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SERVICE OFFERING - Master Equipment List (MEL) Unique Identifier (UNID) Assessment / Optimization / Development

WSC, Inc. Subject Matter Experts (SMEs) will perform an assessment of the Plant Master Equipment List (MEL) Unique Identifier (UNID) database contained within the Computerized Maintenance Management System (CMMS) to offer solutions for optimization and / or development.  SMEs will also, with input and support from site and corporate management, write and provide a MEL UNID Process Guideline to document the standard to apply in creating the structure of unique identification (UNID) of plant assets (equipment) to be used to support asset management, plant operations, plant maintenance, work management, engineering and supply chain.

Once the scope of optimization and / or development has been established WSC Subject Matter Experts (SMEs), with guidance and support from customer designated departments (i.e. Plant Management / Technical, Corporate Support, IT, etc.), will analyze Piping & Instrumentation Diagrams (P&IDs) and Electrical One-Line Drawings to establish the MEL UNID database(s) for plant equipment.

UNID alpha-numeric character strings are structured with intuitive “Codes” that will appear in up to six (6) “Fields” consisting of 1) Unit, 2) System, 3) Sub-System, 4) Equipment, 5) Component and 6) Sequence Identifier for each plant asset.  Each field is separated by a dash “-“.


A minimum of four “Fields” required.

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“Sub-Systems” can number as many as fifty (50) or more depending on the facility. For example, sub-systems such as Feedwater (FW), Circulating Water (CW) and Service Water (SW) would be classified under System “WA” (Water).

Specific “Equipment” and “Component” codes can number up to 200 or more.  These would include asset types such as pump, fan, motor, valve, transmitter, switch, transformer, electrical bus, motor control center (MCC), circuit breaker, etc.  Equipment and Component Codes are created consistent with drawing identification and / or customer preference.  Equipment is considered the “parent” to the Component / “child”.  Please refer to “Field 4” and “Field 5” in the example table below.

Sequence Identifiers are assigned consistent with the alpha-numeric drawing indicator.  An “Equipment Description” is created for each UNID.

A completed Master Equipment List (MEL) for a typical facility will contain, on average, between 10,000 and 15,000 UNIDs.  This includes “placeholder” UNIDs for Unit, System and Sub-System which are needed for database organization and structure clarity.  Naturally, variations from average facility size (larger or smaller) will be reflected in the UNID count.

A typical UNID would be written as follows for Generic Power Plant, Equipment Description - Unit 1 Feedwater Pump Motor 1A:

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“Parent-Child” equipment relationships are enabled by both the UNID and the associated Equipment Description.  When less than six (6) UNID Fields are used, more reliance is placed on the Equipment Description to ensure “parent-child” relationships.

Character limitations for UNIDs and Equipment Descriptions vary by CMMS capability / limitations.  Typically, the IT Department will provide the guidance.  Generally, UNIDs are limited to between 25 - 30 characters (including dashes “-“).  Equipment Description character limit ranges are usually approximately 80 - 85.

Legacy information, in most cases, will need to be preserved by maintaining associations between old and new identifiers.  WSC will ensure necessary legacy associations are contained in the deliverable.  Drawing reference identification numbers are provided with the deliverable as well.

All work can be accomplished remotely, or through a combination of on-site and remote activities.  Consistent communication via telephone, web meetings and virtual conferencing are essential.  Meeting frequency and the associated time durations are managed closely to address specific, planned agenda items thus ensuring that both customer and WSC personnel time commitment productivity is maximized.

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