Ulvac CRYO-U Series Instruction Manual page 22

8. Assembly and disassembly of refrigerator
The refrigerator contains high-pressure and high-pure helium gas. When disassembling
your refrigerator, please contact our Service Engineering Division or the nearest customer
support center for technical assistance.
If you will perform maintenance or disassembly of the refrigerator by yourself, take the
following special precautions for maintenance or disassembly of the refrigerator.
1. Exhaust helium gas completely from self-sealing couplings on both helium return and
supply flexible hoses by using the charging adapter.
2. Make sure that the helium gas pressure has fallen on 0 MPaG and then loosen the
bolts.
NOTE: Do not loosen all the fixed components such as bolts, plugs, and pressure
relief valve pointed by arrows in Figure 3 before discharging the helium gas.
Ignoring this note may cause severe injury or equipment damage by flying
components due to residual pressure.
Take the following cautions when assembling the refrigerator by yourself.
1. Tighten the bolts of each part in the diagonal sequentially.
2. Because the heavy load of the high-pressure helium gas is applied, torque management
for tightening the bolts up is important. As for cylinder bolts (M5×6pcs) used in the
refrigerators of R10 to R50 series, the required torque is 6.9N･m (70kgf･cm). On the
other hand, as for cylinder bolts (M6×6pcs) used in the refrigerators of R80 series, it is
11.6N･m (118kgf･cm).
3. Fill the refrigerator with the helium gas slowly confirming that there is no defect or
abnormality.
4. When adding the helium gas, please follow the all instructions described in "8.4
Cryopump Decontamination Procedures" in this manual.
S-10 ULVAC CRYOGENICS INCORPORATED