How Strong Should Your Seals Be?

How Strong Should Your Seals Be?

Posted by Steve Diebold

A common question from security seal users is how strong their seals need to be. The answer is not always simple and can change in some cases.


The question of seal strength reaches into a wide swath of industries, institutions, seal types and uses. We can address the basics here. A seal expert at AC&M can go deeper with you into the options and advantages of the various seal types for your specific needs. See contact information on our web site for where to get help.

We view seals in 2 basic strength groups; indicative seals (for evidence purposes only) or barrier seals that require stronger tools to cut off and are not likely to break if struck or accidentally caught on obstacles in handling.

For barrier seals the options are essentially either cable seals or bolt seals. Within those two general types are numerous options. You need to decide how much strength is required and which type fits.

For indicative seals which are not hard to cut or pull off the question then becomes which type do you need, and then how strong it should be? Most of them fit the majority of applications physically. But the strength varies widely by type.

When you know which type or model of seals will fit, the goal is to find the one in that group that will withstand the conditions you are exposing it to, without high potential for accidental breakage.


High strength does not automatically translate into high security. A poorly made seal, or one that is not used properly cannot be effective regardless of how strong it is. Impressive strength specifications and strength test standards are no substitute for real world testing. If you are unsure, we recommend that you test before choosing. AC&M can supply you with samples for that.

The cost difference for seals is determined by the types and quantity used. Within each type or group the costs do not vary substantially. For example, 8-inch or 16-inch plastic pull up seals generally range from about 30 lbs to 90 lbs of breaking strength. There are a lot of options within that seal category, but the cost does not vary that much for variations within the group of 8-inch plastic pull up seals, except for the difference in quantity pricing.

If you do need a high strength seal, then do not hesitate to use them. High strength steel seals (bolt and cable seals) are a valuable tool to deter theft and withstand rough conditions. They are similar to plastic or wire seals in that there are many options within the category. You can get varying sizes, types and colors to fit your purpose and your budget. You can get them with high security certification to ISO-17712 (H) category or not. If you do not need a seal that is certified high strength under ISO standards, consider buying a lower cost cable seal. All of our cable and bolt seals, including those not requiring ISO certification, are of the highest quality and give you a good barrier to opening and breakage with clear evidence if they are tampered or opened.

We can advise on which might be best for you if we know details of the use. Often it is our suggestion that you test samples to decide which one best fills your needs. We are glad to provide test samples.


When seal type is mandated, the choice of seal is sometimes simple for the buyer, but not always.

Some regulatory authorities and trade organizations have specific requirements for the type of seals used, and the choice becomes much simpler. A good example is international shipping containers travelling under security programs like C-TPAT in the US, BASC in Latin America, or SOLIS which is a worldwide program for security within the International Maritime Organization (IMO). These groups specify the use of seals meeting the standards of ISO-17712 for High strength seals. It means the user will attach a cable or bolt seal certified to comply with that standard to their shipping container. All you have to do is choose a model and color and determine the markings. AC&M offers several options.

Other mandates or requirements come from government agencies. Many only specify a minimum seal strength or general type requirement, but do not give guidance on how strong the seal should be for your purposes. We have a lot of options and offer solutions tailored to your needs.

A good example of a mandate without specifics would be a milk tanker required by industry standards to have a plastic tamper evident seal on all openings while in transit to a processing plant. Many would choose the lowest cost seal meeting the standard. That seal may or may not be strong enough for the conditions, and it may or may not have the quality of material and manufacture that makes it function without failure. If a seal is easily broken by accident or does not work properly then that low cost seal could end up costing more. There are fines, lost time in delayed delivery, or even missed delivery and lost product because it cannot be delivered if a seal is broken or fails to stay locked properly.

AC&M has over 110 years of history as a leader in quality and performance. Our expertise and wide range of options helps the owner of that tanker to know they have the best seal for their needs.


Some seal manufacturers will tell you the strength of their seal materials or its band. This might be shear strength or tensile or bend. This is not useful in knowing the performance to expect from the seal.

The correct test of a seal is the load to break strength of the seal lock. While the material might be strong, the point at which the entire locked assembly comes apart of fails is the important thing to consider. Most seals are made to break at a specific load so that efforts to force a seal open and reclose will result in obvious damage and essentially destruction of the locking parts, to assure the seal cannot be reclosed. Certain seals are made to break by hand for emergency of quick access, which means knowing pull strength is critical.

Whatever specifications may show it is important to know that the seal will do its job in actual use and not all tests can measure that. Performing your own tests may ultimately be the best to know what works for you.


None of these strength factors can override the importance of reliability of the person locking and removing the seal, or the quality of the seal and its reliability in service.

Your supplier also should be reliable. That is why buying direct from our factory is the best choice. AC&M is a world leader in producing a complete range of seals backed by unsurpassed customer service, expert advice, and quality at the highest level.


Our web site has extensive information about available options and more.

And to learn more about which seals give you the right strength and best fit your application we suggest you contact us to talk or chat online with one of our specialists.