Emerson Process Management Rosemount 2410 manual Grounding 3.4.5 Cable Selection for the Tankbus

Reference Manual

Rosemount 2410

300530EN, Rev BA September 2012

3.4.4Grounding

3.4.5Cable Selection for the Tankbus

The housing should always be grounded in accordance with national and local electrical codes. Failure to do so may impair the protection provided by the equipment. The most effective grounding method is direct connection to earth ground with minimal impedance. There are grounding screw connections inside the terminal compartments which are identified by ground

symbols: / . There is also a grounding screw on the housing.

NOTE!

Grounding the device via threaded conduit connection may not provide sufficient ground.

Grounding - Foundation Fieldbus

Signal wiring of the fieldbus segment (Tankbus) can not be grounded. Grounding one of the signal wires may shut down the entire fieldbus segment.

Shield Wire Ground

To protect the fieldbus segment (Tankbus) from noise, grounding techniques for shield wire usually require a single grounding point for shield wire to avoid creating a ground loop. The ground point is typically at the power supply.

The Raptor devices are designed for “daisy-chain” connection of shield wiring in order to enable a continuous shield throughout the Tankbus network.

Use shielded twisted pair wiring for the Rosemount 2410 Series in order to comply with FISCO(1) requirements and EMC regulations. The preferred cable is referred to as type “A” fieldbus cable. The cables must be suitable for the supply voltage and approved for use in hazardous areas, where applicable. In the U.S. explosion-proof conduits may be used in the vicinity of the vessel.

We recommend cable size 1.0 mm2 or 18 AWG in order to facilitate wiring. However, cables within the range 0.5 to 1.5 mm2 or 20 to 16 AWG can be used.

The FISCO FOUNDATION™ fieldbus specification requires that cables for the Tankbus comply with the following parameters:

Table 3-1. FISCO cable parameters

Parameter(1)	Value
Loop resistance	15 to 150 Ω/km
Loop inductance	0.4 to 1 mH/km
Capacitance	45 to 200 nF/km
Maximum length of each spur(2) cable	60 m in apparatus class IIC and IIB
Maximum length of each trunk(3) cable	1000 m in apparatus class IIC and 1900 m in
	apparatus class IIB

(1)For further information see requirements of the IEC 61158-2 standard, and safety requirements in IEC/TS 60079-27:2002.

(2)A spur is an unterminated part of the network.

(3)A trunk is the longest cable path between two devices on the fieldbus network, and is the part of the network which has terminations at both ends. In the Raptor system, a trunk is typically located between the 2410 Tank Hub and a splitter or the last device in a daisy-chain configuration.

(1)See IEC 61158-2 and IEC/TS 60079-27:2002.

3-6 Section 3. Installation