Electronic Modulating Level Control Text Only

Electronic Modulating Level Control

Modulating level control is essential to a properly functioning pressureized deaerator and high pressure steam boiler.  For more information see engineering guidelines related to Modulating Feedwater vs. On-Off pump control and Pressure Decay in deaerators.

The RWF40 Modulating Feedwater Control Valve Application Guide is intended for use by OEMs that integrate the RWF40 controller into their products.

This application combines separate modular components to produce a modulating feedwater control. The valves in this guide are typically applicable to steam boilers in the 200-2500 HP range.

The transmitter must be mounted below the minimum water level. Since the high and low pressure lines have equal and opposite forces below the minimum level, they will cancel each other out. This allows the transmitter to be mounted at any distance below minimum. The transmitter must be mounted in the vertical position.

The high pressure line is kept completely full of condensate and will be used as a reference. Open or vented vessels require only a high pressure connection.

What you need

Valve actuators

Overload-proof through travel-dependent, electronic switching off in end position.
With die-cast aluminium housing and yoke for valves with 20 mm stroke. Optional function with one auxiliary switch. With manual control.

•    Fitting actuators to valves which are already installed in the plant
•    Replacing obsolete actuators
•    Motorizing of manual valves
•    Fitting and Testing of customer supplied components
•    Installation and commissioning of completely coupled and tested automated Valves in the field

Differential Pressure Transmitter

In order to measure the differential pressure the reliable transmitter, differential pressure transmitter, is installed to the metering section.
The transmitter provides a 4 … 20 mA output signal, from which the flow processor calculates the flow rate. Oxygen applications are provided with a special model.

Control Panel

Control panels are available in a number of configurations to meet the requirements of the applications. Shown
here is a simple control panel that makes use of relay logic to control a pair of pumps. Control panels are manufactured to UL508 requirements.

Typical front panel with alarm lights, “Hand-off-auto” switches for two pumps and a lead pump selector switch. Inside view of the control panel showing the circuit breakers, moton starters, and relays along with field terminations.