Uss Denver
 Blackmer System One Pump Inspection

Auxiliary Machinery Sea Water Circulating Pump
Inspection and Analysis

Blackmer System One Pump - Model Frame S

Scope
The Auxiliary Machinery Sea Water Cooling Pump was returned to the System One factory after 5 years of operation aboard the USS Denver.

The factory was instructed to do a complete analysis of the pump components in the as received condition to determine the total reliability of the System One pump for shipboard use.

The pump was disassembled while photographs were taken of the components during the various steps. The components were next moved to the QC Dept. where all pertinent dimensions were checked against the drawings and recorded.

Results
The wetted components showed no loss of material due to erosion or corrosion. Data from measurements taken of the components is included and compared to the original drawing tolerances. Note that the backcover width, impeller width and casing suction face dimensions did not change.

The pump casing and backcover were cast from 316 SS and the impeller from CD4MCu.

The fact that the casing and backcover were cast of 316SS and showed no corrosion after five years of operation illustrates the suitability of stainless steel for these applications.

In addition, the casing and backcover were changed to CD4MCu material for all Chesterton Navy applications several years ago. This material further improves the stainless steel capability in seawater in addition to significantly improving the strength and hardness. The improved strength should be beneficial to the Navy for operation under high stress conditions.

The CD4MCu is superior because it is a duplex stainless steel (duplex phase microstructure). Materials with this microstructure offer the best properties of both phases: the austenite improves toughness and localized corrosion resistance while the ferrite phase provides strength and resistance to chloride stress corrosion cracking, pitting and crevice corrosion.

The higher chrome content plus the molybdenum combination achieves the good chloride pitting and crevice corrosion resistance. A chart of the chemical composition and strength comparisons between the 316SS and the CD4 is included.

To further demonstrate the capability of the CD4MCu material, the impeller still had machining lines from the original machining process on the O.D. These lines represent a 125 RMS finish which is equivalent to a maximum groove depth of .00025 ". Thus, the impeller had less than ¼ of a thousandth of an inch wear or corrosion on the diameter.

Conclusion
The above analysis demonstrates the suitability of the CD4MCu material for Naval sea water applications. The thorough inspection of the components from the USS Denver after five years of continuous operation revealed no wear or corrosion problems. Due to the superior strength of the CD4MCu material and its ability to withstand chloride stress corrosion, System One feels that this is the best and most cost effective material for the US Navy to use for shipboard pumps.

Overall, this pump required no maintenance during its span of operation and the superb condition of the components exemplify the reliability of the System One pump for Naval services. The pump was operating successfully when it was removed and was sent back to the factory for the sole purpose of inspection and analysis.

In addition, a memorandum written by Steve Lee, CNSP Port Engineer, clearly substantiates the durability and reliability of the System One pump. This pump onboard the Denver was subjected to two instances of extreme duress which could have resulted in catastrophic failure:

• The pump had been started and operated for a period of time with the suction valve closed. This was noticed when the pump became exceptionally hot.
• The discharge strainer plug was misaligned, resulting in no flow through the strainer. In other words, the pump was deadheaded which again resulted in high temperature buildup in the pump and suction piping.

The pump operated successfully after both of these incidents which proved that Blackmer System One pumps were a viable product for the Naval fleet.