Introduction; General; Sample Gas Path - Michell Instruments Promet EExd User Manual

Promet EExd User's Manual
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INTRODUCTION

1.1

General

The Promet EExd is designed for continuous, automatic measurement of the moisture
content of processed natural gas, 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 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 Promet 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 further
provides indication only in the ranges of +20 to +30°Cdp (+68 to +86°Fdp) and -100 to
-120°Cdp (-148 to -184°F), equating to a moisture measurement capability of <1ppb
to >30,000 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 A.
1.2

Sample Gas Path

The Promet EExd analyzer system must be supplied with gas at the required pressure,
via a sample gas handling panel providing suitable pressure, filtration & flow control.
Sample gas entry and exit ports direct the gas through flame arrestors which, along with
the Exd enclosure, provide the explosion proof protection. 1 or 2 separate measurement
channels can be accommodated within the instrument.
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.
All sample gas-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 gas connections are made
through the base of the enclosure. Refer to the Mounting Drawing in Appendix A.
Channel 1 flow components comprise the following:
(Optional) Flow Switch 1 (FS1):
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is present throughout the moisture measurement stream
Pressure Transducer 1 (PT1):
•
the sample gas pressure within the moisture measurement cell
Michell Instruments
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Provides indication that a flow
Provides the measurement of
INTRODUCTION
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