[Descripción General|Especificaciones Detalladas|Desaladoras de Crudo]
Petróleo, Gas y Petroquímica
Homogeneizado de Crudos
Custody Transfer Mixer
The Custody Transfer mixer for petroleum products
has become the standard in the industry. The
"CT" employs an integrated, patented
design to provide the ultimate in mixing. Installed
upstream of the sampling point in a petroleum
product transfer line, this unique synergistic
mixer assures that the bottom sediment and water
is thoroughly dispersed throughout the product
stream for accurate sampling.
Over 8,000 CT Mixers installed to date. Ranging
from 1" to 48" diameter.
KOMAX CUSTODY TRANSFER STATIC MIXER
In 1984 Komax Systems was approached
by the chief engineer of the Chevron Pipeline
Company with a problem. Chevron knew it was
losing millions of dollars each month due to
the failure of its crude oil sampling techniques
to properly account for the water content of
oil being loaded or unloaded from tankers and
during oil transfer between companies. Chevron
wanted to know, “Could Komax develop a
static mixer design to properly mix crude oil
and the bottom water for more accurate sampling?”
Per API recommendations most
pipeline companies installed a vertical loop
in the transfer pipe with a sampling probe on
the down side of the loop. The loop was supposed
to mix the oil and water so that readings from
the sampling probe would accurately reflect
the true water content and allow a proper correction
to be made to the final invoice for the crude
transferred. Chevron and other pipeline companies
found they were paying for a lot of water because
the vertical loop was not a good mixer. Without
good mixing the sampling probe cannot grab accurate
Komax started a research program
monitored by Chevron who supplied barrels of
clear mineral oil to Komax for test work. Komax
built a scale model in two inch diameter glass
piping of a typical CT loop and pipe run. Dyed
water was metered and injected into the mineral
oil flow to simulate bottom water. This allowed
us to study what really happens to BS&W
as it reaches and passes through a “mixing”
loop and other static mixer designs prior to
the sampling point.
Experiments were conducted
using mineral oil covering a range of viscosity’s
to represent variations in crude oil properties
and at pipeline velocities ranging from 1.0
to 10 feet per second. Static mixers from several
companies were tested. A variety of the Komax
static mixer designs were tested modified and
retested; Wires 0.030” in diameter were
welded to the downstream end of the static mixer.
This allowed photographic study of the exit
flow to determine water droplet diameter and
low and high velocities. Pressure drop was measured
for each design.
These lab experiments occupied
a period of eight months. During this test period
over sixty petroleum engineers from most of
the major companies visited Komax to view this
operating model. They could see how the pipe
loop and different static mixers mixed.
From our testing we developed
the design of the low pressure drop CT mixer.
There are two very key points in the Komax design.
The first mixing element is off set at a 30
degree angle. This allows the bottom static
mixer element ear to act as a dam forcing water
or BS&W off the bottom of the pipeline up
into the mixing zone. The back mixing inside
the Komax static mixer produces very small and
evenly spaced water droplets across the pipe
diameter. On the discharge end of the CT mixer
we incorporated an anti-spin fin to cancel the
rotation around the axis of the flow. This prevents
the 10% denser water from centrifuging out and
coalescing on the pipe wall before a sample
is grabbed. This centrifuging from the spin
in the first up flow elbow is causing one of
the mixing problems in the vertical pipe loop.
Photos of mixing are on the back page of our
Custody Transfer Bulletin 104.
Over the years the success
of the Komax CT static mixer alerted other manufacturers
to enter this market. They did this with little
or no testing. Purchases of static mixers for
CT applications were made on purely price basis.
This is understandable for externally all static
mixers look the same, a flanged pipe section
with a sample port down stream. However, this
led to very costly accounting errors for several
major oil companies. Also to Komax chagrin the
statement “I tried a “static mixer”
and it didn’t perform that well”.
KOMAX CUSTODY TRANSFER MIXERS
TYPICAL PAYBACK IS IN HOURS
Off loading a crude oil tanker of 250,000 bbls.
Off loading pipe lines: Two 14 inch diameter
Custody Transfer Mixers one 14 inch in each
Flow rate per mixer: 225,000 gph. (5357 bbls/hr)
Pipeline velocity: 9.75 ft/sec. (3 m/s) Tanker
off loading time: 23.3 hours ( two lines)
The Komax CT mixer finds just 0.5% additional
BS&W over other inline mixing devices.
250,000 bbls X $ 40.00 per
barrel = $ 10,000,000.
$10,000,000 X 0.5% = $ 50,000. Cost of the 0.5%
Payback time for two 14" CT mixer = 6 hours
Off loading four ships a month = $2,400,000
a year. (double at 1%)
Over fifteen years ago Komax Systems developed
the CT Static mixer design at the request of
the chief engineer of Chevron Pipeline Company.
Standard off the shelf static mixers were not
producing repeatable and accurate samples. Vertical
pipe loops, as recommended by the API for mixing,
were producing even greater errors.
Pipeline engineers from Shell,
Chevron, Exxon and other pipeline companies
have reported back to Komax Systems that they
find typically 1% and higher of additional BS&W
over other mixers or loops installed before
the sampling probe. To prove mixing the pipeline
engineers would inject a known quantity of additional
water during a crude oil transfer to see if
the sampling was accurate and repeatable. The
results of these infield tests is why Komax
Systems has sold over 8000 CT mixers world wide
from ¾ of an inch to 48 inches in diameter.
Even on small diameter pipelines operating twenty
four hours a day, the cost savings per year
is in six figures.
When buying or selling crude
oil your company cannot afford not to install
a Komax CT mixer before sampling. As we all
know $40 per barrel has come and gone.
Komax Custody Transfer or CT mixer are installed
upstream of the sampling point in a crude oil
transfer line. They assure that the bottom sediment
and water – B, S & W – is thoroughly
dispersed throughout the crude oil stream. An
even water droplet size and distribution occurs
over a wide flow range. This means that the
automatic sampler takes a truly representative
Komax CT mixers are installed
in petroleum product transfer lines such as
ship and tank truck terminals or refinery transfers
in combination with a LACT unit. CT mixers are
supplied with weld neck flanges or ends prepared
for welding. For ease of installation Komax
CT mixers are supplied complete with two inch
flanged port for the automatic sampler connection.
Dimensions and design graphs for all CT mixers
are listed below.
Special features provide
The Komax CT mixer was specially
designed to solve conventional custody transfer
mixing problems. The CT mixer may be installed
in a horizontal or vertical pipeline. In a horizontal
line, the first mixing element is set 30 degrees
off the centerline so the bottom mixing element
ear acts as a ramp, forcing the bottom water
up into the crude (see Figures 1 and 2). The
internal vortices or back-mixing created by
the Komax mixing elements also rotate the blend
backwards from wall to eliminates any wall streaming
and produces a very uniform distribution and
droplet size of the water in the crude.
A very important feature of
the Komax CT mixer is the addition of a special,
last mixing element that cancels all of the
axial rotation of the flow downstream of the
mixer. Violent rotation of the stream would
cause the centrifuging problem (barber poling)
of the water to re-occur. The automatic sampler
is located two to four pipe diameters downstream
of the mixer. The resulting samples provide
highly reliable net crude oil measurements.
CT Mixer without side sampler
CHEVRON SHIP LOADING TERMINAL
MORRO BAY CALIFORNIA.
THE TWO 20" KOMAX CT- MIXERS SAVED 3 MILLION
DOLLARS THE VERY FIRST YEAR DUE TO IMPROVED
MIXING BEFORE SAMPLING. EXPECTED MIXER LIFE
- 20 YEARS.
Static mixer improves desalting efficiency
An in-line static mixer has
increased salt removal from crude oil at a large
West Coast refinery, says the mixer supplier,
Komax Systems Inc.
The mixer was installed at
a 150,000 bid crude distillation unit’s
Crude at this refinery is a
mixture of local production and imports from
Indonesia and Alaska.
In the past, the refiner used
a typical globe-type mix valve to mix fresh
water with crude at the desalters. The crude
is heated to 300 degrees F., mixed with 5% fresh
water, and then fed to desalters.
Chemical and electrostatic
treatment is used in the desalters to remove
salt and water from the crude.
Pressure drop in the mix valve
was typically set at 10 psi. However, when the
processing of heavy (14 degree API) naphthenic
crudes was attempted, the oil/water mixture
formed a stable emulsion in the desalter. This
prevented economic processing of this low cost,
domestic crude. Several problem areas were identified
which could contribute to stabilizing emulsions.
One was the high shear-rate mixing found in
the mix valve.
The crude oil and water are
then simultaneously mixed though two-by-two
division, cross-current mixing, and back-mixing,
which improves turbulence and increases mixing
efficiency without requiring high fluid shear
The modified desalter system
has operated well on 14" and 22" API
naphthenic crudes, with less that 5% oil in
the effluent water.
As an unexpected bonus, salt
removal also increased as a result of using
the static mixer (Table 1). Depending on the
type of crude oil, the refiner has been able
to remove between 5% and 10% more salt than
by the mix valve method. With less salt carried
over out of desalter, less corrosive HCI will
be generated in the crude unit furnaces. This
will require less ammonia to neutralize the
atmospheric column overhead stream.
At the same time, the mixer
has helped reduce emulsions formed by too much
pressure drop created by the mix valve. With
less oil carry under, less fuel is consumed
from having to reheat recycled oil up to 300
degree F before it re-enters the crude unit.
In addition, the new mixer
has a better turndown ratio than the mix valve.
The Komax unit has performed satisfactorily
at rates as low as 35% of its design capacity.
Previous types of static mixers
were unable to operate effectively at these
Also, pressure drop due to
the mixing device was decreased for 10 psi to
1.5 psi. Depending on the particular situation
this could have energy conservation or through
The refiner calculates that
the mixer will pay for itself in its first year
of operation with combined savings of $4,000/year
in lower power consumption and chemical costs
and $1,000/year in lower fuel costs.
Average desalter performance *
in, † Salt
out, † %
90,000 b/d 22º API Crude 42 4.4 89%
14º API Crude § ----- ----- -----
90,000 b/d 22º API Crude 41 1.6 96%
45,000 b/d 14º Crude 43 º 97%
* Desalters, mix valve, and
static mixer all designed for full design crude
unit feed rate of 150 MBPD.
† Pounds NaCl per 1000 bbl crude.
§ Crude Unit did not run 14º crude
before desalter modifications, which included
the static mixer, because stable emulsions were
The in-line static mixer is
contained within the flanged section of the