Rangkuman Diskusi Mailing List Migas Indonesia ini membahas tentang ASTM standar utk Oil Analysis – Rotating Bomb Oxidation Test (RBOT). Pertanyaan : YudaTomo

Mohon pencerahan kalau ada yg punya ASTM standar utk Oil Analysis – Rotating
Bomb Oxidation Test (RBOT). Kami ada rencana develop analisa utk melengkapi
Turbine Oil Analysis di Lab kami.

Tanggapan 1 : Anas Rosyadi

Pak Yuda,
Ini ada sedikit informasi ttg RBOT (ASTM D2272) dari noria.

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Q & A: Selecting A New Turbine Oil

"We are currently selecting a new turbine oil for our steam turbine. Is
the RPVOT (a.k.a. RBOT, ASTM D2272) a good indication of the relative ability
of two different oils to resist oxidation?"

This is a common misconception regarding the RPVOT test. The RPVOT, or Rotating
Pressure Vessel Oxidation Test, works by stressing the oil in an oxidating environment
that includes heat, water, copper catalyst, oxygen, pressure and agitation.
The test measures the length of time the oil can resist these stressing conditions
before the break point is reached and the oil degrades (oxidizes). This is influenced
by the quantity and type of antioxidants, the presence of natural inhibitors
in the base oil, and the resilience of the base oil to oxidation.

However, because the actual conditions a turbine oil experiences in application
may be considerably different than those present in the RPVOT test, there may
not be good correlation between RPVOT values and in-service oxidative life.
For example, one oil may have an RPVOT value of 1000 minutes, while another
oil may have an RPVOT value of only 700 minutes.

However, depending on actual stressing conditions and formulation factors,
the oil that starts with the lower RPVOT number may oxidize at a slower rate
and hence be more oxidatively stable than an oil with an initially higher RPVOT
value. In other words, formulation factors (base oil and additives) respond
differently to different in-service stressing conditions. In this case, the
oil with the lower new oil RPVOT value may be a better choice for long-term
resistance to oxidation. With that said, for turbine oils it is generally not
advisable to select lubricants with RPVOTs below 600 minutes, and test values
above 1000 minutes are generally considered out of the range of test sensitivity.

It should be also noted that RPVOT is an excellent test for measuring the degree
of oxidative degradation (for example, additive depletion) for in-service turbine
oils, by comparing the in- service oil RPVOT number to a new oil baseline.

LUBRICATION LITERATURE

Book Bits: Turbine Fluid Maintenance

From "Turbine Lubrication in the 21st Century"

As with existing turbine oils it is necessary to adequately maintain phosphates
in order to ensure efficient operation of the system and an acceptable fluid
life. The parameters that are of most concern are the increase in acidity, water
content and particulate contamination level.

When triaryl phosphates degrade, the most common result is an increase in acidity
with little effect on viscosity change. Consequently, this latter property is
not one that requires regular attention. Water and acidity, however, need monitoring.
To date there are no specifications for used fire-resistant turbine lubricants
but there is a tendency to adopt the limits already in existence for phosphate
esters when used as turbine control fluids, i.e. a maximum acidity of 0.2-0.3
mgKOH/g.

Semoga bisa membantu.