TM  55-2840-241-23 7-18.   Compressor Discharge Air Tubes Inspection. Visually inspect for cracks or dents in the sheet metal surfaces and wear in the seal ring grooves. If a crack the air tube if repairable limits are exceeded. a. Check for cracks in the sheet metal surface, Weld repair cracks which are three inches or less in length and do not extend into the brazed joints at the end flanges. (Refer to paragraph 7-31.) Replace the air tube if cracks are longer than three inches or extend into the brazed joint. c. Tubes with dents within allowable limits will be allowed  to  continue  to  operate  without  straightening  or reforming. NOTE Dents should be round with no evidence of a sharp bottom. As a rule of thumb, a dent 1/8 in. deep should be a minimum of 1/2 in. in diameter. 7-19.   Compressor   Discharge   Air   Tube   Seal Ring  Inspection. b.  Check   for   dents   in   the   sheet   metal   surfaces. Replace  compressor  discharge  air  tube  seal  rings which  exhibit  fretting,  excessive  wear,  or  distortion. Replace two-piece seals when the spherical radius on the (1) Any dent is greater than 1/8 in. deep. OD is worn flat all the way across. (2) There are more than three dents  up  to 1/8 in. 7-20.  Combustion  Liner  Inspection. deep m areas not affected by weld joints. Inspect the combustion liner as outlined in table 7-1. Table  7-1.  Combustion  Liner  Inspection Item Inspection  and  method Serviceable limits Repairable limits Corrective action 1 Pulled  or  broken  spot- Not more than three Not more than four Weld  repair.  (Refer  to welds at liner step adjacent welds, or adjacent spotwelds or 40 paragraph  7-32a.) (See  fig.  7-8.)  (Visual) total of six. percent of total per step. 2 Handling  damage. (See  fig.  7-8.) a.   Mashed-out-of- None  permitted. Able to straighten to Straighten  and  re-form. round.  (Visual) concentricity limits. b.  Dented.  (Visual) None  permitted. Any dent that remains Straighten  and  re-form. within the  area  shown  on figure  7-8  and  does  not cause thin-out of metal. Straightened dents must meet concentricity limits. 3 Localized high temp- Warpage  less  than perature distortion 3/16 in. deep over an indicated  by  warping area 1 in. in diameter or rippling of the liner and remaining within surface and is normally the area shown on accompanied by discol- figure  7-8. oring  (burning)  of  the area.  (Visual) Not  repairable. Replace  liner. 7-10 Change  23 diameter. (3)   Any   dent   is   greater   than   1-1/2   in.   in in the sheet metal surface is suspected, refer to TM 1-1520-254-23, Technical Manual Aviation Unit Maintenance   (AVUM)   and   Aviation   Intermediate Maintenance (AVIM) Manual Nondestructive Inspect- ion Procedure for OH-58 Helicopter Series. Replace