Attachment A Specifications for Surface Nuclear Moisture Density Gauges~2.pdf

DEPARTMENT OF TRANSPORTATION

CENTRAL BUREAU OF MATERIALS

SPECIFICATIONS FOR SURFACE NUCLEAR

Moisture-Density Gauges

GENERAL DESCRIPTION:

• The system shall be integrated into a single unit of rigid aluminum.

• The base may be cast or machined and shall have been stress relieved prior to machining to maintain a bottom surface which is flat within 0.005 inches over the entire surface of the instrument. Torquing of the top shell or any other part of the system to maintain flatness in the base will not be allowed. Attachment of the top shell must not cause any deformation to the base or bottom surface of the instrument.

• The upper shell or housing shall be constructed of a material durable enough to protect the internal electronic components and shall be water and dust resistant. If the shell or housing is painted, it must be painted with an epoxy paint, which will not chip or peel under normal field conditions. Powder coated finishes are acceptable.

• Positioning of the source rod, for backscatter and direct transmission density testing, shall be accomplished using an index rod. The index rod shall be mounted securely to the base of the instrument without any staking, shimming or epoxy. The index rod shall be placed in the base of the instrument such, that the height of the source rod tip, capsule end, is 0.010 inches +/- 0.005 inches above the test area when the source rod is in the backscatter testing position. The source rod handle shall be centered over the index rod so there is no contact between the source rod handle and the index rod other than the trigger mechanism. In the standard count position, the free end of the source rod handle shall have a maximum side play in either direction of 0.500 inches. There shall be no alternative mechanism used in place of the index rod that completely or partially encloses the source rod.

• The source rod must be removable with hand tools so all bearings, seals and wipers may be cleaned and lubricated and, if necessary, said bearings, seals and wipers shall be replaceable with hand tool without index rod removal. No adhesives may be used which would prevent replacement of the above without damage to other metal parts.

• The source rod shall move freely from the standard count position through all direct transmission positions in a smooth flow without any binding or pressure on the source rod handle, trigger mechanism or index rod.

• The system shall be capable of density determinations by backscatter and direct transmission methods over a range of 70 to 170 PCF. The direct transmission methods shall be capable of test in two (2) inch increments over a range of two (2) inches to eight (8) inches or twelve (12) inches as specified.

• The gamma source capsule shall be securely attached inside the source rod such that it cannot be separated from the rod by an accident during transportation or construction site conditions. The capsule shall be mounted in the source rod so as to maintain all sources at the same distance above the test area when placed in a backscatter test position. Said distance above the test area in the backscatter test position shall be -0.010 inches +/- 0.005 inches. Machining of the capsule end of the source rod, after the source capsule has been attached, which could affect the height of the source capsule (-0.010 inches +/- 0.005 inches) is prohibited. If there is any rotational or positional shift of the source capsule during the life of the instrument, the manufacturer shall repair the placement of the source capsule at no cost to the purchaser excluding transportation.

• Radioactive sources shall not exceed 10 mCi +/- 10 percent of Cesium 137 for the gamma source and 50 mCi +/- 10 percent of Americium241-Beryllium for the neutron source. All sources shall be double encapsulated in fusion welded stainless steel capsules. The use of recycled radioactive sources shall be prohibited.

• The electrical system may use alkaline or nickel-cadmium, nickel-metal hydride or lithium-ion rechargeable batteries. A low battery warning shall be included to warn the operator to change the alkaline batteries or recharge the nickel-cadmium batteries. The warning shall be at least twelve (12) hours before the system is automatically shut down. The battery charging system shall prevent damage to the rechargeable nickel-cadmium batteries or the electronic circuits in the event the charger is left connected for an indefinite period.

• The high voltage system and high voltage supplied to the detectors shall always be operable while the instrument is in a powered-up state. Switching off the high voltage circuit during test periods or during periods between tests will not be permitted. All electronics shall be contained in replacement modules and shall be bench repairable without the removal of any potting material. The modules shall be visible and accessible for repair and adjustment. Pulse height adjustments shall be accessible from the top without the removal of plates or other accessories.

Schematics, service manuals, parts lists and technical data shall be provided at no additional cost to the purchaser. Notification of revision changes and associated documentation shall be provided in a timely manner.

• The gamma detection system shall consist of not less than two (2) high temperature platinum lined Geiger-Mueller detectors. Each detector shall have a minimum active volume of 0.62 inches diameter and a length of at least 4.10 inches. The detectors must be operated at the exact voltage +/- 10 volts for which they were designed.

The density amplifier shall have separate adjustments for the signal of each detector, of which, the adjustment of the signal of each detector will be independent and not influential of the signal of the other detector. Detector signal shall not be adjusted through any alteration of the high voltage potential applied to said detector.

• The neutron detection system shall consist of a minimum of one (1) HE3 detector with a minimum active volume of 1.00 inches diameter and a length of at least 6.25 inches. The neutron detector shall be insensitive to gamma radiation below 1 MEV.

• The display unit (scaler) shall use a liquid crystal display (LCD) and be visible in bright sunlight without shading. The displayed figures shall have a minimum character height of 3/8 of an inch. The scaling and display circuits will consist of one (1) small circuit board consisting of integrated circuits and the LCD for increased reliability and reduced complexity. The measurement timing period shall be the industry standard periods of 15 seconds, one (1) minute and four (4) minutes. The accumulators must contain both moisture and density counts with either count being displayed as desired

• An advanced model shall comply with the same specifications as the standard model.

• The instrument must contain a microprocessor. The microprocessor shall possess but not be limited to the following functions:

A) Operations shall be menu driven for ease of operations.

B) Power Control - The instrument must be physically powered on; it may be optionally powered off automatically after extended periods (5 hours or more) of inactivity.

C) Test of display and processor functions.

D) Shall have automatic depth control with a manual option as a backup.

E) Control and display of calibration constants for selected depth of measurement.

(Access and display of calibration constants shall be restricted to the manufacturer and authorized service facilities only through the use of a special access code. Dissemination of the access code to the general user will not be permitted.) Additional secure functions must be accessed through a different code than that mentioned above; the additional code may be disseminated to the general user.

F) Selection of measurement time periods and units of measurement (PCF/ SI).

G) Statistical testing of the detection systems with all information available on demand.

H) Display of standard counts, previous standard counts or measurement counts even if the instrument has been powered down and restarted or battery replacement has been performed.

I) Computation and display of the following: wet density, dry density, moisture content and percent moisture.

J) Computation and display of percent compaction based upon a laboratory supplied wet or dry density, which may be input by the instrument operator.

K) Adjustment of the percent moisture, moisture content or dry density based upon a laboratory supplied constant, which may be input by the instrument operator.

L) Computation of void ratio and percent air voids based upon a laboratory supplied specific gravity, which may be input by the instrument operator.

M) Storage of test results shall be non-volatile storage of multiple test results.

Storage parameters shall consist of, but not limited to, date, time, project, location, offset, depth of test, timing period, counts, wet density, dry density, percent moisture, percent compaction, and any bias applied. Stored test results shall be downloadable using USB. In addition to USB, the device shall have Bluetooth capabilities or some other means capable of downloading test results to a smartphone.

N) The processor must be capable of containing a calibration, which may be adjusted by field calibration by the laboratory at any given time. Provisions shall be provided for a return to factory calibrations should errors arise from field calibration. Field calibration controls shall not be normally accessibly to the instrument operator.

• The calibration data shall be in tabulated form and calibrated to average-soil mass-attenuation coefficients using five (5) density standards consisting of granite, limestone, magnesium, aluminum, and magnesium/aluminum which have been calibrated to +/- 0.02 percent traceable to the National Institute of Standards and Technology (N.I.S.T.). The three metallic blocks shall be used to establish the relative shape of the calibration and the limestone and granite blocks to determine the calibration constants. The moisture calibration shall consist of at least two (2) standards, one (1) as near zero water content as possible and a second constructed of magnesium/polyethylene or aluminum/polyethylene for which the water equivalent has been computed. The thermalizing effects of carbon shall be accounted for in the computation. The density calibration range shall be 70 - 170 PCF. The density calibration precision, using a four (4) minute count, shall be +/-

0.26 PCF (backscatter), +/- 0.12 PCF (6 inch direct transmission) or less at a density of 120 PCF. The moisture calibration range shall be 0 - 40 PCF. The moisture calibration precision, using a four (4) minute count, shall be +/-0.16 PCF or less at

15 PCF.

• The system shall operate over an ambient air temperature range of -10 degrees Celsius to +70 degrees Celsius with a relative humidity of 93 percent, without condensation. The system shall be able to test materials with surface temperatures as high as +175 degrees Celsius. The system shall also be capable of storage at ambient temperatures of -55 degrees Celsius to 85 degrees Celsius with no adverse effects when withdrawn from storage.

• Accessories shall include:

1. Reference standard (not part of transport case) shall be constructed of:

(1) piece polyethylene equipped with a carrying handle and four (4) rubber feet at least 1/2 inch in diameter and 3/8 inches in height.

2. Additional accessories shall consist of:

transport case scraper plate, drill rod, drill rod guide (scraper plate)

• The design of the scraper plate shall be such that its perimeter duplicates the outline of the bottom surface of the instrument with the drill rod guide oriented to emulate the source rod position.

battery charger (120 Volt A.C. and 12 Volt D.C.)

instruction manual and calibration data.

3. Calibration software capable of computing data for a 5 block calibration.