G.K. Hodjaeva

research associate of Geoecological Studies Scientific Laboratory of Nizhnevartovsk State Humanities University

 

INDUSTRIAL SAFETY ASSURANCE IN MAIN OIL pipeline OPERATION

 

 

Keywords: pipelines, safety, emergencies, damage, risk

 

ABSTRACT. This Article highlights main pipelines’ safety, gives potential emergency rusk assessment in Nizhnevartovsk district intrafield pipelines and presents the distribution of random number of emergencies per month and per day in accordance with Poisson’s law.

 

Oil-pipeline system in the Russian Federation fuel and energy system. Length of main oil pipelines in Russia is nearly 50,000 km. [4]. Key elements include pipelines, pump stations, and tank farms. Oil movement in the pipeline is 10-12 km/h. Main oil pipeline nomenclature includes 387 oil-pumping stations, tank farms with the total capacity of 17 million cubic metres.

Main oil pipelines are long structures, their routes cross forests, tundra areas, rivers, lakes, bogs, ditches, railways and motorways, underground utilities lines and other natural barriers.

Oil and oil-products pipeline transport is accompanied by emergencies related to pipeline ruptures and oil and oil-products spills resulting from pipes’ corrosion, non-observance of performance characteristics in construction and operation, foundations’ destruction etc. Pipeline emergencies result in severe environmental consequences – long-standing soil and water-reservoirs’ pollutions [3].

To ensure integrity, safety and establish normal operation conditions “Rules of Main Pipelines Protection” were implemented. As per these Rules the so-called safeguard zone is set up as a strip of land limited by the lines passing 25 meters from the pipeline axis in each side. It is intended for staff access and inspection walk-around along the pipeline route as well as for performing works related to the pipeline availability assurance [5].

Age structure of the oil pipeline facilities’ fixed assets demonstrates their substantial depreciation [4]. Most often emergency oil spillovers result for field pipelines’ leaks.

In 2006 [7] at the district oil-field networks 4718 oil/oily mixture/mineralized water spillovers were registered, including 2294 emergencies in the pipelines and 2424 in the water conduits. As a result, contamination area made 279.3 hectares, environments emissions amounted to 19.9 ktons pollutants.

Most of the pipeline emergencies result from pipe corrosion – on average 98%, construction and engineering defects; pipeline mechanical damage cause 1-2% of emergencies [10, p.56-59].

Climate changes also impact the pipeline condition. Ambient air temperature changes cause temperature changes of the soil in which the pipeline is laid. During the soils’ freezing and thawing these changes sometimes result in the pipeline destruction. Frozen wet grounds when thawing settle down significantly as a result of both soil compaction and reduced shear strength, hereby the more clay particles there are in the soil, the smaller is its shear resistance [5]. The non-uniform soil settlement resulting from the pipe weight bends the pipeline. Additional bending stresses in the pipeline accompanied by other unfavorable factors (like poor welding quality) usually results in the joints’ structural failures.

The main safety problem in oil and gas industry facilities’ still is low renewal rates of depreciated and obsolete equipment as well as lack of reliable automatic control and telemetric systems in the industry [6].

The equipment depreciation causes enhanced emergency and failure risk which, in its turn, results in moral losses, injuries and fatalities.

The main reason of fatalities in main pipeline facilities is gross violation of industrial safety rules by the companies’ management and staff during pipeline and equipment operation, maintenance and turnarounds.

Most typical industrial safety violations in main pipeline facilities are:

- non-observance of safeguard zones and minimum admissible distances to main pipeline facilities

- pipeline sections’ floodwater erosions and denudations in short pipelines

- main pipeline the pipe burial depth below the design values

- admission of unskilled staff to unsupervised work

- insufficient protection of the facilities against possible mechanical damage and acts of terrorism [2].

A key facility reliability indicator is no-failure operation probability P(t) in some time interval or reliability function. Function Q(t) =1-P(t), complementing P(t) to one and characterizing failure probability is a function of emergency (injury and/or damage) risk [1].

Damage evaluation is an essential component of industrial safety regulation, including industrial safety declaration and hazardous facilities’ insurance, because the solution to the emergency consequences’ mitigation (probability reduction) problem requires qualitative evaluation [5]. Quantitative determination of emergency damage in hazardous production facilities is the foundation for the emergencies accounting and registration based on unified economic indicators and efficiency analysis of the activities aimed at reducing emergency damage, people and environment safety assurance.

Emergencies’ forecasting is possible based on elementary statistics and discrete distribution of Poisson’s law frequently applied to rate events and natural phenomena. Such events make a sequence of events conventionally called a flow of events [9]. Suchlike data are of interest in making emergency risk mitigation decisions at the facilities.

Table 1 gives the assessment of the potential emergency risk  for different intervals (day, month, year, 2, 5, 10 years) in the intrafield oil pipelines of Nizhnevartovsk district (total length – 21,000 km). The calculation results show that emergency accidence function values increases with the time.

Table 1.

Emergency Accidence Function  values within τ period

τ

1 day

1 month

3 months

6 months

1 year

2 years

5 years

10 years

0

0.005

0.015

0.029

0.058

0.113

0.259

0.451

Fig. 1 shows the distribution of random number of emergencies per month (a) and per day (b) as per Poisson’s law. The analysis shows [8], that most probable number of emergencies per month is equal to 100 and similar per-day number is 3. Maximum expected number of emergencies per day does not exceed ten.

а)
 
a)

b)

Fig. 1. Distribution of Random Number of Emergencies per Month (a) and per Day (b) as per Poisson’s Law

The main accidence rate reduction activities are:

- laying corrosion-proof pipelines

- corrosion inhibitors’ application

- pipeline diagnosis with subsequent emergency sections’ replacement

- pipeline ground and electromechanical protection.

In order to ensure safe operation of oil-pumping stations and oil-storage depots, master plan layout and elevations of the buildings and structures under design [4] must be made observing fire-safety gaps, fire and explosion safety areas, laying process networks’ corridors based on transport communications as well as construction and maintenance conditions.

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