Air release valve delivery information

Four Sizes, One Order: DN40 to DN200 Air Valves Leave the Factory

Most air valve orders are tidy. One size, one pallet, one line on the invoice. The batch that left our factory on November 5 was not tidy, and that is exactly what makes it worth writing about.

Fifty-nine double orifice air release valves: 10 pcs DN40, 34 pcs DN50, 11 pcs DN100 and 4 pcs DN200. PN10/PN16, flanged to EN 1092-2, GGG50 ductile iron. For the buyer this is one purchase order and one supplier to chase. Inside the workshop it is four separate production runs that all had to be cast, machined, tested, packed and loaded on the same day.

The sizes look like a simple ladder. The loads they carry do not. End thrust rises with the square of the bore, so at 16 bar the DN200 flange on this batch carries around 50 kN, the DN100 around 13 kN, the DN50 around 3 kN and the DN40 around 2 kN. That is a 25 to 1 spread inside a single packing list, and the parts that carry it do not scale in step. Buoyancy follows the cube of float diameter, which is why the DN200 float is not an enlarged DN40 float. It is its own casting, with its own wall section and its own seat ring.

The exception is the small orifice in the side chamber. Its size barely changes across the range, because the air it bleeds off comes out of solution according to water volume and temperature, not valve size. One design decision holds across four different castings.

The working principle is identical on every size. During filling, the large orifice under the hood vents the main at full bore so the line fills fast. On drain-down it lets air back in, so the pipe is not pulled flat. Once the line is under pressure the large orifice seals and the small orifice takes over, releasing the air that keeps coming out of solution. Two orifices, two jobs, no operator involved.

Every body is cast in GGG50 ductile iron to ISO 1083 and EN 1563, grade GJS-500-7, with at least 500 MPa tensile strength and 7 percent elongation. Each one is epoxy coated inside and out and carries its month of manufacture in the casting itself. On this batch it reads 202611. Every valve was pressure tested before packing. The small sizes travelled in wooden cases with a cardboard grid between them, and the DN200s were braced on their flanges. Nothing in the shipment touches anything else.

Fifty-nine valves, four sizes, one shipment. For a project that needs more than one size on the same order, this is not a special request here. It is the normal case.