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Penstock definitions general

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Cast iron Penstock


A device for controlling the flow or level of liquid, consisting of a door that slides up and down, controlled by a mechanically operated spindle, which can be handwheel operation, electric actuator operation, pneumatic actuator operation and hydraulic actuator operation.


Penstock aperture

The size of the opening in the Penstock frame for the passage of liquids. For rectangular Penstocks, the width is the horizontal aperture dimension and the height is the vertical aperture dimension; the aperture dimension is first the width dimension and then the height dimension. [see picture 1]


Figure 1 penstock aperture


Penstock door

A closed shutter held in the frame, the door is slid up or down by operating an operating device connected to the shaft to expose or cover the frame hole and seal (see Figure 2)


Figure 2 Penstock door


Penstock frame

Fasten the Penstock to a concrete structure or pipe flange and keep the door sliding vertically up or down, while only allowing the door to move vertically between the open and closed positions (see Figure 3)


Figure 3 Penstock frame


Door guide

A component that may be attached to the gate frame or the door, or be part of it, to keep the door sliding up and down. (see Figure 4)


Figure 4 Penstock door guide



Integral or separate beams on top of both sides of  frame. (see Figure 5)


Figure 5 Penstock yoke


Wedging or pressure device

The assembly that presses the door and frame sealing surfaces together, (see Figure 6)


Figure 6 Penstock wedging or pressure device


Penstock leakage

When the door is in the fully closed position, pass the liquid value between the door and the frame sealing surface of the Penstock.



The top surface of the wall or channel wall may also be in the same plane as the Floor (see Figure 7)



Standing surface of the staff operating Penstock. Mounting surface for Penstock pillar. (See Figure 7)


Figure 7 Penstock Floor or coping


Pillar or Head stock

Structural components that support operating equipment at a convenient height for operation. (See Figure 8)


Figure 8 Penstock Pillar or Head stock



The underside of a channel or pipe. (See Figure 9)


Figure 9 Penstock Invert


Channel fixing Penstock

Penstock is fixed to the pre-formed rebates on the sides of the channel (see Figure 10) and the inverted arch of the channel, with or without anchor bolts, and the penstock frame is sealed to the notches with non-shrinkage grout.


Figure 10 Channel fixing Penstock


Pipe flange fixing Penstock

Penstock bolted to pipe flange. (See Figure 11)


Figure 11 Pipe flange fixing Penstock


Wall fixing penstock

An installation method in which the penstock is fixed to the vertical wall of a channel, chamber or similar structure by means of embedded steel plates or anchor bolts, and is sealed to the wall with non-shrinkable grout. (see Figure 12)


Figure 12 Wall fixing penstock


Wall thimble fixing Penstock

The Penstock is bolted to metal inserts prefabricated into the desired shape in the civil structure. Wall thimble fixing Penstock is generally recommended when the off-seating head is very high. (see Figure 13)


Figure 13 Wall thimble fixing Penstock


Non-rising spindle nut

The screw spindle nut is located on the door so that the nut drives the door to slide up or down. (see Figure 14)


Figure 14 Non-rising spindle nut


Rising spindle nut

A lead screw spindle nut located in the operating device so that the spindle drives the door to slide up or down. (see Figure 15)


Figure 15 Rising spindle nut


Spindle block

Parts for easy connection of spindles to Penstock lead screw nut sets or operating equipment.


Spindle coupling

A structural component used to connect a spindle lead screw in order to achieve the desired spindle length. (See Figure 16)


Spindle guide bracket

Intermediate support for the spindle to prevent buckling under compressive load conditions when the spindle is extended. (See Figure 16)


Figure 16 Penstock spindle guide bracket and Spindle block


Universal coupling

Structural components for penstock and handling equipment that require offset, only for non-rising spindles.


Spindle protection tube

A tube that protects the ascending spindle from damage and isolates the operator from the penstock stem, made of metal or transparent material. (See Figure 17)


Figure 17 spindle protection tube


Coping bracket

A device to support the operating equipment on the roof or on the wall.


Door position indicator

A component, usually attached to a rising spindle, that indicates where the door is at the moment.


Maximum static head

The maximum possible differential head for which the penstock has to be structurally designed.


Differential head

The difference between the on-seating head and the off-seating head when the door is in the closed position.


Off-seating head

Fluid pressure forcing the door away from the frame seal (see Figure 18)


On-seating head

Fluid pressure forcing the door against the frame seal. (see Figure 18)


Figure 18 off-seating head and on-seating head


Operating head

The maximum differential head against which the penstock will be operated.


Input effort

The input effort shall be limited to a maximum of 250 N on the crank handle, tee key or handwheel rim. Electric actuators, hydraulic/pneumatic cylinders shall have sufficient power (using the actuator or cylinder manufacturer’s recommendations) for the calculated torque or thrust requirements, to operate the penstock against the maximum operating head.


Direct type thrust

Thrust force transmitted directly from the operating equipment to the penstock frame yoke. (spindle nut mounted on the Yoke)


Remote type thrust

Thrust force transferred from operating equipment to structures remote from the pressurized water frame. (spindle nut mounted on operating column).


Dimensions from the vertical wall where the Penstock is installed to the centerline of the Penstock spindle. (see Figure 19)



The downward face of the top of the channel. (See Figure 19)


Figure 19 Outreach and Soffit


Operating equipment

A device integrated with the Penstock, manually or through a gear box, bevel gear, etc., the power operation of the mutual matching makes the Penstock door raise or lower. (see Figure 20)


Figure 20 Penstock Floor column operation type


Isolating penstock

Use Penstock once a day or infrequently.
Note: Operationally it can be fully open or fully closed.


Modulating penstock

Run Penstock more than 60 times per hour to provide flow control by moving the door up and down frequently.


Regulating penstock

Run the Penstock no more than 30 times per hour, fine-tune the flow by moving the door up and down occasionally.


Flush invert type

A type of Penstock structure, the sealing structure at the bottom is different, the sealing strip is installed at the bottom of the door or the bottom of the frame, and the sealing is perpendicular to the other three sides. Suitable for flat bottom installation. (see Figure 21)


Figure 21 Flush invert Penstock type


Rebate invert type

A Penstock structure, where the sealing strips on all four sides are in the same plane, is preferred.


Weir type Penstock

Contrary to the normal Penstock, the door is slid vertically upward to close, and the door is slid vertically downward to open. Side and reverse sealing in all intermediate positions between open or closed.


Metal seals Penstock

Metal sealing face on Penstock frame and/or door, can be integral with frame and/or door or fixed to frame and/or door. Mainly used for heavy duty Penstock, cast Penstock mainly choose bronze sealing and stainless steel metal sealing face.


Resilient seals Penstock

One or more elastomeric sealing surfaces on the pressure tube frame and/or door are fixed to the frame and/or door, usually in combination with one or more metal or plastic sealing surfaces, Resilient is often used for lightweight welded gates such as carbon steel and stainless steel seals, the main sealing material is EPEM.

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