Interlocking Safety devices

The manufacturing facility is planning a major expansion in six months during the slow production season for its cyclical product, at which time it will be replacing an aging production line with completely new equipment. The annual safety audit of the plant recommends the installation of emergency shutdown interlocks—safety devices that automatically shut down the system when triggered by an out-of-bounds condition or an... 

Duplex filters are designed for use where an uninterrupted fuel flow is required, or where an immediate standby filter is essential. Fuel oil filters can generally incorporate air vents, drains and tappings for pressure differential instruments. Steam jackets, magnetic elements and interlocking safety devices may also be fitted. Fuel oil cartridges for this type of filter are fitted with media capable of operating up to 160°C, with a 4 am nominal filtration efficiency, and can withstand a 10 bar pressure differential. 

Does the facility have a program for regular inspection and testing of process safety valves and other process safety devices including interlocks ... 

Safety interlock A safety device designed to ensure that equipment will not operate until certain precautions are taken and set on the equipment. 

Formal and systematic inspections of key equipment, safety devices, and safety interlocks. 

Bypassing safety devices. No individual shall bypass a safety device or interlock unless the individual has obtained written approval of the radiation safety officer. 

Safety interlock — A device required to ensure safe start-up and safe operation, and to cause safe equipment shutdown. 

Safety and environmental reviews would probably recommend the installation of a high-level alarm and/or an interlock (a device to shut off the feed if the level gets too high) to guarantee that the tank could never overfill. The tragic accidents at Three Mile Island, Chernobyl, and Bhopal illustrate the need for well-designed and well-instrumented plants. 

Interlocks are commonly used safety devices. The function of an interlock is to prevent the occurrence of an event in the piesraice of certain conditions. Some interlocks prevent action or motion, others send signals to other devices that prevent the action or motion. They automatically reconfigure or interrupt final control devices if monitored variables deviate significantly from specifications. Typical process variables monitored are flow, pressure, level, and temperature. Typical machine variables monitored are coolant level and temperature, lubricant level and temperature, vibration, speed, etc. Interlocks allow equipment to start and operate only when monitored variables are within designed specifications. Interlocks inhibit unanticipated actuation of equipment and ensure correct startup/shutdown sequences are followed. A permissive interlock will not allow a process or equipment to startup unless certain conditions are met. There ate two types of interlocks—safety and process interlocks. Each serves a different function. 

Incorporate safety devices (fixed guards, interlocks). 

HAZID will thus create awareness at the design stage itself and can suggest need for suitable changes in the process design, modifications in equipment designs, and provision of additional safety devices as well as interlocks before the final designs are made. Any serious hazards identified must be addressed suitably to prevent... 

All necessary safety devices (safety valves and mpture discs), automatic activation of safety systems if any dangerous condition develops, and safety interlocks are confirmed to be in working order. There shall be no chance of any tampering of the safety systems. 

Are all safety devices functioning correctly, e.g. emergency stops, interlocks ... 

Energizing power systems, operational testing of plant equipment, calibration of instrumentation, testing of the control systems, and verification of the operation of all interlocks and other safety devices, without yet introducing process materials. These activities are usually described as cold commissioning . In parallel, it is usually necessary to commission the plant utilities, such as cooling water and compressed air systems, in order to enable equipment operation. 

All safety devices and safety interlocks pertaining to a plant item should be made operational, calibrated, and proved before starting it. If this is not fully possible, say in the case of a turbine overspeed trip, then proving the device under controlled no-load conditions should be the first operation after starting. A witnessed checklist should be utilized for recording the proof of safety device and interlock operation. 

Machine guards are examples of safety devices. They prevent operators from getting into a hazardous area of a machine. Fences, interlocks, shielding, and enclosures are all forms of safety devices. 

For hazards that cannot be eliminated, consideration is to be given to safety devices that will minimize mishap risk (e.g., interlocks, redundancy, fail safe design, system protection, fire suppression, and protective measures such as clothing, equipment, devices, and procedures). 

The choice of interlocking method will depend on power supply and drive arrangement to the machine, the degree of the risk being protected against and the consequences of failure of the safety device. The system chosen should be as direct and as simple as possible. Complex systems can be potentially unreliable, have unforeseen fail-to-danger elements and are often difficult to understand, inspect and maintain. 

Is there verification that the equipment does not re-start, either on the re-setting of a protective device such as an interlock (safety non-safety), or the re-establishment of power after an outage ... 

Plastic injection molding machines are very common in many manufacturing plants around the world. Occasionally, the technician needs to reach inside the machine to clear out debris. Many hands and arms have been lost from trying to clean the debris while the machine was still powered on (though not running). An electrical interlock that automatically disconnects the power source when the inside envelope of the machine has been violated is another example of a safety device. 

---