528.1-11 scope

528.1-1 INTENDED USE

• a. This Method is used to qualify shipboard equipment for the environmental vibrations and internally excited vibrations encountered during operation of the equipment aboard ship.
• b. In some special machinery, equipment, or installations (such as antennae, large machinery items, and certain unique designs), it may be necessary to deviate from this Method.
• c. Type I vibration testing is intended to qualify new equipment for exposure to shipboard vibrations during the lifetime of the ship (approximately 30 years).
• d. The primary purpose of Type I vibration testing is to prove the physical and functional integrity of equipment when subject to a prescribed steady-state vibration environment. The results of the application of this Method do not provide a definitive determination of the test item’s natural frequencies and mode shapes.
• e. This Method does not cover vibrations associated with reciprocating machinery, or those associated with propulsion and shafting. For these types, see MIL-STD-167-2A.
• f. The primary purpose of the application of this Method to Type II vibrations is from the standpoint of mechanical suitability, and not from a structure-borne noise standpoint. See MIL-STD-740-2 for noise suitability of equipment.

528.1-1 SCOPE

528.1-1 INTRODUCTION

This Annex attempts to provide reference information related to worldwide and regionalized climatic extremes. There are two basic sources for this information, MIL-HDBK-310, and “Weather and Climatic Extremes.” Much of the information is captured in Section III of this document. The information in this Annex is not intended to be used as design or test data, but rather to provide guidance for consideration when developing Life Cycle Environmental Profiles (LCEPs).

528.1-1 TERMS. (AR 70-38)

I. TERMS. (Fig. 76 56) The following terms apply to this Part.

528.1-1 RELATIONSHIP BETWEEN AR 70-38¹ AND MIL-HDBK-310*

528.1-1.1 Purpose

This document provides planning guidance for realistic consideration (starting points) of climatic conditions in the research, development, test, and evaluation (RDTE) of materiel and materials used throughout their life cycles in various climatic regions throughout the world. It is intended that this and related documents will help achieve the objective of developing materiel that will perform adequately under the environmental conditions likely to be found throughout its life cycle in the areas of intended use.

528.1-1.1 Climatic design types

Four climatic design types are differentiated based on worldwide temperature extremes. They are:

• a. Hot climatic design type.
• b. Basic climatic design type.
• c. Cold climatic design type.
• d. Severe cold climatic design type.

Areas of the world where these types apply are shown in Figure 1. The climatic values included in the design types represent the extreme conditions that items of materiel are likely to encounter in the field, with allowance for some risk (see Annex C, paragraph 1.2).

528.1-1.1 Background

AR 70-38 and MIL-HDBK-310 are the Army and DoD documents, respectively, that provide environmental information and data for the derivation of design criteria through the tailoring process. The two documents are similar in many respects. Both publications reflect a philosophy that accepts a small risk of failure during periods of extreme weather. They also require a complete return to operation after exposure to extreme conditions has ended. MIL-HDBK-310, however, considers only the likelihood of natural extremes occurring, whereas AR 70-38 considers the induced conditions many items are exposed to during transit and storage. This difference means that Army materiel must be able to withstand much higher air temperatures than those in MIL-HDBK-310, although the high temperatures for operation are the same. The principal differences between the AR and the MIL-HDBK are:

• a. The MIL-HDBK is limited to climatic information only (with the exception of blowing sand and dust that is a combination of soil and climatic conditions), whereas the AR provides additional guidance for terrain factors and weather related atmospheric obscurants.
• b. The MIL-HDBK provides data and guidance for both worldwide and regional applications, whereas the AR divides the land areas of the world into design types, some of which are subdivided into multiple daily weather cycles. Prior to the 1987 edition, there were no regional types given in MIL-STD-210. The regional types of the “C” version were derived from the 1979 edition of AR 70-38. Although the AR does not specifically state worldwide values, they can be derived by using the most extreme values from the most extreme daily weather cycles (hot and severe cold) for each climatic element.
• c. The MIL-HDBK provides guidance and data for coastal/oceanic conditions and upper air conditions, neither of which is covered by the AR. The oceans and upper air are, by tradition, primarily areas of concern for the Navy, Air Force, and Army users who have need for such information should consult MIL-HDBK-310. (Its predecessor, MIL-STD-210, was prepared by the Geophysics Laboratory of the United States Air Force Systems Command).
• d. The MIL-HDBK is tailored in a somewhat different manner than the AR. The former does not provide values for storage/transit conditions, whereas the Army approach is that some guidance in this area is needed. The AR provides one level of risk for operational conditions and a second level for storage/transit conditions. The MIL-STD provides several levels for operational conditions and another level for what is referred to as withstanding conditions. These different risk levels in the MIL-STD are described as follows:
• (1) Frequency-of-occurrence values. These are for use in most operational circumstances, and are presented as 1.0, 5.0, 10.0, and 20.0 percent (or other, if appropriate) risk levels for the worst month in the most severe area of occurrence.
• (2) Long-term climatic extremes. For most climatic elements, values are given that are expected to occur at least once, for a short duration (less than 3 hours) during approximately 10, 30, or 60 years of materiel exposure. These are much rarer events than those cited for the frequency-of-occurrence values above. Their use should be limited to specifying conditions that materiel must be able to withstand, but not for which it is expected to be operational. These are generally derived by extreme-value statistical analysis.
• (3) Absolute extremes. The most extreme value ever recorded (not necessarily the most extreme that has ever occurred) is also provided for each element. These are for use when it is determined that materiel should be designed to operate in the most severe conditions it is ever likely to encounter (assuming this is within technical capabilities). Generally, this would be the case only when disastrous consequences would result from failure to operate.

When greater detail is required for the tailoring process, suggest users of AR 70-38 look for corresponding climatic

MIL-STD-810H

PART THREE ANNEX C

elements in MIL-HDBK-310 that will provide a wider range of values at different risk levels for design application.

528.1-1.2 Part Three Organization

Part Three has been structured such that it follows the logical sequence of events leading to an environmental test program.

• a. Section I - Introduction.
• a. Section I - Introduction. b. Section II - Distribution of the Climatic Design Types.
• c. Section III – Natural and Induced Environment - Various Elements.
• d. Section IV - Referenced and Related Documents.
• e. Annex A - Weather and climatic extremes.
• f. Annex B - Discussion of Terminology Used in this Part.
• g. Annex C - Comparison of AR 70-38 with MIL-HDBK-310.

528.1-1.2 Daily weather cycles

11.2 Daily weather cycles. Each of the climatic design types is characterized by one or more daily weather cycles, that show the interactions and daily patterns of temperature, humidity, and solar radiation (where applicable).

• a. Four cycles represent the basic design type.
• (1) One for the hottest days, and one for the coldest days likely to be found in the basic design areas.
• (2) Two cycles represent areas where high humidity is 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.
• b. 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.
• c. 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 paragraph 4 in the front portion of this Part.

528.1-1.2 Risk policy

In the Ground Environment section, MIL-HDBK-310 contains single worldwide values for each climatic element to be considered in the design of materiel for operations. For most climatic elements, the design value selected was the value exceeded not more than one percent of the hours in the most extreme month in an average year at the most severe location for that element. (For low temperature, the level selected was 20 percent of the hours and, for rainfall, the level selected was 0.5 percent of the hours.) These values have become known as one percent design values. When they are applied collectively, they are often referred to as a one percent risk policy. Although this is a convenient short designation, it can be misleading to those who are not aware of this specific definition of a one percent risk policy. In fact, there is no way to quantify, with any degree of accuracy, the probability that materiel will ever encounter a given extreme of an environmental element. It can be stated with assurance that the designated one percent risk levels as used in MIL-HDBK-310 are very conservative. For example, on a year-round basis, the risk of encountering the design level of a selected element approaches 1/12 of one percent (there is some likelihood of occurrence in other than the most extreme month). Also, for many of the climatic elements, the design value applies only to the most severe location in the world. Therefore, the risk of materiel encountering this extreme may be very small, particularly if the value at the most severe location is representative of only a small area or the location is in a remote part of the world.

The above considerations led to the adoption of the system now used in AR 70-38. It provides alternate design values for items not intended for worldwide use. Consequently, the world was divided, on the basis of temperature, into four types. The design temperatures in this four-type division are somewhat arbitrary. However, the geographic areas encompassed by the basic design type contain most of the world's population and landmass. In general, the lines delimiting the areas included in a design type are drawn on the basis of having one percent of the hours in the most severe month on average exceeding the design temperature. Note, it is only along the demarcation line that this criterion applies exactly. For example, if more than one percent of the hours in the coldest month at a given location are below -46°C (-50°F), the area represented by that location is considered part of the severe cold climatic design type. Yet, at that location, there may be almost no chance of occurrence of -51°C (-60°F), that is the lower design value for that type. On the other hand, there are stations in the areas included in the severe cold design type that have temperatures below -51°C (-60°F) for as much as 20 percent of the hours in the coldest month. This kind of variation within the regions could be eliminated only by creating a large number of small regions, a procedure that would make this delineation unduly complex.

528.1-1.3 Application

528.1-1.3 Operational, and storage and transit conditions

In each of the seven daily weather cycles, a distinction is made between operational temperature and humidity conditions, and storage and transit temperature and humidity conditions.

• a. 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 1.2 to 1.8 meters (4 to 6 feet) above the ground and determined according to the risk policy in paragraph 6.2. Solar radiation that 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:
• (1) Measurements have the same meaning in all parts of the world.
• (2) 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 characteristics 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.

MIL-STD-810H PART THREE ANNEX B

• b. Storage and transit conditions. These are temperature and humidity conditions to which materiel might be subjected in storage and transit situations. Examples of these situations are:
• (1) Inside an unventilated field storage shelter.
• (2) In a railway boxcar.
• (3) Dump stored in the open.

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 humidity. 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 studies of similar storage conditions, or is determined by actual measurement under current conditions. Life Cycle Environmental Profiles (LCEPs) and requirements documents must be derived for specific systems to generate sets of design and test criteria. Procedures for preparing LCEPs are found in Part One of this document, along with guidance on other environmental engineering tasks.

MIL-STD-810H PART THREE ANNEX C

PART THREE ANNEX C - Comparison of AR 70-38 with MIL-HDBK-310

528.1-1.3 Additional guidance

A general discussion such as this one cannot possibly address in detail the environmental considerations for all materiel. Thus, users are encouraged to seek additional or more specific guidance from the proponent agency.

MIL-STD-810H

PART THREE ANNEX C

Custodians: Army - TE Navy - AS Air Force - 11

Preparing activity: Army - TE (Project ENVR-2018-004)

Review activities: Army – AI, AR, AT, AV, CE, CR, EA, GL, MI, MT, SM Navy – CH, EC, MC, OS, SH, YD Air Force – 19, 85

NOTE: The activities listed above were interested in this document as of the date of this document. Since organizations and responsibilities can change, you should verify the currency of the information above using the ASSIST Online database at https://assist.dla.mil/.

The Preparing Activity responsibility for MIL-STD-810 transferred from Air Force Code 11 to Army Code TE on 14 November 2008.

528.1-1.4 General Guidance

1.4.1 Thoroughly explore the anticipated life cycles, including periods of transportation, storage, and use. For specific systems, detail these periods in a Life Cycle Environmental Profile (LCEP) that will guide materiel development and testing activities.

1.4.2 Because climatic requirements can have a substantial impact on acquisition and support costs, consider designing, developing, and testing materiel to operate under conditions less severe (e.g., 1 percent high temperature values) than the absolute extremes that may occur within the areas of intended use. This implies there is some risk of failure to operate at times. (See paragraph 6.2 for discussion of risk levels.) The four climatic design types outlined in paragraph 2 all contain some element of risk.

1.4.3 Fully and creatively exploit testing in climatic chambers before testing in the natural environment (unless such testing is impractical, e.g., physical limitations, mobility requirements, soldier/system requirements, etc.), to determine basic problems that can occur before natural environment tests are conducted. Test results from climatic chambers, however, cannot be interpreted as a total substitute for tests conducted in natural environments because, among other things, they do not reproduce all of the interacting factors or synergies associated with the natural environment, concurrently. Both chamber tests and field (natural) tests serve useful purposes. Normally, chamber tests should not be substituted for natural environment tests; chamber tests attempt to replicate the effects of the environment and not the environment itself.

1.4.4 Select sites for field testing, if possible, to induce representative deterioration rates and performance challenges from all environmental effects that the materiel will be expected to encounter throughout its life cycle. Plan the natural environment exposure to coincide with the respective climatic extremes. When time and funding constraints permit, select sites with the highest materiel deterioration rates or most severe conditions.

1.4.5 Consider the interaction of materiel with the environment in all phases of RDTE because the induced conditions may be quite different from those of the natural environment. Design sheltered materiel to operate under the conditions within the shelter during operation in the stipulated areas. This includes storage conditions within the shelter without environmental control, and operational conditions with environmental control. Design sheltered materiel to withstand environmental effects that occur during unsheltered storage and transit.

1.4.6 Design potentially dangerous items (e.g., ammunition and explosives) to meet safety requirements for all climatic design values despite their chance of being used or the requirement to operate in those climates. An item developed for the basic climatic design type may fail in the more severe climatic conditions of the hot, cold, or severe cold types and, in some cases, produce catastrophic or extremely hazardous results.

MIL-STD-810H

PART THREE SECTION II – DISTRIBUTION OF CLIMATIC DESIGN TYPES