solve the problems. More recently,
Neuman & Esser bought the rights to
service Demag compressors and the
German company made some recommendations, such as implementing
temperature control of the cooling
water, use of nitrogen as packing
buffer gas, improvement of gas treatment to lower the amount of condensate and solid entrainment. These reciprocating compressors, however, did
not have any devices allowing either
predictive maintenance or early failure
warning of the running parts.
In 2005, Prognost presented its
Prognost-NT monitoring system expressly tailored for reciprocating compressor diagnostics. At São Mateus do
Sul, the equipment operators had no
experience in monitoring this type of
machine. They only had a monitoring
system installed on an old 9. 4 hp ( 7
MW) Sulzer axial compressor installed
in 1984, which allowed them to perform predictive maintenance.
Prognost specialists were able to explain to Lampert and Chaves the differences between a monitoring system installed on turbomachinery and one
designed for reciprocating machines.
They stressed the importance of continuously monitoring the machine and
process conditions. This activity helped
the machine failure diagnosis and/or
operation out of the machine operating
limits, giving support to the decision to
intervene, leading and helping the
problem analysis and, mainly providing machinery protection.
In the next step, Prognost formulated the specific monitoring objectives
for the client. Finally, the whole system
was purchased by Petrobras. ;
Cylinder side of one of the four-throw compressors compressing hydrogen sulfide in the Petrobras
oil shale plant. These compressors were retrofitted with Prognost N T monitoring systems.
section for heating the oil shale feed
as a supplementary heat source. The
drawback of this process is that the
potential heat of fixed carbon contained in the shale coke is not used.
The compressor duty is to compress
the excess gas derived from pyrolysis
extraction from shale.
The plant is equipped with two
Mannesmann Demag compressors, C-
24101 A/B type 23B4G3/17. These are
four-throw, balanced-opposed, reciprocating compressors with lubricated
cylinders. The compressors are driven
by 1408 hp (1050 kW) electric motors
at a speed of 504 rpm.
The shale gas (hydrogen sulfide) is
compressed in three stages. Between
stages, extraction lines take out several condensates: fuel gas, a small
percentage of naphtha, gas treatment
with soda and DEA (H2S extraction)
and, at the end of the third stage, the
LPG at about 230 psi (1550 kPa).
The compressor service is very demanding because the shale gas has
high humidity and entrains many
solid particles in suspension that are
the cause of the majority of the problems and accidents with these machines. The main problems are caused
by the deterioration of the sealing elements (packing leakages) and consequent H2S attack on the internal compressor parts. These leakages led to
possible condensate ingestion, and
probable frequent condensate fog ingestion, as well as capacity loss because of valve obstruction. A few
years after the installation of the machines, Mannesmann Demag stopped
manufacturing reciprocating compressors, and Petrosix had no help to
