The Lexicon for Safety and Automation.
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Architecture
| Specific configuration of hardware and software elements within a system. |
B10d
| Lifetime of products before 10 % of the product range fails “dangerously” |
Beta-Factor (β)
| Beta factor or common cause factor; |
Category (CAT)
| Classification of the safety related parts of a control system in respect of their resistance to faults and their subsequent behavior in the fault condition, and which is achieved by the structural arrangement of the parts, fault detection and/or by their reliability |
CCF
| Failure due to a common cause |
CCF measurements;
| proportion of failures which have a common cause |
Diagnostic coverage (DC)
| Measure for the effectivity of diagnostics, may be determined as ratio between the failure rate of detected dangerous failures and the failure rate of total dangerous failures |
Diagnostic test interval
| Time period between online tests carried out in order to detect faults in a safety-related system with the specified degree of diagnostic coverage |
Diversity
| Use of diverse means to execute a required function. |
Fault
| State of an item characterized by inability to perform a required function, excluding the inability during preventive maintenance or other planned actions, or due to lack of external resources |
Functional Safety
| This is one part of the overall safety measures, based upon the EUC and the EUC routing and control system, and is dependant upon the correct functioning of the E/E/PE safety oriented system and other risk reducing, safety oriented system technologies and external facilities. |
Intended use of a machine
| Use of a machine in accordance with the information provided in the user information |
IP
| The Internet Protocol, summarised as IP, is referred to and used in connection with the protocol family TCP/IP. Its main function is to address data packets and transfer them into a connectionless packet oriented network (Routing). All stations and terminal equipment have an independent address in the network, the IP address. The IP address, according to IP version 4, is 32 Bit in size. It is divided into 4 byte sections and is separated by dots. For example: 127.0.0., every byte can have a value from 0 to 255. In order to extend the address room the IP V6 was introduced, which is composed of a 128 Bit address. |
PAScal
| Calculation software for verifying functional safety |
Performance Level (PL)
| Discrete level to specify the ability of safety-related parts of control systems to perform a safety function under foreseeable conditions |
Proof test (T1)
| Periodic test performed to detect failures in a safety related system so that, if necessary, the system can be restored to an “as-new” condition or as close as practical to this condition. For most units, a proof test cannot be implemented for technical reasons |
Redundancy
| The duplication of means required by a functional entity to perform a required function or in order for data to represent information |
Residual risk
| Remaining risk left over once safety measures have been put in place. |
Risk
| Combination of the probability of occurrence of harm and the severity of that harm |
Risk analysis
| Combination of the specification of the limits of the machine, hazard identification and risk estimation |
Risk assessment
| The overall process comprising risk analysis and risk evaluation |
Risk evaluation
| Judgment, on the basis of risk analysis, of whether risk reduction objectives have been achieved |
Safety function
| Function of the machine whose failure can result in an immediate increase of the risk(s) |
Safety integrity
| Probability of a safety-related system satisfactorily performing the required safety functions under all stated conditions within a stated period of time |
Safety Integrity Level (SIL)
| Discrete level (one out of a possible four) for specifying the safety integrity requirements of the safety functions to be allocated to the E/E/PE system, where SIL 3 (SIL 4 in the process industry) has the highest level of safety integrity and SIL 1 has the lowest |
SIL claim limit (SILCL)
| Maximum SIL that can be claimed for an SRECS subsystem in relation to architectural constraints and systematic safety integrity |
SRCF – Safety-related
| control function Control function implemented by an SRECS with a specified integrity level that is intended to maintain the safe condition of the machine or to prevent an immediate increase of the risk(s) |
SRECS
| Electrical control system of a machine whose failure can result in an immediate increase of the risk |
SRP/CS – Safety-related
| part of a control system Part of a control system that responds to safety related input signals and generates safety-related output signals |
TCP
| The Transmission Control Protocol, summarised as TCP, is part of the protocol family TCP/IP. Every TCP/IP data connection has a transmitter and a receiver. The principle is a connection oriented data transmission. In the TCP/IP protocol family, TCP, a connection oriented protocol, takes on the function of data security, controls data flow and takes action in the event of data loss. |
Subsystem
| Entity of the top-level architectural design of the SRECS where a failure of any subsystem will result in a failure of a safety-related control function |
UDP
| The User Datagram Protocol (UDP) has the same function as TCP. As a connectionless protocol it has no methods to ensure that a data packet arrives at a receiver. These measures must be carried out by superior levels. UDP is a faster communication version in comparison to TCP. |
Validation
| A confirmation process which takes the form of an investigation and the provision of a certificate and is carried out in order to demonstrate compliance with the special requirements of a specific intended use |
Verification
| A confirmation process which takes the form of an investigation and the provision of a certificate and is carried out in order to demonstrate compliance with requirements |
