Operation
and Control Engineering Services
Examples of jobs with operation and control problems:
Generally fans and pumps are controlled to satisfy either the volume flow rate or the pressure that is demanded by the system or process. The output of fans and pumps can be controlled by a number of devices or methods.
throttling by means of dampers (for fans) or valves (pumps)
variable speed
varying the pitch of fan blades on axial flow fans
varying the number of fans or pumps in operation
An understanding of the operating characteristics of the turbomachine and the system (ie. volume flow rate versus pressure drop) is required in order to properly select the control method and control strategy.
Design of Control Strategies for Fans and Pumps
The design of a control strategy is dependent on a number of factors.
Operating characteristics (volume flow rate versus pressure)of the turbomachine and the system it is connected to.
Device or method used to control the output of the turbomachine (ie. dampers/valves, variable speed or staging of multiple turbomachines)
Operating characteristics and interaction of multiple fans or pumps operating in parallel or series.
Startup and shutdown characteristics of single and multiple turbomachines.
Control to satisfy either the volume flow rate or the pressure that is demanded by the system or process.
FLOWCARE has a solid background in the performance characteristics of fans
and pumps including the effect of control devices. FLOWCARE can predict the
interaction of the turbomachine with an infinite number of potential system
characteristics and will combine this with the above factors in the design
of a control strategy.
Assessment of Operation and Control Problems
Typical symptoms that may be related to operation and control problems are listed as follows.
poor fan, system or process performance
poor control at low flow operating conditions
slow response to system changes resulting in cycling variations in flow or pressure
fan or pump operating at an unstable operating point (frequently the case for fans or pumps operating in parallel)
some form of electrical problem (ie. motor overload)
some form of mechanical failure (ie. cracking of ducts, piping or fan wheels)
In many cases it may not recognized that mechanical or electrical problems
are a direct consequence of the operation and control strategy. FLOWCARE
will define and evaluate the operation and control strategy in terms of the
performance characteristic and controllability of the fan or pump. A vital
component of the evaluation is field performance
testing to establish operating points, accuracy of control instrumentation,
system pressure drops and capacity of fan or
pump.
Assessment of Fan and Pump Sizing
Often, poor control is due to over or under sizing of fans or pumps.
Assess if the fan or pump is properly sized for the application.
Establish the turndown ratio required by the system or process
Evaluate the stability of the turbomachine over the full range of turndown.
Evaluate how effectively the control device will provide the turndown
required.
Selection and Application of Valves and Dampers
Select control valves or dampers and predict the operating characteristics.
Establish the effect that the control device has on the turbomachine
performance,
Evaluation of Variable Speed Control
Engineering evaluation of variable speed control compared to valve/damper control identifying the mechanical and energy implications on the fan/pump.
Assess if fan or pump is suitable for a conversion to variable speed control.
Determine acceleration and deceleration rates possible based on the speed
torque characteristics of the driver, turbomachine and the inertia of the
turbomachine
design of air system blowoffs to avoid turbomachine instability at low
flow conditions (ie. fan surge, rotating stall...)
selecting flow meters suitable for the fluid or gas handled
evaluating suitable locations in duct and piping systems for flow meters.
address temperature and pressure compensation
Examples of jobs with operation and control problems:
Steel Company - Power Boiler ID Fans - A72697
perceived by customer as a motor overload problem on boiler ID fan
electrical? Or fan?
problem related to,
Primary Metals - Fluid Bed Drier Fluidizing Fan - A37594, A45395
problem described by customer as fan impeller cracking (mechanical/structural)
investigated wheel natural frequencies and pressure pulsations
identified an operation and control problem related to,
Pulp and Paper - Boiler Fans - A49495, A50996
unable to attain air turn-down ratio of combustion air and flue gas recirculation (FGR) to meet low boiler loads.
FLOWCARE in conjunction with the boiler combustion expert assessed the sizing and controllability of the existing fans for operation at low boiler loads
compared damper control with variable speed control
developed control strategy accordingly
Steel - Reheat Furnace - A38294, A40494, A43095
operation and control problem due to oversized fan and requirement for high pressures at low flow operating conditions resulting in rotating stall and mechanical failures.
reduced furnace header pressure setpoint
designed a blow-off
improved flow measurement, aerodynamic stability and
energy
efficiency
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Contact: sales@flowcare.com
