Critical point dryer (CPD)

3D Micromanufacturing Lab.School of MechatronicsGwangju Institute of Science and Technology 3D Micromanufacturing Lab.School of MechatronicsGwangju Institute of Science and Technology

Critical point dryer (CPD)

[1]


The phase diagram shows the pressure to temperature ranges where solid, liquid and vapor 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 tem-

perature, and corresponding pressure, where liquid and vapor can co-exist and hence have the same

density. This is the critical temperature and pressure.

What is the critical temperature and pressure?

[2]


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 35 °C can

be achieved at a pressure of around 1200 psi.

Therefore, if the water is replaced with liquid CO2 and the temperature then raised to above the crit-

ical temperature, the liquid CO2 changes to vapor 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.

What is the critical point drying?

[3]


Specifications (E3000)Chamber size Horizontal 30 mm internal diameter x 82 mm long

Front Viewing Window 25 mm thick toughened glasswith clear plastic shield 12.7 mm thick

Pressure Chamber Water cooled

Drying medium Carbon Dioxide (CO2) or Freon 13 (CCIF3)

Operating temperature Normal operating temperature 35°C(critical temperature: 31°C)

Operating pressure 1200 psi with a critical point of approximately 35 ℃using CO2 (critical pressure of CO2 is 1172psi)

Pressure safety cut-out 1850 psiChamber heating chamber Controlled by thermocirculator

Chamber cooling Cooled down by connecting the thermocirculator coolingcoil to the main water supply or cooling water circulator

Sample insertion Specimen boat provided for easy on insertion of specimenBaskets into chamber

[4]


Specifications (RW-0525G)Bath Volume (L) 5

Working Temperature Range ( )℃ -25 to 150

Temperature Stability (± )℃ 0.05

CoolingCapacity

at -20 , W℃ 30

at 0 , W℃ 230

at +20 , W℃ 320

Refrigerator 1 / 3 LBP, R-134A

PumpMax. Pressure, Max. Flow rate 406.8 millibar, 28 liters / minute

Max. Suction Flow Rate 10 liters / minute

Dimension

Bath Opening, Depth (W×L, D) (mm) 150×99, 160

Overall (W×L×H) (mm) 302×438×690

Net Weight (kg) 37

Electrical Requirements (230V, 60Hz) 7A

Electrical Requirements (230V, 50Hz) 7A

Electrical Requirements (120V, 60Hz) 12.6A

[5]


Composition of instruments

[6]


Composition of CPD

[7]


Composition of CPD cont.1. Pressure Vessel: The pressure vessel is machined from solid brass bar to form a cylindrical tube with a wall

thickness of approximately 25 mm. The vessel wall acts as a water jacket, with a series of narrow bores, drilled

lengthways, forming a water passageway for chamber heating and cooling. The ends of the water jacket are

sealed with annular end plates and gaskets. Two hose connectors are screwed into the vessel wall, one at each

end, for connection to a water supply. Each end of the vessel is internally threaded. A 25 mm thick, toughened

glass, viewing window is held in one end by a retaining ring, and a specimen loading door screws into the other

end. A 12.5 mm thick clear plastic shield is screwed over the viewing window and acts as a safety guard in the

unlikely event of the glass cracking.

2. Control Valves: There are three high pressure valves, of the right-angle type, fitted to the pressure vessel using

1/4" BSP threaded unions. The valves seal by contact between a ground steel cone and a brass knife edge.

NOTE: That the efficiency of the valve will be impaired if this metal to metal contact is overtightened.

The INLET and OUTLET valves are screwed directly into the top of the pressure vessel and seal against an O-

ring. The O-rings are located on their seats by small stainless steel inserts. When the valves are initially fitted,

they are adjusted so that the valves face the desired direction when they have been screwed into the vessel.

Locking nuts ensure the valves do not rotate. The DRAIN valve screws into the bottom of the vessel horizon-

tally via an adapter plug.

[8]


Composition of CPD cont.3. Gauges: The thermometer gauge is of the bi-metallic type and measures the temperature of the pressure vessel

brass wall. It attaches to the vessel by means of a push-fit plug inserted in the vessel wall. The gauge screws

into the plug such that the sensing head does not penetrate either the water flow in the jacket or the high pres-

sure work chamber. The pressure gauge is a 0 ~ 2000 psi bronze Bourdon gauge which screws into a 1/4" BSP

threaded port in the upper side of the vessel, and seals onto a fibred washer. NOTE:

By special arrangement with the manufacturers, these gauges are calibrated using methylated spirit

rather than the usual mineral oil.

4. Safety Valve: 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 20 . If the disc ruptures as a result of excess pressure, it has to be replaced. A ℃spare bursting disc is included with the apparatus when shipped. 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

and is supplied with the test certificate.

[9]


Composition of CPD cont.5. Specimen Holder Assembly: The standard specimen holder assembly, Figure consists of a liquid transfer boat,

mesh specimen baskets and a stainless steel gauze cover. The transfer boat is an aluminum dish with an integral

drain valve and holds the specimens, immersed in substitution fluid (acetone, amyl acetate, freon 113, etc.),

during transfer to the pressure chamber. During transfer, a spigot on the end of the transfer boat locates into a

drilled hole in the center of the inside face of the chamber door. In this way, the transfer boat can be carried by

the door and loaded into the chamber. As the boat is loaded, the drain valve is activated by a locating pin em-

bedded in the chamber floor. The valve aperture is sufficiently small (0.75 mm) to ensure the specimens remain

covered until the chamber is filled with liquid CO2. The specimen baskets slide into channels formed by the

gauze cover returned edges. The cover then fits over the liquid transfer boat, immersing the baskets into the

substitution fluid. Various designs of transfer boat and specimen holder are available, with internal slots and

cutouts to accommodate different specimen types and sizes (i.e. glass slides, coverslips and wire tissue

baskets).

[10]


Installation of CPD1. Cut a suitable length of the 6 mm PVC tubing (supplied) and connect between the hot/cold water supply, and

the water inlet connector on the CPDA. It will be convenient to attach a water mixer to the laboratory hot and

cold water outlets, terminating with a 6mm (1/4") hose connection for the PVC tubing supplied, (a “Y” piece

connected to the hot and cold water taps is suitable). The CPDA requires both hot and cold water during the

operating cycle. Cooling facilitates filling of the work chamber with liquid CO2 and heating is required to take

the liquid above its critical point.

2. Similarly, connect a length of PVC tubing between the water outlet connector on the CPDA and a convenient

drain. 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.

3. Connect the transfer pipe to the INLET valve on the CPDA. A fibred washer is provided to ensure a good seal.

4. Using a 3/4" AF spanner, tighten the union to approximately 20 ft lb.

5. Connect the other end of the transfer pipe to the gas cylinder. No gasket is required. Cylinder connection

threads vary from country to country and even between manufacturers in the same country. For example, the

transfer pipe supplied is fitted with 1/4" British Standard Pipe (BSP) and 0.860” x 14 tpi. unions. Standard

threads for the UK, but will not fit cylinders in the USA. An E3000-US kit should be specified for use within

the USA, this includes a transfer pipe adaptor which will fit USA cylinders. If it is found necessary to fabricate

another transfer pipe, advice should be sought from a local supplier of high pressure fittings.

[11]


Installation of CPD cont.6. Tighten the securing nut with a 1 1/8"AF spanner taking care not to twist the transfer pipe.

Check the transfer pipe connections for leaks by first ensuring the INLET valve is closed and then gradually opening

the control valve on the gas cylinder. Any leaks will be audible, or visual if severe. A leak from either of the transfer

pipe connections can be cured by re-tightening the union.

CAUTION: Before attempting to re-tighten a transfer pipe union, close the cylinder control valve and release

any gas pressure in the pipe by opening the CPDA inlet and drain valves.

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.

[12]


CPD operation instruction

[13]

1. Close all valves on the pressure vessel. Do not over-tighten as this will damage the sealing seats.

2. Open the CO2 cylinder control valve.

3. Open the INLET valve on the pressure vessel and listen for any slight leak. If any of the valves have loosened

during transit they should be tightened. With the INLET valve open, and the VENT and DRAIN valves

closed, the pressure vessel will partially fill with liquid CO2. The rate and extent of filling can be increased by

slowly opening the VENT valve on the top of the unit. This will flush through any trapped air in the system.

CAUTION: Before attempting to re-tighten a transfer pipe union, close the cylinder control valve and release

any gas pressure in the pipe by opening the CPDA inlet and drain valves.

4. It is useful at this stage to experiment with the manipulation of the control valves. It will be seen that if the IN-

LET and DRAIN valves are both opened, a constant level of liquid can be maintained, as seen through the

viewing window. This is the FLUSHING action. It is sometimes necessary to open the VENT valve as well to

prevent the liquid level from falling

NOTE: The pressure vessel will be difficult to fill if it is warmer than the cylinder. Although a con-

stant throughput of liquid gas will adiabatically cool the vessel by expansion through the DRAIN

valve, additional water cooling is still recommended.


CPD operation instruction cont.

[14]

5. Having experimented with filling and flushing the work chamber, fill the chamber half full and

close all valves.

6. Turn on the hot water supply (at 35- 40 ) to slowly raise the chamber temperature. At first some ℃

turbulence will be observed in the liquid CO2. If the turbulence is violent, this indicates the heat-

ing rate is excessive.

7. Observe the liquid CO2 through the viewing window and at the same time monitor the TEM-

PERATURE and PRESSURE gauges. As the temperature of the vessel approaches 30 , the ℃pressure will have risen to approx. 1100 psi. As this point is reached, the surface of the liquid will

start to dissolve. When the pressure is greater than 1200 psi, the liquid meniscus will have disap-

peared and the CO2 will have passed through the CRITICAL POINT.

There are 3 indications that the critical point has been exceeded:① The visible effect② The pressure is above 1200 psi③ The temperature is above 32 ℃

The temperature is the least reliable of the indications because of the possibility of thermal lag.


CPD operation instruction cont.

[15]

8. Repeat the above experiment a number of times to become experienced with the critical point ef-

fect.

NOTE: Unreliable pressure readings will be obtained if the liquid level is above the inlet to the

PRESSURE gauge during the heating process.

9. When the chamber contains gas at a temperature above the critical point (36 gives a suitable ℃margin), experiment with the release of pressure from the chamber by gradually opening the

VENT valve. If the pressure is released too quickly, re-condensation of the gas will occur by adi-

abatic cooling. The VENT valve should be controlled to give a venting time of between 3 and 4

minutes.

10. After a critical point run, cool the chamber to below 20 before attempting to re-use.℃


Composition of low temp. bath circulator (LTBC)1. Display2. Over-Temp. Protector3. Communication Port4. Main Power Switch5. Fuse6. Drain Valve7. Ref. system8. Condenser Cover

[16]


Display of LTBC

[17]


Display of LTBC cont.1. RUN LED: This LED indicates Work/Stop state of unit. It turns on when the unit runs and turns down when

the unit stops

2. HEATER LED: This LED indicates heater is activated.

3. Auto Tuning LED: This LED indicates Auto Tuning is proceed

4. Wait On Timer LED: This LED indicates state of timer, which makes the unit begin to run on programmed

time. The LED is blinking when the timer is activated and turns off when the timer is deactivated

5. Wait Off Timer LED: This LED indicates state of timer, which makes the unit stop on programmed time in-

terval since the PV and SV meet each other. The LED is blinking when the timer is activated and turns off

when the timer is deactivated.

6. Low-level alarm LED: This is device monitoring low level of heat transfer media such as water, alcohol, oil

etc. inside of the bath. This can be used in high temperature environment and has good durability by using

unique Jeio tech. made sus-ball. This stops instrument and alarm buzzer when it monitor low level. You have to

refill liquid and resume operation by pressing Start/Stop button.

7. Over heating alarm LED: It stops instrument, alarm buzzer and over heating alarm LED is blinking when the

temperature of media liquid inside of the bath is higher than set value of mechanical over heating prohibit de-

vice on the front panel. In this case the instrument halted because of some unstable factor (over heating) there-

fore remove over heating factor and press Start/Stop button once then the Buzzer and blinking LED set normal

state.

[18]


Display of LTBC cont.8. Temp button: This button is for temperature setting.

9. Timer button: This button is for setting the timer, Auto Run function, and pump circulating capacity

10. Up button: This button is for increasing set value.

11. Enter button: This button is for saving value after varying set value.

12. Down button: This button is for decreasing set value.

13. Lock button: This is to lock the controller buttons.

14. Auto Tuning button: A function operates if it presses this button for three seconds when it practices Auto Tun-

ing.

15. Start/Stop button: This button is for start/stop of unit and for resuming operation after removing some unsta-

ble factors when operation is terminated because of it.

16. SV button: This button is for showing set temperature and showing remaining time when the timer function is

activated.

17. PV button: This button is for showing present temperature.

[19]


LTBC operation instruction

[20]

1. Basic operation

① Fill with water or transfer media before connecting to the mains power supply.

② Please check main power is correct.

③ Set the Over Temp. Protector Knob higher than operating temperature (about 10%).

④ Connect mains power, turn on Main Power Switch and input desired temperature.

2. Temperature setting method

① Press button. Set temperature value (SV) should blink. This means you can vary set

value.

② Press button to change value then press button to save the value.

③ It reverts to the previous value without saving if you don’t touch any button for 10 seconds.

④ Press button again when it is in SV set state then following additional functions are acti-

vated.


LTBC operation instruction cont.

[21]

3. Additional function of button

1) SV storing function.

① Press button 2 times. This function is to store a favorite value at SV.1 and load it. Press but-

ton and button to vary temperature and press button to store.

② Press button 3 times. This function is to store a favorite value at SV.2 and load it. Press but-


③ Press button 4 times. This function is to store a favorite value at SV.3 and load it. Press but-


2) Unit change.

① Press button 5 times. This is a function vary the unit of temperature display. Initial display

is and it can be varied and by pressing button. Press button to store.℃ ℃ ℉

3) Bias Function.

① Press button 6 times. This is a temperature deviation compensation function. PV shows

BAIS compensation values and SV shows BIAS condition. Move to ADJUST mode by pressing

or button. Change the value on PV display the same as the thermometer in the chamber by

pressing and . Conclude the setting by pressing .



[22]

4. Timer set way

1) Wait on Timer.

① Press button one time. Timer (On Timer / Off Timer) is shown on PV and time is shown on

SV. Set time by pressing button and Save and finish by pressing button.

② W/ON LED turns on with a Beep sound after finishing the wait on timer setting.

2) Wait off Timer.

① Press button two times. You can now set the wait off timer. Set time by pressing but-

ton and save and finish by pressing button.

② W/OFF LED turns on with a Beep sound after finishing the wait on timer setting.

③ The timer function is shown below.



[23]

Wait On Timer

• The unit begins to work when the time programmed into ‘Wait On’ is attained.

• Maximum is 99 hr. 59 min. and minimum is 1min..

Wait Off Timer

• The unit stops when the time programmed into ‘Wait Off’ is attained.

• Combination of Wait On Timer & Wait Off Timer.

• The unit works as picture.

④ Timer set deactivation: Press button to deactivate the timer function (LED and timer turns

off). If you want only one timer mode, set the value of the timer for 0, the timer is then deacti-

vated.

5. Additional function of button

1) Auto Run function.

① Press button 4 times. This is to select the machine mode after power failure. If you set ‘yes’

the unit will run after power failure situation. If ‘no’ is selected it will not resume after any power

failure.

2) Pump circulating capacity control.

① Press button 5 times. This is to control motor speed. Control range: 1~5 by pressing

and . Press button to finish setting. (Motor speed is set at 5 as factory default.)

Documents

Critical point dryer (CPD)