Dump Tube

Function

The dump tube is used in combination with a steam converting valve. Following pressure and temperature reduction, the bypass steam inside the valve is finally discharged via the dump tube into the condenser or the turbine exhaust line through a multitude of outlet bores. This design is applicable for both high-pressure applications directly connected to the condenser/exhaust line (e.g., waste-to-energy plants, biomass power plants, etc.) and large-scale power plants (coal-fired power plants, combined cycle gas and steam power plants) with various pressure levels (MP, LP).
The dump tube acts as the final pressure reduction stage upstream of the vacuum-operated condenser. Utilizing it as the final, supercritical pressure reduction stage means that the number of stages inside the valve as well as the size of the outlet nominal diameter can be optimized.
When applying dump tubes, two distinct installation principles are differentiated:

Water-cooled condenser
The dump tube is installed inside the condenser.
Air-cooled condenser
The dump tube is installed in the turbine exhaust line.

Design

The design of the dump tubes is highly versatile and fully customizable.
A distinction is made between single-stage and multi-stage dump tubes, as well as between different types with various connection styles, such as the torispherical head connection and custom arrangements of the steam outlet bores.
Welland exclusively specifies erosion-resistant materials for the dump tube, such as 13CrMo4-5/SA182F12 or 11CrMo-9-10/SA182F22.

Benefits

Reduction of the valve outlet nominal diameter
Reduction of control stages inside the valve
Low investment costs due to optimized structural design of the steam conditioning valve and dump tube
The diameter and length of the piping between the steam converting valve and the condenser can be reduced and shortened (saving both costs and space).
The steam entering the condenser is directed by the steam outlet bores within the dump tube in such a way that damage to the condenser's cooling tubes is prevented.