Pump failure

A pump roller bearing failure in a crude oil refinery initiated the fracture of the motor shaft and the pump bearing bracket. The pump casing then broke, releasing hot oil, which au-toignited. Secondary pipe and flange failures contributed fuel to the fire. Plant damage totaled over 15 million. 

Because the pump was equipped only with manually operated suction-side valves, the valves could not be reached during the fire. 

16William G. Garrison, One Hundred Largest Losses A Thirty-Year Review of Property Damage Losses in the Hydrocarbon Chemical Industries, 9th ed. (Chicago Marsh McLennan Protection Consultants, 1986), p. 7. 

Automated block valves would have minimized damage in this fire. A good inspection and maintenance program would have prevented the accident. 

A drain fitting in a high-pressure (40 kpsi) compressor line broke, allowing ethylene to escape. The ethylene cloud drifted and entered the intake system of an engine that was driving one of the compressors. The ethylene detonated in the engine, and this explosion ignited the rest of the vapors. 

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Fig. 6. A fault tree for the pumped storage example of Figure 5. For a real system the tank and pump failures would be more precisely defined, or set as intermediate events having further definition by subsequent basic events and more detailed failure modes.

Both friction and wear measurements have been used to study boundary lubrication of fuel because sticking fuel controls and pump failures are primary field problems in gas turbine operation. An extensive research program of the Coordinating Research Council has produced a baH-on-cylinder lubricity test (BOCLE), standardized as ASTM D5001, which is used to qualify additives, to investigate fuels, and to assist pump manufacturers (21). 

Chlorine—hydrogen ha2ards associated with mercury cells result from mercury pump failures heavy-metal impurities, particularly those with very low hydrogen overvoltage, ie. Mo, Cr, W, Ni excessively low pH of feed brine low NaCl concentrations in feed brine and poor decomposer operation, which leads to high sodium amalgam concentrations in the cell. 

Elevated Tanks These can supply a large flow when required, but pump capacities need be only for average flow. Thus, they may save on pump and piping investment. They also provide flow after pump failure, an important consideration for fire systems. 

Overflows cause by pump failure or restrictions in discharge piping... 

A few of the above-menti I solutions to cavitation are almost. cal even cost effective. The idea is that they would work to reduce and stop < and the resulting seal, bearing and pump failure. Too many maint. (engineers and mechanics) are running around in circles, wring their h jumping up and down, trying to deal with cavitation. Who would have there are so many solutions, practical or not ... 

In order to solve a pump failure, we have to identify the cause. Once this is known, the problem can be dealt with and a permanent solution can be found. A logical thought process (common. sense) to identify the problem is as follows ... 

Whenever possible, external relief valves should be furnished. On the larger systems, this is mandatory. Internal relief valves will lead to pre mature pump failure if allowed to operate open for more than a few minutes, since the hot oil is returned directly to the suction. An upset period, the time when a pump may open the relief, is probably not the time when an operator would detect the open valve and shut the pump down to r< t the valve. 

Overpressure and tube failure may also result from valve closure on the inlet side of a fomace, or from feed pump failure, etc, if the coil remains pressurized by downstream equipment. In these cases, however, overpressure occurs at or below the normal operating pressure (due to overheating at no-flow conditions), and a PR valve cannot provide the necessary protection. 

If heat ean be removed as fast as it is generated by the reaetion, the reaetion ean be kept under eontrol. Under steady state operating eonditions, the heat transfer rate will equal the generation rate (see Figure 6-26). If the heat removal rate Qj. is less than the heat generation rate Qg (e.g., a eondition that may oeeur beeause of a eooling water pump failure), a temperature rise in the reaetor is experieneed. The net rate of heating of the reaetor eontent is the differenee between Equations 12-44 and 12-45. 

The main cause of pump failure, often accompanied by a leak, are ... 

In a batch reaction plant, an exothermic reaction was cooled by water circulating in a jacket. The circulating pump failed and the reactor went out of control causing a violent explosion. A low flow alarm was present but was inoperable. A critical pump bearing had not been lubricated during maintenance, and the collapse of the bearing had led to the pump failure. 

FIC8 = No Flow (new) Conditions are as specified. It must be inadequate cooling of column Top reflux pump failure (confirmed) Alternative goals Reduce heating in reboiler Reduce flow rate of input Increase cooling in condenser ... 

Consider how different systems might treat the following pump failures ... 

All of the above events would cause a pump failure over a period of time. Therefore, the events would qualify for inclusion in the failure rate. So, at one extreme there might be six catastrophic failures per sample time. However, a data analyst may decide that No. 2 is not a relevant failure since the cause was neither a function of the equipment nor the operational application, but was a mistake by an outside agent. The same might be said of No. 3. 

The book contains, in alphabetical order, failure rates, event rates and probabilities, and descriptive information which has been collected since 1970 in the course of doing risk and reliability assessments. Twenty appendices contain results of surveys on bursting discs, pipes, valves, relief valves, pump failures and information on human error, international fire losses, and blast effects. 

ATWS A Reappraisal, Part 3 Frequency of Unanticipated Transients Nuclear 200 pump failure events from Arkansas Nuclear Unit 1, Calvert Cliff Unit 1, and Indian Point Unit 3 nuclear plants Nuclear reactor coolant pump seals 102. 

NUMBER AND TYPE OF RECORDS 200 pump failure events from Arkansas Nuclear... 

For catastrophic demand-related pump failures, the variability is explained by the following factors listed in their order of importance system application, pump driver, operating mode, reactor type, pump type, and unidentified plant-specific influences. Quantitative failure rate adjustments are provided for the effects of these factors. In the case of catastrophic time-dependent pump failures, the failure rate variability is explained by three factors reactor type, pump driver, and unidentified plant-specific Influences. Point and confidence interval failure rate estimates are provided for each selected pump by considering the influential factors. Both types of estimates represent an improvement over the estimates computed exclusively from the data on each pump. The coded IPRDS data used in the analysis is provided in an appendix. A similar treatment applies to the valve data. 

Figure 6.9 Example Pump Failure Rate Summary. From Science Applications International Corporation.

Hazard, risk, failure, and reliability are interrelated concepts concerned witli uncertain events and tlierefore amenable to quantitative measurement via probability. "Hazard" is defined as a potentially dangerous event. For example, tlie release of toxic fumes, a power outage, or pump failure. Actualization of the potential danger represented by a hazard results in undesirable consequences associated with risk. 

Usually, dual oil pumps are included, so that one pump failure will not shut down the compressor-driver unit. The first or main pump may be driven by electric motor, and the standby steam or gas may be driven by turbine. Any combination is acceptable as long as the selection takes into account the specific local conditions and service reliability. Figures 12-50A-C show an overall assembly, including accessories. 

Formation of vapor bubbles in rapidly flowing or turbulent water causing risk of pumping failure and erosion and/or corrosion. Due to an increase in velocity at the pump head resulting in a localized pressure reduction and the subsequent collapse of the vapor into voids or cavities. Where FW temperatures are high (over perhaps 195-205 °F) the pump velocity can reduce FW vapor pressure below that corresponding to the temperature of the liquid and cavitation can occur accompanied by some noise. Warning of severe pump cavitation is often indicated by a heavy noise. 

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