Trip mechanisms safety

Measuring While Tripping Wiper Logs 999. Measurements at the Bit 1002. Basic Log Interpretation 1005. Drilling Mechanics 1015. Abnormal Pressure Detection 1036. Drilling Safety,... 

Explosives may be detonated electrically or nonelectrically. A nonelectric firing system will consist of a blasting cap, a length of time (safety) fuse or a firing device attached to the cap, and a means of activating the system match, fuse lighter, delay mechanism, or trip wire. The electric system requires an electric cap which has two wires attached, perhaps additional wire, and a battery or batteries to provide the current which activates the cap. 

Class 1 safety instrumentation loops include alarms and trips on storage tanks containing flammable or toxic liquids, devices to control high temperature and high pressure on exothermic-reaction vessels, and control mechanisms for low-flow, high-temperature fluids on fired heaters. Other Class 1 instruments include alarms that warn of flame failure on fired heaters, and vapor detectors for emergency valve isolation and sprinkler-system activation. All of these alarms, shutdown valves, and other critical instruments are regularly proof-tested to a well-defined schedule. 

Hauptmanns U, Jablonski D (2006) Comparison of the availability of trip systems for reactors with exothermal reactions. In Stamatelatos MG, Blackman HS (eds) Proceedings of the 8th international conference on probabilistic safety assessment and management PSAM 8, New Orleans/USA—14-18. May 2006, American Society of Mechanical Engineers, U.S. 

Arrest of dangerous machine motion resnlting from actuation of an emergency stop switch. The switch may be in the form of a safety switch, bntton, trip cable, or foot bar or other mechanical device used in conjnnction with an emergency stop safety module. Emission Control... 

A typical molding cycle will not start until a number of interlock conditions are satisfied. While the interlock conditions vary with the machine, the machine will not enter semiautomatic or automatic mode in the absence of these interlock conditions. Generally, the gate (operator guard door) must be closed and the gate safety (interlock) switches tripped. In hydraulic machines, the front gate has three switches (electrical, mechanical, and hydraulic) whereas the rear gate usually has one or more electrical limit switches. The electrical interlocks are usually electrical limit switches. When tripped, the hydrauHc interlock pre-... 

The behavior of a segment s output as a function of the input with respect to time should be accounted for, either in the determination of the trip setpoint or included in the hazard analyses. The selected setpoint should ensure that the SIF responds to achieve or maintain a safe state of the process within one-half of the process safety time with respect to a specific hazardous event. Special attention should be paid to potential delay mechanisms, such as temperature measurements through thermowells and pressure measurement through capillaries, as these mechanisms may obscure dangerous process variations. 

Figure 3 shows a typical function. The objective is to assess the SIL requmemoit of the instrument over-pressure trip function (in tiie minology of BS lEC 61511, a safety instrumented function , or SIF, in emented by a safety instrumented system , or SIS). One issue which arises immediately, when applying a typical riric graph in a case such as this, is how to account for the relief valve, which also protects the vessel from over-pressure. This is a common situation - a SIF backed up mechanical protection. Tlie options are ... 

Critical interlock While identifying the hazards it is important to categorize critical interlocks (for new plants, data/experience from similar plants may be helpful) for which sufficient backup may have to be arranged as a safety measure. In many of these cases, in addition to software interlock, hardware interlocks are also provided. In some cases, even mechanical protection is provided. A critical trip interlock pertinent to a turbine is an example. For turbine overspeed, condenser vacuum, etc., in addition to electronic interlock (with sufficient hardware/software redundancy), mechanical interlocks are provided so that the equipment is saved. Choke and kill in offshore is also an example of this. Regulations To meet the requirement of a regulatory board or company standards, measures are taken to enhance overall safety. Incorporation of these safety measures does not always mean that risk is adequately reduced. These measures could make the system acceptable for use, and a local regulatory board may require additional precautions. An example will elaborate the situation. Many turbine manufacturers give low forward power relays or reverse power... 

As discussed in WCAP-15776, (Reference 6.7) the setpoints provide a margin to the safety limits which are assumed in the accident analyses, to allow for uncertainties and instrument errors. The safety limits are based on mechanical or hydraulic limitations of equipment or on heat transfer characteristics of the reactor core. While most setpoints used for reactor trip are fixed, there are continuously calculated setpoints for the overtemperature and overpower AT trips. 

One of the most important safety components on any high pressure compressed gas system is the flow restrictor. There are two t5q)es of flow-restricting devices an excess flow switch and a flow restrictor. The excess flow switch can be either mechanical or electromechanical and has an excess flow sensor which trips a valve, shutting off gas flow when a preset limit is exceeded. The restrictor is a passive device (limiting orifice) which is sized to limit the flow of gas to a predetermined rate. 

Multiple sensors redundant fall safe circuits and electrical components and multiple, carefully designed mechanical components make the Horisontal Hod Control and Safety System high reliable The sensors and the logic used for power setback and safety (scram) trips are outlined in Table 5 9 of the first volune ... 

Trip This is a safety device that automatically shuts down a piece of equipment. It s a fail-safe mechanism often activated by unlatching a spring-operated valve, which then closes. 

SAs. By changing the simulation materials loaded in standard SAs, CLEAR-0 can simulate various cores. Meanwhile, two reactor trip systems based on a different mechanism are designed to ensure CLEAR-0 safety. CLEAR-0 has two operation modes one is the critical mode for fast reactor validation and the other one is the subcritical operation mode driven by the accelerator neutron source for ADS validation. 

The Safety Setting Input Units (SSIUs) are three redundant devices, one for each trip unit. Each SSIU has a front panel, which provides as many sets of thumbwheels as Safety System Settings (SSS) are required by its related trip unit. Appropriate values for these SSS are defined by an authorised operator through these thumbwheels and they are read into RAM only once every time the trip unit is power-on. Each SSIU has a panel-door, which is mechanically locked in its closed position, to allow no changes of its SSS while its related Trip Unit is operating. In case this mechanical protection is overridden, the unlock SSIU shall power-off its related trip unit. 

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