I am upgrading instruments on a 30 years old 5000HP Motor driven gas compressor (I kid you not). As part of the upgrade, I have suggested redundancy of thrust probes A & B on the Compressor Outboard thrust pad and even added further additional monitoring points on the radial axis. (Including a new installation of dual redundant thrust probes on the helical gearbox)

However, the Operations dept require the single radials to be redundant with additional probes in an X-Y axis.

I was hoping for a degree of flexibility here with the age of the machine in question and also the fact that the radials are easy to get at (Maintenance point of view) where a high vibration would trip the machine and a failed probe (Eg. Low/ no vibration) would Alarm at the Vibration Controller & Workstation alerting maintenance to change it out.

Obviously I do not wish to impede the safety & protection of the machinery with my suggestions but after 30 years of the current installation and limited budget I am trying to be practical.

Therefore, is API recommendations mandatory? Are there any Specs that are mandatory or is it all on a Clients whim? He'll be wanting to know the speed next!

Hope you can assist
Thanks in advance
Gray

 

Responding to Gray's query:

Here is what worked for me in some cases.

If Probabilistic Risk Analysis, PRA, shows that there is a consequential increase in thrust pad temperature, then, it can replace the redundant displacement probe!

Regards,
Phil Corso, PE
Boca Raton, FL
[[email protected]] ([email protected]) {[email protected]}

 

Gray,

API 670 is not mandated by law. It is intended to be a guideline for good practice and machinery protection. It is most often used as a guideline when purchasing new equipment to assure that the equipment being quoted meets the same specification without having to write the specification.

There may also be instances where your equipment insurer may insist that you follow best practices, which API 670 falls under.

There are a number of reasons to use redundant (X-Y) probes as well as a number of reasons not to use them. It really depends on the criticality of the machine.

Byron Broussard
[email protected]