Open to trip

The application of a valve will affect its failure rates and failure modes. One key variable is position of the valve in order for a safety instrumented function to achieve its safe state. The valve must be designed to be "close to trip" or "open to trip." There are generally no tight shut-off requirements when the valve opens to perform the trip. 

Resilient Butterfly Valve, clean service Open to trip 63.6%... 

Does a valve have the same failure rates and failure modes if used in an open-to-trip configuration versus a close-to-trip configuration ... 

In the case of de-energize type logic set of contacts, opens to trip or shutdown the system (in case of energize to trip logic, contact closure will be considered for trip also series, parallel configuration types will be reversed). When trip is associated with proper cause it is safe failure. When this is NOT, then it is spurious/nuisance trip or shutdown. As per lEC 61508 Demand or failing element commands output to a safe state. 

Since the thermistor circuit will trip the protective circuit as soon as the thermistor current reduces drastically, it provides an inherent feature to trip the protective circuit even when the thermistor circuit becomes damaged or open-circuited accidentally, extending a feature of fail to safety . 

The NO (normally open) contact of I/C-1 (520 is wired in the trip circuit of I/C-2 (52 ii) and vice versa. As soon as an interrupter is closed, the tripping circuit of the other gets ready to trip. 

As previously mentioned in Chapter 5, one of the most severe disturbances for the power recovery train (PRT) is a generator breaker opening. This event often causes the PRT to trip on overspeed or other process or machine conditions. A control solution has been developed to keep the PRT and the process under control during breaker opening. 

Step 1 Calculate actual expander power before breaker opening. To determine the required power from the expander after the breaker opening, it is neeessary to know the aetual power developed by the expander before breaker opening based on readily available and reliable measurements on the expander. Typieally these are Pj, Tj, Pj, Tj, and N. The PRT speed ean be ignored beeause it is nearly eonstant before and after the breaker trip and the expander performanee eurve is typieally a weak funetion of rotational speed. 

Dagang, a Vice-President of the Chinese Academy of Science. The two became overnight friends, and before leaving Tokyo exchanged invitations to visit their respective institutes. Although it seemed unlikely in 1966 that their invitations would be honored, U.S.-Chinese relations warmed immediately after President Richard Nixon s famous trip in early 1972. As a result of his own "opening to China", Mark was the first western chemist to visit colleagues in the Peoples Republic. This historic visit was made in June, 1972. 

An example of a causal factor chart for a relatively simple incident is shown in Figure 9-8. In this example, there are two redundant pumps, one of which is required to supply feed to a reactor downstream. The operator is requested to change-over operation from Pump A, which is running, to Pump B, which was previously shutdown. Instead of opening Pump B suction valve, the operator opens the wrong valve, causing the Reactor to trip on low flow detection. 

While I m being taken for a fantastic ride by the Salvinorin. the Salvia entity is simultaneously taking a ride while experiencing through a human reference. I had the feeling that Salvia enjoys being smoked when the smoker s mind is open to take her on pleasant psychedelic journeys and to experience the unique philosophical perspectives which are often attained while tripping. 

A limit switch is a mechanical device which can be used to determine the physical position of equipment. For example, an extension on a valve shaft mechanically trips a limit switch as it moves from open to shut or shut to open. The limit switch gives ON/OFF output that corresponds to valve position. Normally, limit switches are used to provide full open or full shut indications as illustrated in Figure 3. 

During research trips in the United States and Germany, I enhanced these materials with semi-structured interviews. Questions were prepared in advance however, I intentionally structured interviews to allow follow-up queries to insightful responses. While a valuable "primary source by themselves, the interviews were also very helpful for gaining access to private archives and document centers otherwise not open to the public. 

Unit studies easily incorporate listening, reading, writing, speaking, and research skills by virtue of the limitless avenues open to exploration books, held trips, oral history, Internet, and so forth. In addition, learners who follow unit studies are apparently more self-motivated and retain more of what they learn. 

The drive was kept simple and takes the form of a multistage condensing turbine in which considerable effort was made to provide for on-line maintenance. The main trip and throttle valves can be exercised without disturbing the operation and the main condenser, which can be cleaned on the waterside without shut down of the machine. This is very useful to combat fouling from marine growth in the cooling system which of necessity must be open to the atmosphere. 

Under the 55 mph speed limit, trips of 450 to 500 miles are open to question, and runs of 500 miles or more are considered incapable of being made in compliance with the speed limit and hours of service limitation. 

Final element components will fail also, and again the specific failure modes of the components can be classified into relevant failure modes depending on the application. It is important to know whether a valve will open or close on trip. Table 6-3 shows an example failure mode classification based on a close to trip configuration. 

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