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Instrument Diagrams Checklist


When checking an instrument diagram, the subject matter to be considered may be broken down into categories. The responsibility of the checker varies for each of these categories. Listed below is a brief description of each category to clarify the situation.

  • Representation of the instruments and instrument systems - ­simply a proofreading exercise to ensure that the diagram features are correctly represented in accordance with standards and design practices
  • Instrument applications - the engineer is responsible for determining that the instrumentation portrayed is shown per the specified instruments

☐  Is the Drawing Title information correct per drawing list?

☐  Have all the latest and correct data and information, such as scope of work, sketches, notes, marked prints, calculations, technical drawings, etc., been used to prepare drawings?

☐  Have standards and specifications been identified in the Title Block?

☐  Has the "Instrument Loop Number Allotment Block" been properly filled in?

☐  Has the drawing type been identified and indicated in the Title Block?

☐  Have all column numbers and spacing been correctly indicated?

☐  Has all equipment required to understand the process been shown on the Instrumentation Control and Design (ICD) drawing?

☐  Has all process equipment requiring service-line connections with instrumentation been shown, including such accessories as internal and external coils, steam heaters, removable coils, or jackets?

☐  Have service headers and accounting instrumentation been shown?

☐  Are all instrument items properly identified by loop number?

☐  Have all notes been checked for accuracy and location on drawings?

☐  Have the references to other diagrams been properly identified?

☐  Has the diagram been checked against other functions' diagrams?

☐  Have jacketed pipelines containing instrumentation been indicated?

☐  Has each pipeline containing instrumentation been numbered, sized, and specified?

☐  Has instrument heat tracing been shown?

☐  Have instrument freeze protection, O'Brien boxes, pre-traced tubing, and heatpaks been indicated and identified?

☐  Have instrument purges been properly shown and identified?

☐  Have start-stop push-buttons and running lights been added to motors requiring remote operation?

☐  Has the process flow direction been shown?

☐  Has the to-and-from cross-referencing drawing numbers been indicated on the destination or source of instrument lines and process lines?

☐  Do the tie-in points (asterisks) for interlocks show logic (if required) or schematic diagram reference numbers?

☐  Have standard instrument symbols been used?

☐  Have any non-standard instrument symbols that were used been properly identified?

☐  Have similar installations and applications been shown in a consistent manner?

☐  Has flow relationship to instruments been verified (orifice plates, pressure regulators)?

☐  Are vessel internals (trays) that affect instrumentation indicated?

☐  Are instrument items sequenced in pipelines with respect to process flow?

☐  Have the instruments mounted on racks and panels been properly indicated with panel/rack number (top hat)?

☐  Have the control systems gauges, controllers, etc., been properly indicated?

☐  Has the control system been identified in the diagram?

☐  Has the instrument air or electrical supply symbol been shown where required?

☐  Have all revisions and holds been checked and indicated?

☐  Has the diagram been reviewed for safety considerations?

☐  Have the responsible designers and engineers checked the drawing?

☐  Have proper signatures/initials been applied to the drawing?

☐  Where applicable, have IP Codes been indicated?

☐  Have control valve actions been identified and indicated, including solenoid valve actuation?  Have on-off valve fail actions been shown?  Have proper sizes been indicated?

☐  Have "by Vendor" devices been identified with reference to "Technical Drawing" number?

☐  Have chemseals with capillaries been identified and shown with correct process connection?

☐  Do inline and online instrument connections indicate size and reducers, if needed?

☐  Have vessel nozzle sizes and identifiers been checked and verified against vessel detail?

☐  Have all safety I/O been properly identified and indicated?

☐  Have switch functions been identified (for example: H, L, C or O)?

☐  Has the analyzer been defined and indicated?

☐  Has the analyzer sample system been defined and indicated (components, tubing material type, heat-tracing, houses/enclosures)?

☐  Has the analyzer sample point been defined and indicated (extraction devices)?

☐  Has the analyzer sample return point been defined and indicated (tubing material type, heat-tracing, treatment of disposed sample)?

☐  Has the analyzer power requirements been defined and indicated (24VDC, 120VAC, 240VAC)?

☐  Has the analyzer communication/interface been defined and indicated (connection to analyzer or plant control system)?

☐  Has the analyzer calibration and zero requirements been defined and indicated (standards gas bottle racks, connections to analyzer)?



Tags: Diagrams Checklist Instrument