2-1-103

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2021

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Mechanical Engineering

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Nov 24, 2024

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SERVICE BULLETIN NOTICE: The Type of Change and Recommended Compliance specified reflects Solar’s best judgment regarding the Service Bulletin. All questions should be directed to your Solar Field Service Representative. Solar, Saturn, Centaur, Taurus, Mercury, Mars, Titan, SoLoNOx, and Turbotronic are trademarks of Solar Turbines Incorporated. Cat and Caterpillar are trademarks of Caterpillar Inc. Specifications subject to change without notice. NUMBER: 2.1/103 ISSUED: May 1987 REVISED: PRODUCT: Mars MODEL(S): All Specifics: Units with Pneumatic Starter Assembly, P/N 124990 through -200 SUBJECT: PNEUMATIC STARTER/CLUTCH ASSEMBLY FIELD MODIFICATION KIT Type of Change: Product Improvement Recommended Compliance: Information Purpose: To announce the availability of a Mars pneumatic starter field modification kit and describe the nature of the improved design. GENERAL INFORMATION: Some early model pneumatic start system failures occurred due to starter clutch shaft misalignment and/or clutch bearing failure due to a marginal lubrication. The start system has been redesigned and incorporated in new engine products since 1985. The design improvements are available in a field modification kit for earlier units. The installation of this kit will require some changes to the package and will generate some displaced parts. Original Design – See Figure 1 1. Starter/clutch shaft misalignment The initial arrangement of the starter/clutch is shown in Figure 1. Spline clearance and the short distance between the splines, together with high spline eccentricities could cause the splines to bind. This with high spline eccentricities could cause the splines to SERVICE BULLETIN Page 1 of 5 NUMBER: 2.1/103

bind. This would result in high loads on the small bearing and cause the bearing to heat up, loosen on the shaft, spin and create more heat until failure. Binding of the splines could also misalign the clutch shaft and housing, which would cause end loading and wear on the clutch sprags, and possible assembly lockup. 2. Lubrication The lubrication of the clutch components is accomplished through a jet as shown in Figure 1. The oil is caught in the annulus, flows through axial holes to the small bearing area, through a around the bearing and into the clutch space. Here, the oil is trapped by an oil dam. Some of this oil is centrifuged out through holes in the clutch housing and the remainder flows through the large bearing. The original design did not provide sufficient oil distribution at the small bearing sliding surfaces (cage/inner race). This could create high friction between the sliding surfaces and cause heat to warm up the bearing inner race again, contributing to relation of fit and spin on the shaft, thus creating more heat until failure. Figure 1 Mars Starter/Clutch Original Design Page 2 of 5 SERVICE BULLETIN NUMBER: 2.1/103

Redesign – See Figure 2 To minimize the loads on the small bearing, the starter/clutch splines distance and tooth clearances were increased. Spline teeth were also crowned. The increased distance and clearances prevent splines from binding, thus eliminating the load on the small bearing and misaligning the clutch. Crowning of the spline teeth also minimized thrust loads on the bearing. To ensure lubrication to the clutch assembly components, the following changes were made: • To distribute the oil more efficiently, the single jet was replaced by three, equally spaced. • Two oil annuli are now provided. One is for cooling the bearing inner race, the other for bearing and clutch lubrication. One other jet was added to the large bearing, on the outside surface for lube and cooling. • To ensure oil on the bearing sliding surfaces and clutch shaft surfaces, the oil dam inside diameter was reduced. This trapped more oil. • The small bearing cage was changed from an inner race riding to an outer race riding. This ensures the sliding surfaces will be lubricated. Internal clearances also were increased to tolerate a greater differential temperature between the races. • To ensure the balls ride in the proper position in the bearing races, shimming of the clutch assembly is made. This positions the balls and end play is minimized. • Air-oil mist cooling holes were added. Holes on the rotating housing pump the air-oil mist out, and holes on the clutch shaft let the air-oil mist in. SERVICE BULLETIN Page 3 of 5 NUMBER: 2.1/103

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Figure 2 Mars Starter/Clutch New Design ACTION REQUIRED: 1. Customer determines if turbine package is equipped with pneumatic starter assembly P/N 124990-100 thru -200. If the package is not equipped with one of these pneumatic start systems, no action is required. If the package has one of the above assemblies, review maintenance records to determine if the field modification kit has been installed. If so, no further action is required. 2. If the package has an unmodified pneumatic starter assembly P/N 124990 -100 thru -200, it should be determined if the starter is functioning correctly. This can be done without any special tools or equipment. 3. Refer to the Operation & Maintenance Instructions manual to review operating parameters and sequence of operation associated with pneumatic starter. During the next scheduled maintenance or other convenient shutdown period, examine the air/gas inlet strainer (FS 921) and pilot valve inlet filter (FS 922) for condition and cleanliness. Install 0-200 PSI gage on pressure sensing line on starter housing, Figure 3. Check starter oil reservoir for correct level. Page 4 of 5 SERVICE BULLETIN NUMBER: 2.1/103

4. Observe starter during next start cycle and rundown; observe installed gage to see if adequate start pneumatic pressure is achieved; listen for timely starter clutch drop-out during run-up and for any abnormal sounds or vibration that may indicate starter shaft binding. NOTE Ear protection may be required if package is in confined area. 5. Contact the Solar Regional Service Office in your area for further recommended action if any operating abnormalities are found or suspected. Solar Regional Service assistance is available for the above recommended maintenance inspection. Figure 3 Typical Turbine Pneumatic Starter Installation SERVICE BULLETIN Page 5 of 5 NUMBER: 2.1/103