Page 66 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Be st Practice 2 .5 Pump Best Practices

Fig 2.4.9 Dual volute casing form
Fig 2.4.10 Volute radial reaction forces versus capacity

Best
Best
Best Practice 2.5Practice 2.5Practice 2.5
Double suction pump optimum reliability is achieved by: Impeller cavitation
Having minimum 3 pipe diameter straight pipe into the suction Pump seizure e at wear rings
Suction piping routed perpendicular to the pump centerline Shaft breakage
Keeping suction specific speed below 10,000 (US customary units) Thrust bearing failure
Seal failure

Lessons Learned
Double suction pumps have the greatest reliability prob- Benchmarks
This best practice has been used since the mid-1980s during the pump
lems of all centrifugal pump types, and require special at-
selection and model review phases for all double suction pumps. Prior
tention during the selection process.
to that time, all of the reliability issues noted in the lessons learned
Failure to follow the double suction pump best practices noted
section above were experienced, and many pumps were classified as
above has resulted in the following field reliability issues and MTBFs
“bad actors” (MTBFs below 12 months).
less than 12 months:

B.P. 2.5. Supporting Material

Piping

Piping accounts for the connection of the machinery to the
environment surrounding the equipment. Improper piping as-
sembly, like improper foundation installation, has resulted in
reduced rotating equipment reliability.

General practices

Figure 2.5.1 presents piping considerations that will result in
proper installation of equipment of high reliability.
Piping must always be floated to the machine and NOT first Fig 2.5.1 Piping considerations
mounted on the machine. A machine is definitely not a pipe
support. During construction, observe that piping is first mounted In bolting piping to machinery, lock pins on springs or pipe
to vessels in pipe racks, and then e and only then e floated to the supports must be kept in place until the system is filled with
machine. Any other procedure is totally unacceptable. liquid or gas, since they are designed to support the piping

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