The Application
Plant equipment such as boilers, turbines and heaters requires vent and drain lines. These vent and drain lines must be sealed during normal operation to prevent any loss of fluid. To accomplish this sealing, it is common to install two valves in series on each pipe line. When it is time to vent or drain a particular system, these valves are opened to allow the passage of steam, water or non-condensibles.

The Traditional Approach
Simple double-valving does provide an extra sense of security when sealing off a vent or drain line, similar to that of two locks on a door. However, the two valves (or locks) eventually falter against the strong, destructive forces opposing them. Having two valves (or locks) instead of one, will prolong the inevitable valve failure.

Setting a New Standard
No valve manufacturer has been able to tap into the potential benefits of double-valving vents and drains...until now!

To understand how Yarway has revolutionized the vent and drain processes, let's define the primary function of each valve:

One valve installed on the piping arrangement is designated as the "sealing valve". The primary task of the sealing valve is to resist any leakage of the fluid while the system is in normal operation. The other valve in the series will be identified as the "blowing valve". The blowing valve has the unenviable task of opening and closing through the erosive effects of high velocity flow and high pressure drops during a vent or drain mode.

External leak paths eliminated.
The one-piece forged body design of these valves removes unnecessary joints, gaskets and seams associated with welded and two-piece bodies. Body leaks often prove to be potential hazards to the environment and the worker. The Welbond valves have a simplified one-piece design to provide safe and effective operation.

Seat leakage greatly minimized.
Behind the seat leakage, seat seat misalignment, and valve erosion are all avoided with integral seat design. The Welbond valve has a solid Stellite seat ring which is fused to the body by a vacuum brazing process.

Maintenance costs are reduced.
Any potential wear will occur at the Welbond seat. Renewal of this seat with the proper tools and stem-disc replacement takes less than two man-hours. Since the Welbond is in-line repairable, the valve does not have to be removed from the piping. As a result, valve and insulation removal, welding, labor and materials are all areas where economic savings can be realized.