Data collection

We categorize the input in fixed or dynamic data. Fixed data does not change every week, so these input data should not be updated every week. Dynamic data may change daily and does need to be updated every time you solve the Chemical Distribution Model. The Chemical Distribution Model requires the following input data:

Fixed Dynamic Transport data: Duration 𝒅𝒊𝒋 to drive from location i to location j X

Duration 𝒃 to load Production Chemicals at

central storage location X

Duration 𝒉 to unload Production Chemicals at

delivery location X

Capacity 𝒄𝒊 of storage at location i X IBCs delivered at location between now and last

time the model has been solved X

Duration r for a break during the trip X Chemical injection data: Chemical consumption per Injection Location of

last four weeks from now X

Inventory data: Last known inventory levels per Injection Location X Maximum replenishment level per Injection

Location X

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Fixed Dynamic

 Minimum order level for Production Chemicals 𝒔𝒊 on location i X  Current inventory level of Production Chemicals 𝒆𝒊𝟎 at location i X  Expected injection volume of Production Chemicals in coming weeks,

𝒗_𝒊𝝉 location i in week 𝜏 X

 Maximum orders to be placed 𝒎𝒊𝝉 for location i in week 𝜏 X

As one can see, the majority of the input data is dynamic. We previously described that we need to update dynamic input data every week. For this reason, we have already inserted links in Microsoft Excel, which automatically calculate and/or generate the input data. This increases the efficiency and user friendliness of the Chemical Distribution Model. End users only have to download Chemical consumption data from an internal source, called Business Objects. To calculate current inventory levels, the Model asks to fill out three different dates: the next Chemical distribution date, the last Chemical distribution date, and the last time the model is solved. The current date is automatically generated. The number of IBCs delivered between now and the last time the model has been solved should be inserted as well. Furthermore, the end user has to manually add the last measured inventory levels per Injection Location to the Chemical Distribution Model. This information can be obtained from the last time the Chemical Distribution Model was solved. Operations conduct a physical inventory check every once in a while. To ascertain the reliability of calculated inventory levels, it is highly recommended to update the calculated inventory levels with actual field data from Operations. A dashboard is designed in the Chemical Distribution Model, where the user can add the input for the model.

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The fixed input data is acquired from multiple sources. The durations to travel between locations is gathered from Google Maps Navigation. Our problem consists of 62 different locations and thus 62 by 62 different travel durations. Manually obtaining duration of each possible tour takes days or even weeks. Therefore, a code is written in Microsoft VBA which automatically acquires the duration between trips and add this to the Chemical Distribution Model. This program is able to automatically download the total durations between trips within two hours. The total duration is calculated for passenger cars. However, the Production Chemicals are delivered with trucks, and some roads are obliged to avoid. Therefore, we assume that travel duration increases with 30% on average, when a truck is used instead of a passenger car. The total travel duration between locations can be found in the Appendices.

Duration for loading a truck for Production Chemicals. Duration to load Production Chemicals at central storage location JPB is assumed to be four hours. This assumption is based on analysis of invoices, where the total duration at a central storage location is specified per trip. The total duration also consists of the average duration to travel from and to base locations. Additional time is required when a trip could not be conducted within one day (11 hours), since the truck drives home and restarts the IBC trip a day after. The invoice also includes this ‘additional trip time’. So we also include the average ‘additional time’ in the duration for loading a trucks. The duration for unloading

Production Chemicals is assumed to be 15 minutes. The assumption for average time to unload IBCs at Production Locations is also based on analysis of invoices from the supplier. On average, a truck driver has a break of 1 hour during the replenishment trip.

The capacity of storage at injection locations depends per location. In Chapter 0, we already touched upon the problems with the reliability of level measurements. The level meters may deviate up to 200 Liters from actual inventory levels for the 4000 L skids. We also have to consider that forecasted injection volumes may be slightly higher than the actual injection volumes. This results in higher inventory levels in coming weeks than expected. To prevent the occurrence of spills during replenishment of inventory, we have decreased the actual storage capacity per location with a certain volume. This volume depends on the potential storage capacity. The maximum replenishment levels are being used as input for capacity, and following capacity levels exist:

Actual storage capacity (L) Maximum Replenishment levels (L)

4000 3700

3500 3200

2500 2300

1500 1300

1000 900

Table 7.1 Maximum replenishment levels

The dynamic input for parameters is detracted from analysis of the manually acquired dynamic input data. Current inventory levels are calculated by subtracting the chemical injection volume between the

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date of most recent inventory level update and current date from the most recent inventory level and adding the Chemical volumes delivered in this period.

The expected injection volumes in coming periods is based on analysis of Chemical consumption in last weeks. We calculate the average daily injection volume for past four weeks and for last week. As forecast for daily injection volumes in coming period, we take the maximum of the two calculated average daily injection volumes. However, if the average daily injection in last week is more than 1,5 times the average daily injection in last four weeks, we take the average daily injection volume of last week as forecast for coming weeks.

The minimum order level varies with the expected injection volumes. The minimum order level is at least 200 Liters (safety stock) plus the expected inventory level of one week. Every storage location has a minimum of 200 Liters (safety stock), which is equal to maximum deviation for the measured inventory level from actual inventory level. Appendices show how the dynamic data is automatically generated and displayed in the Chemical Distribution Model.