Isotech B8-30-130 Operating instructions

Isothermal Technology Limited, Pine Grove, Southport, Merseyside, PR9 9AG, England
Telephone: [phone] Fax: [phone] Email: [e-mail] Website: www.isotech.co.uk
Page 1of 10 WTPC B12 & B8 –Issue 8 (07/20)
WATER TRIPLE POINT CELLS
MODELS B12 & B8
User Maintenance Manual/Handbook

Page 2of 10 WTPC B12 & B8 –Issue 8 (07/20)
ⓒIsothermal Technology Limited
The company is always willing to give technical advice and assistance where appropriate. Equally,
because of the programme of continual development and improvement we reserve the right to amend or
alter characteristics and design without prior notice. This publication is for information only.
Isothermal Technology Limited
Pine Grove, Southport, Merseyside, PR9 9AG, England
Telephone: [phone]/544611 / Fax: [phone]
Email: [e-mail] / Website: www.isotech.co.uk

Page 3of 10 WTPC B12 & B8 –Issue 8 (07/20)
CONTENTS
INTRODUCTION...............................................................................................................................................................4
SPECIFICATION ..............................................................................................................................................................5
PREPARATION OF B12 AND B8 TYPE WTP CELLS USING THE SUPERCOOL AND NUCLEATION METHOD
(SLUSH METHOD) IN CONJUNCTION WITH ISOTECH EQUIPMENT.........................................................................6
DRY BLOCK BATHS .....................................................................................................................................................6
STIRRED LIQUID BATHS .............................................................................................................................................7
PREPARATION OF B12 AND B8 TYPE WTP CELLS USING THE LIQUID NITROGEN COOLED METAL ROD
METHOD...........................................................................................................................................................................9
PREPARATION OF B12 TYPE WTP CELLS USING THE ISOTECH MODEL 452 ICE MANTLE MAKER................10

Page 4of 10 WTPC B12 & B8 –Issue 8 (07/20)
INTRODUCTION
A triple point of water cell consists of a volume of distilled water sealed under vacuum within a glass
cylinder containing a re-entrant tube. By semi-freezing the water a situation arises where water, ice and
water vapour exist together in equilibrium. This can only occur at +0.01°C. A sensor placed in the re-
entrant tube will attain this temperature within the tolerance quoted above.
The Water Triple Point Cell is unique.
1. It is a defining point of ITS-90
2. It is used to check the R0.01 value of platinum resistance temperature sensors (or derive the R0
value)

Page 5of 10 WTPC B12 & B8 –Issue 8 (07/20)
SPECIFICATION
MODEL NO.
B8-30-130
B12-46-210
B12-40-210
Size: Length
Diameter
175mm
30mm
355mm
46mm
350mm
40mm
Re-entrant tube: Length
Internal Diameter
140mm
8mm
320mm
12mm
320mm
12mm
Immersion depth within the ice mantle:
(±10mm)
130mm
210mm
210mm
Uncertainty (2 Sigma) (when ordered with
UKAS calibration):
±0.0005°C
±0.0005°C or
±0.0001°C
±0.0005°C or
±0.0001°C

Page 6of 10 WTPC B12 & B8 –Issue 8 (07/20)
PREPARATION OF B12 AND B8 TYPE WTP CELLS USING THE
SUPERCOOL AND NUCLEATION METHOD (SLUSH METHOD) IN
CONJUNCTION WITH ISOTECH EQUIPMENT
Important Note: Since water triple point cells are liquid in a thin glass container under vacuum, Isotech
cannot accept responsibility for breakages and whilst every attempt is made to pack these cells so that they
arrive undamaged, the purchaser should obtain insurance in transporting the cells.
B12 and B8 type water triple point cells can be realised in a variety of Isotech equipment, the procedural
details are generally the same, however the following sections highlight the differences and precautions
that must be taken into account.
DRY BLOCK BATHS
Please note that the container, adaptor rings etc…referenced below are only provided when the water
triple point cell is purchased with an Isotech block bath.
1. Prior to realisation ensure the re-entrant tube of the cell is free from water, this can be achieved by
washing the re-entrant tube of the cell with alcohol before discarding the liquid.
2. For the B12 type Water Triple Point Cells, the adapter rings (provided with the cell when purchased
with the block bath) should be fitted above and below the cell so that the cell sits centrally in the
block. The top of the well should then be thermally insulated with foam, tissue paper or expanded
polystyrene.
3. For the B8 type Water Triple Point Cells, place the metal container (provided with the cell when
purchased with the block bath) into the well of the block bath, gently place the cell into this and
insulate the top with one of the polystyrene blocks (provided with the cell when purchased with the
block bath).
4. Switch on the block bath and set the temperature to -7°C. The block bath will cool much quicker
than the cell because there is an air gap between the cell and the block, therefore monitor the
temperature of the cell using a thermocouple or resistance thermometer inside the cells re-entrant
tube. (a small amount of acetone or alcohol can be inserted into the re-entrant tube to a depth of
10mm to provide good thermal transfer between the cell and the monitor thermometer)
Important Note: It is critical during this cool down period that the cell or monitor thermometer are not
inadvertently knocked, vibrated or generally disturbed as this may cause the super-cooled water inside the
cell to nucleate. If left unchecked the ice mantle will grow, internally pressurising the cell, which will lead to
cells failure.
5. When the temperature in the cell has reached -6°C gently remove the cell from the bath and,
supporting the base of the cell in one hand, gently flick the top of the cell to one side, (disturbing the
meniscus) where upon ice forms from the top downwards, the temperature inside the cell will
immediately rise to the triple point value (0.01°C).
6. In order to stabilise the ice structure, the cell is returned to the block bath at -7°C. It is left there for
10 minutes to stabilise.
7. After 10 minutes the cell is then removed from the block bath and the outer surface of the cell is
warmed by hand until a thin layer of water is observed between the outer glass and the ice mantle,
this is to reduce any internal pressure.

Page 7of 10 WTPC B12 & B8 –Issue 8 (07/20)
8. The cell is returned quickly to the block bath and the temperature increased to -0.1°C. This
gradually causes the ice to grow back to the outer wall of the cell so the ice mantle should be
checked regularly and if required the outer surface of the cell warmed by hand again.
Important Note: Knowledge of the dry block bath controller error is critical in order to ensure that the
temperature of the block bath actually attains -0.1 °C, a temperature lower may cause an increase in the
growth of the ice mantle and a temperature higher may cause the ice mantle to melt.
9. Once the block bath and cell are stable at -0.1 °C the cell can be removed from the block bath and
the monitor thermometer can be removed from the cell. A 6mm diameter solid metal rod can be
carefully inserted into the re-entrant tube along with sufficient alcohol to come up to the level of ice
inside the cell. Simultaneously the outer glass can be warmed by hand again. By tilting the cell 45°
from vertical the ice mantle should be seen to be free to rotate - the cell should never be twisted or
spun
Important Note: This should be done relatively quickly to avoid melting too much of the ice mantle but
always with care.
10. Once the ice mantle is seen to rotate the cell should be returned to the block bath and the cell is
now ready for use.
During normal use the cell should be regularly inspected and if necessary, the ice mantle should be freed
from the outer wall of the cell and re-entrant tube of the cell as before.
STIRRED LIQUID BATHS
Important Note: In a stirred liquid the thermal transfer between the cell and liquid in the bath (alcohol) will
be up to 20 times faster than it would if the cell was surrounded by air (as in the dry block bath) therefore
continuous monitoring is required.
1. Prior to realisation ensure the re-entrant tube of the cell is free from water, this can be achieved by
washing the re-entrant tube of the cell with alcohol before discarding the liquid.
2. For both B12 and B8 cells the appropriate cell holder assembly for the stirred liquid bath should be
used at all times.
3. Switch on the stirred liquid bath and set the temperature to -7°C. The liquid in the bath will cool
quicker than the cell, therefore monitor the temperature of the cell using a thermocouple or
resistance thermometer inside the cells re-entrant tube (a small amount of acetone or alcohol can
be inserted into the re-entrant tube to a depth of 10mm to provide good thermal transfer between
the cell and the monitor thermometer)
Important Note: It is critical during this cool down period that the cell or monitor thermometer are not
inadvertently knocked, vibrated or generally disturbed as this may cause the super-cooled water inside the
cell to nucleate. If left unchecked the ice mantle will grow, internally pressurising the cell, which will lead to
cells failure.
4. When the temperature in the cell has reached -6°C gently remove the cell from the cell holder and,
supporting the base of the cell in one hand, gently flick the top of the cell to one side, (disturbing the
meniscus) where upon ice forms from the top downwards, the temperature inside the cell will
immediately rise to the triple point value (0.01°C).
5. In order to stabilise the ice structure, the cell should be immediately returned to the cell holder and
the temperature of the bath set to -0.1°C.

Page 8of 10 WTPC B12 & B8 –Issue 8 (07/20)
Important Note: Knowledge of the stirred liquid bath controller error is critical in order to ensure that the
temperature of the stirred liquid bath actually attains -0.1°C, a temperature lower may cause an increase in
the growth of the ice mantle and a temperature higher may cause the ice mantle to melt.
6. Once the stirred liquid bath and cell are stable at -0.1°C the cell can be removed from the cell holder
and the monitor thermometer can be removed from the cell. A 6mm diameter solid metal rod can be
carefully inserted into the re-entrant tube along with sufficient alcohol to come up to the level of ice
inside the cell. Simultaneously the outer glass can be warmed by hand again. By tilting the cell 45°
from vertical the ice mantle should be seen to be free to rotate - the cell should never be twisted or
spun
Important Note: This should be done relatively quickly to avoid melting too much of the ice mantle but
always with care.
7. Once the ice mantle is seen to rotate the cell should be returned to the cell holder and the cell is
now ready for use.
During normal use the cell should be regularly inspected and if necessary the ice mantle should be freed
from the outer wall of the cell and re-entrant tube of the cell as before.
The procedures above are for guidance only, with time and experience the user should produce a detailed
procedure which best suits their working schedule.
For example, the optimum temperature to maintain the cell at can only be found following repeated use as
this will depend on:
•The number of sensors required to be calibrated.
•The ambient temperature.

Page 9of 10 WTPC B12 & B8 –Issue 8 (07/20)
PREPARATION OF B12 AND B8 TYPE WTP CELLS USING THE
LIQUID NITROGEN COOLED METAL ROD METHOD
This method describes an alternative way of creating an ice mantle in Isotech B12 and B8 type cells should
an Isotech bath not be available. It utilises 6mm diameter solid metal rods that have been cooled in Liquid
Nitrogen (-195.798°C).
1. Prior to realisation ensure the re-entrant tube of the cell is free from water, this can be achieved by
washing the re-entrant tube of the cell with acetone or alcohol before discarding the liquid.
2. The re-entrant tube of the cell should then be partially filled with acetone or alcohol (enough to fill
the re-entrant tube when the metal rod is in place).
3. Then pre-cool the cell to 0°C for at least 1 hour in a container of crushed ice.
4. Once the cell is cool, leave it in the crushed ice and introducea pre-cooledmetal rod slowly and gently
into the cell re-entrant tube, the ice mantle will be seen to slowly form around the re-entrant tube.
Important Note: Any ice-bridge (freezing of the meniscus of the water) forming inside the cell must be
warmed and melted immediately by hand or the cell may rupture.
5. Continue in this way until the ice mantle is the required thickness, generally 60-70% of the distance
between the re-entrant tube and the outer glass.
Important Note: On no account should the mantle be so thick as to impinge on the outer glass of the cell
or it could rupture.
6. Once the mantle is complete the alcohol should be removed from the re-entrant tube and an ambient
temperature 6mm diameter solid metal rod can should be carefully inserted into the re-entrant tube
along with sufficient alcohol to come up to the level of ice inside the cell. By tilting the cell 45° from
vertical the ice mantle should be seen to be free to rotate - the cell should never be twisted or spun
7. Once the ice mantle is seen to rotate the cell should be returned to the container of crushed ice, the
cell is now ready for use.
8. The cell should be inspected regularly for ice bridge formation, mantle growth or checked for free
rotation of the mantle as before. If it is found not to rotate the outer surface of the cell should be
warmed by hand and an ambient temperature metal rod should be introduced carefully into the re-
entrant tube of the cell until the ice mantle is seen to rotate once again.

Page 10 of 10 WTPC B12 & B8 –Issue 8 (07/20)
PREPARATION OF B12 TYPE WTP CELLS USING THE ISOTECH
MODEL 452 ICE MANTLE MAKER
The Model 452 Ice Mantle Maker is supplied with an Ice Bridge Prevention Collar that is manufactured to the
specific size and design to accommodate the customers WTP cell.
The Model 452 isa dedicated piece ofequipment designed specifically forthe efficient creation of ice mantles.
A procedure for the use of this equipment is detailed in the manual for the Model 452, contact Isotech for
details.
General Note: The accuracy with which the cell may be used to check a thermometers calibration may, in
practice, be limited by the extent of its immersion in the cell or by the self-heating of the thermometer. The
magnitude of these effects may be checked by;
(i) reducing the immersion depth
(ii) making measurements at two currents through the thermometer