Quality variation

The raw material quality variations have a high impact on the schedule itself, as also the time for logistics (e.g., crane movements) has to be taken into account and... 

Sometimes in a process study undertaken to determine the basic causes of some quality variation, the same turmoil may exist. We may show a relationship in a study of a month s data which seems to say that the colour stability of a product is related to the concentration of a metallic contaminant. The next month s data may fail to show this relationship, but may indicate an association with an organic contaminant. Another month s data may show both, or may fail to detect any effect due to either. 

Two new sources of taw snateris were introduced into a process. The process conditions could he adjusted to maintain equal levels of quality, but the batch-to-batch variation might be different for batches made from the two materials. Nine batches of material A were run along with seven batches of material B. The variance of the runs made with material A was 10-72. The variance of the runs made with material B was 3 97. Is there a difference between the two materials in their effect on quality variation, using 90% significance ... 

FIGURE 2 Graphical illustration of the correspondence between the defects per million opportunity (DPMO) process capability (Cpk) and process sigma (assuming normally distributed quality variation). 

Other potential benefits arise from the 33% space saving of MF/UF and the opportunity to increase RO flux and water recovery. Moreover MF/UF provides a more reliable system, and is tolerant of feed-quality variations [7]. 

Knott, J., Shurson, J., and Gohil, J. (2003), Variation in Particle Size and Bulk Density of Distiller s Dried Grains with Solubles (DDGS) Produced by "New Generation" Ethanol Plants in Minnesota and South Dakota, (Website http //www.ddgs.umn.edu/ research-quality/variation.pdf). Department of Animal Science University of Minnesota. Last modified 9/11/03. 

Quality assurance is an important consideration for the user and producer. Both aspects are discussed by Puls (17) in his symposium paper. Lot-to-lot variations in purchased catalyst can be minimized by a system of statistical process control by the catalyst producer, his supplier, and the user. The statistical process helps to minimize product quality variations by instituting corrective action on a real-time basis to prevent the production of off-specification material. 

Quality variations in the polymer produced in bstch reactors are often caused by slight variations in the reactor start up procedure. Furthermore, the polymerization rate may change considerably during the batch and this may give tempetature variations that are difficult to reproduce causing batch-to-batch variations in quality. These problems would be minimized with CSTRs if the continuous reactor system could be operated for at least several weeks before wall fouling and coagulum buUd up become critical and require reactor shutdown for cleanup. If an effective start-up procedure for a continuous reactor train is not available, the costs associated with offspec material could make continuous operation uneconomical. In addition, with a continuous reactor system one loses the flexibility of batch reactors when a multiproduct operation, with its short productions runs, is involved. 

Bohacs K. M. (1993) Source quality variations tied to sequence development in the monterey and associated formations, southwestern California. In Source Rocks in a Sequence Stratigraphic Framework, AAPG Studies in Geology 37. American Association of Petroleum Geologists, Tulsa, OK. 

Jacobson, R.L. and Langmuir, D., 1974, Controls on the quality variations of some carbonate spring waters, J. Hydrol. 23 247-265. 

The performance requirements can be represented either by constraints or by a contribution to the operating costs. In some cases, this is straightforward-equipment and material and energy inputs can be included in an economic objective constraints for which violation leads to plant shutdown are well approximated by a hard constraint. In other cases, the choice of representation is more difficult—excessive quality variations may lead to complete loss of the market for a product (constraint) or reduced price for the product (objective). 

The first seven cycles of an in situ iron removal project in The Netherlands were simulated with the hydrogeochemical transport model PHREEQC (version 2). The concentration changes of CH4, NH/, Mn, Fe , P04 and As are discussed in detail. Arsenic shows concentration jumps in pumped groundwater which are related to oxidation/reduction and sorption/desorption reactions resulting from the water quality variations. 

Blush and bloom are caused by the etching of the anodized oxide which changes the surface reflectivity of the trim material. Problems of a milky white appearance (blush and bloom) on the surface of anodized aluminum trim have frequently been reported. However, this effect has been more pronounced in recent years in the Northeast USA and Canada. Although in previous years the problem has been related to quality variations, recent data indicates that acid precipitation enhances this effect. 

Less variation. Quality variations are less extreme and less frequent, as depicted in Figure 2. 

Native luciferase obtained by collecting fireflies was prone to quality variations. Several companies now supply recombinant luciferases in various genetically modified forms. Modification to obtain one desirable property, e.g. thermostability, may change other characteristics, e.g. specific activity, K values and pH optimum. The specific activity must be taken into account when comparing prices per mg. A generally agreed unit for measuring luciferase activity is needed, since rlu are dependent on luminometer and reaction conditions. 

Figure 6. Water quality variation with discharge of the Mattole River, November 24 to December 19,1966...

Study of water quality variation along a river... 

Figure 5. Wastewater quality variation with time.

Figure 10 presents a synthesis of the main phenomena involved in wastewater quality variation along a sewer network, emphasising on solid transfers during dry and... 

This point is very important mainly in view of the design of a measurement strategy for industrial wastewater quality control. Among the analytical techniques available for the study of the complexity and qualitative variability of the medium, UV spectrophotometry is well adapted for the quality variation control of industrial wastewater (see Chapter 2). 

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