RFP 457842 Questions Answers_72326.pdf

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RFP 457842 Questions & Answers

Attachment C - Technical Specification for the FHCAL - Doc Nr EIC-DET-SPC-021

1. Paragraph 3.2 - Materials

a. AISI 1020 steel alloy (now known as SAE Grade 1020 since AISI organization stopped supporting materials in 1995) is a typical "commodity" alloy only produced to a "Chemistry" and not any minimum mechanical properties nor any magnetic property testing. While the required chemistry is typical for this product and the min mechanical properties are typical for this alloy, the mills/distributors are taking exception to these mandatory min mechanical properties. The required listed specs in Para 3.3 are only for Chemistry and only apply to Plate thicknesses and do not apply to the 14 Ga (0.0747") material.

Testing for Yield and Tensile properties can be performed and provided "For Information Only"

Answer: SOW and Specification documents are being revised.

b. Magnetic Permeability testing per ASTM A773 - the Grade 1020 steel is not considered a "magnetic alloy" and not processed like an electrical steel alloy. Typically this Grade 1020 does not have the mill process controls to control magnetic permeability unless special order. The magnetic properties are impacted by the chemistry (especially Mn, Si), rolling practice, heat treatments, grain size, residual stress from slitting/flattening/leveling, etc. Only after production can this be tested and no procedures are provided to rework the material in case the results are out of the required range. Additionally, this test costs approx $2400 each and 4 samples are required per heat lot of steel so an extra $10,000/heat just for this test. No procedures are provided in case material is out of spec.

We can only test for Magnetic Permeability and provide the results "For Information Only"

Answer: SOW and Specification documents are being revised.

2. Paragraph 3.3 - Code/Standard Compliance

a. We have several issues with these ASTM callouts:

i. ASTM A6 - "General Requirements for Rolled Structural Steel Bars, Plates, Shapes, and Sheet Piling" - This standard does NOT APPLY for 14 ga sheet

- only the thicker plate

1. What specification should be used for the 14Ga 1020 sheet?

Answer: A6 should be replaced with A1011 (hot rolled) or ASTM A1008 (cold rolled)

ii. ASTM A773 "Standard Test Method for Direct Current Magnetic Properties of Low Coercivity Magnetic Materials Using Hysteresigraphs"

- Usually must be arranged through third-party outside testing labs since 1020 steel is a commercial alloy and not an electrical steel so the mills and distributors typically do not have in-house capabilities. Per Paragraph 4.1.2.1, this test must be performed on four samples at approx $2400 each (and min 10 day leadtime) - what is the required location for each of these samples? Should we take all from one sheet? Please clarify this testing requirement. As noted, we can only test for Magnetic Permeability and provide the results "For Information Only"

Answer: The samples should be evenly spaced across the sheets. The test can be arranged through third-party facilities.

iii. ASTM B733: “Standard Specification for Autocatalytic (Electroless) Nickel- Phosphorus Coatings on Metal -

Please identify where the rack/witness marks can be located. Should any secondary coating be applied to these marks? Where should thickness testing be performed on the parts.

Answer: Ideally, plating would use the 10x M6 threaded holes in the top of the unit. If this is not feasible, the towers are best placed on a rack on their short sides (opposite the recess in the absorber plates). A secondary coating is not necessary, but this is subject to confirmation in the pre-production units. The coating thickness can be tested on samples. Visual inspection of the quality of the coating is sufficient if the module dimensions and layer alignment are confirmed before the coating.

iv. ASTM A830 “Standard Specification for Plates, Carbon Steel, Structural Quality, Furnished to Chemical Composition Requirements” - This is directly applicable for Grade 1020 plate but does not apply to the 14ga 1020 sheet.

3. Paragraph 4.1.2.1 Acceptance Tests

a. "......magnetic permeability shall be measured for conformance to the technical specifications for four samples of each heat of steel".

i. As noted earlier, magnetic permeability is never conducted by mills/distributors for Grade 1020 steel, so this can be performed only after production. Please identify locations from each heat lot that these 4 test samples shall be taken. The typical cost for each magnetic permeability test is about $2400. Since it will be performed after production we will test and provide results "For Information Only"

Answer: Not specific locations are required, but the samples should be spaced out across the heat and not be too close to each other.

Weld scope on item 8. Note 3 calls for laser welding along the centerline of contacting faces for items 3, 4, 5, 6, and 9. Item 8, the 55 standard absorber plates, is not listed. Detail A shows staggered stitch welds every second plate across the full stack, which would include item 8.

These two callouts seem to conflict. Please confirm whether the item 8 plates require welding.

Answer: All absorber plates shall be welded as indicated in Detail A , so the list should include item 8.

Laser welding distortion data. If the item 8 plates do require welding, the change from electron beam to laser is significant for final geometry. Our experience is that laser welding produces roughly three times the distortion of electron beam on comparable joints due to higher heat input per inch of weld.

It sounded like prototype modules were built that proved out electron beam welding and established the 0.080 inch shrinkage allowance in Note 3. A&M completed a proof of concept and verified we could hold the drawing tolerances with electron beam. The change to laser introduces new variables in bow, twist, and transverse shrinkage that the existing 0.080 inch allowance may not cover.

Does BNL or ORNL have laser welding trial data or distortion measurements from prototype work that can be shared? Any data would shorten weld procedure development and reduce risk on the five preproduction units.

Answer: We do not have data from prototype modules with laser beam welding. Item 4 mentions post machining and the Specifications list outer dimensions for all modules and go/no-go gauges for the space between absorber plates instead of full GD&T.

Switch to Laser Welding.

a. Is this primarily being driven by cost?

i. Or is there some other driving force, e.g., throughput, supplier capacity, a specific technical deficiency in the established EB process, etc?

ii. If cost, we have a separate writeup that we would submit.

b. We have concerns about this switch as it will add many new variables that have not been fully vetted and tested as the EB welding process that has been fully validated.

c. Can EB welding still be accepted or is a factor as noted above driving this change?

Laser-beam welding should be sufficient for the materials and dimensions of the module assemblies. It is therefore more cost-efficient. There is no technical deficiency in the electron-beam welding process, but throughput and supplier capacity may affect the cost.

Proposals should address all requirements and exceptions need to be clearly documented and explained. This includes concerns about laser-beam welding and the use of electron-beam welding.

Nickel-Plating Option.

a. How is the option decided upon? Who decides? When is the decision made?

b. Is the decision applied to all modules or will it be applied per batch?

c. If not exercised, how will modules be protected from corrosion?

i. Weldments will require protection.

ii. Desiccant packs will likely not be enough to maintain protection.

The decision about nickel-plating will be made at the time of vendor selection. Similar to the previous comment, it will be based on the proposal details, cost, period of shipping and potential exposure until final detector assembly at ORNL. This should apply to all modules unless the production is distributed among a wide range of places. Note that cosmetic corrosion is acceptable and does not affect the use of the modules.

Magnetic Permeability Results.

a. These are still for informational purposes only.

b. Please confirm no accept/reject criterion has been added.

Magnetic permeability is for informational purposes only. It is not included in the acceptance tests.