Guyana Power and Light Inc. (GPL) yesterday shut down its Garden of Eden power plant”.
It is ludicrous that GPL would shut down an entire plant and blackout thousands of customers
because someone detected fuel in the exhaust of a stopped engine operating on Fuel Oil (either
heavy or light)! The engines at the Garden of Eden’s New Power Plant are Wartsila 20V34DF. These engines are designed to operate on dual fuels, either Natural Gas or Fuel oil. Since there is no Natural Gas on shore in Guyana, the engines are being operated on Fuel Oil.
The exhaust manifold of a diesel engine is only connected to the engine via the exhaust ports of the various cylinders. It is obvious therefore that the only way fuel can get into the exhaust manifold is through the cylinders. This would be possible if the injectors are defective and delivering excessive fuel which is not completely burned in the cylinders. The Wartsila 20V34DF engine has a very sophisticated control and monitoring system with includes cylinder temperature measurements. If any of the injectors are delivering excessive fuel and all of it is being burned in the cylinder, the engine would shut down on high cylinder temperature five minutes after giving an alarm. On the other hand, if all of the excessive fuel is not burned in the cylinder, and some of it is carried over into the exhaust manifold, the engine would shut down on low cylinder temperate five minutes after sounding an alarm. Any fuel carried over into the exhaust system would mix with the excess air and immediately detonate since the flash point of Fuel Oil is 65 degrees Celsius and the exhaust temperature is over 700 degrees Celsius. This type of detonation is quite normal in older cars and is called backfire!
If these engines were being operated on Natural Gas, the possibility of gas being carried over into the exhaust system is a major concern because this could result in an explosion.
The system is designed with the necessary safety features to cater for such an event as stated in the Wartsila 34DF Product Guide:
“11.3.1 System design – safety aspects Natural gas may enter the exhaust system if a malfunction occurs during gas operation.
The gas may accumulate in the exhaust piping, and it could be ignited in case a source of ignition (such as a spark) appears in the system.
The external exhaust system must therefore be designed so that the pressure build-up in case of an explosion does not exceed the maximum permissible pressure for any of the components in the system.
The engine can tolerate a pressure of at least 200 kPa. Other components in the system might have a lower maximum pressure limit.
The consequences of a possible gas explosion can be minimized with proper
design of the exhaust system; the engine will not be damaged, and the explosion gases will
be safely directed through predefined routes.”
Editor, it is obvious that the Engineers at Wartsila GOE operations made a major blunder when they detected Fuel Oil in the Exhaust system of the stopped engine. What is disturbing is that the GPL technical staff and Wartsila overseas experts agreed that Fuel Oil in the exhaust of one stopped engine was cause for the entire plant to be shut down. It is embarrassing that the Prime Minister was given bad advice and forced to make a decision to shut down the entire plant due to safety concerns, which did not exist, and thereby denying thousands of GPL customers regular supply of electricity.
Yours truly,
Tara Singh
