Section 64.9 - Maintenance, repair, and alteration of MPTs(a) Each MPT must be maintained in accordance with the approved plans, this part, and subpart 98.30 of this chapter.(b) Repair of an MPT is authorized, provided that each repair is in accordance with the approved plans.(c) No MPT may be altered, except with the written approval of the Commanding Officer, U.S. Coast Guard Marine Safety Center.(d) After each welded repair or alteration, an MPT must be hydrostatically pressure-tested in accordance with § 64.83(a) .CGD 84-043, 55 FR 37409, Sept. 11, 1990