API RP 652-2014 pdf download.Linings of Aboveground Petroleum Storage Tank Bottoms.
1 Scope This recommended practice (RP) provides guidance on achieving effective corrosion control in aboveground storage tanks by application of tank bottom linings. It contains information pertinent to the selection of lining materials, surface preparation, lining application, cure, and inspection of tank bottom linings for existing and new storage tanks. In many cases, tank bottom linings have proven to be an effective method of preventing internal corrosion of steel tank bottoms. The intent of this RP is to provide information and guidance specific to aboveground steel storage tanks in hydrocarbon service. Certain practices recommended herein may also be applicable to tanks in other services. This RP is intended to serve only as a guide. Detailed tank bottom lining specifications are not included. This RP does not designate specific tank bottom linings for every situation because of the wide variety of service environments. NACE No.10/SSPC-PA 6 and NACE No. 11 /SSPC-PA 8 are industry consensus standards for installation of linings on tank floors and vessels. They are written in compulsory language and contain specific criteria intended for use by persons who provide written specifications for tank and vessel linings. These documents should be given consideration when designing and installing a lining system for steel bottom tanks. 2 Normative References 2.1 Codes, Standards, and Specifications The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. API Recommended Practice 575, Inspection of Atmospheric and Low-Pressure Storage Tanks API Standard 620, Design and Construction of Large, Welded, Low-Pressure Storage Tanks API Standard 650, Welded Tanks for Oil Storage
5.3 Tank Corrosion History The corrosion history of a particular tank should be considered when determining the need for an internal lining. The corrosion history of tanks in similar service should also be considered. The items to be considered are dictated by individual circumstances, but some of the more important considerations are as follows. a) Where is the corrosion occurring (product side, soil side, or both)? b) What is the internal and soil-side corrosion rate? c) Have there been significant changes in the corrosion rate? d) Is the corrosion uniform or localized? e) Has corrosion caused perforation of the steel tank bottom? f) What was the prior service of the tank and how corrosive was that product? 5.4 Tank Foundation The foundation must be adequate to prevent excessive settlement of the tank. If uniform foundation support is not provided, flexing of the tank bottom can result as the tank is filled or emptied. Flexing occurs on all steel floors; however, excessive flexing of the steel bottom may cause an internal bottom lining to crack. The tank pad material beneath the steel bottom has a significant effect on the potential for underside corrosion. If there is pad contamination (e.g. rock, lumps of clay, welding electrodes, paper, plastic, wood, etc.) in contact with the underside of the steel, differential aeration or other corrosion cells can form where the contaminates are in contact with the tank bottom and severe corrosion may result (see API 651 ). The use of wood under a tank floor is not recommended given that it promotes bacterial activity and will cause accelerated corrosion. 6 Tank Bottom Lining Selection 6.1 General Tank bottom linings can generally be divided into two classes: thin-films [with a dry film thickness less than 20 mils (500 µm)] and thick-films [with a dry film thickness of 20 mils (500 µm) or more]. Linings may be applied to the bottoms of storage tanks when they are first constructed or they may be installed after some period of service.