Argonne Engineering Professionals Seminar Series September 30, 2009 Argonne National Laboratory Argonne, IL

Transcription

1 Argonne Engineering Professionals Seminar Series September 30, 2009 Argonne National Laboratory Argonne, IL Presentation of Case Study Manufacture of a Helium/Hydrogen Heat Exchanger to the ASME Code presented by: Mike Seely, PHD. Meyer Tool & Mfg., Inc. Oak Lawn, IL

2 Meyer Tool & Manufacturing, Inc. Oak Lawn, IL USA Specialists in Cryogenic, Vacuum and Pressure Technologies

3 Specialists in Getting it Right Our components are installed in the world s most powerful laser, most powerful particle accelerator, most powerful neutron source, at the South Pole and in other harsh and demanding environments. All these components are installed with no surprises and working without fault. Our experience and knowledge is what has made this happen in the past and can make it happen for your project. With over 240 vessels built and delivered in the last three years, with a value exceeding 3 million dollars, Meyer Tool has the engineering and manufacturing resources to give you a surprise free experience.

4 Quick Facts Founded: In Location: Oak Lawn, IL USA Employees: 35 Business Type: Contract Manufacturer Products: Custom Components and Assemblies for Science and Industry. Customers: USA Department of Energy National Laboratories; Industrial Gas Liquefaction System Providers; Vacuum System Original Equipment manufacturers in thin film coating, ddsolar, crystal growth, etc., Medical Equipment, and more..

5 A sampling of what we do. GMR Coating Vessel Laser System Chamber MOCVD Vessel Aluminum Hog outs Anodized Aluminum Vessels Welded Aluminum Vessels

6 A sampling of what we do. Water Jacketed CG Vessel UHV Chambers Expert Welding Precision Machining Inspection & Test Dedicated Cleaning Area

7 Case Study Manufacture of a Helium/Hydrogen Heat Exchanger to the ASME Code

8 We started with this.

9 And ended up with this.

10 What is the ASME Boiler and Pressure Vessel Code? According to the American Society of Mechanical Engineers (ASME) Statement of Policy: The ASME Boiler and Pressure Vessel Code provides rules for the construction of boilers, pressure vessels, and nuclear components. This includes requirements for material design, fabrication, examination, inspection and stamping.

11 The ASME Boiler and Pressure Vessel Code consists of twelve Sections. Section VIII contains the Rules for Construction of Pressure Vessels. Section VIII is further divided into three Divisions. Division 1 treats Vessels designed by rules and does not require a detailed evaluation of all stresses. Division 2 provides alternative rules for Vessel design and requires a much more detailed evaluation of stresses. Division 3 concerns alternate rules for construction of High Pressure Vessels (maximum allowable working pressure above 10,000 psig). The majority of pressure vessels are designed and built to the requirements of Division 1.

12 Section VIII Division 1 is a rules based not a design based Code, this means where a mandatory requirement or prohibition exists within the Code, it must be followed by the designer or fabricator (i.e. Rules based). However where such guidance does not exist, engineering judgment consistent with the Division s design philosophy may be used. This is worth stressing: a perfectly valid analysis may lead to a different result than a Division design formula or fabrication detail, however the Code requirement must be followed.

13 In this case study we are going to look at the design of a cryogenic shell and tube heat exchanger. The original design was a first iteration by a person new to the Code. We will explore how the design changed when Meyer Tool became responsible for the design and manufacture.

14 What were we building? Shell and Tube Counter Flow Heat Exchanger This heat exchanger enables testing and operation of a cryogenic target at 20K and is an integral part of the QWeak Physics Experiment to be conducted at Jefferson Laboratory s Hall C. Meyer Tool built the heat exchanger in a period of about 6 weeks in May and June of 2009.

15 LiquidHydrogenTargetHe15KSupplyHeReturnFinTubeHeatExchangerPumpAluminumCelelectronbeamentrancewindowexitwindow

16 Requirements Shell and Tube Counter Flow Heat Exchanger Designed, manufactured and Stamped to the ASME Section VIII U Stamped Pressure Vessel Design Pressure: 300PSIG/ Full external vacuum Design Temperature: Max: 100F / MDMT: -459F Material of Construction: Stainless Steel Physical Envelope: OD Shell; 34.3 OAL; Multi-pass Internal copper tube coil. Tube Side Fluid: Helium 15K / 15 atm Shell Side Fluid: Hydrogen 20 K

17 Physical Components Code Part? Coil Mandrel Assembly (Coil Supports) No Copper coil and stainless steel inlet Originally yes, after and outlet tubes. redesign no. Shell Yes End Closures Yes Support Brackets Yes

18 The original construction prints showed three copper coils mounted on a cylindrical mandrel. The mandrel and some other miscellaneous components supported the coils within the shell of the exchanger. In both the original and modified design these structural components were not welded to the ASME Code Vessel nor did they impose an significant loads on the vessel. The coils were interconnected in a cross flow arrangement, necessitating three inlets and three outlets for the helium through the shell of the pressure vessel. These inlets and outlets were stainless steel tubes brazed to the coils. In the original design the tubes were welded directly to the shell.

19 Interior Copper fin tube coil.

20 Interior Copper fin tube coil installed in stainless steel shell.

21 The original pressure vessel itself consisted of a shell fabricated from a 10 SCH5S Pipe, two elliptical end closures shown as machined from round bar, one each shell inlet and outlet consisting of a 3 OD x.065 w tubes welded to the end closures and a 4.63 OD Conflat Flange, the six stainless steel Tube 0.5 OD x.035 w coil inlets and outlets each with two external support brackets.

22 Original design drawing.

23 The first step was to review the original design and determine if it met the Code Rules for design and construction. Besides the drawing package the customer had provided a set of Code Calculations.

24 From the basic design rules found in Part UG of Section VIII (UG-27 Thickness of Shells Under Internal Pressure, UG-28 Thickness of Shells and Tubes Under External Pressure, UG- 32 Formed Heads, and Sections, Pressure on Concave Side) the design appeared to be in compliance. However a deeper review identified a number of issues that only a close and detailed reading of Section VIII (or experience) would identify.

25 ASME Section VIII paragraph UW-2 (b)(4) requires all Category D welds (nozzle to shell or head welds) to be full penetration when the Minimum Design Metal Temperature is below -320F. Therefore the welds shown in the original design on drawings between the End Closure and 3 OD tube and drawing between the six inlet/outlet tubes and the shell were not in compliance.

26 ASME Section VIII paragraph UW-2 (b) (3) requires all Category C welds (nozzle to flange welds) to be full penetration when Charpy Impact Testing is required per Section UHA. The welds shown on drawing between the 3 OD Tube and Conflat Flange are not in compliance.

27 Section VIII paragraph UG-45 imposes rules for the minimum wall thickness of nozzle necks. These rules supercede the design rules of UG-27 and UG-28 when sizing cylindrical nozzle necks. The wording of UG-45 can be confusing the first time you read it. The application of these rules can vary for the particular case. In this design it identified that neither the 3 OD tube nor the 0.5 OD tube nozzles had sufficient wall thickness to meet the paragraph requirement.

28 The Code Section UG-45 Nozzle Neck Thickness The minimum thickness of nozzle necks shall be the larger of (a) or (b) below. Shear stresses UG-45(a) The minimum wall thickness of a nozzle neck or other connection shall not be less than the thickness computed from the applicable loadings in UG-22 plus the thickness added for allowances for corrosion and threading, as applicable, on the connection. UG-45(b) Additionally, the minimum thickness of a nozzle neck shall not be less than the smaller of the nozzle wall thickness as determined in (b)(1), (b)(2) or b(3) below, and the wall thickness determined by (b)(4) below: UG-45(b)(1) for vessels under internal pressure only, the thickness (plus corrosion allowance) required for pressure (assuming E=1.0) for the shell or head at the location where the location where the nozzle neck or other connection attaches to the vessel but in no case less than the minimum thickness specified in UG-16(b); UG-45(b)(2); for vessels under external pressure only, the thickness (plus corrosion allowance) obtained by using the external design pressure as an equivalent internal design pressure (assuming E=1.0) in the formula for the shell or head at the location where the nozzle neck or other connection attaches to the vessel UG-45(b)(3) for vessels designed for both internal and external pressure, the greater of the thicknesses determined by (b)(1) or (b)(2) above; UG-45(b)(4) the minimum thickness* of standard wall pipe plus the thickness added for corrosion allowance on the connection; for nozzles larger than the largest pipe size included in ASME B36.10M, the wall thickness of that largest pipe size plus the thickness added for corrosion allowance on that connection. *The minimum thickness for all materials is that wall thickness listed in Table 2 of ASME B36.10M, less 12-1/2 %. For diameters other than those listed as standard in the Table, this shall be based upon the next larger pipe size.

29 The original drawing End Closures shows fabrication of these heads through machining. SA-479 is the material selection and is a specification for round bar. Round bar is not normally permitted for nozzles or heads of this size. However our investigation showed that Code Case 2155 would allow it. Code Case 2155 would require additional nondestructive examination on the material, including two transverse tensile tests, ultrasonic examination and penetrant examination. Based on how round bar is manufactured, there stood a good chance the material would fail the tensile tests.

30 Original End Closure Design

31 The End Closures could be made from SA-240 plate stock material. However Figure UW-13.3 requires that the requirements of Appendix 20 be met if the head were to be machined from plate. The Appendix requirements are similar to those of Code Case A forge material SA-182 could also be used for this requirements. UW-13 (f) (1) would still require a single tension test. We suggested and ultimately used a redesign of the head that avoided these issues.

32 The calculations for the vessel shell and the detail drawing selected a 10 SCH5S (10.75 OD x.134 wall) to meet the requirements. The minimum design metal temperature of -459F, below the UHA F requirement for impact testing of materials and production weld samples, led us to choose seamless pipe for this application. The availability of 10 SCH5S Seamless pipe caused SCH10S to be substituted.

33 Explanation of UHA-51 Because the vessel minimum design metal temperature is below -320F and the vessel is constructed of stainless steel, we must navigate the requirements of Part UHA. Part UHA discusses High Alloy Steels; for Cryogenic Pressure Vessels this means austenitic stainless steels, typically 304/304L or 316/316L. Of special interest to Cryogenic Pressure Vessels users and fabricators is paragraph UHA-51 pertaining to Impact Test Requirements. A summary of requirements follows for austenitic stainless steels. Regardless of minimum design metal temperatures (MDMT) impact tests are NOT required when the maximum obtainable test specimen is less than inches in thickness. For MDMT above 320F (-196C) impact tests are NOT required. For MDMT below 320F (-196C) impact tests are REQUIRED of all raw material, weld procedure qualifications for both the weld and heat affected zone for each type of weld process, and production weld test specimens (weld and heat affected zone) for each type of weld process.

34 Explanation of UHA-51 Impact tests may be Charpy Tests performed at 320F (-196C) only if Type 316L weld filler metal is used (and measured to have a Ferrite Number no greater than 5). Otherwise testing using ASTM E 1820 JIC method at the MDMT must be used. (As an aside we are not aware of any commercial firms capable of performing the E1820 tests at -459F.) UHA-51(g) exempts the impact test requirements above due to low stress. Where vessels that have a coincident ratio of design stress in tension to allowable stress of less than 0.35, impact test of materials and weld procedures and production welds is NOT required. The ultimate design of this vessel was such that we avoided having to perform Impact Testing through use of the UHA- 51(g) exemption on a portion of the components.

35 Redesign of the End Closures: We discussed with the customer why the selected the elliptical End Closure design. Driving the choice was a desire to smoothly channel the flow of two phase hydrogen through the inlet and outlet of the shell. After some back and forth discussion the ultimate design eliminated the material testing issues and the nozzles weld issues while being a more economical manufacturing solution.

36 Final End Closure Design

37 The final End Closure design consisted of a 1.50 thick 304SS SA240 plate with the knife-edge and bolt pattern of a 4.63 OD Conflat Flange machined in its outer face. An aluminum diverter was bolted to the inner face of the End Closure to address the customers desire for channeling the Hydrogen flow. This design eliminated all issues related to the shell inlet/outlet nozzle sizing and welding, material issues related to the machined elliptical end closures and was simpler to machine.

38 The original design of the Tube Side inlets and outlets consisted of 0.5 OD x.065 w tube brazed to the copper coils and were welded directly to the vessel shell at their exit points. Code requirements for wall thickness and full penetration welds at the shell precluded the use of this design. Instead we utilized a common cryogenic vessel design detail. The nozzles welded to the shell were constructed of 1 OD round bar with a pilot hole. The round bar was welded with full penetration welds to the shell, the pilot holes were then drilled out to accept the 0.5 OD tubes from the copper coils. The 0.5 OD tubes now not considered part of the pressure vessel, could be welded with a more appropriate sized fillet weld to the round bar nozzles.

39 Inlet/Outlet Nozzle

40 Final Design

41 Non-Destructive Test Requirements 1. Charpy impact testing of base metals and samples of production welds using Charpy Impact Tested Weld Procedure Specification. 2. Liquid penetrant testing of End Closure weld prep. Edges per UG-93 (4) for flat plates grater than 0.5 thick used to form corner joints and of the exposed prep area after welding. 3. Pneumatic testing of the vessel per UG Since we chose to pneumatic test, liquid penetrant testing of all nozzle welds and an structural welds greater than 0.25 in size per UW- 50.

42 Summary of Changes 1. Vessel Shell changed from welded to seamless pipe to address UHA-51 Impact Testing requirements. 2. End Plates material and configuration changed to address NDE requirements, nozzle thickness requirements, and full penetration weld requirements. 3. Coil inlet and outlet nozzle configuration changed to address nozzle thickness requirements and full penetration weld requirements. 4. NDE added: Charpy Impact Testing, Liquid Penetrant Testing, Hydrotest changed to Pneumatic Test.

43 Finished Helium/Hydrogen Heat Exchanger

44 Interior Subassembly

45 Interior Subassembly

46 Assembly of Coil into Shell

47 Interior Copper to Stainless Tube Detail

48 Interior Copper to Stainless Tube Detail

49 Exterior Stainless Tube Detail

50 Assembly prior to End Closures

51 Immersion Cold Shock after completion of welding

52 Immersion Cold Shock after completion of welding

53 Completed Helium/Hydrogen Heat Exchanger

54 Questions? Contact Ed Bonnema or Mike Seely at Meyer Tool