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Magazine Temperatures

The main purpose of a daily magazine inspection is to check and record space temperatures. If you recall, temperature is the single most important factor that affects powder and propellant stability.

Temperature readings normally are taken once a day. The exact time may vary, but most ships take the readings in the morning (around 0800, for example). A special maximum and minimum thermometer is used. (Sometimes it's called a high-low thermometer.) Figure 2-12 illustrates a typical maximum and minimum thermometer.

Every magazine or locker will have at least one such direct-reading thermometer. It will be located where maximum space temperature variations will normally occur. It must be installed so it is readily accessible for taking readings and resetting the index pointers. Special brackets are available to mount the thermometer where accidental damage can be prevented.

View A of figure 2-12 shows the internal components of the device. The temperature-sensitive element is a single-helix low-mass coil. The coil fits closely inside the thermometer stem. The bimetal element is carefully sized and aged for lifetime stability. The element is covered with a fluid to assure good heat transfer. The fluid also permits maximum speed of response and reduces pointer oscillations caused by

Figure 2-12 . -Bimetallic maximum and minimum thermometer: A. Internal components; B. Dial fats and pointers.

outside vibrations. The case and stem are made of stainless steel for strength and anticorrosion purposes.

View B of figure 2-12 illustrates the dial face of the thermometer. It is 3 inches in diameter. A plastic window protects the index pointers. The index reset arm is on the outside of the window and is used to reset the high-low pointers. Temperature graduations on our example are marked off in 20-degree increments. The approximate readings on this thermometer are 100F, high; 78F, present; and 55F, low. After you record these temperatures, reset the high and low pointers in line with the present pointer. As temperature rises during the day, the present pointer pushes the high pointer up the scale. As temperature falls during the night, the present pointer reverses direction. It now pushes the low pointer down the scale. As the sun comes up, the present pointer moves up the scale. Thus we see three different temperature readings reflecting the temperature variations throughout a 24-hour period.

The 45-degree spread between the high and low pointers in our example is a bit large, but illustrated for clarity in our explanation. However, it could happen. The reading you must be cautious about is the 100F high. The magazine air-conditioning (A/C) or ventilating system should be turned on in this instance.

The optimum temperature should be around 70F. If the A/C system is not working, artificial cooling (fans, blowers) might have to be used.

The bimetallic maximum and minimum thermometer described is becoming the standard thermometer in shipboard magazines. You may come across a different model. It only has a maximum (high) index pointer and a reset knob. This type of thermometer is acceptable. The older liquid-in-glass (tube) mercury high-low thermometer is no longer authorized for shipboard use. These mercury units should be replaced with the bimetallic-type thermometer.

Records of Magazine Inspections

Like other maintenance procedures, magazine inspections and ammunition surveillance operations are performed periodically according to a prescribed 3-M schedule. The magazine inspections and surveillance operations presently prescribed for all United States naval vessels are listed in OP 4 and on applicable MRCs.

Written records must be kept of all maintenance operations, whether they are routine or not. As far as magazine inspections and ammunition surveillance are concerned, the most common written record is the daily magazine temperature report form (fig. 2-13) and

Figure 2-13.-A. The magazine temperature record; B. Daily magazine temperature report.

magazine temperature record. 3-M Systems records may also be considered as records of magazine inspection.

The magazine temperature record is a card posted in each magazine. Every day you enter the maximum and minimum temperatures recorded for the previous 24 hours in that magazine. The card is replaced every month, and the old one is turned over to the weapons officer.

The daily magazine temperature report summarizes the results of magazine inspections for the whole ship. This form includes not only spaces for entering the highest and lowest magazine temperatures but also for reporting the condition of the magazines and their ventilating devices, and (under Remarks) for miscellaneous nondaily routine work.

The daily magazine temperatures are transferred from the record cards to a magazine log that is a permanent record of all magazine temperatures. A separate section of the magazine log should be set aside to record the results of the monthly sprinkler system tests.

Magazines are considered to be in satisfactory condition if inspection shows the space meets the requirements listed on applicable MRCs. Daily inspection requirements usually include checking the general condition and cleanliness of the space. Less frequent inspections (monthly, quarterly, and so on) normally direct a more detailed check of specific magazine conditions and equipment. Each 3-M inspection requirement should be completely understood and followed to the letter. Doing so not only ensures a safe ammunition storage area but also fulfills the requirements of periodic inspections, such as the explosive safety inspection (ESI). ESI inspectors use the same inspection criteria as are found on your MRCs.


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