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structure, such as a sealant web for a stand-up pouch,

without compromising the structural rigidity of the pack-

age. Typically, this structure consists of a sealant ﬁlm

laminated to a stiffer reverse-printed ﬁlm. Pouch makers

are limited on downgauging the sealant ﬁlm by the

rigidity requirements necessary for the stand-up feature

of the package. Through MDO, the stiffness of the sealant

ﬁlm can be increased, while still maintaining sealing

properties, allowing the converter to use a downgauged

sealant ﬁlm without compromising performance. Table 2

shows an example of an MDO sealant ﬁlm, when com-

pared to a standard sealant ﬁlm, that, captures a signiﬁ-

cant yield increase with improvements in mechanical and

optical properties.

When comparing the downgauged MDO and generic

sealant ﬁlms, the MDO ﬁlm provides a 32% increase in

yield, a nearly 800% increase in machine direction mod-

ulus, an over 500% increase in machine direction break

strength, a 40% decrease in transverse direction strength,

similar haze, and better gloss. This ﬁlm forms a seal

with strengths of approximately 5 lb at 2501F sealing

temperature.

An example for the second scenario would be replacing

a polyester ﬁlm with an MDO polyoleﬁn ﬁlm. A speciﬁc

case involves replacing a 0.48-mil PET ﬁlm with a 0.6-mil

polyoleﬁn ﬁlm (2), as shown in Table 3.

While the gauge of the polyoleﬁn ﬁlm is 25% heavier,

the yield (MSI/lb) is improved by 15%. This is due to the

difference in the densities of the two polymers. Additional

beneﬁts include a 90% increase in machine direction

break strength, an anisotropic tear resulting in better

straight-line tear characteristics, the inherent hydropho-

bic nature of the polyoleﬁn, and a heat-sealable ﬁlm.

Signiﬁcant shortcomings of the MDO polyoleﬁn ﬁlm

should be acknowledged, and they include the lack of

thermal stability at elevated temperatures, higher haze,

lower oxygen barrier, and lower transverse direction

tensile properties. As a result, some applications can

utilize the MDO polyoleﬁn ﬁlm and capture the yield

beneﬁt, while others may be limited by the shortcomings

of the MDO polyoleﬁn ﬁlm.

High-barrier ﬁlms for sealant webs or lamination

replacements are a third application where MDO ﬁlms

can be utilized to signiﬁcantly reduce packaging costs (2).

These ﬁlms would be utilized to reduce costs in pouch

applications where the inherent properties of MDO ﬁlms,

such as increased modulus, barrier, strength and gloss,

add value to the ﬁnished package and lower package costs

by reducing the need for secondary processes. The follow-

ing example of a sealable high-barrier MDO ﬁlm combines

excellent moisture and oxygen barrier, good heat sealabil-

ity, high stiffness, high gloss, and low haze (Table 4).

The ﬁlm’s tensile properties are signiﬁcantly higher

than those of laminated polyester structures. In addition,

the high-gloss surface is similar to, if not better than,

other lamination-grade printed ﬁlms and provides excel-

lent aesthetics to the package.

This ﬁlm has oxygen and moisture barrier properties

similar to those of many coated and metalized ﬁlms (9–11),

as shown in Figure 3.

Table 2. Typical Data for a Standard Sealant Film and a

Downgauged MDO Sealant Film

Property Units

Standard

Sealant

Film

MDO

Sealant

Film

Gauge mil 2.0 1.5

Yield MSI/lb 15.0 19.7

MD modulus psi 35,000 310,000

MD break strength psi 4,500 28,000

TD break strength psi 4,000 2,400

Haze % 10 9.0

451 Gloss 65 75

Heat seal temperature

for 5 lb/in. seal

strength

1F 200–250 250

Table 3. Typical Data for Oriented Polyester Film and a

MDO Polyoleﬁn Film (2)

Property Units

0.48 mil

PET

MDO

Polyoleﬁn

Film

Gauge mil 0.48 0.6

Yield MSI/lb 42.2 48.6

MD modulus psi 400,000–

600,000

500,500

MD break strength psi 32,000 60,000

TD break strength psi 39,000 5,600

MD break strain % 110 48

TD break strain % 70 6.7

MD Elmendorf

tear

g/mil 30 11.1

TD Elmendorf tear g/mil 30 54.0

Haze % 3.6 12

Table 4. Properties of a Sealable High-Barrier MDO Film

for the Replacement of Laminated Barrier Structures in

Flexible Packaging (2)

Property Units

Sealable High-Barrier

MDO Film

Gauge mils 2.6

MD modulus psi 230,000

TD modulus psi 170,000

MD break strength psi 13,400

TD break strength psi 3,100

MD break strain % 57

TD break strain % 1,440

MD elmendorf tear g 190

TD elmendorf tear g 250

OTR cc/100 in.

/day 0.091

WVTR g/100 in.

/day 0.314

451 Gloss (print side) 90.1

Transparency % 93.9

Haze % 10.5

Heat seal temperature

for 10-lb/in. seal strength

1F 250

688 MACHINE DIRECTION ORIENTATION

CONCLUSION

Machine direction orientation (MDO) of polymer ﬁlms

provides signiﬁcant improvements in both the cost

and performance of ﬂexible packaging. Signiﬁcant in-

creases in stiffness, strength, optics, and barrier are easily

attained through MDO. Each section of the MDO unit

is critical for the production of high-quality ﬁlm, with

each requiring careful consideration during the equip-

ment design process. Utilizing MDO ﬁlms can reduce

packaging costs through downgauging, replacing less

desirable ﬁlms, and/or reducing the need for more costly

secondary processes in the manufacturing of ﬂexible

packaging.

GLOSSARY OF TERMS

Blocking Blocking occurs when two layers of ﬁlm ad-

here to each other. This is typically seen when a roll is

wound with too high of tension and cannot be easily

unwound. Winding with lower tensions and/or the addi-

tion of an anti-blocking agent to the polymer ﬁlm can

minimize the effects of blocking.

Crushed Core Crushing a core refers to the event

where the paper cores that are used to wind the rolls are

crushed by the ﬁlm that is being wound around them. This

can occur if the ﬁlm is wound with too high of tension and/

or the ﬁlm shrinks after it has been wound on the core.

Crushed cores make it difﬁcult to unwind rolls in second-

ary processes.

Dart Drop The impact strength of the ﬁlm, as measured

by a moving weighted dart.

Draw Gap The draw gap is the distance between the

slow draw and fast draw rolls. The draw gap can be given

either in terms of a radial or tangential distance between

the two rolls.

Draw Ratio (DR) The ratio at which the ﬁlm is being

oriented. Draw ratio is also the ratio of the ﬁlm thickness

before and after the orientation process.

Draw Resonance Draw resonance, also known as tiger

striping, is the presence of thick and thin streaks in the

transverse direction of the ﬁlm. It is a property inherent to

the type of polymer being oriented.

Edge Bead An edge bead is the thick portion of ﬁlm

located at the edges of the roll. Typically, the edge bead is

removed by cutting a small piece of ﬁlm off the edge,

known as trim, prior to winding.

Gloss The amount of light reﬂected from the surface of

the ﬁlm at a speciﬁed angle. Gloss is the shininess of the

ﬁlm.

Haze The percentage of light that is not transmitted

through the ﬁlm. Haze is the lack of ﬁlm transparency.

MDO Machine direction orientation.

Neck-in The amount the width of the ﬁlm changes after

orientation. The neck-in is calculated by subtracting the

width of the ﬁlm after orientation from the width of the

ﬁlm prior to orientation.

Nip Rolls The nip rolls are typically rubber covered

rolls that are used to pin the ﬁlm to the surface of the

heated/cooled roll. Nip rolls are critical for proper tension

control throughout the process.

Orientation Temperature The orientation tempera-

ture refers to the temperature to which the ﬁlm has

been heated by the preheating rolls prior to the orienta-

tion stage.

Proﬁle The proﬁle refers to the thickness of the ﬁlm in

the transverse direction.

Rate of Draw The rate of draw is the rate at which the

ﬁlm is being oriented. It is also referred to as the accel-

eration in the gap. The rate of draw is calculated by

dividing the difference between the fast draw and slow

draw speeds by the tangential distanced of the drawing

gap.

Rate of draw ¼

ðFast draw speed Slow draw speedÞ

Tangential gap distance

Roll Proﬁle Roll proﬁle refers to the uniformity of the

roll in the transverse direction of the ﬁlm.

Metallic PC

PET

Metallic PA

PVdC

Metallic LDPE

Metallic PET

Metallic BOPP

Metallic Cello

MDO

0.01

0.1

100

0.01 0.1 1 10 10

OTR (cc/100 in

/24 hr)

WVTR (g/100 in

/24 hr)

Improving Oxygen Barrier

Improving Balanced Barrier

Improving Moisture Barrier

Figure 3. Water and oxygen transmission rates

for various polymer ﬁlms. Data for all ﬁlms other

than the MDO ﬁlm from references (9–11). Data

for the MDO ﬁlm taken from reference (2).

MACHINE DIRECTION ORIENTATION 689

Trim A small piece of ﬁlm cut from the edge prior to the

winding of the roll to remove the edge bead.

Yield Yield refers to the surface area, typically given in

thousand square inches (MSI) of one pound of ﬁlm (lb).

BIBLIOGRAPHY

1. K. L. Williams, G. Laverde, R. Wolf, and D. R. Breese,

Economic beneﬁts of machine direction orientation, SPE

Polyoleﬁns RETEC Conference, 2005.

2. D. R. Breese, Economic beneﬁts of utilizing MDO ﬁlms in

ﬂexible packaging, TAPPI PLACE, 2007.

3. E. Hatﬁeld, Some of the important design requirements of a

machine direction orientor (MDO) Machine, TAPPI PLACE,

2007.

4. D. R. Breese, G. Beaucage, and K. L. Williams, Modeling the

effects of solid state orientation of blown high molecular

weight high density polyethylene ﬁlms: A composite theory

approach, SPE ANTEC, 2005.

5. D. R. Breese and J. J. Strebel, Balancing tear strength and

modulus of machine direction oriented ﬁlms containing high

molecular weight polyethylene, SPE FlexPackCon, 2006.

6. E. Hatﬁeld, R. Tate, K. L. Williams, and B. Todd, New MDO

Medium molecular weight high density polyethylene ﬁlms,

SPE ANTEC, 2001.

7. E. Hatﬁeld and D. R. Breese, Step change improvements in

barrier using MDO, TAPPI 2006 Innovations in Barrier

Packaging, 2006.

8. D. R. Breese, and G. Beaucage, Effects of machine direction

orientation on the moisture and oxygen barrier properties of

HMW-PE ﬁlms, TAPPI PLACE Conference (2005).

9. S. E. M. Selke, J. D. Cutler, and R. J. Hernandez, Plastics

Packaging: Properties, Processing, Applications, and Regula-

tions, 2nd edition, Hanser, Munich, 2004.

10. A. L. Brody, and K. L. Marsh, The Wiley Encyclopedia of

Packaging Technology, 2nd edition, John Wiley & Sons, New

York, 1997.

11. O. Vetter, Trends and opportunities in the European clear

barrier market, TAPPI PLACE, 2006.

MANAGING THE PACKAGING FUNCTION

AL CORNING

A Corning Consulting, Inc.,

Lombard, Illinois

Ongoing disagreements and/or confusion exists as to

where in the organization packaging best ‘‘ﬁts’’ and,

even worse, a general lack of understanding on the part

of senior management, and other corporate groups, as to

what packaging can or should be doing to best serve that

business.

LOCATION IN THE ORGANIZATION

Where is the packaging function best positioned to serve

the company? Granted, there is no easy answer to this

question. The close relationship with suppliers that are

typically desired or required directs one to elect location

within the purchasing department as optimum. Especially

when one considers the increasing importance of

cost control, cost reductions, speciﬁcation negotiation,

and supplier problem resolution—especially quality

problems.

Cases exist in which the manufacturing function has a

dominant need; and in all cases, packaging must assure

good working relationships with production management

and line personnel.

In essence, there is no one best answer for all, but the

wrong or inappropriate corporate location of the packa-

ging function ensures hampered performance and limited

professional growth or recognition of value.

PACKAGING RESPONSIBILITIES: KNOWN AND

UNDERSTOOD

Perhaps the prime responsibility of a packaging manager

is to understand clearly all that is currently and appro-

priately expected of the function, and, likewise, to educate

upper management, continually, as well as their peers or

‘‘customers’’ in other company functions’ as to what the

department’s capabilities and expected productivity are.

The latter is basis stafﬁng, training thereof, budget, and

assigned priorities.

The emphasis on current expectations is to ensure that

the department manager keeps aware of ongoing changes

in the company and/or industry that continually impact

respective responsibilities and priorities. Those changes

must also be quickly communicated to the packaging staff.

STAFFING

One must expect the typical, and likely ongoing, under-

stafﬁng that exists today has existed for years, and it will

likely continue in the future. This understafﬁng is due

partially to failure to communicate to senior management

the needs, beneﬁts, and cost-effectiveness possible within

the packaging function. ‘‘Cost-effectiveness’’ is a combina-

tion of cost reductions and avoiding major costly claims or

mistakes that impact other corporate functions. This is

concept covered in a later paragraph.

Appropriate stafﬁng is usually a matter of budget

restraints and the collective expectations of the packaging

department. Clearly delineated project assignments and

regular progress reports help emphasize possible under-

stafﬁng. If certain engineers have more work assigned

than they can reasonably handle, then the resultant tardy

results and stress will quickly magnify the need for added

stafﬁng. One cannot emphasize enough the need for

establishing a project priority system as the best measure

of ‘‘appropriate’’ stafﬁng. In essence, continuing failure to

meet objectives and particularly timelines (schedules) will

be a failure of management. That could include depart-

ment managers and their superiors! If added staff is not

made available, then a reduction in priority assignments

is in order if timelines are to be met.

690 MANAGING THE PACKAGING FUNCTION

TRAINING

Because packaging as a whole is both complex and ever

changing, ongoing training programs are of paramount

importance, which include both technical and nontechni-

cal. Good examples of the latter include total quality,

teamwork, the development of leadership thereof, as

well as interpersonal relations and communications.

A need always exists for prompt and optimum deci-

sionmaking. Therefore, everyone in the department should

attend a course in problem analysis and decisionmaking.

They last throughout a career!

Finally, department managers are responsible for

training their successors; the earlier, the better.

BUDGET

The woes of an inappropriate budget are a great teacher

for future budgeting. Properly budgeted departmental

costs, as well as cost reductions, are a key to avoiding

monthly or quarterly stress through the year. Department

managers must take the time to fully understand what is

expected of them in the year ahead, both of themselves

and all others. This understanding helps establish a

budget, which at least allows for a good to excellent

performance. A constant review is essential through the

year as ‘‘surprises’’ come or situations change. The resul-

tant changes in priorities or workload can be deafening

(which refers to the screams from those individuals who

expect a certain level of performance from the packaging

functions).

EDUCATING ASSOCIATES AND SENIOR MANAGEMENT

It can be enlightening to ﬁnd out how little your peers and/

or senior management understand about packaging! The

better packaging is understood, the more likely you can

expect proper recognition and understanding of your

problems in day-to-day affairs.

It is clearly worthwhile to prepare a brief, but thor-

ough, description of what you do and for whom. Also,

consider the beneﬁts of a meeting in which you can

explain in some detail, and others can ask questions to

learn, the complexities and potential of the packaging

functions in your company.

COST REDUCTIONS AND CRISIS AVOIDANCE ($ AND $)

These concepts are two critical aspects of a packaging

department, which impact stafﬁng, growth, and respect.

Every packaging person in the department should have

some cost reduction budget dollars assigned annually,

with a total cost reduction budget of 1–3% annually on

the basis of the total package material expenditures for

that year. Cost reductions affect the corporate ‘‘bottom

line’’ and should get attention at the highest levels,

especially if a year-end summary is sent out with wide

circulation!

Equally important is the avoidance of major packaging

crises, especially claims due to unsalable merchandise.

These claims can, and have, mushroomed into millions of

dollars. Then packaging is in the spotlight negatively!

Good packaging speciﬁcations and the enforcement

thereof, along with participation in vendor screening or

selection, are the responsibility of packaging. Many horror

stories exist about packaging and product claims that

serve to remind us how important the proper package

and package quality are to the marketplace.

PROFESSIONAL GROWTH AND ASSOCIATIONS

Packaging managers should assume responsibility for

their own and the department’s growth professionally

speaking. In addition to the training programs previously

mentioned, opportunities are present to participate in the

local chapter of the Institute of Packaging Professionals

(IoPP). Furthermore, it allows you to become a Certiﬁed

Packaging Professional (CPP) through the IoPP exam.

The CPP program has been modiﬁed to allow more alter-

natives to qualify for the CPP certiﬁcation. This certiﬁca-

tion is truly a matter of personal pride and industry

recognition of your interest in being a professional

member.

PROJECT CONTROL

The packaging manager should assume full responsibility

for projects assigned to the department and their success-

ful completion on a timely basis. The number of projects

accepted and their comparative or assigned priority

should be a direct responsibility of the department man-

ager and should be clearly understood in total by the

manager and the assigned engineer.

This control is a critical basis for good interrela-

tionships between packaging and other departments,

especially new-product development, marketing, and

manufacturing. Such activity often calls on the manager’s

diplomatic skills in explaining current workloads and any

new assignments’ comparative priority.

SELF-DIRECTED PROJECTS

One major means of helping the staff engineer gain

and retain pride in their work is to encourage their

self-initiated projects. This encouragement could, if not

should, involve up to 10% of their time. It certainly

develops a sense of personal pride and professional

growth.

This

might be a

good time to emphasize the beneﬁt of

motivation in the individual engineer. A lack of motivation

to excel and/or improve is a sure sign that something is

awry and needs attention from the department manager.

Such lack of motivation can, and usually does, result in

less than quality efforts, all the way to sloppy or careless

work. The longer it continues unabated, the worse the

results become.

MANAGING THE PACKAGING FUNCTION 691

GLOBAL OUTLOOK

Today’s packaging manager must have a global interest

and awareness. Matters such as new products, materials

or equipment, and cost impact because of impending

worldwide shortages or market glut allow for constructive

planning and activity. Whether this knowledge is primar-

ily from trade magazines, meetings or seminars, supplier

presentation, or whatever, the point is that there must be

sources of global packaging knowledge for packaging

department managers. They, in turn, can sort out the

likely impact on their company products or industry and

keep the management appropriately informed.

PACKAGING SPECIFICATIONS

A ﬁrst step in developing a worthwhile speciﬁcation

program might be ‘‘descriptive’’ speciﬁcations. By deﬁni-

tion, these speciﬁcations describe the package structure

and size. They lack any assurance of quality, or better-

controlled quality, from the vendor. This beneﬁt comes

only from ‘‘performance’’ speciﬁcations that are complete

and negotiated with the vendor to ensure that they are

realistic. They should be signed off by the supplier and

your purchasing department as recognized operating

documents. Many historical examples exist in all indus-

tries of how performance packaging speciﬁcations pre-

vented claims and/or market disasters. Today, with the

constant emphasis on quality, it is the bestway to ensure

that the package is what was planned, tested, and ex-

pected from the package development effort.

CONCLUSION

In summary, the packaging manager has the opportunity

to hire motivated engineers and technicians, implement

an ongoing training program for their growth on the job,

and help ensure optimum department location in the

corporate structure that improves effectiveness as well

as the company proﬁts. The latter is the result of well-

executed cost reductions and claim avoidance, along with

carefully prepared performance packaging speciﬁcations.

Truly, it is a professional effort conducted by a Certiﬁed

Packaging Professional (CPP).

MARINE ENVIRONMENT AND EXPORT

PACKAGING

JOHN P. C OLLETTI

John P. Colletti and Associates,

Pittsburgh, Pennsylvania

PURPOSE AND SCOPE

Before any meaningful discussion can occur about the

preparation of goods for export shipment, there must

ﬁrst be an understanding of the terms ‘‘preservation’’,

‘‘packaging’’, and ‘‘packing’’. These three terms constitute

a total system that, when properly implemented, serves

the following purposes:

To protect cargo from the elements and the normal

rigors encountered in export transportation

To facilitate handling

To provide a degree of rigidity to the cargo

To provide continued protection to the cargo in short-

and long-term storage

This article is intended to offer the shipper a ready

reference on how to prepare a product for export ship-

ment. The fundamentals of preservation, packaging, and

packing, including the selection of materials, are dis-

cussed. Proven methods of construction of skids, crates,

and boxes are presented. The problems associated with

marine transportation and with the use of sea containers

are given special attention.

DEFINITIONS

Preservation is the operation by which goods are protected

from the elements, i.e., freshwater and salt water, heat,

cold, corrosive atmospheres, and humidity. Preservation

usually consists of the direct application of a coating

speciﬁcally designed to protect against a known hazard

such as rust. Other types of preservatives are vapor-

corrosion inhibitors (VCI) and vapor-phase inhibitors

(VPI), which are additives in the form of powder or

chemically treated paper that serve to inhibit the forma-

tion of water vapor and the rust resulting therefrom.

Desiccants are also used as preservatives because they

absorb moisture.

Packaging is an operation that consists of wrapping or

boxing an item as a preparatory step prior to placing the

item into the ﬁnal shipping container. The nature of an

export shipment, i.e., by marine transportation, is such

that the cargo is handled many more times than a

domestic shipment, and for that reason, greater consid-

eration must be given to known or assumed levels of shock

and vibration. The type and extent of packaging depends

on these considerations as well as on marketing require-

ments and segregation requirements. It is usually per-

formed as an intermediate step in the protection of the

item from the rigors of transportation.

Packing is the ﬁnal step in the preparation of goods for

shipment. Packing consists of the outer or external ship-

ping container, whether it is a box, crate, or sea container.

Cushioning, blocking, bracing, and anchoring are addi-

tional protective measures taken within this outer ship-

ping container.

If shippers would view the preparation of their goods

for shipment as a system consisting of preservation,

packaging, and packing and would conscientiously evalu-

ate their goods for susceptibility to the rigors encountered

in marine transportation, their goods would stand a

substantially better chance of arriving at the ultimate

destination in sound condition.

692 MARINE ENVIRONMENT AND EXPORT PACKAGING

VCIs and VPIs, when incorporated in waterproof

packaging, can add a substantial measure of protection

against moisture.

Desiccants are usually moisture-absorbing powders

contained in packages such as boxes or cloth bags. When

placed in relatively watertight or waterproof voids, these

desiccants will absorb excess moisture. They cannot,

however, be expected to continue to absorb water or

moisture beyond their absorption capability; therefore,

the amount of desiccant used must be carefully deter-

mined considering the expected temperature and humid-

ity levels and the volume of the spaces that they are to

protect.

Marks and numbers are extremely important. The

outer or external shipping container must clearly show

certain critical information essential to the safe handling

and expeditious delivery of cargoes to their ﬁnal destina-

tion: The name and full address of the consignee; an

identifying number or code relating to the particular

item being shipped; full dimensions and gross and net

weight in both metric and British systems; and the

appropriate international shipping symbols such as

‘‘Keep dry,’’ ‘‘Fragile,’’ ‘‘This side up,’’ and ‘‘Lift here’’ or

‘‘Sling here,’’ are all part of the labeling requirements (see

also Figure 1).

Unitization is the assembly of cargoes of similar size

and conﬁguration into a single bundle, group, platform,

or pallet. The purpose of unitization is to reduce cubage,

to facilitate handling, and usually to provide a greater

degree of rigidity to the unitized cargoes. The bundling of

pipe, coiled wire, lumber, and structural steel members

are examples of unitization.

Palletization is a special case of unitization and consists

of placing one or more similar units of cargo on wooden

pallets and securing the cargoes to the pallets usually by

means of steel or synthetic fabric tension bands. If re-

quired, overwraps may be applied to the palletized units to

provide either watershed or waterproof protection. Other

common methods of restraining and securing palletized

cargoes are shrink wrap and tension wrap (polyethylene

or polypropylene ﬁlms).

The term protective materials generally refers to contact

preservatives such as paint, grease, and oil or to the

watershed or waterproof liners and wraps applied to protect

the cargo from the elements. Protective materials can also

include cushioning materials and blocking and bracing .

Skids are wooden timbers or alternative materials used

either as a base to facilitate handling for heavy cargoes

where cargoes possess inherent rigidity; or skids serve

alone as a base for cargoes that lack inherent rigidity,

protecting them and facilitating handling. Skids are also

major structural members in crate construction. It is

important to note that if skids are used alone as a base

to carry a cargo with or without inherent rigidity, then

attention must be given to the type of load (i.e., uniform or

concentrated), and the skid must be designed accordingly.

In addition, for economic reasons, skids used as structural

members in true crates can be signiﬁcantly smaller in

cross section than the skids used as support bases because

crate side and top and end panels contribute signiﬁcantly

to the overall strength of the crate.

A wood crate (see Figures 2–7 for examples of open-

crate design) is a structural framework of members fas-

tened together to form a rigid enclosure that will protect

the contents during shipping and storage. This enclosure

is usually of rectangular outline and may or may not be

sheathed. A crate differs from a nailed wooden box in that

the framework of members in the sides and ends provides

the basic strength, whereas a box must rely for its

strength solely on the boards of the sides, ends, top, and

bottom. The crate framework can be considered to be

similar to a type of truss used in bridge construction. It

is designed to absorb most of the stresses imposed by

handling and stacking.

A wooden box is simply a rectangular enclosure that

consists of wooden boards or planks nailed along their

ends or sides to adjacent boards or planks. Boxes generally

do not employ framework such as that used in crates.

However, boxes can and should employ cleats and battens,

which are wooden members that act as nailers and

stiffeners.

The wood species most commonly used in crate construc-

tion are divided into four groups largely on the basis of

density. In general, it is good practice to use species in the

Figure 1. International shipping symbols.

MARINE ENVIRONMENT AND EXPORT PACKAGING 693

same group for similar parts. Group I consists of the softer

woods such as pine, spruce, and chestnut. Group II consists

of heavier woods such as Douglas ﬁr and Southern yellow

pine. Group III woods are generally hard woods of medium

density and possess relatively good nail-holding capacity.

Examples o f these woods are ash, soft elm, and soft maple.

Group IV woods are heavy hardwood species, the heaviest

and hardest domestic woods. They have the greatest capa-

city to both resist shock and hold nails. They are difﬁcult to

nail and tend to split but are especially useful where high

nail-holding capacity is required. Oaks, hickory, birch, and

white ash are examples of Group IV wood.

Wood defects should be carefully considered when

selecting wood for skid, crate, and box construction.

Seasoned wood is preferable to green lumber. Knots and

other various defects, such as slope of grain, decay, wane,

shakes, checks, splits, and warping, are defects that affect

the strength and long-term serviceability of wood. Guide-

lines for selecting wood with defects are contained in great

detail in the USDA Wood Handbook (1) and Wood Crate

Design Manual, Agricultural Handbook No. 252 (2).

Rub strips or runners are lumber strips secured to the

underside of skids and skid-based crates to facilitate

handling. Rub strips are an essential part of skid assem-

blies and crates and in box construction for loads in excess

of 200 lb.

Tension bands are metal or fabric bands or straps used

to secure or bind cargoes to pallets or skid bases or as an

Figure 3. (a) Typical open crate; (b,c) bases for light-duty open

crates [(b) r42 in. wide; (c) W42 in. wide] (2).

Figure 2. Open-crate designs: (a) light-duty open crate (for loads

to r200 lb) with three-way corner nailing, the key to proper

assembly nailing of crates of this type; (b) limited military-type

open crate (for loads r2500 lb) designed for the shipment of light,

bulky items that do not require a waterproof container (2).

694 MARINE ENVIRONMENT AND EXPORT PACKAGING

added measure of binding the external members of crates

and boxes. Tension bands are manufactured in a variety of

dimensions and are applied by means of mechanical or

hydraulic tensioning equipment. Tension bands are also

an essential part of good packing.

Reinforcing straps (see Figure 8) are mild steel metal

bands ﬁtted with nail holes and can be afﬁxed at the

corners of crates and at the junction of side-panel vertical

members and top-panel horizontal members. Reinforcing

straps should be applied in two directions where possible.

Figure 4. (a,b) Typical nailing patterns;

MARINE ENVIRONMENT AND EXPORT PACKAGING 695

Figure 5. Crate components and ﬁnal assembly (2).

696 MARINE ENVIRONMENT AND EXPORT PACKAGING

These straps serve as an added measure to prevent the

separation of joints.

Headers are timbers or alternative materials that are

bolted across the end of skid assemblies. Generally, they

are to be of at least the same cross section as the skid

members they join. Headers are an essential part of skid

assemblies in skids acting alone as well as skids serving as

part of a crate.

Load-bearing ﬂoorboards are wooden members or al-

ternative materials that are fastened transversely across

the tops of skid assemblies and carry the load of the item

for which the skid assembly is intended.

Splicing refers to the joining, end to end, of two lengths

of timbers of similar cross section to make one longer

section with approximately the same longitudinal

strength as a single continuous piece. The ends to be

spliced are to be notched to half the timber thickness,

and through-bolts are to be placed vertically through

the joining notched sections. Lapped along each side of

the splice is to be a

-in. steel plate of length no less than

three times the thickness of the members joined and

through-bolted, side to side, with at least two bolts in

each half of the splice.

A uniform load refers to a load that is distributed more

or less evenly over the entire unsupported length of the

member on which it rests. As was pointed out above,

consideration must be given to the type of load, i.e.,

uniform or concentrated, when determining the size of

members to be used as skids and load-bearing ﬂoorboards.

A concentrated load is a load that is not distributed

evenly over the unsupported length of the member on

which it rests. Rather, it is centered over a shorter

segment of the member on which its rests, which results

in a bending moment higher than that produced by a

uniform load of similar magnitude.

Rigidity refers to a strength property of materials that

allows them to resist deformation such as longitudinal

bending or racking. For example, a 20-in.-diameter pipe

with

-in. wall thickness and length of 20 ft may be able

to be picked up by a sling at its midlength without any

noticeable deformation, whereas a 2-in.-diameter pipe

with wall thickness of

in. and length of 20 ft would

droop noticeably if lifted with a sling at its midlength.

Items with no inherent rigidity, which are intended for

export shipment, should be skidded or crated to facilitate

handling and prevent damage.

Fragility is a term used to describe the degree of

susceptibility to damage from the normal rigors of trans-

portation, i.e., shock and vibration.

The Bending moment, as used within the scope of this

article, refers to the product of a load acting over a

distance to produce deformation of a structural member

that is subjected to the load at some point along its length.

The load may be uniform or concentrated as described

above. As an example, consider a beam supported only at

its extreme ends and subjected to a load at its midlength

such that the resultant of the load acting downward and

the reaction forces at the extreme ends acting upward is a

sagging of the beam. What actually happens here is that

the ﬁbers of the beam in contact with the load are in

compression, whereas the ﬁbers on the underside of the

beam opposite the load are in tension. The bending mo-

ments described above can be written in the form of the

mathematical expression

BM ¼

ðft lbÞ

where BM is the bending moment, W is the applied load, L

is the unsupported length of the beam, and the denomi-

nator 4 takes into account that W is a concentrated load.

Similarly, the mathematical expression for the bending

moment resulting from the application of a uniformly

distributed load on the same beam

BM ¼

ðft lbÞ

Figure 6. Assembly of (a) light-duty open crate; (b) covered-style

light-duty open crate (2).

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