A Smarter and Cost Saving Approach for Inhibited Hydrotest Water for Large Storage Tanks Commissioning

摘要

This paper describes how demineralized water was substituted using inhibited sea water for hydro testing large capacity storage tanks and the huge cost savings achieved in the process. ADGAS built two new Paraffinic Naphtha Tanks in 2014-2016. The tanks are of double walled doubled deck floating roof construction. The holding capacity of the tanks was approx. 50000m3.The tanks were to be hydro tested before commissioning. The volume of the Hydrotest water used was 50000 m3 for inner tank and 10000 m3for the annular space between the walls hence totaling 60000 m3for one tank. Demineralized water was the primary choice for Hydrotesting. Minimum cost of desalinated water for testing one tank would be USD 222000 (USD 3.7x60000). Utilizing a conventional multifunction inhibitor would cost approximately USD 1.2 Million for both tanks. ADGAS used a newly developed floating corrosion inhibitor that would only wet the surfaces to be protected. Cost of this innovative chemical is only USD 11000/tank. The corrosion inhibitors used was a float coat mixed with oxygen scavenger. Float Coat inhibitor is a biodegradable, nitrite and amine free, and environmentally acceptable for use. This was spray/brush applied on the tank walls for surface protection. Sea water was deoxygenated using an oxygen scavenger and gradually filled in to the tank. The floating properties of the inhibitor ensured uniform reach of the inhibitor. Total cost savings achieved: Cost of demineralized water: 222000×2= USD 444000. (Both tanks) Cost of chemicals: 1. Float coat USD 11000/tank 2. Oxygen scavenger USD 49800/tank Total: USD 60800/tank Total cost of chemicals for two tanks: 60800× 2= USD 121600. Savings: 444000+ 1200000-121600 = USD 1321600