Data discrepancy
A significant inconsistency appears in your recent article by Steve Shu, Francis Christiano, and Malcolm Harrison, "Analysis points to electric-motor drivers for Angola LNG" (OGJ, Oct. 7, 2002, p. 60). In part, Table 3 in this article shows the following:
The figure 270 hr/year for gas turbines plays a large role in determining the conclusions contained in the article: Motors are favorable over gas turbines for the Angola LNG plant.
The article cites "Use Equipment Failure Statistics Properly" by Heinz Bloch and Fred Geitner (Hydrocarbon Processing, January 1999). In part, that article shows the following data:
I suspect the 270 hr referenced in the OGJ article to be in error, and it adversely affects the comparison between gas turbines and motors.
Bud Thompson
Facilities engineer with major integrated US oil company
Author replies
Mr. Thompson is correct in his interpretation of the reliability-maintenance data from the 1999 article by Heinz Bloch.
The data provided by Foster Wheeler in Table 3 of our OGJ article were provided as "typical component availabilities," using the referenced article as the major source of data. The data quoted for the gas turbines in Table 3 and used in the Angola LNG study were based on information supplied by General Electric, specific to the machines usually used on LNG projects and so more accurate for the LNG industry.
In the article, we did not provide a reference to the Angola LNG study because it is not in the public domain.
Malcolm Harrison
Foster Wheeler Energy Ltd.
Reading, UK
