The Troubleshooting Process

The troubleshooter should obtain the performance and modification history for the machine. This information is typically available from electronic data storage 

All mechanical and electrical components should be examined and verified that they are functioning properly. These components include the solenoid valves for water cooling systems, cooling water pumps, cooling fans, electrical heaters, thermocouples and other temperature sensors, pressure sensors, and gear pump operations. 

Often troubleshooting guides are provided by equipment manufacturers for common problems. These guides are helpful for many of the simpler problems associated with the equipment. Some resin manufacturers are an excellent resource for troubleshooting processing problems that are specific to a resin. Subject matter experts or extrusion consultants are also resources for troubleshooting an extrusion process. 

Spare parts for common components such as heaters for barrels, transfer lines, and dies, thermocouples, pressure transducers, drive belts, and fuses should be kept in stock. Since the goal is to keep the line operational at all times, keeping these low-cost but necessary components in stock can reduce the amount of downtime due to simple failures. For operations where the resin is abrasive or corrosive, a spare screw should be kept in stock. As the screw wears in the extruder and the performance decreases beyond an economic limit, then the screw should be replaced with the spare screw and the worn screw should be sent to a screw manufacturer for refurbishment. 

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Three examples are presented that introduce the use of the equations developed in this chapter. These calculations should be used at the start of the performance analysis of all troubleshooting problems. This analysis will be expanded in subsequent chapters through Chapter 7 using additional tools and understandings to complete the troubleshooting process. 

Performance information for the incumbent resin was missing from the early parts of the decision-making process. The decision that the technical problem was the performance of the new resin was based on anecdotal information from plant personnel on the performance of the incumbent resin. That is, the plant personnel believed that the reject level for parts made from the incumbent resin was less than 5 %. A statistical analysis of the part defect rates was not performed. This lack of information early in the process allowed the plant manager to propose a poor technical solution without understanding the root cause for the defect. Later in the troubleshooting process, a statistical analysis of the defect rate indicated that the incumbent resin had a defect rate that was statistically equivalent to the new resin. 

This example clearly shows that developing and accepting a hypothesis based on accurate and complete information is necessary for setting an acceptable technical solution. If the plant manager could have persuaded the resin manufacturer to develop a new resin that was similar to the incumbent resin, then the defect would still be there, the cost of the troubleshooting process would have been extremely high, the supplier would have incurred unnecessary development costs, and a high level of defective parts would still have occurred because the root cause would not have been removed. 

A. The first step in the troubleshooting process is to talk to the customer. It is best to obtain as much information as possible from the user so you have an idea of where to begin your troubleshooting. 

By closely following the introduction of the optimized steps at the site where the problem occurred, one can monitor the results immediately and quickly make any further adjustments that are needed. If the modified operations did not solve the problem, it is necessary to begin the troubleshooting process again. 

Method failures can, of course, occur at any stage in the progression from transfer to validation to sample testing. Therefore, the troubleshooting process discussed in this chapter applies to any of these stages. 

It should be noted that not all changes have an immediate effect on the process. In some cases, there can be a considerable incubation time before the effects of a change become noticeable. This, of course, complicates the troubleshooting process it is important to keep this in mind and not jump to conclusions. The author experienced a case where a disastrous wear problem was related to an event that took place four months earlier. The wear remained insignificant until about four months after a new feed housing was installed. However, when the rapid wear started, the screw was destroyed within a time period of only 48 hours. 

There are a number of tools that will help during the troubleshooting process. A discussion of a number of the important tools follows. 

Implementation of a test program control routine that executes the stimulus routines. When a failure is detected, the guided probe database is invoked to determine the next step in the troubleshooting process. 

Control loop—system consisting of a collection of instruments that work together to control pressure, temperature, level, flow, and anal3itical variables. Information from control loops is invaluable in the troubleshooting process. 

The troubleshooting process requires a wide array of skills and techniques. The primary goal is to control variables such as temperature, pressure, flow, level, and analytical. With modern control instrumentation, such as indicators, alarms, transmitters, controllers, control valves, transducers, analyzers, interlocks, and so on, it is possible to control large, complex processes from a single room. 

Replacement parts for most HVAC controls are available directly from the manufacturers or their authorized distributors. The decision regarding repair versus replacement of the device is easier for controls than it is for mechanical equipment in an HVAC system because controls usually are much less expensive—and the troubleshooting process often recommends replacement. In general, there are three scenarios for inoperable or damaged equipment ... 

Some devices have the ability to record an additional signal between the can and a shocking coil, which can mimic a surface EGG lead. This can also aid the interpreter in the troubleshooting process, particularly when dealing with a single chamber ICD. 

Once the solution is implemented, it is often helpful to review the troubleshooting process itself, either in a Lessons Learned review, or as part of a Continuous Improvement program. That review may also involve a reassessment of your vendor-sourcing protocol, not just in whether a given vendor is actually capable, but in the methods that were used to evaluate that vendor in the first place. 

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