1、b 0b 21i15763 325 NOTICE OF INACTIVATION FOR NEW DESIGN 1 INCH-POUND I MIL-G-7818 AMENDMENT 2 20 October 1999 SUPERSEDING AMENDMENT 1 29 May 1952 MILITARY SPECIFIC AT1 ON GAGE, FUEL QUANTITY, CAPACITOR TYPE, COMPENSATED, GENERAL SPECIFICATION FOR This amendment fomis a part of MIL-G-78 18, dated 26
2、November 195 1, and is approved for use by all Departments and Agencies of the Department of Defense. PAGE 1 * 2.1.1 : Delete “QQ-P-416 - Plating; Cadmium (Electrodeposited).” PAGE 3 3.2.2: Delete the last sentence and substitute the following: “Insofar as practicable, pivots, bearings, and gears sh
3、all not bind or shake and shall be frictionless.” PAGE 4 3.2.3: Add the following subparagraph: “3.2.3.1 The design of the circuit shall be such that the current in the leads running to the sensing electrodes of tank units and compensator sensing units shall in no case exceed 0.2 ampere. This requir
4、ement shall apply both to normal operating conditions and to any combination of the following abnormal conditions: (a) Short circuiting of any combination of electrodes in the tank unit or compensator sensing unit. (b) Short circuiting of any capacitor or any combination of capacitors elsewhere in t
5、he bridge circuit. AMSC N/A 1 of8 FSC 6680 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. e Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-G-78 18 AMENDMENT 2 (c) All switches and other adjustments in the bridg
6、e circuit set to any desired position.” 3.2.4: At the end of the first sentence add the following phrase: “including turbo-prop applications.” 3.5.1 : Delete the last sentence. 3.5.2: At the end of the first sentence add the following phrase: “unless approved by the procuring agency.” 3.5.3: Tank un
7、its. Delete in its entirety and substitute the following paragraph: “3.5.3 Tank units. The basic tank unit shall consist of a suitable capacitative arrangement of metallic conductors such as a pair of concentric cylinders electrically insulated from each other and forming a three-wire capacitor. The
8、 design shall be such that the tank unit can be disassembled and reassembled without the use of special tools, except as approved by the procuring agency. It shall be so constructed as to permit fuel into which the unit has been immersed to rise freely to its natural level between the conductors, so
9、 that up to this level, the fuel will serve as the dielectric substance. Above the level of the fuel, a mixture of air and vapor will be the dielectric substance. Unless otherwise approved, non- sensing portions of the sensing element shall not exceed the following dimensions: 0.600 inch at the flan
10、ge end and 0.400 inch at the opposite end for externally mounted tank units, except that 0.850 inch shall be allowed for the flanged end only for tank units including the compensator capacitors, and 0.400 inch at both ends for internally mounted tank units. It shall be so constructed as to preclude
11、the formation of deposits and sediments between the conductors. The minimum allowable distance between the conductors shall be O. 125 inch. The tank unit shall be designed to make electrical connections readily accessible for testing the tank unit and making calibration adjustments using a substitut
12、e precision capacitance. The materials used in the construction of the tank units shall be impervious to aircraft fuels.” PAGE 5 3.5.4 Intermediate device: Add the following sentence between the first and second sentences “The intermediate device shall be designed to provide readily accessible elect
13、rical connections for testing the gage system and making Calibration adjustments using substitute precision capacitors.” 3.5.5.1 : Delete the third sentence. PAGE 6 FIGURE 1: Delete “LENGTH OF CASE SHALL NOT EXCEED 4.25 INCHES.” 2 Provided by IHSNot for ResaleNo reproduction or networking permitted
14、without license from IHS-,-,-, MIL-G-7818 AMENDMENT 2 PAGE 7 FIGURE 2: Make the following changes: a. Opposite “TOLERANCES” delete “ANGLES Mo 1 5”. b. Delete the following note: “NOTE: LENGTH OF CASE SHALL NOT EXCEED 5 INCHES.” c. In the marking data for the “MAIN DIAL” under the second column, chan
15、ge as follows: (1) Opposite “FUEL QUANTITY,” delete “.140” and substitute “.125;” (2) Opposite “LBS X” delete “.100” and substitute “.062.” d. In the marking data for the “SUB-DIAL” in the first column, delete “X100” and substitute “X- 1 O0 or X- 1 O00 AS APPLICABLE.” e. Change sub-dial circle diame
16、ter from “0.718 fo.010” to “0.583 fO.010” PAGE 8 FIGURE 3: Make the following changes: a. Delete the following note: “NOTE: LENGTH OF CASE SHALL NOT EXCEED 4.25 INCHES.” b. Opposite “TOLERANCES” delete “ANGLES fo0-15”. PAGE 9 3.5.5.2 Indicator case: Add the following sentences at the end of the para
17、graph: foi snsitire indicators. The length limitations may be modified onIl, with the specific approval of the procuring agency.” “The case length shall not exceed 4.25 inches for nonsensitive indicators and 5.00 inches 3.5.5.5.2 Dial scale: In the fifth and seventh lines, delete “radius” and substi
18、tute “angle.” 3.5.5.5.3: In item (c) delete “usable” and add the following at the end of the sentence: “By tank volume is meant that part of the total volume measured by the gage.” PAGE 10 3.5.5.5.4 Dial markings: Add the following sentence between the third and fourth sentences: “The graduation mar
19、kings for the sub-dials on figures 2 and 3 shall be linear within +lo.” PAGE 11 3.9 Damping: Delete in its entirety and substitute the following paragraph: Pointer overshoot. The gage shall be designed to provide steady indication of the pointer. In approaching null the pointer shall not overshoot t
20、he final position more than one time and shall return to the final position within 2 seconds.” “3.9 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-G-78 18 AMENDMENT 2 3.1 1 : Gage failure indication: Delete in its entirety and substitute the f
21、ollowing paragraph: “3.1 1 Gape failure indication. The gage shall be provided with a readily accessible terminal connection for use with a remote test switch to indicate failure of gage operation. Operation of the external test switch shall cause the indicator pointer to rotate counterclockwise fro
22、m a balance point on any portion of the dial.” * 3.14.3: Delete in its entirety and substitute: Specification AN-P-32.” “3.14.3 Steel arts. Steel parts shall be zinc-plated where practicable in accordance with PAGE 12 3.16.4 Wiring diamam: Delete the entire paragraph. PAGE 13 4.2.4.1 Test instrument
23、: Delete the entire paragraph and substitute the following: “4.2.4.1 Test instrument. Whenever a master test instrument is specified for tests of gages, it shall be in the form of a precision variable capacitor or precision fixed capacitors. The accuracy of the precision capacitors, fixed or variabl
24、e, at 25 OC, shall be 0.2 percent for capacitances in excess of 50 uuf and 0.1 uuf for capacitances less than 50 uuf. For tests of totalizers the master test instrument shall consist of a suitable number of gages, or equivalent input devices, which have been calibrated to an accuracy of 0.2 percent.
25、” 4.2.4.2 Capacitance bridge: Delete the second sentence and substitute the following: “The accuracy of the bridge at an ambient temperature of 25 OC shall be 0.2 percent for capacitance in excess of 50 uuf and 0.1 uuf for capacitances less than 50 uuf.” PAGE 14 4.2.6 Delete the entire paragraph and
26、 substitute the following: measuring equipment shall be added to the specified tolerance for the given test or measurement .” “4.2.6 In all subsequent tests and measurements specified herein, the tolerance of the 4.3.1 SamDling instructions: In the first sentence add “two” immediately preceding “tot
27、alizers.” 4.3.1.2 Totalizer: Delete the paragraph in its entirety and substitute the following: combine the indications of three gages corresponding to relative tank volumes of 6:3: 1. The requirements for the totalizer indicator shall be the same as those for the gage indicator. Totalizers shall no
28、t be submitted for qualification unless approval has been previously authorized for individual gages associated with the totalizer, or the individual gages are submitted jointly with the totalizers for qualification.” “4.3.1.2 Totalizer. Totalizers submitted for qualification approval shall be desig
29、ned to 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-m 9999906 2LL57b5 Ti0 MIL-G-7818 AMENDMENT 2 4.3.1.2.1 Gage outputs for Totalizer: Delete the second and third sentences. 4.3.1.2.2: Totalizer inputs: Delete the paragraph in its entirety and s
30、ubstitute the following: “4.3.1.2.2 Totalizer inputs. The manufacturer shall furnish with the totalizers a set of three gages, provided with suitable calibration charts to serve as inputs for testing the totalizers. In lieu of the three gages, the manufacturer may submit artificial devices simulatin
31、g the gages. If artificial devices are submitted, the manufacturer shall provide sufficient data to veri that such devices are equivalent to the respective individual gages.” PAGE 15 Table I. Characterization of Tank Units for Qualification Tests: Under the fourth column in the sixteenth line change
32、 “22.24” to “25.54.” Under the sixth column on the last line, change “o” to read “2.4.” PAGE 16 4.3.1.4 Calibration data for qualification tests: Delete subparagraph “(c)” in its entirety. 4.4. i Calibration data for inspection tests: Delete item (h) and substitute the following: “(h) Relative posit
33、ions of tank units corresponding to locations in the airplane.” PAGE 17 4.4.2 Individual tests: Add the following at end of paragraph: “unless otherwise specified.” 4.4.2.2 Indicator operation at room temperature: Delete item (c) in its entirety and substitute: “(c) That. where applicable, the outpu
34、t signal at each major graduation is within I1/2 percent of the fixed design value at full scale. This test is required only for those indicators providing signals for totalizers.” In item (e) delete the clause following “the indicator.” PAGE 18 TABLE III Gage system calibration data: Change the hea
35、ding of the fifth column to read “Output Signal Where Applicable.” Revise note to read as follows: “NOTE: The last four columns of this table shall be extended to include capacitance values and totalizer output signals up to and including the highest major dial graduation. The capacitance values lis
36、ted in the extended portion of the second column are to 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- 999990b LL57bb 907 MIL-G-78 18 e AMENDMENT 2 be interpreted as applicable to those tests on which master test instruments are connected in lieu
37、 of the tank units.” PAGE 19 TABLE IV Totalizing gage calibration data (intermediate device and indicator): Change the heading of the first column to read: “Input Signal.” 4.4.2.3 Intermediate device otieration at room temperature: Subparagraph (c) fourth line delete “or voltage and/or resistance as
38、 applicable.” Add at end of subparagraph (c), “For totalizers a suitable input signal provided by a master test instrument shall be employed in lieu of input capacitance.” 4.4.2.4.1 Tank unit: In the second sentence immediately following “1 .O percent” add “or 0.5 uuf, whichever is greater.” 4.4.2.4
39、.2 Comtiensator sensinp unit: In the second sentence immediately following “1.5 percent” add “or 0.5 uuf, whichever is greater.” PAGE 20 O 4.4.2.6 Tank unit calibration: Add the following subparagraph: tank unit thereafter on the contract or order. In the event a tank unit fails to meet the specifie
40、d requirements. it shall be rejected. When a tank unit failure occurs the next 1 O consecutive tank units manufactured shall be subjected to the test specified in 4.4.2.6.” “4.4.2.6.1 The test specified in 4.4.2.6 shall be conducted on the first and every tenth 4.4.2.8 Dielectric strength: Add the f
41、ollowing to the last sentence: “and shall not be conducted between points where circuit elements would be damaged by the test voltage.” 4.4.3.1 Comtilete gage scale error at room temDerature: Delete the last sentence and substitute the following: “The difference between the observed readings and the
42、 readings specified shall not exceed 2.0 percent of indication +l .O percent of full scale indication.” PAGE 21 4.4.3.1.1 : In the second sentence change “the observed indicator readings” to “the specified indicator readings.” PAGE 22 4.4.3.3 1: Delete the seventh sentence and substitute the followi
43、ng: Where applicable, the output signals for the totalizer shall be recorded for each test point. ” 6 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-G-78 18 AMENDMENT 2 4.4.3.3.1 In the first sentence, delete “precision resistance decade andor v
44、oltage source, as applicable” and substitute the following: “master test instrument.” PAGE 24 4.4.3.10.3 Vibration isolation suitability - intermediate device: Delete the paragraph in its entirety. 4.4.3.10.4.1 Intermediate device vibration resonance: In the fifth sentence delete “1 hour” and substi
45、tute “2 hours.” Add the following sentence to the paragraph: “The intermediate device shock mount shall be included as a component part of the intermediate device for purposes of this test.” 4.4.3.10.4.2 Intermediate device vibration cycling: Delete the paragraph in its entirety. PAGE 25 4.4.3.10.4.
46、3 Tank unit resonance: In the seventh sentence delete “1 hour” and substitute “2 hours.” 4.4.3.10.4.4 Tank unit cvcling: Delete the paragraph in its entirety. 4.4.3.10.4.5 Delete the paragraph in its entirety. 4.4.4. I Vacuum tube replacement: Delete the third and fourth sentences and substitute: “E
47、ach vacuum tube or plug-in type amplifier employed in the gage system shall be removed individually and replaced consecutiyely with six tubes or amplifiers of the same type designation taken at random from stock. The difference in reading obtained with the original tube or amplifier and any of the s
48、tock replacement tubes or amplifiers shall not exceed 0.3 percent of full scale deflection.” PAGE 27 4.4.4.7 Tank unit immersion. Delete the eighth sentence and substitute the following: “The gage reading shall be noted after 5 minutes, and the change of indication from the original reading shall no
49、t exceed 2 percent of the full scale indication.” NOTE: The margins of this amendment are marked with asterisks to indicate where changes from the previous amendment were made. This was done as a convenience only and the Government assumes no liability whatsoever for any inaccuracies in these notations. Bidders and contractors are cautioned to evaluate the requirements of this document based on the entire content irrespective of the marginal notations
