Needle Valves

Needle valves are used to eliminate the intermediate level transfer basins/reservoirs in the case of pipelines supplying water directly from the high level storage reservoirs to low level storage reservoirs. The energy saved in this way is utilized for obtaining increases flow in the pipelines during periods of high consumer demand. By appropriate positioning of the needle valve, the flow is regulated so as to adapt to the variations in consumer demand.

These valves can be supplied in sizes from 75mm to 2000mm (Larger sizes, are also available in request) for a working pressure upto 30 bars and for flows unto 20 m³/sec.

Applications

Some of the common applications are :-

• Inline regulation.
• Terminal regulation – free discharge to atmosphere.
• Terminal regulation –expansion.
• Auxiliary by-pass filling.
• Pumping station by-pass valves.

Particularly in Water supply installations and irrigation schemes, it is mandatory requirement to adjust to variation in demand. He flow between upper and lower reservoirs should be regulated by valves that are suitable for operation under condition of high flow such as 20 m3/sec and under differential head. These needle valves are precisely suitable for these application.

Further, Fouress-Boving Needle Valves are specifically designed to achieve maximum energy dissipation with a minimum of cavitation and vibration effects. In large size Needle valves air is sometimes introduced slightly down stream of the valve throat where a clear line of separation creates a suitable void or negative pressure region.

Introduction of air on downstream reduces noise, vibration and also assists in energy dissipation functions effectively. Normally these valves are offered with either manual or electrical operation. On specific requests, other forms of operation can also be incorporated. Our principals Boving Newton Chambers Engg. Ltd., U.K. have supplied these valves upto a maximum size of 2000 mm to various Water Supply installation, Irrigation Schemes, etc. through out the world which are performing extremely well till date. Added to these, Fouress has supplied Needle valves penstock valves by-pass systems. Some of these valves are under successful operation at Tata Electric Company (Khopoli Hydro Electric Project), and at Himachal Pradesh Electricity Board, Shimala (Sanjay Vidyut Pariyojana Hydel Scheme).

Construction

The 600 mm size valve shown in Figure 1 is essentially a developed from PELTON turbines and is used almost exclusively for terminal regulation or by-pass purpose. This type of valve is used for heads upto 500 MM AND FLOWA OF 4 Cu.mecs. The valve shown had a casing of composite construction with cast steel and fabricated sections joined by welding,. The needle , seat ring and operating spindle are supplied in high grade stainless steel and the bearings are of self lubricating type. Normal operation is by means of a rear mounted motor/gear box unit with rotating nut machined to suit the thread operating spindle which functions as an extending spindle to position the needle.

Figure illustrates the general arrangement details of a 1500 mm Needle valve which can be used for virtually all regulating application except for auxiliary by-pass systems. For the application involved, the working conditions for these type of valves does not extend beyond 200 M referred. The complete body is of fabricated construction with seat ring and operating spindles in high grade stainless steel. Operation is by means of the input shaft to a bevel wheel and pinion, driving a rotating nut around a threaded center spindle which axially controls the position of the needle. The input shaft is mounted in self-lubricating bearings while bevel gear and center spindle are submerged in grease packed compartment with bronze collars o take the axial thrust. Holes are drilled along the downstream needle cone to ensure balanced operation at all times and normal operation is by means of electric motor actuator mounted on the valve casing and directly coupled to the input shaft.

The design of Fouress-Boving Needle valves are determined and finalized based on the extensive model studies conducted by our principals in KMW Hydraulic laboratory at Sweden. The cavitations, noise level characteristic etc., have been tested on a full scale model after the prototype model tests and these tests proved that these characteristics have improved by around five per cent than the protype designs.

Material of Construction