Section 61.20-17 - Examination intervals(a) A lubricant that demonstrates the corrosion inhibiting properties of oil when tested in accordance with ASTM D665 (incorporated by reference, see § 61.03-1 ) is considered to be equivalent to oil for the purposes of the tailshaft examination interval.(b) Except as provided in paragraphs (c) through (f) of this section, each tailshaft on a vessel must be examined twice within any 5-year period. No more than 3 years may elapse between any 2 tailshaft examinations.(c) Tailshafts on vessels fitted with multiple shafts must be examined once every 5 years.(d) Tailshafts with inaccessible portions fabricated of materials resistant to corrosion by sea water, or fitted with a continuous liner or a sealing gland which prevents sea water from contacting the shaft, must be examined once every 5 years if they are constructed or fitted with a taper, keyway, and propeller designed in accordance with the American Bureau of Shipping standards to reduce stress concentrations or are fitted with a flanged propeller. Accessible portions of tailshafts must be examined visually during each drydock examination.(e) Tailshafts with oil lubricated bearings, including bearings lubricated with a substance considered to be equivalent to oil under the provisions of paragraph (a) of this section need not be drawn for examination-(1) If tailshaft bearing clearance readings are taken whenever the vessel undergoes a drydock examination or underwater survey;(2) If the inboard seal assemblies are examined whenever the vessel undergoes a drydock examination or underwater survey;(3) If an analysis of the tailshaft bearing lubricant is performed semiannually in accordance with the lubrication system manufacturer's recommendations to determine bearing material content or the presence of other contaminants; and(4) If-(i) For tailshafts with a taper, the propeller is removed and the taper and the keyway (if fitted) are nondestructively tested at intervals not to exceed 5 years; or(ii) For tailshafts with a propeller fitted to the shaft by means of a coupling flange, the propeller coupling bolts and flange radius are nondestructively tested whenever they are removed or made accessible in connection with overhaul or repairs.(f) Tailshafts on mobile offshore drilling units are not subject to examination intervals under paragraphs (b) through (d) of this section if they are- (1) Examined during each regularly scheduled drydocking; or(2) Regularly examined in a manner acceptable to the Commandant CG-CVC.CGD 95-027, 61 FR 26001, May 23, 1996, as amended by CGD 96-041, 61 FR 50728, Sept. 27, 1996; 61 FR 52497, Oct. 7, 1996; USCG-1999-5151, 64 FR 67180, Dec. 1, 1999; USCG-2009-0702, 74 FR 49229 , Sept. 25, 2009; USCG-2012-0832, 77 FR 59778 , Oct. 1, 2012