Questions and Answers - N6426724R0017.pdf

N6426724R0017 NAVAIR VSC IDIQ Questions and Answers

3.9.1.2 Simultaneous connections for two 1/2 inch Rohr fittings and one NW25 (DN25 ISO-KF) fitting.

Please specify the exact style of 1/2 inch Rohr connector, i.e. male or female, straight or tapered

Intent was to specify 1/2-inch Rohr connectors as female/tapered with plugs as delivered.

3.9.2 Range. The VSC shall provide indications of the absolute vacuum in the test volume from the range of 10-4 to 1,000 Torr at the uncertainty specified in 3.9.4.

a) We are reading 10-4 as 1x10-4. Please confirm.

Confirmed.

b) 1x10-4 to 1000 Torr is understood as a control range for the pressure control. Please confirm.

Confirmed.

c) In order to “zero” reference standards, the VCS must be able to pump down to 1x10-5 Torr or lower. The Specification does not stipulate the “zero” pressure, the “base” pressure (lowest pressure achievable by the pumping system), as well as the time required to reach “zero” and “base” pressures. Although Paragraph

3.9.5 specifies the minimum speed requirement of 10 l/mins, the Specification, to the best of our knowledge, does not define the minimum volume of the test chamber. Chamber volume, size of the pimping system, “zero” and “base” pressure requirements will greatly affect the pump down times to reach “zero” and/or “base” pressure. Please clarify.

The equipment will be used to calibrate the components of a master unit used to calibrate (word used in spirit of specification referenced, not to the METCAL definition) vacuum furnace equipment for heat treating of metal to SAE specification AMS 2769. Based on the performance required for the most severe conditions and tolerances of that specification, request that prospective contractor propose the chamber volume, ‘zero’ pressure, and ‘base’ pressure required to meet that specification understanding that some of the additional requests below will be used as either input for these parameters or will be affected by the choices made. As long as the selected parameters are explicit and the effects of these parameters are disclosed in the proposal, it is acceptable for the supplier to make the choices that meet or exceed the minimum performance specified.

If additional information (e.g. – make/model of equipment being used/calibrated or manufacturer/model/type of sensors) would be beneficial, that additional information can be made available upon request.

3.9.6.4 Adapters. The VSC will include three accessory adapters, two of size 1/2 inch Rohr to an ISO-KF flange (size NW16 or NW25) and one of size 1/8 inch NPT to an ISO-KF flange (size NW16 or NW25).

This paragraph seems to be missing 1/4 inch MFL fitting to NW16 or NW25 adapters. Please clarify.

Concur. Please include the 1/4 inch MFL fitting to NW16 and NW25 adapters in the proposal.

To the best of our knowledge, the following important subjects are not defined in the Specification:

a) Type of pumping system. The similar systems nowadays are built with “dry” (oil free roughing pump), but this is not defined in the Specification.

Performance-based spec. As long as the supplied system meets or exceeds the performance specifications for pressure, speed, reliability, and maintainability, it will be acceptable.

b) Pressure control type. Calibrations systems may have Automatic or Manual pressure control. In addition, some systems may have an option of using either one. This is not defined in the Specification.

Unit shall be capable of operating under Automatic or Manual pressure control as selected prior to testing by the operator.

c) Pressure control resolution. How close the VCS should track to the required pressure set point. This is not defined in the Specification

Pressure control resolution shall be 1 x 10-5 Torr or better to meet or exceed the minimum resolution defined in Section

3.9.3 unless there is a need for a different resolution for the track.

d) An additional pressure gauge(s). Additional pressure gauge will be required to read “zero” and “base” pressures, as both values will be out of range of the Pressure Standards. This is not defined in the Specification

Concur. The government recognizes that gauges will be required to read these extremely low pressures. While it is not explicit in the specification, the expectation is that the necessary gauges would be included in the proposal. This was not necessarily an oversight, just an expectation that all gauges required to meet performance specifications would be called out in the specification and included in the price quoted.

e) Data Collection. Although MIL-PRF-38793 provides some guidance for the calibration process, the Specification does not provide any guidance or requirements on what data should be collected during calibration process. This may include, but not be limited to pressure readings from the Pressure standards, Pressure readings from UUTs, Calibration Set Point, Actual set point etc.

The intent is that the unit be capable of retaining setpoints required to perform any of the tests that the equipment be capable of performing – whether the settings were made in manual or automatic mode. In addition, it shall collect the pressure readings from UUT and standard along with any other data required to perform the calibration.

f) Data retention. The Specification does not provide any guidance on what king of data, if any, should be retained/saved after the completion of the calibration process.

Data collected shall be retained until manually erased or over-written by a subsequent cycle. When over-writing, NO data shall be left from previous cycles. Data fields not used in any given cycle can be flagged in any convenient way as long as it would be extremely difficult to confuse with actual data. Filling fields with spaces, dashes, 9’s or X’s have been used effectively in other processes.