Crude Storage Tanks play a vital role in the day to day activities of Export Operations. The integrity of the tanks leading to the operational availability of the tanks is key to the continuous, undisrupted productions in GCs as well as to meet the Export commitment of KOC and the State of Kuwait at large.
Crude Oil storage tanks have all the features essential for measurement, monitor, operation, control, containment, quality, safety protections, stability, etc.,
Export Operations have 86 numbers of Floating Roof Crude Oil Storage Tanks of various sizes ranging from 44 meter to 91 meter diameter and capacities in the range of 150,000 Barrels to 618,000 Barrels, which are used to handle multiple crude oil streams viz., Kuwait Export Crude (KEC), Kuwait Super Light Crude (KSLC), Kuwait South Ratqa Crude (KSRC) and EOCENE. Projects are in place to segregate two more crude export Ratawi Burgan (R/B), Kuwait Medium Heavy (KMH) and Kuwait Light Crude.
Segregation of tanks is done based on the production and export capacity requirements, pipeline network flexibility, operational and loading methodology etc.,
The tanks are taken out of service for major overhauling every 10 years of service. However, based on the protection measures available (fiberglass lining of tank bottom, cathodic protection, etc.,), the maintenance cycle are being considered for 15 years service.
All the tanks that are constructed before 2006 were of single deck floating roof design. Since 2006, the sizes of new tanks are generally preferred at 91 meter diameter, with double deck floating roof which is more suitable and advantageous for larger diameter tanks. Larger capacity tanks have the advantage of minimum tank changeovers during loading operations.
Tank 58 is one of the biggest single deck floating roof tanks (80 meter diameter) constructed in 1985. Due to the roof damage, the Tank was taken out of commission and handed over to Maintenance for major overhauling in 2014.
Access to more than 50% of the tank internal area was not possible due to the collapsed roof and the risks thereon. Conventional sludge removing mechanisms were not workable for safety reasons. After evaluating all the options, the roof was dismantled by a combination of cold cutting (high pressure water jetting) and conventional hot work by making room for cutting operations by stage-wise segregated sludge removal.
Then came the challenge of selection of type of roof. Though there is no theoretical limitations in selecting the single deck roof based on size, the stability of single deck roof over the period of operation wears away with undulations in the roof and water accumulations. There was an incident of oil entry into the single deck roof of one of the similar size tank in 2010.
In the absence of prior experience in construction of a double deck roof through maintenance contractor (wherein the design has to be endorsed in-house), the selection was critical.
Export Operations geared upto the task and recommended to install double deck roof.
Replacement with New Double Deck Floating roof inclusive of Design, Roof load calculations, General arrangement, Roof deck plate (bottom and top) layout, foam dam arrangement, arrangement of roof legs / drain sumps / auto bleeders / guide poles / rolling ladder / place thickness selection, etc., were submitted by contractor.
Design reviews / endorsement were handled in-house involving relevant stakeholders (EMS&R, Insp&Corr, EO, ETS, HSE-EO&MO). Review meetings / presentations conducted as and when required and construction of roof was successfully completed by EMS&R with support from all relevant teams.
Additional features were added in roof and tank as well during the process of overhauling, based on the lessons learnt and the consistencies with other similar design:
- Two Primary Roof Drains with “pivot master flexible joints"
- Additional Emergency Roof Drains (with seal pots) at suitable locations and distance from the primary roof drains.
- Added Height of pontoon manway necks at lower elevations
- Access ladder for High Level Switch
Hydrotest of the tank was completed and the Tank will be commissioned in Aug-2021.
The following are the highlights of the activities carried out by Export Operations and Support Services Group in Tank 58:
- Double Deck floating roof constructed in-house.
- Implementation of High pressure hydrojetting technology for the first time to cold-cut the roof plates.
- Use of High pressure hydrojet technology for fiberglass lining removal.
The success of this activity inspire the teams to go for similar complex jobs in order to prove the competencies of all individuals.
KOC NORTH & SOUTH TANK FARMS
TANK 58 (AFTER MODIFICATION)
