In December 2020, Totus' Industrial Services team completed a successful project for a key client.
The highlights of the project were:
- 12,500 m³ Crude Oil Transferred in 72 Hours
- Zero accidents
- 100% containment while operating over the jetty
- 600m pipework laid in 48 hours
- Ship released 48 hours ahead of schedule saving client ££££s
A Crude Oil storage tank containing sludge up to 4m, water and a significant volume of crude oil was fast approaching the end of its statutory inspection requirements. With close attention from the HSE, this was a high profile and very important job.
Firstly, we needed to establish an accurate assessment of the material inside the tank. Following a sludge profile of the tank, we completed an oil water interface measurement. The results showing the tank had over 12,000m³ of crude oil on top of a layer of water, covering 4 meters of sludge.
Analysis showed it to be good quality crude oil with a flash point of -20°C and a buyer was secured, however the Crude oil needed to be pumped onto a ship 600m from the tank using temporary pipework as the site transfer lines were unavailable.
As Principal Designer and Principal Contractor for the project, our solution had safety at the heart of the design. Due to restrictions on time, and without the option of using a sister tank for storage of material, the priority was to remove the crude oil leaving the sludge and water to be treated at a later date.
Our solution was to hot tap into the tank at the interface of oil and water. Using ATEX pumps in series, we designed the optimum route for our 6” temporary pipework from the tank to the ship, including all scaffold requirements to navigate the 600m route.
Our design included provisions for hydro testing the system, joint integrity testing, electrical continuity verification, non-return valve protection, water flush of the lines following the crude transfer and a valve design that allowed controlled and safe clearing of the lines using our in-house specialist vacuum equipment.
Hot tapping into the live Crude Oil tank was critical to maximise the volume of crude removed while ensuring the volume of water was minimised. After detailed measurements and assessment of the plate integrity, the cut was made at exactly the right location.
To ensure a safe and efficient operation during Crude oil transfer Process Safety was critical. We designed detailed valve-by-valve procedures with double sign off protection for each stage of the operation. To support this, our team walked the entire line from ship to tank every hour checking the valve integrity.
An additional challenge was caused by the concern of the very high level of sludge in the tank. During the transfer, the roof legs would reach the sludge layer and lower into it by 1.5m. To monitor and control this, we installed four roof measuring devices evenly around the tank. We recorded hourly increases to ensure that the roof was lowering at a steady rate and therefore was level.
Following a successful hydro test, we commenced the crude transfer. During the crude oil transfer our team recorded the flow and total cargo discharged to the ship every hour with rates of up to 210m³ per hour being produced.
In 72 hours, we removed the full cargo of 12,507.953m³ of Crude Oil and then displaced the lines with fresh water leaving them clear.
Working through the Process Instructions, we methodically cleared the lines using the Totus Liquid Ring Tanker allowing us to safely demobilise the job and leave the site clean and tidy with a very satisfied client.