Reliable storage of crude oil

Metal expansion joints for tank farm

KeyVisual_CaseStudy_MEJ_Tank_Farm .jpg

Tank settling by filling with crude oil. The increasing weight ensures that the double-walled tank sinks deeper into the ground. At the same time, the increase in volume causes the inner wall of the tank to bulge outwards.


Compensation of positional changes of the oil tanks under adverse conditions such as low temperatures, immediate proximity to the sea and explosive environment.


Customised metal expansion joints made of carbon steel with double bellows from EagleBurgmann

KeyVisual_CaseStudy_MEJ_Tank_Farm .jpg

A crude oil storage tank has a lifetime of approximately 15 to 20 years during which it is constantly filled to different levels or emptied. A completely filled tank can hold up to 630,000 barrels of crude oil. This enormous mass of crude oil causes the inner tank walls to bulge slightly and the entire tank unit to sink a little into the ground. The higher the filling level, the higher the bulging of the side walls and the more the tank settles into the ground. “This is normal, and therefore the pipe connections must be designed flexible enough to accommodate these movements” according to Jesper R. Dam,  Technical Manager at EagleBurgmann.

A leading provider for crude oil logistics operates a terminal storage plant at the coast of the Baltic Sea. In recent years, one of its tank farms was extended by two newly constructed storage tanks with a capacity of 100,000 m3 each.


In the process of filling up storage tanks with crude oil, the added weight results in the double-walled tanks sinking into the ground, while the increase in volume leads to a bulging of the inner tank wall. Depending on the amount of oil, the pressure in a tank is between 6 and 16 barg. These effects are common with large volume tanks and are known as tank settling. Due to the difference between the initial and the settled state,  a direct, rigid connection between pipeline and tank is not suitable. Expansion joints on the leakage and pressure lines are needed to compensate for the effects of tank movements resulting from different filling levels in terms of axial, lateral and angular movements, especially of the inner shell, and to ensure a sealed connection to prevent leakage.

In this case, components must also be able to withstand the location’s harsh climate conditions with the temperature dropping as low as -30 °C. Withstanding this temperature is a prerequisite for the material in this application. Common carbon steels are only suitable for temperatures of -20 °C or higher and are therefore inadequate for this application. Furthermore, due to the proximity to the sea, the materials must also be able to cope with high humidity and a high salt content in the air.


In this project, EagleBurgmann was awarded the manufacturing of 22 double bellows metal expansion joints to serve as connections between the pipelines as well as between the tanks and pipelines. Their sizes range from DN250 up to DN1200 depending on the pipeline and whether they are incorporated in the outer or inner wall.

The customized expansion joints are used on leakage as well as pressure lines. They consist of two multi-convolution and multi-layer bellows that are connected by a central pipe. This design allows for a large lateral offset to be absorbed. By tolerating the required motions, the expansion joints compensate changes in the tank’s position.


With regard to withstanding very low temperatures, P355NL1 carbon steel emerged as the ideal solution. The pressure vessel steel is characterized by high impact toughness even in very cold conditions. Additional  impact tests provided evidence that the  material meets the requirements at -30 °C.

The expansion joints were designed in accordance with the norm EN 14917 and the pressure equipment directive (PED) of the European Union. The expansion joints between the inner and the outer tank wall  comply with PED category III due to the increased explosion risk in this area.

EagleBurgmann is a proven, reliable supplier of this customer with a successful track record in previous projects for which they supplied expansion joints, mechanical seals as well as packings and gaskets.

While the overall construction of the storage tanks took 2 to 3 years, the fabrication of the metal expansion joints by EagleBurgmann was finished within a short time. This included product engineering and design, manufacturing as well as testing and documentation. As required by the norm, hydrostatic pressure tests, dye penetrant tests and visual tests were conducted. Additionally, hydrostatic pressure tests were carried out on-site after the expansion joints were installed.

The material used keeps its ability to contain the high internal pressure even at low outside temperatures. No maintenance is required, eliminating the need for shutdowns due to expansion joint inspections. The expansion joints are designed to be operational as long as the storage tanks are in service.


Operating conditions

• Media:  crude oil

• Temperature: -30 °C … 50 °C

• Movements: axial, lateral, angular

Solution: Metal expansion joints for tank farm

Further reference projects


Does not blow off steam

A boiler circulation pump in a power plant conveys very hot and pressurized water. The pump has no cooling jacket, which increases the risk of a thermosiphon effect.

Read on for the entire case study
Feuer und Flamme_DRO_Head2.jpg

Feuer und Flamme für hohe Temperaturen

In Drehrohröfen geht es heiß zu, sehr heiß sogar. Bei der Herstellung von Zement zum Beispiel misst das Thermometer mehr als 1.000 Grad Celsius. Dichtsysteme von EagleBurgmann, einem Unternehmen der Freudenberg Gruppe und EKK, leisten unter diesen „feurigen“ Hochtemperatur-Bedingungen nachhaltige Beiträge für Umweltschutz, Energieeffizienz und Prozesssicherheit.

Lesen Sie die ganze Case Study

Flexible and hygienic expansion joints for dairy products

By means  of custom-made PLUG & RUN expansion joints  with a more wear-resistant material, EagleBurgmann was able to provide a solution which ideally fulfills the requirements with regard to wear while at the same time significantly reducing the changeover time.

Read the complete case study

Maximum robustness for centrifugal compressors

Upgrading oil-lubricated seals to seals with dry gas seal technology on centrifugal compressors offers attractive benefits for the operator: considerable cost savings, emission reduction and longer MTBM (Mean Time Between Maintenance). However, the technical realization is challenging and tricky.

Read the complete case study

Powerful partnerships for clean air

EagleBurgmann supports shipbuilders, shipping companies and conversion companies globally with metal expansion joints for the flexible attachment of a scrubber within the exhaust gas system of a ship.

Read the complete case study
United Kingdom

Ready for dry running

Constantly changing operating conditions place extreme demands on pump seals in the production of antibiotic active ingredients. DiamondFace technology significantly extends the life of seals and enables the reduction of stock costs through rationalization.

Read on for the entire case study
Show all references

Excellence in Practice

With our free e-mail newsletter „Excellence in Practice“, you will receive first-hand information about current products, services, references and worthwhile industry insights.