ENGINEERING MAINTENANCE BRANCH
BULLETIN


Issue # 014

T
HIS
I
SSUE CONTAINS
:

Picture of the Month

SAMM/Maintenance Tips

Electric Motor Maintenance Program
Review

Question of the Month Man-hour
Estimates in SAMM

CMEO Training What Are You Waiting
For?

Feedback Its A Bright Idea

Vibration: How Bad & How Soon???
This is the engineering maintenance management
bulletin to MSC ships and shoreside personnel.
The purpose of the bulletin is to inform all
concerned of current COMSC Preventive
Maintenance management practices associated
with any new or revised policy and procedures,
along with helpful tips & tricks for improved
maintenance. The bulletin will also discuss and
present any upcoming initiatives in the various
programs.
We continue our efforts to bring you useful
information with the page dedicated to the
Vibration Monitoring System (VMS). This will
have useful tips as well as past case histories.

PICTURE OF THE MONTH REQUEST -
WE NEED YOUR PICTURES!!
It is said, A pictures worth a thousand words! If you
have pictures of Shipboard Maintenance (Vibration
Monitoring, Oil Sampling, machinery upkeep, etc.) being
performed, or a visit from a SAMM or VMS Tech Rep,
please send them (along with a brief narrative as to what the
picture is about) to Norman Wolf (e-mail:
norman.wolf@navy.mil
).

Aboard the USNS LEWIS & CLARK (T-AKE 1), DLI
Engineerings Mike Johnson takes initial vibration data
(using a DCA-31 data collector) on one of the Main
Machinery Room exhaust fans during the Machinery
Vibration Baseline Survey performed underway. First-
of-the-Class surveys provide a wealth of knowledge for
enhancing the performance monitoring of this and
follow-on vessels machinery.
SAMM/Maintenance Tips
Extend the life of your LogBook PDA battery: For units with conventional disposable batteries, leave unit
out of the cradle. This will prolong the life of the batteries in the unit.
-
Reader
Tips provided by Seaworthy Systems Incorporated (SSI)
Human Error Tip. To minimize human error, the culture should:
a.

Allow the boss to hear bad news.
b.

Identify and address potential failures proactively before they materialize.
c.

Realize that punishing people does not necessarily eliminate the risk of recurrence of the same failure
somewhere else.
d.

Not blame the regulator for failing to monitor closely enough.
e.

Make the concept of Root Cause Analysis an integral part of the organizational culture.
-Tip provided by Reliability Center Inc.,
http://www.reliability.com
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ENGINEERING MAINTENANCE BRANCH
BULLETIN



Electric Motor Maintenance Program
Review
(By David M. Greer, Elec. Engineer, N711)
According to two separate studies performed in the
past three years, electrical maintenance on the T-
AOE-6 and T-AKR-300 class vessels accounts for
one-third of all shipboard maintenance. Motor
maintenance alone accounts for 1/3 to 1/2 of an
electricians work time on T-AOE-6 and T-AKR-300
class vessels. These numbers can be expected to be
similar for other MSC vessels. The electrical portion
of shipboard maintenance, specifically electric motor
maintenance, is critical and deserves a significant
amount of attention.
Our objective is to provide tools which will establish
an effective motor maintenance program to prevent
unexpected failures through planned motor
maintenance efforts. Recent research performed on
electrical technologies currently on the market has
revealed an array of motor diagnostic tools. Only a
few of these technologies are currently being
employed by MSC as a part of our electrical
Condition-Based Maintenance (CBM) program.
These are infrared thermographic inspection and
insulation resistance testing by means of megger
devices, and/or insulation resistance constant
monitoring devices (e.g. MSEs FailSafe Insulation
monitors used on several MSC vessels).
Infrared thermographic inspection, an online (i.e.
system needs to be energized while testing)
preventative maintenance technique using an infrared
camera, is useful in detecting loose connections,
overloaded circuits, and poorly maintained electrical
equipment due to abnormal increases in heat. The
faults that are detected are trended based upon degree
of fault.
Insulation resistance testing, an offline (i.e. system is
de-energized) preventative maintenance technique,
places a DC voltage between the motor windings and
ground. The megger device and insulation resistance
monitor device detect current leakage and then
convert to meg-, gig-, or tera-Ohms. Thus, this form
of testing provides early warning of insulation
degradation and breakdown helping to reduce motor
start-up failures.
In addition to Thermography and insulation
resistance testing, there are plenty of other motor
diagnostic techniques. In Dr. Howard Penroses
article, Multi-Technology Approach To Motor
Diagnostics (see
http://www.iemd.org/toc.htm
), he
describes methods such as high potential (HiPot)
testing, surge testing, polarization index (PI) testing,
ohm meter testing, vibration analysis, ultrasonic
testing, voltage/current testing, Motor Circuit
Analysis (MCA) testing, and electrical signature
analysis (ESA) also known as Motor Circuit
Signature Analysis (MCSA). Here is a brief
description of each:


High potential testing evaluates the insulation
between the motor windings and ground by
applying a voltage twice the value of the motor
rated voltage plus 1,000V for AC and an
additional 1.7 times that value for DC high
potential. This test is considered potentially
destructive as opposed to insulation resistance
testing.
Surge comparison testing is a go/no-go test that
compares the impedance of each motor phase
graphically by using pulses of voltage at values
calculated the same as high potential testing. This
test detects shorted turns within the first few
turns of each phase and is considered potentially
destructive.
Polarization Index testing is used to detect severe
winding contamination or overheated insulation
systems. An insulation tester is used and the 10
minute to 1 minute values are viewed and a ratio
is produced.
Ohmmeter testing detects loose connections,
broken connections, and very late stage winding
faults by measuring and comparing ohmmeter
values between windings of an electric motor.
Vibration analysis measures mechanical
vibration using a transducer, which provides tri-
axial vibration values and performs Fast Fourier
Transform (FFT) analysis. These values are
indicators as to the condition of numerous
mechanical components, such as bearings and
alignment. Rotor faults can be detected as long

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Issue # 014 ENGINEERING MAINTENANCE BRANCH
BULLETIN


as the electric motor meets the minimum load
requirement.
Ultrasonic testing measures low and high
frequency noise to detect variety of electrical and
mechanical faults towards the late stages of their
development.
Electrical Signature Analysis (ESA) testing is an
online technique, which uses the electric motor as
a transducer to detect electrical and mechanical
faults. ESA detects early rotor faults, late-stage
stator faults and mechanical problems in their
later stages. ESA is usually used as a go/no go
test but it does have trending capabilities.
Motor Circuit Analysis (MCA) testing is a non-
destructive offline technique, which uses a low
voltage output while taking and evaluating
trendable readings through a series of bridges.
MCA devices use a combination of values for
resistance, impedance, inductance, capacitance,
phase angle, current frequency response and
insulation testing to troubleshoot and evaluate
control, connection, cable, stator, rotor, air gap
and insulation to ground health.
Several common approaches to the incorporation of
multiple technologies already exist in the electrical
maintenance industry. In general, a combination of
offline and online testing to join both electrical and
mechanical disciplines is recommended since both
types of tests identify faults that the other type
cannot. For example, insulation problems can only
be detected by using an offline/de-energized test,
whereas online testing is necessary to detect issues
with vibration, alignment, load, bearings, and power
quality.
Dr. Penrose further points out in his article that in a
2003 Motor Diagnostic and Motor Health Study,
38% of motor system testing involving only
vibration and/or infrared saw a significant return on
investment. This number jumped to 100% in systems
that used a combination of MCA/ESA along with
vibration and/or infrared. Vibration and Infrared
Thermography, our current technologies, are capable
of early detection of faults with cables, stators, rotors,
or air gaps. Combining MCA testing with MSCs
vibration analysis and infrared thermography
programs would provide the early detection of faults
from power quality, controls, connections, bearings,
insulation, vibration, alignment, and load. Thus,
MSCs fleet (in particular, vessels driven by
electrical propulsion) would notice a significant
increase in early warning detection of potential motor
faults, which can facilitate advance planning prior to
the need for a repair.
It should be noted that although MCA
ins