Managing Process Variability

Surveys of this kind are of course subject to bias. Individuals are perhaps more likely to respond if they unhappy with the system generally or the way that it has been implemented. As with the other metrics, trends observed over time are more informative than taking a snapshot view. 

One final metric that may be chosen to assess SMS performance is the level of residual risk itself. It could be argued that an optimal SMS will ensure that all hazards are mitigated to as low as reasonably practicable thus where there are risks which are insufficiently controlled this represents deficiencies in the process itself. This approach can be attractive to manufacturers who don t necessarily have access to the outcome metrics available to healthcare organisations. 

The need to vary a process from one project to another can occur for a number of reasons. These include  

Where a variation to the process is considered, this should be formally documented in the CRM Plan for each system under assessment along with the rationale and jnstihcation for the variation. The process documentation itself could also set out any basis for omitting relevant steps. Building in process flexibility at the time of SMS development facilitates the straight-forward justification of the approach when one applies the process to a product. 

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HME is a continuous and efficient process, which thus enables high throughput, online monitoring, minimal and controlled processing, and manageable process variables. 

Control of the process. Prevention of hazardous deviations in process variables (pressure, temperature, flow), by provision of automatic control systems, interlocks, alarms, trips together with good operating practices and management. 

The fundamental goal of TQM and TQC (total quality management and control) is to program, measure, and keep process variability under control. Some of these methods discussed in this chapter are as follows ... 

Arguably, the most important aspects of quality management for PAT are the concepts of quantitative process performance characterization using process capability indices as universal descriptors, which form the basis of the measure and analyze portions of the DMAIC model. Process capability indices consider simultaneously both process variability and process specifications to determine whether... 

One procedure that makes subsystem evaluations and performance qualification trials manageable is the application of constraint analysis. Boundary limits of any technology and restrictions as to what constitutes acceptable output from unit operations or process steps should in most situations constrain the number of process variables and product attributes that require analysis. The application of the constraint analysis principle should also limit and restrict the operational range of each process variable and/or specification limit of each product attribute. Information about constraining process variables usually comes from the following sources ... 

Process measurements encompass the application of the principles of metrology to the process in question. The objective is to obtain values for the current conditions within the process and to make this information available in a form usable by the control system, process operators, or management information systems. The term measured variable or process variable designates the process condition that is being determined. 

The plant control system functions to limit temperature rates of change during plant load change and upset events. This is achieved at two different levels. In the time asymptote the control system through control variable set points (with values assigned as a function of steady-state power) takes the plant to a new steady-state condition. The set point values are chosen so that hot side temperatures remain little changed. In the shorter term the control system manages the dynamic response of the plant so that the transition between steady states is stable and with minimal overshoot of process variables. 

The objectives of this test pattern is to analytically resolve these problems into three manageable segments. The first task will be to define the viscoelastic kinetic properties of a material as a function of various reaction temperatures. These properties (viscosity, viscous modulus, elastic modulus, tan delta) define the rate of change in the polymers overall reaction "character" as it will relate to article flow consolidation, phase separation particle distribution, bond line thickness and gas-liquid transport mechanics. These are the properties primarily responsible for consistent production behavior and structural properties. This test is also utilized as a quality assurance technique for incoming materials. The reaction rates are an excellent screening criteria to ensure the polymer system is "behaviorally" identical to its predecessor. The second objective is to allow modeling for effects of process variables. This will allow the material to undergo environmental... 

Sequence control of process operations, and recipe/batch management and tracking. Alarm and device interlocking (often in addition to separate hard-wired systems). Event and alarm recording, and historical trend recording of process variables. 

Francis Pitard Sampling Consultants, LLC. (1995). Software Process Variability Management. Bloomfield, CO. 

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