Improve Trapped Key Interlocking Processes with Upgrade to Medium or Heavy Duty Designs

September 10, 2014

Kirk Key MD and HD Series locks withstand harsh environments and handling for long service life


North Canton, Ohio (September 10, 2014) – Kirk Key’s trapped key interlock systems ensure a pre-determined safety sequence is followed each time hazardous equipment is accessed or operated. Over the past 80 years, its Standard Duty (SD) brass interlocks have earned a reputation for dependable service in a range in applications. To meet the needs of more challenging environments, Kirk now offers Medium Duty (MD) and Heavy Duty (HD) Series options. Constructed to withstand exposure to extremes in temperature, weather, dirt, and corrosive elements, the MD and HD Series deliver long, reliable operation.


The construction of both the MD and HD Series interlocks use 316 stainless steel cylinders, keys, bolts, and inner-workings that withstand high temperatures and corrosives in outdoor or harsh environments. The cylinder mechanism has no openings and few moving parts. The shaft driven design prevents dirt and debris from clogging the mechanism. Gasketed keys and dust covers on the interlocks further protect the cylinder from debris.


The HD Series is constructed completely of 316 stainless steel, including the lock body. Ideally suited for chemical applications, passivating electropolishing further protects HD Series interlocks from chemical activity. The MD Series interlocks are constructed with a brass lock body protecting the inner-workings.


The 316 stainless steel dowel pin key design used in the MD and HD series is stronger than typical pin tumbler keys to resist breakage and damage. The dowel pin design cannot be duplicated or altered to create a master key. Its distinctive shape is less likely to be misplaced or slip through standard floor gratings, minimizing the incidence of lost keys.


MD Series and HD Series ranges include mechanical and electromechanical bolt, access, transfer and valve interlocks, along with a full range of accessories to form a comprehensive interlocking scheme.


To learn more about upgrading an existing system or designing a new interlocking scheme, contact a Kirk technical sales engineer at, or call +1 234 209 9301. See the full range of products at 




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