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正确选择接地点，完善接地系统
良好的接地是保证PLC可靠工作的重要条件，可以避免偶然发生的电压冲击危害。接地的目的通常有两个，其一为了安全，其二是为了抑制干扰。完善的接地系统是PLC控制系统抗电磁干扰的重要措施。
PLC控制系统的地线包括系统地、屏蔽地、交流地和保护地等。接地系统混乱对PLC系统的干扰主要是各个接地点电位分布不均，不同接地点间存在地电位差，引起地环路电流，影响系统正常工作。例如电缆屏蔽层必须一点接地，如果电缆屏蔽层两端A、B都接地，就存在地电位差，有电流流过屏蔽层，当发生异常状态如雷击时，地线电流将更大。
此外，屏蔽层、接地线和大地有可能构成闭合环路，在变化磁场的作用下，屏蔽层内又会出现感应电流，通过屏蔽层与芯线之间的耦合，干扰信号回路。若系统地与其它接地处理混乱，所产生的地环流就可能在地线上产生不等电位分布，影响PLC内逻辑电路和模拟电路的正常工作。PLC工作的逻辑电压干扰容限较低，逻辑地电位的分布干扰容易影响PLC的逻辑运算和数据存贮，造成数据混乱、程序跑飞或死机。模拟地电位的分布将导致测量精度下降，引起对信号测控的严重失真和误动作。
6-VANE 10-5/8 IN OD BRASS PUMP IMPELLER D512996
FISHER 22B6094X012 SEAT RING VALVE REBUILD KIT D528119
SKF AOH 3068 G WITHDRAWAL SLEEVE ADAPTER D517639
SKF AOH3060G WITHDRAWAL SLEEVE ADAPTER D517640
HAYWARD TYLER 1E3739-010-3067 16-1/4IN OD STAINLESS PUMP IMPELLER D518616
WEIR RUBBER PUMP FRAME LINER INSERT D532907
WATTS RK 909 RT 4 0887751 RUBBER VALVE REPAIR KIT D579442
GEORG FISCHER GF EA21 ELECTRIC VALVE ACTUATOR 100-230V-AC 40VA D579463
FLOWSERVE EK663 QBBW-2250-5AAX/QBW-2125-5AAX PUMP SEAL KIT D580068
JOHN CRANE 1.375 TYPE 5611 X F 1 O58 1 MECHANICAL PUMP SEAL KIT D580061
FRISTAM 1659630000 STAINLESS FLK 50 ROTOR D575797
EIM 1240359 300FV-668 VALVE ACTUATOR CONTROLLER UNIT D577837
JOHN CRANE 2-1/8IN TYPE 315 MECHANICAL PUMP SEAL KIT D580104
CHESTERTON S10 70M 70MM PUMP CASSETTE CARTIDGE SEAL D580353
BWIP SK215 BW SEALS QB-2500-5A4N SK204 PUMP SEAL REPAIR KIT D580070
BAILEY AV121100 PNEUMATIC POSITIONER 150PSI D583687
IMO 3210/150 SCREW PUMP MINOR REPAIR KIT D581189
GORMAN RUPP 46512-192 PUMP SEAL ASSEMBLY D577116
4005227 2 VANE 18 IN OD 2-5/16 IN ID STAINLESS PUMP IMPELLER D582019
EL-O-MATIC ES0200.U2A03A.S22KS0 PNEUMATIC VALVE ACTUATOR D596918
SKF HA3128 4-15/16IN BEARING ADAPTER HOUSING ASSEMBLY D563367
EDWARDS NRD850000 CHEMRAZ VACUUM VALVE PAD KIT D591643
WILLIAMSON 7-083-03 07-0355-0000 PUMP SEAL D594931
JOHN CRANE 611QGCSBR337-22 STAINLESS MECHANICAL PUMP SEAL 1-3/8-IN D591195
FLOWSERVE 365094-00 STEEL PUMP THRUST BEARING HOUSING D591955
FLOWSERVE 027254-00-986A-78101-FLS BEARING LINE HOUSING COVER D591776
APV 03H-P-420144 N-4B-1540 PUMP ROTOR REPLACEMENT PART D592825
JOHN CRANE B06700 TYPE 21 PUMP SEAL ASSEMBLY 1.750IN D594084
GOULDS 3196 STI I-FRAME CENTRIFUGAL IRON PUMP POWER END D594148
UNITORQ M-470 K44 DLS PNEUMATIC VALVE ACTUATOR 150PSI D600205
FOXBORO C0140QN PROPORTIONAL PNEUMATIC CONTROL UNIT D569601
GORMAN RUPP 46512-192 PUMP SEAL ASSEMBLY D577115
MASONEILAN DRESSER SVI2-21121111 SVI-II VALVE POSITIONER D530404
ASCO 027477-001-D MP-C-078 110-125V-DC SOLENOID VALVE COIL D526978
DEAN PUMP R434 1X2X11-1/2IN PUMP POWER END D522390
BRAN LUEBBE 3G1D2E STROKE ADJUSTMENT ASSEMBLY D597372
TUCHENHAGEN STAINLESS ACTUATOR W/ VALVE STEM D568865
STAINLESS PUMP IMPELLER 67-088-696 2-1/8IN BORE 4-VANE 13-15/16IN OD D569090
ARMSTRONG STEEL PUMP CASING 1-1/2X3IN D569287
EIM VALVE CONTROLLER ASSEMBLY D564355
GOULDS 3756 CENTRIFUGAL PUMP CASING 2-1/2 X 3 - 7IN D596184
WORTHINGTON 1CNG42 PUMP POWER END D596114
RADIOMETER E32M002 METAL DOUBLE PLATINUM SENSOR ELECTRODE D597474
WEIR MK33970 6VCG 6 VANE 10-1/2IN STEEL PUMP IMPELLER 1-1/4IN NPT D599414
ROSEMOUNT 220-000138 TRANSMITTER DENSITY INTERFACE MODULE D569642
FLOWSERVE 15H 277 652398-06 7-VANE BRASS PUMP IMPELLER D538706
FLOWSERVE 802551ER 2X3 IN FLANGED STEEL PROCESS PUMP CASING D542468
WATTS RK 909 RT 4 0887751 RUBBER VALVE REPAIR KIT D579441
YOKOGAWA K1520LQ SENSOR CABLE 5M D576593
FISHER 4210 ELECTRONIC VALVE POSITION TRANSMITTER D598104
MORIN B-072U-S080 100PSI ROTARY VALVE ACTUATOR STAINLESS D535686
JOHN CRANE 706267N2 680XPC-SXF000-12 .750 PUMP SEAL ASSEMBLY D581809
SPX BRAN + LUEBBE 041213-8MM PUMP HEAD 8MM D584173
BENTLY NEVADA 293514-000 VP-R VALVE POSITION INDICATOR D590537
GOULDS 2E122 3196 I-FRAME IRON PUMP POWER END D587368
DRESSER N BLOWER SEAL KIT D591379
DURIRON DT46326AA STEEL CENTRIFUGAL PUMP CASING 3X1.5 - 82/65 D589174
MIDLAND B-590S SENSOR HEAD ASSEMBLY WITH CABLE D593285
MIDLAND B-590S SENSOR HEAD ASSEMBLY WITH CABLE D593285
ASCO 074073-002-D RED-HAT 240V-DC SOLENOID VALVE COIL KIT D537464
FISHER 15A6655X012 1-1/2 IN CONTROL VALVE SEAT RING D531463
13-1/2IN OD 2IN ID 6-VANE BRASS PUMP IMPELLER D515562
INGERSOLL RAND X1334TA36 PNEUMATIC COMPRESSOR FREE AIR UNLOADER D596455
EL-O-MATIC ES0150.U2A04A.22K0 PNEUMATIC VALVE ACTUATOR 116PSI D597255
16IN 6 VANE STEEL PUMP IMPELLER 2-1/2IN BORE D592058
FISHER 26A3351X012 CONTROL VALVE SEAT RING D536500
SKF AOH 24152 WITHDRAWAL SLEEVE ADAPTER D517638
SCHUNK OSE-A34-4 PNEUMATIC ROTARY ACTUATOR D593921
NELES JAMESBURY 32EX6 RAINTIGHT SNAP LIMIT SWITCH 125/250V-AC D587566
6-VANE 18IN OD 3-3/4 IN ID BRASS PUMP IMPELLER D538413
FLOWSERVE 2104723-001 STEEL PUMP SUCTION SIDE CASING D538446
008552-27 5-VANE 12-3/4 IN OD 1-3/4 IN ID STAINLESS PUMP IMPELLER D542937
6-VANE 10-1/2 IN OD BRASS PUMP IMPELLER D527163
FLOWSERVE XEDMA500AB3-4 NE3MA500AB3-4 STAINLESS COMPRESSION UNIT D522200
MASONEILAN DRESSER SVI2-21111111 SVI II VALVE POSITIONER D539594
DURA SEAL GEB2668884A BSI OSMEX675181 4-1/4IN STAINLESS PUMP SEAL D546221
SUDMO D620 SANITARY DOUBLE SEAT STAINLESS ACTUATOR REPLACEMENT PART D559069
LABOUR PUMP POWER END D522392
LABOUR SIZE 15 TYPE SZ PUMP POWER END D522394
DRESSER 48915013 ROOTS 16-1/4IN OD STEEL PUMP LOBE IMPELLER D532126
INGERSOLL RAND 6EH159B 2-1/4 IN SHAFT PUMP POWER END D546312
JAMESBURY QPX1C/K15 METSO QUADRA-POWR X 100PSI ACTUATOR D554743
6 VANE 16-1/2 IN OD 3-1/2 IN ID STEEL PUMP IMPELLER D525121
NORBRO 33 BRS 40 N10 10BAR PNEUMATIC VALVE ACTUATOR D535994
FLOWSERVE 005330-00 PUMP BOWL TOP 12HH ASSEMBLY 11BRG STEEL D532508
FISHER 22B6063X012 SEAT RING STAINLESS D545421
GEA BEL-IPS3/IPS4-SZ TUCHENHAGEN STAINLESS PNEUMATIC VALVE ACTUATOR D560683
ROTORK LA-2410-D-1-0.2/800-600-6 120V-AC ELECTRIC ACTUATOR D563999
FLOWSERVE B200DH AUTOMAX 150PSI PNEUMATIC ACTUATOR D564012
PARKER 608200659 DOMNICK HUNTER EXHAUST CYLINDER KIT D561700
PARKER 608200659 DOMNICK HUNTER EXHAUST CYLINDER KIT D561699
PARKER 608200659 DOMNICK HUNTER EXHAUST CYLINDER KIT D561697
FISHER 481-16 DVC6020 SIZE 40 ACTUATOR POSITIONER ASSEMBLY D565918
FISHER 481-16 SIZE 40 ACTUATOR POSITIONER ASSEMBLY D565917
FISHER 481-16 DVC6010 SIZE 40 ACTUATOR POSITIONER ASSEMBLY D565916
JOHNSON CONTROLS VA4233-GGA-2 1/2IN LINEAR PROPORTIONAL ACTUATOR D582117
JOHN CRANE 670AHT-SCX000-32 MECHANICAL PUMP SEAL KIT D580056
SPORLAN MVE-26-GA THERMOSTATIC EXPANSION VALVE D583021
GOULDS 70424 1618 BRONZE PUMP WEAR PLATE 3405M D586395
MASONEILAN DRESSER 7411-802 VALVE POSITIONER D583342
STAINLESS PUMP CASING 82629 1IN X 1-1/2IN NPT D581705
EMERSON XL0071U-S80-SCW-Y00 HYTORK X71 PNEUMATIC ACTUATOR 116PSI D585151
LAMIFLEX BRONZE LABYRINTH RING PUMP SEAL 150/190X22 D580255
FISHER 2U856346052 STAINLESS 1IN SEAT RING D581453
ABZ DA100 DOUBLE ACTING PNEUMATIC VALVE ACTUATOR D579674
TUTHILL 086800-OKIT PUMP REPAIR KIT FOR SDV-800 D595090
GOULDS 3405M 70423 1618 5X8-12IN BRONZE PUMP WEAR RING D596249
FLOWSERVE A10708-05 STUFFING BOX ASSEMBLY D596439
GOULDS 59016 IRON CENTRIFUGAL PUMP CASING 2-1/2 X 3IN NPT D596816
EL-O-MATIC ED0200.U2A00A.22K0 PNEUMATIC VALVE ACTUATOR D596947
EL-O-MATIC EL-55 ELECTRIC VALVE ACTUATOR 120V-AC D596915
GRUNDFOS 00345122 CR30/60 AUUE/V B PUMP SEAL KIT D597126
VON RUDEN 41970 OHLA OVERHUNG LOAD ADAPTOR 2 BOLT D597421
MILTON ROY PD017511432T0300 STAINLESS PULSATION DAMPENER 2IN NPT D597901
PLAST-O-MATIC GX300EP-PV PVC SINGLE WALL SIGHT FLOW GLASS 3IN D597878
MASONEILAN DRESSER 7411-712 VALVE POSITIONER D598904
DRESSER-RAND K7299-1 REPAIR KIT D599274
CHESTERTON S10 182633 STAINLESS CASSETTE TYPE CARTRIDGE SEAL 1.750IN D599638
MOORE 74G PNEUMATIC VALVE POSITIONER D599998
UNITORQ M237K55 PNEUMATIC VALVE ACTUATOR 150PSI D600201
CCI 731601001 BYPASS VALVE UPDATE REPAIR KIT D599630
1B096 BRASS PUMP IMPELLER 6-VANE 11IN OD 2-3/16IN BORE D591037
INGERSOLL RAND 6EH159B 2-1/4 IN SHAFT PUMP POWER END D546313
ROSEMOUNT 01 SMART RETROFIT KIT D561561
VIKING 3-574-001-100 1-15/16IN OD 27IN LENGTH PUMP SHAFT/ROTOR D568082
ROTEX ECV250E 125PSI PNEUMATIC VALVE ACTUATOR D568266
TUCHENHAGEN STAINLESS ACTUATOR W/ VALVE STEM D568867
STAINLESS PUMP IMPELLER 3543-99 B3653 1-3/8IN BORE 11-7/8IN OD D569086
STAINLESS PUMP IMPELLER 9593 1-1/4IN BORE 6-VANE 7-1/4IN OD D569088
TSI 1027 STAINLESS PUMP IMPELLER 1-1/4IN BORE 4-VANE 8IN OD D569089
ARCA REGLER 824 ELECTRO-PNEUMATIC VALVE POSITIONER D569593
SKF ASK 114 BEARING REMOVAL SLEEVE D542889
AUMA SAH7.1 1/2HP 460V-AC 1A 3360RPM ELECTRIC VALVE ACTUATOR D535643
LABOUR SIZE 12 TYPE SZ PUMP POWER END D522762
INGERSOLL RAND 637303-GG ARO DIAPHRAGM PUMP SERVICE KIT D559530
BALDOR 135136 AV05140774 DODGE 1012 TRAPEZODIAL OIL RING D541638
BALDOR 435010 AV06131484 DODGE SLEEVOIL 10 SLV RTL SEAL KIT D541727
FISHER 13B8790X012 03311-0298-0008 MULTIRANGE DIRECT MODULE ASSEMBLY D542067
APV 03H-P-478537 PUMP ROTOR D594542
DUFF NORTON M5804-253B ANTI-BACKLASH IRON VALVE ACTUATOR D594899
SPENCER TURBINE FNA103446.P 17-1/2IN ALUMINUM BLOWER IMPELLER D586589
PULSAFEEDER E12XBE-STD ECLIPSE KOPKIT D587382
PULSAFEEDER E12XBE ECLIPSE SERIES KOPKIT D586682
TRI CLOVER 761TR-10W-29S-2-316L-12-1 ALFA LAVAL STAINLESS ACTUATOR D593114
STONEL QZP2SC2R QUARTZ VALVEPOINT VALVE POSITION SENSOR 24-125V-AC D589621
CURTISS-WRIGHT 40771F PUMP RETAINING RING 6IN ID D595960
PLAST-O-MATIC GX300EP-PV 3IN PVC SINGLE WALL SIGHT FLOW GLASS D598207
6 VANE 16-1/8 IN OD 3-1/2 IN ID STEEL PUMP IMPELLER D525126
NELES JAMESBURY NP723/S1 PNEUMATIC VALVE POSITIONER D569048
GORMAN RUPP 46512-048 PUMP SEAL ASSEMBLY D577119
DURCO MY36862A100-D20 STAINLESS 5-VANE PUMP IMPELLER 8-3/4IN OD D561739
ROTORK K3 K-TORK PNEUMATIC ROTARY VANE ACTUATOR D563036
CHESTERTON 678351 442 GEMINI SPLIT SEAL SPARE KIT SIZE-15 1.875IN D594293
AESSEAL 3201243J P-150 BSTS STAINLESS BELLOWS PUMP SEAL 1-3/4IN D594295
