TANK

StandardsThe following International Codes may be applicable to the design of pressurized LPGtanks:1. The United States American Society of Mechanical Engineers, ASME Boilerand Pressure Vessel Code, Section VIII Section VIII is subdivided intoDivision 1 Unfired Pressure Vessels and Division 2 Rules for Constructionof Pressure Vessels. To be more economical, LPG horizontal tanks shall bedesigned and fabricated according to ASME VIII Division 1 while LPGsphere tanks shall be designed and fabricated according to ASME VIIIDivision 2.2. API STD 2510 and NFPA 58.3. BS 5500 Specification for Unfired Vessels.4. BS 1501 Steels for Fired and Unfired Pressure vessels - Plates, or Equivalent.5. BS 1502 Specifications for Steels for Fired and Unfired Pressure vessels -Sections and Bars.6. BS 1503 Specifications for Steel Forgings (including semi-finished forgedproducts) for Pressure Purposes.7. Finnish Standards (SFS) 3205, 3339, 3340, 3341, and 3342. FinnishGovernment Statues 98/73, 636/77, 257/84, 258/84, 312/79, and 1106/81.8. Japan High Pressure Gas Law (HPGL). Japan Industrial Standards (JIS).9. Australian Pressure Vessel Code AS 1210.

Materials Specifications(Page31)The recommended materials specifications for bullets and mounded drums are identicalto ASTM Specifications as follows:SA 516 Grade 70 normalized for the shell and headsSA 333 Grade 1 or 6 for nozzlesSA 350 Grade LF2 for flanges & fittingsSA 352 Grade LCB for fittingsSA 334 Grade 1 or 6 for tubingSubstitute Materials specifications may be made provided they meet with therequirements in GP 18-1-1. Materials not covered in GP 18-1-1 should be evaluated ona case by case basis.Design Temp: The minimum design temperature shall be the minimum metal temperature expected inservice, taking into consideration ambient temperature and auto-refrigeration of thestored product when it flashes to atmospheric pressure. For storing Propane, thistemperature will be 42 C. (Comment based on Propane)In no case shall the minimum design temperature be higherthan 18 oC. In many situations, the owner prefers to set the minimum designtemperature at the lowest possible temperature due to depressurizing the LPG toatmospheric pressure (42 C). This is almost always more conservative than thecriteria provided above.External Corrosion Protection1. Develop an earthwork specification for the mound. Specify sand bed fills, general fills, and acceptance tests, in accordance with ASTM Standards and Global Practice GP 4-9-1.

2. Provide an adequate corrosion resistant coating on the external surface of the drum per GP 19-1-1. Shop-applied coatings are preferred, but field applications are also acceptable. Irrespective of type and application method of coatings, a holiday test on the coating shall be carried out immediately prior to back-filling on site. The following specification is the normalrequirement:Surface Preparation: Abrasive Blast Clean toSSPC SP-10 Near White1st Field Coat: Coal Tar Epoxy @ 6-8 mils DFT2nd Field Coat: Coal Tar Epoxy @ 6-8 mils DFT

3. Install a cathodic protection system utilizing sacrificial anodes. Permanent reference electrodes shall be buried along with the drum at each end of the drum and above and beneath the drum at its midpoint.4. Requirements for a cathodic protection system are a twenty-year life and a maximum exposed steel surface of 10%. Insulating flanges shall separate permanent lines connected to plant piping from this cathodic protection(If Drum is mounded, it shall have cathodic protection by means of Sacrificial anodes, Corrosion resistant coating and proper Mound or fill material )system. The cathodic system may be used to protect short runs of buried pipeprovided the pipe coating is equal or better than the tank coating.5. Any special plant refinery/production applications where the LPG is expectedto contain wet H2S, shall have the drums lined internally.

Design Conditions for LPG DrumsDesign conditions for LPG drums should preferably be based on Propane storage.the minimum design pressure is specified as 17.2 bar gauge with a corresponding design temperature of 55 C. Under design conditions, 1.6 mm corrosion allowance shall be added to the design thickness of a drum

( Comment on Corrosion Allowance )

Nozzles on LPG Drums1. Pressure relief valve (PRV) connection to the vapor space.2. Water draw-off connection via the top (similar to GP 9-2-1, para. 9.5).3. Connection for the level indicator with high level alarm.4. Connection for the independent high level alarm.5. Connection for the fixed level gauge.6. Filling connection at the top of the drum.7. Withdrawal connection at the top or bottom of the drum.8. Vapor return connection at the top of the drum.9. Vent connection to atmosphere.10. Connection for the temperature indicator.11. Pressure indicator connection to the vapor space.

(One Nozzle for Level indicator with High alarm)(One Nozzle for Level indicator with Low alarm to trip the pump)(manhole shall be show for the drum)(P&ID shall indicate LPG sampling connections and provisions in the pump suction line)(Vent connection for the drum shall be shown)

LPG Compressor shall have a high pressure cut off switch in the discharge line LPG Compressor suction pressure shall be limired to a maximu value with a pressure switch. Other wise, Driver gets overlaoaded if the suction pressure increases beyond the design value.LPG Compressor hsall have a high temperature alarm on the discharge side.( it signals the pressure differential is too high)Compressor shall have a suction kock out drumHose Standards NFPA77