Choice of Sector and Materials
The variety of component and sealing materials available make this valve commonplace in many sectors with duties ranging from within sludge control - waste water, mining, power plants, pulp mills and many more.
Materials of construction
• Body materials include ductile iron, carbon steel, stainless steel 316, duplex and super duplex.
• Seating materials include NBR, EPDM, EPDM WRAS approved, VITON, silicone, natural rubber and polyurethane.
• All of these dependant on the media and temperature requirements.
Choice of working pressures
Many associate a knife gate valve for operation where working pressures are typically low; sludge plants where pressures such as 4/5 bar, even less are the norm, however AVK routinely manufactures knife gate valves that in some cases exceed 100 bars. These are very much dependant on valve size, please see figure.
In addition the working pressure of the valve can be reduced to suit the application whilst still maintaining PN16 flanges. This reduces the valves weight and cost, and is a standard specification for the UK water industry.
Choice of Functionality
The AVK UK knife gate valves can be supplied with operators such as;
• Hand wheels
• Chain wheel operation
• Electric actuators
• Double and single acting pneumatic actuators
• Linak actuators
• Hydraulic actuators
• Basic levers
All are designed and manufactured to suit a specific application. In addition, end of travel limit switches, scrapers, closed bonnet (only for standard working pressures) etc., can all be supplied to the basic valve as and when required.
Choice of Duty
Standard gate valves have become the core product for isolation in the water sector over the years. Although not suited for modulating or flow control applications, and in terms of sludge flow control there are but a few valve types available for such arduous duty.
Series 764 plug valves, manufactured by AVK UK, although quarter turn in design have a full bore and where square ported, have linear flow capability which offers a solution for many flow control applications in sludge. Depending on the specialist nature of the ‘flow control ‘application - the standard AVK knife gate valve is available in larger sizes and gives a viable alternative in a light weight option, as well as a reduced face to face dimension, reducing working confines giving less costly pipe supports/ civils structures culminating in potentially lower craneage costs.
Where the standard wedge gate valve should not be used as a modulating flow control device, the AVK knife gate valve can and is used as a flow control
option. This valve can also be fitted with specially designed ports to match the flow requirements, for example; V port, diamond port, square port etc.
This offers a greater degree of reliable flow control function than that of the standard knife gate valve. Full flow control curves / KV values and technical information are available.
Valve selection checklist;
1. Valve function- flow control/modulating/ on off application /cycle (details e.g. 6 time operation per hour)
2. Valve size / diameter
3. Valve pressures- maximum/minimum working pressures
4. Differential pressure
5. Valve flow - maximum/minimum
6. Operation- how is the valve operated and where from e.g. locally or from platform above
7. Actuator location- direct mounted /indirect mount via floor mounted pillar etc.
8. Actuator specification- Electrical supply
As referenced in the opening paragraph AVK UK can offer a wide range of products to suit a multitude of applications and because we manufacture all of
these options, we will offer what is ‘right’ for the application not just because we want to promote a particular range (which is often the case for some distributer competitors).
Contact Stuart Montgomery for more information regarding this range of products please refer to AVK UK website.