Vents (click on underlined links below to see one page brochure of vents)
Two types of vents suitable for lowering the humidity in valve chambers are discussed here:
1. Swivel-venturi vent - The principle here is that the venturi can rotate horizontally, and a vertical vane aligns it with the wind. Then as the wind passes through the narrow section of the venturi a suction is created that pulls out the moist air from the valve chamber - this air is replaced with drier air from outside. This vent system is suitable for all valve chambers and reservoirs, and may be made from steel or plastic.
2. Enclosed-venturi vent - Here there are two venturis, at 90 degrees to each other, so that regardless of the direction of the wind at least one will suck air out of the chamber. Furthermore the efficiency of both these venturis are improved by enclosing them in a cylindrical body such that only their two ends are open to the outside. According to the laws of fluid dynamics the air pressure in the lower right venturi is greater than atmospheric pressure on the upwind side and conversely lower than atmospheric on the downwind side - this forces more air through the venturi, making it in effect a super venturi. On the other hand the venturi at the top left experiences a negative pressure at both ends (owing the wind moving faster at these sides, resulting in lower pressure), and hence both ends of the venturi will suck out humid air from the chamber. In these vents the ducts and funnels of the venturis may all be made of thin plastic, and encapsulated in cylindrical body of concrete. This effectively makes this vent virtually immune to theft/vandalism.
1. Swivel-venturi vent - The principle here is that the venturi can rotate horizontally, and a vertical vane aligns it with the wind. Then as the wind passes through the narrow section of the venturi a suction is created that pulls out the moist air from the valve chamber - this air is replaced with drier air from outside. This vent system is suitable for all valve chambers and reservoirs, and may be made from steel or plastic.
2. Enclosed-venturi vent - Here there are two venturis, at 90 degrees to each other, so that regardless of the direction of the wind at least one will suck air out of the chamber. Furthermore the efficiency of both these venturis are improved by enclosing them in a cylindrical body such that only their two ends are open to the outside. According to the laws of fluid dynamics the air pressure in the lower right venturi is greater than atmospheric pressure on the upwind side and conversely lower than atmospheric on the downwind side - this forces more air through the venturi, making it in effect a super venturi. On the other hand the venturi at the top left experiences a negative pressure at both ends (owing the wind moving faster at these sides, resulting in lower pressure), and hence both ends of the venturi will suck out humid air from the chamber. In these vents the ducts and funnels of the venturis may all be made of thin plastic, and encapsulated in cylindrical body of concrete. This effectively makes this vent virtually immune to theft/vandalism.