Interlock, interlocking devices

The assessor should also find out whether an effective testing program is in place to help ensure the serviceability of process measurement equipment. The successful toller should have an established calibration program to address the accuracy of critical measurement equipment. Safety critical process parameters should be monitored and critical process equipment should automatically interlock when monitoring instrumentation detects safety critical deviations. Interlocks should either facilitate a remedy to the critical deviation or bring the process to the zero energy state. These instruments and interlocking devices should be routinely tested to ensure operational reliability. 

Vent and purge lines Procedure to indicate how to check if fully purged Ensure training covers symptoms of pressure in line Line pressure indicator at controls. Interlock device on line pressure. 

High voltage equipment (e.g. for use in electrophoresis, or in the generation of ozone) requires special precautions. Ideally, such apparatus should be isolated within an enclosure equipped with an interlocking device so that access is possible only when the current is switched off. 

Total enclosure is represented by fixed covers over the pulleys, gears, shafts, and couplings to prevent access to the hazardous area. They can also be coupled with interlock devices for shutting down the machine if a portion or the whole cover is removed. 

The hazards associated with inappropriate use of microwave equipment cannot be entirely prevented by interlocking devices and other safeguards. However, the risk can be minimized if the analyst continually inspects the system to ensure that the equipment is maintained in safe working order. If any portion of the microwave unit such as door seal or vessel casing becomes damaged by a serious event such as an acid spill, prolonged wear or impact, the safety of the equipment should be re-assessed before it is returned to service. 

A High Furnace Temperature Interlock is required by NFPA 86 (sect. 5-16) whenever it is possible for the controlled temperature to exceed a safe limit. The high-temperature interlock device and associated equipment including thermocouple must be independent of the equipment used to control the temperature of the furnace. The high furnace temperature interlock is considered a critical safety interlock. 

The transfer of materials into and out of the controlled workspace is a critical factor of the isolator s operation. The transfer device separates the background environment from the Grade A controlled workspace. It should be designed such that it does not compromise the Grade A controlled environment. To this end an interlocked device will provide greater security. The size of the transfer device should be sufficient to allow all necessary materials and equipment to be passed through. 

This first critical phase may initiate the most permanent alteration of the artifact s tissue, as its field often involves the microstructure of the wood cell. Attachment through adhesive bonding tends to engage the most widespread interaction with the intrinsic tissue. Mechanical interlocking devices, such as threaded rods and pins held in place by friction, function by crushing the substrate to increase its solidity. 

Safety Interlocking Devices Control and Indication Devices... 

Most switchboards and motor control centres are fitted with a variety of electrical and mechanical safety interlocking devices. Their purposes are to protect against for example -... 

Various external attachments can be fitted to moulded case circuit breakers, e.g. pad-locking tabs, shunt trip coils, hazardous area enclosure with an on and off operating handle, withdrawable rack mountings, undervoltage tripping units, auxiliary switches of the normally open and normally closed types, interlocking devices, ambient temperature compensation for the protection curves. Some... 

Gauges at plants are frequently out of service [23]. At the Bhopal fadlity, there were few alarms or interlock devices in critical locations that might have warned operators of abnormal conditions—a system design defidenqr. 

Safety of Machinery—Interlocking devices associated with guards Safety of Machinery—Safety related parts of control systems—General principals... 

Reliability and safety of railway signalling and interlocking devices... 

Other control interlocks could include hoist start prevention when embarking at shaft landings by hoist blocking device and shaft gate closed/locked switch, shaft landings gate open interlock device, and lockable hoist start prevention switches used during hoist mechanical maintenance (located in tower and at shaft maintenance locations). 

Shaft landings gate open interlock device 2... 

Example 34-4 A company wants to reduce the hazards of injury in a machine. There are two options that may help installing a guard or using an interlock device. The goal is to compare each approach and express the solution as a return on investment. Table 34-12 compares the two alternatives. 

Flow interlocking devices (required to ensure coolant flow anytime the equipment is energized)... 

When fixed or adjustable guarding is impractical, an interlocked device should be considered. The interlocked guard provides access to the danger area when the moving parts of the machinery come to rest. The guard is required to ... 

Engineering controls are primarily used for protection against microwaves. Typical controls include the enclosure of the whole microwave system in a metal surround and the use of an interlocking device that will not allow the system to operate unless the door is closed. 

In general, OSHA requires that all power sources that can be locked out, must be locked out for servicing or maintenance. Guards or interlock devices cannot be used as substitutes for locks. 

British Standards Institution, BS EN 1088 (ISO 14119), Safety of machinery - Interlocking devices associated with guards - Principles for design and selection, BSI, London (1995)... 

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