Unscheduled downtime

Boiler Deposits. Deposition is a principal problem in the operation of steam generating equipment. The accumulation of material on boiler surfaces can cause overheating and/or corrosion. Both of these conditions frequentiy result in unscheduled downtime. Common feed-water contaminants that can form boiler deposits include calcium, magnesium, iron, copper, aluminum, siUca, and (to a lesser extent) silt and oil. Most deposits can be classified as one of two types scale that crystallized directiy onto tube surfaces or sludge deposits that precipitated elsewhere and were transported to the metal surface by the flowing water. 

Because of this, all new machinery should be thoroughly inspected for defects before installation. Acceptance criteria should include guidelines that clearly define acceptable design/operational specifications. This practice pays big dividends by increasing productivity and decreasing unscheduled downtime. 

Process reliability is the ability of the process to consistently produce required results as measured through the primary dimensions of uptime, dependability, and first run yield [97]. Uptime is the time the process is in operation compared with the available time the process is scheduled to be in operation. Dependability is the repeatability of a process actual run rate compared with its scheduled run rate. First run yield is the ability to produce quality outputs the first time through production run without any rework. Reliability losses are measured in terms of unscheduled downtime, run rate losses, yield losses, and reprocessing [97]. 

Two unanticipated events took place at Poelkapelle. In one of them, there was some difficulty in opening the vessel lid. This was due to the deposition of dust on the traveling rail on which the lid moves laterally. Unscheduled downtime also occurred when a 21-cm... 

An effective MOC program will help increase production rates because there will be fewer direct losses from unscheduled downtime and from undesired events such as flaring or the recycling of off-spec product. Also, internal losses from problems such as reactor temperature excursions will be reduced. 

LPR is particularly useful as a method to rapidly identify corrosion upsets and, thus, evaluate remedial action, reducing and minimizing unscheduled downtime, thereby prolonging plant life. 

Increasing the resistance of equipment to corrosion is highly beneficial because it extends service life and cuts unscheduled downtime. Even though fluoropolymers may increase the initial equipment cost, lifetime costs can be reduced, allowing manufacturers to be more competitive and in especially severe service such as exposure to hydrogen fluoride, carbon steel components lined with PTFE or PFA have replaced exotic metal alloys at a lower initial cost. 

A survey of 500 plants that have implemented predictive maintenance methods indicates substantial improvements in reliability, availability and operating costs. The successful programs included in the survey include a cross-section of industries and provide an overview of the types of improvements that can be expected. Based on the survey results, major improvements can be achieved in maintenance costs, unscheduled machine failures, repair downtime, spare parts inventory, and both direct and in-direct overtime premiums. In addition, the survey indicated a dramatic improvement in machine life, production, operator safety, product quality and overall profitability. 

One of the manufacturing challenges with a full-system cleanout, is the need to interrupt manufacturing. Some fabs have installed totally redundant delivery systems, including dispense module and piping. Some adopt a scheduled downtime for system maintenance. Most simply refuse to recognize the need until disaster strikes in the form of unscheduled interruption of slurry delivery or dramatic increase in wafer defects. 

Is the process reliable The technology should not have excessive downtime due to scheduled and unscheduled maintenance. 

Catastrophic electrical failures Unscheduled electrical outages or shutdowns Chronic electrical problems in a piece of equipment or process Excessive steam usage Frozen or plugged product transport lines An inability to predict failures accurately Inefficient use of downtime maintenance opportunities Friction failures in rotating equipment... 

Downtime includes all sources of delay or degraded status, including scheduled and unscheduled maintenance, waiting to parts, personnel or eqnipment. 

The major downside of reactive maintenance is unexpected and unscheduled equipment downtime. If the equipment fails and repair parts are not available, delays ensue while parts are ordered and delivered. When this is the sole type of maintenance practised, both labour and materials are used inefficiently. Labour resources are thrown at whatever breakdown is most pressing. A purely reactive maintenance programme ignores the many opportunities to influence equipment survivability. However, it can be effective if used selectively and performed as a conscious decision based on the results of an RCM analysis. Equipment that can be reactively maintained must be non-critical and will not pose any serious hazards or affect the operation of the system as a whole. 

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