Woodward CPC-II electro-hydraulic current pressure converter

Woodward CPC-II electro-hydraulic current pressure converter: technical selection and implementation points for replacing and upgrading CPC and Voith E360 I/H after discontinuation

Industry Pain Point: Oil Pollution - The Number One Issue in Turbine Control Reliability

In the steam turbine control system, the electro-hydraulic current to pressure converter (I/H Converter) is the core component that converts the current command output by the controller into a hydraulic pressure signal, and then drives the actuator of the regulating valve (throttle valve). The throttle hole and precision valve port of this component are extremely sensitive to the cleanliness of the oil. The deposition of particles and sludge in the oil during long-term operation can cause jamming, delayed response, decreased control accuracy, and even force unplanned shutdown of the unit for filter replacement and component cleaning.

Woodward explicitly states in his application technology literature that oil pollution is the top reliability issue in the steam turbine market. The traditional coping methods are frequent maintenance of precision filters and regular cleaning of converters, but this not only increases operation and maintenance costs, but also introduces additional pressure drop and potential failure points due to the presence of filters themselves. In response to the pain points in this industry, Woodward has launched the second-generation Current to Pressure Converter CPC-II (Generation 2) and simultaneously launched an upgrade plan for old CPC and Voith E360 I/H users.

Special attention should be paid to the timeline: CPC products have been discontinued since July 2012, and the official recommended replacement model is CPC-II. Power plants and equipment owners who are still operating CPC devices online should develop spare parts and upgrade strategies as soon as possible to avoid the passive situation caused by shutdown and supply interruption.

Analysis of CPC-II Core Technology

2.1 Dirt Buster and Silk Buster Anti pollution Technology

The core innovation of CPC-II is the "Dirt Buster" technology, which is reflected in two aspects of hardware enhancement:

The driving force of the actuator is increased by 4 times: the stronger electro-hydraulic actuator can still reliably operate when particles invade, and will not be stuck by 40 μ m level dirt;

Self cleaning valve core design: The valve components have self-cleaning characteristics during operation, and with the patent application's "Sill Buster" sludge cleaning technology, it can remove sludge accumulation without interrupting operation or damaging the integrity of operation - this means that there is no need to shut down and drain oil for cleaning, and the continuity of operation is fundamentally guaranteed.

The practical application effect is that CPC-II can directly "pass through" 40 μ m sized pollutants, thereby reducing or even completely eliminating the front-end filter and its maintenance workload of the converter. For old units with difficulties in purchasing filter spare parts and tight maintenance windows, this characteristic has significant economic value.

2.2 Control performance advantages

CPC-II integrates Woodward's industry-leading control point algorithm, advanced diagnostic capabilities, and PC based service tools, with performance advantages reflected in:

Pressure output is "quiet" and stable: Traditional I/H converters generate excessive pressure "noise", leading to increased wear and tear of the servo system; The dynamic characteristics of over damping also result in delayed response. CPC-II achieves stable pressure output while balancing low wear and fast and accurate command response;

Bumpless precision throttle valve control: ensures control stability under normal operating conditions, achieves disturbance free switching during plant upsets, and minimizes process overshoot and overshoot to the greatest extent possible;

Step response approaching ideal: From the performance comparison curve, it can be seen that during the process of pressure decreasing from about 4.8 bar to 2.7 bar and then rising again, the output transition of CPC-II is smooth, and the servo position response of the steam valve is close to the ideal step characteristic, while traditional I/H converters are accompanied by significant fluctuations and steady-state deviations.

2.3 Functional Capability Comparison

Compared with the older generation CPC and Voith E360 I/H, CPC-II is comprehensively ahead in terms of functional matrix:

Ability/Function CPC-II CPC Voith E360

Oil pollution tolerance ✓——

Resistance to silt accumulation ✓——

Valve linearization compensation ✓——

Corrosive pollution tolerance ✓ - x

Viscous (high friction) mouth compensation ✓ - x

Accept redundant pressure set point input ✓——

Accept redundant pressure sensor input ✓——

Accept external cylinder position sensor ✓——

Internal health monitoring ✓——

Manual Stroking Function ✓ - x

Input/output isolation ✓——

Performance Trend Tool ✓——

Performance/stability adjustment ✓ x -

In addition, CPC-II has increased the inlet pressure option to 25 bar (with an expanded range compared to the previous generation), providing optimal flexibility for redundant control configuration through isolated input-output, advanced redundancy management, and performance monitoring management capabilities. The introduction of redundant set point inputs and redundant pressure sensor inputs enables the seamless integration of CPC-II into a dual channel regulation system with high availability requirements.