We were most distressed to receive today’s message informing us about the broken pump shaft on the Dredge No. KOR 15. Thank you for the photographs and we would appreciate receiving more when available.
 
The Chief Officer’s concerns about experiencing several problems with this particular pump are understood by us and we hope he does not become too discouraged. We have not been made aware of any previous problems with the AMMCO 16x14-40 Dredge Pumps installed in four other of Marine Department’s KOR dredges.
 
In any case, we agree with your decision to have a replacement shaft made in Bangkok in order that the dredge KOR 15 can return to work as soon as possible. As requested, a copy of Dwg. No. ACG-00122, Rev 3 for the pump shaft is attached. This shaft is appropriate for both KOR 15 and KOR 17 dredges. We expect you can have printed there in larger size so that it is more easily read but if you have difficulty printing larger, please advise and we can send large copy via courier.
 
As indicated on the drawing, the recommended material is AISI 4140 alloy steel (or equivalent JIS SCM 440). Although not indicated on drawing, we prefer to use heat-treated and annealed alloy if available for improved machining characteristics. We recommend that the raw material not be larger than about 6.75” (170 mm) diameter so that not too much outer strength is removed by machining. If recommended material is not available, please advise alternatives available there for our consideration. If possible, we would like to receive close-up progressive photographs of the shaft being machined, in particular the radius areas where diameters change and at the threads.
 
From our review of photographs, we expect shaft breakage may be either directly related to breakage of Impeller or related to the replacement Impeller and bronze Impeller Washer not being well seated against the end of the shaft sleeve. 
 
Once the new shaft is made and before it is installed in the pump, it should be checked to confirm the fit of new shaft threads to threads of replacement Impeller and to confirm the Impeller and bronze Impeller Washer will properly seat against the end of shaft sleeve. The shaft should first be screwed into the replacement Impeller as far as possible without either the shaft sleeve or bronze Impeller Washer being in place. The gap distance between back of Impeller and shaft shoulder should be recorded. The shaft sleeve and bronze Impeller Washer should then be installed and the shaft screwed into the Impeller again to confirm the parts are properly seating together. We would appreciate receiving photographs of both these checks of fit if possible.
 
We recommend that a new bronze Impeller Washer be used and it must not be larger than 7” (177.8 mm) outside diameter – same as shaft sleeve. It must also be machined flat with its two sides parallel. The shaft should be screwed into the replacement Impeller until the Impeller, bronze Impeller Washer and shaft sleeve are all well seated together. The assembly should be checked to confirm the Impeller is square with the shaft and to confirm there is no gap at the bronze Impeller Washer, at any point around the outside. “Engineer’s Blue” applied to the bronze Impeller Washer before assembly to aid in determining if the parts are properly seating together with at least 90% contact all around. When proper fitting together of the parts has been confirmed, the shaft can be reinstalled in the dredge pump.
 
Please note that when the dredge pump is reassembled, the bronze Impeller Washer and Impeller must be installed following the procedure outlined in the attached Service Bulletin Form SB-2014-9 and also sent to you July 30, 2015 for distribution to Marine Department.
 
Thank you for your assistance in resolving this problem with the Marine Department. Please keep us advised of the progress of repair.