Ion-science Hydrosteel 7000 User Manual download pdf (Page 14)

Hydrosteel 7000 MANUAL Ion Science Ltd

Page 14 of 43

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Hydrosteel 7000

Thermocouple

junction box

Thermocouple

SCREEN

0V BK

+V RD

SCREEN

+V RD

0V BK

Red Connector

Blue Connector

4-20mA 1

4-20mA 2

Electrical connections (IS) using galvanic isolator and alternative grounding

SCREEN

+V RD

0V BK

Yellow Connector

Power

Control equipment

SAFE AREA

IS Galvanic

Isolator

Screens no longer grounded

at the control equipment end

Capacitors and Power OV shorted

to ground stud inside HY7K

JB earth

Note: JB earth and HY7K earth must be

equi-potential and have no more than 1 Ohms

resistance between them

HY7K earth

Installation

Use of Galvanic isolator and alternative grounding

Galvanic isolators may be used instead of safety barriers in the above circuit. If an isolated supply is used,

the supply at the instrument should be checked for AC noise. Measure the AC voltage between the 0 V and

the local earth. If there is AC noise this needs to be removed. It might be due to a faulty power supply or

induction of AC onto the cables. To remove the noise it might be necessary to ground the 0 V to an earth

point either in the control equipment or at the HY7K instrument. For electrically noisy environments the

optimum grounding is shown in the wiring diagram below. It is essential to follow the following key rules:

1. Screens may only be grounded at one end.

2. If the Power supply 0 V is grounded at the Hydrosteel then a suitable rated Galvanic isolator must be

used.

Cable Requirements

To meet the EMC compliance for immunity it is required that power and 4-20 mA current loops are supplied

with screened twisted pairs. Pairs should be individually screened with the screens terminated in the safe

area and to the terminals on the Hydrosteel 7000. (Note the Hydrosteel does not allow DC earth loops to

ground down the screens).

Removal of cladding and insulation

Hydrosteel flux measurement requires intimate contact between the probe plate and test surface, so it is

necessary to remove any insulation from the target sites.

For ease of access during probe installation, cladding and insulation should be removed from a 1 ft distance

from the centre of the site for flux monitoring. Additionally, if the probe is to be fixed with banding (to pipes

and vessels of less than 32” diameter), insulation and cladding must be removed from the entire

circumference of the vessel or pipe under test.

Preparation of test site

The surface should be free from ridges such as weld filets which could prevent the collector plate from

making intimate contact with the steel surface.

The identified test site surface should be at least 4”, in diameter, to accommodate both the probe and

magnetic thermocouple assembly. This surface should be free from rust and flaking paint which might

otherwise prevent hydrogen flux from exiting the steel surface.

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