Authors
Jim Lamar
Saint-Gobain NorPro
Muralidhara A
JMP
Objective
Study the use of Nested Variability chart to understand and analyze the different components of variances. Also explore the ways to minimize the variability by applying various rules of operation related to variance.
Background
Saint-Gobain NorPro (subsidiary of Saint-Gobain) is an international company with an undisputed leadership position in providing an impressive collection of engineered ceramic media and shapes using leading edge ceramics technology. The company has been serving the petrochemical, chemical, refining, environmental and gas processing industries for well over 100 years; even more impressive is that parent company Saint-Gobain has served its customers for more than 350 years.
The ceramic pellets manufactured by the company are used for multiple purposes, including:
- -Supporting media, literally supporting the bed of catalyst inside a reactor vessel for the chemical and refinery industries.
- -Filtering media at the top of the large reactors, cleaning up the feed streams before these streams interact with the catalyst.
- -Carrying catalysts to ensure certain reactions take place, then using the ceramic pills to hold the metals in place inside the reactors.
Depending on the customer’s application and reactor size, an order of carriers could range from 50,000 kg to 200,000 kg. Since many of the products are custom-made to suit the application and the exact geometry of the reactor, Saint-Gobain NorPro often makes the same pills in varying sizes for a single customer with multiple reactor sizes.
The ceramic pills come in a wide variety of shapes and sizes. Some spheres are as small as 3 mm in diameter and weighing a tenth of a gram. Some rings are 35 mm in diameter and weigh up to 10 grams. Other cylindrical or multifaceted shapes can range from 8 to 15 mm in diameter with variable lengths and weighing 0.5 to 1.0 gram.
Customer order fulfillment
When a customer buys 100,000 kg of a specific media consisting of 500 pills per kg, that translates to 50 million individual pills. Naturally the customer expects 100% consistency in pills delivered, meaning that all the pills are exactly same. But Saint-Gobain NorPro can’t make 50 million pills at one time. It runs a continuous operation making small batches of green ware that are later loaded into large kilns and fired into a finished ceramic called fired ware. It takes several days to make enough green ware to start loading into the kilns and a few more days for all of the product to flow through the kilns. So, for an order this size, it takes many days or even weeks of continuous production to complete. During this period, there will be many variables, from shift changes to new batches of raw materials to replacing the dies, etc.
Quality control
A small sample of the fired ware is collected every minute of every day throughout the production period and placed in a sample reservoir, all of which happens while the main product stream is flowing into a super sack (SS). When the super sack is full (roughly 500 kg), the sample reservoir is dumped into a smaller sealed bag, which becomes the composite sample for the super sack. Multiple super sacks are made each day, meaning bags of composite samples for each super sack. Half of the material from every super sack’s composite sample is put into a five-gallon bucket as the daily composite sample.
The lab then mixes this daily composite sample to achieve homogeneity (a process called riffling) and then analyzes the quality of the product for that day. Next, the lab conducts the Wetted Ionic Deposit Index (WIDI) test to capture the sample’s score, which is an excellent predictor of how well the pills behave as catalyst carriers. If a problem is noted, the lab can also riffle and analyze each super sack sample to identify the exact time and day when the process might have drifted off.
The Task
One of the commercial managers observed a high variability (which is the enemy of quality!) in the products delivered to a customer and wants the plant to fix it. As is all too common in the world of manufacturing, the production department says the problem is in the lab’s inability to measure the quality properly. However, the lab says the problem is that production is not controlling the process tightly enough. The R&D team thinks that everybody at the plant is doing everything wrong and everything needs to be fixed. But the plant manager does not have the resources to explore every step in the process. So, there is a need to leverage the available resources to fix the problem to minimize variability. The task is to identify the greatest source of variability so that the team can align their resources to make the greatest improvement.