Installation Manual

ValveWatch II Hardware Installation and Setup Manual
Page 18 of 34
CRANE
Nuclear
5.1 Example Cable Length Calculations for Power
Connection
Cable lengths are critical for intrinsic safety. Before any installation is complete, an analysis of the
cable length for verification of intrinsic safety is required.
The Tables below are an example for verifying specific cable length requirements
Assumptions for the Example Cable Length Calculation Tables 3, 4 and 5
For our example, use Ex ia IIC
Table 1. Example entity parameters for the ValveWatch Sensor Modules
Apparatus
Classification
Uo (V) Co (uF) Lo (mH)
Ex ia IIC
Class I Group A,B
28 0.083 2.510
Ex ia IIB
Class I Group C
Class II Group E
28 0.650 7.350
Ex ia IIA
Class I Group D
Class II Group F,G
28 2.150 20.00
Table 2. Example entity parameters for the ValveWatch Communications
Module
Apparatus
Classification
Uo (V) Co (uF) Lo (mH)
Ex ia IIC
Class I Group A,B
23 0.200 1.000
Ex ia IIB
Class I Group C
Class II Group E
23 1.000 5.000
Ex ia IIA
Class I Group D
Class II Group F,G
23 Not specified Not specified
• Operation modes DOP or RF are indicated
• Communications module has a minimum operating voltage of 9 volts and a peak current
of 40 milliamps.
• The sensor modules have a minimum operating voltage of 9 volts and a peak current of
20 milliamps per module.
• Cable parameters used for 0.75mm
2
conductors are:
C
cable
= 90 nF/km or 90 pF/m
L
cable
= 0.75 mH/km or 0.75 uH/m
R
cable
= 24.8 Ω/km or 0.0248 Ω/m
• The input entity parameters of the module power terminals 13, 14,15 and 16 is zero (0)
for inductance and capacitance.
• The minimum supply voltage for sensor modules is 24 vdc.
• The minimum supply voltage for the communications module is 13.8 vdc.
• The resistance for the MTL 7728P+ barrier is 252 ohms.