Introduction

This range of steam check valves has been specifically designed for installation in bled (extraction) steam lines between steam turbines and feed water heaters but are equally applicable to reheater connections and bleed on passout lines in process plants.

Their function is to prevent the reverse flow of stored steam and any water from the heater or its bled steam pipe to the turbine. Installation would be in a horizontal pipe as near to the turbine as possible.

These valves are Free Acting whereby the disc moves to the closed position when flow in the forward direction ceases. Gravity action on the disc provides a closing moment from the fully open to fully closed position. Where power assistance is required a Spring return pneumatic cylinder can easily be accommodated whilst still maintaining the automatic Gravity closing feature. The Dewrance bled steam Check Valve is the result of evolution from the original vertical seated design, field experience, customers requirements and is based on the Dewrance Tilting Disc Check Valve.

All Dewrance Tilting Disc Check valves are based on the same seat geometry of a conical seated disc in a conical body seat, which has been applied over a wide range of conditions from sub-atmospheric bled steam up to ANSI 2500 Class for steam and water. The seating intensity is high enough to give a good seal and yet low enough not to cause any surface scuffing. The position of the hinge pin ensures that the disc opens and closes without a rubbing action to effect a tight seal over the full range of pressures.

The combination of disc geometry and the body shape produce a seat angle which gives a short disc travel as the flow falls progressively with decreasing flow. This disc will be on the seat when flow ceases and before reversal takes place without SLAMMING. This arrangement gives a low pressure drop and flow under the disc assists in keeping the valve fully open over a wide range of flows.

Features & Benefits of Dewrance Steam Check Valves: