Introduction; General; Liquid Sample Path - Michell Instruments Liquidew EExd User Manual

Liquidew EExd User's Manual
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INTRODUCTION

1.1

General

The Liquidew EExd is designed for continuous, automatic measurement of the moisture
content in hydrocarbon solutes, utilizing the Michell Ceramic Moisture Sensor. It is the
result of more than 30 years' experience in the supply of analyzers to the worldwide oil,
gas and petrochemical industry.
The analyzer comprises either a single or a dual channel moisture measurement sensor
cell, control electronics and a display interface housed in an Exd enclosure. The analyzer
is ATEX Directive, IECEx or cCSAus compliant for use in a Zone 1 or 2 Hazardous Area
and Class I, Div 1 Hazardous Location. See marking label located on right hand side of
analyzer to identify approvals. An accompanying sample handling panel, designed to be
positioned close to the process sample point to prepare the sample prior to entry into
the Liquidew EExd, can also be supplied.
The instrument offers several user-selectable display options based on a calibrated
dew-point measurement range of -100 to +20°C (-148 to +68°F), traceable to the
humidity metrology standards of NPL (UK) and NIST (USA). The instrument provides
indication in moisture in liquids (ppm
The requirements for operation are a 90 to 260 V AC, 47/63 Hz power supply of 180W
and field communications Modbus RTU and/or 4-20 mA. Refer to the System Wiring
Diagram in Appendix B.3.
1.2

Liquid Sample Path

The Liquidew EExd analyzer system must be supplied with a liquid sample at a pressure
up to 80 barg (1160 psig), via a sample handling panel providing filtration & flow
control. Sufficient differential pressure will be required (typically greater than 0.5 barg
(7.2 psig)) between the process sample source and return points. This should enable a
flow between 0.1 and 0.3 l/min (0.03 and 0.08 GPM) through the Liquidew EExd and its
associated sampling system. Sample entry and exit ports direct the liquid through flame
arrestors which, along with the Exd enclosure, provide the explosion proof protection.
The measurement system components are housed within a cast aluminum Exd rated
enclosure. The enclosure has a screw cover incorporating a sealed window. It is
chromate primed, polyester coated in black, and provides environmental protection to
IP66/NEMA 4. An enclosure breather is fitted in the form of an additional flame arrestor.
It is important that no pipe connection is made to this breather and that no restriction
is allowed to occur.
For accuracy and long term reliability, the temperature of the sample entering the
Liquidew EExd should be less than +40°C (+104°F) and higher than +10°C (+50°F).
The sample and operating temperature must not exceed the T ambient rating of +60°C
(+140°F).
All sample wetted metallic parts are manufactured in AISI 316L stainless steel with
Viton soft parts that comply with the NACE standard MR-01-75 (latest edition). Tube
fittings are twin ferrule compression type. All electrical and liquid connections are made
through the base of the enclosure. Refer to the Mounting Drawing in Appendix A.1.
Flow components for Channels 1 & 2 comprise the following:
Flow Meter:
Measurement Cell:
Michell Instruments
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W
Provides indication of low, OK or high flow that is present
throughout the sample measurement stream.
The point of measurement that incorporates the Michell Ceramic
Moisture Sensor.
INTRODUCTION
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