Once You Know MS Excel Well You Can Simulate Many Pragmatic Scenarios With It: Mill Grinding's 'Technical Limit Capacity' Modelling

Here is an example of a one-pager dashboard modelling of a grinding mill's 'Technical Limit Capacity'.

To improve efficiency in decision making, this calculator is conjured up as a handy tool for our 'intended recipients'. The inherent 'Technical Limit Capacity' of the grinding system, i.e. based on present support conditions for that specific period of assessment, needs to be established for production planning for the specific time period. Note the mentioning of 'support conditions' and 'specific time period' as these are two of four elements in the definition of reliability and availability. Reliability or availability is; 1. a probability that a component/equipment/system will; 2. perform a specific function; 3. over a specific time period; 4. under specific support conditions (i.e. maintenance).

Establishing our mill's true inherent production capacity for the specific time period will mitigate the risk of overpromising then struggling to deliver on the production targets for a specific time period.

The intention of this workbook is to provide a quick 'what if' scenarios guide calculator. The assumptions and logic applied are modelled based on mill equipment's respective downtime records from AMPLA Downtime Database for a specific budget period. While AMPLA can give you ready made reports, there will be some scenarios where you would want to customise to model yourself and establishing the Mill's ‘Technical Limit Capacity’ is one such example.

The AMPLA determinations are locked. You plug in your ‘what if’ budget availability percent inputs in the 'white cells' which are 'unlocked' and the simulation happens automatically on the graphs so you can compare your expectations with the inherent 'Technical Limit Capacity'. Each graph represents a system availability (and system utilization) for total system and sub-systems which are obtained through ‘Availability Block Diagram’ modelling. A summary rolled-up visual of the block diagram model and formula is also provided on the dashboard.

Note the 'Operating Apportionment Factor' inputs for the SAG and Ball Mills which are key to this modelling. These factors account for the system loss whenever a mill is down. Also, for all availability percents, there is an expected utilisation percent to enter that is factored in the calculations.

The dashboard calculator has automatic colour grades (by Conditional Formatting) to rank from least to most severe plant availability bottlenecks for the specific time period.

Data is exported from customised fields in AMPLA and pasted to the table files in the background to generate instantly this dashboard to play the ’what if' scenarios.

There is also a 'downtime' interactive graph to drill down to the downtime causes for the least available equipment. This also is generated instantly from the AMPLA Downtime Database data dumps.

See article below for more.

Postscript

How the graphs (the orange and black bars) change on the dashboard as availability values are entered in the 'white cells' that are unlocked. The orange bars are budget values while the black bars are values calculated and entered. The calculated values can be from SAP work order historical records.