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Ammonia tank refurbished for continuous safe operation

  • marimac 
Inspecting and refurbishing the 20-year-old ammonia storage tank for increased lifespan and continuous safe operation. Image credit: thyssenkrupp Uhde.
Inspecting and refurbishing the 20-year-old ammonia storage tank for increased lifespan and continuous safe operation. Image credit: thyssenkrupp Uhde.

The halfway mark has been reached in the inspection and refurbishment of thyssenkrupp Uhde’s ammonia tank located at Richards Bay’s back-of-port facilities in South Africa’s KwaZulu-Natal Province.

Two 19 034 cubic metre anhydrous ammonia storage tanks were designed and built by thyssenkrupp Uhde for the key customer back in 1982.

Liquid ammonia is stored in low pressure cryogenic tanks at harbour import facilities for distribution to various industries around the country. Ammonia is used in a host of applications that include the manufacturing of pesticides, fertilisers, plastics, textiles, dyes and other chemicals. Ammonia is also used as a refrigerant gas and to purify water supplies.

It is statutory to take storage tanks out of commission every 20 years to allow for internal and external inspection, due to the highly corrosive properties of liquid ammonia, and to protect people and the environment. Yurisha Singh, HOD Sales & Proposals, at thyssenkrupp Uhde, says: “By inspecting the integrity of the structure, we are able to identify possible weak areas and carry out all the necessary refurbishments. This helps to prevent potential ruptures and subsequent leakage, extend the tank service life and, importantly, also allows for continuous safe operation of the facility.”

The company was awarded the ammonia tank revamp project in October 2022. Singh says: “As the prime contractor, we deploy a full construction management team, including safety management, to site. We appoint sub-contractors to attend to the necessary construction work.”

Before any inspection can commence, the tank’s interior environment first has to be made safe. This involves draining all the ammonia liquid which is followed by the purging of any residual gases from the tank using an inert gas like nitrogen. Once the space is cleared of ammonia it is further vented with natural ambient air. Only then is it safe for a skilled thyssenkrupp Uhde technician to enter the tank without the need for a breathing apparatus to commence with the inspection procedures.

More than 1822 Non-Destructive Tests (NDTs) are performed to detect any potential faults. As the tank is manufactured from cold duty carbon steel, a Magnetic Test (MT), which is designed for only this type of material, is conducted. “For stainless steel tanks we would carry out Penetration Tests (PT),” notes Singh. Further tests conducted on the ammonia tank during the inspection process include a material thickness test as well as a Radiographic Test (RT). “We also conduct an ultrasonic test on all the weld points to determine whether the quality is within parameters. Any problem spots are then flagged for re-welding.” Once all the revamp work has been completed, the thyssenkrupp Uhde team conducts further NDTs to ensure that the tank is compliant with all necessary standards.

Although this is not a genuine ‘green’ project, Singh confirms that some of the identified revamp scope will help to reduce environmental impact. “For example, improved insulation will help to cut down on energy loss.”

Full refurbishment of the ammonia tank will be completed by thyssenkrupp Uhde. Commissioning will take place under the direction of experts who have been especially assigned to the project, in collaboration with operations staff from the customer. Project commissioning and expected completion date is scheduled for the month of June 2023.

Supplied by PR and edited by Eamonn Ryan