Metal Can Defects Manual - Identification and Classification
Chapter 7 - Defect categories

7.1 Metal Plate Manufacturing Defects

(PDF (660 kb))

7.1.1 DEFECT: LAMINATED PLATE

CLASSIFICATION:

A plate lamination is considered a serious metal plate defect.

DESCRIPTION:

Metal body or end plate which can be separated into two layers of metal which are not bonded.

COMMON SOURCES:

  1. Folds or layers of plate rolled into a single plate thickness in the rolling mill. These folds or layers do not bond together during rolling and will separate when the metal is worked during can manufacture.

 Laminated Plate - photo 1

Laminated Plate - photo 2Laminated Plate - photo 3

Laminated Plate - photo 4Laminated Plate - photo 5

7.1.2 DEFECT: PIN-HOLE

CLASSIFICATION:

A pin-hole is considered as a serious metal plate defect.

DESCRIPTION:

A hole in the metal plate originating in the rolling mill. These will vary in size from barely visible to large irregular shaped holes with rough edges.

COMMON SOURCES:

  1. Foreign particles may be rolled into the plate during the rolling operation in the mill; they do not bond with the plate. Large particles will extend to both surfaces of the plate. When the plate is worked during can manufacture or flexed during retorting, these particles may pop out leaving a hole (pin-hole) in the plate.

 Pin-hole - photo 1

Pin-hole - photo 2

Pin-hole - photo 3

Pin-hole - photo 4

7.1.3 DEFECT: PLATE STAIN

CLASSIFICATION:

Plate stain is considered as a minor metal plate defect.

DESCRIPTION:

Readily visible stains on the metal plate surface. If the metal plate is coated, these stains may be visible through the coating.

COMMON SOURCES:

  1. This condition originates during plate fabrication.

Photo not available.

7.1.4 DEFECT: WELD JOINT

CLASSIFICATION:

A weld joint is considered a serious metal plate defect when packed with a corrosive product, when there are gaps in the continuous weld such as in spot welds or when the weld is weakened to the point that it fails under finger pressure.

DESCRIPTION:

An obvious, black line (joint) approximately 5 mm (3/16") wide running across the can end or body. They seldom result in leakage although there is potential for corrosion along this weld which may lead to perforation.

COMMON SOURCES:

  1. These joints are made in the steel mill when two coils of plate are joined (arc welded) together.

Weld Joint - photo 1

Weld Joint - photo 2

7.2 Coating Application Defects

(PDF (965 kb))

7.2.1 DEFECT: COATER DRIP

CLASSIFICATION:

A coater drip is considered a minor defect unless careful examination proves that the defect is a serious defect. A coater drip is considered a serious coating application defect if a hole and/or plate corrosion is detected, after a thorough examination, which would include opening the can or removal of the coater drip to determine the condition of the metal plate.

DESCRIPTION:

A drop of coating, exterior or interior, often appearing as tiny hard metallic bubbles of coating. A coating drip may resemble a scrap-in-die type defect.

COMMON SOURCES:

  1. Drips or splashes from the coating operation.

Coater Drip - photo 1

Coater Drip - photo 2

Coater Drip - photo 3
Coater Drip - photo 4

A     Inside View of A

Coater Drip - photo 5
Coater Drip - photo 6

7.2.2 DEFECT: COATING SKIPS

CLASSIFICATION:

Coating skips are considered serious coating application defects if:

  1. internal and contents are corrosive; or
  2. external and plate is corroded.

Coating skips are considered minor coating application defects if:

  1. external and no corrosion; or
  2. internal and contents are non-corrosive.

DESCRIPTION:

Any discontinuity (bare spots, hairline skips, eyeholing) in the coating. Corrosion or sulphide production (reaction with product) may be present. See also section 7.7.3 - CORROSION

COMMON SOURCES:

  1. Dirt, grease or other foreign material on the metal plate prior to coating.
  2. Misapplication of the coating to the metal plate.

Coating Skip - photo 1

Coating Skip - photo 2

Coating Skip - photo 3

Coating Skip - photo 4

Coating Skip - photo 5

7.2.3 DEFECT: FOREIGN PARTICLES IN COATING

CLASSIFICATION:

A minor coating application defect.

DESCRIPTION:

Small particles in the coating surface, often black in colour. Coating ash may appear as a line on the body wall of two piece cans as the result of the drawing operation.

COMMON SOURCES:

  1. Coating ash or charred particles of coating, dirt or other foreign particles that may adhere to the wet coating before it is baked.
Foreign Particles in Coating - photo 1
INSIDE VIEW
Foreign Particles in Coating - photo 2
OUTSIDE VIEW

7.3 Can Body Manufacturing Defects

(PDF (3,140 kb))

THREE PIECE SOLDERED

7.3.1 DEFECT:  ACID SALTS CORROSION

CLASSIFICATION:

Acid salts corrosion is considered a serious three piece can defect.

DESCRIPTION:

Acidic residues on the outside of the side seam area that result in rusting, or any deposit of salts on the inside of the can.

COMMON SOURCES:

'
  1. Acidic residues on the side seam solder, picked up from the solder bath when it is charged with "acid crystals" used to keep the solder roll clean and "tinned".

Acid Salts Corrosion - photo 1Acid Salts Corrosion - photo 2

7.3.2 DEFECT:  COLD SOLDER

CLASSIFICATION:

Cold solder is considered a serious three piece can defect.

DESCRIPTION:

A discontinuity (gaps or voids) or a rough and spongy irregularity of the side seam solder fillet which could result in a pathway through the side seam. The cold solder condition will most easily occur in the lap area at the extremities of the side seam, but cannot be properly checked unless the side seam and double seam are torn down for examination.

COMMON SOURCES:

  1. Solder temperatures too cold.

Cold Solder - photo 1Cold Solder - photo 2

7.3.3 DEFECT:  DISTORTED REFORM RIDGE

CLASSIFICATION:

A distorted reform ridge is considered a serious three piece can defect.

DESCRIPTION:

Creasing of the body and flange area on the reform ridge of reformed cans such that it affects the integrity of the double seam or fractures the metal plate.

COMMON SOURCE:

  1. Improper flattening of can body cylinders.
  2. Improper reforming of flattened can body cylinders.

Distorted Reform Ridge

7.3.4 DEFECT:  EXCESSIVE SOLDER

CLASSIFICATION:

Excessive solder is considered a serious three piece can defect, if:

  1. a solder ridge 1/2 the can height in length by 0.4 mm (1/64") in thickness on the outside is found; or
  2. the excess solder interferes with the forming of the double seam.

DESCRIPTION:

Excessive solder at the customer lap area of the side seam which may cause deformation of the double seam at the crossover, resulting in excessive side seam droop, a raised seam, or a jumped seam. Excessive solder may also cause a pleat to form in the side seam lap. A thick lap is a condition where the side seam contains excess solder between the laps.

COMMON SOURCES:

  1. Improper wiping of the solder.

Excessive Solder photo 1Excessive Solder photo 2

7.3.5 DEFECT:  FLUX STAINS

CLASSIFICATION:

Flux stains are considered as minor three piece can defects.

DESCRIPTION:

Dark brown resinous staining on the inside surface of the side seam or lap. The fluxes used for the manufacture of food cans in Canada are non-toxic and will not impart off-odors or off-flavours to the product.

COMMON SOURCES:

  1. Excessive flux during the side seam soldering operation.

Flux Stains - photo 1Flux Stains - photo 2

7.3.6 DEFECT:  INSUFFICIENT SOLDER

CLASSIFICATION:

Insufficient solder is considered a serious three piece can defect if the solder fillet is incomplete along the outside of the side seam and is accompanied by a defective sweat.

DESCRIPTION:

Solder voids in the outside side seam fillet resulting in incomplete soldering of the side seam. The fillet is the strip of solder deposited along the intersection of the two walls of folded metal plate of the side seam. A TURNED CAN, depending on the degree of turning, results in a solder void or an incomplete fillet along the outside of the side seam.

A sweat is the action of bonding together, by application of heat, of surfaces to which solder has already been applied. A defective sweat is the result of improper solder temperature or incorrect flux application.

COMMON SOURCES:

  1. Contamination of the side seam area such that solder bonding is prevented.
  2. Improper or insufficient flux application.
  3. Turning of the can body prior to solder application.
  4. Excessive wiping of the solder.
  5. Solder temperature too hot.
Insufficient Solder - photo 1
CONTAMINATION
Insufficient Solder - photo 2
EXCESSIVE WIPING

7.3.7 DEFECT:  INVERTED INSIDE COATING

CLASSIFICATION:

The inverted inside coating is considered a serious three piece can defect for a soldered can. On a welded can it is considered a minor defect unless there is product/container incompatibility.

DESCRIPTION:

The inside coating margin pattern is visible. Plain rectangular areas show at each end of the side seam. These plain areas are normally concealed in the side seam. Soldering will be incomplete due to coated areas in the side seam fold.

COMMON SOURCES:

  1. Misfeed (backward feed) of sheets to slitter (machine which cuts sheets into body blanks).
  2. Misfeed (backward feed) of body blanks to body maker.

Inverted Inside Coating

7.3.8 DEFECT:  MIS-LOCKED SIDE SEAM

CLASSIFICATION:

A mis-locked side seam is considered a serious three piece can defect.

DESCRIPTION:

Failure of the side seam hooks to interlock along their entire length. Complete soldering of the side seam is not always possible. The side seam most probably will not leak.

COMMON SOURCES:

  1. Misassembly of the side seam hooks.
  2. Side seam hooks damaged prior to assembly.
  3. Improperly formed side seam hooks.

Mis-locked Side Seam - photo 1Mis-locked Side Seam - photo 2

7.3.9 DEFECT:  MIS-NOTCH

CLASSIFICATION:

A mis-notch is considered a serious three piece can defect when a 0.8 mm (1/32") gap extends into the depth of the flange.

DESCRIPTION:

A gap in the side seam lap area where the notched or cut away section is not overlapped by metal plate resulting in an incomplete flange.

COMMON SOURCES:

  1. Misalignment during notching of the body blank.

Mis-notch

7.3.10 DEFECT:  NECKED-IN-CAN

CLASSIFICATION:

A necked-in can is considered a serious three piece can defect. This classification only applies to those cans which were not designed to be necked-in.

DESCRIPTION:

A can body which has an end diameter that is unintentionally smaller than the main body cylinder diameter. Either one or both ends of the body cylinder may be necked-in.

Necked-in cans are now commonplace in the beverage industry and the technology may appear in other food containers. Necked-in cans are intentionally necked-in to strengthen the can body. The can ends for such cans are intentionally smaller in diameter.

COMM0N SOURCES:

  1. Misassembly of the body blank edges during formation of the side seam.

Necked-in Can

7.3.11 DEFECT:  NOTCHER TRIM STILL ATTACHED

CLASSIFICATION:

Notcher trim still attached is considered a serious three piece can defect due to additional metal formed into the double seam.

DESCRIPTION:

Extraneous metal at the side seam lap area having the shape of the section of body blank that is normally cut away prior to the formation of the side seam hooks.

COMMON SOURCES:

  1. Notching die failed to make a clean cut.

Notcher Trim Still Attached - graphic 1

 

Notcher Trim Still Attached - photo 1

7.3.12 DEFECT:  OFF-REGISTER BODY BLANK COATING

CLASSIFICATION:

An off register body blank coating is considered a serious three piece can defect when complete soldering of the side seam is not possible.

DESCRIPTION:

An off register or misplacement of the inside and/or outside coating. This may result in coating of the margin(s) along the body blank edges which will form the side seam. This misplaced coating prevents soldering. The side seam margin will appear elsewhere on the can body giving the can a turned appearance.

COMMON SOURCES:

  1. Off register coating application.
  2. Off register slitting of sheets into body blanks.

Off-Register Body Blank Coating - photo 1Off-Register Body Blank Coating - photo 2

7.3.13 DEFECT:  OPEN OR WEAK LAP

CLASSIFICATION:

Open or weak lap is considered a serious three piece can defect if the solder bond at the lap is broken either before or after flexing the lap inward 2.4 mm (3/32").

DESCRIPTION:

A condition where light finger pressure on an empty can will cause the bonded (soldered) lap joint to open. When empty cans with weak laps or open laps are seamed, the lap joint solder frequently fractures resulting in an open lap and leakage. Such an open lap is sometimes difficult to observe, and cans with this defect appear "normal" except for gross liquid loss.

COMMON SOURCES:

  1. Solder temperatures too hot or too cold.
  2. Improper or insufficient flux during soldering.
  3. Laps insufficiently tightened (see section 3.3.1).

Open or Weak Lap - photo 1Open or Weak Lap - photo 2

7.3.14 DEFECT:  OUT OF SQUARE BODY

CLASSIFICATION:

An out-of-square body is considered a serious three piece can defect.

DESCRIPTION:

A can body with a step in the flange of the lap area due to the lap members being misaligned by 0.79 mm (1/32") or more. Also called "high ends".

COMMON SOURCES:

  1. Misalignment of the body blank edges during formation of the side seam.
  2. Out-of-square body blank.

Out-of-Square body - photo 1  

Out-of-Square body - photo 2

7.3.15 DEFECT:  SOLDER PELLETS

CLASSIFICATION:

The occurrence of extraneous, loose or easily dislodged solder pellets, flakes, or strings of solder are considered serious as a product contaminant. The presence of solder pellets will seldom compromise can integrity, unless they are in the double seam (see SEAM INCLUSIONS 7.5.19).

DESCRIPTION:

The presence of solder droplets or pellets adhering to the inside surface adjacent to the side seam of the open-top can. Solder pellets are considered foreign material in the can.

COMMON SOURCES:

  1. Solder splash during the side seam soldering operation.

Solder Pellets

7.3.16 DEFECT:  TURNED BACK LAP

CLASSIFICATION:

A turned back lap is considered a serious three piece can defect.

DESCRIPTION:

A condition where one of the overlapping edges (laps) of the can body has been turned back during formation of the side seam. Such a defect will most probably result in an open (leaking) side seam.

COMMON SOURCES:

  1. Damaged slit notch (a step in forming the lap).

Turned Back Lap - photo 1  Turned Back Lap - photo 2

THREE PIECE WELDED

7.3.17 DEFECT:  BURNED WELD

CLASSIFICATION:

A burned through weld is considered a serious weld defect.

DESCRIPTION:

Excessive local heat due to the presence of foreign materials. This results in a burned through condition.

COMMON SOURCES:

  1. Foreign material in weld, for example, inside or outside coating, dirt, oil or grease.
  2. Contaminated weld wire.

Burned Weld - photo 1 Burned Weld - photo 2

7.3.18 DEFECT:  OPEN WELD

CLASSIFICATION:

An open weld is considered a serious weld defect.

DESCRIPTION:

An incomplete or parted side seam weld bond.

COMMON SOURCES:

  1. Incorrect side seam overlap.
  2. Insufficient current.
  3. Damaged or defective body blank.
  4. Tapered side seam overlap.
  5. Cold or weak weld.

Open Weld - photo 1Open Weld - photo 2

7.3.19 DEFECT:  TURNED CORNER

CLASSIFICATION:

A turned back corner is considered a serious weld defect.

DESCRIPTION:

A triangular hole at either end of the side seam.

COMMON SOURCES:

  1. Corner of body blank turned back prior to welding.
  2. Unwelded or weakly welded area of side seam turned back during flanging and/or double seaming operation.

Turned-back corner - photo 1Turned-back corner - photo 2

OPEN TOP - CAN INTERIOR

Turned-back corner - photo 3

Turned Back Corner - photo 4

CAN EXTERIOR

Turned Back Corner - photo 5Turned Back Corner - photo 6

Turned Back Corner - photo 7

TWO PIECE INTEGRAL END

7.3.20 DEFECT:  FLANGE BURRS

CLASSIFICATION:

Flange burrs are considered as serious can manufacturing defects if the burr protrudes greater than or equal to 0.50 mm (0.020"). Flange burrs are considered minor can manufacturing defects, if the burr protrudes between 0.50 mm and 0.25 mm (0.020" and 0.010").

DESCRIPTION:

A rough protrusion of metal plate (a burr) on the cut edge of the flange.

COMMON SOURCES:

  1. The flange trim press does not cleanly shear the flange to the desired length.

Flange Burrs

7.3.21 DEFECT:  FLUTED BODY

CLASSIFICATION:

A fluted body defect is generally considered a minor defect. If the flutes extend into the flange area it is considered a serious defect, when the degree of wrinkling is sufficiently pronounced so as to interfere with the formation of double seams, compromising its integrity.

DESCRIPTION:

One or more deep wrinkles on the tapered body.

COMMON SOURCES:

  1. Can body moves during the drawing operation.

Fluted Body

7.3.22 DEFECT:  FRACTURED BOTTOM PROFILE

CLASSIFICATION:

Fractured bottom profile is considered a serious two piece can defect if:

  1. there is a complete fracture of the countersink radius; or
  2. the metal stress on the countersink radius weakens or scores the metal at the radius and a fracture is imminent.

DESCRIPTION:

A fractured bottom profile radius of a two piece style can or a pinched bottom profile radius which may fracture during processing or handling.

COMMON SOURCES:

  1. Inadequate lubrication of the plate prior to drawing.
  2. Misaligned punch and die.

Fractured Bottom Profile      Fractured Bottom Profile     Fractured Bottom Profile

7.3.23 DEFECT:  INCOMPLETE BOTTOM PROFILE

CLASSIFICATION:

An incomplete bottom profile is considered a minor two piece can defect provided that the can does not buckle during retorting.

DESCRIPTION:

The integral end profile is not completely formed. This end is then weaker and may buckle during retorting.

COMMON SOURCES:

  1. The punch does not complete its stroke into the die.

Incomplete Bottom Profile - photo 1

Incomplete Bottom Profile - photo 2

7.3.24 DEFECT:  MALFORMED ABUSE BEAD

CLASSIFICATION:

A malformed or incomplete abuse bead is considered a serious can manufacturing defect if the metal plate is deeply abraded or creased.

DESCRIPTION:

The abuse bead on the two piece body is misaligned or incomplete. The metal plate may be abraded, creased or dented to varying degrees.

COMMON SOURCES:

  1. The can slips during the beading operation resulting in an incomplete abuse bead.
  2. The can misfeeds at the entrance to the beading machine.

Malformed or Incomplete Abuse Bead - photo 1

Malformed or Incomplete Abuse Bead - photo 2

Malformed or Incomplete Abuse Bead - photo 3

7.3.25 DEFECT:  SCRAP-IN-DIE MARKS

CLASSIFICATION:

Scrap-in-die marks are considered serious can manufacturing defects if:

  1. the metal plate is fractured; or
  2. the marks are sharp, angular, deep impressions and indicative of potential fracture with handling; or
  3. the marks have broken the inner coating, exposing metal which will react with a corrosive product; or
  4. the formation of the flange is affected.

Scrap-in-die marks are considered minor can manufacturing defects if the marks are smooth, round, and the impressions are shallow.

DESCRIPTION:

An abnormal mark or impression in the metal plate which may vary in size, shape, and depth. If the scrap mark affects the formation of the flange, double seam defects may result.

Refer to the section on DAMAGED COATING (7.7.7) for additional information on fractured coating.

COMMON SOURCES:

  1. Pieces of metal plate (scrap) or other foreign material caught in the die during formation of the two piece can body.

Scrap-in-die Marks - photo 1

Scrap-in-die Marks - photo 2

Scrap-in-die Marks - photo 3

Scrap-in-die Marks - photo 4

7.3.26 DEFECT:  WRINKLED FLANGE

CLASSIFICATION:

Wrinkled flange is considered a serious two piece can defect when the degree of wrinkling is sufficiently pronounced so as to interfere with the formation of the double seam, compromising its integrity.

DESCRIPTION:

Wrinkles in the walls of a two piece style can body extending into the flange area. The resulting flange thickness may be outside of guidelines, or wrinkles may form open channels through the double seam.

COMMON SOURCES:

  1. Improper drawing characteristics of the metal plate, such as temper.
  2. Can body blank moves during the drawing operation.

Wrinkled Flange - photo 1

Wrinkled Flange - photo 2

Wrinkled Flange - photo 3

OTHER CAN BODY DEFECTS

7.3.27 DEFECT:  COATING INSIDE OUT

CLASSIFICATION:

Coating inside out is considered a serious defect for three piece cans and for two piece cans, if the metal is exposed to a corrosive product, otherwise coating inside out is considered a minor defect for two piece cans.

DESCRIPTION:

The inside coating is on the outside of the can, and the outside coating, if present, is on the inside of the can. In three piece cans, this results in coating being present in the area to be soldered which will preclude complete soldering of the side seam. In two piece cans, the hermeticity of the can will not be affected, however, the incorrect (outside) coating, if present, will be in contact with, and may react with, the product.

Coating Inside Out - photo 1
Inside Coating on the Outside -  Outside Coating
Two Piece Cans

Coating Inside Out - photo 2
Inside Coating on the Outside -  Outside Coating
Three Piece Cans

Coating Inside Out - photo 3

Three Piece Can - Inside View

Coating Inside Out - photo 4

Three Piece Can - Outside View

7.3.28 DEFECT:  DOUBLE BODY

CLASSIFICATION:

A double body is considered a serious can body defect for both two piece and three piece cans.

DESCRIPTION:

In a three piece can, this defect occurs when two body blanks form the body of one can. The double seams are often thicker and longer but otherwise normal in appearance. Often the outer body will buckle and the side seam may appear mislocked or incompletely soldered.

COMMON SOURCES:

  1. Two body blanks which are "stuck together" when fed into the body maker.
  2. One body cylinder slid inside the other following formation of the cylinders on the roll former of three piece cans.
  3. Two tapered two piece bodies nested tightly together.
  4. Two pieces of metal plate formed together into a two piece body.
Double Body - photo 1
 Body Buckling
Double Body - photo 2
Two Bodies Formed Together

 Three Piece Cans

Double Body - photo 3

Two Piece Can - Double Body

7.3.29 DEFECT:  INCOMPLETE FLANGE

CLASSIFICATION:

An incomplete flange is considered serious if the flange is reduced by 0.4mm (.016") or more. An incomplete flange is considered minor if the flange is reduced by less than 0.4mm (.016").

DESCRIPTION:

Clips or cuts in the flange resulting in reduced or zero overlap in the double seam.

COMMON SOURCES:

  1. Plate misfeed under die.
  2. Inadequate trim allowance on strip.
  3. Plate moves during the draw.
  4. Starting flange on drawn can (1st operation) too short.

Incomplete Flange - photo 1   Incomplete Flange - photo 2

Incomplete Flange - photo 3

Incomplete Flange - photo 4

Incomplete Flange - photo 5      Incomplete Flange - photo 6

7.4 Can End Manufacturing Defects

(PDF (884 kb))

7.4.1 DEFECT:  BURRS ON CURL

CLASSIFICATION:

Burrs on curl are considered serious can end manufacturing defects if the burr protrudes greater than or equal to 0.5 mm (.020"). Burrs on curl are considered minor can end manufacturing defects if the burr protrudes between 0.5 mm and 0.25 mm (0.020" and 0.010").

DESCRIPTION:

A rough protrusion of metal plate (a burr) on the cut edge of the curl.

COMMON SOURCES:

  1. The end press does not cleanly shear the curl to the desired size.

No photo available

7.4.2 DEFECT:  DOUBLE END

CLASSIFICATION:

A double end is considered a serious container defect.

DESCRIPTION:

Two ends are seamed onto one end of a can body. The double seam has the appearance of additional thickness and length, and may have numerous droops or vees along the double seam.

COMMON SOURCES:

  1. Two strips of end plate are stuck together as they enter the end press. The resulting ends have two thicknesses of plate that are curled together and only the inner end is compound lined.
  2. Two independently formed ends are stuck together and double seamed onto a body.

Double End - photo 1

Double End - photo 2

Double End - photo 3

Double End - photo 4

Double End - photo 5

7.4.3 DEFECT: EXCESSIVELY DEEP OR WEAK SCORELINE

CLASSIFICATION:

Excessively deep scoreline is considered a serious can end manufacturing defect if any of the following conditions are present:

  1. the scoreline is fractured; or
  2. scorelines are not within can maker's guidelines (see description below).

Other serious scoreline defects are:

DESCRIPTION:

The scoreline is a thin single or double line around the end panel where the plate gauge is mechanically reduced by the scoring punch. If the panel is scored too deeply it may fracture or be weakened to the extent that it will break during processing or handling.

An excessively deep scoreline defect should be assessed with reference to the can maker's guidelines, which must include the minimum residual thickness of the scoreline. Its resistance to leakage testing, dye testing or scoreline testing may also be used.

COMMON SOURCES:

  1. Defective manufacture (such as excessive score depth).
  2. Corrosion on scoreline (internal or external).
  3. Embossing on or near scoreline.
  4. Damaged pull tab. (Scoreline has been stressed due to movement of pull tab.)
  5. Physical abuse or stressing of scoreline.
  6. Defective metal plate.
  7. Canning defects due to processing deficiencies (such as overfilling of cans).

No photo available.

7.4.4 DEFECT:  FAULTY SEALING COMPOUND

CLASSIFICATION:

Serious if the faulty compound or faulty application precludes the formation of an hermetic seal (compound skips, missing compound, dried out or runny compound) or if the compound interferes with the formation of the double seam (excess compound).

Minor if the compound is smeared on the inner surface of the end panel as it is non-toxic and does not impart off-odours or off-flavours.

DESCRIPTION:

The improper application of the sealing compound to the can end. The result can be excessive sealing compound, uneven distribution of compound, voids or gaps in the compound on the inside of the end curl. Other faults may be smearing of the sealing compound elsewhere on the end or spraying the sealing compound on the outside of the end curl (called "dirty ends").

COMMON SOURCES:

  1. Plugged or partially plugged compound lining nozzle.
  2. Improper feed of ends to sealing compound applicator.
  3. Faulty compound formula.

Faulty Sealing Compound - photo 1
Excess Compound

Faulty Sealing Compound - photo 2
Compound Skip

Faulty Sealing Compound - photo 3
Compound Smear

Faulty Sealing Compound - photo 4
Dirty Ends

Faulty Sealing Compound - photo 5
Peeling Compound

7.4.5 DEFECT:  INCOMPLETE CURL

CLASSIFICATION:

An incomplete curl is considered as a serious can end manufacturing defect if the curl is reduced by more than 0.4 mm (0.016").

An incomplete curl is considered as a minor can end manufacturing defect if the curl is reduced by less than 0.4 mm (0.016").

DESCRIPTION:

Clips or cuts in the end curl resulting in loss of overlap.

COMMON SOURCES:

  1. Plate misfeed under die.

Incomplete Curl - photo 1

Incomplete Curl - photo 2

7.4.6 DEFECT:  PULL TAB RIVET FRACTURE

CLASSIFICATION:

A fractured pull tab rivet is considered a serious defect.

DESCRIPTION:

A break in that portion of the end panel from which the rivet is formed.

COMMON SOURCES:

  1. Pull tab not properly aligned with rivet maker.
  2. Rivet flattened too tightly.
  3. Lack of lubricant on the rivet area during drawing.

No photo available.

7.4.7 DEFECT:  SCRAP-IN-DIE MARKS

CLASSIFICATION:

Scrap-in-die marks are considered serious can end manufacturing defects if:

  1. the metal plate is fractured; or
  2. the marks are sharp, angular, deep impressions and indicative of potential fracture with handling; or
  3. the marks have broken the inner coating exposing metal which may react with the product; or
  4. formation of the flange is affected.

Scrap-in-die marks are considered minor can end manufacturing defects if the marks are smooth, round, and the impressions are shallow.

DESCRIPTION:

An abnormal mark or impression in the metal plate which may vary in shape, size, and depth. If the scrap mark affects the formation of the curl, double seam defects may result.

Scrap-in-Die Marks - photo 1       Scrap-in-Die Marks - photo 2       Scrap-in-Die Marks - photo 3

7.4.8 DEFECT:  WRINKLED CURL

CLASSIFICATION:

A wrinkled curl is considered as a serious can end manufacturing defect when the degree of wrinkling is sufficiently pronounced so as to interfere with the formation of the double seam, compromising its integrity.

DESCRIPTION:

Wrinkles formed in the curl of can ends. The resulting curl thickness may be outside of guidelines, or wrinkles may form open channels through the double seam.

There are certain cases in which a certain degree of wrinkling in the curl of the can end is introduced by the design of the can end. If such is the case, the wrinkles will be considered as a defect when they are outside of the guidelines of the can end maker.

COMMON SOURCES:

  1. Faulty curler setting.

Wrinkled Curl - photo 1
Wrinkled Curl - photo 2

7.5 Double Seam Defects

(PDF (3,662 kb))

7.5.1 DEFECT:  BROKEN CHUCK

CLASSIFICATION:

A broken chuck is considered a serious seam defect, due to absence of tightness at the point of the defect.

DESCRIPTION:

A portion of the double seam which is not properly ironed-out because of a void in the chuck lip (insufficiently tight), and appearing as an irregularity on the countersink wall of the seam.

COMMON SOURCES:

  1. Chipped seaming chuck caused by a jam-up, or improper set-up.
Broken Chuck - photo 1
Broken Chuck - photo 2

Broken Chuck - photo 3

7.5.2 DEFECT:  CLINCHED ONLY

CLASSIFICATION:

Clinched only is considered as a serious double seam defect.

DESCRIPTION:

Only the clinching operation was completed. Cans are removed to check the clinching operation; these cans must be replaced so that the seaming operation will be completed.

Clinched Only - photo 1

      Clinched Only - photo 2     Clinched Only - photo 3

7.5.3 DEFECT: CUTOVER

CLASSIFICATION:

A cutover is a sharp seam that has fractured and is considered a serious seam defect. A sharp seam is considered a minor seam defect.

DESCRIPTION:

A sharp seam is a sharp fin of metal formed when the seaming panel radius of the end is forced over the top of the seaming chuck flange during the seaming operation. Cutovers are sharp seams which have fractured and often occur at the crossover and with product inclusions but may occur all the way around the double seam; are best detected by running a finger around the inside of the seam.

Alternate Terms: Wire Edge, Feather, Feather Edge

COMMON SOURCES:

  1. Excessive solder in the lap.
  2. Worn seaming chuck.
  3. Worn seaming rolls.
  4. Chuck set too low in relation to first operation seaming rolls.
  5. Second operation rolls set too tight.
  6. Excessive base plate pressure.
  7. Vertical play in the seaming head.
  8. Excessively long body hook.
  9. Inclusion of product in the seam.
  10. Excessive sealing compound.

Cutover - photo 1

Cutover - photo 2     Cutover - photo 3

Cutover graphic showing both 50% reduction and a fracture
Cutover - photo 4

Cutover - photo 5

Cutover - photo 6

Cutovers are often accompanied by other external double
seam defects (as shown above KDC with Cutover)

7.5.4 DEFECT:  CUT-DOWN FLANGE (CDF)

CLASSIFICATION:

A cut-down flange is considered a serious seam defect due to the absence of overlap.

DESCRIPTION:

A portion of the body flange which is torn or cut with part of the flange turned back against the can body, without being engaged with the end hook, and may protrude below the bottom of the normal seam. Severe forms of this defect result in a hole in the can body just below the double seam.

A unique type of CDF is the "index fault" found on reformed cans which consists of a characteristic tear in the flange approximately 10-15 mm from the reform ridge on the can body, due to flange damage caused by the reformer picker finger.

COMMON SOURCES:

  1. Flange damage during handling of open top cans.
  2. Flange damage during filling.
  3. Flange damage from other canning line equipment.
  4. Flange damage from the grip chain during formation of the can body cylinder.
  5. Mis-indexing of collapsed can body blanks during reforming.

Cut-Down Flange (CDF) - photo 1

Cut-Down Flange (CDF) - photo 2

Cut-Down Flange (CDF) - photo 3

Cut-Down Flange (CDF) - photo 4

Cut-Down Flange (CDF) - photo 5

7.5.5 DEFECT: DROOP

CLASSIFICATION:

The only true assessment is done in a teardown where optical seam measurements of the overlap and seam tightness are assessed applying can manufacturing guidelines.

Any droop assessed as having 25% or less optical overlap will be classified as a serious double seam defect.

Any droop assessed as having 25% to 50% optical overlap will be classified as a minor double seam defect.

When a visual assessment is carried out, the droop will be considered a serious double seam defect if it extends more than 20% of the seam length, or more than 1 cm (3/8") along the seam, or if there is more than one droop on the double seam (confirmation of the classification must be from optical overlap measurements as indicated above).

DESCRIPTION:

A smooth projection of the end hook of the double seam below the bottom of the normal seam. A droop which shows signs of second operation roll marks will be assessed for classification in terms of overlap; otherwise see FRACTURED SEAM (7.5.7).

COMMON SOURCES:

  1. Inclusion of product or foreign material in the double seam.
  2. Excessive amount or unequal distribution of sealing compound.
  3. First operation seam too loose or too tight.
  4. Worn first operation roll groove.
  5. Body hook too long.

Droop - photo 1 Droop - photo 2

Droop - photo 3

Droop - photo 4

Droop - photo 5

Droop - photo 6

7.5.6 DEFECT:  FALSE SEAM

CLASSIFICATION:

A false seam is considered a serious seam defect due to the absence of overlap.

DESCRIPTION:

A defect where a portion of the body flange is bent back against the body, without being engaged with the end hook, but does not protrude below the bottom of the end hook radius. This is similar to a knocked-down flange defect where the body flange is visible below the end hook radius. This defect is difficult to observe and requires close visual inspection of the underside of the double seam where sometimes two layers of metal can be seen. Confirmation of this classification often requires a seam cut to observe the configuration of the end curl and body flange.

COMMON SOURCES:

  1. Flange damage (bent flange) during shipping, depalletizing, filling the can; from feed screw, the clincher, the seamer; or from product or foreign material on the flange.
  2. Mushroomed can flange.
  3. Damaged or bent end curl.
  4. Misalignment of can during assembly.

False Seam - graphic 1    False Seam - photo 1

False Seam - photo 1  False Seam - photo 2

False Seam - photo 3

False Seam - photo 4

False Seam - photo 5

False Seam - photo 6  False Seam - photo 7

False Seam - photo 8

7.5.7 DEFECT:  FRACTURED SEAM

CLASSIFICATION:

A fractured seam is considered a serious seam defect when the metal is fractured.

DESCRIPTION:

A fracture or break in the end hook radius. This defect may be difficult to observe without magnification. Seams which show second operation roll marks should be closely examined for this defect, particularly at the side seam or if a droop is present.

Sometimes designated: Cut Seam (see CUT SEAM 7.7.5)
Alternate Term: Split Droop

COMMON SOURCES:

  1. Seam too tight.
  2. Excessive solder in the lap.
  3. Defective end plate.
  4. Excessive sealing compound.
  5. Inclusion of product or foreign material in the seam.
  6. Excessively long end hook resulting from first operation being too tight.

    Fractured Seam - graphic 1    Fractured Seam - photo 1

Fractured Seam - photo 2

Fractured Seam - photo 3
Fractured Seam - photo 4

Fractured Seam - photo 5

7.5.8 DEFECT:  INSUFFICIENT OVERLAP

CLASSIFICATION:

Any portion of the double seam having an optical overlap of less than 25% of the internal seam length is considered to contain a serious double seam defect.

DESCRIPTION:

The can manufacturer provides a guideline for each can size and style outlining the seam measurements and tolerances for which the double seam was designed to ensure an hermetic container. Adequate overlap is an essential requirement for the integrity of a double seam.

The body and end hooks must overlap sufficiently to ensure that the sealing compound is properly held under compression with the correct seam tightness. Calculating overlap by formula provides only an estimate of the overlap. There is no accurate substitute for optical measurement.

COMMON SOURCES:

  1. Improper mechanical interlocking of the body flange and end curl.
  2. Incorrect setting of seaming rolls, lifters or base plate loads.
  3. The presence of other material in the seaming areas (e.g., product, excess solder, excess sealing compound, foreign material).
  4. Damaged or incomplete flanges or curls.

No photo available.

7.5.9 DEFECT:  JUMPED SEAM

CLASSIFICATION:

A jumped seam is considered a serious seam defect due to inadequate seam tightness.

DESCRIPTION:

Externally, this defect may appear as a looseness of the seam at one side of the crossover. Internally this defect appears as two or three looseness wrinkles at one side of the crossover. The defect occurs when the seaming rolls jump off the extra thickness of the crossover area. The side of the crossover on which the defect occurs depends on the seaming roll direction in relation to the crossover.

COMMON SOURCES:

  1. Operation of the closing machine at excessive speed.
  2. Sluggish acting second operating seaming roll cushion spring.
  3. Second operation seaming roll cushion spring too weak. This defect would be identified on tear down.
  4. Broken cushion spring. This defect would be observable externally.
  5. Can lap too thick at double seam area.
  6. Excessive external solder at can body lap.
  7. Insufficient seam tightness setting.

Jumped Seam

7.5.10 DEFECT: KEY TAB NOT PROPERLY TUCKED

CLASSIFICATION:

Key tab not properly tucked is considered a serious double seam defect if:

  1. there is insufficient overlap (see 7.5.8) present at the key tab area of the double seam; or
  2. there are vees present adjacent to key tab; or
  3. there is evidence of leakage.

DESCRIPTION:

The key tab portion of end curl not properly incorporated into the double seam resulting in reduced or no overlap. The key tab may be cocked (crooked) or extended downward (partially or completely). Vees may be present on either side of the key tab and the double seam may be fractured.

COMMON SOURCES:

  1. Defective/damaged can end.
  2. Defective/damaged body flange.
  3. Improper adjustment of seamer.
  4. Worn 1st or 2nd operation rolls.
  5. Overfilling of cans with product.
  6. Defective sealing compound.

Graphic of key tab not properly tucked - showing cross section of normal key tab and cross section of key tab not tucked Key Tab Not Properly Tucked - photo 1

7.5.11 DEFECT:  KEY TAB SEAMED TO INSIDE

CLASSIFICATION:

A key tab seamed to the inside of the double seam is considered a serious double seam defect.

DESCRIPTION:

The key tab is not visible from the exterior of the can. There may be vees on either side of the area where the key tab is normally located. The tab is seen on the inside of the can when opened.

COMMON SOURCES:

  1. Misfeed of the end to the double seamer.
  2. Key tab damaged prior to seaming.

Key Tab Seamed To Inside - photo 1

Key Tab Seamed To Inside - photo 2

7.5.12 DEFECT:  KNOCKED-DOWN CURL (KDC)

CLASSIFICATION:

A knocked-down curl is considered a serious double seam defect due to the absence of overlap.

DESCRIPTION:

A portion of the end hook which is not engaged with the body hook but is turned down against the can body exposing the cut edge of the end plate. Variations of this defect can range from a 'V' with the edge of the end plate exposed, to complete knocking-down of the end hook all the way around the can.

COMMON SOURCES:

  1. Inclusion of product or foreign material in the seam.
  2. Chuck set too low in relation to the base plate.
  3. Damaged or bent end curl.
  4. Misalignment of can during assembly.

Knocked Down Curl (KDC) - photo 1

Knocked Down Curl (KDC) - photo 2   Knocked Down Curl (KDC) - photo 3

Knocked Down Curl (KDC) - photo 4   Knocked Down Curl (KDC) - photo 5

Knocked Down Curl (KDC) - photo 6      Knocked Down Curl (KDC) - photo 7

Knocked Down Curl (KDC) - photo 8

Knocked Down Curl (KDC) - photo 9

Knocked Down Curl (KDC) - photo 10

Knocked Down Curl (KDC) - photo 11

7.5.13 DEFECT:  KNOCKED-DOWN END (KDE)

CLASSIFICATION:

A knocked-down end is considered a serious seam defect, due to the absence of overlap.

DESCRIPTION:

Severe distortion of the can end, as though struck by a downward blow inside the countersink, such that the hooks are disengaged or fail to engage, and part of the curl is pulled back to expose the flange. In severe forms of this defect the end curl is pulled back to expose (form) a hole in the can end.

Alternate Term: Pushed-in Bottom

COMMON SOURCES:

  1. Scrap jammed in the seaming head.

Knocked Down End (KDE) - photo 1

Knocked Down End (KDE) - photo 2

Knocked Down End (KDE) - photo 3

Knocked Down End (KDE) - photo 4

Knocked Down End (KDE) - photo 5

Knocked Down End (KDE) - photo 6

7.5.14 DEFECT:  KNOCKED-DOWN FLANGE (KDF)

CLASSIFICATION:

A knocked-down flange is considered a serious seam defect due to the absence of overlap.

DESCRIPTION:

A portion of the body flange which is bent back against the body, without being engaged with the end hook, and protruding below the bottom of the end hook radius. This is similar to a false seam defect where the body flange is not readily visible below the end hook radius. Severe forms of this defect involve knocking-down of both the flange and body leaving a distinctive gap between the can end and body. When caused by a feed screw (spacer) on the canning line, the defect has a distinctive "V"-shaped dent to the flange and body with a "signature" scratch down the centre.

COMMON SOURCES:

  1. Flange damage during filling.
  2. Flange damage during shipping or depalletizing.
  3. Flange damage from canning line screw feed.
  4. Flange damage from the clincher or seamer.
  5. Flange damage from product or foreign material on the flange.
  6. Mushroomed can flange.
  7. Damaged or bent end curl.
  8. Misalignment of can during assembly.
Knocked Down Flange (KDF) - graphic 1
Knocked Down Flange (KDF) - photo 1

Knocked Down Flange (KDF) - photo 2

Knocked Down Flange (KDF) - photo 3

Knocked Down Flange (KDF) - photo 4

Knocked Down Flange (KDF) - photo 5

Knocked Down Flange (KDF) - photo 6

Knocked Down Flange (KDF) - photo 7

7.5.15 DEFECT: LOOSE SEAMS

CLASSIFICATION:

A loose seam is considered a serious double seam defect if:

  1. seam tightness is less than the minimum required by the can manufacturer's guidelines; or
  2. for round can product where can manufacturer's published guidelines are not available, tightness ratings as specified in table 4.1.5 will be applied; or
  3. containers which are non-round and are designed for no vacuum, and where can manufacturer's guidelines are not available, tightness ratings are less than 50%, and for other non-rounded containers and where manufacturer's guidelines are not available, tightness ratings as specified in table 4.1.5 will be applied; or

  4. there is any evidence of leakage; or
  5. the percentage "free space" exceeds 33% of the combined metal thickness comprising of the double seam or the percentage "compactness" is less than 75% in the prime sealing area.

DESCRIPTION:

A loose seam is normally characterized by one or more of the following conditions: rounded appearance of the double seam profile (a bowed seam configuration); seam thickness which exceeds accepted can manufacturer's guidelines; the can has a faint or no pressure ridge; and a low tightness rating. In severe examples of loose seams, the body hook and the end hook of a cut out (seam saw cross section) double seam may slide apart. This slippage condition in the double seam would demonstrate loose seam condition.

COMMON SOURCES:

  1. Loose 1st operation.
  2. Loose 2nd operation.
  3. Worn 1st or 2nd operation rolls.
  4. Improper roll profile.
  5. Defective can end.
  6. Poor can end design.
  7. Pre-wrinkle in seaming panel or end curl.

Loose Seams - photo 1    Loose Seams - photo 2

7.5.16 DEFECT:  NO SECOND OPERATION

CLASSIFICATION:

No second operation is considered as a serious double seam defect.

DESCRIPTION:

Only the first operation was completed. Cans are removed to check the first seaming operation; these cans must be replaced so that the second operation seaming will be completed.

No Second Operation - photo 1

Normal Double Seam                                No Second Operation

No Second Operation - photo 2

No Second Operation - photo 3

7.5.17 DEFECT:  PLEATS

CLASSIFICATION:

A pleat is considered a serious defect if the pleat extends to the bottom of the double seam.

DESCRIPTION:

A pleat is a fold in the end hook which may be accompanied by a small vee-shaped projection of the end hook radius and the metal of the fold may be fractured. A pucker is intermediate between a wrinkle and a pleat, where the end hook is locally distorted downwards; it may or may not be externally visible.

COMMON SOURCES:

  1. Clincher or first operation rolls set too loose.
  2. Worn rolls.
  3. Second operation rolls set too tight will aggravate the pleat or pucker.
  4. Poor can end design.
  5. Residual wrinkle along end curl.

Pleats

Pleats

Pleats - graphic 1    Pleats - photo 3

Pleats - photo 4

Pleats - photo 5

Pleats - photo 6 

Inset Shows the End Curl

7.5.18 DEFECT: PUCKER

CLASSIFICATION:

A pucker is considered a serious defect if there is insufficient overlap (see 7.5.8).

DESCRIPTION:

A pucker is intermediate between a wrinkle and a pleat where the end hook is locally distorted downwards; it may or may not be externally visible.

COMMON SOURCES:

  1. Clincher or first operation rolls set too loose.
  2. Worn rolls.
  3. Second operation rolls set too tight will aggravate the condition.
  4. Poor can end design.
  5. Residual wrinkle along end curl.

graphic showing serious and minor puckers
Serious Pucker                              Minor Pucker

Pucker - photo 1 Pucker - photo 2 Pucker - photo 3

7.5.19 DEFECT: SEAM INCLUSIONS

CLASSIFICATION:

Seam inclusions are considered as serious double seam defects.

DESCRIPTION:

Extraneous material or product included in the double seam.

COMMON SOURCES:

  1. Product over flange.
  2. Scrap metal from a filler jam up.
  3. Solder pellets.

Seam Inclusions - photo 1

Seam Inclusions - photo 2

Seam Inclusions - photo 3

Parchment Paper Formed Into Double Seam

7.5.20 DEFECT: SIDE SEAM DROOP

CLASSIFICATION:

The only true assessment is done in a teardown where optical seam measurements of the overlap and seam tightness are assessed applying can manufacturing guidelines.

Any side seam droop assessed as having 25% or less optical overlap will be classified as a serious double seam defect.
Any side seam droop assessed as having 25% to 50% optical overlap will be classified as a minor double seam defect.

When a visual assessment is carried out, the droop will be considered a serious double seam defect if it extends more than 20% of the seam length, or more than 1 cm (3/8") along the seam, or if there is more than one droop on the double seam (confirmation of the classification must be from optical overlap measurements as indicated above).

DESCRIPTION:

A smooth projection of the end hook of the double seam below the bottom of the normal seam at the crossover. A slight droop at the crossover may be considered normal because of the additional plate thicknesses incorporated in the seam structure. However, excessive droop at this point is not acceptable.

COMMON SOURCES:

  1. Excess external solder at the can body lap.
  2. Can lap too thick at the double seam area (thick lap).

Side Seam Droop - photo 1

Side Seam Droop - photo 2

Side Seam Droop - photo 3

7.5.21 DEFECT:  SPINNER

CLASSIFICATION:

A spinner is considered a serious seam defect due to inadequate tightness.

DESCRIPTION:

A spinner is an incompletely ironed out double seam. It occurs when the chuck slips on the can end. This defect is characterized by part of the seam having normal thickness and part of the seam being loose (thick). This defect may be accompanied by a scuffing of the countersink wall radius caused by the chuck slipping. First operation spinner shows signs of vees around can, second operation spinner has incomplete double seam.

Deadhead - this terminology applies for can revolve closing machines.
Spinner - this terminology applies for can standstill closing machines.

Alternate terms: Deadhead, Skidder, Incomplete Double Seam
Associated Conditions: Scuffed Seam

COMMON SOURCES:

  1. Insufficient lifter pressure.
  2. Improper end fit with chuck, size or taper, either too loose or too tight.
  3. Worn seaming chuck.
  4. Incorrect pin height setting. Chuck set too high in relation to base plate.
  5. Seaming rolls binding.
  6. Oil or grease on seaming chuck or lifter.
  7. Any vertical play of seaming chuck spindle.
  8. Improper timing.

Spinner - graphic 1    Spinner - photo 1

Spinner - photo 2 
Top view showing incompletely ironed out double seam

Spinner - photo 3
Countersink wall radius showing scuffing caused by chuck slipping

7.5.22 DEFECT:  VEE

CLASSIFICATION:

Vees are considered to be serious double seam defects due to the absence of overlap at the point of the vee.

DESCRIPTION:

A sharp 'V' shaped projection of the end hook of the double seam below the bottom of the normal seam which results in no overlap.

Alternate Terms: Lip, Spur

COMMON SOURCES:

  1. Inclusion of product/bones or foreign material in the double seam.
  2. First operation seam too loose.
  3. Worn first operation roll groove.

Vee - photo 1
Vee - photo 2

Vee - photo 3

Multiple Defects May Occur - As Shown a Knocked Down Curl Plus a Serious Vee

Vee - photo 4    Vee - photo 5

Vee - photo 6

Vee - photo 7     Vee - photo 8

7.6 Other Manufacturing Defects

(PDF (562 kb))

7.6.1 DEFECT:  MISEMBOSSING

CLASSIFICATION:

Misembossing is considered a serious can end defect if:

  1. the metal shows signs of fracture at the the point of embossing; or
  2. any part of the embossing has struck a sensitive area such as an easy open pull ring or scoreline.

DESCRIPTION:

Misembossing includes sharp, illegible, misplaced, or multiple embossing. Sharp embossing may fracture the coating, leading to corrosion and perforation, or it may fracture the metal plate. Misplaced embossing which interferes with the pull tab or is on the scoreline or reinforcement lines or rings is likely to cause a fracture of the metal plate.

COMMON SOURCES:

  1. A can end going through the embosser twice.
  2. Excessive embossing pressure.
  3. Mismatched embossing dies.
  4. Misfeed of can into embosser.

   Misembossing - photo 1   Misembossing - photo 2

Misembossing - photo 3

Misembossing - photo 4

Misembossing - photo 5

7.6.2 DEFECT:  OVERFILL, FLIPPER, SPRINGER, AND SWELL

CLASSIFICATION:

Must be treated as a serious container defect unless testing proves otherwise.

DESCRIPTION:

The terms overfill, flipper, springer, and swell are used to describe cans which have end(s) distended to varying degrees from several causes. The cans must be checked for microbial growth, chemical reaction such as hydrogen gas production, internal corrosion or weight.

COMMON SOURCES:

  1. Overfilling or failure to draw a proper vacuum.
  2. Microbial spoilage with gas production resulting from under processing.
  3. Microbial spoilage with gas production resulting from post-process contamination.
  4. Microbial gas production during time lag between closing and processing.
  5. Hydrogen gas production from a chemical reaction of product with the metal plate.

Overfill, Flipper, Springer, and Swell - photo 1    Overfill, Flipper, Springer, and Swell - photo 2

7.6.3 DEFECT:  PANELLING

CLASSIFICATION:

Panelling is considered a serious container profile defect if the can body has been sharply distorted such that the internal coating has fractured or the double seam or side seam has been distorted.

DESCRIPTION:

A permanent distortion (collapsing) of the can body generally observed on larger sized containers. Appears as flat, vertical panels or indentations of the can body.

COMMON SOURCES:

  1. Excessive closure vacuum.
  2. Excessive external pressure on the can during processing.
  3. Excessive pressure during cooling.
  4. Inadequate plate gauge or temper.

    Panelling - photo 1    Panelling - photo 2

7.6.4 DEFECT:  PEAKED CAN

CLASSIFICATION:

A peaked can is considered a serious container profile defect if the can end has been sharply distorted such that the metal plate or coating has fractured or the double seam has been distorted.

DESCRIPTION:

A permanent outward distortion of the can end in the form of pyramidal-like deformities near the double seams, resulting from a large differential between internal and external container pressures. Excessive peaking will adversely affect the integrity of the double seam.

Alternate Terms: Buckling, Buckled End

COMMON SOURCES:

  1. Insufficient closure vacuum.
  2. Insufficient external pressure during cooling.
  3. Incipient spoilage before processing, resulting in vacuum loss.
  4. Inadequate plate gauge or temper of the end plate.
  5. Overfilling of the can.

        Peaked Can - photo 1    Peaked Can - photo 2

7.7 Handling Defects

(PDF (2,249 kb))

7.7.1 DEFECT:  ABRASION

CLASSIFICATION:

Abrasion is considered a serious container defect when the metal has been reduced to less than 50% of its normal thickness.

DESCRIPTION:

A mechanical wearing of the metal plate. Abrasion results in the weakening of the metal plate making the abraded area susceptible to either fracture or corrosion which could eventually perforate the metal plate.

COMMON SOURCES:

  1. The action of moving cable or metal conveyors on stationary cans. This may occur with either empty or filled cans.
  2. Cans being moved against stationary objects with sharp parts. For example loading cans into damaged or rusted retort baskets.
Abrasion - photo 1
Abrasion - photo 2
Abrasion - photo 3
Abrasion - photo 4

7.7.2 DEFECT:  CHALKY SIDE SEAM

CLASSIFICATION:

Chalky side seam is considered a minor side seam defect.

DESCRIPTION:

Chalky white deposits or corrosion on the side seam solder, which are unlikely to develop into a rusting condition.

COMMON SOURCES:

  1. Alkaline boiler water carry over in the 8.0 to 9.0 pH range.
  2. "Green" or wet pallet boards.
  3. Salt air exposure and/or high humidity.
  4. May be noted on cans stored for an extended period of time under unfavorable storage conditions.

chalky Side Seam - photo 1

chalky Side Seam - photo 2

7.7.3 DEFECT: CORROSION

CLASSIFICATION:

Corrosion is considered to be a serious container defect if:

  1. the corrosion causes pitting; or
  2. the corrosion is on any sensitive area of the container such as the scoreline

DESCRIPTION:

The deterioration of the metal plate from the inside or the outside of the container as a result of chemical reaction which can lead to penetration of the metal plate. Most commonly seen is external corrosion (rust) due to dampness (see also COATING SKIPS 7.2.2).

COMMON SOURCES:

  1. Wet cans due to either excessive post-process cooling or insufficient tipping time (drainage) following retorting.
  2. Improper temperatures and humidity levels in the warehouse.
  3. Cans unprotected from weather during transport or storage.

Corrosion - photo 1  Corrosion - photo 2

Corrosion - photo 3

Corrosion - photo 4

Corrosion - photo 5

Corrosion - photo 7

Corrosion - photo 6

Corrosion - photo 8

7.7.4 DEFECT:  CRUSHED

CLASSIFICATION:

A crushed can is considered a serious container defect.

DESCRIPTION:

An extreme mechanical deformation of the metal container.

COMMON SOURCES:

  1. Misfeed of the filled can in conveying equipment.
  2. Transit damage.

Crushed - photo 1

Crushed - photo 2

Crushed - photo 3

Crushed - photo 4

7.7.5 DEFECT:  CUT SEAM

CLASSIFICATION:

A cut seam is considered a serious double seam defect.

DESCRIPTION:

The physical tearing or cutting through of the outer layer of metal plate on the double seam, such that the inner layers of the double seam are exposed and the integrity of the double seam is compromised.

Alternate Terms: Torn Seam, Cable Cut
Sometimes designated: FRACTURED SEAM (see 7.5.7)

COMMON SOURCES:

  1. Cans contacting weld beads or rough metal during conveying.
  2. Mishandling of the metal containers either during pre-processing or post-processing.
  3. The action of moving cable on stationary cans.
Cut Seam - photo 1
Cut Seam - photo 2
Cut Seam - photo 3

7.7.6 DEFECT: DAMAGE TO SCORELINE/PULL TAB

CLASSIFICATION:

Damage to scoreline and/or pull tab is considered a serious can handling defect when:

  1. the scoreline is broken at the point of the tab; or
  2. the rivet is fractured or broken; or
  3. there is any evidence of loss of hermeticity.

DESCRIPTION:

A pull tab which has been twisted or distorted out of the horizontal or parallel plane with the can end. The scoreline may be pierced by the point of the tab, possibly resulting in leakage. The pull tab rivet may have been fractured or broken.

COMMON SOURCES:

  1. Defective can ends.
  2. Physical abuse.
  3. Embossing on or near the scoreline.
  4. Weak scoreline - exterior rust on scoreline (tin or tin free ends).
  5. Weak scoreline - interior corrosion on the scoreline.
  6. Defective or damaged pull tab (score pierced by the point of the tab).
  7. Weak scoreline - excessive score.
  8. Canning defects - overfilling, double seamer adjustment problems.

photo showing Damage to Scoreline/Pull Tab

7.7.7 DEFECT:  DAMAGED COATING

CLASSIFICATION:

Damaged coating is considered a serious material handling defect if metal is scored and the product packed is corrosive.

Damaged coating is considered a minor material handling defect when exposed metal is not susceptible to rust and corrosion.

DESCRIPTION:

Obvious physical damage to either the inside or outside coated surface of the can end or can body which exposes bare metal, such as scratches, rub or scuff marks, essentially cosmetic in nature, but susceptible to corrosion (see CORROSION - 7.7.3).

While fracture of the metal plate is obviously a loss of hermetic seal, the fracture of the coating may or may not result in reaction of the metal with the product or loss of hermetic seal. Where the metal is coated with tin and then overlayered with an organic coating, there is a double system of protection. If the product is very aggressive to tinplate, then the organic coating is very important. If the product is not aggressive to tinplate, then the loss of the organic coating is not important, especially if there is no reduction in expected shelf life of the product.

COMMON SOURCES:

  1. Mishandling of the coated metal plate used to manufacture can bodies or ends.
  2. Mishandling of the can bodies or ends following manufacture, i.e., during shipping, storage, processing and subsequent handling.

Damaged Coating - photo 1   Damaged Coating - photo 2

7.7.8 DEFECT: DAMAGED CURL/FLANGE

CLASSIFICATION:

A damaged end curl is considered a serious handling defect when the end curl interferes with the double seam formation.

A damaged flange is considered a serious handling defect when damage extends more than 0.8 mm (1/32") from the normal flange level or is of sufficient size to cause a defective double seam.

DESCRIPTION:

A dented, bent or deformed end curl on the can end(s) or flange on can body such that it may cause seaming difficulties such as can end feed jam-ups and defective double seams.

COMMON SOURCES:

  1. Mishandling of the can ends or can body during the manufacturing process, in transit handling and in storage, or during use in the cannery.
  2. Machine damage during manufacture.
  3. Scrap-in-die damage or deformation of the metal plate.

Damaged   Curl/Flange - photo 1

Damaged   Curl/Flange - photo 2   Damaged Curl/Flange - photo 3

Damaged   Curl/Flange - photo 4

Damaged Curl/Flange   - photo 5

Damaged Curl/Flange - photo 6

Damaged Curl/Flange - photo 7

Damaged Curl/Flange - photo 8

7.7.9 DEFECT:  DENT

CLASSIFICATION:

A dent is considered a serious container defect if the can body or end has been sharply distorted such that:

  • the containers have bulged one or both ends, other than pressurized containers; or
  • the body dent has pulled on the double seam such that the distortion of the end seam exceeds the countersink depth of that specific can size and results in the double seam dimensions being outside of the can makers published guidelines; or
  • the metal plate has fractured, or the fracture of the coating has exposed metal which may react with a corrosive product; or
  • the container shows evidence of content leakage.

DESCRIPTION:

The pronounced mechanical distortion of the metal container resulting in either significant reduction of the internal volume of the container or deformity of the can end or body, the double seam, or the side seam. Dents may crease the metal plate which may adversely affect the internal coating causing susceptibility to corrosion. Dents may distort the double seam or side seam such that vacuum loss may occur.

COMMON SOURCES:

  1. Mishandling of the empty or filled cans during conveying, transporting, labelling, or preparing the product for marketing.

   Dent - photo 1   Dent - photo 2

Dent - photo 3
Dent - photo 4

Dent - photo 5

Dent - photo 6
Dent - photo 7

Lower limit of a serious body dent.  Body dent is sharp and deep and the double seam has been pulled down below the level of the countersink depth of the can.

Dent - photo 8

Dent - photo 9

Dent - photo 10

Dent - photo 11
Dent - photo 12

Upper limit of a minor body dent.  Body dent is sharp and deep.  Need to assess the inside coating for possible fractures, if the contents are considered as being a corrosive product which will react with the container, and the double seam has been distorted so that the dimensions are outside of the can maker's guidelines.

7.7.10 DEFECT: DOUBLE SEAM DENT

CLASSIFICATION:

A double seam dent is considered a serious defect when:

  1. the dent is sharp (V-shaped), and fails the leak, pressure, vacuum or dye tests; or
  2. the containers have bulged one or both ends as a result of the impact to the double seam; or
  3. the container shows evidence of content leakage.

DESCRIPTION:

The mechanical deformation of the double seam (can rim) of the container, caused by a sharp blow or excessive mechanical force to the double seam. Double seam (rim) dents can adversely affect the integrity of the double seam resulting in a potential for post-process contamination.

COMMON SOURCES:

  1. Mishandling of the closed can either during pre-processing or post-processing. Post-processing is anytime after retorting, during labelling, transport or storage.
Double Seam Dent - photo 1
Pulled Seam
Double Seam Dent - photo 1
Rim Dent

7.7.11 DEFECT:  FOREIGN CONTAMINATION INSIDE

CLASSIFICATION:

Foreign contamination inside the can is considered a serious defect.

DESCRIPTION:

Any observable amount of oil, grease, glue or dirt which is present on the inside surface of can ends or can bodies.

COMMON SOURCES:

  1. Grease or oil dripping from machines.
  2. Excess material being deposited during manufacture.
  3. Contamination during storage or handling of empty cans or can ends.

       Foreign Contamination Inside

7.7.12 DEFECT:  PUNCTURED

CLASSIFICATION:

A puncture is considered a serious container defect.

DESCRIPTION:

The complete penetration through the metal plate of the can body or end by a sharp object such that there is loss of hermeticity.

COMMON SOURCES:

  1. Punctures from sharp corners of equipment.
  2. Punctures from sharp objects such as staples.
  3. Cuts or gashes from knives or similar tools.
  4. Punctures from forks on lift trucks.

 Punctured - photo 1

Punctured - photo 2

7.7.13 DEFECT:  SCORED

CLASSIFICATION:

A scored can end or can body is considered a serious can handling defect.

DESCRIPTION:

A sharp linear stressing (deformation) of the metal plate such that either the metal plate is fractured (has failed), or there is potential for failure due to corrosion or stress from normal handling.

COMMON SOURCES:

  1. Deep scratching of the metal plate surface on either the inside or the outside of the container.

Scored - photo 1

Scored - photo 2