Types of Safe Locks

The most common types of safe locks on the market are mechanical combination locks, these are mostly based on design principles refined over centuries. More recently electronic and electro-mechanical combination locks have become available and offer a variety of advanced features. Today almost all types of safe lock use a standard form factor and mounting so that any modern safe can be easily fitted with the lock of your choice regardless of the manufacturer or technology of the lock.

Given the array of options it is necessary to determine your customer’s needs when deciding on the type of lock you want before considering specific models or security ratings. Mechanical combination locks can be slow to dial and require a degree of precision, electronic locks typically use keypads with push buttons which can allow rapid and accurate entering of combinations even for a person with limited dexterity.

Mechanical combination locks are very reliable requiring only occasional lubrication for decades of use, electronic locks on the other hand will require replacement batteries (at least once per year on average) in addition to mechanical maintenance. Mechanical safe locks typically can only be set to accept a single combination which must be shared with anyone else requiring access to the safe. Modern electronic safe locks can often be set to accept multiple unique access codes so that each user of the safe can have their own unique code as well as offering options such as anti-tamper alarms and ‘duress codes’ that can alert an alarm monitoring center. Consider these factors when deciding on what type of lock to use or recommend.

Some insurance policies (particularly in Europe) will set requirements for safe locks based on the value of the safe’s contents while government agencies and contractors handling sensitive documents and materials will often be required to use containers and locks that meet specifications issued by the government (in the US Federal Specification FF-L-2740B is the most commonly encountered). When recommending a product to a customer it is important to get these details at the outset as they will narrow the options significantly.

Mechanical Safe Lock Ratings

In the United States the most commonly used rating system for mechanical combination locks used on safes is Underwriters Laboratories’ UL 768 standard. UL 768 lays out four possible ratings for combination locks, known as Groups. In order from lowest to highest the ratings are: Group 2, Group 2M, Group 1, and Group 1R. In order to attain any rating under UL 768 a combination lock must meet certain minimum criteria regarding the design of the mechanism and provide at least 1,000,000 (one million) unique combinations.  In Europe the most common standards are EN1300 and VdS certification, while these standards are not directly interchangeable, VdS Class 2 or EN 1300 Class B locks are essentially equivalent to UL 768 Group 2 or 2M locks. For potential buyers in Europe it is highly recommended to consult with your insurance provider on their requirements for both secure container and lock ratings.

Group 2

The minimum possible rating. These locks meet the basic requirements for build tolerances, durability, and accuracy. The combination wheel must be accurate to one and a half of a digit or less when the combination is entered. Group 2 combination locks are considered to have “a moderate degree of resistance” to opening by unauthorized people. These locks are usually sufficient to prevent accidental opening of a safe or opening by a person with little to no knowledge of safe manipulation techniques. These locks are common for B and C rated safes but should not be used on higher rated containers.

Group 2M

Group 2M is a relatively recent addition to the UL 768 standard and indicates a slightly higher level of security against manipulation than the basic Group 2 designs. Group 2M locks are supposed to provide up to two hours of resistance to expert attempts at manipulation. These are the most commonly used locks for higher rated safes and containers such as TL-15 and TL-30 rated safes.

Group 1

Group 1 locks offer the highest level of manipulation resistance available to most civilian buyers and are often required for sensitive government applications. These locks offer up to 20 hours of resistance to manipulation by a single expert. The dial must be mechanically accurate to within 1.25 digits of the correct number on a three digit lock or 1.5 digits on a four digit lock. Group 1 locks must also have features to immobilize the bolt if the lock case is compromised or the spindle is punched out. Group 1 locks are suggested for TL-30×6 or TRTL-30 rated safes and up.

Group 1R

The rarest of the UL 768 ratings, Group 1R locks must meet all the requirements of Group 1 ratings but also resist up to 20 hours of manipulation or decoding using X-ray or similar radiological imaging techniques. These locks may use shielding (such as lead) to prevent x-ray penetration or they may employ x-ray transparent materials such as certain types of plastic to prevent x-ray imaging.

Surprisingly, in most cases there is not a significant price difference between the classes of mechanical safe locks. With this in mind the primary considerations affecting the selection of lock for a safe will be the rating of the container and requirements set by insurance policies or government regulations. Group 2 locks are adequate for most fire safes and Residential Security Containers to maintain their ratings, while Group 2M is the minimum required for low end burglary-resistant safes (TL-15 and TL-30) or ATM safes to maintain their ratings. High security safes must use Group 1 or 1R locks to retain their attack resistance ratings. Additionally most governments will require containers used to store sensitive materials or firearms to be secured with a lock meeting a certain minimum rating.

UL 768 and GSA Approved Containers

US Government agencies and contractors storing classified materials or weapons and ammunition are required to use GSA Approved containers (safes and cabinets) fitted with locks which exceed even the highest grade of UL 768 certification. These locks must meet the requirements of Federal Specification FF-L-2740B (locks for protection of classified materials), FF-L-2937 (mechanical combination locks for protection of weapons and ammunition), or FF-L-2890B (pedestrian door locks for secure rooms and SCIFs). Certification of locks under those standards is administered by the General Services Administration (GSA) in cooperation with the Department of Defense Lock Program. Purchase of locks certified under FF-L-2740B and FF-L-2890B is restricted to the Federal Government, US Government contractors, and organizations or people specifically authorized by the US Government.

Electronic Safe Lock Ratings

In the United States UL 2058 is the primary standard for electronic safe locks. Locks which are certified to meet the criteria of UL 2058 are often listed as “UL Type 1“. Like mechanical locks, electronic locks are required to offer a minimum of 1,000,000 (one million) possible combinations however there are several unique requirements for electronic locks. To aid reliability and prevent accidental lock outs batteries must be stored in the keypad on the outside of the door so that they can be replaced even when the container is locked and combinations must be stored in non-volatile memory so that codes will not be lost when the lock loses power. To prevent decoding or manipulation of the lock all storage, and processing of combinations must occur in electronics located on the secure side of the door (ie inside the container).

UL 2058 also lays out a variety of durability requirements intended to ensure the lock will continue to function even with a certain amount of rough handling or in less than ideal environments. Unlike UL 768’s multiple grades, UL 2058 currently only offers the one grade which makes it essentially a pass/fail system. Using an electronic lock that is not rated as UL Type 1 is not recommended on any burglary rated safe.

2018-10-18T08:04:47+00:00 October 18th, 2018|All, Combination Safe Locks, Safe and Vault|

About the Author:

I am a security researcher and licensed locksmith working in New York, NY, USA.

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