A modern risk assessment will include dozens if not hundreds of inputs. This is necessary to ensure that even the normally-rare phenomena are included. Many inputs will be insignificant risk contributors (or limiters) but should nonetheless be included. This at least documents thoroughness and completeness but also ensures that aspects of risk are not prematurely dismissed.
See more discussion under Data Integration, Evidence, Measurements vs Estimates, Intelligent Simplification, List of Exposures, and others.
Sensitivity analyses are challenging for risk assessments. Inputs appearing more often in algorithms and/or higher in a flowchart hierarchy will generally have a bigger impact on risk estimates. However, normally insignificant inputs can sometimes be the largest contributors to the dominant risk at a location. Consider for example landslide potential in the US. The vast majority of US pipelines have an insignificant potential for failure by landslide but, in some location-specific scenarios, landslide-induced failure will be the dominant failure mechanism. This is also why the use of weightings is strongly discouraged. Furthermore, even if a pipeline system being assessed is free from such potential, a to-be-acquired asset may have that vulnerability and the risk assessment should catch that.
This list includes probability-of-failure variables covering exposure, mitigation, and resistance, and many aspects of consequence potential, including harm to receptors and commercial damages. Included are commonly mandated (by US regulators) risk assessment inputs and some that will be extremely rare phenomena for most pipelines. Note again the caution against removing inputs prematurely–better to include and ‘zero them out’ rather than remove from the assessment.
Following is a sample list of inputs into a risk assessment with brief definitions included.
| pipe_diam | nominal pipe diameter, in; assignment based on largest reported diameter in data |
| pipe_wall_nom | nominal pipe wall thickness, in; assignment based on smallest reported in data |
| NOP | normal operating pressure |
| MAOP | max pressure |
| pipe_SMYS | specified minimum yield strength, psi |
| pipe_date1 | pipe date of manufacture |
| pipe_date2 | pipe date of installation |
| pipe_wall_reinforce | pipe sleeves; wraps; etc |
| casing | binary: is pipe cased |
| product | product transported |
| aerial | convert burial/aboveground status into binary EAC factor |
| impct offshore | offshore sinking objects that might strike pipe |
| impct_buildings | buildings and structures falling on pipe ROW |
| impct_trees | trees falling on ROW |
| impct_utility poles | utility poles falling on pipe ROW |
| impct_other | other falling-type impacts to pipe ROW |
| vehicles_air | exposure: hit rate from aircraft,events/mi-yr |
| vehicles_auto | exposure: hit rate from ground vehicles, events/mi-yr |
| vehicles_rail | exposure: hit rate from rail traffic, events/mi-yr |
| vehicles_marine | exposure: hit rate from watercraft, events/mi-yr |
| Detonations | exposure: hit rate from nearby ground shocks/vibrations such as from seismic investigations, events/mi-yr |
| barriers_nat | mitigation: natural barriers that prevent impact on pipe |
| barriers_manmade | mitigation: man-made barriers that prevent impact on pipe |
| mech_prot | protection from external impacts (pavement, etc) |
| depth2 | depth cover from CIS |
| activity_landuse | exposure: event rate from activities linked to landuse (agriculture, construction, etc) |
| activity_excav | exposure: event rate from excavation activities |
| activity_agri | exposure: event rate from agricultural activities |
| pub_ed | benefit of public education in reducing exposure from thd pty |
| one_call | effectivness of one-call in reducing excavation exposures |
| patrol_method | effectiveness of patrol in reducing external force exposures |
| patrol_freq | benefit of patrol frequency |
| signs_markers | effectiveness of signs/markers in reducing ROW exposures |
| warning_tape_mesh | effectiveness of subsurface markers in reducing exposures |
| ROW | benefit of ROW condition in reducing exposure from thd pty |
| Max_wall_factor | see context |
| Crit_wall_thickness | related to thickness beyond which puncture becomes nearly impossible |
| source press | max pressure connected to pipe (regardless of regulating or safety devices) |
| MOP potential | frequency/magnitude of events that cause MOP exceedance |
| surge_prob | probability of surge event |
| surge_max | maximum pressure generated by surge event |
| training | effectiveness of training programs in reducing human error events |
| procedures | benefit of procedures in reducing exposure to inc ops |
| safety sys | effectiveness of safety devices/systems considering fail modes covered, redundancies, etc |
| mech error preventers | use of human-error preventors |
| SCADA | exposure reduction through formality of communications and monitoring |
| PHA | process hazard analysis, a type of risk assessment that potentially reduces human error potential |
| substance abuse | effectiveness of sub abuse programs in reducing human error events |
| sab history | exposure variable, threat of sabotage; history of attacks or threats |
| sab external threat | exposure variable, threat of sabotage; threat from outside company |
| sab internal threat | exposure variable, threat of sabotage; threat from inside company |
| sab opportunistic | exposure variable, threat of sabotage; chance of random, opportunistic event |
| sab access | mitigation variable, threat of sabotage; ease of access |
| sab fence | mitigation variable, threat of sabotage; ability of fence to deter attacks |
| sab visibility | mitigation variable, threat of sabotage; ability of visibility to deter attacks |
| sab lighting | mitigation variable, threat of sabotage; ability of lighting collection to deter attacks |
| sab patrol | mitigation variable, threat of sabotage; ability of patorl and monitoring to deter attacks |
| sab community | mitigation variable, threat of sabotage; ability of community partnering to deter attacks |
| sab intelligence | mitigation variable, threat of sabotage; ability of intelligence collection to deter attacks |
| geo scour | exposure: event rate from scour, hits/mi-yr |
| geo flood1 | exposure: event rate from flood, data source#1, hits/mi-yr |
| geo flood2 | exposure: event rate from flood, data source#2, hits/mi-yr |
| geo flood3 | exposure: event rate from flood, data source#3, hits/mi-yr |
| geo erosion | exposure: event rate from erosion, hits/mi-yr |
| geo wave_current | exposure: event rate from wave, current action, hits/mi-yr |
| geo hydraulic mit | mitigation: consider cover, anti-buoyancy, anchors, anti-scour, etc |
| geo settlement | exposure: event rate from settlement, hits/mi-yr |
| geo aseismic faulting | exposure: event rate from aseismic faulting, hits/mi-yr |
| geo landslide | exposure event rate from landslides |
| geo fire | exposure event rate from fires |
| geo faulting | exposure: event rate from faulting, hits/mi-yr |
| geotech mit | mitigation: consider cover, anchors, monitoring, etc |
| wthr freeze exp | frequency of freeze-related load exposure with no mitigation applied |
| wthr freeze mit | mitigation: sum effect of all reductions to freeze exposure |
| wthr snow exp | frequency of snow load exposure with no mitigation applied |
| wthr snow mit | mitigation: sum effect of all snow load exposure reductions |
| wthr lightning | frequency of potentially damaging lightning strikes |
| wthr ice_hail | frequency of ice/hail load exposure with no mitigation applied |
| wthr windstorm | frequency of wind load exposure with no mitigation applied |
| wthr frost heave | frequency of potentially damaging soil mvmnts due to frost action; mitigation included |
| wthr other mit | benefits from other types of mitigation against weather related exposures |
| elec_isol | amount of electrical isolation of pipe from soil, if casing, assume both atm and galv corr are occuring |
| atm_corr_general | general atmospheric corrosivity |
| atm_corr_special | atmospheric corrosivity under special conditions (under insulation, tree sap, splash zone, etc) |
| buried_environ_soil_corrosivity | soil corrosivity: base value; perhaps from resistivity measurements |
| buried_environ_soil_corr_moist | soil corrosivity: contribution from moisture content |
| buried_environ_soil_corr_MIC | soil corrosivity: contribution from bacterial activity |
| buried_environ_soil_corrosivity_pH | from surrgo |
| AC Induced Prob | probability of AC induced corrosion |
| AC_potential | mpy of AC induced corrosion |
| AC_mit | reduction in AC induced corrosion derived from installed mitigation |
| CP_ineff_meas1 | ILI-measured freq of gaps in coverage; 999=no ILI |
| CP_ineff_meas_confid1 | include age of meas |
| CP_ineff_meas2 | CP gap freq measured by CIS |
| CP_ineff_meas3 | CP gap freq measured by CIS–no anomaly found |
| CP_ineff_est | assumed CP gap rate; prob of one or more gaps in CP coverage per unit length, based on experience with all avail info |
| CP_effectiveness_rectifier_oos | reduction in CP effectiveness due to rectifier out of service periods |
| CP_effectiveness_P-S_criteria | effectiveness of CP: robustness of acceptability criteria for pipe-soil voltage readings |
| CP_effectiveness_P-S_dist | effectiveness of CP: distance from last pipe-soil voltage reading |
| CP_effectiveness_P-S_reading | effectiveness of CP: acceptability of last pipe-soil voltage reading |
| CP_effectiveness_P-S_date | effectiveness of CP: date of last pipe-soil voltage reading |
| CP interference DC source | % red in CP eff based on minutes per yr interruptions in CP per ft2 of steel and cast iron within buffer of track(s) |
| CP_interference_DC_mit | benefits from mitigation of DC source interference |
| coating_ext_cond_fail_disbond | propensity of ext coating to become disbonded and shield CP |
| coat_def_new_est | rate of emergence of new coating defects, per mile-year |
| coat_def_ext_est | estimated holiday rate for coated steel or cast iron pipe |
| coat_def_ext_est_confid | confid in coat holiday rate |
| coat_def_ext_meas | ILI measured holiday rate for coated steel or cast iron pipe |
| coating_ext_insp_date | date of inspection of external coating |
| coat_def_ext_meas2 | measured holiday rate for coated steel or cast iron pipe |
| coat_def_ext_meas_confid2 | confid in coat holiday rate |
| coating_ext_insp_date2 | date of inspection of external coating |
| coat_def_ext_meas3 | measured holiday rate for coated steel or cast iron pipe |
| coating_ext_insp_date3 | date of inspection of external coating |
| corr ext mpy meas | measured at ILI anomaly |
| corr ext mpy meas confid | confidence in measured corr rate value and applicability to segment of interest |
| corr ext mpy meas2 | measured at ILI non-anomaly |
| corr ext mpy meas confid2 | initial confid then % loss of confid per year since ILI date |
| corr ext mpy meas3 | rate measured in DA |
| corr ext mpy meas confid3 | external corrosion rate as measured (by coupon, probe, successive NDE, etc) |
| prod corr general | summation of product stream factors that add to corrosivity; each is modeled to independently add to the potential damage rate |
| int corr crit angle | mpy int corr due to exceedance of critical angle (liq/solid holdup) |
| int corr velocity | mpy int corr due to liquid/solid depositions and lack of sweep |
| int corr flow regime | mpy int corr due to liquid/solid depositions and lack of sweep |
| Prob of Accumulation Point_ILI | triggered by ILI anomaly |
| corrosivity_product_ILI | triggered by ILI anomaly |
| int corr contam episodes | mpy due to excursions in int corr prevention systems |
| int corr prob upset | prob of int corr contaminant excursion |
| erosion | mpy of wall loss from fluid/solid impingement, mechanical wear |
| internal_corr_mitigation_chem_inhib | chem treatment to reduce product corrosivity |
| internal_corr_mitigation_coat | internal coating |
| internal_corr_mitigation_filtering | filtering of corrosive components |
| internal_corr_mitigation_pigging | maint pigging to sweep accumulations |
| corr int mpy meas | internal corrosion rate as measured (by coupon, probe, successive NDE, etc) |
| corr int mpy meas confid | confidence in measured corr rate value and applicability to segment of interest |
| corr int mpy meas2 | internal corrosion rate as measured (by coupon, probe, successive NDE, etc) |
| corr int mpy meas confid2 | confidence in measured corr rate value and applicability to segment of interest |
| corr int mpy meas3 | rate measured in DA |
| corr int mpy meas confid3 | initial confid then % loss of confid per year since assess date |
| cycles int press | count of cycles from int pressure fluctuations |
| pct_SMYS_int_press | magnitude of cycles from internal pressure fluctuations |
| fatigue_resis | reduction in potential crack growth due to thicker wall pipe and possible presence of stress contributors |
| crack_growth_base_int | mpy base rate of cracking due to internal pressure cycle |
| cycles external | count of cycles from external loadings |
| pct_SMYS_ext | magnitude of cycles from external loadings |
| crack_growth_base_ext | mils/cycle; increase in crack growth rate due to ILI w no anomaly |
| cycles oscillations | count of cycles from pipe movements |
| pct_SMYS_oscill | magnitude of cycles from pipe movements |
| EAC_Hist | mpy implied by history of EAC |
| EAC_base | mpy EAC base rate |
| EAC_colony | mpy added by crack colony density |
| EAC_coal | mpy added by crack coalenscence potential |
| crack mpy meas | crack rate as measured (by successive NDE, etc) |
| crack mpy meas confid | confidence in measured crack rate value and applicability to segment of interest |
| crack mpy meas2 | crack rate as measured (by successive NDE, etc) |
| crack mpy meas confid2 | confidence in measured crack rate value and applicability to segment of interest |
| pipe_SMYS_ML | actual or conservative est (highest plausible SMYS leads to thinner wall est) |
| surviving_defect_fctr | adjustment to Barlow-inferred wall thickness to allow for surviving defects at this pressure; % red in pipe eff wall; eg, 0.9 = 10% reduction in theoretical wall thickness due to potential surviving defects |
| test_press | pressure test pressure level |
| test_date | pressure test date |
| pipe_wall_meas_ILI_depth | depth of metal loss expressed as % of pipe wall, measured by ILI |
| pipe_wall_meas_ILI | wall thickness measured by ILI |
| pipe_ERF | effective repair ratio (or RPR or other); pipe rupture pressure ratio; usually from ILI |
| integ_insp_date_ILI_ml | date of ML ILI |
| pipe wall meas accuracy metal loss ILI | metal loss detection accuracy associated with ILI |
| pipe_wall_meas_metal_loss_NDE | pipe wall remaining after metal loss as measured by NDE |
| pipe wall meas accuracy metal loss NDE | metal loss detection accuracy associated with NDE |
| integ_insp_date_NDE | date of inspection: NDE (physical contact on pipe) |
| pipe wall meas crack ILI | pipe wall remaining after cracking, as measured by ILI |
| pipe wall meas accuracy cracking ILI | crack detection accuracy associated with ILI |
| integ_insp_date_ILI_crk | date of crack ILI |
| pipe wall meas crack NDE | pipe wall remaining after cracking, as measured by NDE |
| pipe wall meas accuracy crack NDE | crack detection accuracy associated with NDE |
| pipe_flaw_repair_hist | possible pipe weakness; substandard repair practices |
| pipe_flaw_crk | possible pipe weakness; manufacture flaw in pipe seam |
| pipe_manufact | possible pipe weakness; substandard manufacturing process |
| pipe_toughness | possible pipe lack of toughness as part of ‘effective’ pipe wall calculation; assumption is that toughness property is less certain for pipe manufactured prior to 1975 |
| pipe_appurt | possible pipe weakness; substandard appurtenance |
| pipe_construct | possible pipe weakness from construction methods |
| pipe_buckle | possible pipe weakness; buckle |
| pipe_joint | possible pipe weakness; substandard joint type |
| pipe_span | possible pipe weakness due to stress from span |
| pipe_wrinkle_bend | possible pipe weakness; wrinkle bends present |
| pipe_ext_load | possible pipe weakness; excessive external loading |
| pipe_flaws_anom | from ILI |
| pipe_wk_emerge_rate | may require pairing specific weakness types with insp/test types |
| pipe_flaw_body-new | emergence rate of new weaknesses of this type |
| pipe_flaw_seam-new | emergence rate of new weaknesses of this type |
| pipe_flaw_repair_hist-new | emergence rate of new weaknesses of this type |
| pipe_appurt-new | emergence rate of new weaknesses of this type |
| pipe_construct-new | emergence rate of new weaknesses of this type |
| pipe_buckle-new | emergence rate of new weaknesses of this type |
| pipe_girthweld-new | emergence rate of new weaknesses of this type |
| pipe_span-new | emergence rate of new weaknesses of this type |
| contam area | hazard zone (radius) caused by contamination by released product |
| HCA_ESA_units | number of ‘units’ of this receptor |
| HCA_OPA_units | number of ‘units’ of this receptor |
| HCA_HPA_units | number of ‘units’ of this receptor |
| HCA_DW_units | number of ‘units’ of this receptor |
| HCA_NW_units | number of ‘units’ of this receptor |
| HCA_ESA_damage_rate | HCA-type-weighted average damage rate per HCA unit |
| HCA_OPA_damage_rate | HCA-type-weighted average damage rate per HCA unit |
| HCA_HPA_damage_rate | HCA-type-weighted average damage rate per HCA unit |
| HCA_DW_damage_rate | HCA-type-weighted average damage rate per HCA unit |
| HCA_NW_damage_rate | HCA-type-weighted average damage rate per HCA unit |
| pop_class_units | CFR49 Part 192 population class categories |
| pop damage rate | fraction of units damaged or extent of damage per unit |
| Prop val | unit value of this receptor |
| Prop damage rate | fraction of units damaged or extent of damage per unit |
| Environ units | number of ‘units’ of this receptor |
| Environ val | unit value of this receptor |
| Environ damage rate | fraction of units damaged or extent of damage per unit |
| pop_roads | population density on roadway |
| pop_census | population density per US census |
| product val | value per unit volume of product transported |
| vol deinventory | volume that would drain to release point |
| vol shutin | volume that would move to leak site prior to system shut in |
| repair costs | total repair costs incl return-to-svc costs (inspection, etc) |
| service interruption costs | contract penalties, etc |
| outage cost/period | value of lost transport revenue |
| outage period | time period of transport service interruption due to incident |
| production interrupt period | time period of production interruption due to incident |
| production interruption cost/period | value of lost production due to outage |
| CoF indirect | damage to corp reputation; increased regulatory oversight; legal costs; etc |