Not a Drop of Oil to the Sea
Ram K Goyal, Risk and Reliability Management, Engineering Service Unit
Bahrain Petroleum Company (BAPCO)

The paper titled as - "Not a Drop of Oil to the Sea" - The Role Corrosion Engineers Have to Play in Delivering This Environmental Vision – bring forward an analysis that illustrates the right approach to manage risk-based assets. It cites two examples where Bahrain Petroleum Company (BAPCO) adopted the approach to 'achieve its stated environmental goal.'

In the wake of the BP Macondo Gulf of Mexico incident public awareness regarding oil pollution of our coastlines and the sea and other inland bodies of water has reached new heights. The adverse reaction faced by the industry after the Exxon Valdez breaking up into two pieces in the Prince William Sound on Alaskan coast was cacophonous enough, the BP Macondo reaction was simply deafening. “Not a drop of oil to the sea” has been adopted as one of the EHS mottos by many oil companies and is at par with other management initiatives that call for zero incidents and zero accidents . Bapco owns and operates a vast array of transport pipelines that bring crude oil to the refinery and then take our products to the loading wharves via storage and shipping terminals; and by necessity many of our lines run in shallow waters and above the sea. Any breach of integrity in our lines can thus defeat our vision of not-a-drop-of-oil-to-the-sea. Through two practical examples drawn from our Sea Line Number 5 and Number 19, the authors have illustrated in this paper the risk-based asset integrity management approach adopted by Bapco to achieve its stated environmental goal.

Our Reliability Engineering Department assures no containment loss is resulted from general corrosion which is supported and assisted by all. The top priority is to assure that no line thinning or pressure vessel thinning occurrences will go undetected by us as long as within our control (an example is submerged sea lines, unless NDT pigged). During recent Turnarounds and Inspections (T & I) we will make sure that all planned thickness gaging of critical systems are extensively scan gauged in line with their commitment to assure integrity.

Historical Perspective
Our region has experienced several major oil spills in the past and had to cope with all the negative consequences arising from those spill events. Not all such events have arisen from accidental causes. The vast spill resulting from damage to Kuwaiti oil wells at the back end of the first Gulf War could be viewed as deliberate acts rather than accidental events perse.

The overall impact to the region was quite significant. Figure 1 represents just one example of the major oil spill clean-up efforts that were required at that time. With an estimate of 8-11 million barrels of oil spilled it is reputed to be the largest oil spill that ever occurred. In terms of purely accidental events causing oil spill on the waters around the Gulf Cooperation Council countries the challenge is quite significant simply on the basis of the large volumes of crude and petroleum products being transported through the region. Closer to the shore lines and within the territorial waters of the Gulf countries it should be possible to exercise greater control on events and this is where the contribution from corrosion engineers and experts is more relevant.

Assuring Mechanical Integrity – Process Safety Management
Under an overarching system called “Operational Excellence Management System (OEMS)" Bapco have adopted a formal approach to process safety management in accordance with the United States OSHA regulation of 1992. "Mechanical Integrity" is a major element under this PSM system. Any loss of containment of hazardous materials or hydrocarbon is seen as recordable "Process Safety Event” which forms a component of the company's key performance indicators. The American Petroleum Institute has issued a standard API RP754 under which various hydrocarbon release quantities to the sea are categorized from Tier 1 through Tier 3. Potential consequences of a release in terms of total sea surface impacted can be determined using empirical relationships derived by experts from historical data of spills. For example, Figure 2 illustrates the spread of a 4,000 barrel release of Arab Light.

Transport and Shipping Lines
Bapco's main product storage facility at Sitra, lies about six kilometers North of the Refinery site and the Sitra Wharf is a further 5 km from the Sitra storage facility. Also, Bapco receives a bulk of its needed crude supply via a pipeline from Saudi Arabia which has a 26 kilometer marine section. The product lines transporting product and intermediates to Sitra Tank Farm run via a part of the Bahrain territorial waters (known as the 'Wet Gap') and our shipping lines from Sitra Tank Farm to the Sitra Wharf run along the causeway between these two sites. Any release from our transport lines at the Wet Gap area and any release from our shipping lines will thus enter the marine environment at once. Figure 3 shows our product transfer lines that run from the Refinery to the Sitra Tank Farm. In the wake of the BP's Gulf of Mexico incident the public has become extremely aware of the potential for adverse environmental impact that can get associated with an oil spill. Hence our 'tolerance' of release to sea is being driven lower and lower. After the BP incident Bapco management also promoted the concept of 'Not a Drop of Oil to the Sea' as an achievable objective. This has subsequently been spearheaded by our Environment Health and Safety Committee and this objective fits well with others such that: no one gets injured, zero incidents are an achievable goal, and no injuries no accidents. Hence from an engineering perspective the challenge is: how do we contribute to this management vision of 'not a drop of oil to the sea.' We examine this role through two practical examples; one relates to the use of life-cycle principles in assuring integrity of an ageing asset (Sea Line 5) and the other relates to operating practices and material selection (the Sea Line 19 incident).

Sea Line 5 - A Case Of Reliability-Driven Decision
No.5 Sea Line is a 12 Inch diameter, Schedule 20 Carbon Steel (API 5L Grade B) product shipping line with 6.5 km total length. No.5 Sea Line has a loading rate of 3,000 BPH. Approximately 80 per cent of the total length of the line has been located sub-sea since its installation. The sub-sea section of the line is not painted internally or externally and is facilitated with Cathodic Protection (CP) to prevent corrosion to the external surfaces. The 20 per cent of the line's length that runs above water is protected against external corrosion by application of a paint system.

For many years, sea lines have been subjected to scheduled hydro-tests to prove their fitness for continued service. Although the initially used hydro-test pressure was 275 psig, this was taken up to 425 psig in 1990 to expose any corrosion-weakened spots with potential to lead to an in-service rupture in the event of line over-pressurisation in operation due to, for instance, sudden closure of valves on ships taking cargo.

In July 2006, No.5 Sea Line developed a leak in the flume area south of the Sitra Wharf Causeway while it was being flushed with Naphtha at approximately 150 psig. This was immediately following the successful completion of its scheduled 5 yearly hydro-test at 425 psig. The leaking section was cut out, and replaced with a 20 feet long flanged spool. To ensure fitness of the line for continued service, decision was taken to hydro-test the entire line by pressurising it, one isolated section at a time. This test revealed 15 more leak points, which were all located along the older section of line that runs in the south flume from Sitra Tanks Pump House to the South Flume Riser. The line kept on failing repeatedly at approximately 100 psig as the identified leak holes were clamped, and the hydro-test was resumed.

No.5 Sea Line was holed mainly due to internal corrosion caused by presence of numerous corrosion cells (under-deposit corrosion and Oxygen attack cells ) over its inner surface along its length.

In terms of the number of leaks experienced in one single year, 2006 was the worst in the history of No.5 Sea Line as it witnessed a total of 17 leaks. It needs to be noted that of these 17 failures, 16 were in the older section of the line running in the south flume that spans from the Sitra Tanks Fire Pump House to the South Flume Riser. No.5 Sea Line had a total of 50 leaks in the past 32 years since 1975, and 16 of these leaks (32 per cent) occurred in a single year (2006) in the 3.3 km long section of the line in the south flume. See the charts.

The corrosion observed in the No.5 Sea Line indicates that these are as a result of stagnant aggressive water when line is idle and the corrosion is mainly confined to bottom; 5-7 o'clock position.

In the past pipeline stand up test was carried out and hydro test was limited to 275 psig. In 2010, this was changed to hydro testing to flange rating, except for the No.18 Sea Line due to logistic reasons. It is to be noted that when a line is pitted near holing, depending on the size and shape of the pit, it may stand the hydro test; as testings are carried out, the scale in the pitted areas get disturbed, causing these pits to pop-out during subsequent testing. In some cases corrosion may have already taken place in the form of pits or pits running into each other well before the initial testing or first leak.

Basis the age of No.5 Sea Line and the extent of corrosion damage it sustained, it would be impossible to predict where and when it might leak next. Consequently, No.5 Sea Line was taken out of service and it was recommended that the entire length of No.5 Sea Line from Sitra Tanks Fire Pump House to the Tee Head be replaced.

Sea Line 19 - Role Of Corrosion Engineers
This Sealine serves to route slop from the Wharf area back to the Slop Tank in Sitra Tank Farm. Corrosion of carbon steel in this service is known and had been observed to occur predominantly at the bottom portion inside the line. The decision to use ˝" thick carbon steel for a new line placed in service in 1996 was deliberate in that it was planned to rotate the line by 90 degrees every 5-6 years so that fresh steel gets exposed to the corrosive fluid, thus a line life of 20-24 years could be obtained. The first rotation was done in 2002. The next planned rotation of 2008 got deferred due to lack of resources at that time. During Aug 2010 there was a leak at the upstream elbow of a jump-over located near Costal Tanker Berth (No. 7).

The physical cause of the leak was a pitting corrosion hole (about 1/4" diameter); subsequent inspection of the leaked section showed several other corrosion pits. A decision was taken to immediately take the line out of service and carry out a hydrostatic test.

The initial decision to use carbon steel in this service and rotate the line periodically was based on cost versus risk-benefit analysis applicable at that time. In the present times, any leak to the sea is to be considered significant with consequences such as negative impact to company image, public complaints and actions.

While an initial study proposed replacement of the line, the Reliability Engineering Department (RED) recommended taking a decision basis review of the intelligent pigging results. Pigging data of No.19 Sea line showed almost 30,000 indications, but very few indications were reported above 60 percent in wall thickness losses, and these were mainly at causeway road crossing section and T-head riser. These sections had already been requested for replacement. Therefore based on previous service life history of 20 years, total line replacement was not recommend up to 2017 as originally envisaged. The pigging survey would be redone in 3 years' time and basis findings, decision could be taken on extensive line repairs/replacement.

Recommendations
  • Reinforce to all personnel the message from senior management that any oil leak to the sea is unacceptable. Personnel stationed close to marine facilities need to be vigilant and report any oil spill immediately.
  • Alert RED personnel that any violations of their Mechanical Integrity Guidelines document must be raised to the attention of senior management.
  • Correct the ISO 14001 Aspects register to include sealine leak events.
  • Issue an Engineering Design Guide requiring all sealines to have intelligent pigging facilities.
  • Install oil spill detection systems and permanently install oil spill containment systems at selected locations.
Concluding Remarks
At Bapco, the Reliability Engineering Department (RED) of Engineering Division plays a most vital role in ensuring the integrity of our static assets. RED is able to assure that our process and transport equipment pressure-envelop thickness gauging is carried out so comprehensively (and recorded in PCMS (piping corrosion monitoring system)) that there is virtually no chance of us having to face a major loss of containment event from a sudden rupture as a result of major sizable thinning due to general internal corrosion.

Acid gas lines, Overhead system transfer lines and vessels, LPG lines (including those going to the gas bottling plants), Lines associated with V509 in Gas Concentration Unit (GCU) (insurance survey action item), Lines and vessels associated with other light-end service in GCU, 2Poly light-end lines and vessels, Naphtha Rerun Complex (NRC) lines and vessels, Lines in services above auto-ignition temperature of fluid, Fuel gas liquid KO drums and associated piping, Gas Distribution Network(GDN) lines, Sea lines and Refinery-Sitra transfer lines were some of the services identified as most critical to Bapco’s operations and scan gauged to maximum possible extent.

To fulfil the responsibilities with specific regard to pipe line systems, RED extensively gauge our lines at every T & I (Turnaround and Inspection) regardless of PCMS 'recommended' next inspection date; Scan gauge a band of 4" at weld and intermediate locations and the extent of the gauging locations depends on system corrosion rate history; and ensure that additional attention is paid to gauging systems prone to unpredicted corrosion such as CDU/VDU overhead line.

Bibliography
  1. Relevant Bapco Incident Investigation Reports by Atil Gurhan and Ram K Goyal
  2. API RP 754; Process Safety Performance Indicators for the Refining and Petrochemical Industries
Acknowledgements
The authors are grateful to Mr. Mohamed Hasan, Senior Manager of Engineering Services Unit of Bahrain Petroleum Company (BAPCO), for granting permission to publish and present this paper.