Siemens SIPART PS2 6DR51xx Instrucciones de operaciones descargar pdf (Pagina 241)

Glossary

SIPART PS2 with and without HART communications

Operating Instructions, 09/2008, A5E00074631-08

243

layer of the reference model. Transport protocols are used for the lower four layers of the

reference mode and higher protocols are used for control, data provision and application.

Safety function

Defined function executed by a safety-instrumented system with the objective of attaining or

maintaining a safe status of the system by taking a defined hazardous incident into account.

Example: limit pressure monitoring

Safety-instrumented system

A safety-instrumented system (SIS) executes safety functions that are required to attain or

maintain the safe status in a system. It consists of sensors, logic unit/control system and final

controlling elements.

Example: a safety-instrumented system consists of a pressure transmitter, a limit signal

indicator and a servo valve.

Sensor

Converter that converts mechanical or other non-electric variables into electric signals.

SIL

The international standard IEC 61508 defines four discrete safety integrity levels (SIL) from

SIL 1 to SIL 4. Every level indicates a probability range for the failure of the safety function.

The higher the SIL of the safety-instrumented system, the higher the probability that the

required safety function works. The achievable SIL is determined by the following safety-

instrumented characteristics:

● Average probability of dangerous failures of a safety function on demand (PFDAVG)

● Hardware fault tolerance (HFT)

● Safe failure fraction (SFF)

SIMATIC software

Program for process automation (e.g. PCS7, WinCC, WinAC, PDM).

Zero point shutdown

The zero point shutdown guarantees a tight closing of the valve if an input signal is < 2% of

the maximum value. The coil current is then set to zero. The zero point shutdown must

normally be deactivated to set the minimum coil current

Zone 0

Area in which hazardous potentially explosive gaseous atmospheres build up often, regularly

or over long durations during the normal operation of a device.

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Siemens SIPART PS2 6DR51xx Instrucciones de operaciones Pagina 241