Determining Pallet Maximum Working Loads From

Nominal Load Measurements

Marshall S. WhiteWilbur DiblingRalph RupertJohn McLeod

Most Loads on Pallets do not act Like Airbags or Two Rigid Bars as in Draft ISO 8611-1 Tests 1 and 3

Certain Loads on Pallets will “Bridge” across the Pallet Deck.

In Warehouse Racks, Some Loads will Shift Stresses from the Center of the Pallet to the Rack Supports

We Tested Different Load Configurations To Determine The Level Of

Load Bridging In A Warehouse

Rack

We Tested The Following Load Stabilizers• Interlock Stacking

• Stretch Wrap

• Strapping (steel and poly)

• Breakaway Adhesive

• Pallet Tie Sheets

• Stretch tape

We Used Plywood To Simulate Pallets And Used 4 Different

Stiffness Levels of Pallets

5.3 kN per cm of deflection3.6 kN per cm of deflection2.3 kN per cm of deflection1.6 kN per cm of deflection

Each Load Was Lifted 5 Times To Simulate Typical Loosening

Of Load After Palletization

Case Goods, Average Deflections at 4.5 kN

Air

bag

Col

umn

Stre

tch

Tap

eA

dhe

sive

Col

umn,

SW

Tie

She

ets

Col

umn,

ST

Inte

rloc

kIn

terl

ock,

SWIn

terl

ock,

ST

Air

bag

Col

umn

Stre

tch

Tap

eT

ie S

heet

sC

olum

n,S

WA

dhe

sive

Col

umn,

ST

Inte

rloc

kIn

terl

ock,

SWIn

terl

ock,

ST

Air

bag

Stre

tch

Tap

eT

ie S

heet

sC

olum

nC

olum

n,S

WA

dhe

sive

Col

umn,

ST

Inte

rloc

kIn

terl

ock,

SWIn

terl

ock,

ST

Air

bag

Tie

She

ets

Col

umn

Col

umn,

SW

Col

umn,

ST

Inte

rloc

kIn

terl

ock,

SWIn

terl

ock,

ST

Def

lect

ion

(m

m)

0.0

5.0

10.0

15.0

20.0

25.0Low

Medium

Medium-Low

High

Case Goods, Average Deflections at 4.5 kN, Low Stiffness Panel

0.0

5.0

10.0

15.0

20.0

25.0A

irb

ag

Col

um

n

Str

etch

Tap

e

Ad

hes

ive

Col

um

n,S

W

Tie

Sh

eets

Col

um

n,S

T

Inte

rloc

k

Inte

rloc

k,

SW

Inte

rloc

k,

ST

Def

lect

ion

(m

m)

Sacks, Average Deflections at 4.5 kN

0.0

5.0

10.0

15.0

20.0

25.0Ai

rbag

Colu

mn

Colu

mn,

SW

Colu

mn,

ST

Inte

rlock

, SW

Int,

Plas

Strp

Inte

rlock

, ST

Inte

rlock

Airb

agCo

lum

n, S

WCo

lum

nCo

lum

n, S

TIn

terlo

ck, S

TIn

terlo

ck, S

WIn

terlo

ck

Airb

agCo

lum

n, S

TCo

lum

n, S

WCo

lum

nIn

terlo

ck, S

TIn

terlo

ck, S

WIn

terlo

ck

Airb

agCo

lum

n, S

TCo

lum

n, S

WCo

lum

nIn

terlo

ck, S

WIn

terlo

ck, S

TIn

terlo

ck

Def

lect

ion

(mm

)

Low

Medium -Low

Medium

High

Sacks, Average Deflections at 4.5kN, Low Stiffness Panel

0.0

5.0

10.0

15.0

20.0

25.0A

irbag

Col

umn

Col

umn,

SW

Col

umn,

ST

Inte

rlock

,S

W

Int,

Pla

sS

trp

Inte

rlock

,S

T

Inte

rlock

Def

lect

ion

(m

m)

Pails, Average Deflections at 4.5 kN

0.0

5.0

10.0

15.0

20.0

25.0Ai

rbag

Colum

n,SW

Colum

n

Colum

n, T

ape

Colum

n, S

T

Airb

ag

Colum

n

Colum

n, T

ape

Colum

n,SW

Colum

n, S

T

Airb

ag

Colum

n, T

ape

Colum

n

Colum

n,SW

Colum

n, S

T

Airb

ag

Colum

n

Colum

n, S

W

Colum

n, S

T

Defle

ctio

n (m

m)

HighMedium

Medium -Low

Low

Drums, Average Deflections at 4.5 kN

0.0

5.0

10.0

15.0

20.0

25.0Ai

rbag

Colu

mn

Colu

mn,

ST

Colu

mn,

SW

Airb

ag

Colu

mn

Colu

mn,

SW

Colu

mn,

ST

Airb

ag

Colu

mn

Colu

mn,

ST

Colu

mn,

SW

Airb

ag

Colu

mn

Colu

mn,

ST

Colu

mn,

SW

Def

lect

ion

(mm

)

Low

Medium -Low

HighMedium

Blocks, Average Deflections at 4.5 kN

0

5

10

15

20

25

30

Airb

ag

Col

umn

Inte

rlock

Airb

ag

Col

umn

Inte

rlock

Airb

ag

Col

umn

Inte

rlock

Airb

ag

Col

umn

Inte

rlock

Def

lect

ion

(mm

)

Low

Medium -Low

Medium High

The Effect of Load Geometry on Load Bridging During Warehouse Rack Storage on Pallets

Average Pallet Deflection as a Percent of Airbag Deflection

54

100 99

708287

0

20

40

60

80

100

Airbag-noload bridging

Cinderblock-column stack

Sacks-column stack

Cases-column stack

5gal pails-column stack

55gal drums-column stack

Load Geometry

Perc

ent D

efle

ctio

n

The Effect of Load Stabilizers on Load Bridging During Warehouse Rack Storage

of Cased Goods on Pallets

Average Pallet Deflection as a Percent

of Column Stacked Deflection

0

20

40

60

80

100

Column

Stacked

Stretch

Tape

Interlock

Stacked

Pallet

Sheets

Stretch

Wrap

Adhesive Strapping

Load Stabilizers

Per

cent

Def

lect

ion

100 100 8796 94

8061

The Effect of Load Stabilizers on Load Bridging During Warehouse Rack Storage

of Sacked Products on Pallets

Average Pallet Deflection as a Percent of Column Stacked Deflection

108 114100 100

020406080

100120

Column Stacked Interlock Stacked Stretch Wrap Strapping

Load Stabilizers

Perc

ent D

efle

ctio

n

The Effect of Load Stabilizers on Load Bridging During Warehouse Rack Storage

of Column Stacked 5 Gallon Pails on Pallets

Average Pallet Deflection as a Percent of Column Stacked Deflection

52

100 10079

020406080

100120

Column Stacked Stretch Tape Stretch Wrap Strapping

Load Stabilizers

Perc

ent D

efle

ctio

n

The Effect of Load Stabilizers on Load Bridging During Warehouse Rack Storage

of 55 Gallon Drums on Pallets

Average Pallet Deflection as a Percent of Unbound Drum Deflection

52

100

47

020406080

100120

Unbound Drums Stretch Wrap Vertical Strapping

Load Stabilizers

Perc

ent D

efle

ctio

n

Implications of Load Bridging Tests on Estimates of Maximum Working Loads

for pallets as described in Draft ISO TS8611-3

1. Geometry and mechanical properties of the package or container on the pallet affect the maximum working load estimate

2. The types of load binders used affect the maximum working load estimates

3. The tension applied to the load binders affects the maximum working load estimates

Implications of Load Bridging Tests on Estimates of Maximum Working Loads

for pallets as described in Draft ISO TS8611-3

4. The package or container stacking patterns affect the maximum working load estimate

5. The stiffness of the pallet affects the maximum working load estimates

6. Normal movement of the unit load changes unit load stiffness and therefore affects the maximum working load estimates