Precision pressure measurement in high-temperature CSP application

Concentrated Solar Power (CSP) systems generate electricity by using mirrors or lenses to focus sunlight onto a receiver, where it is transformed into thermal energy. This heat is used to produce steam that powers a turbine, generating electricity that can also be stored—typically in molten salt—for use when sunlight is not available. To ensure efficiency and safety across these stages, precise pressure measurement is essential. CSP plants operate under extreme conditions, requiring sensors that can reliably detect very low pressures even at temperatures reaching up to 600°C, with significant fluctuations in both process and ambient temperatures.

The CSP-E and CSP-H series pressure sensors have therefore been designed to meet these requirements, working in contact with high-temperature viscous fluids, minimizing thermal drift and ensuring high measurement accuracy.
The design principle of these sensors is based on hydraulic pressure transmission: mechanical stress is transferred from the contact membrane to the measuring membrane via an incompressible NaK (sodium/potassium) transmission fluid.

The sensing element consists of a Wheatstone bridge strain gauge, manufactured using thick film technology. The CSP-E and CSP-H series are available with a 4-20 mA output signal and HART protocol. The flange connection ensures an optimal hydraulic connection to the system.

These transducer offer high accuracy (±1.0% FS) and resistance to temperatures up to 538°C, with pressure ranges from 0-20 to 0-1000 bar (0-300 to 0-15000 psi). It features a flanged connection, integrated (or external) auto-zero function, and Inconel 718 components for maximum durability and resistance in extreme environments.

Flanged connections are widely used in piping applications to connect pipes together, and are particularly useful when access is required for equipment or detection systems. This type of connection also facilitates the separation of pipes when required. A flanged connection consists of two flanges (flange and counterflange), a gasket, and bolts.
The joint between the two flanges creates a seal that prevents fluid or gas leaks, protecting the internal environment from external contamination. Gefran CSP pressure transmitters are available with two types of flanged connection:

• RF – Raised Face
• RTJ – Ring Type Joint

The installation of the sensor plays an extremely important role in ensuring its correct functioning. It is advisable not to place the tip of the sensor directly on the main pipe inside the flow, but to use a piezometric bypass. The insulation of the piezometric bypass must not cover the sensor stem. Similarly, it is necessary not to completely insulate the stem, but to limit insulation to the area below the flange. This is to contain the heating of the sensor to the area where it is attached to the process, thereby limiting the thermal drift of the sensor.