Description
The Automatic Density Control System is designed for the Serva
High Energy Recirculating Mixing system and uses the latest Computer
Control Technology.
The ACM® -III interacts with the cement-metering valve that controls
the dry bulk cement. The mixing process is controlled by an industrial
grade programmable controller that is equipped with an operator interface
control panel. This programmable controller controls the cement metering
valve position. The control software analyzes the measured mix water
rate, slurry density and the desired slurry design. The “go-to” control
algorithm calculates the required cement to match the measured water
to meet the required slurry density. The mix water flow meter measures
the water rate that is flowing into the mixer, and the control algorithm
calculates the required percent opening for the cement metering valve
to meet desired density.
A PID loop dials-in the fine setting of the metering valve as it reads
the signal from the densitometer. The control algorithm will respond
to three possible changes during the job. Changes in the throughput
rate, which is reflected in changes in the mix water rate; changes
in set point density (operators can thicken the slurry at the tail
end of the slurry mix or reduce the set point due to measured air entrainment);
and changes in cement delivery due to irregular and/or declining cement
delivery from the bulk supply.
The system also has a training simulator
mode that lets the operator run cementing jobs without having bulk
cement supplied to the unit. The operator can improve his skills for
controlling density in manual or automatic mode with no material cost
or cleanup. The programmable controller, while in simulation mode,
provides system function verifications to test all lines, cables, flow
meter, hydraulic system, feed back system and the programmable controller
itself.
The cement flow rate is controlled and adjusted via aproportional
solenoid valve, which is automatically controlled by the computer.
The slurry densitometer located on the circulating piping system detects
the actual density and feeds the measured value back to the computer.
The 3” water flow meter mounted on the mix water piping system measures
the water flow rate and sends the measured value to the computer. With
the water rate and the desired density, slurry design and measured
density, the computer calculates the required cement valve position.
A command signal is sent to the hydraulic actuating system to adjust
the opening of the bulk cement-metering valve and thus controls the
slurry density to the set range. The auto mixing system has interfaces
for triplex discharge pressure and rate, bulk delivery ability and
discharge rate. It displays and records the slurry density, discharge
rate, and pressure bulk deliverability.
Key Features
1. GO-TO and PID Program
The “Go-To” program and the “PID” program together precisely control
the slurry density. The “Go-To” feature adjusts the cement metering value
before a density error occurs. When the job requires a change to the
water flow rate, the computer will automatically adjust the opening of
the cement metering valve. The “Go-To” feature will normally adjust the
cement metering to the correct position. If the density is still off
a little, the PID control algorithm takes over to make final adjustments.
The PID algorithm uses density error (set desired value less measured
value) to correct density errors that the “Go-To” system did not take
care of. Thus, the PID system is a secondary control system that makes
the final trim in the control values.
2. Simulator Module
The ACM® System is configured with a simulator program. In the simulating
mode the operator can implement the system self-check without bulk
cement before starting the cement job. The program is also very helpful
for training operators.
3. Non-radioactive Source Densitometer
The non-radioactive source densitometer responses very quickly and
works reliably. It requires no calibration.
4. Manual/Auto Mode Switch
The system shifted back and forth between manual and automatic mode
whenever the operator wishes.The job can be started and stopped in
either manual and auto mode.
5. American Standard Industrial Computer
The American standard industrial computer is oftop shock resistance.
It is applicable to all different kinds of oilfield job services. Its
operation temperature ranges from -29ºC to +49ºC (-20ºF ~120ºF). The
computer is equipped with 6” color screen. Only one screen is used for
running the job but other screens are used for prejob setup and calibration.
Note: The system also has features to ensure proper operation in cold
weather. The ACM® System is also configured to receive triplex pump discharge
rate and pressure measurements for recording. The triplex discharge pressure
and rate sensors are available.
Components & Fundamental Operating Principles
Operator interface panel
Computer with I/O interface
Electro-hydraulic control valve (drives the cement metering valve)
Cement metering valve feedback transducer
Mix water flow meter
Densitometer
Triplex pump rate sensor (optional)
Triplex pump pressure sensor (optional)
Automatic
Density Control System ACM-III