Security seals can help to detect theft or contamination, either accidental or deliberate. Typically they are considered an inexpensive way of providing tamper evidence of intrusion into sensitive spaces. They also provide some level of security. The level of security depends on the material used and the design of the seal.
Applications include sealing of containers, valves, gates, doors, meters, trolleys, tankers, drums, keys, vehicles, cages, boxes, bags, sacks, hazardous waste, legal evidence, fire extinguishers. A slightly different application is when seals are used for asset tagging.
Seals are either single use or re-useable. Re-useable seals are generally made of stronger material and are more expensive. They are generally used in the logistics industry. Single use seals are more commonly used.
The most common types of metal seals are bolt seals, ball seals, cable seals and tin clip seals. Bolt seals are used to secure shipping containers, trucks and trailers. Balls seals are used for securing trucks. Cable seals are more versatile and come in different lengths. Tin seals are used in conjunction with sealing wire. They are versatile and easy to use. Metal seals usually have a higher level of security.
The most common types of plastic seals are variable length seals, fixed length seals, padlock seals, meter seals and special adhesive tapes/labels. They commonly made from polypropolene or nylon, some may also have internal metal locking parts.
Variable length seals, commonly called “pull tight seals” can fit many applications from securing the neck of a bag or mail sack to sealing chemical drums, first aid kits and fire extinguishers. They have an adjustable length much like a cable tie but offer a much higher security level and an audit trail.
Fixed-length seals tend to be more tamper resistant than variable length as there are no sliding parts, they simply ‘click’ into place to lock, which can make them easier to fit than variable length seals.
Padlock seals are usually supplied as a completely plastic seal, shaped as a standard padlock would be. Technically, they can be classed as a fixed length seal. The most common use for these seals is for airline duty-free trolleys. One reason for this is that plastic padlocks can be placed over a locking part as any metal padlock would be to secure, but do not require keys to open, they simply break off at their built in break point using hands or a small pair of wire cutters.
Meter seals are used with electric or gas or water meters and usually molded in polycarbonate. The transparent body of the seal means that the locking mechanism is visible, and can provide clear indication of tampering. Meter seals can withstand exposure to sunlight and extreme weather, and a wide range of temperatures. Designed for only a single use, they are destroyed when removed. Some meter seals contain components which glow under ultraviolet light, allowing the seal to be easily located in darkness.
Special adhesive tapes and labels have high bond-strength adhesives in combination with backing that are designed to fracture or delaminate under designated conditions to indicate premature attempts at opening.
The seals can be individualized to fit the needs of the user. Typical marking includes branding, barcoding and consecutive numbering. This is important because it provides tamper evidence and an audit trail. There are several technologies in use, including hot stamping, ink jet printing, laser engraving and thermal printing.
The effectiveness of seals is strongly dependent on the proper protocols for using them. These protocols are the official and unofficial procedures used for seal procurement, storage, record keeping, installation, inspection, removal, disposal, reporting, interpreting findings, and training. With a good protocol, a modest seal can provide excellent security. On the other hand, a sophisticated seal used poorly may be worse than useless if naively trusted.