Critical repair

Clearly define a process for delaying maintenance and capital work in the event of budget constraints. Critical repair work should not be delayed. Environmental, Safety, and Health reviews should be conducted on delay of scheduled mechanical integrity program inspections. (Before startup)... 

The failure mode of an equipment item describes the reason for the failure, and is often determined by analysing what causes historic failures in the particular item. This is another good reason for keeping records of the performance of equipment. For example, if it is recognised that a pump typically fails due to worn bearings after 8,000 hours in operation, a maintenance strategy may be adopted which replaces the bearings after 7,000 hours if that pump is a critical item. If a spare pump is available as a back-up, then the policy may be to allow the pump to run to failure, but keep a stock of spare parts to allow a quick repair. 

Breakdown and subsequent repair is clearly non-scheduled, but gives rise to nonavailability of the item. Some non-critical items may actually be maintained on a breakdown basis, as discussed in Section 11.3. Flowever, an item which is critical to keeping the production system operating will be designed and maintained to make the probability of breakdown very small, or may be backed up by a stand-by unit. 

This header has undergone repair after through-thickness cracking of an assembly weld after 108.000 hours of service, it is presently in operation and periodically submitted to ultrasonic inspection during planned maintenance shutdown. Continuous on-line AE monitoring of the integrity of critical welds is expected to contribute supporting continued and safe operation of the header until its replacement, platmed to take place in 1999. 

Implantable valves, particularly mechanical valves which continue to encroach on tissue valves, are unique. Methods such as valvuloplasty, mitral valve repair, or use of ultrasound are unlikely to reduce the number of valve replacements into the twenty-first century. Valve selection remains in the hands of the surgeon because of the critical nature of the procedure. If anything goes wrong, the result can be catastrophic to the patient. Cost of a valve, from 3000— 4000, is a relatively small part of the cost of open-heart surgery which can mn as high as 30,000. Growth of the cardiovascular valve market has slowed in the United States with the decline of the threat of rheumatic fever. 

Bonded patch Flat or curved surface field repair Not suitable for high temperature or critical parts Fast but depends on cure cycle of adhesive Low to medium... 

Inspection and repair provided in the section titled Recommended Practice for Maintenance and Use of Drilling and Well Servicing Structures are extremely critical under low-temperature conditions. Masts should be maintained in excellent condition. 

Computers, like plant equipment, fail. Therefore, the use of a commercially available computer is recommended. The critical considerations include availability of repair parts and local vendor support. 

As a minimum, your baseline data set should include the labor, overhead, overtime premiums and other payroll costs of the maintenance department. It should also include all maintenance related contract services, excluding janitorial, and the total costs of spare parts inventories. The baseline should also include the percentage of unscheduled maintenance repairs versus scheduled actual repair costs on critical plant equipment and the annual availability of the plant. 

Class 11 or critical machinery would severely limit production capacity. As a mle-of-thumb, loss of critical machinery would reduce production capacity by 30 per cent or more. Also included in the critical classification are machines or systems with chronic maintenance histories or that have high repair or replacement costs. 

If sufficient data are available, much more information can be provided when different curves for various percentages of failure are plotted. Where such data are available, reasonable design criteria would be based on some probability for failure, depending on how critical the effects of failure occur. If a large, expensive repair of a complex mechanism would result from the fatigue failure of one product, then a 10 or even 1 % probability of failure would be a more likely design criterion than the 50% suggested above. 

At the area between the breakdown potential Eb and the critical pitting potential pit local film breakdown occurs, which leads to the creation of pit nuclei. However, these nuclei are immediately repassivated. Consequently, in this potential region it is concluded that breakdown and repair are continuously repeated without creating pit growth. 

Maintenance embraces regular inspection, periodic examination by competent persons , and repairs. All maintenance on equipment used with chemicals should be properly planned and recorded. Maintenance operations, particularly those which are non-routine, require a sound system of work with strict administrative procedures, e.g. permit-to-work, to avoid risks arising from modifications to established safe practices. A permit-to-work should be used wherever the method by which a job is done is likely to be critical to the safety of the workers involved, nearby workers, or the public it is required whenever the safeguards provided in normal operations are no longer available. Examples include ... 

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