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Screw Pumps and Hydropower Screws


Screw pums are mainly used to pump large amounts of liquids to a relatively limited higher level. Screw pumps are mainly used for controlling water levels in canals and rivers but they are also used for transferring contaminated water in water treatment installations (return activated sludge pump, influent pump).

Hydropower screws produce electric energy by passing large amounts of liquid via a turbine from a higher to a lower level. The electro-mechanical configuration is similar to that of a screw pump.


Vijzelpompen en waterkrachtvijzels Thessaloniki Aandrijfgroep vijzels, voorzien van dieselmotoren, Lugang (Taiwan) Constructie vijzellichaam.

vandezande supplies screw pumps and hydropower screws of a very high quality and offers the possibility to combine both techniques in one and the same screw pump unit. The conflicting boundary conditions for optimal liquid levels are regulated by a hydraulic powered valve at the upper level which determines the amount of flow by the action of the turbine (as function of the revolutions per minute – r.p.m.) and, at the lower level the screw pump body has adapted blades.

The main advantages of screw pumps and hydropower screws are:

  • High flow
  • High efficiency
  • High reliability
  • Low maintenance
  • Long life (little wear and tear)
  • Fish friendly and easily installed in natural streams (due to the atmospheric function principal and the relatively low nominal revolutions per minute)
  • Self drawing
  • Easy access
  • Possibility to run dry over longer periods

At vandezande a screw pump consists of the following main components:

Screw pump unit
The screw pump unit consists of a central tube, on which blades are welded to form a continuous spiral thread. Depending on the required flow a two or multiple bladed spiral is fitted.

Screw pump trough
As well as a custom made concrete trough, for the installed screw pump, it is also possible to choose either a steel trough, mounted together with the screw pump in a rectangular concrete trough, or a self-supporting prefabricated steel unit which is provided with the necessary supports. With this last option, the screw pump together with the trough and drive line are delivered as one unit.

Splash guards
The purpose of these guards is to minimize the leakage rate which in turn optimizes the take-up rate of the screw pump thereby increasing the efficiency.

Upper bearings
The greased upper bearings take up axial as well as radial forces. The bearing housing is either wall or floor mounted. Self-aligning bearings are used to take up any misallignment, originating from distortion due to a sagging of the screw pump.

Lower bearings
The self adjusting lower bearings only take up radial forces and allow for thermal expansion of the screw pump. The lower bearings are mounted in a cast-iron housing with an alloy specially designed for this application. Different types of lower bearings are available: grease lubricated, oil lubricated or without lubrication (ecological bearings).

Drive unit
The drive unit consists of an external brake fitted on the rotating shaft of the motor connected to the rotating shaft of a right-angled or parallel gearbox via a transmission belt or flexible coupling. The low speed shaft of the gearbox is connected to the screw pump shaft with a flexible coupling. Screw pumps are fitted with a backstop brake in the gearbox. Hydropower screws are fitted with an external brake fitted on the rotating shaft of the gearbox.

Scraper Bridges


A scraper bridge is a mechanical construction that is an integral part of a waste water treatment installation. It can be used for transferring precipitated particles to a sludge collector pit or alternatively for depositing floating substances into a scum removal container.

There are two types available: for round basins (circular cleaning type bridge) and also for rectangular basins (rectangular cleaning type bridge).


Ruimerbrug 1 Ruimerbrug Harelbeke Vandezande Diametrale Ruimerbrug Brugge

At Vandezande a scraper bridge consists of the following main components:

Bridge construction
The bridge consists of either an aluminium casing, a steel coated or thermally galvanized tube construction or a modified beam construction. The construction spans either a half, two thirds or the total diameter of the basin. In the latter case, the bridge is in two sections and is vertically hinged one meter beyond the central rotation point. This is to allow the support trolleys, mounted at the end of each bridge section, to make maximum contact with the external perimeter wall. This avoids any surface irregularities affecting the smooth distribution of the load.

Central rotation point (only for circular cleaners)
The bridge is hinged at the rotation point with a grease lubricated ball race. At the location of the rotation point an electric power distribution unit is also installed, which provides the power supply for the drive mechanism and includes all appropriate safety controls.

Drive unit
Circular scraper bridge:
In addition to the bearing housing mounted on the central rotation point of the circular scraper bridge, the bridge is supported on the basin perimeter edge via a one or
two wheeled trolley. The motorized wheel is powered by a reduction motor via a continuous shaft. In the case of a two wheeled trolley there is, in addition to the motorized wheel, an extra support wheel. The displacement speed at the height of the external perimeter of the basin is 2.5 m/min.

Rectangular cleaner:
The transverse bridge is fitted with a two wheeled trolley on either end and four guiding wheels along the sides of the basin. The motorized wheels are connected to a single reduction motor to prevent skewing of the bridge. The drive shaft, the shell coupling and the supporting bearing housings are sturdily mounted to the side of the bridge. The displacement speed is about 1.8 m/min.

Furthermore the wheeled trolleys both types are of a semi closed unit equipped with adjustable snow clearing shields, obstacle protection and wheel slippage sensors.

Bottom scrapers
Circular cleaners:
The steel bottom bridges which are fitted with rubber scraping blades must clear away the precipitated sludge lying on the bottom of the basin and transport it to the central sludge collector pit. There are two types available: the first type is where the scrapers are hinge connected to the bridge with tie rods and a second type is where the scrapers are fitted with wheels that run around the bottom of the basin.

Rectangular cleaners:
The bottom scrapers cover the entire width of the basin and clear away the precipitated sludge lying on the bottom of the basin and transport it to the central sludge collector pit. The scrapers are suspended from the bridge with box section profiles and are kept at the correct distance by wheels which run along the bottom of the basin. The suspension of the bottom scrapers is constructed in such a way that they can be easily inspected from the bridge after they have been hoisted clear, via a (powered) cable drum.

Sludge scrapers (only for circular cleaners)
The central sludge collector pit is equipped with one
or two sliding blades and connected to the bridge with
a specially constructed sturdy framework. When the resistance is too high in the sludge collector pit the sliding blades retract automatically.

Input drum (only for circular cleaners)
The feeding of the contaminated medium takes place
via a central cylinder that discharges into the top of the input drum. The input drum directs the medium into the underlying sediment and thus prevents a short circuit flow between the central cylinder and the overflow ledge. An additional deflection baffle can be suspended under the inflow drum to prevent feedback from within the sludge collector pit. An opening is provided in the inflow cylinder to facilitate scum removal. This opening is equipped with a drawer and can be operated from the bridge.

Surface cleaner
Grease, oil and other floating substances are removed in an efficient manner by a surface cleaner. With a circular cleaner the surface cleaner is set up in such a way that all floating substances are collected from half of the diameter of the sediment basin and pushed to the scum removal unit. With a rectangular cleaner the cleaning action is executed in an efficient way from the dividing partition at the drainage section of the basin through to the scum removal unit.

Scum removal unit
Circular cleaner:
The scum removal unit consists of a collection chute in stainless steel, which feeds, by means of a gravity pipe, into a floating substances collector located outside of the basin. A movable scraper pushes the scum layer into the chute. An automatic rinsing valve flushes the installation with surface water from the sediment basin.

Rectangular cleaner:
The scum removal unit consists of a scum collector or trough which is connected, by means of a gravity pipe, to a floating substances collector located outside of the basin. The trough has a sufficient incline so that all collected floating substances are fed into the drainage system. The movable scraper on the bridge pushes the floating layer into the collector tank.

Overflow trough cleaning
The sediment basin can be equipped with a trough cleaning system, that is lowered into the overflow trough during the rotating movement of the bridge. Alternatively this can be rotated by means of an electric motor.

Vacuum cleaner
For both circular- as well as for rectangular cleaners the option exists for removal of the sludge via vacuum rather than scraping it into a collection pit.

Sludge Thickener


Sludge is an important side product in the waste water treatment process. The dewatering of sludge, which consists of 99% water, is carried out by installing a sludge thickener. The sludge is stored for a few days in round basins in which a slowly revolving paddle induces the sludge to solidify, due to the influence of gravity, which produces 2 to 4% of solid matter.

The paddle homogenizes and breaks down the sludge layers which in turn allows the water to separate so that the sludge can sink more rapidly to the bottom. Finally the sludge is transferred via the sludge scrapers to the sludge collector.


Indikker RWZI Amsterdam-West (Nederland) Indikker RWZI Amsterdam-West (Nederland)

At Vandezande the sludge thickener consist of the following main components:

Bridge unit
The bridge is of metal profile beams or of concrete construction and spans the entire basin.

Drive unit
The drive unit of the paddle is installed on the bridge unit and is fitted with a reduction motor. On the output shaft of the gearbox there is a pinion, that connects to the gear toothed bearing housing. This is in turn flanged onto the central tube of the paddle and the sludge scrapers. A mechanical torque limiter automatically switches the motor off when the maximum admissible torque is exceeded.

Paddle
The paddle consists of a framework of vertical bars and is connected to the central tube via a specially constructed framework, which covers the entire diameter of the sludge thickener.

Scraper mechanism
The scrapers are equipped with adjustable rubber blades, ensuring the optimal removal of the solidified sludge. The scraper arms are attached via struts to the central tube.

Input drum
The feeding of the sludge takes place via a central cylinder that discharges into the top of the input drum. The input drum directs the medium into the underlying sediment and thus prevents a short circuit flow between the central cylinder and the overflow ledge.

Grit and Scum Remover


In a water treatment plant the grit and scum remover separates grit (and oil and grease) from the contaminated medium. There are 2 different types of grit and scum removers: the circular grit and scum remover and the rectangular grit and scum remover. The feeding of the medium in the circular grit and scum remover basin is carried out via a supply channel, in which flow vanes

are mounted to ensure an even distribution of the flow. The precipitated grit and organic substances are pushed into a recessed pit by the bottom scrapers, while the waste water on the other side of the collector runs off the overflow ledge. With a rectangular grit and scum remover the gantry performs a back and forth movement. The gantry can be equipped with a vacuum pump or bottom scrapers to remove precipitated particles, and with surface scrapers to remove floating substances (scum).


Langszandvanger met airliftsysteem Step Tubize (België) Rondzandvanger Constructie langszandvanger

At Vandezande a grit and scum remover consists of the following main components:

Gantry unit
The gantry consists of an aluminium casing or metal profile beams which spans the entire basin. The circular grit and scum remover can also be made of concrete.

Drive unit
The drive unit of a circular grit and scum remover is similar to the drive unit of a solidifier facility. The drive unit of a rectangular grit and scum remover is similar to the drive of a rectangular cleaning gantry.

Scraper mechanism
With a circular grit and scum remover the scraper arms are mounted to the central tube via struts. With a rectangular grit and scum remover the scraper mechanism is mounted onto the gantry unit and can be raised. The forward movement lowers the scraper mechanism and the backward movement raises the scraper mechanism. Both types of scrapers are fitted with adjustable rubber blades, ensuring optimal removal of the solidified sludge.

Vacuum pump (only with rectangular grit and scum removers)
By blowing air through suppressors at the bottom of the basin, the precipitated particles can be removed from the basin via a funnel shaped shroud and a submersible tube. The vacuum pump is only active during the forward movement of the gantry.

The scum remover unit (only with rectangular grit and scum removers)
At the end of the forward movement the floating substances are removed by means of the surface rakes. During the backward movement the surface rakes are raised.

Automatic Trash Rack


An automatic trash rack facility is employed for removing a build- up of miscellaneous coarse debris in a canal or river by catching it in a grid structure. It is installed on the upstream side of pump stations or rivers. The debris is then collected, transported and finally deposited into a container.


Rooster Woumen Stenensluisvaart (België) Rooster St. Michiels Brugge (België) Rooster Woumen (België)

An automatic trash rack facility consists of the following components:

  • Depending on the width of the canal, 1 or more removable grid frames of stainless steel, equipped with vertical grid bars, are required. The distance between the grid bars can be selected. There is a choice between 40 mm or 100 mm. The grid frames are supported by guide rails, mounted at an angle of 75° in relation to the horizontal surface. The mechanical resistance of the grid frames with grid bars is calculated on a maximum height of the water upstream, without back pressure downstream.
  • The stainless steel bucket consists of a fixed part and a hinged part. When cleaning, the fixed part of the bucket slides down the grid bars into the build-up of debris. The hinged part of the bucket is then closed, using 2 stainless steel hydraulic cylinders. The fixed part of the bucket is compatible with the distance between the grid bars for a smooth operation and intrusion. In standard versions, the width of the bucket varies between 1,200mm to 1,800mm.
  • A moving trolley with support structure.

There are 3 different types :
Overhead transfer type: a moveable trolley is suspended from a monorail which is supported by a portal structure. The bucket is suspended from steel cables, wound round 2 cable drums.

Crane type: a trolley with hinged crane arms, moving on a track fitted with crane rails. The bucket is suspended from the end of the crane arms.

Hybrid type: a combination of the overhead transfer type and crane arm type: a trolley with fixed gallows, moving on a track fitted with crane rails. The bucket is suspended from steel cables, wound around 2 cable drums.

Overhead transfer:

  •  A reduction motor fitted with a brake operates the 2 cable drums of the bucket, which is suspended from steel cables.
  • Idlers prevent the unwanted unwinding of the steel cables.
  • A hydraulic power unit feeds the hydraulic cylinders of the bucket.
  • An electronically driven hose reel controls the hydraulic TWIN hose, which powers the hydraulic cylinders of the bucket.
  • The moveable trolley is suspended on runners, each of them are equipped with 2 vulcanized running wheels.
  • The transfer movement on the monorail of the trolley unit is operated via a reduction motor fitted with a brake.
  • All necessary sensors and limit switches are provided for monitoring the operation of the equipment.
  • The frame of the trolley and the machine housing are made of stainless steel. The access hatches are equipped with gas springs.
  • The steel portal structure with monorail is anchored onto the adjacent concrete structure.

Crane:

  • The steel crane arm consists of a main arm and a swivel arm; the bucket is hinged at the end of the swivel arm.
  • Hydraulic cylinders perform the movements of the crane arm.
  • A hydraulic power unit feeds the hydraulic system.
  • In this setup the crane arm is moved rotationally on a turntable fitted with a ring gear.
  • The rotational movement of the crane arm and the transfer movement of the trolley is driven by a reduction motor or via a hydraulic motor.
  • During the transfer of the trolley all steel wheels of the trolley are powered.
  • The steel track fitted with 2 crane rails is anchored onto the adjacent concrete structure.

Hybrid:

  • A reduction motor fitted with a brake operates the 2 cable drums of the bucket, which is suspended from steel cables.
  • The end of the gallows has guide wheels, over which the steel cables roll.
  • Idlers prevent the unwanted unwinding of the steel cables.
  • A hydraulic power unit feeds the hydraulic cylinders of the bucket.
  • An electronically powered hose reel controls the hydraulic TWIN hose, which powers the hydraulic cylinders of the bucket.
  • In this setup the crane arm is moved rotationally on a turntable fitted with a ring gear.
  • The rotational movement of the crane arm and the transfer movement of the trolley is driven by a reduction motor or via a hydraulic motor.
  • During the transfer of the trolley all steel wheels of the trolley are powered.
  • The steel track fitted with 2 crane rails is anchored onto the adjacent concrete structure.

For each configuration we provide the following custom engineered facilities:

  • Access steps, handrails, stairs and ladders specific to the accessibility requirements and level of security.
  • The installation of the monorail or track is undertaken to guarantee maximum integration with adjacent structures or to comply with legal building regulations.
  • Protection of steel structures: galvanizing and painting in the desired RAL colour or hot dip galvanizing.
  • Level of automation: PLC control and integration with already existing controls.

Water Management


Vandezande undertakes all types of work in steel construction and electromechanical installations used for the water management of canals and rivers.

A study of the possible implementation options is carried out to suit each set of circumstances followed by construction and assembly.


Waterbeheersing Segmentstuw Vandezande Asper Waterbeheersing Segmentstuw Vandezande Waterbeheersing Segmentstuw Vandezande

A few examples of suchlike work are:

  • Drives (segment weir gate, rectangular weir gates)
  • Valves (gate valves, slide valves, wheel valves)
  • Non-return flaps

Electromecanical Installations


VANDEZANDE is active in the supply of electromechanical installations for all types of government contracts e.g. …


Elektromechanische uitrustingen Evergem Elektromechanische uitrustingen Wintam-Zeesluis Vandezande Elektromechanische uitrustingen

Road bridges: mechanical or hydraulic drives for bridge movement and lock mechanisms

  • Ref. Plassendale Jaagbrug – Ostend (Belgium – West Flanders)
  • Ref. Straussbrug – Zeebrugge (Belgium – West Flanders)
  • Ref. Zennegatbrug – Mechelen (Belgium – Province of Antwerp)
  • Ref. Zandvoordebrug – Oudenburg (Belgium – West Flanders)
  • Ref. Zeebergbrug – Aalst (Belgium – East Flanders)
  • Ref. St-Annabrug – Aalst (Belgium – East Flanders)
  • Ref. Brug N°11 – Brecht (Belgium – Province of Antwerp)

Sluice gate mechanisms: mechanical or hydraulic drives for mitre gates, door gates, wall gates and weir gates e.g.:

  • Ref. Evergem sluis (Belgium – East Flanders)
  • Ref. Vancauwelaertsluis – Antwerp (Belgium – Province of Antwerp)
  • Ref. Duwvaartsluis Albert Canal (Belgium – The Albert Canal connects Antwerp with Liège)
  • Ref. Sluizen op Kanaal Leuven Dijle (Belgium – Flemish Brabant)
  • Ref. Iepersluis – Nieuwpoort (Belgium – West Flanders)