Guaranteed leakage rates in accordance with BS7775 for penstocks and WIMES 8.10 of no more than 0.4l/min/m of seal perimeter on-seating head and off-seating head conditions.
Fabricated stainless steel penstocks are a cost-effective solution compared to cast iron. As the size of the penstock increases the saving increases.
The ultimate strength of stainless steel is more than twice the ultimate strength of cast iron and approximately twice the modulus of elasticity of cast iron.
Stainless Steel resists corrosion better than cast iron. The UV-Stabilized UHMWPE seat/seals are field proven to maintain shape and integrity in demanding applications and have been tested with 25,000 gate open/close cycles in an abrasive media to show only negligible wear.
Even after long periods of inactivity, the slide will not “freeze” to the frame which can be seen in cast iron penstocks. The UHMWPE seat/seals prevent any metal-to-metal contact between the slide and the frame.
Stainless steel penstocks do not require periodic painting and require less operator attention compared to cast iron penstocks.
The IQ Whipps Series 900 stainless steel penstocks have a self-adjusting seal system that eliminates the need for field adjustment. This seal system was developed because many penstocks are installed in locations where field adjustment of wedges is not practical or possible. Wedge adjustment is an inexact science and when attempted by inexperienced personnel can lead to additional leakage, difficult penstock operation and increased localized penstock stresses. The self-adjusting seal system is a combination of durable UHMWPE seat/seals and a resilient static spring/seal. The UHMWPE seat/seals are shaped to form a low friction, yet tight, seal with the slide. The spring/seal serves two main purposes: Firstly, it acts as a bulb seal between the frame and the UHMWPE seat/seals, and secondly; it acts as a “spring” to ensure continuous contact between the UHMWPE seat/seals and the slide. The spring/seal is stationary, like an O-ring seal, and it is protected from wear or damage from the movable slide by the UHMWPE seat/seals.
In the unusual event that the seat/seals are damaged, they can be replaced in the field with routine tools. The penstock does not have to be removed from the wall. If the seating surface on a cast iron penstock is damaged, the penstock will have to be removed from the wall and shipped back to the manufacturer for re-work.
The process to design and manufacture fabricated penstocks allows for a nearly unlimited range of sizes. This is not the case with cast iron penstocks since new patterns or modifications to existing patterns are required to accommodate unusual sizes.
Penstock frames may be embedded in the channel walls, mounted to a wall with anchor bolts and mounted to a pipe flange or wall thimble. Wall thimble mounting is possible although it is usually only necessary for applications with high off-seating heads. Penstocks can also be designed to mount to existing wall thimbles or existing pipe flanges. Flanged frames or flat frames are available for penstocks to cover square, rectangular, or round openings in concrete structures.