A-2 Statement of Work for Vacuum Jacketed Piping.docx

Statement of Work for Vacuum Jacketed Piping

1. BACKGROUND AND PURPOSE

The National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR) in Gaithersburg, MD plans on installing a liquid deuterium (LD2) cold neutron source that will replace an existing liquid hydrogen (LH2) cold neutron source. The LD2 cold neutron source architecture includes an LD2 cryostat, condenser heat exchanger, warm deuterium ballast tank, and interconnecting piping. The LD2 condenser heat exchanger will be connected to an existing helium refrigeration cryoplant via cryogenic helium vacuum jacketed (VJ) piping. New helium VJ piping assemblies are required to adapt the existing VJ piping to the new LD2 condenser while maintaining service to a second existing VJ helium piping circuit that supplies another helium/hydrogen condenser.

2. ATTACHMENTS

The drawings and STEP files provided with this statement of work are for layout purposes only. The contractor is responsible for creating a detailed design and plan to manufacture each spool.

2.1 Helium piping assembly drawings

2.1.1 002-3265 R1.1 PW RETURN SPOOL ASSEMBLY

2.1.2 002-3266 R1.1 RETURN SPOOL

2.1.3 002-3267 R1.1 RETURN ADAPTER SPOOL

2.1.4 002-3278 R1.1 HEATER SPOOL

2.2 Helium piping assembly 3D models

2.2.1 002-3265 R1.1.stp

2.2.2 002-3266 R1.1.stp

2.2.3 002-3267 R1.1.stp

2.2.4 002-3278 R1.1.stp

3. SCOPE OF PROJECT

The required components consist of four VJ spools with instrumentation. These spools will replace four existing spools to adapt the existing VJ piping system to the new LD2 cold neutron source condenser. New instrumentation will be incorporated to improve process control and monitoring capability. The largest spool replaces the existing helium return spool, relocates a control valve, and incorporates two venturi or orifice style flow meters with temperature sensing diodes. A smaller spool connects an existing return line from a liquid hydrogen cold source located on the far side of the reactor to the new return spool. A coupling spool links the LD2 condenser helium outlet location to the return spool. Another coupling spool that incorporates an inline heater will adapt the existing helium supply spool to the new LD2 condenser inlet location.

A conceptual CAD model has been developed by NCNR and is detailed in NCNR drawings and 3D models listed in Appendix 1, included as a part of this document. Dimensions for the assembly can be taken from the 3-D models and drawings.

The general scope of this project is:

· Detailed design of four cryogenic helium VJ piping assemblies

· Fabrication and testing of those assemblies

· Delivery of completed assemblies to the NCNR

· Documentation package including design calculations, material certifications, as-built drawings, 3D models, etc.

4. DESIGN AND FABRICATION REQUIREMENTS

The layout and general features required for each spool is shown in the included drawings. Some items required for vacuum jacketed cryogenic lines such as expansion joints and vacuum jacket service ports are not shown. A schematic of the spool features is shown in figure one. A model-based view is shown in figure two.

Figure 1 - VJ pipe spools schematic

Figure 2 - VJ pipe spools rendering

4.1 Operating conditions

The working fluid is gaseous helium. System pressures and temperatures are provided in table 4.1.

Table 4.1 - System operating parameters

4.2 Insulation

The inner process piping shall be insulated with a static vacuum with Multi-Layer Insulation and a chemical gettering system. No loose insulation or powders are permitted. Maximum allowable warm vacuum is 10 microns Hg. Acceptable heat leak rates at 17 K provided in table 4.2.

Table 4.2 - Acceptable heat leak rates at 17 K

4.3 Bayonet connections

Existing VJ piping has both male and female bayonet connections, manufactured by different companies. Table 4.3 provides a schedule of bayonet connections that the new spools must mate with. These connections are also indicated on the included layout drawings.

Table 4.3 – Bayonet connections All required O-rings and v-band clamps shall be included in the scope of delivery.

4.4 Expansion segments

Expansion joints shall be incorporated, as necessary, in the spool jacket pipe to compensate for the differential rate of expansion and contraction between the inner line and jacket pipe.

4.5 Flexible segments

Flexible segments shall be incorporated to allow for ease of installation and to accommodate misalignments in piping. Drawing 002-3265 shows the location and length of a flexible segment that matches the layout of the existing spool. NCNR has favorable experience with this arrangement aiding installation and alignment of this spool. As part of the detailed design effort it is expected that the contractor, based on their experience, may suggest other places where incorporation of flexible segments is advisable for installation reasons.

4.6 Evacuation and relief ports

Each spool piece shall be equipped with a one inch combination evacuation and relief port (including vacuum gage tube manifold isolation valve and dust cover assembly). Each spool will be delivered with a thermocouple vacuum gauge tube installed (Teledyne Type DV-6R). The contractor shall also supply two (2) removable valve operators.

4.7 Instrumentation

Two flow meters are required in spool 002-3266. The general positions are indicated in the included drawing and in figures 1 and 2. The flow meters shall be integrated into the VJ return spool and may be either orifice or venturi flow meters. Flow meters shall be positioned with the required amount of straight pipe both upstream and downstream to insure accurate flow readings. Flow meters shall be instrumented with helium temperature measurement, pressure and differential pressure transmitters. Pressure taps shall be designed to minimize thermal leakage from the vacuum jacket passthroughs. Temperature sensor wiring shall be detailed (thermally lagged) to minimize thermal conduction from the exterior connection to the sensor. Flow meter and temperature sensor specifications are provided in table 4.4.

Table 4.4 - Flow meter parameters and components

4.8 Valves

Two control valves are included in the scope of this project. While these valves are indicated on the layout drawing with valve sizes, valves shall be sized using appropriate calculations to the flow rates shown below at the nominal fluid conditions specified in table 4.1

Table 4.5 - 2 inch line control valve parameters

Table 4.6 - 1 1/2 inch line control valve parameters

4.9 Heater

A helium gas heater is required on the supply side as shown in figures 1 and 2. Integrating the heater into an adapter spool is preferred as it eliminates the need to replace an existing supply spool assembly. Heater specifications are provided in table 4.7.

Table 4.7 - Inline helium heater specifications The heater shall have a fully redundant heating capability. No wiring or heating elements shall be shared. However, the wiring may use a common electrical feedthrough. Heater element wiring inside the vacuum jacket shall be accessible without cutting the vacuum jacket. Heater controls and external wiring shall be provided by the NCNR.

4.10 Supports and fixations

Any parts of supporting structures in contact with the VJ pipe shall be made of the same material as the supported lines or compatible materials to avoid galvanic corrosion. All components necessary for installation and fixing shall be included in the scope of delivery. Supports shall be either stainless steel, or painted steel to prevent corrosion.

Mounting brackets for transducers are outside the scope of this requirement. NCNR will design and procure brackets for mounting these items separately.

4.11 Routings and interfaces

The two piping spools will be connected to existing VJ piping bayonets at the NCNR, building 235, room C100. Room C100 contains the NCNR reactor and cold sources. The piping spools shall be routed above existing neutron guide shielding and below an existing catwalk. A model of the anticipated layout is shown in figure 3. Design/Layout decisions will be made in coordination with NCNR to verify that no conflicts are created with existing equipment not described in this document or supporting drawings.

Figure 3. – VJ spool routing in C100 (note existing VJ piping green, new piping gray)

5. FABRICATION AND PERFORMANCE

5.1 Materials of Construction

For all pressure-bearing process pipes, the choice of materials shall comply with ASME/ANSI B31.3 and shall be fabricated of austenitic stainless steel. All flexible segments shall be covered with a protective metal braid. Expansion joints are exempt from this requirement.

Table 5.1 - Materials of construction

5.2 Welding

All welding shall be conducted using the GTAW process. Process lines shall be all full penetration butt-welded construction. No socket welds are allowable. Weldors and Welding Procedure Specifications (WPS) shall be qualified to ASME Section IX for all welding work performed by the contractor or their sub-contractors. Each weld joint shall be covered by a WPS. Contractor shall guarantee that all WPS comply with the requirements of ASME/ANSI B31.3.

5.3 Cleaning

All surfaces shall be free from moisture, dirt, organic compounds, scale, paint or other foreign matter, and suitable for cryogenic helium service. Shop fabricated components shall be suitably sealed to prevent contamination during shipment.

6. QUALITY ASSURANCE REQUIREMENTS

6.1 Codes and Standards

The spools must conform to applicable US standards regulating safety aspects for pressurized piping systems. The applicable construction code for design, choice of materials, manufacturing, installation, inspections and controls of the piping in this specification is ASME/ANSI B31.3 – Process Piping, latest edition.

6.2 Testing and Inspections

6.2.1 General

The scope of this project includes tests to prove the integrity of the spools. These tests will include examination and pressure testing in accordance with ASME/ANSI B31.3.

6.2.2 Jacket vacuum retention

A piping spool shall be deemed acceptable if there is no rise in pressure, other than from outgassing, after pump down. Outgassing shall be limited to a small rise in pressure immediately following pump down followed by several days of no pressure increase. The maximum allowable pressure due to outgassing is 35 microns as measured over a seven day period. A steady increase throughout the test period is unacceptable.

6.2.3 Helium line leak testing

The spools shall be 100% leak tested at ambient temperature in accordance with ASTM E499, latest edition. The helium leak rate shall not exceed 1x10-9 std. cc/sec.

7. WORKSITE AND LOGISTICS

NCNR anticipates that the VJ piping assembly will be, to the extent practical, a modular structure initially prepared at the manufacturer’s workshop.

Final installation and pressure test of the installed VJ piping spools shall be performed by NCNR staff. Supplier shall provide instructions for assembly of the spools.

8. DELIVERABLES

The Contractor shall provide all equipment and documentation as specified herein to NCNR within the period of performance:

1. VJ piping spools tested and delivered to NCNR.

2. Transducers and transmitters required for flow meter operation.

3. Integrated temperature sensors.

4. As-built drawings of each spool.

5. As-built STEP files of the 3D models of each spool. These can be envelope models if desired.

6. Assembly/installation procedures for spools.

7. Written certification that the requirements of section five are met.

8. Test certificates that confirm all tests required by section six are performed and that the spools meet the requirements described.

9. NIST traceable calibration certificates for all transducers and temperature sensors.

10. Design calculations for the control valve sizing.

11. Design calculations for the heater element sizing.

9. PERIOD OF PERFORMANCE

The period of performance is 16 weeks from award of contract.

10. WARRANTY

The contractor shall warrant the entire system for a period of a minimum of one (1) year after receipt of the equipment. Warranty shall be in accordance with terms in FAR 52.212-4. The warranty shall cover:

1. All deliverables, parts and labor,

1. Site visits as required, and

1. Contractor must respond to all warranty requests within 24 hours of the request.

Warranty shall commence upon acceptance of the equipment by the Government.

image1.png image2.png image3.png