Station capacity control · Optimal loadsharing · Minimize recycle flow
Control
On centrifugal and axial compressors, anti-surge control and capacity control can pull in opposite directions by design. Capacity control reduces speed or closes guide vanes to cut throughput when demand falls. Anti-surge control opens the recycle valve to keep flow above the surge limit. Left uncoordinated, falling demand can drive speed down and move the operating point toward surge. The anti-surge valve opens, recycled flow affects what the capacity controller sees, and the capacity controller can respond by demanding even less machine output. The result can be a station that sits in recycle longer than it needs to.
Innova Technologies engineers the two functions as one coordinated architecture for centrifugal and axial units. A capacity controller develops station demand from suction pressure, discharge pressure, throughput, or another defined process objective. Loadshare controllers convert that demand into a surge-margin target for each applicable compressor based on its available turndown range, so the units move proportionally toward their operating limits rather than allowing one machine to unload into recycle while another still has useful capacity.
A capacity control interlock breaks the unwanted interaction when an anti-surge valve begins to open. Instead of allowing continued speed reduction to deepen the event, the interlock blocks that response and transfers the station response to the appropriate recycle logic. For reciprocating and screw compressors, station capacity is managed through pressure control and machine-specific final control elements rather than through anti-surge margin.
The Problem
For centrifugal and axial compressors, recycle is not a fault condition. It is the correct response when flow approaches the surge limit. The question is how much recycle is actually necessary. Avoidable recycle can come from poor coordination between capacity and anti-surge control, unequal loading that pushes one machine toward its limit while another still has usable range, or a surge line that no longer reflects the conditions the compressor is operating under.
The technical case for station optimization is straightforward: share load more intelligently, reduce unnecessary recycle, limit avoidable operator intervention, and keep the available machines working efficiently across the station’s operating range. Adaptive surge detection can account for changing conditions on centrifugal and axial machines rather than relying only on a fixed commissioning curve. Loadshare allocation can then respond to the available turndown of each applicable unit as station demand changes.
The same station-level automation can coordinate sequencing and pressure response across other compressor types using their own control strategies. That gives the plant one operating objective without pretending every compressor responds to that objective the same way. A properly engineered station control layer can also support remote and unattended operation by automating capacity response, sequencing, load allocation, and protective interaction across the plant.
Capabilities
Click any capability to expand the full technical detail.
A station capacity controller develops total demand from suction pressure, discharge pressure, throughput, or a user-assigned process variable such as temperature or a downstream setpoint. Split-range output blocks and feedback selection logic prevent controller windup when an output saturates, and the active control response can change automatically as operating conditions change rather than relying on constant operator intervention.
Automatic sequencing brings units on and off line against station demand, with runup and rundown sequences, standby unit assignment, run-hour equalization, and permissive checking before each start. AUTO, MANUAL, and SAFE MANUAL modes provide different levels of operator control with bumpless transfer between modes. On centrifugal and axial units, SAFE MANUAL gives the operator manual control of the recycle valve while allowing the anti-surge controller to override the operator’s command when necessary to avoid surge.
For centrifugal and axial compressors, the loadshare controller converts station capacity demand into a surge-margin setpoint for each machine, scaled to that compressor’s available turndown range. As station demand falls, the applicable units reduce capacity proportionally toward a defined minimum just short of anti-surge valve action rather than allowing one machine to unload into recycle while another continues carrying substantially more load. Dissimilar centrifugal and axial machines can be handled according to their individual operating ranges.
The compressor control scheme is engineered together with the driver control, whether that is a gas turbine, an electric motor with variable speed drive, or a reciprocating engine. Speed modulation, guide vane positioning, valve throttling, and applicable driver limits are coordinated within the station strategy rather than treated as independent systems negotiating through a simple handshake.
For centrifugal and axial compressors, the capacity control interlock prevents unwanted coupling between anti-surge and capacity control. When an anti-surge valve begins to open, the interlock prevents the loadshare controller from continuing to command the response that is driving the machine toward surge. The station response is transferred to the appropriate recycle logic instead of allowing the two controllers to work against each other.
Real-time performance calculation locates applicable machines on their operating maps and tracks values such as polytropic head, efficiency, and distance to surge. Trending helps operations see changes in machine behavior and provides the station control layer with information it can use when allocating load across centrifugal and axial units. The goal is to use the available operating range effectively without compromising machine protection.
For centrifugal and axial compressors, surge detection can recalibrate the surge line in response to measured operating conditions rather than relying only on a fixed commissioning curve. This is especially important as machine and process conditions change over time. The anti-surge controller acts through the recycle or blow-off valve to keep the operating point above the surge limit, with valve response engineered around the protection requirements of the machine.
Reciprocating and screw compressors are coordinated against the same station suction and discharge pressure objectives as the rest of the plant, but through control strategies appropriate to those machine types rather than through anti-surge margin. For reciprocating compressors, final control elements can include variable clearance pockets, piston suction valve timing, variable speed, or recycle. Innova has control strategies for each, with the same basic suction- and discharge-pressure objective adjusted as supply and demand change. Screw compressors are incorporated into the station pressure-control framework through their available machine control interface and operating limits without applying centrifugal or axial anti-surge logic to them.
Why Innova Technologies
Station performance before promises
Capacity optimization starts with understanding how the station is operating today: where recycle occurs, how the machines are sharing load, how often operators have to intervene, and where usable operating range is being left on the table.
Innova evaluates those conditions before recommending a control change. If the station is already operating efficiently and there is little unnecessary recycle to recover, we will say so.
Where the opportunity exists, coordinated station automation can improve load sharing, reduce unnecessary recycle, simplify operating response across changing demand, and support remote and unattended station operation.
Open architecture, no vendor lock-in
Station control is deployed on IEC 61131-compliant platforms in simplex, dual, or triple modular redundant configurations. Innova works with the end user to select the design that meets safety and availability requirements, and with the client to select a platform that meets those requirements while maintaining common platform standards to reduce training, spare parts, and service costs over the life of the system. Supported platforms include Rockwell, Emerson, Schneider, and GE, with controller families including ControlLogix, CompactLogix, RX3i, Triconex, and Modicon.
The open architecture gives the user the application logic, tuning constants, and documentation to become self-sufficient, if desired, rather than depending on a single-source supplier worldwide.
Technical Resources
FAQ
Yes. Centrifugal and axial compressors can share station demand using each machine’s available turndown range and surge margin. Reciprocating and screw compressors are coordinated against the same station pressure or capacity objective through their own control strategies rather than through anti-surge load-sharing.
For reciprocating compressors, final control elements may include variable clearance pockets, piston suction valve timing, variable speed, or recycle. Screw compressor capacity control is integrated at the station level using the machine’s available control interface and operating limits. The station layer coordinates the overall demand while respecting how each compressor type actually operates.
Independent control for every turbine class.
Anti-surge, loadshare, performance, and capacity control.
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A MESSAGE FROM JOHN KAZOUR, CEO
To our customers and partners,
For more than 50 years, our team has helped customers keep critical operations running. We built our reputation as Petrotech by taking responsibility for control systems on important rotating machinery.
As more industries came to us with similar challenges across power generation, compression, and hydro applications, our engineering team kept finding ways to solve them. Eventually, the business outgrew the Petrotech name.
We are entering our next chapter as Innova Technologies. The new name reflects the full scope of our work as a rotating machinery control systems specialist. We engineer controls around the machine, deliver complete projects from design through commissioning, and provide support that stays with the problem until it is solved.
Our name is changing, but the people, engineering experience, and commitment behind the work continue. Our responsibility to active projects and installed systems carries forward under the Innova Technologies name. Your current contacts remain the right place to start, and we will communicate directly if an administrative record requires an update.
We appreciate the trust you have placed in us over the decades, and we look forward to continuing that work as Innova Technologies.
CEO, Innova Technologies
