Engineering manual - SAB 193-233-283 S A-frame (including ATEX)
116/175
008831 en 2022.02
•
Lower speed of sound enables the gas to resonate in smaller volumes
•
Lower specific volume (larger density) increases the amplitude (severity) of the
vibration.
Group I
Warning in COMP1 – Refrigerants in this group have the highest risk of requiring many and
significant design changes to avoid vibration damage of the unit. They are therefore NOT rec-
ommended for VSD operating units, and it must be avoided to sell VSD units with refrigerants
in this group.
Group II
Refrigerants in this group have some risk of requiring some design changes or preventive sup-
ports - this means that extra lead time and/or additional engineering hours (cost) should be ex-
pected when combining refrigerants in this group with VSD. On-site remediation of critical
vibrations may be required, including:
•
Skip of speed ranges with high vibration levels as described in the VibraGuard manual.
•
Addition of pipe supports and structural reinforcement. This may include on-site
welding.
Group III
This group is considered as the design reference point, and there is low risk of vibration issues.
Any issues that do occur may require skip of speed ranges but will usually not require signifi-
cant alterations/repairs. Apart from this, no additional consideration is needed with regard to vi-
bration issues when offering VSD in combination with refrigerants in this group.
Group IV
No known vibration-related issues exist with refrigerants in this group combined with VSD.
Note that critical speeds and other issues related to structure may still be the cause of vibration
problems, but such issues will be unrelated to the specific refrigerant.