IMI STI RTQH Series, Instruction Manual

Page: 14 / 42

_____________________________________________________________________________________
STI S.r.l.
– Via Dei Caravaggi 15, 24040 Levate (BG) – ITALY www.imi-critical.com
Manual 5400, rev. 05 02/2018
– RTQHS
10
Fig. 3
– Assembling of the actuator on the valve
Important To guarantee the correct transmission of torque from the actuator to valve
stem without phenomena of slip it is important to remove any trace of oil
and/or grease from the mating surfaces of valve and actuator or bracket and
tighten the nuts fixing the bolts with the torque specified into the following
Table 1
Table 1
Threading Tightening torque (Nm) Threading Tightening torque (Nm)
M8 20 M24 550
M10 40 M27 800
M12 70 M30 1200
M14 110 M33 1400
M16 150 M36 1800
M20 300
The torque values in Table 1 have been calculated considering the materials ASTM A320 grade L7/ASTM
A193 grade B7 for screws or tie rods and ASTM A194 grade 4 for the nuts.
Alternative bolting permitted i.e. ASTM A193 B8M (or B8M3) for tie rods and ASTM A194 grade 8M for the
nuts, provided that yield strength of screws or tie rods is higher than 450 MPa.