Table 12-4 Maximum Allowable Joint Efficiencies for Arc and Gas Welded Joints No. 1 2 3 4 Type of Joint Description Butt joints as attained by double- welding or by other means that will obtain the same quality of deposited weld metal on the in- side and outside weld surfaces to agree with the requirements of UW-35. Welds using metal back- ing strips that remain in the place are excluded. Single- welded butt joint with backing strip other than those included under (1). Single- welded butt joint without use of backing strip Double full fillet lap joint. limitations None (a) None except as in (b) below (b) Butt weld with one plate offset — for circumferential joints only, see UW-13(c) andFig.UW-13.1(k) Circumferential joints only, not over 54-inch thick and not over 24-in. outside diameter. Longitudinal joints not over /i-in. thick. Circumferential joints not over %4n, thick. (a) Fully (b) Spot (c) Not Spot Radiographed' Examined Examined 3 1.00 0.85 0.70 0.90 0.80 0.65 — 0.60 — — 0.55 on page) 5 Single full fillet lap joints with plug welds conforming to UW-17. (a) Circumferential joints 4 for — — 0,50 attachment of heads not over 24-in. outside diameter to shells not over H in. thick. (b) Circumferential joints for the attachment to shells of jackets not over % in. in nominal thickness where the distance from the center of the plug weld to the edge of the plate is not less than 1 1 A times the diamter of the hole for the plug. 6 Single full fillet lap joints with- (a) For the attachment of heads — — 0.45 out plug welds. convex to pressure to shells not over %-in. required thickness, only with use of fillet weld on inside of shell; or (b) For attachment of heads having pressure on either side to shells not over 24-in. inside diameter and not over 54-in. required thickness with fillet weld on out- side of head flange only. 'See UW-12(a) and UW-5J. 2 See UW-12(b) and UW-52. -The maximum allowable joint efficiencies shown in this column are the weld joint efficiencies multiplied by 0,80 (and rounded off to the nearest 0.05) to effect the basic reduction in allowable stress required by the Division for welded vessels that are not spot examined. See (UW-12(c)). 4 Joints attaching hemispherical heads to shells are excluded, Table 12-5 Materials Typically Specified Plate Pipe Flanges and Fittings Stud Bolts Nuts Low Pressure SA-36 SA-285-C SA-53-B SA-105 SA-193-B7 SA-194-2H Common Steel T > -20°F SA-5 16-70 SA-106-B SA-105 SA-181-1 SA-193-B7 SA-194-2H NACE MR-01-75 SA-5 16-70 SA-106-B SA-105 SA-181-1 SA-193-B7M SA-194-2M Low Temp -50°F<T<-20°F SA-5 16-70 SA-333-6 SA-350-LF1 SA-320-L7 S A- 194-4 Low Temp T < -50°F SA-240-304 SA-312 TP-304 SA-182 F-304 SA-193-B8 SA-194-8A High CO 2 Service SA-240-316L SA-312 TP-316L SA-182 F-316L SA-193-B8M SA-194-8MA Mechanical Design of Pressure Vessels 339 Figure 12-3. Vessel support devices. (text continued from page 335) The shell weight can be estimated from: where W = weight, Ib d = ID, in. t = wall thickness, in. L = shell length, ft The weight of one 2:1 ellipsoidal head is approximately: The weight of a cone is: a = one half the cone apex angle 340 Design of GAS-HANDLING Systems and Facilities The weight of nozzles and internals can be estimated at 5 to 10% of the sum of the shell and head weights. The weight of a skirt can be estimated as the same weight per foot as the shell with a length given by Equation 12-8 for an ellipsoidal head and Equation 12-9 for a conical head. where L = skirt length, ft The weight of pedestals for a horizontal vessel can be estimated as 10% of the total weight of the vessel. SPECIFICATION AND DESIGN OF PRESSURE VESSELS Pressure Vessel Specifications Most companies have a detailed general specification for the construc- tion of pressure vessels, which defines the overall quality of fabrication required and addresses specific items such as: »Code compliance • Design conditions and materials • Design details - Vessel design and tolerances - Vessel connections (nozzle schedules) - Vessel internals - Ladders, cages, platforms, and stairs - Vessel supports and lifting lugs - Insulation supports - Shop drawings • Fabrication - General - Welding - Painting - Inspection and testing - Identification stamping Mechanical Design of Pressure Vessels 341 - Drawings, final reports, and data sheets - Preparation for shipment A copy of this specification is normally attached to a bid request form, which includes a pressure vessel specification sheet such as the one shown in Figure 12-4. This sheet contains schematic vessel drawings and pertinent specifications and thus defines the vessel in enough detail so the manufacturer can quote a price and so the operator can be sure that all quotes represent comparable quality. The vessel connections (nozzle schedules) are developed from mechanical flow diagrams. It is not neces- sary for the bidder to know the location of the nozzles to submit a quote or even to order material. Shop Drawings Before the vessel fabrication can proceed, the fabricator will develop complete drawings and have these drawings approved by the representa- tive of the engineering firm and/or the operating company. These draw- ings are called shop drawings. They will show detailed vessel design and fabrication/welding, nozzle schedules and locations, details of vessel internals, and other accessories. Examples are shown in Figures 12-5 through 12-13. Some typical details are discussed below. Nozzles Nozzles should be sized according to pipe sizing criteria, such as those provided in API RP 14E. The outlet nozzle is generally the same size as the inlet nozzle. To prevent baffle destruction due to impingement, the entering fluid velocity is to be limited as: where V ]N = maximum inlet nozzle fluid velocity, ft/sec pi = density of the entering fluid, lb/ft 3 If an interior centrifugal (cyclone) separator is used, the inlet nozzle size should be the same size as the pipe. If the internal design requires (text continued on page 346) Figure 12-4, Example of pressure vessel specification sheet. Figure 12-5, Example of pressure vessel shop drawing. 344 Design of GAS-HANDLING Systems and Facilities Figure 12-6. Nozzle projections. (Reprinted with permission from Pressure Vesset Handbook, Publishing, Inc., Tulsa.) Figure 12-7. Siphon drain. Mechanical Design of Pressure Vessels 345 Figure 12*8. Example of supports for mist extractors. (Reprinted with permission from Pressure Vessel Handbook, Publishing, Inc., Tulsa.) Figure 12-9. Examples of Vortex Breaker Details. (Source: Copyright © International Training & Development.) [...]... temperature = 20 0°F = M in Corrosion allowance Material = SA516 Grade 70 Diameter = 1.0ft Seam-to-seam length above the cone = 12 ft Cone apex angle = 60° Solution: Case I—Cone bottom Required thickness = 0 .50 7 + 0 . 25 0 = 0. 757 in 3 52 Design of GAS-HANDLING Systems and Facilities (b)Head: |- == ( 1 25 ) ( 120 ) , _ ,— = y 50 5 in (2) (17 ,50 0) (0. 85) - (0 .2) ( 1 25 ) Required thickness = 0 .50 5 + 0 . 25 0 = 0. 755 in Use—-in... head (0.8 1 25 ) W = (0.34)(0.8 1 25 )( 120 )2 + (1.9)(0.8 1 25 )( 120 ) = 4,1631b (c) Cone: _ Pd ~ 2 cos a (SE - 0.6P) t t= ( 1 25 ) ( 120 ) • = 0 .58 5 in (2 cos 30) (17 ,50 0 x 0. 85 - 0.6 x 1 25 ) Required thickness = 0 .58 5 + 0 . 25 0 = 0.8 35 in Use in plate (0.8 75) w= (0 .23 ) (0.875X 120 )1= sin 30 (d) Skirt: Height = —— = 8.66 ft tan 30 Allow 2 ft for access Height =11 ft Assume it is M-in plate W = (11X 120 X0.5X11) = 7 ,26 0 (e)... Length of shell = 12 + 8.7 = 20 .7 ft Weight of shell = (11)( 120 )(0.8 1 25 ) (20 .7) = 22 ,20 0 Ib 353 354 Design of GAS-HANDLING Systems and Facilities (c) Summary: Shell Head Head Skirt Cone Misc 22 ,20 0 4,163 4,163 2, 970 L 656 35, 1 52 _5JQQ 40,1 52 Ib CHAPTER 13 Pressure Relief* The most important safety devices in a production facility are the pressure relief valves, which ensure that pipes, valves, fittings, and. .. Misc 12, 870 4,163 5, 796 7 ,26 0 30,089 5. 000 35, 089 Ib Mechanical Design of Pressure Vessels Case II—Ellipsoidal head (a) Skirt: I-°^d +r2jL j_j — " 12 _ (0 . 25 ) ( 120 ) | 12 = 4 .50 ft W = (11) ( 120 ) (0 .5) (4 .5) = 2, 970 Ib (b)^ELn!aiy: Shdl Head Head Skirt Misc 12 870 < 4,163 4,163 2, 970 24 ,166 5, 000 29 ,1661b Case III—Internal cone (a) Internal Cone: w= (0 .23 ) (0 . 25 ) ( 120 )2 sin 30 lb (b) Shell: Height of cone... detail 348 Design of GAS-HANDLING Systems and Facilities BASE PLATE SCHEDULE ANGLE LEG SIZE "A" *&" x x x x a* 3 3/8" 2 7/8* 6* 5" 4" 3" 6* 5" 4" 3" 2 1 /2" x 2 1 /2" 7* 6" 2* 5* 13/4" 4* 1 1 /2" ELEVATION VIEW Figure 12- 11 Angle support legs Pressure Relief Devices All pressure vessels should be equipped with one or more pressure safety valves (PSVs) to prevent overpressure This is a requirement of both... the PSV The disc is designed to break when the internal pressure exceeds the set point Unlike the PSV, which is self-closing, the rupture disc must be replaced if it has been activated Corrosion Protection Pressure vessels handling salt water and fluids containing signficiant amounts of H2S and CO2 require corrosion protection Common corro- 350 Design of GAS-HANDLING Systems and Facilities SIDE STEP... Thro of Paragon Engineering Services, Inc 355 356 Design of GAS-HANDLING Systems and Facilities RELIEF REQUIREMENTS The ASME code requires every pressure vessel that can be blocked In to have a relief valve to alleviate pressure build up due to thermal expansion of trapped gases or liquids In addition, the American Petroleum Institute Recommended Practice (API RP) 14C, "Analysis, Design, Installation and. .. for 12- in and larger manways for safe and easy opening and closing of the cover Figure 12- 10 shows an example of a horizontal manway cover davit and sleeve details Vessel Supports Small vertical vessels may be supported by angle support legs, as shown in Figure 12- 11 Larger vertical vessels are generally supported by a skirt support, as shown in Figure 12- 12 At least two (2) vent holes, 180° apart,... Design of Pressure Vessels 351 EXAMPLE PROBLEM 12- 1 Determine the weight for the following free-water knockout It is butt weld fabricated with spot x-ray and to be built to Division 1 A conical head (bottom of the vessel) is desired for ease in sand removal Compare this weight to that of a vessel without the conical section and that to a vessel with a !4-in plate internal cone Design pressure = 1 25 ... Testing of Basic Surface Safety Systems on Offshore Production Platforms," recommends that relief valves be installed at various locations in the production system; and API RP 52 0 , "Design and Installation of Pressure Relieving Systems in Refineries," recommends various conditions for sizing relief valves In production facility design, the most common relieving conditions are (I) blocked discharge, (2) . ( 12 0) |- == , _ ,— = y 50 5 in ( 2) (17 ,50 0) (0.8 5) - (0. 2) ( 12 5) Required thickness = 0 .50 5 + 0 . 25 0 = 0. 755 in. Use—-in. head (0.8 12 5) W = (0.3 4)( 0.8 12 5) ( 12 0) 2 + (1. 9)( 0.8 12 5) ( 12 0) = . (1. 9)( 0.8 12 5) ( 12 0) = 4,1631b (c) Cone: _ Pd ~ 2 cos a (SE - 0.6P) t ( 12 5) ( 12 0) t = • = 0 .58 5 in. (2 cos 3 0) (17 ,50 0 x 0. 85 - 0.6 x 12 5) Required thickness = 0 .58 5 + 0 . 25 0 . 12 + 8.7 = 20 .7 ft Weight of shell = (1 1)( 12 0)( 0.8 12 5) ( 20 . 7) = 22 ,20 0 Ib 354 Design of GAS-HANDLING Systems and Facilities (c) Summary: Shell 22 ,20 0 Head 4,163 Head 4,163 Skirt