NORSTAT Safety Relays - Handbuch (Seite 6)

application guide safety relays from riese electronic page 6
B General definitions
Term Description
AND operation
Connects two or more devices.
Start-up can only occur when all the start-up conditions are met.
Protection
Releasing the switching output passes autonomous after
interrupting the protection area, when no restart interlock is
activated.
Single action By interrupting once the protection area and releasing the
switching output, the start of the machine is carried out.
Double action By interrupting twice successively the protection area and
releasing the switching output, the start of the machine is
carried out.
Actuation types of ESPDs
Reclosing interlock
Reclosing interlock prevents the automatic start after the
protection area is released. The start has to be initiated
manually.
B10D Numbers of cycles, until 10% of the components fail dangerously.
β (Susceptibility to
Common Cause Failure) Rate of failures, which have a common cause.
CCF (Common Cause
Failure) Failure as a result of a common cause
Clocked output
Clock pulse is directed from the clocked outputs to the inputs by corresponding
wiring. Thereby it is possible to recognize cross circuits.
Cross-/ short circuit
detection Detection of cross-/ or short circuits, detection of reduction of the insulation
resistance between 2 contacts and respectively short circuit between 2 wires or
more.
Danger zone
Zone within or around machinery in which a person is exposed to risk of injury or
damage to health.
DC (Diagnostic Coverage) Diagnostic coverage, this can be determined from the ratio of the failure rate
“detected dangerous failures” and the failure rate “all dangerous failures”. The
Diagnostic Coverage is suited as a parameter for the efficiency of the diagnosis.
DCavg (Average
Diagnostic Coverage) Average diagnostic coverage
Enable circuit A redundant implemented output with forcibly guided contacts. The output is used
to switch off a machine.
Equipment, accessible The danger zone can be entered through a light barrier.
Equipment, non-
accessible The area secured by a light barrier is protected, in addition, mechanically (e.g. by a
grid)
Error Describes the state of a device, which is not able to carry out a requested function,
excepted is the inability during maintenance, other planed activities or the failure of
external supplies
ESPD Electro sensitive protective device (ESPD) can be based on physical principles:
Optoelectronics, supersonic, inductive or capacitive sensor technology, infrared
movement sensors etc. An ESPD encloses the following elements: Sensor
function, control / supervising function, output elements (OSSD).
ESPE (Electro-sensitive
protective equipment) See ESPD
Feedback loop Circuit for monitoring externally connected contactors or relays. The N/C contacts
are used to check whether the relays or contactors have assumed their fail safe
before they are re-operated.
Forcibly guided contacts Contacts which are connected mechanically with each other so that N/Cs and N/Os
can never be closed at the same time.
Functional safety The part of the entire plant safety, which depends from the correct function of
safety related systems, for reducing the risk. These systems have to execute their
intended functions (safety functions) under a defined error condition and with a
defined probability.
Housing protection
classes Protection classes characterize the range of protection of a sensor or a machine
against contact as well as penetration of foreign objects or water.
The protection class indication starts with the letters IP. The first number acts as an
indicator for the contact and foreign objects protection, the second number as an
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