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Data Integration

Modern risk assessment requires use of many types of data. While not every risk assessor needs deep knowledge of database architecture, specialize software such as GIS, or various software languages to more efficiently utilize data, some basic knowledge makes the practitioner more efficient in his work.

Topics examined here include:

The focus here is on tools, tips, lessons learned, etc to help risk assessments progress most efficiently. A full chapter on Data Management is available, as are additional resources around using the data in the risk assessment process–the mechanics of the risk assessment.

Introduction

A great deal of information is usually available in a pipeline operation and pertinent to a risk assessment. A foundational element of this risk assessment methodology is that all available information be utilized appropriately. There will often be potentially conflicting indications that must be sorted out.

Information that can routinely be used to create and update the risk assessment typically includes

  • All survey results such as pipe-to-soil voltage readings, leak surveys, patrols, depth of cover, population density, etc.
  • Documentation of all repairs
  • Documentation of all excavations
  • Operational data including pressures and flow rates
  • Results of integrity assessments (ILI, pressure testing, etc)
  • Maintenance reports
  • Updated consequence information
  • Updated receptor information—new housing, high occupancy buildings, changes in population density or environmental sensitivities, etc.
  • Results of root cause analyses and incident investigations
  • Availability and capabilities of new technologies.

A special section on Inspections and Assessments discusses the many ways in which these especially-rich sources of information are utilized in risk assessment.

Sources of Information

In addition to sources listed above, don’t forget important maintenance- and reliability-related sources such as:

  • Design documents
    • Predicted loads/stresses
    • Safety factors
    • The design process is an exercise in risk management
  • HAZOPS
  • PPM
    • ID failure mechanisms
    • segmentation strategy
    • failure rate determinations
  • Spill prevention plans
  • PHA
  • Emergency response plans
    • discharge scenarios
    • volumes
    • ignition potential
    • reaction times
  • Specialized studies
    • Fatigue cracking
    • Surge analyses
    • Geohazard
    • PHA/HAZOPS

 

Multiple Uses of Same Information

Information importance is even more amplified when it informs multiple elements of the risk assessment at the same time. It is often the case that individual pieces of data impact several different aspects of risk, therefore it is not unusual for a single piece of information to be used in multiple ways in a risk assessment.

Let’s say you know something simple about the soil type—where it’s rocky and where it’s mostly clay. Some of the risk factors that can be strongly influenced by just this simple piece of information include:

  • Potential soil moisture content, impacting corrosivity estimate
  • Likelihood of past coating damages during installation
  • Propensity of future coating damages to occur
  • Dispersion of liquid spills—infiltration vs surface flow
  • Amount of potential harm to certain receptors (for example, aquifers vs surface flow)
  • Exposure to third party excavation damages
  • Exposure to certain geotechnical phenomena (for example, subsidence, shrink/swell, landslide, etc)

As another example, pipe wall thickness is a factor in almost all potential failure modes: It determines time to failure for a given corrosion rate, partly determines ability to survive external forces, and so on. Population density is a consequence variable as well as a third-party damage indicator (as a possible measure of potential activity). Inspection results yield evidence regarding current pipe integrity as well as possibly active failure mechanisms. A single detected defect can yield much information. It could change our beliefs about coating condition, CP effectiveness, pipe strength, overall operating safety margin, and maybe even provides new information about soil corrosivity, interference currents, third-party activity, and so on. All of this arises from a single piece of data (evidence).

Another example of multiple uses of info: Product flowrates. The flowrate tells us something about 4 different kinds of exposures (threats): internal corrosion, erosion, surge, waterhammer

Many companies now avoid the use of casings. But casings were put in place for a reason. The presence of a casing is a mitigation measure for external force damage potential, but is often seen to increase corrosion potential. The risk model should capture both of the risk implications from the presence of a casing.

Perhaps you can think of more. In this example, a single piece of information—a simple soil characteristic; rock vs clay—has influenced seven different risk variables.

proximity to roads, railroads, other pipelines has both probability and consequence implications.

Test of Time Evidence

In the absence of more compelling evidence, an appropriate starting point for the exposure estimation may be the fact that a component or collection of components has not failed after x years in service. This involves the notion of having ‘withstood the test of time’. A component having survived a threat, especially for many years, is evidence of the exposure level. This is best illustrated by example. If 10 miles of pipe, across an area with landslide potential, has been in place for 30 years without experiencing any landslide effects, then a failure tomorrow perhaps suggests an event rate of 1/(10 miles x 30 years) = 1/300 mile years.

This simple estimate will not address the conservatism level. The estimator will still need to determine if this value represents more of a P50 estimate or perhaps a more conservative P90+ value.

In many cases, the evidence is actually of the mitigated exposure level. That is, the component has survived the threat, but perhaps at least partially due to the presence of effective mitigation. This makes the separation of exposure more challenging.

Despite the lack of complete clarity, this ‘test of time’ rationale can be a legitimate part of an exposure estimate.

Absence of Information

Gaps in knowledge are unavoidable. As noted in mechanics of risk assessment, gaps are so ubiquitous that they should be planned for in the risk assessment processes.

Handling Uncertainty

Assessing risk means measuring risk. All measurements have uncertainty. There are many forms of uncertainty caused by aspects such as accuracy limitations and natural variation in the thing being measured. Acknowledgement of the uncertainty in a risk assessment and how that uncertainty pertains to risk estimates are both essential elements of modern risk assessments. See full discussion here.

Age as Risk Input

Age is rarely a direct indicator of risk. It does, however, suggest indirect risk indications related to issues such as era of manufacture/construction and extent of degradation where time-dependent mechanisms are active. Location-specific failure probability is best estimated by assessment of relevant exposure, mitigation, and resistance characteristics at that location and system-wide deterioration is best estimated by accumulating all location-specific damage potentials. The more useful risk assessment will evaluate the actual mechanisms possibly at work at any location and then supplement this with population statistical data.

While age is often used as a gross indicator of leak/break likelihood, especially on distribution systems where some amount of leakage is tolerable and is tracked over time, neither age nor historical leak rates indicate the presence of degradation mechanisms at any specific location.

In the special instances where age is a useful indicator of risk, age-based or historical leak-rate based estimates are readily generated when data is available and may be useful for initial risk estimates. Statistical examination of historical leak and break data provides insights into behaviors of populations of components over long periods of time. When such populations are similar in characteristics and environment to a collection of components being assessed, such statistical analyses have some predictive capability. This is often an approach for general predicting of leaks in larger distribution systems.

GIS

Elevation Data

Important for a variety of risk implications, including:

  • Potential accumulation points for internal corrosion
  • Drain down calculations (spill size)
  • Hydrostatic pressure changes
  • Leak detection

Measurements vs Estimates and Other Needs for Parallel Tracks

To address multiple information sources (multiple evidence sources), there should be parallel ‘tracks’ for quantification based on measurements vs estimates based on known or assumed characteristics. For instance, external corrosion rates (mpy) may be measured via coupons or successive wall thickness measurements. They may also be estimated based on soil chemistry and pipe material properties.

The recommendation is to include both in the risk assessment. Each track–measurements vs estimates–produces a value for mpy which should be adjusted for confidence. With a fair and consistent application of this adjustment, the more optimistic value can govern. That way, more reliable information can override the less reliable. See more.

Measurements and Statistics

Risk assessment is a measurement of risk. All measurements carry uncertainty. Statistics helps us understand that uncertainty.

See also: Data Management, Inspections/Assessments, Data Myths