Downloaded from https://www.everyspec.com The climatic values included in the design types represent the extreme conditions materiel is likely to encounter in the field, with allowance for some risk (see 1-5b and app A). b. Daily weather cycles. Each of the climatic design types is characterized by one or more daily weather cycles, which show the interactions and daily patterns of temperature, humidity, and solar radiation (where applicable). (1) Four cycles represent the basic design type. (a) One for the hottest days and one for the coldest days likely to be found in the basic design areas. (b) Two cycle represent areas where high humidities are a major problem.
Materiel that can operate satisfactorily under all four of these daily weather cycles should be capable of satisfactory performance throughout the areas of the basic design type. (2) The hot climatic design type is characterized by two daily weather cycles, one representing the highest temperatures likely to be found anywhere in the world, and the other representing extremely high dewpoints. (3) The cold climatic design type and the severe cold climatic design type are each represented by one daily weather cycle, the latter representing the lowest temperatures in which materiel operation is required.
Details of the daily weather cycles that make up the climatic design types are given in section II, chapter 2. c. Operational, and storage and transit conditions. In each of the eight daily weather cycles, a distinction is made between operational temperature and humidity conditions, and storage and transit temperature and humidity conditions. (1) Operational conditions. These are climatic conditions in the open to which materiel might be subjected during operations or standby for operations.
Ambient temperature and humidity conditions are those measured under standard conditions of ventilation and radiation shielding in a meteorological shelter at a height of 4 to 6 feet (1.2 to 1.8 meters) above the ground and determined according to the risk policy in paragraph 1-5b. Solar radiation, which might be experienced concurrently with the temperature and humidity, is also stated for many of the climatic conditions.
Although the standard conditions measured in meteorological shelters are usually not exactly the same as the operational environment for materiel, it is necessary to state operational conditions in standard terms so— (a) Measurements have the same meaning in all parts of the world. (b) The great range of variations in response of different materiel to a given climatic condition is not a complicating factor in setting design criteria.
For example, the temperature of the materiel itself may vary considerably from the operational air temperature because of the effects of incoming solar radiation, internal sources of heat, the thermal mass, and the heat transfer characteris- tics of the materials. Most items exposed to the sun will attain higher temperatures than the air temperature. The exact temperature can be obtained through actual or simulated exposure to the appropriate daily cycle, or through the development and use of suitable mathematical models. (2) Storage and transit conditions. These are temperature and humidity conditions materiel might be subjected to in storage and transit situations.
Examples of these situations are— (a) Inside an unventilated field storage shelter. (b) In a railway boxcar. Because of great differences in temperature and humidity in varying storage modes, the severity of the exposure depends upon the choice of storage mode as much as the storage location. This is very important in areas of extreme solar radiation and high humilities. Storage and transit air temperature and humidity may differ from operational temperature and humidity because of the induced effects of heat gains or losses of air in confined spaces.
Where a large thermal mass is involved (e.g., in food storage), the temperature of the stores may be much lower than the storage air temperature stated, and may have little daily variation. Temperature for such a thermal mass is derived by using data from previous similar storage conditions or is determined by actual measurement under current conditions. 1–4. Objective. It is intended that this and related regulations will help the Army achieve the objective of developing materiel that will perform adequately under the environmental conditions likely to be found in the areas of intended use. 1–5. Design and test policy. a.
Areas of potential use for Army materiel include all parts of the world except the Antarctic continent. Standard general-purpose materiel will be designed for safe and effective use under the specified conditions of the basic climatic design type (defined in chap. 2). Materiel for use under the conditions of extreme climatic design types (hot, cold, and severe cold) will be provided by designing— (1) Special materiel capable of such use. (2) Special materiel solely for such use. 3 AR 70–38 • 15 September 1979