Specifications

A specification defines the target value and various upper and lower quality/alarm limits for a variable and a product combination. It can be used to define the amounts of materials in a batch process, measure the actual value of a quality variable against a target and set of limits, or compare the current values of a set of process related variables against the average of a number of past sets. Specifications are defined for a specific product. They can be as general or detailed as needed and can be Production Unit/Line specific or shared across many production units/lines.

Specifications can be configured and managed within Plant Applications by three different methods. Depending upon the type of production process that needs to be modeled, a combination of these three methods can be used.

  • One method is to assign specifications at the variable level for a specific product on a specific production line. This method is called Unit Level Specification Management. In a typical Plant Applications software installation this method is used to manage the process variable specifications for a single production unit or machine.

    The Unit Level specifications are defined at the “machine” level and they override any other limits defined at the Central and Corporate levels. They are defined directly on the variable for each product. They are the best strategy for maintaining process operating settings such as target levels, pressures, temperatures etc. The typical application would be for a single-line facility where products and variables are fairly independent.

  • The second method manages specifications centrally and assigns them to the multiple variables and/or products that have them in common. It normalizes specification limits for common products and variables. This method is called Central Level Specification Management. This second method is normally used to manage quality related product specifications on a plant-wide basis with multiple production lines.

    The specifications are organized by properties with characteristics and specification variables. Products are associated to characteristics and variables are associated to specification variables.

  • The third method manages specifications at the corporate level where specifications can be shared amongst plants on one site or many sites. This method is called Corporate Level Specification Management.