476C: EXHAUST TEMPERATURE SPREAD GUIDELINES November 11, 1980 Applicable to: MS3002, 5002, 5001, 6001 and 7001 Machines BACKGROUND/DISCUSSION A statistical analysis of exhaust temperature spread data for units in commercial operations has been made. Based on this data, new guidelines have been established which reflect actual operating experience. The new guidelines are listed below: MODEL SERIES ____________ MS3002 MS5002
GUIDELINES __________ IF THE EXHAUST TEMPERATURE SPREAD EXCEEDS 60F FROM THE HIGH TO LOW READING OR CHANGES 25F FROM THE LAST READING, INITIATE INVESTIGATIVE ACTION.
MS5001 MS6001 MS7001
IF THE EXHAUST TEMPERATURE SPREAD EXCEEDS 80F FROM THE HIGH TO LOW READING OR CHANGES 35F FROM THE LAST READING, INITIATE INVESTIGATIVE ACTION.
The above guidelines reflect operation at base temperature control but can be used for part load operation. Although there is not sufficient part load data to make an accurate assessment, it has been observed that the spreads at part load are 10 to 20F lower than the base load values. These guidelines also reflect operation on both gas and liquid fuels with gas fuels showing higher spreads on the order of 10F. In addition, these guidelines are not meant to supersede turbine protective systems such as the combustion monitor and Integrated Temperature System (ITS). The customer should use the presented guidelines as a reference for setting up his own monitoring program where he can be an active participant in troubleshooting potential problems. An important point regarding the evaluation of exhaust temperature spread data is that THE CHANGE IN SPREAD OVER A PERIOD OF TIME IS PROBABLY A MORE VALUABLE PARAMETER THAN THE OVERALL MAGNITUDE OF THE SPREAD. Combustion problems generally do not occur instantaneously but develop over a period of time depending on the nature of the problem. This deterioration can be picked up through monitoring of the exhaust temperature spread. It is also of value to note how the exhaust temperature spread changes after: COPYRIGHT, GE The information published in this Technical Information Letter is offered to you by GE in consideration of its ongoing sales and service relationship with your organization. However, since the operation of your plant involves many factors not within our knowledge, and since operation of the plant is in your control and ultimate responsibility for its continuing successful operation rests with you, GE specifically disclaims any responsibility for liability based on claims for damage of any type, i.e. direct, consequential or special that may be alleged to have been incurred as result of applying this information regardless of w hether it is claimed that GE is strictly liable, in breach of contract, in breach of warranty, negligent, or is in other respects responsible for any alleged injury or damage sustained by your organization as a result of applying this information.
1. an initial startup 2. a shutdown 3. a maintenance outage The guidelines presented in the above table are felt to be the best estimates for separating satisfactory operation from a potential problem. The user should initiate investigative and/or corrective action as outlined in the Service Manual should the spread exceed the specified limit. A plot of exhaust temperature versus thermocouple location can be an extremely useful tool in trouble shooting hot gas path problems (see attached example ). The plot can also provide an excellent record of data and when used with the guidelines it can help detect an early problem and possibly prevent serious damage. RECOMMENDATIONS The General Electric Company recommends that customers: o adhere to the new guidelines o establish and maintain a data logging system or data plot o insure that the exhaust temperature measurement equipment is in good working order o take corrective action whenever readings exceed limits as set forth in the guidelines The above guideline supercedes those previously published in the Operation and Maintenance section of your turbine Service Manual, TILs 337CR1, 366A, 367A and 430C. Corrective action criteria, however, published in some of the above documents are still valid. Contact your General Electric Company Field Service Representative for any additional information.
COPYRIGHT, GE The information published in this Technical Information Letter is offered to you by GE in consideration of its ongoing sales and service relationship with your organization. However, since the operation of your plant involves many factors not within our knowledge, and since operation of the plant is in your control and ultimate responsibility for its continuing successful operation rests with you, GE specifically disclaims any responsibility for liability based on claims for damage of any type, i.e. direct, consequential or special that may be alleged to have been incurred as result of applying this information regardless of w hether it is claimed that GE is strictly liable, in breach of contract, in breach of warranty, negligent, or is in other respects responsible for any alleged injury or damage sustained by your organization as a result of applying this information.
