BS 7986-2005 pdf free download

BS 7986-2005 pdf free download.Data quality metrics for industrial measurement and control systems Specification.
control loop switches immediately to manual.
— An optimization function can monitor the uncertainty and drive the process as close as possible to a plant constraint or limit. When uncertainty increase., the operating state is automatically moved away from the limit to provide an increased margin of safety.
— Loop gain may be decreased when uncertainty indicates a less accurate measurement, so unnecessary cycling can be reduced.
— When uncertainty decreases, loop setpoints may be moved closer to operating constraints and loop gain may be increased to provide for faster responses.
Measurement reporting functions and control decision functions may be distributed into different parts of a fleldbus network and implemented by different suppliers.
These and similar examples of control responses using data quality metrics are shown in Figure 1.
NOTE 2 Thec actions can be taken automatically by control agents seeking to maintain best. control performance in response to
changing device performance capability.
4.3.2 Improving maintenance performance
4.3.2.1 General
Device status in conjunction with other data quality metrics shall he suitable for first level planning of maintenance actions and plant shutdown events.
The availability of maintenance status values from self checking devices shall be device independent. enabling the development of re.useable maintenance packages and procedures for all instrumented units within a site or an organization to gain related operational benefits.
NOTE I These functions are intended to support just-in-time maintenance scheduling using real-time quality estimates from devices.
Several levels of maintenance priority shall be supported.
NOTE 2 Intelligent devices Lire often multi-measurement with failure modes that invalidate some measurements but not others, so
a traditional “goodibad” maintenance indication for the complete device is not appropriate.
4.3.2.2 Application mapping
NOTE 1 It should be recognized that service priorities issued by a device or its instrument channel are a device designer’s best estimate of urgency for service needs. These device estimates need to be modified by an appropriate user maintenance function to produce values that reflect the importance of the device within the user application.
For example, a low priority alarm issued by a key measurement device in a safety application should have more significance than a low priority alarm issued by a device executing a secondary process task.
The four primary states specified in Table 1 shall be distinguished for use with any device, based on internal data and local diagnosis.
These statuses shall be chosen to support two basic operational questions.
— How urgent is the maintenance need?
— When is it essential that plant operation is modified or stopped?
These status values shall be suitable for use by operators and maintenance engineers to prioritize and schedule service activity with minimum process disturbance and maximum operating benefit. Figure 2 shows a mapping function located in a maintenance terminal that converts generic device status values into application specific alerts for operations and maintenance agents.
NOTE 2 Details about a specific fault diagnosis and exact repair needs for a device are always important, but these items arc device specific and secondary to the operational issue. of when it is essential that maintenance is scheduled or production stopped.BS 7986-2005 pdf free download.