Failures pump repairs

The most common maintenance problem with centrifugal pumps is with the seals. Mechanical seal problems account for most of the pump repairs in a chemical plant, with bearing failures a distant second. The absence of an external motor (on canned pumps) and a seal is appeahng to those experienced with mechanical seal pumps. 

Failure and repair times for the pumps are provided in Table 1.14. 

Figure 5. An ET of primary pump failure without repair.

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. 

Repair and maintenance records were analyzed to determine failure rates and distribution of failure modes. Preliminary findings are reported which include the Weibull distribution characteristics. Failure mode distributions are approximate. Overall mean-time-between-failure is given for the kiln, leach tank, screwfeeder, tank pump, tank gearbox, and kiln gearbox. The study was confined to an analysis of unscheduled repairs and failures. 

SAIC Data Base Nudear Plant maintenance and repair records by system and component type selected basic event failure rates and unavailability Data mainly for pumps, valves, diesels, batteries, chargers, and heat exchangers 76. 

This data collection effort was concentrated on the following components because of their extensive populations and repair action documentation pumps, valves, electrical positioning devices, electric motors, and drives. For each component type, preface pages and data summary tables are provided. Separate data summary tables are provided for each component type and are structured in a format that allows for the inclusion of the number of pieces of operating equipment, the total number of operating hours, total number of failures, and hourly failure rates with upper and lower bounds. 

A starter is connected to a motor that is connected to a pump. The starter fails once in 50 yr and requires 2 hr to repair. The motor fails once in 20 yr and requires 36 hr to repair. The pump fails once per 10 yr and requires 4 hr to repair. Determine the overall failure frequency, the probability that the system will fail in the coming 2 yr, the reliability, and the unavailability for this system. 

AM. Fire brigade member reaches pump house and finds electric fire pump inoperable due to power failure, one diesel fire pump inoperable due to known mechanical problems, second diesel would not start due to dead batteries calls for maintenance help. Several maintenance employees dispatched to repair diesel fire pump No. 2. 

If initial SST fails, the analyst should stop the sequence immediately, diagnose the problem, make necessary adjustments or repairs, and re-perform SST. Analysis of actual samples should commence only after passing all SST limits, not only the failed criteria. Most SST failures are traced to problems from the autosampler, pump, column, or mobile phase (see Chapter 10 on troubleshooting hints). If one of the interspersed SSS injections fails, data from all samples after the last passing SSS become invalid and must be repeated.15... 

The hardware of an automated solid-phase synthesizer consists of all the electromechanical components of the system (reaction vessel, tubing, valves, pumps, detectors, power supplies, circuit boards, sensors, etc.). It is imperative that all these components are reliable and can operate without failure for many synthesis cycles before repair or replacement. Before using any component in an automated system, it should undergo compatibility and lifetime testing with the reagents that would be in contact during the synthesis. 

One difficulty with this type of model is that it is difficult to provide a probability value for an absolute repair time. For example, the Mean Downtime (MDT) for P-lOlB is 3 hours this is the time it takes to repair it when it fails. It may be that this time is an absolute minimum (say due to the time it takes to isolate the pump, drain it down, repair the failure, and bring the pump back into service). Hence a simple probability value cannot truly represent this downtime. 

Example 9.25 Treatment of the repair of a component as a Markov process A failure rate of = 97 x 10 h applies to a pump. The average time needed for its repair is known to be Tr = 5 h. T[Pg.375]

After the start of the emergency cooling system of a nuclear power station the radiation level drops to a value which permits a repair of the emergency cooling pump only after 48 h. It is assumed that the pump starts on demand. For its failure during operation a rate of Ji, = 42 x 10 h applies the average time for repair amounts to = 20 h. 

Pedal is low or soft master pump has failure Repair or replaee the master pump... 

Brake pump has failure. Brake assist has failure Improper vacuum degree The brake pipeline is blocked. Repair if necessary... 

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