1、 ENGINEERING STANDARDS Test Procedure SUPERCEDED EDS-T-7770 Determination of Heat Stability of Brake Fluids This standard may be applied only for current projects. It is Superceded for all future projects and replaced by GMW14714. Copyright 2011 General Motors Company All Rights Reserved November 20
2、11 Originating Department: GM Korea Engineering Standards Page 1 of 4 Version : 3 1 Scope Note: Nothing in this standard supersedes applicable laws and regulations. Note: In the event of conflict between the Korean and English language, the Korean language shall take precedence. 1.1 Purpose and Appl
3、icability. This test method shall be used to evaluate brake fluids with regard to their stability under conditions of high temperature use. This method provides a reasonable simulation of a vehicle driven in mountainous terrain. 2 References Note: Only the latest approved standards are applicable un
4、less otherwise specified. 2.1 External Standards/Specifications. None 2.2 GM Standards/Specifications. None 2.3 Additional References. None 3 Resources 3.1 Equipment and Reagents. 3.1.1 Apparatus and Ancillary Equipment Required. 3.1.1.1 Base plate of approx. size (800x500x50) mm. 3.1.1.2 Pedal pad
5、arrangement with scale for indicating pedal travel (see Sketch). 3.1.1.3 Main brake cylinder without booster (dual circuit brake system). 3.1.1.4 Graduated burette - 25 ml with rubber plug. 3.1.1.5 Sensitive pressure gauge with pressure release (class 0.6, 160 mm , indicating 0 to 60 bar). 3.1.1.6 C
6、onnectors. 3.1.1.7 Miscellaneous brake pipes with threaded pipe connections. 3.1.1.8 Brake hoses with brake pipes as clause 3.1.1.7 mounted to brake calipers see also clause 3.1.1.9. 3.1.1.9 Disc brake caliper (floating caliper), part number see appendix. 3.1.1.10 Heater 800W, infinitely variable be
7、tween 60 E and 600 E , with an orifice plate made from stainless steel. 3.1.1.11 Thermocouple Element: Deviating from the specification give in clause also a thermocouple element Fe/Constantan and a suitable recording device can be used. 3.1.1.12 Insulated hood, outer diameter 260 mm, internal diame
8、ter 230 mm, height 250 mm with 2 U-shaped openings to accommodate brake hoses. Perforated plate used as a support between heater and hood for assembled calipers. 3.1.1.13 Supports for base plate, clause 3.1.1.1 and the heater to clause 3.1.1.10. These supports must assure the arrangement described i
9、n clause 3.3. 3.1.2 Sources of Equipment. GM KOREA ENGINEERING STANDARDS EDS-T-7770 Copyright 2011 General Motors Company All Rights Reserved November 2011 Page 2 of 4 Version : 3 3.1.2.1 Equipment to clauses 3.1.1.1, 3.1.1.2, 3.1.1.12 and 3.1.1.13 must be manufactured. 3.1.2.2 Parts to 3.1.1.3, 3.1
10、.1.6, 3.1.1.7, 3.1.1.8 and 3.1.1.9 must be ordered from GM Korea. 3.2 Test Fluid. Test shall be carried out with brake fluid in the as received condition (i.e. no special pre-conditioning). Approximately 1 liter of brake fluid is required. 3.3 Test Apparatus (See Attached Sketch). A dual circuit mas
11、ter cylinder without brake booster but with foot pedal. For measurement of pedal travel, a pointer is mounted 146 mm from the pivot of the pedal and indicates travel on a suitable scale. A 25 ml burette is fitted into the filling orifice of the master cylinder. Two equal disc brake calipers, one con
12、nected to a thermo-couple, are secured together, bolted face to face. Two segments of disc brake calipers are connected to the front fitting of the master cylinder with brake pipe and original brake hoses. a precision manometer, reading 0 to 60 bar, is connected into the hose system by means of a by
13、-pass through distribution tubes. The air heater shall be arranged such, that the brake calipers, which are placed on the orifice plate, are about 20 cm below the master cylinder. A Ni/Cr-Ni thermocouple, to measure the temperature of the calipers, is firmly fixed and the calipers covered by the ins
14、ulated hood. The brake calipers shall be used only for one investigation (three tests with three measuring processes each), they must be then replaced by new, virgin calipers for further investigation. 4 Procedures 4.1 Conditions. 4.1.1 Test Conditions. Deviations from the requirements of this stand
15、ard shall have been agreed upon. Such requirements shall be specified on component drawings, test certificates, reports, etc. 4.2 Instructions. 4.2.1 The brake fluid to be tested is filled into the master cylinder and bled, de-aerated) by means of a screw plug in the rear brake circuit, after which
16、the brake calipers and finally the manometer are bled. 4.2.2 The cover is placed in position, the thermocouple and its recorder are connected and the burette fitted to the master cylinder. A first measurement is then taken at +23 E 5K by depressing the brake pedal by hand until the manometer records
17、 a pressure of 30 bar. At this point the pedal travel is recorded. The pedal is allowed to return to its original position and the level of fluid in the burette recorded. 4.2.3 The air heater is then switched on and the temperature of the brake calipers allowed to rise at approx. 2 to 3 min/10 E . F
18、or temperatures above +200 E the rise in temperature shall be 5 to 10 minutes/10 E . At intervals of 10 E rise in temperature the procedure as 4.2.2 is repeated to record pedal travel and burette reading. This procedure is repeated with increasing temperature until the point is reached where the pre
19、ssure of 30 bar cannot be achieved, and the pedal can be completely depressed without any pressure being recorded. 4.2.4 The air heater is then switched off, the cover hood removed and to avoid-further rise in temperature, the calipers are cooled with compressed air. Measurement of pedal travel and
20、burette reading are continued at 10 E intervals during the cooling period. The rate of cooling should be approximately 10 E every 2 minutes. 4.2.5 One test consists of a least three measuring processes as detailed in clauses 4.2.2 to 4.2.4 without bleeding the brake system. Three measuring processes
21、 per day can be performed. 4.2.6 Prior to starting the second and third tests, the brake hoses and calipers shall be flushed, using fluid from the reservoir on the master cylinder and bled(de-aerated), so that the previously heated brake fluid can be purged from the system. The volume of brake fluid
22、 used to purge the hoses and calipers shall be limited to 150 ml max, to avoid air entry into the brake system. After filling the master cylinder reservoir and prior to fitting the burette, the master cylinder shall be re-bled. 5 Data 5.1 Evaluation. 5.1.1 Up to a temperature of T1 =. E (T1 = brake
23、still operable) the measure expansion of the fluid (as shown by the burette readings) shall be proportional to the temperature rise9constant expansion coefficient). An over-proportional increase of the volume in the burette(caused by formation of gas) shall not occur below a temperature of T1=. E 5.
24、1.2 At T2 =. E (T2 = no brake pressure) complete depression of the pedal, accompanied by a reading of the manometer below 30 bar. T2 is generally +10 E higher than T1. GM KOREA ENGINEERING STANDARDS EDS-T-7770 Copyright 2011 General Motors Company All Rights Reserved November 2011 Page 3 of 4 Versio
25、n : 3 5.1.3 During the cooling period the full brake pressure of 30 bar shall be restored at T3 =. E (T3 = brake again operable.) 5.2 Expression of Results. Due to the passivation effect, only the measurements of the third test shall be used for determination of the test results. With reference to t
26、his method, the heat stability shall be expressed as the arithmetic average of the individual test results for T1=. E and T3=. E 6 Safety This standard may involve hazardous materials, operations, and equipment. This standard does not propose to address all the safety problems associated with its us
27、e. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 7 Notes 7.1 Glossary. Heat Stability: As determined by this test method, shall be defined as the limiting temperatures
28、 of the brake fluid operation during the respective heating and cooling periods. 7.2 Acronyms, Abbreviations, and Symbols. Not applicable. 8 Coding System This standard shall be referenced in other documents, drawings, etc., as follows: Heat Stability of Brake Fluid to EDS-T-7770 - T1 T3 E min E min
29、 Requirement Test Method Designation 9 Release and Revisions This standard was originated in March 1995. It was first approved by Engineering Standard Committee in March 1995. It was first published in March 1995. Issue / P9I8)Y Publication Date / 38 88 Description (Organization) / 9PP9I76 (:04.2P )
30、 3 NOV 2011 Apply new Engineering Standard Template. Superceded (Polymer / Organic Material Lab Team) / 4 d3TE:4 64 957 . F9I957 =* (G)8*4G D4 ) GM KOREA ENGINEERING STANDARDS EDS-T-7770 Copyright 2011 General Motors Company All Rights Reserved November 2011 Page 4 of 4 Version : 3 Sketch of the Test Apparatus
