SABROE SAB 193 S, Инструкция по эксплуатации, Страница: 115 / 177

Engineering manual - SAB 193-233-283 S A-frame (including ATEX)
008831 en 2022.02
115/175
Installation instructions
As the loads on the supporting surfaces of the unit vary, different vibration dampers may be
used on the same unit. Consequently, it is important to position them in the right places com-
plying with the order specific drawing supplied with the unit.
To check the deflection of the vibration dampers while loaded, measure "A", Fig. 80, while the
unit is still suspended in the crane. After the unit has been installed, measure "A" once more.
The difference (deflection)
must be between 3 and 5 mm for all vibration dampers.
If this is not the case, insert liner plates under the vibration dampers until the above deflection
has been obtained.
As vibration dampers for marine use should also dampen vibrations coming from the founda-
tion caused by the main and auxiliary engine, vibration dampers are selected on the basis of
an information table and the mentioned descriptions. Send the information table, including ap-
pendices, to your local Johnson Controls representative, who will then select the appropriate
dampers.
7.24 VSD equipment
Equipment running variable speed (VSD) is more likely to encounter resonance causing critical
vibrations. During selection, an assessment of equipment feasibility for variable speed must be
carried out, based on the risk chart below. The table values are based on reference tempera-
tures of 35°C of condensation pressure and discharge temperatures at 75°C (60°C for HFCs).
Every refrigerant belongs to either group I, II, III or IV. Which group is determined by the most
severe property, whether this is density or the speed of sound in the refrigerant at operating
conditions. It is also a prerequisite that the compressor is running close to ideal VI as any over-
or under-compression will increase vibrations significantly.
To ensure that vibrations are handled safely, all Sabroe VSD equipment must be checked dur-
ing commissioning using our VibraGuard tool and procedure, or equivalent. It is the commis-
sioning engineer’s responsibility to document the equivalence.
Group
Specific volume
[m3/kg]
Average speed of
sound in gas
[m/s]
Examples of refrigerants
usually in the group
I
< 0.0167 < 175
R507, R404A, R410A
II
< 0.0333 < 300
R134A, R407(A+C+F), R22, CO
2
(R744), R32, MR gas Note 1
III
< 0.3333
< 500
(some exceptions)
Ammonia (R717), Propane (R290)
IV
> 0.3333 > 500
Steam (R718)
Note 1: Even though MR gas is typically in group II, be aware that the possibility of performing
hot work (welding) on site may be limited due to flammability. In such case, variable speed ap-
plications must be avoided.