(THIS IS AN EXCERPT OF MIL-D-3464 MILITARY SPECIFICATIONS AS PROVIDED BY THE US GOVERNMENT. FOR THE COMPLETE AND CURRENT DOCUMENT, VISIT THE US DEPARTMENT OF DEFENSE ASSIST.DLA.MIL)

MIL-D-3464E
21 April 1987
SUPERSEDING
MIL-D-3464D
17 May 1966

MILITARY SPECIFICATION

DESICCANTS, ACTIVATED, BAGGED, PACKAGING USE AND STATIC DEHUMIDIFICATION

This specification is approved for use by all Departments and Agencies of the Department of Defense.

1. SCOPE

Scope. This specification covers bagged, chemically inert, dehydrating agents that prevent corrosion and mildew by adsorbing the moisture from the air of an enclosed space.

2. REQUIREMENTS

Qualification – Bagged desiccant furnished under this specification shall be products which are authorized by the qualifying activity for listing on the applicable qualified products list at the time set for opening of bids.

Material

– Desiccant. The desiccant shall be newly manufactured and shall be nondeliquescent.

– Definition of desiccant unit – Desiccant will be purchased on the basis of adsorption capacity. A desiccant unit is that quantity of desiccant, as received, which will adsorb at equilibrium with air at 25 degrees Celsius (“C) at least the following quantities of water vapor:

(a) 3.00 grams at 20 percent relative humidity (R.H.) , and
(b) 6.00 grams at 40 percent R.H.

Unit weight – The weight of desiccant constituting a desiccant unit is defined as the unit weight. Unit weight shall not exceed 50.0 grams. Unit weight shall be specified by the manufacturer when submitting qualification samples, and shall be verified by the qualifying laboratory using the methods specified. The unit weight thus approved shall be used in all subsequent inspections.

– Unit adsorption capacity (equilibrium conditions). The actual weight of water vapor adsorbed by a unit weight of desiccant in equilibrium with air at 25°C, when tested, is defined as the unit adsorption capacity.

– In qualification tests, unit adsorption capacity shall be at least:

(a) 3.00 grams at 20 percent R.H. , and
(b) 6.00 grams at 60 percent R.H.

– When testing a bagged desiccant, an allowance shall be made for normal manufacturing variations. In connection with such inspection testing, unit adsorption capacity shall be at least :

(a) 2.85 grams at 20 percent R.H., and
(b) 5.70 grams at 60 percent R.H.

Unit volume – The volume of desiccant constituting a desiccant unit is defined as the unit volume. Unit volume shall be not greater than 45.0 milliliters (mL) when tested.

Unit content per bag – The number of desiccant units contained in each bag (unit content) shall 1 be clearly marked on the bag label. When tested as specified, bags of desiccant shall actually contain at least 95 percent of the number of units indicated on the bag label.

Unit adsorption rate – When tasted as specified, the bagged desiccant, as received, shall adsorb in 7 hours the weight of water vapor in accordance with table I.

TABLE I. Unit adsorption rate requirements.

Bag size, units
At 40 percent R.H.
(gram minimum)
At 80 percent R.H.
(gram minimum)
16 and smaller sizes
0.25
0.70
Humidity control – A unit of desiccant shall prevent a closed metal box from exceeding 60 percent R.H. , when tested.

Adsorption capacity and rate after reactivation – After the reactivation and tests specified, bagged desiccant shall retain at least 90 percent of the original unit adsorption capacity, and at least 80 percent of the original unit adsorption rate. Reactivation conditions shall be recommended by the manufacturer. However, the reactivation temperature shall be not less than 245°F (118.3°C), and the time for each reactivation shall not exceed 24 hours.

Dusting

– Type I (all sizes) and type III (8 and 16 units). When tested as specified, the weights of dust found shall be in accordance with table II.

TABLE II. Dusting requirements.

Bag Size Units
Number of bags tested
At least six of the dust values shall not exceed (mg)
At least eight of the dust values shall not exceed (mg)
No more than two dust values shall be in the range (mg)
No more than one dust value shall exceed (mg)
16
8
4 and smaller
12
12
12
5.0
2.5
—
—
—
0.5
60.0 to 200.0
60.0 to 200.0
60.0 to 200.0
200
200
200
– Type II. When tested as specified, type II desiccant shall produce not more than 1/2 milligram of dust, regardless of bag size.

Corrosiveness – The bagged desiccant and the desiccant by itself in contact with steel, brass, magnesium, and aluminum shall show no increase in corrosion when tested.

Bag durability

– Types I, II and III. Bags in which the desiccant is packaged shall not puncture, tear or burst, and the tie strings shall not break when tested.

– Type III only. Bags in which the desiccant is packaged shall not puncture, tear or burst nor show visible evidence of leaching of the desiccant through the bag materiel when tested as specified. The test water used for immersion shall contain not more than 5 milligrams of non-combustible material per 8 units of desiccant when tested.

Resistance of bagging material to reactivation temperature – When reactivated and tested as specified, the desiccant beg shall not puncture, burst, or othervise fail.

Bag size – Type I and 11 desiccants shell be furnished in bags in the fractional unit sizes of 1/6, 1/3, and 1/2; tbe unit size 1, and the multiple unit sizes of 2, 4, 8 and 16 as specified.

– Type III desiccant shall be furnished in bags in the multiple unit sizes of 8 and 16 as specified.

Tie strings – Unless otherwise specified in the contract or order, bags of 16-unit size or larger shall be provided with tie strings having a minimum length of 7 inches.

Particle size – The particle size distribution shall be as shovn in table III .

TABLE III. Particle size.

Sieve number
Distribution, percent
1/2 inch *1
80
Retained (max) 0.0
Retained (max) 96
*1 The permissible variation in average openings shall be 3 percent. The permissible variations in maximum openings shall be 5 percent. The wire diameter shall be 0.094 to 0.122 inch.

Bag markings – Each desiccant bag shall be marked durably and legibly with the following information:

Nomenclature: Desiccant, Activated, Bagged, Packaging Use and Static
Dehumidification
Specification: MIL-D-3464
Type I, II, or III, as applicable
Manufacturer’s designation
Unit content _____________________
Reactivation temperature in bag __________°F
Reactivation time ____________hours
Manufacturer’s name and address

PROTECT ESD - MIL-PRF-81705