Shipping product to the DLA Warehouse in excess of 250 lbs. or 20 cubic feet requires us to palletize our loads in accordance with MIL-STD-147E.
The maximum weight of a load, including the pallet, bonding methods, stability dunnage, and units, shall not exceed 3,000 lbs. per single pallet load (¶ 188.8.131.52). Unit loads shall not exceed 52" x 43" x 54" in size (¶ 5.1.2).
The standard pallet is 48" x 40" x 5", so units should be stacked without overhand a maximum of 49" high.
As our shipping containers are fiberboard boxes stacked in single or multiple layers, our load type is Ia (¶ 5.2). This load type is what determines the extent of stacking and bonding methods are used to secure the load during shipment. We use a combination of Bonding Method D (tie-down straps) and Bonding Method G (stretch wrap) to secure our loads, with Stability Dunnage 2 (nonmetallic edge protectors) to protect containers from bonding methods.
Load Stability and Stacking
When stacking uniform sized containers in columns on a pallet, a sheet of paper should be placed between every other layer to increase load stability. 50-pound basis weight kraft paper should be used for lightweight containers under 10 lbs, or weather-resistant single-wall corrugated fiberboard conforming to ASTM D4727/D4727M for heavier containers (¶ 5.1, 184.108.40.206).
The top surface of the loading pallet shall be level, or made level with a wooden top frame or leveling board, for stacking purposes (¶ 5.1).
Containers shall be stacked to form a compact squared load centered on the load base and shall be square with all corners of the pallet. Stability dunnage shall be used to fill any voids or gaps in containers to be even with the side or ends of the pallet (¶ 5.1).
Load Bonding - Strapping
Loads are strapped to compact and bond the load under tension (Bonding Method D).
There are four different types of straps: horizontal, primary, secondary, and auxiliary (¶ 3.35):
- Horizontal straps are secured around the load parallel to the pallet deck. These straps are positioned on each layer in excess of two.
- Primary straps pass over the load and under the length of the pallet deck inside the outboard pallet stringers.
- Secondary straps pass over the load and through strapping slots in the stringers, if the pallet has them.
- Auxiliary straps are those that are not primary or secondary straps. Only the first two straps in either direction that go over the top of the load and under the pallet deck (tie-down straps) are considered primary or secondary, with additional straps being auxiliary. This is also true of any straps that go over the top of the load but not under the pallet deck.
Nonmetallic strapping and strapping seals shall conform to ASTM D3950 (¶ 220.127.116.11). The strap size is dependent on the weight which must be borne by each strap. The size of a tie-down strap (primary and secondary straps) is determined by dividing the gross weight of a load by the number of tie-down straps. Likewise, the size of a horizontal strap is determined by the gross weight of the layer it is securing (¶ 18.104.22.168).
We use a 1/2" x 0.024" polypropylene strap rated for 500 lbs. break strength, which provides over double the minimum breaking strength requirement for a pallet of Drip Torches, which weighs roughly 450 lbs. and is secured by two primary straps.
Seals are used to hold strap tension (¶ 22.214.171.124). Seals must be steel with a corrosion protective coating (zinc or black iron oxide) (ASTM D3950). The strapping material referenced above uses a 1/2" open galvanized metal seal from Uline.
Straps are secured to the load in the following sequence (¶126.96.36.199.1):
- If the load has more than two layers, secure each layer with horizontal straps beginning with the lowest layer of the load and working upward (¶ 188.8.131.52).
- Next, apply primary and secondary straps, with the first strap spanning the greatest number of units. Secure straps in an alternating fashion, with the second strap positioned at a right angle to the first and the third strap paralleling the first strap.
- Auxiliary straps are secured last.
Edge protectors are used in conjunction with straps at corners or edges of containers (Stability Dunnage 2). They must be weather-resistant single-wall fiberboard with a minimum 3 inches square in size (¶ 184.108.40.206.2). When using edge protectors in conjunction with primary straps, they should be positioned so the edge protectors will bridge two rows of units, if practicable, to create integral bonding (¶ 220.127.116.11).
Load Bonding - Wrapping
Once the load is secured by strapping, 90 gauge (0.9 mil) clear polyethylene stretch wrap is wrapped around the load multiple times, ensuring a uniform tension exists throughout the load (Bonding Method G). Wrap the load from the top of the bottom deckboard in a spiral around the load, and optionally fully wrap around the top of the load. The minimum wrap thickness depends on the weight of the load (¶ 18.104.22.168):
- Up to 1,000 lbs. needs wrapped 3 times (2.7 mil)
- Up to 2,000 lbs. needs wrapped 5 times (4.5 mil)
- Up to 3,000 lbs. needs wrapped 6 times (5.6 mil)