API Spec 12F pdf download Specification for Shop Welded Tanks for Storage of Production Liquids
5.15 Shell Attachment
The tank deck shall be attached to the tank shell, if the deck if flanged, by a double-welded butt joint with completepenetration, or by a double-welded, ful-flet lap joint, or , if the deck is not flanged, by ful-fillet welds, both inside andoutside.
Tanks shall be furnished with a 24-in. x 36-in. extended-neck cleanout, located as shown in Figure 1 and conformingto Figure 4.Cleanout cover plates shall be of one-piece construction, except that, if so specified on the purchaseorder they shall be of two-piece construction with a horizontal lap seam having one row of 1/2-in. bolts on 2-in.centerswith suitable gaskets and bolt retainers. lf two-piece construction is specified, the top inspection plate shall have aclear opening of approximately 14 in.x 24 in., unless otherwise specified. When specified on the purchase order,handles for lifting the cleanout cover plate(s) shall be furnished.
Tanks may be provided with inlet and outlet connections as shown in Table 1, Column 9 and Column 10, andFigure 1.Unless otherwise specified by the purchaser, connections shall be full couplings, and shall be attached tothe tank member by ful-ille t welds on both inside and outside surfaces, with equal projections inside and outside thetank，except that half couplings may be used for connections c-1,C-4, C-5,and C-6, at the option of themanufacturer.Additional or fewer connections of other sizes or locations may be provided, if so agreed between thepurchaser and the manufacturer.When flanged or other types of connections are specfied, the nozzle neck shall bea minimum of standard weight pipe and attached by full-illet welds,both inside and outside. The bolting pattern forthe thief hatch shall conform to Figure 1.
5.18Anti-channel Drain Baffle Design
An anti-channel drain baffe conforming to the following requirements shall be furnished if so specified on thepurchase order.
a) The periphery of the baffle, in plan view, shall be 64 in.
b) The height of the baffle from the inside surface of the tank bottom to the top of the baffie shall be 4 in. minimum for90-bbl tanks, and 5 1/4 in. minimum for all other sizes.
c)The baffile shall be equipped with spacers so that the bottom edge of the baffle is 1 in. above the tank bottom.d) A drain line shall be provided from the baffle to the tank shell. The line size shall be 3 in. nominal for 90-bbl tanksand 4 in. nominal for all other sizes.
e) The baffie shall be attached to the tank bottom by a J-bolt passing through an eye retainer welded to the tankbottom, and by the line connection to the tank shell. The baffe shall not be welded to the tank bottom.
5.19 Downcomer Pipe
A downcomer pipe shall be installed if requested by the purchaser;design of downcomer to be by agreementbetween purchaser and manufacturer.
6 Venting Requirements 6.1 Normal Venting Connections C-1 and C-3 are provided for normal inbreathing and outbreathing due to temperature changes and to liquid movement into and out of the tank. These connections should be fitted with pressure-vacuum valves properly sized in accordance with API 2000. The pressure setting should be from 2 oz/in. 2 to 4 oz/in. 2 less than the opening pressure of devices used for emergency venting. Annex B is provided as a guide to aid in the selection of venting devices, where required.
6.2 Emergency Venting When storage tanks containing flammable liquids are exposed to fire, the venting rate may be in excess of that resulting from a combination of normal thermal effects and oil movement. Unless tanks are installed in remote locations, the purchaser shall provide, or cause to be provided, pressure relieving devices which will provide capacity in addition to normal venting to meet the requirements tabulated in Table C.1. The opening pressure of such devices shall not exceed the design pressure of the tank on which the devices are installed. The maximum internal pressure