Questions_and_responses_second_round_0004.pdf

Questions/Answers #24-29 that were not included in Mod 0002, are below:

24. Are vans and small vehicles allowed to move crews in and out of job site?

Response: Yes, with proper identification/authorization of all occupants.

25. Can the BOR give additional details on how the cranes are expected to operate in tandem mode?

Response: Ability to:

1. Perform all operations of single motions for all hooks, trolleys, and bridges for both cranes via one control source

2. Perform all operations tandem via one control source

3. All single hook, trolley and bridge movements

4. All levels of tandem movements: main hooks on one crane, all main hooks for both cranes, aux hooks on one crane, all aux hooks for both cranes, trolleys for one crane, trolleys for both cranes (near, far, all), both bridge movements.

26. Will both cranes exclusively be controlled via a single radio transmitter?

Response: Yes, this is one operation option. The option to operate each crane with its own controls will also be met. So two radio controls minimum will be supplied. Adequate interlocks and safeties will be in place to not be able to override crane operation from a controller that is already active for selected crane(s). See sect 41 22 20 2.01.T-Controls for allowable frequencies for radio.

27. Will two cab operators work together to make the moves required?

Response: For tandem operation, no, only one operator is required. For cranes being operated individually, one operator per crane would be required. HMI displayed for both crane should match.

28. Will one crane cab need to operate both cranes?

Response: For each powerplant: yes, at least one crane cab should have the ability to operate both cranes, while safely locking out any other controllers.

29. Page 177:

A. Is there a defined precision that the mechanical interlock must be able to hold?

Response: No, there is no defined precision. This is open to methods that best cover the ability for each crane, while in tandem, to hold some capacity to antiskew and hold the crane spacings to the lifting beam spans without the allowed float between cranes to create unsafe conditions.

B. Is the mechanical interlock only for the bridges? or is it for bridge to bridge and trolley pairs on each crane?

Response: Bridges only, not trolleys

C. Is it to be manually applied either at location of the bridge, remotely applied by radio, or is there to be some fancy semi auto mode required?

Response: All safe options would be considered. Manually applied would assume safe accesss, remote or semi auto may require a light indication of its current configuration with the ability to manually engage/disengage.

D. Does the load beam count as the “mechanical” interlock?

Response: No.

Questions/Answers below are from the second question period:

1. Question 10. Div. 41, part 2, 2.01 Bridge cranes, paragraph C-3, design features.

In the BOR's response to Question 10: "Exposed structure and framing. The exposed diagonals in the trusses, the exposed gear boxes and open ends of the cab are all key features."

How can there be open ends on the cab as we will be providing fully air-conditioned enclosed cab? See section 41 22 20-6 item S 1.

Response:

Retention of historical character defining features:

a. Design crane components to have similar size, shape, and scale of existing crane, in order to preserve and maintain their historical character.

b. Coatings: Match existing crane color and gloss of finish coats using manufacturer’s standard finishes, unless otherwise indicated, in accordance with Section 09 96 20 – Coating Performance Requirements.

Modern crane girder designs per CMAA have no exposed diagonals/trusses or rivets; girder box design has internal diaphragms. Please advise as to how this statement should be complied with?

Response:

The load bearing structural portions SHALL meet all codes and historical aesthetics would be cosmetic. I would like to see the contractor build off of industry standard design before replicating rivets.

There is only one crane design required in the submittals. The existing cranes have different aesthetic look. Is there to be a single crane design for both power houses or are we to add the additional effort and cost to design two different cranes?

Response: All 4 bridge cranes should be of the same design and capability in keeping with the revised historical character guidelines in 41 22 20 – Part 2, 2.01 C.

2. Question 41. Section 2.01.E.2- 2.01.E.2 – Motor torque: In accordance with NEMA MG-1, Design D, break down torque not less than 275 percent of full load rated torque. The motors will be NEMA Design “B” built for inverter duty - not NEMA Design D made for contactor control and across the line starting).Modern standard motors are not that high but they are close to 275% - Please clarify.

In the BOR's Response to question 41 it states: "CMAA 70 states that “squirrel cage motors shall have high starting torque, low starting current and high slip at full load, similar to NEMA Design D”.

Confirmation will be required that the design B motor will meet these requirements. Specifications will be revised. "

Follow-up:

Specified motor NEMA design D have a high slip that translates into poor speed regulation. We recommend using NEMA Design A motors on VFD applications.

VFD applications, especially in closed loop vector control, require low slip design like NEMA design A to achieve accurate and stable speed/torque regulation.

NEMA A motors can also handle transient overload that are likely to occur in general hoisting applications. Closed loop vector control method offers full load torque at 0 RPM and throughout the speed range. Our motors have a starting start torque ratio anywhere from 2.4 to 3.1 against nominal torque depending on the motor frame size.

Our VFDs are selected to be able to sustain the startup torque. Please advise if this is acceptable.

Response:

For AC motors used with inverters, CMAA 5.2.1.3.1 states “Motors shall be AC Induction NEMA Design A, NEMA Design B or IEC Design N, or any other suitable motor designs selected for the particular application. Motors should be inverter duty.

Amendment 2 changed the language to “Motor torque: In accordance with NEMA MG 1, Design D or B”

3. Div. 9, part 2, 2.01 B.4: Color and gloss: To match existing crane. Will the BOR provide Fed Std. no. or RAL number? Or provide sample for color matching by paint manufacturer?

Response: BOR will provide the Fed. Color standard to be used on all four cranes after award.

4. Div. 41, part 2, 2.01 E.10: Hooks. Existing Hook designs are significantly larger than necessary for hoist capacities. Main Hooks will be designed and sized to meet capacity and accommodate existing rotor lifting device; Aux Hooks will be designed to meet capacity per ASME B30.10. Should hook designs also consider matching existing hook design (size)?

Response:

Provided the hooks comply with CMAA 70 and ASME B30.10, slightly smaller hooks are acceptable.

5. Based on the information we have at this point it would seem that the TERO (Tribal Employment Rights Office) charges a 5% fee on total contract value for work within tribal lands. This is a significant amount on a project of this size. It is unclear if this is only for the portion of the work that occurs on tribal lands or if it is for the entire contract regardless of the percentage that occurs on tribal lands.

Furthermore, this fee is to be paid prior to the start of contract work.

Will the government permit a pay item in the schedule to compensate for this cost at the beginning of the contract?

Response: No

Will the government consider issuing two separate contracts in order to reduce the cost of this fee by separating the cost of the crane to be installed on tribal lands vs off tribal lands?

Response: No

6. We need trolley to trolley lifting beam detail to determine the minimum required distance between hooks trolley to trolley.

Response:

U-9256 and U-9272 are provided in Amendment 2 for Lifting beam drawings.

7. Due to supply chain concerns and material delivery times we request that the overall schedule be extended to a total of 1000 days.

Response: The period of performance will be extended to 1,000 days.

8. Need a drawing of the concrete floor at the entrance to both power houses at approximately elevation1012. We also require floor load rating at this location.

Response:

See drawing 222-D-7588, 222-D--2302 & 222-D-2230 included in amendment 2.

9. We need drawings and load rating for the parking on the north side of the left power house between the left power house and the 3rd power house.

Response:

The assumption is the parking lots match the same rating as the access roads.

10. Currently, the specification requires us to provide Load test skids with weights and leave them for the dam’s future use. We would like to know if this should be added to the Clin – 011 and Clin -014 Install bridge cranes ?

Response:

They should be in whatever CLINs that specify the load test.

11. Can Clin – 0006 and -0007 be changed from 100ft and 150ft cubed to “for the lump sum of”?

Estimating by the qty listed is not cohesive with how abatement on a crane project will go. We want to provide a total price for the abatement on all four cranes as an all-encompassing price for these two Clins.

Response:

The price schedule will remain as is.

12. Question: the wording below implies that cast iron gear reducers would not be acceptable on the project. Can the Bureau confirm that all gear housings will be required to be fabricated steel? Not allowing cast iron housings will increase the procurement cost of the complete package of gearboxes for the four cranes by about $ 750,000.00.

Response:

CMAA 70-4.8.4 states “All bearings shall be provided with proper lubrication or means of lubrication.

Bearing enclosures should be designed as far as practicable to exclude dirt and prevent leakage of oil or grease.” Provided the housing/enclosure can keep dirt out, prevent leakage, and adequately support the gears within the design loads as stated in CMAA 70-4.7, the material can be cast iron.

13. Do they have a certified weight for all of the load beam assemblies?

a. Trolley to Trolley Beam Assembly

b. Crane to Crane Beam Assembly

c. Does the stamped dead weight include the two trolley to trolley beam assemblies?

Response:

Photos of the lifting beams will be sent upon request.

14. Are we to leave the hoist capacities at 175-Tons each, or size them for 183-Tons as designed by Whiting in their Calculations on page U-9155?

Response:

All design is to 175-ton and marked and labeled accordingly. If the hoists are designed to 183-ton, they would still be labeled as 175-ton.

15. Can the BOR confirm the assembly weight of the largest piece they plan to lift? Response to question states 650-Tons, drawings show 625-Tons.

Response:

These loads stated in the question do not address the combined load at the hooks. Regardless of weight of rotor discrepancy, the largest weight the combined cranes can lift can be 700-ton. There is always a possibility a replacement rotor can weight more than the current 625 tons and increasing the total lift load.