How to Protect Machinery From Self Destruction: Online Versus Offline Protection

In modern industries of Petroleum Refining, Chemical Processing, and Powerplants, typically the larger rotating machinery of 2000 HP and above are equipped with online vibration monitoring and well protected. The smaller equipment are only protected by a monthly or weekly manual vibration detection route with handheld devices.

However some machinery such as Hydrocarbon pumps can incur sudden destructive failure events that will not be noticed in time by operators. For example bearings can fail suddenly, leading to mechanical seal breakage and sudden ignition fires even with M-Seal leak detection. So what is the solution:

1- Install low cost online vibration protection systems optimised for minimum cost. The sensor is an Accelerometer or Velometer [Bently]. You can choose hardwired cable systems routing signals to central control room, or use Wireless systems if company policy allows that.

2- In year 2001 we developed a detail system architecture design for a plantwide low cost online monitoring system, and had a contractor install such a system to protect a Red Sea Refineries' pumps [all below 2000 HP] that were non-instrumented and were causing many fires. The offline monthly vibration route did little to protect them from fire incidents. Notice in Fig-2, the sudden rise in vibration at a short time span.

3- We installed a Bently Nevada Trendmaster system that used local mounted Bently Nevada Model-1900 low cost Field mounted heavy duty rating monitors 4-channel type accepting accelerometers input plus temperature if needed, and a hard wired Fieldbus Loop system which eliminates the need for expensive direct wiring of each machine to the control room. The online protection extended to about 250 Hydrocarbon pumps. From that year onward, the project prevented all pump related fires by early shutdown of equipment, both ball bearing and hydrodynamic bearing types. It is still functioning. There are other equally suitable protection and monitoring systems from Emerson, Prognost, and others.

4- These days you have the option of hard wired Fieldbus loop systems as in the Trendmaster, or Wireless transducer transmission systems using Trendmaster or other manufacturer systems. The signal from wireless systems is sent to the central control room using multiple field recievers which then transmit back to the central control room receiver. That receiver then interfaces with a central monitor collecting data which has shutdown outputs of 4-20ma, and it stores data in a PC or a main process plant DCS computer. Its your choice and of course if looking at more than twenty machines, the wireless systems are very much lower in final installed cost.

5- First recognise which machinery you want protected: I advise online protection for all hydrocarbon pumps and gas compressors of 100 HP and above. Next if funds are available, extend protection to other plant high criticality machines such as Process fans, Boiler FD fans and Feedwater pumps which are not neccesarily fire risk related.

6- Since we are primarily applying safety and fire prevention instrumented protection, look at reducing total project costs by installing vibration transducers on the driven machine only; not necessarily the driver as it is not as critical for fire safety. Its up to you to decide this issue as lowering the number of installed accelerometers, allows extending the project to a large number of machinery. A total of three transducers are required on driven machine: One Accelerometer or Velometer in DE bearing housing horizontal. Same on NDE bearing housing horizontal. Third one on NDE housing axial direction reading thrust.

7- Recommended Vibration Alarm and Shutdown Protection Settings in Velocity, RMS: Notice Fig-3. Settings: Alarm: 0.18 Inch/s RMS in range of 5 to 1500 Hz. Shutdown 0.25 inch/s RMS. If the normal pump vibration is rough, you can increase settings to Alarm 0.20 inch/s RMS and shutdown 0.28 inch/s RMS. Do not exceed these limits. When machines exceed the trip level, the central monitor uses its 4-20 ma output signals to interface with the central controls to send a relay signal to shutdown the driver whether it is motor driven or turbine driven.

In Conclusion

The protection system at the refinery has operated from year 2002 until 2023, 21 years without failure to function, with a very minimum cost of PM maintenance. Regarding project costs these will be recovered by preventing fires, and in fact the Insurance companies typically provide a discount based upon this protection system, so there are multiple paybacks. In addition the savings extend to the reduction of manual route manpower, and reduction of machinery damage repair costs. Suppliers of full systems include Bently Nevada, Prognost, and Emerson.

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1- https://www.dhirubhai.net/posts/abdulrahman-alkhowaiter-a7865318_pdm-when-to-move-from-walk-around-to-online-activity-7108355019875233792-ldG-?utm_source=share&utm_medium=member_desktop

2- https://www.dhirubhai.net/posts/abdulrahman-alkhowaiter-a7865318_protect-machines-from-self-destruction-online-activity-7108396473062502400-vWez?utm_source=share&utm_medium=member_desktop