Leaky Seals... Sorted

Simon Wilson highlights the main causes of leaky seals that he comes across in his day-to-day job as seal technologist for tray sealing machinery specialist Packaging Automation, and suggests solutions to these problem scenarios.

Problem 1 - Contaminated Seals
Most ready meal and convenience food operations tend to rely heavily on manual intervention to weigh and deposit the constitutent parts. This often results in oil or grease getting onto the seal area. Wiping the seal area can be counter-productive, spreading the contamination, whilst alcohol-based wipes can leave moisture on the tray edge, making sealing difficult.

The Solution: the use of tray edge covers or ‘templates’ helps to prevent contamination during tray filling. Sealing issues as a result of residues from wipes can usually be eradicated by adjusting the machine settings; trials with ‘wiped’ trays will establish the optimum parameters.

Problem 2 - Damaged Seal Rubber
If the seal rubber is damaged or there are gaps in it, there will be no support underneath the tray, making it difficult to achieve an even seal all the way round the tray.

The Solution: in-house maintenance. Replacing the strip or seal rubber is a fairly quick and easy task to perform and seal rubber should be held as a spare. Damage to seal rubber often arises as a result of damage to the base tool - we offer training to our customers on how to maintain and look after heat sealing tooling as well as encouraging them to use racks for storing tools.

Problem 3 - Contaminated Seal Profile
A seal profile is a heated plate in the top tool, when the tool comes together it heats the film when compressing against tray flange to form a seal. If the seal profile isn’t clean it will prevent the sealing system from applying heat evenly, causing leaky seals.

The Solution: regular cleaning of the seal profile, as well as after spillages.

Problem 4 - Weak Seal Force
If two or three sealing springs break, the machine won’t achieve the seal force it needs to create a strong seal.

The Solution: regular checks that the sealing springs are intact. Packaging Automation has designed a quick release blade that checks whether the seal springs are in good condition.

Problem 5 - Hot Product Causing Film Creep
When sealing a tray containing a very hot product, ‘doming’ of the film can occur, causing the film to creep away from the tray edges before the seal has had time to ‘cure’.

The Solution: insert pads can be placed inside the seal profile to push the air out, diffusing the build up of internal pressure within the pack to ensure a tight seal.

Problem 6 - Incorrect Settings
With the correct machine setting tray sealers operate perfectly but over time, sealing performance can be reduced because operators have taken it upon themselves to change the original settings. The quality of a seal is a finely balanced combination of sealing time, pressure and temperature, so if any of these parameters are slightly out, it will compromise seal integrity.

The Solution: introduce a system that allows various levels of operator access to different features of the machine. Packaging Automation have an RFID key fob system which improves efficiency, and increases accuracy by preventing unauthorised changes to the functions of the machine and restricts operator user access to appropriate levels within the HMI screen giving full visibility of accurate real-time information.

Original content written by Lynda Searby Packaging News.


Packaging Automation Ltd was established in 1963 and is a leading UK manufacturer of tray sealing machinery and pot filling and sealing machinery.
PA can offer customers a tray sealing machine or pot filling and sealing machine for a wide range of applications in the food industry including fresh produce packing such as salad, tomato, strawberry, raspberry and soft fruit packing, fish, seafood, meat and chicken packing (including vacuum packing and skin packing), ready meal sealing and packing, and pot or tub denesting, filling and sealing for puddings and sauces.

Full packing lines can be specified and installed to include tray denesting, conveyoring, tray filling, film sealing including modified atmosphere packing (MAP) facilities. Foil tray sealing as well as plastic tray sealing can be accommodated on all machines as standard.
For further information please contact:
Packaging Automation Ltd
Claire Carless
Marketing Assistant
Samantha Ashton
Commercial Director
Packaging Automation Ltd
Parkgate Industrial Park
WA16 8XW
01565 755000