Michell Instruments PSD2, PSD4 Operating Manual
PSD2
Pressure Swing Dryer
User’s Manual
97031 Issue 13.1
September 2018
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PSD2
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© 2018 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.
PSD2 User’s Manual
Contents
Safety ................................................................................................................................ v
Electrical Safety ........................................................................................................... v
Pressure Safety ............................................................................................................ v
Toxic Materials ............................................................................................................. v
Repair and Maintenance ............................................................................................... v
Safety Conformity ........................................................................................................ v
Abbreviations ......................................................................................................................vi
Warnings ............................................................................................................................vi
1 INTRODUCTION ................................................................................................1
1.1 Overview ........................................................................................................... 1
1.2 Operating Principle .............................................................................................1
2 INSTALLATION ..................................................................................................2
2.1 Installing the Dryer ............................................................................................. 2
2.2 Electrical Connections .........................................................................................2
2.3 Gas Connections ................................................................................................. 2
3 OPERATION ......................................................................................................3
3.1 Operating the Dryer ............................................................................................ 3
4 MAINTENANCE ..................................................................................................4
4.1 Maintaining the Dryer ........................................................................................4
4.1.1 Desiccant Change .........................................................................................4
4.1.2 Adjusting the Purge Flow ............................................................................... 6
4.2 Fault Diagnosis ................................................................................................... 8
4.2.2 Flow, Pressure and Timing Calibration ............................................................8
Figures
Figure 1 System Layout Drawing ............................................................................13
Figure 2 Schematic Flow Drawing ...........................................................................14
Appendices
Appendix A Technical Specifi cations ..............................................................................11
Appendix B System Drawings .......................................................................................13
B.1 System Layout Drawing ................................................................13
B.2 Schematic Flow Drawing ..............................................................14
Appendix C Quality, Recycling, Compliance & Warranty Information ................................16
Appendix D Return Document & Decontamination Declaration ........................................18
iv 97031 Issue 13, July 2018
PSD2 User’s Manual
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.
Pressure Safety
DO NOT permit pressures greater than the safe working pressure to be applied to the instrument.
The specifi ed safe working pressure is 5 to 7 barg (70 to 100 psig).
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. Refer
to www.michell.com for details of Michell Instruments’ worldwide offi ces contact information.
Safety Conformity
This product meets the essential protection requirements of the relevant EU directives. Further
details of applied standards may be found in the product specifi cation.
Michell Instruments v
Abbreviations
The following abbreviations are used in this manual:
AC alternating current
atm pressure unit (atmosphere)
bar pressure unit (=100 kP or 0.987 atm)
°C degrees Celsius
°F degrees Fahrenheit
dp dew point
kg kilogram
Hz Hertz
lb pound
l/min liters per minute
max maximum
mm millimeter
ppm
parts per million (by volume)
V
ppb
parts per billion (by volume)
V
scfh standard cubic feet per hour
V Volts
" inch(es)
% percentage
PSD2 User’s Manual
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.
vi 97031 Issue 13, July 2018
PSD2 User’s Manual
1 INTRODUCTION
1.1 Overview
The Michell PSD2 is a Pressure Swing Dryer in a compact rack mounting unit designed
to remove moisture from compressed air down to trace levels of less than 1 part per
million by volume.
The dryer operates by pressure swing regeneration of a desiccant column. Design is
such that, with 2 columns operating in rotation, a constant fl ow of very dry air (or other
inert gas) can be produced for long periods without maintenance.
Heat is not supplied to the desiccant making the unit energy effi cient and extremely
reliable with the typical lifetime of the desiccant being 5 years.
1.2 Operating Principle
INTRODUCTION
The supply pressure is regulated by PR1, and indicated by either gauge PG1 or PG2,
depending which column is active at that moment in time.
The gas then passes through the solenoid valves (SV1 & SV2), which direct it to the
appropriate desiccant column (DC1 or DC2).
The desiccant columns are fi lled with 4 Ångström molecular sieve. The column capacity
is designed so that, as the molecular sieve absorbs water from the gas, the moisture
content at the outlet of the cylinder is reduced to <1ppmV. This output is achievable
regardless of the moisture content of the gas source. the only stipulation is that it must
not contain liquid water.
The dried gas then passes through the non-return valve (NRV1) before reaching the
outlet port.
The life expectancy of the molecular sieve is preserved by continual regeneration of the
active column (purging of accumulated moisture). At the beginning of the regeneration
cycle the bulk of the moisture is removed by rapidly reducing the pressure in the
column, which desorbs moisture from the molecular sieve surface. Following this, the
remainder of the moisture is removed by fl owing a small proportion of the dried gas
from the active column.
Once this cycle is complete, the system switches columns, and begins the cycle again.
This regeneration process operates on 10 minute cycles, to provide uninterrupted dry
gas output.
Michell Instruments 1
INSTALLATION
2 INSTALLATION
The PSD2 is supplied with a full accessory package. Please check that you have received
all the items listed on the Packing Check List.
The factory set power supply voltage is indicated on the yellow label located on the rear
panel of the unit. The power supply voltage setting cannot be changed by the user as
this involves replacing internal electro-mechanical parts. Contact Michell Instruments’
Customer Service Department (contact details at www.michell.com) if a change is
needed.
2.1 Installing the Dryer
The PSD2 requires an operating environment of 0 to +50°C (+32 to +122°F), 0 to 90%
RH. Refer to Appendix B for outline dimensions.
The PSD2 case is designed for 19” 6U rack mounting. However, it can be used as a
bench mounted device without any special preparation. When rack mounting, simply
screw the unit front panel to the front of the rack using 4 M6 X 15mm screws and plastic
inserts.
PSD2 User’s Manual
NOTE: A minimum depth behind the PSD2 front panel of 48cm (18.9”) is
required for the unit, pipes and wiring.
2.2 Electrical Connections
Either 220/240 V AC, 50Hz or 100/20 V AC, 60Hz power supply is required to operate
this instrument. Refer to the yellow label located on the rear panel of the unit for the
correct supply voltage required.
The power supply connection is via the 3-pin IEC plug located on the rear panel of
the unit. A 3-core power cable is provided, the free end of which should be wired to a
suitable earthed plug or directly via a fused power spur.
Power cable conductors are colored according to the convention:
Brown L (Live)
Blue N (Neutral)
Green/yellow E (Earth)
2.3 Gas Connections
Gas connections are made via tube fi ttings located on the rear panel of the unit marked
‘GAS INLET’ and ‘GAS OUTLET’.
The gas inlet connection is a Swagelok® stainless steel 6mm bulkhead union tube fi tting.
The gas outlet connection is a Swagelok® stainless steel 6mm bulkhead union face seal
(VCR) fi tting.
Ensure the supply inlet gas is of a suitable pressure - between 5.5 to 7 barg (80 to 100
psig), free of oil and at a dew point of typically <-40ºC (<-40ºF). If the supply inlet gas
does not meet this requirement it will reduce the dryer’s effi ciency and eventually lead
to complete failure.
NOTE: An oil free compressor or bulk inert gas source must be used.
2 97031 Issue 13, July 2018
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