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Blow Molded Bottle Leak Detection Overview For Executives

Heidi Amsler

WHERE DO LEAKS COME FROM?

The blow molding of bottles involves the stretching of plastic under air pressure to force the bottle wall material against the internal walls of a mold to give a bottle its final shape.  In the case of extrusion blow molding, the plastic is melted in the extruder barrel by mechanical working and electrical heating to achieve a viscosity that can be shaped into a cylinder (parison) that is then welded into a body with only one opening through which the compressed air is introduced to perform the final shaping.  Why do holes appear in the final product?  First, the amount of stretching can exceed the ability of the plastic to stay together and the bottle wall can thin down to nothing, causing a tear.  Second, impurities (dirt) can be introduced into the plastic through the recycling of scrap that is blended with virgin resin and it’s also possible that dirt particles can find their way into the resin storage boxes (gaylords) or silos.  In this case, the molten plastic does not adhere to the dirt particle and it causes a weak point in the bottle wall.  Third, blow-molded bottles can contain several welded areas, such as at the base of the bottle, on the sides below the neck to make a taper, and around the inside of handles formed by welding and cutting out the center of the handle so the user’s hand can pass through (milk gallons).

WHY ARE LEAKY BOTTLES A PROBLEM?

One might think that losing a few bottles because of leaks would not be a major cost to a blow molder.  That is right, when the leaker is discovered, rejected, and recycled into a new bottle by re-melting the plastic.  However, after a bottle has been labeled, filled with a liquid and capped, then packed into a box that is stored and transported stacked up eight feet high, one leaker can cause a much larger loss in a damaged product that has to be scrapped.  Another example is in the home and office water delivery business.  When a bottle is upside-down on a dispenser, it is the vacuum in the bottle that keeps the water from running out onto the floor and requiring the repair or replacement of the floor.  A small leak in the base of the 5-gallon bottle will allow this damage to occur, which the water supplier normally has to pay to repair.

WHAT MAKES BOTTLE LEAK DETECTION DIFFICULT?

A common type of leak detector operates on the pressure-drop principle, meaning that a known pressure of air is created in the bottle and the system is sealed off.  If the drop in the pressure occurring over a set time exceeds a certain limit, it indicates that the bottle has a leak.   Leak testing takes place immediately after blow molding or, in the case of purchased bottles, immediately before filling.  In either case, the line speeds can be in the thousands of bottles per hour.  This limits the time to test each bottle to a few seconds.  Because leaks are small and the pressure that is used to test the bottles is low so that the bottles are not distorted, the detection of a pressure drop inside the bottle requires very sensitive instruments called transducers.  The evolution of automation equipment and digital computers over the years has made leak detectors more accurate and also made them a source of quality control data that documents the performance of the blow molding operation.

WHAT TYPES OF LEAK DETECTORS ARE AVAILABLE?

Several different designs have been in the market.  In one type, air at a known pressure is introduced into a tank of fixed volume and then this air is released into the bottle and the final pressure in the bottle is measured to see if it achieves the expected value.  This method relies on all bottles being of the same size.

The most common type of leak detector is the pressure drop test as described above.  The simplest have a single test head and a conveyor that indexes to bring each bottle under it.  With the bottle stationary, an air cylinder moves the test head down onto the neck of the bottle.  A soft rubber seal prevents leakage from the contact area between the test head and the neck of the bottle.  A valve opens and allows air to fill the container to set pressure and then closes.  The pressure in the bottle attains a level and settles down to a steady reading and then the test period begins.  If the pressure stays above a set level, the bottle is good.  Otherwise, the bottle is rejected from the conveyor.

In addition to detecting leaks, pressure-decay bottle inspection units can often be set up to test for the following:

  • Wall thickness variation
  • Choked / obstructed necks
  • Defective neck finish
  • Color
  • Fallen bottles

Click Link for Leak Testing Videos: https://amslerequipment.com/en/leak-testers/

Screenshot of Leak Tester User Interface

Another test method is the use of a vacuum pump to create a negative pressure inside the bottle when compared to the atmospheric pressure in the room outside the bottle.  This test can work better in some cases involving cracks, rather than holes in the wall of the bottle.  In this case, if the low pressure inside the bottle rises by a given amount during a set time, due to the entrance of air from the outside into the bottle, the test shows the presence of a leak.

Leak testers can have a single head or multiple heads.  These can be stationary or “flying”, meaning that the heads follow the bottles on the conveyor as they pass by without stopping the conveyor.  The flying-head leak tester can test faster than a stationary-head tester and multiple-head testers are able to test faster than a single-head leak detector.  Beyond the design of the leak detector, the speed that a leak detector can achieve is dependent on the bottle size (the smaller, the faster) and the size of the smallest hole that the operator wants to detect.  The smaller the hole (.006 inches is a reasonable lower limit), the longer it takes for the test to occur and the fewer bottles can be tested per hour.

Pictured Above Manual Table Top Leak Tester

PET stretch blow molding machines in Canada, USA

W. Amsler Announces First Commercial Application for 64oz PET Barrier Growler for Craft Beer Market

Heidi Amsler

BOLTON, Ontario, June 14, 2019 – W. Amsler Equipment Inc., a leading supplier of all-electric linear PET stretch blow molders, has announced the first commercial sale of 64-oz polyethylene terephthalate (PET) growler jugs to Arch Brewing Co., an independently owned craft brewery in Newmarket, Ontario. The beer container mimics the competitive glass design and provides barrier protection for extended shelf life. Arch Brewing will offer the PET growler as an event-safe alternative to its glass growler.

W. Amsler has focused new resources and expanded its participation in the beer and spirits packaging market. It has provided market-entry assistance to customers like JMS International Packaging, a leading packaging solutions provider, in the areas of design, development, and pre-production runs. “This is a major milestone for us in terms of cracking the craft beer industry,” said Marc Leblanc, owner of JMS International Packaging. Heidi Amsler, sales and marketing manager for W. Amsler, said: “We’re excited about the future prospects of converting glass to PET and creating environmentally-friendly barrier packaging for the beer and spirits markets.”

The idea of using PET growlers was appealing right from the outset, according to Sue King, owner of Arch Brewing. She noted that the shape, color, and look of the bottle were a close match to the traditional 1.9L glass growler bottle that is common in the industry. “Growlers are a really big seller for us and we see an opportunity for growth with the people who love the 1.9L format, but shy away from it because glass isn’t welcome in all environments,” said King. “The craft brewing industry is about innovation and about trying new things so we’re proud to be on the cutting edge by offering PET growlers.”

W. Amsler sees strong opportunities in glass conversion applications where barrier PET bottles have a strong fit due to their light weight and portability. The amber PET container is manufactured by W. Amsler at its Bolton, Ontario, facility on behalf of JMS International Packaging on a W. Amsler all-electric, single-cavity linear series stretch blow molder. The PET barrier container weighs 106 grams versus 1.2 kg for the glass version, thus resulting in reduced shipping costs. It is also event-friendly, unbreakable, and 100% recyclable, according to the company.

A growler is a jug commonly sold at breweries and brewpubs as a means to sell take-out craft beer. The significant growth of craft breweries and the growing popularity of home brewing have also led to an emerging market for the sale of growlers.

“We’ve set a new benchmark in terms of shelf life and provided craft brewers a highly viable alternative to the standard glass container,” said Amsler. Unbreakable and portable PET growlers provide an entry into venues that do not allow glass because of the potential for breakage and other security requirements.

The 64-oz, 106-gram container was designed by W. Amsler with standard preforms supplied by Preform Solutions Inc., Sioux Falls, S.D. It incorporates a barrier with a monolayer structure which includes a Sherwin Williams’ barrier additive. The barrier prevents oxygen ingress and egress and loss of CO2, thus providing up to a 12-month shelf life versus 48 hrs for standard PET growlers. This monolayer barrier solution is compatible with existing recycling streams. The high-density polypropylene (PP) handle, designed by JMS International Packaging, is produced separately and attached to the container via a secondary process. The PET container can accept the same steel or plastic recloseable caps that are found on the glass growlers today.

The PET growlers are also available in clear color with or without barrier protection for ciders, craft sodas, craft cocktails, and liquor. Custom growlers can be produced in different shapes, colors, and engraving. Pressure-sensitive labels can be applied and a screen printing process can also be used. W. Amsler offers PET growlers in small batch (pallet or less) availability to meet craft brewer needs.

About Arch Brewing

Arch Brewing, a craft brewery based in Newmarket, Ontario, specializes in small-batch, high- quality beers. The company offers a cozy space for its customers and challenges itself to find ways to keep getting better. The brewery is in a constant state of innovation, delivering the latest in terms of products and services for its clientele. Arch Brewing serves beer directly to the public through their brewery storefront as well as the LCBO and Beer Store. Arch Brewing is a unique space to come visit, have a pint, and be present where it is brewed. For more information, visit www.archbrewing.ca.

About JMS International Packaging Inc.

JMS International Packaging, based in Sherbrooke, Quebec, specializes in design, manufacturing and delivery of complete packaging solutions. Through a combination of 30 years of plastic knowledge, JMS International Packaging specializes in the production of high-quality packaging materials. Through the years, the company has evolved into a multi-product and multi-service business which provides customers with an endless variety of packaging possibilities.

The company’s product line is diversified and responsive to the needs of the entire food market. JMS International creates innovative products through established and proven technology and advanced R&D. The new patented plastic PETB1 offers the best performing air index on the market. It’s a unique material that protects a product from UV rays and offers transparent or opaque options. The product resists impact and ensures a certain economy compared to glass. The formula has enabled JMS to obtain a recycle code 1. It has strong resistance to hot filling and is much lighter than glass. For more information, visit www.jmsintpackaging.com.

About W. Amsler Equipment Inc.

W. Amsler Equipment Inc. is the only North American manufacturer of all-electric linear PET stretch blow molders, 100% designed and built in North America. W. Amsler is a privately-held Canadian company founded in 1994 by Werner Amsler. In addition to PET stretch blow molding machines, Amsler provides bottle design, preform sourcing, preform design and pilot production run services. Amsler Equipment can also supply equipment for complete blow molding plants and filling lines. These products include bottle inspection units, blow-dome spin-off trimmers, air compressors, vacuum conveyors, blow molds, gaylord dumpers, mold temperature control units, and process chillers. For more information, visit www.amslerequipment.net.

Press Contact:
Joseph Grande
J. Grande communications Inc.
413.684.2463
joe@jgrandecommunications.com