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 (CO
2
)
The critical point dryer requires a cylinder of liquid CO
2
fitted 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 CO
2
cylinder. 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 CO
2
tank. 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 (CO
2
) 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 CO
2
can 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 CO
2
exhaust 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.
