Interpret device and circuit operating from drawings Apply schematic readings in circuit diagnostics

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Chad Hicks
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1 Supplemental Read, follow, and understand schematics Electrical Hydraulic Pneumatic Interpret device and circuit operating from drawings Apply schematic readings in circuit diagnostics ECET 257 Consumer Power Electronics, PNC 2 1

2 Although it is common, not every manufacturer follows the same rules in schematics. This is a general guide. Always check your drawings against the machine. ECET 257 Consumer Power Electronics, PNC 3 All drawings are drawn with the device off and at rest Relays, switches, inputs, etc. ECET 257 Consumer Power Electronics, PNC 4 2

3 Electrical Schematics Only those that are indicated to intersect actually intersect ECET 257 Consumer Power Electronics, PNC 6 3

4 USUALLY use industry standards Marked with unique designators (R1, n1, etc) Commonly labeled with part number, values When in doubt, get data sheet ECET 257 Consumer Power Electronics, PNC 7 Commonly labeled, outlined ECET 257 Consumer Power Electronics, PNC 8 4

5 Commonly marked TP Allow for safe in-circuit measurement Matching point marked on board ECET 257 Consumer Power Electronics, PNC 9 Labeled on schematic, matches on-board designation ECET 257 Consumer Power Electronics, PNC 10 5

6 Pins may be marked on board to aid pinpoint diagnosis Board layout drawings aid in component location, board recognition ECET 257 Consumer Power Electronics, PNC 11 Coil associated with their outputs with dashed lines ECET 257 Consumer Power Electronics, PNC 12 6

7 Give tech overall theory of system Help guide initial diagnosis ECET 257 Consumer Power Electronics, PNC 13 Wire carrying signal commonly marked High/low states marked accordingly ECET 257 Consumer Power Electronics, PNC 14 7

8 Actual conduction patch Follow for possible unmarked test points ECET 257 Consumer Power Electronics, PNC 15 Hydraulic and Pneumatic Schematics 8

9 Many systems electric controlled hydraulic/pneumatic Servos Pump motor controls Pressure/flow sensors May be the only one to service a device. ECET 257 Consumer Power Electronics, PNC 17 Flow (Current) Movement of material Measured in volume/time (l/m, gal/hr) Pressure (Voltage) The exertion of force upon a surface by an object Measured in force/area (psi, n/m 2 ) Restriction (Resistance) Opposition to flow ECET 257 Consumer Power Electronics, PNC 18 9

10 Definition Measurement of force distributed over an area P = F/A Pascal s law Pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and perpendicular to the walls of the containing vessel Can be varied by changing flow rate or area applied Ex: 20 lbs applied to 1 square inch = 20 PSI ECET 257 Consumer Power Electronics, PNC 19 ECET 257 Consumer Power Electronics, PNC 20 10

11 Pressure varies inversely with volume Container must be sealed Decrease volume, pressure increases Increase volume, pressure decreases Gases are compressible Molecules can be moved closer Follow gas laws Liquids are not compressible Will transfer force throughout Will move to lower pressure area ECET 257 Consumer Power Electronics, PNC 21 ECET 257 Consumer Power Electronics, PNC 22 11

12 Create flow only Restrictions create pressure Displacement types Fixed - One output volume Variable volume adjustable, based on demand Reversible will have two triangles Fixed Variable ECET 257 Consumer Power Electronics, PNC 23 Converts hydraulic flow to mechanical movement Reversible will have two triangles Fixed Variable ECET 257 Consumer Power Electronics, PNC 24 12

13 The dashed line indicates internal passages Can have a spring, or can be pressure operated (sequence valve) Pilot operated (relay) Activated by another hydraulic pressure ECET 257 Consumer Power Electronics, PNC 25 Can be single or double acting Single one port, gravity or spring reset Double two port, hydraulic both directions ECET 257 Consumer Power Electronics, PNC 26 13

14 Direct fluid flow Manually or externally actuated Hydraulic, pneumatic, or electrical ECET 257 Consumer Power Electronics, PNC 27 Ex- Spool valve Multiple positions Allow for more control with less components ECET 257 Consumer Power Electronics, PNC 28 14

15 Hold unused reserve fluid Sight glass may be used to indicate level Can be several tank symbols in one drawing, but only one common tank ECET 257 Consumer Power Electronics, PNC 29 Indicate status of system Temperature Pressure Flow ECET 257 Consumer Power Electronics, PNC 30 15

16 Can use a ball and seat or a spring behind the ball ECET 257 Consumer Power Electronics, PNC 31 Clean environment whenever possible Seals may have tight tolerances for pressure Air must be purged OEM procedure Cycle cylinders till air returned to tank ECET 257 Consumer Power Electronics, PNC 32 16

17 ECET 257 Consumer Power Electronics, PNC 33 Similar to hydraulics Use of check valves, control valves, cylinders, tanks, and pumps Important differences Gases can be compressed Air usually vented to atmosphere ECET 257 Consumer Power Electronics, PNC 34 17

18 Pressurized Storage Bottle Regulator 3/2 Valves Pneumatic Cylinders with Speed Valves ECET 257 Consumer Power Electronics, PNC 35 18

The Secret of Hydraulic Schematics. BTPHydraulics www.iranfluidpower.com

The Secret of Hydraulic Schematics BTPHydraulics www.iranfluidpower.com www.iranfluidpower.com Table of Contents The Secret to Reading and Interpreting Hydraulic Schematics... 1 Hydraulic System Schematics...