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|  MIL-G-24477(SHIPS)
parts per million (ppm) with the degree of accuracy indicated in 4.4.2.3.3.
Iron (Fe).
(a)
(b)
Lead (Pb).
Copper (Cu).
(c)
Chromium (Cr).
(d)
Aluminum (Al).
(e)
Nickel (Ni) .
(f)
Silver (Ag).
(9)
Tin (Sri).
(h)
(i)
Silicon (Si).
Sodium (Na).
(j)
Degree of accuracy.
4.4.2.3.3
The degree of accuracy shall be as follows:
--
Standard reference specimen
Standard deviation
(Range in ppm)
(Maximum in ppm)
3-9
1.5
10-19
2
20-49
3
50-99
5
100-199
8
200-500
15
4.4.2.4 The supplier shall establish maximum limits for exhaust gas temperatures and
blower intake and discharge temperature differential. The engine shall then be operated at
various snorkel loads and rated rpm at various blower intake vacua and exhaust back pressures
in order to determine the engine output limits at which the engine will not exceed exhaust
temperature or blower differential temperature limits as established above.
4.4.2.5 Snorkel operation. The engine shall be operated continuously for 160 hours
rated snorkel load and rpm. The exhaust back pressure at the manifold outlet shall be 6
psi. Intake air pressure shall be 2 inches Hg. vacuum. Fuel" consumption shall be recorded
and submitted to the command or agency concerned.
4.4.2.6 Simulating loss of depth control. The engine shall be operated at the greatest
load which will not exceed temperature limits established in 4.4.2.3. Automatic control of
the blower intake and exhaust valves shall be arranged to gradually decrease the blower
intake pressure from 2 inches of Hg. below atmospheric pressure up to 7 inches of Hg. below
atmospheric pressure, and at the same time increase exhaust hack pressure from 6 psi up to
12 psi. The time required to reach these maximum pressure conditions shall be 3.5 minutes.
The control valves shall then permit the engine to return to snorkel operations (see 4.4.2.4)
in 1 minute. The engine shall operate 5 minutes under snorkel conditions. The entire cycle,
therefore, will require 9.5 minutes. The unit shall operate on this cycle 500 times to de-
monstrate the mechanical reliability of the engine.
4.4.2.7 Simulated wave action. The air inlet pressure shall be constant throughout this
test and shall be 2 inches of Hg. below atmospheric pressure. The exhaust back pressure shall
be regulated for a standard pressure of 6 psi with the damper valve in exhaust line control-
lable to raise the pressure to 8 psi. The cycle of operation shall be for the pressure to
rise to its maximum in a period of 25 seconds, returning to the standard pressure in 5 seconds
and a rest period of 30 seconds or a total cycle time of 60 seconds. This cycle of operation
shall be repeated for a period of 48 hours at rated snorkel load and rpm.
4.4.2.8 Simulated submerged starting test to remove water from the snokel tube. The
engine shall be started with the exhaust line closed until the back pressure reaches a maximum
of 20 psi in approximately 6 seconds. The exhaust line shall then be opened to reduce the
back pressure to the normal pressure of 6 psi. The engine shall then be shut down, and the
test shall be repeated. A total of 250 starts shall be made. One of the starts shall be made
from the cold ambient condition after the engine has been shut down for at least 24 hours.
4.4.3 Test data. Test data shall be submitted on supplier's test forms or on large
sheets with lines folding to 8 by 10-1/2 inches for filing.
4.4.3.1 All temperature and pressure readings necessary for complete evaluation of the
engine performance including ambient room temperature, barometric pressure and relative
humidity, shall be entered on the test sheets. Fuel consumption in pounds per hour shall be
entered for all runs during which engine conditions to become stabilized. All addition of
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