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long-established practice of describing cans in English

measurements is now more or less unique to North

America, but it is well understood in Western Europe.

For instance, 112 signiﬁes 1 and 12/16 in. in diameter,

while 214 indicates 2 and 14/16 in. for the height from the

base of the bottom double seam to the top of the top double

seam. For tinplate (or steel) cans not having a top double

seam, the height measurement is the total height to the

top of the can curl.

Well-known examples of can dimensions are A, which

is 1.00070.004 in. (25.470.1 mm) for all can sizes and

metals, and B, which is 1.23270.010 in. (31.370.25 mm)

for tinplate cans of all sizes. These particular dimensions

are quite critical because the valve cup must ﬁt rather

perfectly into the ‘‘1-in.’’ can opening to avoid jamming

or scraping and to allow a good hermetic seal when

crimped. The outer wall diameter of the valve cup is

B0.99270.003 in. (25.270.08 mm), and this leaves a con-

tingency clearance of only 0.001 in. (0.025 mm) between

the largest cup and the smallest hole. This is important

not only for ﬁt, but to anticipate traces of out-of-round,

metal dimpling and other factors. The B dimension is

important in making the top rim and shirt of the standard

valve cup ﬁt snugly to the can bead, increasing the

statistical probability of a good seal. See the article

‘‘Pressure containers’’ for more information.

Seams

The tinplate can has three seams, which can occasionally

become matters of concern. Aside from aesthetics, if can

leakage occurs, it will often be at the side seam and will

more rarely be at the top or bottom double seams. The side

seam is also a favored site for can corrosion, due to

exposed iron and the relatively poor coverage of side-

seam enamel stripes, if applied. The dimensions of the

top and bottom double seams are about the same, for a

given can diameter. Small-diameter side seamed cans (35,

38, and most importantly 45 mm) have smaller-size double

seams than the larger cans. In fact, the 35- and 38-mm

Table 2. Surface Coatings (or Linings) for Aluminum Aerosol Cans

Exterior coatings are applied by offset printing.

The Base Coat . Selected for adherence to the metal, absence of crazing, radia fracturing, and blistering during the oven-

curing process.

. Appearance aspects:



High-opacity white or colored enamel.



Clear or clear-tinted lacquer.



Pearlized lacquer.



Metallic lacquer.

. Selected for a relatively low curing temperature.

The Decorative Coat . May be applied, up to 7 or 8 colors, in a single operation.

. Special effects include:



Half tones.



Color gradation.

. Transparent lacquers, often showing brushed metal.

The Exterior Coat . Hard, protective varnish, usually glossy but sometimes matte.

Interior linings are applied by three-stage spraying of the ‘‘cup,’’ before die-forming the can dome and curl.

. Epon-phenolic are the most common.

. Organosols (as ‘‘Microﬂex’’) are preferred for mousse.

. P.A.M. (polyimideamides) are very resistant.

Maximum

snap-lock

diameter

N Dia.

20°

1.375″  Ref

Figure 1. Straight-wall aerosol can (standard tinplate).

28 AEROSOL CONTAINERS

cans actually have no top double seam; the metal (side

seam and all) is smoothly formed into the ‘‘inch–inch’’ curl.

Figure 3 can be used to illustrate the general shape and

important elements of a typical side seam. In general,

these seams are about 0.125 in. (3.2 mm) high, from seal-

ing wall radius to end hook radius, if the can is 52 mm or

larger in diameter.

Description

The United States and Canada use a ‘‘sales description’’

method for indicating can overall dimensions that is based

on the English (inch) measurement system. England is

changing over to the metric system to conform to the ISO

descriptions used in the rest of Europe and generally

throughout the rest of the world. Australia and Canada

have taken steps in the same direction.

The U.S. ‘‘can description’’ system can be best described

by illustrations. The 202 can is one with a body diameter

of 2

in., or 2.125 in. The ISO diameter (actually the

inside diameter of the body) would be 52 mm.The U.S. can

height is dimension D (see Figure 1 or 2), measured as

total body height over the two seams. A 612 can would

then have a body height of 6

in., or 6.250 mm. The

system extends to such descriptions as 211 1208 and

207.5 605. Seeds of change are being sown in the United

States by the United Nations and other international

groups, but the system is deeply ingrained and is likely

to persist.

CAN-MAKING TRENDS

The three-piece aerosol can is highly serviceable and is

produced by the daily use of heavy equipment valued in the

multi-billion-dollar range. There are no massive changes

predicted during the next decade. The aerosol dispenser

has been accused of having about the same cylindrical

shape it had over 40 years ago. Minor improvements—

such as necking-in, welding side seams, plastic labeling (to

cover the side seam scar), and the ‘‘ecogorge’’ indentation on

some aluminum cans, for the attachment of full-diameter

caps—have been relatively unnoticed by consumers. To

them the aerosol is a cylindrical package, although some-

times with a variously convoluted top portion.

The cylindrical image is an architectural necessity for a

pressure-resistant dispenser (see also Pressure contain-

ers). Even though glass aerosols had somewhat wider

limits, the underlying shape limitations have been a factor

in having nearly all the perfume and cologne business

transfer to nonpressurized glass pump sprayers and other

containers. However, some advances have been offered

recently, in the metal can area.

In the United Kingdom the Wantage Research Center of

CarnaudMetalBox, plc (a ﬁrm now being purchased by

Crown Cork & Seal Co.) engineers have developed a process

by which a ﬁnished (plain or lithographed) three-piece

tinplate can is placed momentarily in a heavy steel mold

cell and expanded against the contoured sidewalls of the

cavity by pressurization with some 1200 psig (83 bars) of

ﬁltered dry air. The volume increase is limited to about 12–

18%, depending on relative can length. The emerging cans

(OD)

20°

1.375″  Ref

Figure 2. Necked-in aerosol can (tinplate).

End hook radius

End hook

Body hook

Seaming wall

Body hook radius

Seaming wall radius

Seaming panel

Seaming panel radius

Chuck wall

Body wall

Chuck wall radius

Figure 3. Anatomy of a double seam.

AEROSOL CONTAINERS 29

are necked-in and may have pleated, quilted, crestlike,

ergonomic ﬁnger depressions or other debossings in the

body wall. In general, these are never more than B0.15 in.

(3.8 mm) deep. Round-the-can lateral depressions must not

be too sharply deﬁned, or the can will increase in height

when pressure-tested during later can-making checks or in

ﬁller hot tanking. The fact that this is presently an extra

cost operation has thus far prevented marketer acceptance,

but one is mindful that such innovations as welded seams

and necked-in proﬁles were well-engineered decades before

marketers paid them much attention.

The trend toward aluminum cans has been quite notic-

able. During 2006, the production of these cans grew at

about 18%/year, which is much more than the more proseic

2–3% increase/year for the total aerosol market. This is

thought to relate to the greater aesthetics of aluminum,

more than anything else. Marketers who use tinplate cans

are responding by increasing the trend toward necked-in

types and by permanently covering at least the unsightly

valve cup, and ideally the entire can dome with a spray cap

or foam spout. In Europe and Japan, starch and fabric

ﬁnish products are offered with ‘‘pistol-grip handles’’ that

are integral with a full-diameter, nonremovable spray cap.

The accoutrement not only provides aesthetics but also

reduces hand and ﬁnger fatigue.

During 2006, the ﬁrm of DS Containers, Inc. began

production of two large sizes of 65-mm steel cans using the

‘‘Protact’’ process of double PET lamination developed by

Corus RD&T unit, Hoogevans Division of British Steel and

reﬁned by the Japanese can-maker, Daiwa Can Company.

The plate is delivered in huge rolls of chrome/chrome

oxide-coated steel, optimized for adhesion of PET and to

which the main layer of PET is attached with a special

adhesive, followed by a top layer for gloss, printability,

internal lubrication, and scratch resistance. These lami-

nates, the same for both sides of the steel plate, are about

80 times thicker that the typical 9 mm (0.0004-in.) thick-

ness of roller-coated or sprayed-on can linings, so they

offer outstanding protection for the metal substrate. A few

solvents, such as dimethyl ether (DME), are claimed to

soften PET plastics, and DS Containers state that the

hydroalcoholic hair sprays containing a much as 37% of

DME propellant can be packaged with no adverse effects.

DC Containers has produced containers for at least 50

domestic and international marketers to date. They plan

to install can-making equipment to produce various sizes

of the popular 52-mm-diameter aerosols during 2008.

With their nicely rounded tops and unobtrusive botton

double seams, these cans have an appearance almost

identical to that of the 66-mm aluminum aerosol cans.

There is no information of their ability to be shaped, but

this probably will not occur until a few years in the future.

Table 3 gives some general data on these cans.

Aerosol formulations weave their effects into the for-

tunes of the steel and aluminum can-makers. Because of

environmental considerations centering on the issue of

clean ambient air, along with the reduction of emissions

that directly or indirectly produce air pollutants, the U.S.

aerosol industry has been obliged to reformulate most of

their products toward those that have reduced amounts of

volatile organic compounds (VOCs). The state governments

of California and New York have been very active in

limiting the VOC content of aerosols and other products.

As a result, many hair sprays and other products now

incorporate signiﬁcant amounts of water; otherwise they

use new propellants, such as (non-VOC) HFC-152a (1,1-

diﬂuoroethane). Quite often, these new formulations favor

aluminum cans, from both a corrosion resistance and a

smaller package standpoint. In some other countries the

percentage of aluminum cans is in the area of 40–60% of the

total, and it is possible that the United States and Canada

may slowly approach this high ground, as time goes by.

BIBLIOGRAPHY

General References

M. A. Johnson, The Aerosol Handbook, 2nd edition, Wayne E.

Dorland Co., Mendham. NJ, 1982.

Table 3. DC Containers: Steel Aerosol Cans

. The sole U.S. supplier is DC Containers, Batavia, IL.

. They currently produce two sizes: 211 604 and 211 713. DC Containers will make 52-mm cans in 2008. All cans are ‘‘DOT-2Q.’’ List

prices are about $0.26 to $0.29. Cans are ‘‘two-piece,’’ with rounded domes and bottoms necked in double seams.

. Using Corus Research technology (from Europe, but perfected in Japan), all inside and outside surfaces of tin-free steel are laminated

with:



Chrome/chrome oxide (Cr/CrO

) optimized for PET.



Adhesive.



Main layer of PET. ‘‘Protact’’



Top layer of PET. ‘‘Protact’’

. The total thickness, on each side, is about 0.020 in. (0.5 mm). WACO testing shows 0-mA conductance—inside to outside. All cans are

automatically pressure-tested to 120 psig.

. The main PET layer can be colorized, but printing is done on an eight-color offset machine on the top layer, then baked. The top layer

also provides gloss and abrasion resistance.

. For comparison, the lining of tinplate and aluminum cans is typically 0.0004 in. (0.01 mm or 10 mm), or 2% as thick.

. WACO readings on aluminum cans are typically 2–20 mA, while those on lined tinplate cans are typically 300–800 mA.

. Pure dimethyl ether (DME) greatly softens PET, but solution of up to 38% DME (as in some 55% VOC hair sprays) are said to have no

effect.

30 AEROSOL CONTAINERS

The Aerosol Guide, 8th edition, Consumer Speciality Products

Assocaition, 1995; a 10th edition as a CD will publish in

2009.

Aerosol Europe, Seeshaupt, Germany, a monthly journal.

Spray Technology and Marketing, Parsippany, NJ, a monthly

journal.

AIR CONVEYING

TIMOTHY AIDLIN

Aidlin Automation,

Sarasota, Florida

The fast changes within both lightweight packaging and

plastics technology during the 1980s brought forth

the development of a new technology: the air conveyor.

Because of the backpressure created on chain conveyors,

the new lightweight packages and bottles were getting

crushed and marred—but with the advent of the air

conveyor, those problems were no longer of great concern.

The air conveyor is faster, easier, cleaner, and safer than

its predecessors, the belt, cable, and chain conveyors. For

these reasons, the air conveyor has quickly become the

conveying method of choice.

AIR CONVEYING

How does it work? All air conveyors share several basic

operating principles that are as follows:

. Use of air as the transport medium.

. Containers are moved using a high volume of low-

pressure air to transport the product along the

conveyor path.

The major differences among the leading air conveyor

manufacturers are the following:

. Where the air is directed against the product, con-

tainer, or bottle

. How the airﬂow is created (design of motors and fans

for maximum efﬁciency)

. Where the airﬂow is created: one large blower vs

multiple small blowers

. Construction details and ‘‘user-friendly’’ features of

the air conveyor

See Figures 1–3 for air conveying operations.

How does the air conveyor solve the problems

found with the chain conveyor, and why is it the

better method of conveying? It eliminates crushing.

The air conveyor moves the packages by a directed ﬂow of

air against the containers. The ﬂow of air can be controlled

throughout the air conveying system. In this way, crush-

ing of packages is eliminated as follows:

. By reducing the backpressure force against the ﬁrst

product in a long line of products in a backfeed

condition.

. By controlling the velocity of the product through the

use of manual or automatic bafﬂes, one can reduce

the impact force of a product arriving from upstream

and reduce damage.

. By introducing lift holes in combination with louvers,

the product can hover while using the conveyor for

accumulation on the ﬂat-top air conveyor—no mark-

ing of crushing is evident from the friction caused by

the belt or chain.

In beverage applications, the bottles cannot fall, which

is detailed as follows:

. The bottles cannot fall when the bottle is transported

hanging by the neck support ring.

. Eliminating bottles falling down on the conveyor and

getting caught in the starwheels or timing screws.

As a result, users of air conveyors derive the following

beneﬁts:

. Gapless ﬁlling. At the higher production speeds, even

small inefﬁciencies are costly and unacceptable. Air

conveyors will virtually eliminate the possibility of a

missed cap or container by assuring that a sufﬁcient

supply is provided to the infeed of the ﬁller, rinser,

capper, or packaging equipment. In the event of a

‘‘hiccup’’ of the upstream equipment, bottles, caps, or

other products from upstream will be conveyed

quickly, which allows the line to recover.

Figure 1. Airﬂow inside plenum.

AIR CONVEYING 31

. Shorter surge areas. Faster conveying speeds allows

for quicker recovery from the upstream supply of a

product to the rinsers, ﬁllers, cappers, or packaging

equipment. As a result, users of air conveyors will be

able to greatly reduce the lengths of a conveyor to

accommodate surges.

. Reduction in buffer areas (BIDI tables). For the same

reasons as described above, bidirectional accumulat-

ing tables can be eliminated. There still may be

the need for accumulation as, for example, where

the labelers need to be changed over. For beverage

applications we recommend side lengths of air con-

veyor where the bottles can be diverted for additional

accumulations as the most effective means of accu-

mulating and preventing bottles from falling over.

The net result of these advantages is less overall length

of conveyor in the plant. This length reduction also results

in both lower cost for the conveyor installation and freeing

up of valuable plant space at ﬂoor level.

CHARACTERISTICS OF A PROPERLY DESIGNED AIR

CONVEYOR

Construction Materials. We recommend and use stain-

less steel construction for the conveyor; this material will

Figure 2. Plenum, cutaway view.

Figure 3. Single-lane air conveyor, adjustable bottle guide.

32 AIR CONVEYING

result in lowered maintenance costs and in easier wash-

down. Most importantly, the use of stainless steel guide-

rails on neckring a air conveyor avoids the need to replace

guiderail wear strips.

Airﬂow. In cap conveying applications on ﬂat-top air

conveyors, center louvers are the most efﬁcient. On heavier

parts, the addition of lift holes combined with louvers aids

the product ﬂow, especially where accumulation is required.

The three methods used most commonly are neck blow,

shoulder blow, and sidewall blow in neckring air conveyor

applications. In these applications , we feel that neck blow is

the preferred method, because most bottles have the same

neck dimensions as compared with body diameter dimen-

sions. Using the neck dimension as the criterion, adjust-

ment for different sized containers is reduced.

Flat-Top Air Conveyor Applications. The food industry

found a solution in a ﬂat-top air conveyor and, in turn, is

a major user of it. Because of the ﬂat-top air conveyor’s

ability to convey with virtually no damage to the product,

the manufacturers of candy, for instance, turned

away from conventional tabletop conveyors and turned

toward air conveyors. Because of the ﬂat-top air con-

veyor’s ability to lift as well as convey, the air conveyor

can be used to accumulate products, eliminating the

damage caused by friction from a belt or chain. These

features make the air conveyor the product transportation

vehicle of choice.

The beverage industry has changed signiﬁcantly with

the growth of the 16- and 20-oz bottles. Use of 28- and 38-

mm plastic beverage caps has grown as well. The beverage

industry was now looking for a versatile method of con-

veying them while maintaining orientation to the capper.

Their solution was to use an air conveyor coupled with a

cap feeder/orientor. In general, the bottlers were now able

to convey their caps quickly, efﬁciently, and 100% oriented

to their cappers at speeds to 1800 Hz from remote loca-

tions, such as warehouses and production facilities.

BEVERAGE INDUSTRY APPLICATIONS

Faster Filling Speeds. Filling line speeds have and will

continue to increase. Our company is now involved with

projects where the required line speeds are as follows:

. 2-L container: 800/min

. 20-oz bottle: 1100/min

. 16-oz bottle: 1200/min

Our company’s Airtrans Air Conveyor installations

have been to provide better control of the containers out

of the depalletizers that are running at higher speeds.

One-Piece and Single-Serving Bottles. Because of their

higher center of gravity and thin-walled, lighter design,

most one-piece bottles are inherently less stable than the

base-cupped bottle. Also, in recent years, an increase has

occurred in market share for the 16-oz and now the newly

introduced 20-oz PET bottles. These containers are less

stable on ﬁlling lines than the 2-L bottle, and they fall over

more easily than the glass bottles they replaced. The

higher ﬁlling line speeds of the smaller bottles (up to

800 bottles per minute) continually aggravate the problem

of the bottles falling over and jamming on the conveyors.

The neckring air conveyor virtually eliminates these

problems by conveying quickly, cleanly, and with little to

no jamming or tipping. Because the bottles are suspended

by the neckring, the possibility of tipping is eliminated.

Also, because the bottles are conveyed with air, there is

much less back pressure exerted on the new, thin-walled

bottles, signiﬁcantly reducing damage. (see also Carbo-

nated beverage packaging)

Marketability. A major trend has been the expansion of

blow-molding plant outputs, in terms of both total output

and numbers of packaging lines. This growth 6L in output

has resulted in an increased need to eliminate cable or

chain conveyors and in an increased implementation of air

conveyors. Bottlers are splitting the output of their blow

molding machined into several streams to downstream

packaging equipment and combining the output of multi-

ple blow molders into their packaging equipment. How-

ever, as shown in the applications of ﬂat-top air conveyors,

the applications of air conveying are not limited to blow

molding applications by any means.

Problems of Conventional Tabletop Conveyors Needing

Solution. The following problems of cable and chain con-

veyors are commonly known by the industry:

. Greater nonproductive costs of mechanical conveyors

because of higher maintenance of high-speed chain

conveyors—mechanical conveyors have moving parts

that are subject to wear and mechanical failure.

. The following spare parts are required:

. Chain

. Wear strips

. Gears

. Sprockets

. Bearings

Expense for disposable lubricants and wear parts

. Unsanitary—grease

and constant soap

on bottles

and product

. Higher unplanned downtime of tabletop conveyors—

these mechanical components will fail unexpectedly

. Greater crushing of lightweight plastic bottles and

delicate packages

. Bottles fall over

. Bottles jam on tabletop conveyors

BENEFITS OF AIR CONVEYORS AND ELIMINATION OF

POPULAR MYTHS

Expense. An air conveyor system can actually be more

cost-effective than chain, belt, or cable conveyor for

the same application. Although initial costs of an air

AIR CONVEYING 33

conveying system may be more, the reduced maintenance,

amount of spare parts, and downtime make air conveying

an overall less expensive method of transport. Basic

capital expenditures of the conveyor are only part of the

complete cost picture. The true and total cost of the

conveying system also includes the following:

. Spare parts. The air conveyor needs and uses less.

Few moving parts exist on an air conveyor so the

initial capital for spare parts and yearly additional

parts’ costs are less than for mechanical conveyors.

. Maintenance labor costs are less than for mechanical

conveyors. Because few moving parts are present, it

is less likely to break down and need repair break-

down and need of repair.

. Air conveyors can be more readily located overhead.

These savings in ﬂoorspace costs may be applied as

cost saving.

Flexibility. Air conveyors offer signiﬁcantly more ﬂex-

ibility than chain conveyors for the following:

. Revisions to ﬂoorplan. Both ﬂat-top and neckring air

conveyor systems are furnished in sections that bolt

to each other in a continuous path. The modules

typically are combinations of straight sections, hor-

izontal curves, vertical curves, and gates for merging

and diverging. Any of these modules can be reconﬁ-

gured in a different combination and can be added

or deleted. Our company reconﬁgured a system that

had been shipped four years previously, and by

adding additional sections to the original system as

well as by adding other new sections, we provided a

totally different conveyor system layout. Few of the

old sections were wasted; rather they were reused

elsewhere in the new conveyor line. The entire

system was reconﬁgured with less than one week of

installation and dismantling.

. Multiple sizes of containers. The ﬂat-top air conveyor

can generally carry 5 lb/ft

. Also, our ﬂat-top air

conveyor can be designed to accommodate many

differently sized products. Whether it be through a

dual-lane, multi-lane, or single-lane ﬂat-top air con-

veyor, from unwrapped candy to boxes to caps, a

virtually endless variety of products can be trans-

ported using this system.

. Multiple sizes of beverage containers. Multiple sizes

of containers are accommodated using several differ-

ent techniques. Different heights of containers are

accommodated by adjusting the height of the air

conveyor through hand wheel adjustment or auto-

matically. The air conveyor transports bottles hang-

ing by the neck support ring. The Aidlin Airtrans has

hinged end sections on the infeed and discharge ends

of the air conveyor. Similarly, the height would be

adjusted when discharging bottles to the infeed

screw of the ﬁller. Infeed and exit plenums are

hinged to allow adjustment of bottle height in the

air conveyor. Also, bottle heights from the same

supplier can have height variations for which the

conveyor may need to be adjusted. Fixed height

neck rails obviously do not have the necessary ad-

justability for this condition. Different neck dia-

meters are accommodated by Aidlin’s Dual-Lane

Airtrans. The Dual-Lane Neck Ring Air Conveyors

is a double-lane neck rail. One lane is set up for 16-oz

bottles, whereas the other is set for 2-L containers;

similarly, one lane could be set for 28-mm neck

ﬁnishes and the other lane set up for 38-mm neck

ﬁnishes (as on 3-L containers). A single air plenum is

switched over to supply either set of neck rails as

required.

Interfacing with Other Equipment. One signiﬁcant ad-

vantage of both ﬂat-top and neckring air conveyors is their

ability to interface easily with other packaging equipment

(see also, Blow holding; Labels and labeling machinery;

Palletizing).

Mechanical interfacing.

. The ﬂat-top air conveyor can transport from and to

most equipment: from the orienting orientors to the

cappers, liners, or decorators; or to a wrapper, car-

toner, or case packer. When needed, the air conveyor

can be ﬁt to virtually any line. The transport process

is described as follows:

. Blow molders. Bottles are received either through a

bottle collector conveyor (as on the Cincinnati, Mag-

plas, and Nissei) or directly from the output neck

rails (as on the Sidel and Krupp).

. Palletizers. An escapement is mounted to the dis-

charge of the air conveyor to stabilize the bottle and

match the container’s speed to be the same as the

infeed conveyor to the palletizer.

. Depalletizers. Containers are received off the outfeed

conveyor directly to the split neck rails of the air

conveyor. The bottles are accelerated and conveyed

away from the palletizer at a faster line rate than the

depalletization. In this way, no possibility exists of

bottles falling down.

. Labelers. Containers can be placed directly into the

infeed starwheel or timing screw of the labeler.

. Fillers. Bottles are placed directly into the infeed

timing screw of the ﬁller. By assuring a proper

backpressure and constant supply of bottles, max-

imum ﬁlling speed is achieved.

Maintenance. The total maintenance factor of the air

conveyor is signiﬁcantly less than that for mechanical

conveyors. For example, the normal maintenance in the

Airtrans system consists of replacing, in less than one

minute, the 5-mm fan ﬁlters as needed. In our ﬂat-top air

conveyor, both the top guiderail and the Lexan covers are

hinged for easy cleaning.

Less Contamination to Products. Based on R&D done at

Aidlin Automation in Bradenton, FL, the air transporting

34 AIR CONVEYING

the bottles or products is ﬁltered, in our case, to 5 mm.

The net result is that bottles or products, such as food

or caps, remain cleaner than in the typical plant where

the neck, cap, or product is open to unﬁltered ambient

air.

Conclusion. As one clearly can see, air conveying pro-

vides the alternative to chain, cable, or belt conveyors. Air

conveying provides clean, consistent, and predictable per-

formance. The new generation of conveying technology is

here and in great demand. To be proﬁtable in this quickly

changing industry, one must keep up to date with new

technology—and that is the air conveyor.

AMPULS AND VIALS, GLASS

Ampuls and aluminum-seal vials are glass containers

used primarily for packaging medication intended for

injection. Ampuls are essentially single-dosage containers

that are ﬁlled and hermetically sealed by ﬂame-sealing

the open end. Vials, which contain single or multiple

doses, are hermetically sealed by means of a rubber

closure held in place with a crimped aluminum ring.

An ampul is opened by breaking it at its smallest

diameter, called the constriction. A controlled breaking

characteristic is introduced by reproducibly scoring the

glass in the constriction, or by placing a band of ceramic

paint in the constriction. The ceramic paint has a thermal

expansion that differs from the glass, thus, forming stress

in the glass surface after being ﬁred. This stress allows the

glass to break in a controlled fashion at the band location

when force is applied. Medication is then withdrawn by

means of a syringe.

Medication can be withdrawn from a vial by inserting

the cannula of a syringe through the rubber closure.

Because the rubber reseals after cannula withdrawal,

multiple doses can be withdrawn from a vial.

Both ampuls and vials are fabricated from glass tubing

produced under exacting conditions. The glass used for

these containers must protect the contained product from

contamination before use and, in the case of light-sensitive

products, from degradation caused by excessive exposure

to light. In addition, the glass must not introduce con-

tamination by interacting with the product.

GLASSES

The most important property of a glass used to contain a

parenteral (injectable) drug is chemical durability; that is,

the glass must be essentially inert with respect to the

product, and contribute negligible amounts of its consti-

tuents to the product through long-term contact before

use. The family of glasses that best meets chemical dur-

ability requirements is the borosilicates. These glasses

also require higher temperatures for forming into shapes

than other glass types.

When glass-product interactions are far less critical,

the soda-lime family of glasses can be used to fabricate

vials. These glasses can be formed at lower temperatures

than borosilicates but do not nearly have their chemical

durability. Typical compositions are shown in Table 1.

Borosilicate and soda-lime glasses contain elements that

facilitate reﬁning, but borosilicates generally do not con-

tain arsenic or antimony.

Both borosilicate and soda-lime glasses can be given a

dark amber color by adding small amounts of coloring

agents, which include iron, titanium, and manganese. The

amber borosilicate and soda-lime glasses then can be used

to package products that are light-sensitive.

The interior surface of containers formed from soda-

lime glass is often subjected to a treatment that enhances

chemical durability without affecting the desirable lower

melting and forming temperatures typical of soda-lime

glass. For very critical applications, borosilicate ampuls

and vials can be treated to improve their already excellent

chemical durability.

For pharmaceutical packaging applications (see Phar-

maceutical packaging), the various types of glass have

been codiﬁed into groups according to their chemical

durabilities, as speciﬁed by the United States Pharmaco-

peia (USP) (1). The glasses are classiﬁed by the amount of

titratable alkali extracted into water from a crushed and

sized glass sample during steam autoclaving at 2501F

(121 1C). Thus, borosilicate glasses are typical of a USP

Type I glass, and most soda-lime glasses are typical of a

USP Type III glass. Some soda-lime glasses exist that are

less chemically durable than Type III glass, and these

glasses are classiﬁed as USP Type NP.

USP Type III (soda-lime) containers that have had

their interior surface treated to improve durability can

be classiﬁed as USP Type II if they meet the test require-

ments. The test in these cases is performed on the treated

container instead of a crushed sample and uses a similar

steam autoclave cycle.

The pharmacopeiae of other nations also have classiﬁed

glass into groups according to their chemical durability.

Table 1. Compositions of Soda-Lime and Borosilicate

Glasses, wt%

Constituent Soda-lime Borosilicate

SiO

68–72 70–80

0–2 10–13

2–3 2–7

CaO 5 0–1

MgO 4

O 15–16 4–6

O 1 0–3

Typical forming temperatures 1796–18951F 2066–22641F

(980–1035 1C) (1130–1240 1C)

AMPULS AND VIALS, GLASS 35

These classiﬁcations are generally similar to those speci-

ﬁed by USP.

FORMING PROCESSES

Ampuls and vials are formed from glass tubing. The glass

tubing is formed by processing in a glass furnace and by a

tube-forming operation. The glass furnace operation con-

sists of bulk batch preparation, continuous batch melting,

and reﬁning (see Glass-container manufacturing). The

tube forming is done to exact speciﬁcations in either a

Danner process or a downdraw process. The Danner

process involves continuous streaming of molten glass

onto an angled rotating sleeve that has an internal port

for inﬂation air. The inﬂation air controls the tubing

outside diameter (OD). The downdraw process is an

extrusion process through an annular area. The inner

core has an inﬂation air hole. The inﬂation air serves the

same purpose as in the Danner process. In either process

the tubing wall weight is controlled by adjusting the rate

of glass withdrawal and supply. Typical ampul and vial

tubing dimensions and tolerances are shown in Figures 1

and 2.

The tubing is formed in a continuous-line process.

Various devices are used to support the tubing during

pulling. A device, normally consisting of pulling wheels on

belts and a cutting mechanism, is situated downstream to

pull and cut the tubing. The tubing is cut to prescribed

lengths and used in vertical- or horizontal-type machines

for converting the tubing into vials or ampuls.

Many machines are rotary and either index or operate

with a continuous action. The tubing is placed in the

machines and is handled in a set of chucks. Heat is applied

in the space between the chucks, and forming of the ampul

or vial occurs throughout the machine rotation cycle.

Ampuls are formed on continuous-motion rotary ma-

chines. One sequence is shown in Figure 3. The process

consists of sequentially heating and pulling (elongating

the glass) to form the constriction, bulb, and stem contours

of the ampul. The ampul contours are controlled primarily

by proper temperature patterns in the tubing and by

pulling rate of the tubing. Mechanical tooling of the glass

can be used to assist in constriction contour forming.

The forming process accurately controls the seal plane

diameter, which controls ampul closing after ﬁlling. After

the basic ampul is formed on the machine, the ampul

blank is separated from the tubing and is transferred to a

horizontal afterforming machine. On the afterforming

machine the ampul is trimmed to length, glazed,

and treated if necessary. Also, the ampul constriction

can be either color banded with a ceramic-base paint or

scored to control opening properties. The ceramic paint

and scoring cause stress concentrations in the constric-

tion, which assist in obtaining desirable opening force and

fracture characteristics. Identiﬁcation bands are applied

Figure 1. Standard long-stem ampul.

Figure 2. Standard tubular serum vial.

Capacity,

Diameter (D)

Width (W),

Length (L1),

mm ± 0.50 mm

Length (L2),

1 10.40–10.70 0.56– 0.64 67 51

2 11.62–12.00 0.56– 0.64 75 59

5 16.10–16.70 0.61–0.69 88 73

10 18.75–19.40 0.66– 0.74 107 91

20 22.25–22.95 0.75– 0.85 135 120

Capacity,

Diameter (D1),

Width (W),

Length (L),

mm ± 0.50 mm

Diameter (D2),

1 13.50–14.00 0.94–1.06 27 12.95–13.35

2 14.50–15.00 0.94–1.06 32 12.95–13.35

3 16.50–17.00 1.04–1.16 37 12.95–13.35

5 20.50–21.00 1.04–1.16 38 12.95–13.35

10 23.50–24.00 1.13 –1.27 50 19.70 –20.20

15 26.25–27.00 1.13 –1.27 57 19.70 –20.20

36 AMPULS AND VIALS, GLASS

and the ampul is annealed to relieve the strains caused by

the thermal forming of the ampul. The completed ampuls

are then transferred into a packing area where the ampuls

are accumulated, inspected manually or automatically,

and packed into clean trays for distribution (see Figure 4).

Vial forming is done on vertical machines that either

index or have a continuous motion. A vertical forming

sequence (see Figure 5) consists of a parting (separation

operation), wherein a narrow band of glass is heated to a

soft condition and the vial blank and the tubing are pulled

apart. After parting, the ﬁnish-forming operations occur.

The ﬁnish forming consists of heating and mechanically

tooling the glass in sequential steps. Normally, multiple

heating and tooling operations are necessary to form the

closely held tolerances of aluminum-seal ﬁnishes. The

tooling is done with an inner plug to control the contour

and diameter of the ﬁnish bore and with outer contoured

round dies that control the contour and diameter of the

ﬁnish outer surface. The vial bottom contours are formed

in the lower chucks whereas ﬁnish forming occurs for

another vial in the upper chucks. After tooling, the vial

length is set by a mechanical positioner. The process then

continually repeats itself until the whole tubing length is

consumed. After fabrication, the vial blank is transferred

to a horizontal afterforming machine. The operations that

are normally performed on an afterformer are dimen-

sional gauging, vial treatment, and annealing. The vials

are then transferred to a packing area where they are

accumulated, inspected manually or automatically for

cosmetic conditions, and packed in clean containers (see

Figure 6).

Figure 3. Ampul contour-forming sequence.

Figure 4. Tube converting for ampul manufacture.

AMPULS AND VIALS, GLASS 37