Ethylene production is an inherently complex and dangerous process, particularly when considering the operation of valves and/or line blinds around a cracking furnace. The incorrect operation of the controls to gas, feed stock and decoke air to the furnace can have catastrophic results. Under normal conditions, the operation of controls is carried out manually using valves and/or the swinging of line blinds or elbows (spool pieces) to control the gas inlet and decoke air inlet. This process is time consuming and can lead to extended downtime. The probability of accident and injury can be high if procedures are incorrectly carried out. To counteract this, valve interlocks can be mounted directly onto valves and equipment. They can be supplied to suit any make, model or type of valve, either manual or actuated and will ensure that valves are operated in the correct fashion.