This specification covers requirements for screen assemblies and their retaining/connecting Reflange, Inc. T-Con buttweld hubs used in liquid oxygen, liquid nitrogen, liquid hydrogen, gaseous hydrogen, gaseous helium, and gaseous nitrogen service as specified on the data sheet(s). Requirements herein shall govern design, material, fabrication, assembly, inspection, examination, testing, cleaning, packaging and delivery of the specified components. Vendor shall also provide specially modified Reflange, Inc. T-Con buttweld hubs, based on those specified herein, which position and retain the screen assembly in the pipe system. The government reserves the right to inspect any aspect of the fabrication and testing of this component.
2.0 APPLICABLE DOCUMENTS Screen requirements shall comply with the latest edition of the following referenced publications unless shown or specified otherwise:
NASA/SSC Standards and Specification Control Drawings
Stennis Space Center
SSC, Mississippi 39529-6000
SSC STD 79-001 Surface Cleanliness Requirements for SSC Fluid Systems
SSC STD 79-010 SSC Requirements for Materials Used in LOX/GOX Service
SSC DWG 54000-GM30 Specification for Materials used in LOX and GOX Service Exempt from Batch Test Requirements
SSC DWG 54000-GP11 Packaging and Preservation of Cleaned Components
American Society of Mechanical Engineers (ASME)
United Engineering Center
New York, New York 10017
ASME A182 Specification for Forged or rolled Alloy-Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service
ASME A312 Specification for Seamless and Welded Austenitic Stainless Steel Pipe
ASME B31.3 Process Piping
ASME Boiler and Pressure Vessel Code
3.0 DESIGN REQUIREMENTS
Screen assemblies are to be conical (witch-hat), frustum, or stacked frustum-cone type screens with axial distance from plane of maximum diameter to parallel plane of minimum diameter or conical tip not exceeding 18 inches. The normal flow direction will be from minimum diameter or conical tip to maximum diameter, but the screen shall be designed to enable reverse flow.
Screen assembly shall have fully supported wire mesh sized such that the spherical particles having diameters larger than that specified on the data sheet(s) cannot pass through the screen. A coarse wire mesh, 8 per inch by 8 per inch, shall be used for support or prevention of flow passage blockage of the primary wire mesh. A second coarse wire mesh, 8 per inch by 8 per inch, shall be overlaid onto the fine wire mesh on the concave outer surface to mitigate damage due to particle impact or sudden reverse flow conditions. 1 Perforated sheet is not acceptable as a substitute for a wire mesh screen. It is acceptable as a structural support for the screen to prevent collapse; provided that the perforations are circular holes and they each have a diameter that is 30 or more times larger than the minimum opening cross section width dimension of the supported wire mesh.
Screen assembly shall be designed such that pressure drop is less than the value indicated on the data sheet. Screen assembly shall be designed to prevent collapse and wire mesh failure with 100 psid or higher differential pressure across the screen in both the normal and reverse flow directions.
Screen assembly shall be designed such that pressure pulses (compression waves) at sonic velocity in water traveling in both the normal and the reverse flow direction do not collapse the screen assembly and do not cause wire mesh failure (i.e. water hammer condition).
Screen assembly shall be configured such that there are no zero velocity (stagnation) regions radially inboard of the screen retainer ring under normal and reverse in-service flow conditions; including regions near the inside diameter of the screen retainer ring.
Screen assembly shall be configured to enable visual examination of the entire outside surface area of the primary (fine) wire mesh and pressure spraying of all surfaces with liquid cleaning solvents. The screen assembly configuration shall enable complete and rapid draining as well as hot gas drying to remove cleaning liquids from all surfaces.
Screen assembly shall be designed such that it can be directly installed into the associated pipe system as a complete unit between two modified mating Reflange T-Con or R-Con hubs as specified in the data sheet(s). Use of hub seal ring as part of the screen assembly or direct attachment of screen assemblies to hub seal rings is prohibited. Vendor shall provide detailed design that shows required hub modifications for installation and retention of the screen assemblies.
The screen assembly shall be designed such that it can be installed and removed from pipe system without cutting, welding, or brazing.
Threaded fasteners are not permitted for retention or preloading of screen assembly in pipe system.
The screen retainer ring shall be designed such that it is radially preloaded to hold the screen assembly axial centerline colinear with the T or R-Con hub axial centerlines while screen is chilled to –423 degrees Fahrenheit and while T or R-Con hubs are at –100 degrees Fahrenheit. Any reliance on sliding friction forces to provide this radial preload is unacceptable.
The screen assembly shall be designed such that it is axially preloaded with force equal to 3000 lbf or higher when screen assembly is chilled to –423 degrees Fahrenheit and T-Con hubs are at –100 degrees Fahrenheit. Any reliance on sliding friction forces to provide this axial preload is unacceptable.
Screen assembly shall be designed such that no parts are stressed beyond 90% of minimum yield stresses as listed in ANSI B31.3 when screen assembly is at –100 degrees Fahrenheit and T-Con hubs are at temperature of –423 degrees Fahrenheit.
Screen assembly shall be designed such that required axial and radial preloads are maintained throughout all thermal and differential thermal transient conditions, where hubs and screen assembly can cycle between –100 and –423 degrees Fahrenheit and where maximum temperature difference between hubs and screen assembly is as high as 323 degrees Fahrenheit.
If springs are used to provide preloading, design shall include features that prevent reverse buckling of all springs. If springs are used to provide preloading, design shall include provisions that prevent inadvertent removal from and incorrect reinstallation of springs onto the screen assembly.
The screen assembly shall include provisions to enable mass transfer of fluid into and out of all enclosed cavities between screen retainer ring, hub, seal ring, and spring surfaces; i.e. 1/16” or 1/8” vent ports or grooves for fluid venting.
All welding and brazing procedures, filler metals, procedure qualifications, and welder qualifications shall conform to all applicable requirements of ASME Boiler and Pressure Vessel Code or ASME B31.3. All welds and brazed joints shall be accessible to visual inspection and shall be 100% dye-penetrant inspected in accordance with ASME B31.3 or ASME Boiler and Pressure Vessel Code requirements. Weld filler metal shall have same nominal composition as the base metal. All welding and brazing procedures shall be qualified to –320 degrees Fahrenheit for liquid oxygen service and –423 degrees Fahrenheit for liquid hydrogen service. This qualification includes Charpy V-Notch or buyer’s approved alternate toughness testing of weld or braze test coupons at the minimum service temperature.
The maximum allowable working pressure (MAWP) for each screen assembly and the (maximum) fluid pressure at the screen inlet are specified on individual data sheets. The modified Reflange T-Con hubs, used to contain the screen assemblies, shall be designed and fabricated to contain the MAWP and specified screen inlet pressure in conformance with the requirements of ASME B31.3.
All internal surfaces of screens, hubs, and filters, wetted by service media, (except for wire cloth and wire mesh) shall be 250 RMS or smoother for proper precision cleaning.
Conceptual drawings depicting the proposed screen design including the materials of construction shall be submitted to NASA for review prior to fabrication of parts to ensure compliance with the specification.
4.0 MATERIALS T or R-Con hubs used to hold and support the screen assemblies shall be ASTM A182 Grade F304/304L dual rated or Grade F316/316L dual rated stainless steel.
Each materials of construction shall conform to a governing ASTM or ASME material specification and Certified Material Test Report (CMTR) documentation shall be provided for each material used in screen assembly construction.
Alternate materials may be substituted for materials stated on the data sheet provided that NASA (buyer) approval is obtained in writing prior to start of fabrication.
Screen assembly non-metallic elements for oxygen, helium, and nitrogen service shall be designed according to SSC DWG 54000-GM30, Specification for Materials used in LOX and GOX Service Exempt from Batch Test Requirements.
5.0 MARKING Each screen assembly shall have permanent markings at conspicuous visually accessible locations (preferably along the outer circumference of the screen assembly) that includes the following information:
Flow Direction Arrow at two locations on outer circumference of screen assembly (retainer ring) spaced 180 degrees apart
Governing Specification Number
Micron Rating or Mesh and Wire Size of Primary Wire Cloth
Each buttweld hub shall be permanently marked on an external surface with the hub part number, pressure rating, and hub material including the ASTM A182 material specification.
Permanent markings shall be applied with electro-chemical etching or stamping. Minimum required wall thicknesses shall be maintained above minimum requirements.
6.0 CLEANING Each screen assembly shall be cleaned according to the requirements of NASA/SSC Standard 79-001 per data sheet specifications. The cleanliness level shall be maintained throughout final assembly, final leakage testing, and packaging. Each screen assembly shall be packaged separately from the connecting buttweld hubs that will be used to retain and position the screen assemblies in the pipe system. Precision cleaning of the screen assembly and final packaging shall be performed after all testing required by this specification.
Individual cleanliness certification cards identifying the component locator number, serial number, and clean level are required for each component.
7.0 TESTING Vendor shall perform a fit up test for each screen assembly prior to precision cleaning, packaging, and shipment.
Vendor shall perform flow and differential pressure tests, actual applied load tests, or shall provide analytical computations and data to demonstrate that each screen assembly will not collapse under conditions specified in Section 3 and the data sheet of this specification. The analyses shall include all simplifying assumptions used, margins and methods used to provide conservatism, empirical test data for other similar wire mesh and screen assembly configurations if used, and all reference sources for equations and algorithms used in the analyses; i.e. the analyses shall provide the buyer, NASA, a level of confidence that screens will not fail under operating conditions that is equal to or better than confidence level obtained by actual tests. All analyses shall properly account for material property variations and uncertainties associated with heat affected zones and filler metal regions at the welded and brazed joints. Combinations of actual tests and analyses to support and complement each other are also permitted as well as encouraged.
Vendor shall supply 3 copies of all weld and braze inspection documents with delivery of hardware.
8.0 PACKAGING AND DELIVERY The manufacturer shall be responsible to prepare shipment of screen assembly to arrive undamaged with cleanliness intact. The screen shall be packaged in accordance with NASA/SSC Drawing 54000-GP11 Packaging and Preservation of Cleaned Components.
All GN, HE, LO and GO components shall be treated as LO/GO components (section 3.3). All LH and GH components shall be treated as NON-LO/GO components (section 3.4).
Connecting hubs shall be commercially cleaned to be free of visible contaminants prior to packaging and shipment.
Vendor shall provide packaging and crating procedures for shipment of hardware one month prior to shipment of hardware. With these procedures, vendor shall also provide instructions for unpacking, handling, transport, precision cleaning, and installation of screen assemblies such that damage to hardware is prevented.
9.0 WARRANTY The screen furnished under this specification shall be new equipment purchased from the original equipment manufacturer or their authorized distributor.
The vendor shall supply a certificate of conformance with the screen certifying that the screen has met all of the requirements of this specification.
The screen furnished under this specification shall be guaranteed against defective materials, design, and workmanship for a period of one year from the date of acceptance. Upon the receipt of notice from the Government of failure of any part of the guaranteed equipment during the guaranty period, new replacement parts shall be furnished and installed promptly by the supplier at no additional cost to the Government. The supplier shall acknowledge his responsibility under these guarantee provisions by letter, stating that the shipment and materials referred to herein be guaranteed and the inclusive dates of the guaranty period.
10.0 SUBMITTALS The following submittals are required as part of this specification:
Bid proposals must include the following information:
scaled conceptual design drawings including the configuration of each screen assembly as installed between the two mating hubs used to position and retain the screen assembly in the pipe system (actual geometric dimensions can be nominal or approximated pending final design calculations and analyses)
locations of clearance and interference fits with approximate value or range of the interferences or clearances
an outline and a general description stating the proposed testing procedures and analysis methods in accordance with requirements in the “Testing” section in this specification. The general description shall provide sufficient detail to provide the buyer a complete understanding of what will be performed, such that detailed test procedures could be developed from the description, and such that analytical methods are understood by the buyer.
Vendor shall provide all analyses and detailed test procedures within one month after award of contract. Buyer reserves the right to one review and critique where comments are provided within one week after receipt. Vendor is required to exercise good faith and sound engineering practices to assure that final design of screens will meet all requirements in this specification.
Vendor shall provide scale detailed design drawings prior to start of fabrication. A detailed drawing that depicts the screen assembly as installed between the mating hubs shall also be provided. The detailed design drawings shall include design details that depict materials of construction and all required modifications, including dimensional and angular tolerances, to Reflange T or R-Con hubs for positioning and retaining the screen assembly within the pipe system. Buyer reserves the right to provide review comments one week after receipt of these drawings.
All weld and brazing procedure specifications (WPS’s) and their supporting procedure qualification records (PQR’s) shall be provided by vendor for review and comment two weeks prior to start of any welding or brazing work.
Materials of construction that differ from the specification requirements described in paragraph 4.0. Buyer approval required.
Cleaning and verification procedures for review and comment in accordance with paragraph 6.0.
Test reports documenting the results of tests described in paragraph 7.0 within 1 week after completion of tests.
CMTR’s (certified material test reports) for all materials used in fabrication, including weld filler wire to be delivered with the hardware.
Certificates of conformance as described in paragraph 9.0.
A copy of all calculations associated with the hardware.
Unless otherwise specified the vendor shall ensure that their submittals are received by NASA a minimum of two weeks prior to the start of work governed by the respective submittal. This will enable NASA to review the submittal to ensure compliance with the requirements of the specification and to provide feedback to the contractor in a timely fashion. A vendor that commences work without a NASA review to ensure compliance of the submittal with the specification assumes all risks associated with rework, delay and other effects resulting from a nonconforming article should a subsequent review reveal that the vendor’s submittal did not comply with the requirements of the specification.
The submittals, when appropriate, may be submitted in electronic form instead of paper form (hard copies). When hard copies are submitted, 3 copies of each submittal are required.
INDIVIDUAL DATA SHEETS
SCREEN DATA SHEET # SC-10A2281-LO 2
WITCHES-HAT INLINE TYPE TO FIT BETWEEN REFLANGE HUBS
TYPE 304L, 316L OR 347 SS, RETAINER RING, SUPPORTS AND WIRE MESH (RIGIMESH, DUTCH TWILL WEAVE OR PLAIN SQUARE WEAVE). ALL WIRE MESHES SHALL BE MADE OF MONEL 400, MONEL K-500, NICKEL 200, OR BUYER APPROVED ALTERNATE MATERIAL.
ASTM A182 STAINLESS STEEL, TYPE 304/304L OR 316/316L DUAL RATED
ERBE OR EQUAL
MODEL OR FIG. NO.
PSK-E1-2003-FAC SHEET 3
CLEAN PER NASA/SSC STD 79-001 TO LEVEL 1X
* ITEMS TO BE FILLED IN BY MANUFACTURER
NO. OF FILTERS / STRAINERS
FILTER/STRAINER TAG NUMBERS:
SCREEN DATA SHEET # SC-10A2286-LH 3
WITCHES-HAT INLINE TYPE TO FIT BETWEEN REFLANGE HUBS
FILTRATION LEVEL (MICRONS):
300 to 800
DESIGN PRESSURE (PSIG)
DESIGN TEMPERATURE (F)
-423 TO +100
9150 gpm (90 lb/sec)
OPERATING PRESSURE DROP
50 PSID MAXIMUM ALLOWED AT DESIGN CONDITIONS
CLEAN (MIN.) PSI
DIRTY (MAX.) PSI
ELEMENT COLLAPSE PRESSURE (PSID)
UNIT BURST PRESSURE (PSIG)
MEDIUM USED FOR TESTING
WIRE CLOTH FLOW AREA (SQ.IN.)
* (6” BCK1 PIPE)
REFLANGE T-CON BUTTWELD HUBS OR REDUCING HUBS OR EQUAL, BCK1 PIPE
17-4 PH SILVER COATED STAINLESS STEEL
TYPE 304L, 316L OR 347 SS, RETAINER RING, SUPPORTS AND WIRE MESH (RIGIMESH, DUTCH TWILL WEAVE OR PLAIN SQUARE WEAVE)
ASTM A182 STAINLESS STEEL, TYPE 304/304L OR 316/316L DUAL RATED