Ductile Iron/Cast Iron Penstocks are highly preferred for their reliable performance and longevity. They can survive a service life of around 100 years and more. They are made with heavy-duty cast iron, constructed with substantial ribbing for resistance to deflection. Frame connection is of flat back or spigot type for extending into concrete, spigot end type provides extra stiffening to the frame. Flange connection is also available on request for circular and rectangular sewage penstocks. These types of connections are preferably used for enabling bolting installation to the flange inlet pipe and wall thimble installation. On each side of the frame, guide channels are provided for the gate and extended to a sufficient height to ensure that the gate is supported over not less than two-thirds of its depth when at maximum lift.
The body seat and gate seat normally consist of bronze seating strips of heavy rectangular sections which are pinned to machines surfaces on body and gate which are then ground in together to a watertight bearing. The bronze strips are also fitted as bearing surfaces in the guides into which the gate lifts. In the case of sea-water or sewage, aluminum bronze is used or alternatively is stainless steel.
There are cat iron cover bars on every side of the frame extending vertically down with adjustable block for limiting the downward movement of the gate. In these places, tight closure is required and when under pressure, the gates are forced away from the frame, additional top and bottom wedges are provided. When strong support is required due to heavy loading, top wedging is a cast iron bar spanning the gate, having taper faces against which the hate wedges work. The number of wedges present depends on the size and shape of the penstock and the pressure conditions.
With us, you can get both rising and non-rising stem construction. In the non-rising stem design, the operating threads engage a tapper lifting nut which is housed between lugs at the head of the gate, the gate is cast with a barrel for accommodating the projection of the stem at open positions. In the rising stem variant, the stem is bolted to stem nut and has the operating thread at the upper end where it engages a revolving nut in the actuator. All the stems are suitably sized for duty and furnished with a machine-cut thread of stub acneform. High-grade materials appropriate to the service requirements are used, the selection of which is based on factors like the nature of the fluid to be handled, the operating load, the distance from the gate to actuator, etc. aluminum bronze and stainless steel arc alternatives and regularly employed.