cap sealing

The Poor Man’s Tamper Evident Seal – Pressure Sensitive Cap Sealing

Tamper Evident Seal

When looking into whether to use a pressure sensitive tamper evident seal or an induction seal it is a good idea to understand the core reasons behind applying tamper evident seals and induction seals to bottles and jars.

For induction sealing the key benefits from that type of seal include:

A visual tamper proof barrier showing the client the contents of this product have not been compromised.
An oxygen and moisture barrier, preserving the integrity and shelf life of products. For this reason alone induction seals are often referred to as freshness seals.
Eliminate leaks through caps. Often plastic caps are well tightened after their bottle has been filled, however temperature changes resulting in slight cap expansion and contraction and the vibration of transport result in caps loosening and product leaking, Eg. Often compromising significant portions of product shipment that become very difficult to retail if not impossible.
To provide a professional finish to the product showing the manufacturer cares about the above three major benefits of good product sealing.

For pressure sensitive sealing – sometimes called PS22 Wadding the key benefits from that type of seal are reduced:

A visual tamper evident barrier showing the client the contents of this product have probably not been compromised
To provide a professional finish that resembles the level of care used by manufacturers using induction sealing.

Pressure sensitive wadding is susceptible to someone that can come along and carefully peel such a liner partially off the neck of a bottle and then simply tighten the cap again to apply pressure and re-seal the bottle; no equipment or tools is required. In this way bottle sealing with pressure sensitive cap sealing is more visual than practical.

Pressure sensitive cap lining material usually has no foil barrier and therefore has little to no barrier properties to lengthen shelf life or preserve freshness. Being glue based, many liquid contents are not suitable for pressure sensitive or PS22 cap sealing.

So why do companies choose pressure sensitive sealing materials over induction foil sealing?

In some cases it is ignorance of the induction sealing process and in other cases it is the “poor man’s” version of a tamper evident seal.

Induction sealing tamper evidence requires induction sealing machinery. Pressure sensitive sealing requires no machinery.

Safe bench top induction machinery can start at USD$3500.00. Beware there are many hand held induction machines on offer for sub USD$1000 and manufacturers of that level of equipment refuse to provide safety certifications or advise that they do not “yet” have the certification.

An induction machine is not like a toaster or a kettle so beware of anyone offering toaster or kettle prices for induction sealing equipment. An induction machine deals with high currents and produces high levels of magnetic and electrical fields.

If you find a retail product on the shelf with a pressure sensitive seal be aware that while it looks like it is tamper proof it is at best only ‘tamper evident’. The company producing that product is taking the cheapest path to providing you with a look that resembles but in no way performs like an induction seal or a tamper proof seal.

Induction Sealing Bottles with Specialty Caps

Induction Sealing

A Tunnel Induction Sealing Head lets you seal caps where the foil sits a distance greater than say 4 mm from the top surface of the cap; This is often the case with twist top spouts, flip top lids, sports drink caps, sipper caps or shaker caps.

Induction sealing is a process where a coil in the shape of an elongated loop is used to generate a fast oscillating high magnetic field. This magnetic field can change poles as many as 100,000 times every second.

The magnetic field can travel through air and plastic. When the magnetic field meets a metal surface, the magnetic field “induces” a high oscillating current in that metal surface in a plane that is parallel to the coils that generated the magnetic field.

A magnetic field generated from a “point” dissipates with the cube of its distance from that point.

In general, the magnetic field of an induction sealing machine needs to be within 5mm or ¼ inch from the sealing foil to obtain meaningful production speeds.

There are a large range of caps that do not fit the standard flat top profile and present a problem to bring the magnetic field of the heat sealing equipment to within 5mm or ¼ inch from the sealing foil.

These specialty caps need an adaption from a standard flat coil sealing head to a tunnel sealing head. The Coils are shaped to pass around the tunnel. The tunnel allows the protruding feature of the specialty caps to pass through the machine without lifting the plane of the magnetic field further away from the sealing foil within the bottle cap.

On the SealerOn website there is a youtube icon that will link you to videos showing SealerOn™ heat sealing or more accurately induction heat sealing using a tunnel sealing head.

The SealerOn™500 fitted with a sealing tunnel is capable of sealing at sealing speed up to 10 Meters per Minutes or 30 Feet per Minute depending on the cap and foil combination.

For faster induction sealing there is the MeRo adjustable tunnel sealing machines. These machines have the added and unique feature of having an adjustable width sealing head. Having an adjustable width enables higher concentrating and focussing of the induction field allowing for higher speed sealing. A MeRo 2Kw unit is capable of sealing at sealing speed up to 30 Meters per Minutes or 90 Feet per Minute depending on the cap and foil combination.

Efficient cap sealing means that less time is needed under the sealing head and hence higher production speed is possible.

A Flat profile sealing head will allow for a greater range of cap sizes and even allows for that Sealing head to be placed at an angle across the product’s path to achieve sealing of cap diameters that are even wider than the coil winding pattern within the sealing head. It is quite possible to have a Flat profile sealing head that can seal caps from 30mm to 110mm wide. The trade-off for the versatility of this profile sealing head on a heat sealing head is lower speed throughput and an inability to seal specialty caps.

What Shape Sealing Head is Best on an Induction Sealers?

Induction Sealers

To understand this question of the sealing head shape we must first understand how an induction seal is achieved.

The sealing head is the part of the machine that is placed over the path of the product cap/lid. Within the sealing head is usually long oval shaped coils of thick wire that carry high current that changes direction many thousands of times a second. This creates a magnetic field at right angles to the coil that also changes direction many thousands of times a second. The magnetic field can travel through air and plastic but it does get weaker as it travels away from the coils that generated the magnetic field. When the magnetic field comes across metal, it will act to generate current in the metal.

In the case of the heat sealing machine, it waits for a product that has a metal laminated foil in its cap. The magnetic field from the sealing head acts to generate current in the laminated foil and the laminated foil gets hot. Laminated to the foil is a layer that will melt or become “wet” with heat. When the product has completely passed from under the induction machine the foil will begin to cool and the layer that became “wet” will set to bond the laminated foil across the opening of the product.

From the above “theory” it can be understood that the sealing of a bottle or product using induction machines will depend on how long the product is under the magnetic field and how close it gets to that origins of the magnetic field.

There are two distinct shapes of sealing heads for cap sealers being Flat profile and Tunnel profile sealing heads.

The Flat profile sealing head is suitable for “Standard Flat Caps” . A “Flat Cap”, generally speaking, refers to a cap where the plane of the induction liner is within 4.0 mm of the plane of the Cap’s top surface.

The Tunnel profile sealing head is suitable for “Specialty Caps”. A Tunnel Induction Sealing Head lets you seal caps where the foil sits a distance greater than say 4 mm from the top surface of the cap; this is often the case with twist top spouts, flip top lids, sports drink caps, sipper caps or shaker caps.

The Tunnel sealing head concentrates the magnetic field to an area within the tunnel profile and hence provides stronger magnetic fields over a generally smaller width path for the products passing underneath. A Tunnel sealing head also allows the coils within the sealing head to have a path lower than the top of the product caps. This brings the magnetic field closer to the plane of the foil within “specialty caps”. The drawback to this Tunnel profile sealing head is that it is usually not very good for large caps and it does limit the range of cap sizes that can be efficiently sealed. There is a small exception to this rule with the MeRo™ brand induction sealer with an adjustable width tunnel profile. This machine can typically cater for a range of specialty caps with an adjustment of 30mm which would mean a typical cap diameter range of 30mm to 60mm could be very efficiently sealed.

Efficient cap sealing means that less time is needed under the sealing head and hence higher production speed is possible.

MeRo Flat Caps

Flat Caps

With Induction sealing it is important to identify if your range of plastic caps is considered “Flat Caps” or specialty caps.

A “Flat Cap”, generally speaking, refers to a cap where the plane of the induction liner is within 4.0 mm of the plane of the Cap’s top surface.

See the picture below:

With only Flat Caps, a Flat Sealing Head can be provided.
With A Flat Sealing Head it is possible to cater for a wide range of cap sizes.

The energy transfer for a Flat Sealing Head is not as efficient as a Tunnel sealing head but the versatility often makes up for the reduced speed throughput compromise of a Flat Sealing Head

Mero Flat Caps

MeRo Sealer Machine Introduction

MeRo Induction Sealer Machine Range

We believe there is no better value medium priced “High End” Induction Sealing Equipment. There are unique features to allow process validation and adjustable width sealing head tunnels are available.

MeRo Induction Sealer Machines feature:

An Air cooled system (Absolutely no need to water cool the induction head).
Compact construction for easy integration into the filling line.
High power efficiency thanks to the configuration of the power circuits and the use of IGBT modules.
Sinusoidal output waveform (Not Square or chopped).
Constant and Precise Output power due to the configuration of the regulation circuits.
Easy to use controls that display operating parameters and alarm signals.
Remote control Start-Stop interface.
Power variation monitor which can be set by the user to activate an alarm.
Manufactured in accordance with EN-60204-1 standards, Electromagnetic (EMC) compatibility in accordance with EN-5511 and EN50082-2 standards.
Motorized height adjustment
Set-Up Validation providing an Energy absorbed reading- A key advantage over Nearly Every other make

Depending on the range of product and cap, lid, closure shapes, different sealing heads can be supplied.

Options include:

Missing Foil Detection with Bottle Eject Mechanism or Signal
Bottle Accumulation Detection to avoid the situation where bottles are stalled under the active sealing head.
Pressurized Cabinet version to work in dangerous areas.
Fieldbus connection to the production process ASI/PROFIBUS/CAM OPEN/DEVICE NET
Integration of power regulation proportional to the speed of the conveyor via feedback from your existing conveyor’s speed controller. This is another key advantage that MeRo are able to offer over nearly other make.

Take a Closer Look

SealerOn™ Induction Machines – Take a Closer Look

What is Induction Sealing?

Induction sealing is a common packaging process to bond a foil seal across the opening of container, jar or bottle. Usually, the foil seal is placed into the cap or closure of the product to be sealed and then the cap or closure is placed over the filled product. The product then passes beneath an induction sealing machine and without ever touching the product the machine bonds the foil to the opening of the product.

How Induction Sealing Takes Place?

As soon as the container has been filled and capped – with a closure fitted with an induction liner – it travels beneath the induction sealing system. The non-contact heating system welds the liner to the container resulting in an air-tight and water-tight seal. Induction sealing machines or sealers, sometimes referred to as heat sealers, facilitate a product seal by emitting a high energy concentrated electromagnetic field. This field is created using high current thick windings (coils of wire), with voltage and current that switches back and forth at many thousands of times per second. The electromagnetic field passes through the air and the plastic of the containers cap to reach the Aluminum of the Induction Liner. The field then generates high frequency alternating currents on the surface of the foil which causes the foil to heat up.

Bonded to the Aluminum is a heat seal layer – usually a polymer layer that will melt with heat. When this heat sealing layer melts its bonds with the top surface opening of the container and as it cools it “sets” in place with the neck or rim of the container. The Food and Drug Administration regards induction sealing as a highly effective method of tamper evidence.

The SealerOn™ SealerOn400. This has been the Flagship of the SealerOn™ range and is being replaced by the SealerOn™ SealerOn500.

SealerOn™100 Induction Sealing Machine - Affordable Entry Level Induction Machine

SealerOn™ 3000 The SealerOn™ 3000 is typically rated for Flat Caps of Diameter 20 mm to 120 mm traveling on a conveyor at speeds up to 20 Meters (60 Ft) per minute.