MODIFICATION
66 -- Force Calibration Press, Aircraft Platform Scales - Force Calibration Press
- Notice Date
- 3/29/2011
- Notice Type
- Modification/Amendment
- NAICS
- 334516
— Analytical Laboratory Instrument Manufacturing
- Contracting Office
- Department of the Air Force, Air Force Materiel Command, 562 CBSG OMP (AFMETCAL), 813 Irving Wick Dr. W. Bldg 2, Heath, Ohio, 43056-6116, United States
- ZIP Code
- 43056-6116
- Solicitation Number
- FA2263-11-Q-0029
- Point of Contact
- Michael D Hickey, Phone: 740-788-5043
- E-Mail Address
-
michael.hickey@afmetcal.af.mil
(michael.hickey@afmetcal.af.mil)
- Small Business Set-Aside
- N/A
- Description
- Purcahse Description Rev. 1 dated 28 March 2011 *** 29 March 2011 *** Revised Purchase Description, REV. 1 has also been posted to the site. Questions/Comments and Responses The Scope states the Press will be used to calibrate scales with capacities of 5,000, 10,000, 20,000, 30,000 and 60,000 lbf from 10% to 100% of capacity. This implies the minimum force required to be applied will be 500 lbf. Paragraph 2.2 and 3.1 require the Press shall have a continuous operating range of 0 - 60,000 lbf minimum. It is not possible to build a hydraulic press that will meet the requirements of the Purchase Description when working at very low forces. Since the minimum force at which the Press will be used is 500 lbf (10% of a 5,000 lbf load cell) should the operating range be 500 - 60,000 lbf? RESPONSE: The press must be able to be continuously operated from 0 to 60,000 lbf, while the accuracy is required from 500 to 60,000 lbf. There is no error. Paragraph 2.3.1.1.1 requires the load cells be calibrated in accordance with ASTM E74-06 including zero. Paragraph 7.2.1 of ASTM E74-06 states, "In no case should the smallest force applied be below the theoretical lower limit of the instrument as defined by the values: 400 x resolution for Class A loading range and 2000 x resolution for Class AA." This excludes zero from being included in calibration and analysis of data according to ASTM E74-06. The two most recognized and used force calibration procedures are ASTM E74 and ISO 376 both exclude zero as a calibrated force. These procedures are written and reviewed by experts in the field of force calibration, including scientists from National Metrology Laboratories, such as NIST-USA and PTB- Germany. Neither ASTM E74 or ISO 376 permit the use of an instrument below the lowest non zero force applied at the time of calibration. This requirement is based on calibrating a load cell at forces less than 10% of its rated capacity assures the fitting of the calibration equation when the load cell is used below 10%. Another problem with using zero in the calibration equation is how zero is treated. According to Paragraph 8.1 of ASTM E74 deflection is defined as the difference between the reading under applied force and the average zero-force reading. Deflection is a net value and the zero-force reading will be a perfect zero for all three calibration runs. This will tend to artificially lower the standard deviation of the load cell. Based on internationally recognized force calibration procedures it is not appropriate to include zero-force readings in the calculation and analysis of data and the calculation of the standard deviation of the load cell. RESPONSE: The load cells shall be calibrated with a zero. The applicable calibration points must meet the requirements listed in your applicable uncertainty analysis. This document is not stating that the 0 must meet a specific requirement, but it will be used during calibration. No change will be made to the PD. Paragraph 2.3.1.2.1 requires the temperature effect on the load cell's zero for a change of 1 degree C and paragraph 2.3.1.3.1 requires the temperature effect on the load cell's actual rated output for a change of 1 degree C be included in the uncertainty analysis. Paragraph 4.3.1 states the Press will be operated in an ambient temperature of 67 to 79 degrees F. Since most force calibrations are referenced to a temperature of 23 degrees C the temperature will vary from 23 by -3.6 degrees C to +3.1 degrees C. Since the environment in which the press operates varies by more than 1 degree C the contribution to the uncertainty due to changes in temperature effect on zero and rated output should be based on a change of 3.6 degrees C. RESPONSE: Uncertainty budget shall be changed to reflect a maximum change of 3.6 degrees Celsius. Paragraph 2.4 requires the display shall be in pounds force. Many displays use a multiple point linearization to convert the load cell output to read in pounds force. Paragraph 2.3.1.1.3 requires the utilization of a second or third degree polynomial fit. The Purchase Description should require the displayed value be pounds force calculated using coefficients determined from the force and deflection values obtained in the calibration and the calibration equation for the proper degree of polynomial used to determine the standard deviation. RESPONSE: You are correct. If the cells are calibrated without an indicating device at the primary lab, then a second or third degree polynomial will be used. Then an additional error shall be included in the uncertainty analysis for using selected points from the polynomial calculation. Paragraph 3.3.1 refer to "Shift Test IAW NIST Handbook 44's Section 3". Section 3 of 2010 Handbook 44 deals with Liquid-Measuring Devices. What is the correct reference for the "Shift Test"? RESPONSE: This is a typographical error; it should say Shift Test in Section 2. Paragraph 3.4.1 requires a mounting fixture and indicator be supplied with each unit to verify perpendicularity. It further states the indicator will be used with an Air Force owned 18 inch Granite Square. Does each destination have a granite square? RESPONSE: Yes, each testing laboratory has an 18 inch Granite square. Paragraph 4.1.3 includes a requirement for decreasing force. No reference to decreasing force is made elsewhere in the Purchase Description. RESPONSE: This is an error. There should only be a requirement for an increasing force. This was only meant as a status, but due to the use of the equipment, the words have been removed from the PD. Paragraph 4.1.5.2.1 refers to Brand Name or equal ECS Composites Part Number 00017529 revision B. These cases are extremely expensive. Are Pelican Cases satisfactory? RESPONSE: Offerors are allowed to submit cases that are Brand Name or equal but must provide supporting documentation showing the case meets specifications of the Brand Name ECS Composites Part Number 00017529 revision B. There is a requirement for a 5 year warranty. We can offer five years on the frame, but not on the hydraulic seals or electronics. RESPONSE: There will be no change to the warranty. The 5 year warranty is required for all items in the system.
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-
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- Record
- SN02412143-W 20110331/110329234952-35c0ef3228bd36664dde71eea7fa700f (fbodaily.com)
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