Piping failure incidents

Thirteen of the twenty-seven major refinery incidents reported from 1980 to 1995 in the large property damage report were piping failures. Six of twenty-four major petrochemical plant major incidents were the result of tube or piping failures or improper maintenance procedures involving valves. Recent examples of piping failures which resulted in massive fires or explosions follow. 

At Zaporozhe NPP, protection of the primary circuit against overpressure during incidents is provided by three safety valves on the pressurizer For Units 1 to 4, only one valve can be opened intentionally by actuating pilots from the control room and the emergency control room The other two safety valves are acting as passive pilot operated safety valves For Units 5 and 6, they have a new design of valves All the pilots of the safety valves can be actuated from the control rooms The pilots can be isolated by an additional pilot in case of impulse pipe failure The qualification of safety valves for water flow is not confirmed... 

Loss of radiator capability could be caused by heat pipe failure, reduction of radiator emissivity, and/or incident radiation. All three of these events will reduce the amount of heat rejected by the HRS and increase the HRS fluid temperature at the gas cooler inlet. This decreases the amount of heat transferred from the primary to the secondary coolant and increases the gas temperature at the compressor inlet, decreasing system efficiency. Margin would be built into the radiator area to offset this concern. Control action such as changes in HRS pump speed may also be used. 

Systems analyses are like formulas, they have little usefulness until the variables are assigned probabilistic numbers from nuclear or chemical data bases. These data concern the probability of failing vessels, pipes, valves, instruments and controls. The primary difference between chemical and nuclear data is that the former may operate in a more chemically active environment, while the later operate in radiation. This chapter addresses both, but most of the data were gathered for nuclear systems. It covers 1) failure rate databases, 2) incident databases, 3) how to prepare failure rates from incidents, and 4) human factors for nuclear and chemical analyses. 

This report is by Battelle Columbus Division to the Line Pipe Research Supervisory Committee of the American Gas Association. It presents an analysis of statistical data obtained from reports of lea)c or rupture (service) incidents and test failures in natural gas transmission and gathering lines over the 14.5 year period from 1970 through June, 1984. All gas transmission companies were required to notify the Office of Pipeline Safety Operations in the event of a "reportable" incident, as defined by the Code of Federal Regulations. The purpose of the study is to organize the reportable incident data into a meaningful format from which the safety record of the industry can be assessed. 

A mismatch between operator procedures and the automatic control system of the reactor (see also Table 17) was the first active failure identified in this scenario. This precursor was still present mainly due to a shortage of people. Literally it was said that the pressure relief valve would open if the wrong value was inserted into the reactor s control system. The second precursor was the failure of the pressure relief valve (see also Table 17), which was not known to the responsible person who decided to ignore the difference between procedures and control system. The pressure relief valve failed, because resins stuck in the valve after it was used for the first time. Consequently the second time the valve was opened it was at a much higher pressure due to the build up of resins in the valve. If this second precursor had not been observed in time by damp on the pipes situated above the pressure relief valve or by the alarms in the control room a possible accident scenario existed. This was especially dangerous as the alarms in the control room are often ignored because of the high incidence of false alarms (see also Table 17), which was the third precursor present. 

BLEVE types of incidents arise from the reduction in yield stress of a vessel or pipe wall to the point that it cannot contain the imposed stresses by the design and construction of the container and are also influenced by the relief valve set point. This results in a sudden catastrophic failure of the containment causing the violent discharge of the contents and producing a large intense fireball. 

Normally where it is necessary, fireproofing is preferred over water spray for several reasons. The fireproofing is a passive inherent safety feature, while the water spray is a vulnerable active system that requires auxiliary control to be activated. Additionally the water spray relies on supplemental support systems that may be vulnerable to failures, i.e., pumps, distribution network, etc. The integrity of fireproofing systems is generally considered superior to explosion incidents compared to water spray piping systems. The typical application of water sprays in place of fireproofing is for vessel protection. 

While the Challenger disaster was not a process incident in the strictest sense, the nature of the failure was similar to many piping system failures that typically occur in the process industries. More importantly, organizational failure was a fundamental cause of the incident. This case study serves as a classic example of the type of loss that can occur in a large complex organization if management systems are not effective. 

Piping and Instrumentation Diagram Probability of Failure on Demand Process Hazard Analysis Pressure Indicator Protection Layer Preventive Maintenance Process Safety Incident Database Process Safety Management Pressure Safety Valve (Relief Valve)... 

But, all of these obvious technical pipeline considerations are sometimes overh>oked, and many of the most infamous incidents have involved poor practices in piping design, in operations, or in piping maintenance systems. The American Insurance Association states Piping hazards are often underrated as compared to pressure vessels although the history of failures does not warrant this... . Piping systems should be located in. serviceable areas. They should be constructed in accordance with appropriate code requirements and inspected by appropriate means.. .. [20]... 

System failures which could have fed to an incident (e.g., instrument had failed, pipe wall thickness is low). 

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