SP Scientific Freezemobile Series, Operator'S Manual, Page: 49 / 54

VirTis Freezemobile 25L and 35L Appendix A: Troubleshooting
Rev 005, 02/12 39
© SP Scientific 2012
2. Testing with Alcohol or Acetone
If the leak cannot be found with soapy water, test again using alcohol or
acetone. Helium
3
leak testing is also an option.
Note: These tests should only be performed as a last resort. .
a. This type of leak testing is performed externally. Thus, insulation must be
carefully removed to reveal the area to be tested.
Install a full range, atmosphere to high vacuum, Pirani-type electric
vacuum gage sensor as close to the vacuum pump as possible.
With the gage in place, the vacuum should be at its lowest possible level.
Spray the solvent on the suspected leak areas.
If there is a leak, the solvent will enter the hole and be drawn directly to
the vacuum pump. With the Priani sensor mounted near the pump, the
solvent will cause a deflection in the vacuum reading indicating a leak.
Sometimes the leak can be temporarily sealed with water or grease to
confirm that a leak is present. Using alcohol, which invariably has some
water content, this freeze and seal will happen often. The sudden drop in
vacuum is confirmation that the leak has been pinpointed
Permanent repairs should be made once the leak is located.
Product Melting
The most common reason for product melting is poor vacuum. Adequate vacuum is
required to keep products in a frozen state. Check for a vacuum leak or possible
restrictions in the vacuum hose as previously described.
If the unit is functioning properly but the product is still melting, the product’s freezing
point (eutectic temperature) may be too low to remain in a frozen state. Retest using a
water sample to determine if a mechanical or product-related problem exists.
3
Helium is used in the same fashion as alcohol and acetone to find a leak. A helium leak tester is very expensive but it is
capable of finding very small leaks.