Welded Pump Drain Pipe Cracked

Safety Incident : A crack in the weld of a pump drain pipe
Location Of Incident : Lingen, Germany
Date Of Incident : 10th May 2005


Brief Account Of Safety Incident
On May 10, 2005, a contracted company performed assembly work on the RF1- Feedpump GA-1804 B, and damaged a drain pipe of the pump housing. A strong gas leakage occurred close to the feed furnace BA-1801/02.

Result:
O Formation of a gas cloud of light gasoline, downstream of the reformer furnace. The cloud was stemmed by changing over to an available parallel pump, while applying adequate PSA and the involvement of the fire brigade (department).
Possible result:
O Danger of people and operating units in the event that the gas cloud would have ignited close to the reformer furnace.

What went well:
O The contractor informed control room operators immediately.
O Quick identification of the problem on site
O Quick and safe change of the leaking pump by the operators and the use of heavy breathing mask and the support of the fire department.
O Fortunately the wind direction was turned away from the furnace.

What went wrong:
As a general rule, it is prohibited to step onto pipes regardless if assembly work is done or during operations. Unfortunately this cannot always be avoided due to the location of shutdown valves or other pipe accessoires. A weld failed at a location which was not fulfilling the required quality levels.

Direct causes:
Leakage due to stepping on the drain pipe.
An insufficient weld at the pump drainage.

Causes in the system:
Reconsidering of Integrity management for inspection and documentation of nozzles.

Direct measurements:
O Immediate repair of the defect weld.
O Inspection of neighboring welds, also at the parallel feedpump GA-1804A via x-rays (without findings).
O Clarifying discussion with the contractor, who can demonstrate long lasting experience in the Lingen refinery.

Additional measurements:
O Updating of the nozzle-inspection-program incl. documentation and determination of periodic inspections.
O Installing of additional fittings on the suction and pressure side of the feed pumps (HAZOP-safety discussion is still necessary!!)
O Automatic extinguish-vapor-supply to the reformer furnace is planned (TAR 2006).

Lessons Learned
O Leakages even on small pipes could have serious consequences for people and equipment.
O nozzle inspection programs must be completed and well documented.
O For limitation of damages process units have to be devided up into smaller, containable sections.

Conclusion:
It has been seldom that Pump drain pipes failed, however, when they failed, it was due to corrosion. As a result of a mechanical rupture of a pump nuzzle at reformer-1, a nozzle testing program was developed. All pumps that operate with hazardous goods were listed, classified based on its potential risk, and the nozzle welds radio-graphically examined. The result was rather shocking.
Not only did we identify unacceptable weld imperfections and design deficiencies on fillet and flange welds on pumps which are 50 and more years old, also pumps that are of a more recent date of manufacture came out with the same results. Depending on the testing result, repairs were initiated right away or scheduled for the upcoming TAR in 2006.
Per definition, Pumps are machines that fall within the scope of the European Directive for Machinery (98/37/EC). It seems that in accordance with the machinery directive, non-destructive testing requirements are not as stringent as they are in accordance with the pressure equipment directive (97/23/EC) and the associated engineering and construction codes (e.g. . AD-Merkblatt 2000, EN 13445, EN 13480, ASME Section VIII Div.-1). What is required though is a pressure test as part of integrity/safety testing requirements.
From now on, we will require a non-destructive examination of nozzles and welded assembly parts, which carry external loads. The evaluation will be performed in accordance with EN 25817, Quality Level C (Moderate) or B (Stringent), or equivalent quality standards and levels.