Method Codes

Method Code: 50
Code Description: Watervaporproof bag with desiccant.
Long Code Description: Watervaporproof protection with desiccant. Items protected in accordance with Method 50 shall be heat sealed in a watervaporproof enclosure with activated desiccant. Unit packs of all of these methods shall also include a humidity indicator. Projections, sharp edges, or other physical characteristics of the item that may damage the watervaporproof bag or container shall be cushioned as required in accordance with 5.2.3. The item shall also be cushioned as required to mitigate shock and vibration, thereby preventing physical and functional damage to the item. Preservative coating requirements shall be determined in accordance with For all Methods of Preservation where the bag is the unit container and the outer/shipping container is a wood box, see 5.2.3(l). When bags are used, the bag size shall be of sufficient surface area to permit two subsequent resealing after item inspection. Unless prohibited in the contract or order, carrying cases or housings, which function as a sealed container, may also be used as the watervaporproof enclosure within which the desiccant and humidity indicator will be placed. Precautions shall be prominently noted on the item cases or housings that the desiccant and indicator cards shall be removed prior to placing the item into use. Requirements for desiccant and humidity indicators are as follows:

a. Desiccant (activated) - The bagged, activated desiccant shall conform to MIL-D- 3464. Type I shall be used unless Type II or III is specified or required because of special characteristics of the item. Desiccant shall be in standard unit sized bags. The desiccant shall be strategically located in the pack so as not to be load bearing. Optimally, it is to be placed in voids of the item or pack interior. Desiccant shall be adequately secured to prevent its shifting or movement or placed in specially designed desiccant baskets affixed to the container interior. Under no circumstances shall desiccant be permitted to come in direct contact with critical surfaces of the enclosed item. The desiccant shall not be unnecessarily exposed to the ambient environment when removed from the sealed desiccant storage container. Removal of the desiccant and its insertion into the unit pack shall be the last action prior to final sealing of the bag or container.

b. Quantity of desiccant - The minimum quantity of desiccant to be used per unit pack shall be computed in accordance with either Formula I or II as applicable. The various values of "X" take into consideration the quality and types of dunnage. The inner container (when applicable) shall be considered in the dunnage calculations.
Formula I - To find units of desiccant for use within a sealed container other than rigid all metal:
U = CA + X1D + X2D + X3D + X4D
Formula II - To find units of desiccant for use within a sealed rigid metal container:
U = KV + X1D + X2D + X3D + X4D
Symbols used above are defined as follows:
U = The number of units of desiccant to be used.
C = 0.011 when the area of the barrier material is stated in square inches.
C = 1.6 when the area of the barrier material is stated in square feet.
A = Area of container (barrier) stated in square inches or square feet.
K = 0.0007 when volume is stated in cubic inches.
K = 1.2 when volume is stated in cubic feet.
V = Volume within rigid metal container in cubic inches or cubic feet.
X1 = 8.0 for cellulosic material, including wood and any other material not noted below.
X2 = 3.6 for bound fibers (synthetic or vegetable fibers bound with rubber).
X3 = 2.0 for glass fibers (fiberglass).
X4 = 0.5 for synthetic foams and rubber.
D = Pounds of dunnage within the container.

Note: Formula II may also be used to determine the units of desiccant required for sealed rigid containers other than all metal, when the sealed enclosure provides a WVTR not exceeding 0.001 gram per 24 hours per 100 square inches, tested in accordance with ASTM D4279 using the constant atmosphere method.

c. Humidity indicators. Humidity indicators shall conform to MS20003. The humidity indicator shall be firmly secured directly behind the inspection window or immediately within the closure seal of the container. When specified, externally mounted humidity indicating elements or devices shall be installed in the barrier or rigid container used to effect the unit pack. Externally mounted color change humidity indicating devices shall conform to SAE AS26860.

All unit packs prepared in accordance with any method of this basic group shall pass the applicable quality assurance tests of tables G-I and G-II.