Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations TugboatEng on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
solar compressor tie bar
- Thread starter jadow
- Start date
I thought it was just me with tie bar problems - comes as a surprise to know there are others out there. What makes you think your tie-bars are loose? I have 2 types of compressor - the HP unit rotors are relatively short and problem free but the LP units are quite long and the problems I have are as follows:
a) After a hot stop (trip) we need to restart the unit immiediately or the rotor 'hogs' and we face a minimum 2 hours wait before we can restart it (otherwise it goes out on high vibration as it goes through the critical speed)
b) The measured critical speed is higher on cold start than on hot shutdown suggesting a reduction in stiffness when warm: my thinking is that the tie rod heats up and expands causing loss of rotor stiffness - the hot and cold critical speed values are repeatable so there appears to be no ongoing deterioration in rotor integrity.
c) It doesn't help the the LPC is running close to its 2nd critical speed (Solar are in denial about this) so its really senstive to small changes in balance due to minor fouling and regular washing/trim balancing is needed - I would go as far to say that our LPC machines are of poor design, not really fit for purpose and virtually unmaintainable.
We have had one of the LP tie bars replaced by one with a new material (INCO based) allowing the pre-stretch (rotor stiffness) to be greatly increased - this increases the critical speed values, but does not change the difference between hot and cold values or solve any problems we have.
a) After a hot stop (trip) we need to restart the unit immiediately or the rotor 'hogs' and we face a minimum 2 hours wait before we can restart it (otherwise it goes out on high vibration as it goes through the critical speed)
b) The measured critical speed is higher on cold start than on hot shutdown suggesting a reduction in stiffness when warm: my thinking is that the tie rod heats up and expands causing loss of rotor stiffness - the hot and cold critical speed values are repeatable so there appears to be no ongoing deterioration in rotor integrity.
c) It doesn't help the the LPC is running close to its 2nd critical speed (Solar are in denial about this) so its really senstive to small changes in balance due to minor fouling and regular washing/trim balancing is needed - I would go as far to say that our LPC machines are of poor design, not really fit for purpose and virtually unmaintainable.
We have had one of the LP tie bars replaced by one with a new material (INCO based) allowing the pre-stretch (rotor stiffness) to be greatly increased - this increases the critical speed values, but does not change the difference between hot and cold values or solve any problems we have.
- Thread starter
- #3
Many thanks for the response and useful information.
We have a vibration issue that is not consistent and we thought this is possibly associated with a loose tie-bar. Was it Solar who supplied the replacement tie-bar (INCO based). Also please advise the LP compressor model No. and number of impellers you have in in this casing.
We have a vibration issue that is not consistent and we thought this is possibly associated with a loose tie-bar. Was it Solar who supplied the replacement tie-bar (INCO based). Also please advise the LP compressor model No. and number of impellers you have in in this casing.
- Status
Similar threads
