SPI Supplies SPI-DRY User manual

Rev. 2.2 April 2021
SPI-DRYTM
Critical Point
Dryer
Operation Manual
SPI Supplies Part #13200JE-AB

SPI Supplies 2 SPI-DRY Critical Point Dryer
Structure Probe, Inc. / SPI Supplies
Street address for UPS, FedEx, DHL, other couriers, trucks
206 Garfield Ave.
West Chester, PA 19380 ·
Mailing address P.O. Box 656 West Chester,
PA 19381-0656 USA
Phone: [phone]-SPI
Toll-free from USA/Canada 1-(610)-436-5400
FAX: [phone]
E-mail: [e-mail]
For further information regarding any of the other products designed and manufactured by SPI Supplies,
contact your local representative or directly to SPI Supplies at the address above.
Carbon and Sputter Coaters
Plasma Reactor for ashing and etching
High Vacuum Bench Top Evaporators
Critical Point Dryers
Electron Microscopy Consumables

SPI Supplies 3 SPI-DRY Critical Point Dryer
Warranty
The SPI Supplies unit you have purchased is guaranteed to be free of defects in workmanship on the
day of shipment. This warranty covers parts and labor for a period of one year, excluding shipping
charges or consumables. Breakage of glassware is specifically excluded from this warranty.
Proper use of your unit, according to the operation manual, should result in trouble-free operation. Any
improper use of the SPI Supplies unit through modifications or unreasonable operating procedures will
void this warranty.
Disclaimer
SPI Supplies instruments are designed for simplicity of installation and operation. This manual provides
full and complete information in both these areas. SPI Supplies therefore assumes no liability or
responsibility of any kind for damage or injury resulting from incorrect installation or operation of the
machine.

SPI Supplies 4 SPI-DRY Critical Point Dryer
1 Contents
1.1 Manual Layout
This Operation Manual is divided up into the following major section, each section dealing with specific
topics, as follows:
Section 1 - Contents
Section 2 - Health and Safety
General section which applies to all SPI Supplies products detailing the very important issues of
Health and Safety applicable when using sample preparation equipment.
Section 3 - Introduction
Introduces this manual.
Section 4 - General Description
Identifies each of the equipment items and provides an overview of their functions and how they
work.
Section 5 - Installation
Instructions on how this instrument should be installed and the connections which should be made
between the equipment items.
Section 6 - Operation
Instructions on how to start-up and run the instrument.
Section 7 - Maintenance
Instructions on routine maintenance checks ensure that the system is functioning correctly.
Information on how to identify faults in the system, and how to rectify these faults.
Section 8 –Troubleshooting
Spare parts and consumables

SPI Supplies 5 SPI-DRY Critical Point Dryer
1.2 Section Contents
Section 1 - Contents ................................................................................................4
1.1 Manual Layout ...............................................................................4
1.2 Section Contents ............................................................................5
1.3 Illustrations .....................................................................................7
1.4 Tables ............................................................................................7
Section 2 - Health and Safety ..................................................................................8
2.1 Safety Policy ..................................................................................8
2.2 Conformity ......................................................................................8
2.3 Servicing ........................................................................................8
2.3.1 Disclaimer ...............................................................................8
2.3.2 Operators and Service Engineers ..........................................8
2.4 Hazard Signals and Signs ..............................................................9
2.4.1 Hazard Signal Words .............................................................9
2.4.2 Hazard Labels used on Equipment ........................................9
2.4.3 Hazard Warning Labels used in Equipment Manuals ............9
2.4.4 Instrument Functionality Signs ...............................................10
2.4.5 Serious Damage to Instruments .............................................10
2.4.6 Hazard to Operator ................................................................10
2.5 Risk Analysis ..................................................................................11
2.5.1 Personal Operational Risks ....................................................11
2.5.2 Hazardous Materials ..............................................................11
2.6 Good Working Practices ................................................................12
2.7 Critical Point Dryer Specific Safety Hazards ..................................12
Section 3 - Introduction............................................................................................13
3.1 Return of Goods .............................................................................13
3.2 Returns Procedure .........................................................................13
Section 4 - Description ............................................................................................14
4.1 Equipment ......................................................................................14
4.1.1 Accessories ............................................................................14
4.2 Overview ........................................................................................15
4.3 Technical Specification ..................................................................15
4.3.1 SPI-DRY Critical Point Dryer Specifications ..........................15
4.4 Physical Description .......................................................................16
4.4.1 Chamber body.........................................................................16
4.4.2 Control Valves ........................................................................16
4.4.3 System Gauges.......................................................................17
4.4.4 Safety Valve ...........................................................................17
4.4.5 Specimen Holder ....................................................................17
4.4.6 Microporous Specimen Capsules ..........................................17

SPI Supplies 6 SPI-DRY Critical Point Dryer
Section 5 - Installation .............................................................................................18
5.1 Unpacking Checklist ......................................................................18
5.1.1 Site Selection .........................................................................18
5.2 Connection of Services ..................................................................19
5.2.2 Water ......................................................................................19
5.2.3 Carbon Dioxide (CO2) ............................................................19
5.2.4 Carbon Dioxide (CO2) Exhaust ..............................................19
Section 6 - Operation ...............................................................................................21
6.1 Critical Point Drying Method ..........................................................21
6.1.1 Drying Fluids ..........................................................................21
6.2 Trial Run .........................................................................................232
6.3 Tissue Preparation .........................................................................23
6.3.1 Washing .................................................................................24
6.3.2 Fixation ...................................................................................25
6.3.3 Dehydration ............................................................................25
6.3.4 Substitution .............................................................................26
6.4 Complete Trial Operation Run .......................................................26
Section 7 - Maintenance ..........................................................................................28
7.1 Chamber Components....................................................................29
7.1.1 Viewing Window Maintenance ...............................................29
7.1.2 End Plate Maintenance ..........................................................29
7.1.3 Drain Valve Maintenance .......................................................29
7.1.4 Gas Control Valve Maintenance ............................................29
7.1.5 Inlet/Vent Valve Maintenance ................................................30
7.1.6 Gauge Maintenance ...............................................................30
7.1.7 Transfer Boat Maintenance ....................................................31
7.1.8 Bursting Disc Assembly .........................................................31
7.2 Troubleshooting .............................................................................32
7.3 Preventive Maintenance ................................................................32
Section 8 - Spare Parts & Accessories...................................................................33

SPI Supplies 7 SPI-DRY Critical Point Dryer
1.3 Illustrations
Figure 2.1 - Hazard Warning Symbols .......................................................................9
Figure 2.2 - International Warning Symbols ...............................................................9
Figure 2.3 - Typical Signs as shown in this Manual....................................................10
Figure 2.4 - Typical Signs as shown in this Manual ...................................................10
Figure 2.5 - Typical Warnings, as shown in this Manual ............................................10
Figure 6.1 - Phase Diagram .......................................................................................21
Figure 6.2 - Process Flow Chart ................................................................................24
Figure 7.1 - Cross section of SPI DRY Critical Point Dryer ........................................28
Figure 7.2 - Gauge Mountings ...................................................................................30
Figure 7.3 - Safety Valve Assembly............................................................................31
1.4 Tables
Table 2.1 - Personal Operational Risks .....................................................................11
Table 7.1 - Troubleshooting .......................................................................................32
Table 7.2 - Preventive Maintanence ..........................................................................32
Table 8.1 - Spare Parts ..............................................................................................33
Table 8.2 - Accessories ..............................................................................................33

SPI Supplies 8 SPI-DRY Critical Point Dryer
2 HEALTH AND SAFETY
Safety is very important when using any instrumentation and all users of our equipment should read
this section.
This section of the Manual applies to all specimen preparation equipment supplied by SPI Supplies,
not just the particular instrument for which the manual refers.
Included in this section are details on warning notations and good working practices.
2.1 Safety Policy
This section contains important information relating to all health and safety aspects of the equipment.
As such it should be read, and understood, by all personnel using the instrument whether as an
operator or in a service capacity.
SPI Supplies is committed to providing a safe working environment for its employees and those that
use its equipment.
SPI Supplies regularly reviews its operations to make environmental, health and safety improvements
in line with applicable legislation.
The equipment has been designed as a free-standing bench mounted instrument. SPI Supplies cannot
be held responsible for any damage, injury or consequential loss arising from the use of its equipment
for any other purposes, or any unauthorized modifications made to the equipment.
All service work carried out on the equipment should only be undertaken by suitably qualified
personnel. SPI Supplies is not liable for any damage, injury or consequential loss resulting from
servicing by unqualified personnel. SPI Supplies will also not be liable for damage, injury or
consequential loss resulting from incorrect operation of the instrument or modification of the instrument.
2.2 Conformity
This instrument is supplied in a form that complies with the protection requirements of the EC
Electromagnetic Compatibility Directive 89/336/EEC and the essential health and safety requirements
of the low voltage directive 72/23/EEC both as amended by 92/31/EEC. Any modifications to the
equipment, including electronics or cable layout may affect the compliance with these directives.
2.3 Servicing
2.3.1 Disclaimer
All service work on the equipment should be carried out by qualified personnel. SPI Supplies cannot
be liable for damage, injury or consequential loss resulting from servicing from unqualified personnel.
SPI Supplies will also not be liable for damage, injury or consequential loss resulting from incorrect
operation of the instrument or modification of the instrument.
2.3.2 Operators and Service Engineers
A normal operator of the equipment will not be trained in or qualified for service work on the equipment
and may cause a hazard to himself/herself or others if such work is attempted. Operators should
therefore restrict themselves to the normal operation of the equipment and not remove covers from the
electronic equipment or dismantling of the instruments.
Service Engineers who are suitably trained to assess and isolate electrical, mechanical and vacuum
hazards should be the only personnel who access the equipment.
2.4 Hazard Signals and Signs
2.4.1 Hazard Signal Words
The standard three hazard signal words are defined as follows:
DANGER - imminently hazardous situation or unsafe practice that, if not avoided, will result
in death or severe injury.
WARNING - potentially hazardous situation or unsafe practice that, if not avoided, could
result in death or severe injury.

SPI Supplies 9 SPI-DRY Critical Point Dryer
CAUTION - potentially hazardous situation or unsafe practice that, if not avoided, may result
in minor or moderate injury or damage to equipment.
2.4.2 Hazard Labels used on Equipment
Several hazard symbols may be found on the equipment, they are shown below with their meaning:
Caution, risk of electric shock
Caution (refer to accompanying documents)
Easily touched higher temperature parts
Warning, risk of electric shock
Figure 2.1 - Hazard Warning Symbols
2.4.3 Hazard Warning Labels used in Equipment Manuals
The international warning signs used in equipment manuals as shown in Figure 2.2.
Figure 2.2 - International Warning Symbols
Where appropriate these are used when a specific identifiable risk is involved in either using or
maintaining the instrument. These take the form of warning triangles or signs with a graphical
description of the hazard.

SPI Supplies 10 SPI-DRY Critical Point Dryer
2.4.4 Instrument Functionality Signs
CAUTION
Extreme care should be taken during transfer to prevent surface drying of the specimen.
Should air drying occur, the specimen will be irreversibly damaged.
Figure 2.3 - Typical Warning sign as shown in this Manual
This typical sign applies to cautions where there is a risk to the functionality of equipment due to
incorrect operation. These cautions or warnings will be contained in a box and be accompanied by a
circular warning symbol as shown in Figure 2.3.
2.4.5 Serious Damage to Instruments
WARNING
Do NOT depress button “P” as this will change the program.
Figure 2.4 - Typical Warning sign as shown in this Manual
This typical caution sign is used where serious damage will be caused by incorrect operation of
instrumentation. They will follow the same form as functionality warnings but with a triangular warning
symbol as shown in Figure 2.4.
2.4.6 Hazard to Operator
WARNING
HAZARD TO HEALTH!
Risk of asphyxiation in poorly ventilated rooms.
As carbon dioxide is heavier than air, the concentration of exhaust gas will be
greater at ground level and the oxygen concentration correspondingly reduced.
Figure 2.5 - Typical Warning as shown in this Manual
These warnings will generally occur in relevant installation and maintaining sections where there exists
a potential hazard to the engineer working on the instrument. They will take the form of the triangular
warning symbol accompanied by an international warning sign and bold type lettering beginning with
“WARNING-HAZARD TO HEALTH!” as shown in Figure 2.5.

SPI Supplies 11 SPI-DRY Critical Point Dryer
2.5 Risk Analysis
2.5.1 Personal Operational Risks
The following is a list of tasks carried out by both the operator and service engineer where recognized
risks have been observed. Listed is the personnel protection equipment (PPE) which is suggested for
use for various tasks on any surface analysis equipment and systems:
Task
Carried out by
Nature of Hazard
Recommended PPE
Cleaning of parts /
samples with
isopropanol (IPA)
Operator / Service
engineer
Splash hazard to
eyes, drying of skin
Protective goggles,
protective gloves.
Use of Carbon
Dioxide
Operator / Service
engineer
Asphyxiation
Frost Burns
Use in large room with good
ventilation.
Avoid exposure to CO2 being
vented from the system.
Lifting of Heavy
Items
Service engineer
Dropping on foot.
Protective footware.
Table 2.1 - Personal Operational Risks
2.5.2 Hazardous Materials
Isopropanol (IPA)
For certain service tasks isopropanol is suggested for cleaning components before use in the
vacuum system. It should be noted that isopropanol is a flammable liquid and as such should
not be used on hot surfaces. In addition it is recommended that protective gloves be worn when
using isopropanol.
Compressed Air
Compressed air can be a potential hazard if handled inappropriately. A compressed air line may
be fed from some instruments to the customers supply, and the customer should ensure that
this and any other service pipes and cables are maintained in good condition.
Nitrogen, Argon and Helium Gas Supplies
For instruments that use nitrogen, argon or helium gas supplies for their operation, the customer
is responsible for maintaining the supply to the instrument. This supply should be regulated and
kept to the lowest pressure and flow rate that is practical to minimise the effects of any leaks.
Hazardous Gases
SPI Supplies has no control over the gases used within the system. It is therefore viewed as the
customers responsibility to assess the hazards involved and take appropriate precautions when
using explosive, toxic or corrosive gases or gases which may result in hazardous products as a
result of a chemical reaction.

SPI Supplies 12 SPI-DRY Critical Point Dryer
2.6 Good Working Practices
It is essential that good hygienic working practices are adopted at all times especially in an ultra high
vacuum or cleanroom environment and are generally of the “Common sense” type. Some simple good
practice rules are:
If in doubt don't.
If in doubt ask.
When handling solvents wear face mask, gloves, apron and work only in a well ventilated area.
Mop up any spillages immediately.
When handling or decanting mineral oils wear protective clothing.
Aerosols of mineral oils, such as that produced by gas ballasting, can prove to be hazardous
and an exhaust is recommended.
Before attempting to service electrical equipment, isolate from the mains.
Treat all unknown substances as hazardous.
Dispose of substances in an appropriate manner.
Use the correct tool for the job.
Keep a straight back and bend from the knees when lifting heavy objects.
Wear protective clothing when using liquid nitrogen.
Affix pressurised gas cylinders firmly to walls or racks. Use the correct regulating valves on gas
cylinders and always transport cylinders using the appropriate specialist trolley.
Obey safety regulations regarding lifts, hoists and machine tools.
Always make sure you understand a procedure well before attempting it for the first time.
2.7 Critical Point Dryer Specific Safety Hazards
The following Safety Hazards are specific to the SPI Supplies 13200JE-AB Critical Point Dryers.
(a) The equipment uses Liquid Carbon Dioxide (CO2) or alternatively Freon (CCIF3). Ensure the
area is adequately ventilated.
(b) High pressures inside the chamber are generated during the drying process; the instrument is
protected by a safety valve containing a thin diaphragm guaranteed to rupture at 1850 psi at
200C.
(c) All chambers and seals are pressure tested to 2500 psi by an independent authority before
shipment to the customer. Each chamber bears the serial number of that test.

SPI Supplies 13 SPI-DRY Critical Point Dryer
3 Introduction
This manual is intended for all users of the SPI Supplies SPI-DRYTM Critical Point Dryer (SPI Part
#13200JE-AB) and provides information on the installation, operation and maintenance of the
instrument.
Please note that the servicing and maintenance procedures should only be carried out by qualified
service personnel, and it is essential that all users should read the Health and Safety section of this
manual.
3.1 Return of Goods
If goods are to be returned to SPI Supplies for repair or servicing the customer should contact SPI
Supplies or their local distributor before shipment. A "Return Authorisation Number" should be obtained
in advance of any shipment. This number is to be clearly marked on the outside of the shipment. To
obtain an RA#, contact our Customer Service Department and be sure to provide us with the following
details:
* SPI Invoice Number and Invoice Date (if applicable)
* Method of shipment if applicable (post office, UPS, FedEx, Air Freight, etc.)
* Product(s) in question
* What is wrong with the product, or why do you want to make this return?
3.2 Returns Procedure
Warranty Claim
All components are sold with a return to factory warranty (unless otherwise stated) which covers
failure during the first 12 months after delivery.
Returns must be sent courier paid, SPI Supplies will cover the return courier costs. This covers
defects, which arise as a result of a failure in design or manufacturing. It is a condition of warranty
that equipment must be used in accordance with the manufacturers instructions and not have
been subjected to misuse. This warranty does not cover consumable items such as sputter
coating targets and carbon evaporation material. To make a claim under the terms of this warranty
provision contact the Customer Service Department at SPI Supplies.
Chargeable Repairs
Contact the Customer Service Department at SPI Supplies who will be able to provide an estimate
of repair costs.
Service of equipment is generally completed within twenty working days after receipt of the
equipment. A minimum evaluation fee is normally applied. Additional fees are charged as a per
hour repair rate in addition to parts.
Returns
All returns to SPI Supplies are required to follow the procedure described above in Section 3.2.
All returned items are required to have a Return Authorization Number
Packaging and Shipping
All goods shipped to the factory must be sealed inside a clean plastic bag and packed in a suitable
carton. If the original packaging is not available SPI Supplies should be contacted for advice. SPI
Supplies will not be responsible for damage resulting from inadequate returns packaging or
contamination of delicate structures by stray particles under any circumstances. All non-warranty
goods returned to the factory must be sent courrier pre-paid. They will be returned courrier, pre-
paid and added to the final invoice unless otherwise arranged.

SPI Supplies 14 SPI-DRY Critical Point Dryer
4 Description
4.1 Equipment
Each SPI-DRY Critical Point Dryer when supplied as a complete package includes the basic
instrument, specimen holder, high pressure CO2transfer hose, accessory kit, and an operation
manual. Items can be ordered as a full package or separately against the following numbers:
13200JE-AB Jumbo Critical Point Dryer, consisting of the following:
Jumbo Critical Point Dryer.
Temperature and Pressure gauges
High pressure CO2 transfer hose
Tubing for water connections
Tissue Baskets and Holder
Tool Kit
Spare Parts Kit
Operation Manual
4.1.1 Accessories
The following are accessories available from SPI Supplies, which are used with our Critical Point
Dryers.
13201-AB Grid Holder (3mm grids) for Regular Critical Point Dryer
13203-AB Grid Holder (2.3mm grids) holder for Regular Critical Point Dryer
13202J-AB Grid Holder (3mm grids) for Jumbo Critical Point Dryer
13203J-AB Grid Holder (2.3mm grids) holder for Jumbo Critical Point Dryer
Full list of consumables and spare parts is listed in Section 8.

SPI Supplies 15 SPI-DRY Critical Point Dryer
4.2 Overview
The SPI Supplies SPI-DRY Critical Point Dryer (CPD) is designed to handle the dehydration of
biological (as well as other materials) samples prior to examination the high vacuum environment of
the scanning electron microscope (SEM).
Although a variety of liquid gases may be used for the critical point drying process, the procedures
described in this document assume the use of liquid carbon dioxide (CO2), as it is the most commonly
used and least expensive option. The SPI Supplies CPDs are designed to work at the critical
temperature and pressure of CO2. The high pressure coupling hose supplied with the CPD has been
provided with the appropriate connection to a carbon dioxide siphon cylinder.
Cooling water is applied to the water jacket to lower the temperature of the chamber to below 20C.
Samples that have previously been chemically dehydrated are loaded into the chamber, which is then
filled with liquid CO2. A series of flush cycles remove the dehydration liquid and replace it with the liquid
CO2. Once the substitution is complete, the chamber is heated by flowing hot water through the jacket.
This will raise the internal pressure, taking the CO2 through its critical point. Once the critical point has
been passed, the pressure is slowly released through the vent valve, and the samples removed.
4.3 Technical Specification
4.3.1 SPI-DRY Critical Point Dryer Specifications
Specimen Chamber: 13200JE-AB: 2.50” (60mm) ID x 3.12” (78mm) deep
Front Viewing Window: 1.00” (25mm) thick toughened glass with 0.50” (12.7mm) plastic shield
Pressure Chamber: Water heated / cooled
Drying medium: Carbon Dioxide (CO2) or Freon 13 (CCIF3).
Working Pressure: 1200 psi with a critical point of approximately 350C using CO2.

SPI Supplies 16 SPI-DRY Critical Point Dryer
4.4 Physical Description
The SPI Supplies SPI-DRY Critical Point Dryers are comprised of cylindrical, water heated/cooled
pressure chambers, horizontally mounted, with attached gauges and valves.
Three manually operated valves, positioned around the chamber, are provided to control the flow of
inlet and exhaust gases, as well as the venting of the system. The pressure system incorporates a
bursting disc, rated at 1850 psi, located in the gas line between the chamber and the pressure gauge,
see figure 7.1. The disc is designed to rupture in the unlikely event of an excessive build up of pressure
in the chamber. Should this happen, all gas in the chamber is safely vented away.
All chambers and seals are pressure tested by an independent authority before shipment to the
customer. Each chamber bears the serial number of that test.
Temperature and pressure gauges allow for constant monitoring of chamber conditions.
The complete assemble consists of the following:
Pressure vessel assembly with integral water jacket, endplates (2), window, specimen loading
door, and water connectors (2)
Control valves (3)
Thermometer
Pressure Gauge
Safety Valve
Baseplate
Sample holder assembly
High pressure transfer hose
Spare parts kit
4.4.1 Pressure Vessel
The pressure vessel is machined from a solid brass bar to form a cylindrical chamber with a wall
thickness of approximately 1” (25mm). The vessel wall acts as a water jacket, with a series of narrow
bores drilled lengthwise that allow water passage for heating and cooling. The ends of the water jacket
are sealed with two annular end plates and gaskets. Two water connectors are screwed into the vessel
wall (one at each end) to allow for connection of the water supply.
Both ends of the vessel are internally threaded. The specimen loading door screws into one end, with
the viewing window located at the other end, held in place with a retaining ring. The window consists
of a 1” (25mm) piece of toughened glass, covered by a ½” (12.7mm) plastic shield, which acts as a
safety guard in the unlikely event of the glass cracking.
4.4.2 Control Valves
There are three high pressure valves (right-angle type) fitted to the pressure vessel using ¼” BSP
threaded unions. The valves seal by contact between a ground steel cone and a brass knife edge.
NOTE: Do not overtighten these valves, as doing so will impair the efficiency of the metal to
metal contact.
The INLET and VENT valves are screwed directly into the top of the pressure vessel, and seal against
O-rings. The O-rings are located on their seats by small stainless steel inserts. When the valves are
initially installed, they are adjusted so that they face the desired direction once they have been screwed
into the vessel. Locking nuts ensure they do not rotate further.
The DRAIN valve located at the bottom of the vessel is installed in a slightly different manner. A ¼” BSP
plug is sealed into the female part of the valve body with an adhesive, and this plug butts against an O-
ring seal. This method allows the valve to be conveniently mounted in the horizontal postion.
4.4.3 System Gauges
The thermometer is the bi-metallic type, and measures the temperature of the pressure vessel brass
wall. It is attached to the vessel by means of a push-fit plug inserted in the vessel wall. The gauge fits

SPI Supplies 17 SPI-DRY Critical Point Dryer
in such a way that the sensing head does not penetrate either the water jacket or the high pressure
chamber.
The pressure gauge is a 0-2000 psi bronze Bourdon gauge, which screws into a ¼” BSP threaded port
on the upper side of the vessel, and seals against a fiber washer.
NOTE: By special arrangement with the manufacturers, this gauge was calibrated using methyl
alcohol, rather than the usual mineral oil.
4.4.4 Safety Valve
The stand pillar, which supports the vessel, also incorporates the safety valve. The top of the valve
screws into the vessel and is sealed with a bonded seal. The valve exit is a small hole in the side of
the pillar.
The valve uses a nickel fuse (bursting disc), which is a thin diaphragm guaranteed to rupture at 1850
psi (+/- 5%) at 20C. If the disc ruptures as a result of excess pressure, it must be replaced. A spare
disc is included with the spare parts kit.
4.4.5 Specimen Holder
The standard specimen holder assembly consists of an aluminium alloy liquid transfer boat (with
integral drain), mesh specimen baskets, and a gauze cover. The baskets slide into the channels on
the gauze cover, ensuring they remain immersed when placed into the liquid transfer boat.
Sample preparation is carried out with the samples in the baskets to the point where final substitution
is made (pure ethanol, acetone, amyl acetate, etc.). At this point, the boat is filled with the substitution
liquid, and the basket assembly transferred to the boat.
When the liquid transfer boat is loaded into the pressure vessel, the post on the end of it fits into a hole
drilled on the chamber door. This aligns the liquid transfer boat so that when the door is sealed, the
drain valve is activated by a pin in the chamber floor. The valve aperture is small enough (.75mm) to
ensure that the samples remain covered until the chamber is filled with liquid CO2.
4.4.6 Microporous Specimen Capsules
Microporous Specimen Capsules may be used as an alternative to the mesh baskets included with the
CPD. These small, cylindrical containers protect fragile specimens during CPD, preserving three-
dimensional form for later SEM observations. The sheltered environment also protects the fragile
samples against the undesirable effects of turbulence. Both the capsule and its snug-fitting cap are
solvent resistant (not harmed by alcohol, acetone, or chloroform). Capsules can also be used as
convenient storage vessels for specimens under desiccation. The capsules measure 12mm in
diameter by 11mm high and are available in three different pore sizes, the smallest at 30 µm. The
inside diameter is 8mm, because of the roughly 2mm thickness of the wall.

SPI Supplies 18 SPI-DRY Critical Point Dryer
5 Installation
SPI Supplies carefully packs all instruments so that they will reach their destination in perfect
working order. Do NOT discard any packing materials until the unit has been inspected for any
transit damage and the instrument has been used to the customers satisfaction.
If any damage is found, notify the carrier and SPI Supplies (or local agent) immediately. If it is
necessary to return the shipment, use the packaging as supplied and follow the instructions in this
manual for return of goods paragraph 3.1.
5.1 Unpacking Checklist
The Equipment package will normally be despatched from the factory in one box. Inside the box
the following will be found, refer and check each item off against the supplied packing list.
13200JE-AB Unit, comprised of pressure vessel, pressure gauge, temperature gauge,
three control valves, base/safety valve assembly
High pressure transfer hose
Tubing for water connections
Liquid transfer boat with basket assembly
Tool kit (window retaining ring spanner & tommy-bar for specimen door removal/sealing)
Spare parts kit
Operating Manual
5.1.1 Site Selection
The critical point dryer should be positioned in the laboratory convenient for:
(a) Hot and cold water supply
(b) Good ventilation
(c) Space for carbon dioxide siphon cylinder

SPI Supplies 19 SPI-DRY Critical Point Dryer
5.2 Connection of Services
Once unpacked and inspected, the critical point dryer should be secured to the surface where it will be
used. There are two ¼” BSF tapped holes in the bottom of the base on a 5½” (127mm) PCD. These
holes are to allow the CPD to be mounted to the bench top.
5.2.2 Water
Cut a suitable length of the included tubing to connect the water inlet port on the pressure vessel to the
hot/cold water supply.
If connecting to individual hot and cold water taps, it may be more convenient to connect both taps to a
“Y” adapter, and connect the adapter to the pressure vessel. This will allow for convenient changing
from cold water to hot water, and also allow for fine control over the water temperature, which will give
better control over the heating rate. Another possibility, if available, is the use of a water re-circulator
that allows for precise control of the temperature.
Connect a second piece of tubing from the water outlet on the pressure vessel and run it to the drain (or
to the water re-circulator, if using one).
NOTE: Running mains water to waste may contravene local regulations. If in doubt, the user is
advised to seek advice from the local water authority.
5.2.3 Carbon Dioxide (CO2)
The critical point dryer requires a cylinder of liquid CO2fitted with a siphon tube. If there is any doubt
regarding the presence of a siphon tube, advice should be sought from the gas supplier.
Using the included fiber washer, connect the high pressure transfer hose to the INLET valve of the
pressure vessel. The fiber washer is necessary to ensure a good seal. Tighten with a ¾” wrench.
Connect the other end of the high pressure transfer hose to the CO2cylinder. Tighten with a 1 1/8”
wrench.
Please note that cylinder connection threads may vary from country to country, and manufacturer to
manufacturer. There is an included adapter that may or may not be necessary, depending on the threads
on the CO2tank. If it is found to be necessary to fabricate an adapter, advice should be sought from a
local supplier of high pressure gas fittings.
5.2.4 Carbon Dioxide (CO2) Exhaust
During operation of the Critical Point Dryer, it is usual to monitor the presence of intermediate fluid
(acetone/ethanol) in the exhausting gas. For this reason it is unwise to make a permanent connection
to the exhaust port. An arrangement incorporating an in-line type breakable connection would be more
practical. With this method, except during gas monitoring, the exhausting CO2can be piped into a fume
hood or out through an open window, if desired.
WARNING
HAZARD TO HEALTH!
Risk of asphyxiation in poorly ventilated rooms.
As carbon dioxide is heavier than air, the concentration of exhaust gas will be
greater at ground level and the oxygen concentration correspondingly reduced.
During the flushing, the CO2exhaust is very cold, and can cause frost burns.
WARNING
If the apparatus is not secured, there is a risk that it could slide
off the bench top in the event of the safety valve rupturing.
CAUTION
Before attempting to remove the high pressure hose, close the cylinder control valve
and release any gas pressure in the pipe by opening the CPDA inlet and drain valves.

SPI Supplies 20 SPI-DRY Critical Point Dryer
6 Operation
6.1 Critical Point Drying Method
The phase diagram (Figure 6.1) shows the pressure to temperature ranges where solid, liquid and
vapour exist. The boundaries between the phases meet at a point on the phase diagram called the triple
point. Along the boundary between the liquid and vapor phases it is possible to choose a particular
temperature, and corresponding pressure, where liquid and vapor can co-exist and hence have the
same density. This is the critical temperature and pressure.
Critical Point Drying relies on this physical principle. The water in biological tissue is replaced with a
suitable inert fluid whose critical temperature for a realizable pressure is just above ambient. The choice
of fluids is severely limited and Carbon Dioxide (CO2) is universally used today despite early work with
Freon 13 and Nitrous Oxide. With CO2, a critical point of approximately 35OC can be achieved at a
pressure of around 1200 psi. Therefore, if the water is replaced with liquid CO2and the temperature then
raised to above the critical temperature, the liquid CO2changes to vapour without change of density and
therefore without surface tension effects which distort morphology and ultra-structure. Since liquid CO2
is not sufficiently miscible with water, it is necessary to use an intermediate fluid, which is miscible with
both water and liquid CO2. In practice, intermediate fluids commonly used are methanol, ethanol, amyl
acetate and acetone.
Figure 6.1 - Phase Diagram
6.1.1 Drying Fluids
The two drying fluids in general use are liquid carbon dioxide and Freon 13. Their critical points are as
follows:
Carbon Dioxide (CO2) 31.5OC, 1100 psi (75bar)
Freon 13 (CCIF3) 28.8OC, 560 psi (38bar)
The critical point of Freon 13 is considerably lower than that of carbon dioxide but this gives no particular
advantage. The usual deciding factor is the price. Freon 13, besides the environmental effects, is about
twenty times more expensive than carbon dioxide and is not so readily available. These considerations
have made carbon dioxide the most widely used drying fluid.
The transfer pipe provided with the critical point dryer is suitable for use with a ‘siphon’ type cylinder.
Also, best results are obtained when using CO2with as little moisture content as possible.When ordering
CO2 tanks, make sure to specify “dry liquid CO2in a siphon tank”.
NOTE: It will be assumed in the following text that CO2is being used as the drying fluid.
6.2 Trial Run
Before processing samples for the first time, it is suggested to run the CPD without any samples in order
to gain familiarity with the process and the controls.