Michell Instruments Pura 2-Wire User manual

Pura
Trace Moisture
2-Wire / 3-Wire / Digital Transmitter
User’s Manual
97070 Issue 12.1
March 2016
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Please fill out the form(s) below for each instrument that has been purchased.
Use this information when contacting Michell Instruments for service purposes.
Transmitter
Code
Serial Number
Invoice Date
Location of Instrument
Tag No
Transmitter
Code
Serial Number
Invoice Date
Location of Instrument
Tag No
Transmitter
Code
Serial Number
Invoice Date
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Tag No

© 2016 Michell Instruments
This document is the property of Michell Instruments Ltd. and may not be copied or
otherwise reproduced, communicated in any way to third parties, nor stored in any Data
Processing System without the express written authorization of Michell Instruments Ltd.
Pura 2-Wire / 3-Wire / Digital Transmitter
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For Michell Instruments' contact information please go to
www.michell.com

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
iv 97070 Issue 12.1, March 2016
Contents
Safety ................................................................................................................................vi
Electrical Safety ...........................................................................................................vi
UL Approval.................................................................................................................vi
Pressure Safety............................................................................................................vi
Toxic Materials .............................................................................................................vi
Repair and Maintenance ...............................................................................................vi
Calibration...................................................................................................................vi
Safety Conformity ........................................................................................................vi
Abbreviations..................................................................................................................... vii
Warnings ...........................................................................................................................vii
1 INTRODUCTION ................................................................................................1
1.1 Features ............................................................................................................ 1
2 INSTALLATION ..................................................................................................2
2.1 Unpacking the Instrument................................................................................... 2
2.2 Unpacking the Pura SEN ..................................................................................... 3
2.2.1 Unpacking Pura OEM-single bag, PREMIUM (PRM)-double bag versions ............ 3
2.3 Pura SEN ........................................................................................................... 4
2.4 Pura OEM, PRM.................................................................................................. 4
2.5 Preparation of the Transmitter Cable .................................................................... 5
2.6 Transmitter Mounting.......................................................................................... 6
2.6.1 Pura SEN - Sample Block (Optional) .............................................................. 6
2.6.2 Pura OEM & PRM Connection ......................................................................... 8
2.6.3 Pura SEN - Direct Pipeline Connection............................................................. 9
2.6.4 Transmitter Cable Connection....................................................................... 10
3 OPERATION ....................................................................................................11
4 MAINTENANCE ................................................................................................12
5 FAULT CONDITIONS ........................................................................................13

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
Michell Instruments v
Figures
Figure 1 Transmitter Unpacking Method ....................................................................3
Figure 2 Unpacking - Pura OEM & PREMIUM (PRM) - Single / Double Bag ...................3
Figure 3 Pura SEN ...................................................................................................4
Figure 4 Pura OEM, PRM..........................................................................................4
Figure 5 Connector Terminal Block Removal ..............................................................5
Figure 6 Rear of Connector Terminal Block - 2-wire....................................................5
Figure 7 Electrical Connections - 2-wire.....................................................................5
Figure 8 Rear of Connector Terminal Block - 3-wire....................................................6
Figure 9 Rear of Connector Terminal Block - 4-wire....................................................6
Figure 10 Sensor Block Connection.............................................................................7
Figure 11 Inlet/Outlet Identification............................................................................8
Figure 12 Transmitter Mounting - Pipe or Duct.............................................................9
Figure 13 Connector Installation...............................................................................10
Figure 14 Installation Location .................................................................................11
Figure 15 Indication of Dead Space ..........................................................................11
Figure 16 SEN Dimensional Drawing .........................................................................16
Figure 17 OEM & PRM Dimensional Drawing..............................................................16
Appendices
Appendix A Technical Specifications..............................................................................15
A.1 Dimensional Drawings..................................................................16
Appendix B EU Declaration of Conformity......................................................................18
Appendix C Quality, Recycling & Warranty Information...................................................20
C.1 Pressure Equipment Directive (PED) 97/23/EC ...............................20
C.2 Recycling Policy ..........................................................................20
C.3 WEEE Compliance........................................................................20
C.4 RoHS2 Compliance ......................................................................21
C.5 Warranty.....................................................................................21
C.6 REACH Compliance ......................................................................22
C.7 Calibration Facilities .....................................................................22
C.8 Return Policy ...............................................................................23
C.9 Manufacturing Quality..................................................................23
Appendix D Return Document & Decontamination Declaration........................................25

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
vi 97070 Issue 12.1, March 2016
Safety
The manufacturer has designed this equipment to be safe when operated using the procedures
detailed in this manual. The user must not use this equipment for any other purpose than that
stated. Do not apply values greater than the maximum value stated.
This manual contains operating and safety instructions, which must be followed to ensure the safe
operation and to maintain the equipment in a safe condition. The safety instructions are either
warnings or cautions issued to protect the user and the equipment from injury or damage. Use
competent personnel using good engineering practice for all procedures in this Manual.
Electrical Safety
The instrument is designed to be completely safe when used with options and accessories supplied
by the manufacturer for use with the instrument.
UL Approval (2-wire version ONLY)
This product (2-wire version only) is UL approved within the operating temperature range of -20°C
to +60°C. The IP66 rating of this product is outside the scope of UL Approval, but this product has
been verified as being IP66 by independent, UKAS accredited, 3rd party listing.
Pressure Safety
DO NOT permit pressures greater than the safe working pressure to be applied to the instrument.
The specified safe working pressure is 24 MPa (240 barg / 3480 psig). Refer to Appendix A,
Technical Specifications.
Toxic Materials
The use of hazardous materials in the construction of this instrument has been minimized. During
normal operation, it is not possible for the user to come into contact with any hazardous substance,
which might be employed in the construction of the instrument. Care should, however, be exercised
during maintenance and the disposal of certain parts.
Repair and Maintenance
The instrument must be maintained either by the manufacturer or an accredited service agent. For
Michell Instruments’ contact information please go to www.michell.com.
Calibration
Periodic re-calibration is recommended in order to maintain the highest quality of measurement in
your application. Michell Instruments recommends that you have your Pura transmitter re-calibrated
annually unless it is used in a mission-critical application or in a contaminated environment, in which
case the calibration interval should be reduced accordingly.
Michell Instruments can offer a variety of re-calibration and exchange transmitter schemes to suit
your specific needs. Your local representative will be pleased to provide detailed, custom advice.
Safety Conformity
This product meets the essential protection requirements of the relevant EU directives. Further
details of applied standards may be found in the Technical Specifications, Appendix A.

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
Michell Instruments vii
Abbreviations
The following abbreviations are used in this manual:
barg bar gauge
°C degrees Celsius
°F degrees Fahrenheit
dp dew point
DC direct current
fps feet per second
μm micro-meter
Nl/min normal liters per minute
mA milliampere
Mpa megapascal
m/sec meters per second
Nm Newton meter
psig pounds per square inch
ppmVparts per million by volume
RH relative humidity
scfh standard cubic feet per hour
V volts
Ωohms
Warnings
The following general warning listed below is applicable to this instrument. It is repeated
in the text in the appropriate locations.
Where this hazard warning symbol appears in the following
sections it is used to indicate areas where potentially
hazardous operations need to be carried out.

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
Michell Instruments 1
INTRODUCTION
1 INTRODUCTION
The Pura Series of transmitters has been manufactured, tested and calibrated to
the highest available standards and should arrive in perfect working order, ready for
installation into a gas measurement application.
If there are any questions about the transmitter or how to install it, not detailed in
this Manual, contact your local representative. Refer to www.michell.com for details of
Michell Instruments’ worldwide offices’ contact information.
1.1 Features
The Pura Series are a continuous, on-line, 4-20 mA/digital transmitter family for the
measurement of moisture content in air and other non-corrosive gases.
Their key features are:
• Accuracy ±1°C dp
• 0.5°Cdp (0.9°Fdp) repeatability
• 2-wire connection - linear 4–20 mA signal
• 3-wire connection - linear 4-20 mA signal
• Digital transmitter - 4-wire connection - digital string signal (NOTE: only
works with the Pura AOL monitor)
• Operating pressure range - up to 24 MPa (240 barg / 3480 psig)
• Operating range - 120 to -40°Cdp (-184 to -40°Fdp)
• Moisture content ppmV (2-wire)
• Powered by any DC source from 12 to 28 V

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
297070 Issue 12.1, March 2016
INSTALLATION
2 INSTALLATION
2.1 Unpacking the Instrument
On delivery, check that all the following standard components are present in the packing
box:
Pura SEN (transmitter, no block version)
2-wire 3-wire Digital Transmitter
Calibration Certificate 
Transmitter Connector 
Connector Gasket 
Round

Square

Square
97070 User’s Manual 
Leak Test Certificate 
VCR Seal
(for sample block) 
Pura OEM / Pura PREMIUM (PRM)
2-wire 3-wire Digital Transmitter
Calibration Certificate 
Transmitter Connector 
Already Fitted

Already Fitted

Already Fitted
Connector Gasket 
Round

Square

Square
97070 User’s Manual 
Leak Test Certificate 
NOTE: If any component is not present in the packing box, contact Michell
Instruments immediately.
NOTE: Packing tube and foam protectors are not needed for operation. Save
all the packing materials for the purpose of returning the instrument for re-
calibration or any warranty claims.

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
Michell Instruments 3
INSTALLATION
2.2 Unpacking the Pura SEN
Unpack the dew-point transmitter packing tube as follows (see Figure 1).
87645321
Figure 1
Transmitter Unpacking Method
1. Unscrew the cap (1) from the packing tube (8).
2. Remove the foam block (3) containing the connector (2).
3. Pull out the transmitter (5) from the tube, complete with the two foam
covers (6) and (7), the red protective cap (4) and the connector gasket
(3-wire or digital sensor only).
4. Remove the foam covers from the transmitter but leave the red plastic
protective cover (5), the red cap (4) and the connector gasket in place
until ready for installation.
NOTE: The transmitter sensing element is protected while in transit by a red
cover containing a small desiccant capsule. The connection pins are protected
by a red plastic cap. None of these plastic items are required for the operation
of the transmitter.
NOTE: Keep the connector (2) in a safe place until the transmitter is ready
for wiring.
2.2.1 Unpacking Pura OEM-single bag, PREMIUM (PRM)-double bag versions
Figure 2 Unpacking - Pura OEM & PREMIUM (PRM) - Single / Double Bag

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
497070 Issue 12.1, March 2016
INSTALLATION
2.3 Pura SEN
NOTE: For environmental and operating conditions, refer to Appendix A,
Technical Specifications.
Electrical connector
Transmitter cover
Transmitter label
Hexagonal nut
Process connection (½”VCR)
Sensing element
Figure 3 Pura SEN
2.4 Pura OEM, PRM
NOTE: For environmental and operating conditions refer to Appendix A,
Technical Specifications.
NOTE: The OEM and PRM transmitters are protected in transit by putting in a
plastic bag filled with nitrogen. The Pura OEM has single bag protection and
the Pura PRM has double bag protection.
Electrical connector
Transmitter cover
Transmitter label
Sensor block
Gas inlet (¼” VCR)
(see note below) Gas outlet
(¼” VCR)
NOTE: The Pura has a uni-directional connection and must be
connected so the upstream flow is connected to the inlet port
of the Pura block (marked with a silver label).
INLET
Figure 4 Pura OEM, PRM

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
Michell Instruments 5
INSTALLATION
2.5 Preparation of the Transmitter Cable
The transmitter cable is NOT supplied as standard. A cable can be obtained by contacting
your local distributor or Michell Instruments (see www.michell.com for details).
Cable connection to the Pura transmitter is made via the removable connector. Removing
the central screw enables the connector terminal block to be removed from the outer
housing by using a small screwdriver to prise it clear.
i
O-ring
and washer
Figure 5 Connector Terminal Block Removal
Caution: When removing the central screw ensure that the
small sealing O-ring and the washer are retained on the screw
and are present during re-installation.
For the transmitter to work properly, and to achieve maximum performance, the
transmitter cable must be connected to the transmitter connector as shown in the
drawings below:
2-wire
h
h
Supply
4-20 mA
PIN 3
PIN 1
(GND) Screen/Shield
Optional
Figure 6 Rear of Connector Terminal Block - 2-wire
Always connect the 4-20 mA return signal to a suitable load
before the power is applied. Without this connection the sensor
may be damaged if allowed to operate for prolonged periods.
3
1
Max Load
250R @ 12V
500R @ 24V
Supply
12V Min
28V Max
+
Figure 7 Electrical Connections - 2-wire

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
697070 Issue 12.1, March 2016
INSTALLATION
3-wire
4-20 mA (Source)
PIN 3
PIN 1
(GND)
GROUND (System 0 V)
and Cable Screen
Power (+12 V to +24 V)
Figure 8 Rear of Connector Terminal Block - 3-wire
4-wire Digital String
NOTE: Digital String will only work with Pura AOL Monitor
YELLOW
GREEN
BLUE
RED
PIN 3
PIN 2
RED
+Power YELLOW
Signal (A)
GREEN
Signal (B)
PIN 1
BLUE
Ground 1
2
3
4YELLOW Signal (A)
GREEN Signal (B)
BLUE Screen
RED +Power
Figure 9 Rear of Connector Terminal Block - 4-wire
2.6 Transmitter Mounting
2.6.1 Pura SEN - Sample Block (Optional)
Prior to installation of the transmitter, unscrew and remove the red plastic cover and
HDPE guard and retain for future use. Take care to prevent any contamination of the
transmitter before installation - handle the transmitter by the main body only,
avoiding contact with the sensor guard.
The recommended gas flow rate, when mounted in the optional sampling block, is 1 to
5 Nl/min (2.1 to 10.6 scfh). However, for direct insertion applications, gas flow should
be from static to 10 m/sec (32.8 fps).

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
Michell Instruments 7
INSTALLATION
The following procedure must be carried out by a qualified
installation engineer.
To mount the transmitter into the sensor block (preferred method), proceed as follows
(see Figure 10) :
1. Remove the red protective cover (2) from the tip of the transmitter
(1).
2. Fit the ½” VCR gasket (3) over the threaded part of the transmitter
body.
WARNING: Under no circumstances should the filter guard be
handled with the fingers.
3. Screw the transmitter (1) into the sensor block (4) and, holding
the Pura transmitter stationary with a spanner/wrench, tighten the
gas line nut 1/8 of a turn using a second spanner/wrench. NOTE:
Use the flats of the hexagonal nut and not the transmitter
body.
4. Fit the transmitter cable/connector assembly to the plug located
on the base of the transmitter and tighten the fixing screw (see
Figure 5).
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Figure 10
Sensor Block Connection

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
897070 Issue 12.1, March 2016
INSTALLATION
2.6.2 Pura OEM & PRM Connection
The Pura OEM and PRM have been assembled and packaged within a Class 100 clean-
room environment. To maintain this level of cleanliness the packaging should only be
opened within the same, or cleaner, environment.
Michell Instruments recommends the use of Swagelok®retained gasket assemblies,
containing silver plated, stainless steel ¼” VCR gaskets, when connecting the Pura into
a gas line. The distance between the inlet and outlet gas connection ports is set at a
pitch of 120mm (4.7”).
1. Install the sealing gasket onto the VCR connections on either the
Pura or the connecting gas lines. Ensure that the Pura is offered
into the gas line with reference to the gas flow direction and the
inlet port, as indicated on the Pura body.
Inlet Outlet
Figure 11 Inlet/Outlet Identification
NOTE: In order to identify the Inlet and Outlet without
dismantling the instrument it is necessary to look through the
Inlet/Outlet holes. Looking through the INLET hole a shiny end
can be seen, looking through the OUTLET hole an elongated
shape can be seen.
2. Tighten the female nut firmly, finger tight.
3. Hold the Pura transmitter stationary with a spanner/wrench and
tighten the gas line nut 1/8 of a turn using a second spanner/
wrench.
4. Repeat this operation on the remaining gas connection port.
CAUTION: Over-tightening the nuts can cause irrecoverable
damage to the seals and seatings.

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
Michell Instruments 9
INSTALLATION
2.6.3 Pura SEN - Direct Pipeline Connection
The transmitter may be directly mounted into a pipe or duct .
CAUTION: Do not mount the transmitter too close to the
bottom of a bend where any condensate in the pipeline might
collect and saturate the probe.
The pipe or duct will require a ½” VCR male process connection thread to match
the transmitter body thread. Fixing dimensions are shown in Figure 12. For circular
pipework, to ensure the integrity of a gas tight seal, a mounting flange will be required
on the pipework in order to provide a flat surface to seal against.
Procedure
The following procedure must be carried out by competent
personnel.
1. Ensure that the red protective cover has been removed from the
tip of the transmitter.
WARNING: Under no circumstances should the filter guard be
handled with the fingers.
2. After first checking that the pipeline has a wide enough bore to
accept the transmitter’s process connection, screw the transmitter
into the pipe. Tighten enough to obtain a gas tight seal. (Torque
will depend upon the pipeline material.)
Michell Instruments recommends the use of Swagelok®retained gasket assemblies,
containing silver plated, stainless steel ½” VCR gaskets, when connecting the Pura into
a gas line.
NOTE: Do not overtighten or the thread on the pipework may be stripped.
(1.9”)
1
1
2
2
3
3
Optional
display
(available
on request)
Optional
cable
(available
on request)
j
j
48mm
Figure 12 Transmitter Mounting - Pipe or Duct

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
10 97070 Issue 12.1, March 2016
INSTALLATION
2.6.4 Transmitter Cable Connection
When installing the connector, and to ensure that full ingress protection is achieved, the
securing screw (with the O-ring and washer) must be tightened to a minimum torque
setting of 3.4 Nm (2.5 ft-lbs). The transmitter cable used must be a minimum diameter
of 4.6mm (0.2”).
4
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and washer
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2
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Figure 13 Connector Installation

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
Michell Instruments 11
OPERATION
3 OPERATION
Operation is very simple assuming the following installation techniques are adhered to:
Sampling Hints
Be Sure the Sample is Representative of the Gas Under Test:
The sample point should be as close to the critical measurement point as possible. Also,
never sample from the bottom of a pipe as entrained liquids may be drawn into the
sensing element.


Figure 14 Installation Location
Minimize Dead Space in Sample Lines:
Dead space causes moisture entrapment points, increased system response times, and
measurement errors as a result of the trapped moisture being released into the passing
sample gas and causing an increase in partial vapor pressure.
Deadspace

Figure 15 Indication of Dead Space
Remove Any Particulate Matter or Oil from the Gas Sample:
Particulate matter at high velocity can damage the sensing element and similarly, at
low velocity, they may ‘blind’ the sensing element and reduce its response speed. If
particulate, such as degraded desiccant, pipe scale or rust is present in the sample gas,
use an in-line filter, as a minimum level of protection. For more demanding applications
Michell Instruments offers a range of sampling systems (for more information contact
www.michell.com).
Use High Quality Sample Tube and Fittings:
Michell Instruments recommends that, wherever possible, stainless steel tubing and
fittings should be used. This is particularly important at low dew points since other
materials have hygroscopic characteristics and adsorb moisture on the tube walls,
slowing down response and, in extreme circumstances, giving false readings. For
temporary applications, or where stainless steel tubing is not practical, use high quality
thick walled PTFE tubing.
Position Transmitter away from Heat Source:
It is recommended, as good instrumentation practice, that the transmitter is placed
away from any heat source to avoid adsorption/desorption.

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
12 97070 Issue 12.1, March 2016
MAINTENANCE
4 MAINTENANCE
Calibration
Routine maintenance of the Pura is confined to regular re-calibration by exposure of
the Pura to sample gases of known moisture content to ensure that the stated accuracy
of the Pura is maintained. Calibration services traceable to the UK
National Physical
Laboratory (NPL) and the US National Institute of Standards and Technology (NIST) are
provided by Michell Instruments.
Michell Instruments offers a re-calibration service to suit specific needs. A Michell
representative can provide detailed, custom advice (for Michell Instruments’ contact
information go to www.michell.com).

Pura 2-Wire/3-Wire/Digital Transmitter
User’s Manual
Michell Instruments 13
FAULT CONDITIONS
5 FAULT CONDITIONS
2-wire & 3-wire 4-20 mA Output Only
Message
Displayed Cause Action
Current output is
0 mA constantly Power failure
Check power supply to transmitter
Check transmitter cable for
continuity/damage
Rectify/replace cable
Instrument failure Contact instrument supplier
Current output is
4 mA constantly
Transmitter desiccated Check gas source supply
Transmitter contaminated Replace/re-calibrate transmitter
Current output is
20 mA constantly
Gas is wetter than -40°Cdp
(-40°Fdp) Check gas source supply
Transmitter contaminated Replace/re-calibrate transmitter
Current output is
23 mA constantly Instrument failure Contact instrument supplier
Digital String - See Pura AOL Manual