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24 hours per day, year after year, continuously working with corrosive and erosive fluids under high pressure and at high temperatures. Splashing of pulp and alkalines, vibrations created by refiners and pumps, pressure shocks, crystallisation and scaling, impurities such as sand and metal wires. It is under these conditions that valves installed in the pulp and paper industry have to work and to work properly as any failure will result in unacceptable production losses.

V&A has a long history in the pulp & paper industry together with global leaders NAF and Stafsjö who themselves each have more than 100 years’ experience in the pulp & paper industry. V&A have extensive experience supplying equipment to Mondi Business Papers, Sappi Chemical Cellulose, Sappi Southern Africa, Sappi Fine Papers, Mpact and Nampak.

Rotary Valve selection for Pulp and Paper in general

NAF Rotary control and on-off valves have been used in almost every type of pulping installation since they were introduced in the beginning of the 1950’s. High capacity combined with easy automation and maintenance have been the key factors to the success. In the digester area the flanged, NAF-Duball full-bore ball valve has great advantages due to its high capacity and good resistance to stress from pipeline. If the flowing media includes chips, stones or similar items, the use of metal seated valves is common. The consistency of pulp is one criterion in valve selection. Shut-off valves for pulp consistencies of 5% or more should be the NAF-Duball full-bore ball valve. In control duty, the NAF-Setball ball sector valve is the preferred choice. This valve type gives the optimal trim form to avoid clogging and dewatering of the pulp. NAF-Torex metal seated butterfly valves do an excellent job in steam control as well as steam shutoff service. These valves are also becoming common in the air evacuation, liquor fill and liquor circulation.

Rotary Valve selection for Chemical Pulp

Rotary Valve selection for special application Batch digester

The blow service is one of the most severe valve applications. The sudden release of energy when the valve opens creates high flow velocities and in many cases a severe shock in the line. This line shock creates high peak impact to the blow valves for the other digesters connected to the same manifold. A NAF-Duball full-bore ball valve with reinforced ball and locked stellite seat rings is frequently used this on/off service.

Continuous digester

The valve for feeding of MP-steam is a part of the safety system for the digester. The valve must close if the pressure in the digester exceeds the allowed pressure. A NAF-Duball full-bore ball valve with satellite seat rings is used. The valve has a spring return actuator, spring to close and may be locked in closed position.

Switching valves for spent liquor

These valves are exposed to full stroke operations as often as 1 time/120 seconds (262 800 times per year). This together with heavy vibrations and pressure shocks require very good valves. A NAF-Torex metal seated butterfly valves with metallic seats and metaloplastic bearings are used.

Valves for flashing of black liquor

These valves are mounted onto flanges mounted directly onto the flash tanks. When sizing the valves it must be taken into consideration that the medium is in a two-phase condition. I.e. a mixture of black liquor and steam. The flow to each tank is often split up to 25% through one valve and 75% through the other to be able to handle fluctuations at start up etc. For handling the liquid direct from the digesters the NAF-Duball full-bore ball valve with stellite seat rings is often selected. The NAF-Torex metal seated butterfly valves with metallic seats are often used for the liquid between the tanks.

The blow valve

Controls the level in the digester and works under very harsh conditions. The pressure drops can be very high combined with high temperatures. The pulp contains knots and stones which result in high wear in the valves severely reducing the life. NAF-Duball full-bore ball valves with cylindrical bore and locked stellite seat rings are used. Stellited outlet or ceramic sleeves can prolong the life-time.

Bleaching plant

In modern bleaching plants the control valves may be mounted directly on the mixing pumps. In most cases Richter fully lined valves would be the preferred choice. Should special alloy valves be required then the NAF-Setball ball sector valve would be supplied in titanium or another special alloy so it can be used for Chlorine service.

Evaporation plant

The black liquor is basically waste liquor from the digester and other processes. It´s a combination of lignin, spent chemicals and water. The black liquor prior to evaporation can be handled with the NAF-Torex metal seated butterfly valves. Liquid leaving the evaporation section can have a high solid content up to 70% combined with salt cake and sulphur. Here the NAF-Duball full-bore ball valves with locked stellite seats is often selected. The NAF-Torex metal seated butterfly valves can be used for control service with solids.

White liquor preparation

Here you find very erosive valve services. NAF-Setball ball sector valve with stellite seats are often used for green liquor. For unclarified green liquor and lime sludge, NAF-Duball full-bore ball valves with stellite ball and seat may be required. Lime mud control is one of the most erosive services. A NAF-Duball full-bore ball valves with ceramic lining could be used here.

Rotary Valve selection for Mechanical Pulp

Most applications for mechanical pulping are not subject to the demanding fluids and environment encountered in chemical pulping. Two valve types namely the NAF-Torex metal seated butterfly valve and the NAF-Setball ball sector valve will suit the majority of the applications. NAF-Torex metal seated butterfly valve do an excellent job in steam control as well as on-off and isolation. The consistency of pulp is one criterion in valve selection. Shut-off valves for pulp concentrations of 5% or more should be the NAF-Duball full-bore ball valves. In control duty, the NAF-Setball ball sector valve is the ideal choice. This valve type gives the optimal trim form to avoid clogging and dewatering of the pulp. If the flowing media includes chips, stones or similar items, the use of metal seated valves is common.

Valve selection for special applications

When the throttling differential pressure is high, i.e. for pressure control in (C)TMP-refiners, low noise ball valves are recommended. NAF-Trimball provides gradual pressure reduction which solves many of the problems with noise, cavitation and erosion.

Rotary Valve selection for Paper Making

Valve selection in general for Paper Making

The majority of paper mill applications are not subject to the demanding fluids and environment encountered in pulp mills. Two valve types namely the NAF-Torex metal seated butterfly valve and the NAF-Setball ball sector valve will suit the majority of paper mill applications, including steam. Paper mills can make remarkable savings in their valve selection by concentrating on these two types and use the same type of actuators and positioners on all valves. When the throttling differential pressure is high, low-noise ball valves are recommended. The NAF-Trimsector ball sector control valve and NAF-Trimball ball control valve provides gradual pressure reduction which solves many of the problems with noise, cavitation and erosion.

Valve selection for special applications

The stock preparation process includes several consistency control loops with water dilution valves. A perfect application for the NAF-Setball ball sector valve. In many cases the final furnish of the paper machine is a mix of different pulps. They are mixed in a stock blending system, where the flow of each pulp line is controlled by ratio controllers. This control loop requires high repeatability and accuracy - another perfect application for the NAF-Setball ball sector valve.

In vacuum service, line dimensions are large and a NAF-Torex butterfly valve is the most economical final control element. The same applies to large sizes in screening, centric leaning and where the stock consistency is below 5%. NAF-Torex butterfly valves can also be used for shut-off and control of steam.The demands of basis weight control are so critical that in most cases pneumatic actuators and positioners do not provide the accuracy needed. For this important control loop a step motor driven special designed actuator in combination with a NAF-Setball ball sector valve is recommended. This combination offers high accuracy and movements without hysteresis.

Careful consideration must be given to valve selection for additives used in the paper production. Fillers, like clay, cause wear and erosion. These services require a hard-facing option for NAF-Setball ball sector valve or valves with ceramic inserts. When designing these control loops the differential pressure and the flow velocity should be kept low.

Knife Gate Valve selection for Pulp & Paper in General


Pulp Mill (Digestion, Recovery, Bleaching, Causticizing)

Position / Media / Mill Section Conc./ Others ManualOn/OffV&A Solution
SeriesType
Alkaline Nearalization Reacot (Sulphite) Stafsjö HG Knife gate valve
Blow Pit Stafsjö MV Knife gate valve
Wood Chips Stafsjö HG Knife gate valve
Digester Tailings-Knotter/Rejects Stafsjö HG Knife gate valve
Brown Stock7-17% Stafsjö HG Knife gate valve
Stock1-7% Stafsjö MV / HG Knife gate valves
Black Liquor Stafsjö MV Knife gate valve
Turpentine Stafsjö HG Knife gate valve
Flyash (Dry) Stafsjö SLV Knife gate valve
Green Liqour Stafsjö HG Knife gate valve
Green Liqour Dregs Stafsjö HG Knife gate valve
Dry Lime Stafsjö RKO Knife gate valve
Slaker Stafsjö HG Knife gate valve
Lime Mud Slurry Stafsjö HG Knife gate valve
White liquor Stafsjö HG Knife gate valve
MC Stock from Storage to Bleach Tower Stafsjö HG Knife gate valve
MC Stock to Upflow Tower Stafsjö HG Knife gate valve
MC Stock Storage Stafsjö HG Knife gate valve

Paper Mill (Coating Kitchen, Stock Prep, Paper Machine)

Position / Media / Mill Section Conc./ Others ManualOn/OffV&A Solution
SeriesType
Stock Prep5-17% Stafsjö HG Knife gate valve
Stock0-5% Stafsjö MV Knife gate valve
White Water Stafsjö MV Knife gate valve

Recycled Paper & Miscellaneous Applications

Position / Media / Mill Section Conc./ Others ManualOn/OffV&A Solution
SeriesType
Hydropulper Rejects Stafsjö HG HG /RKO Knife gate valves
HD Cleaners Stafsjö HG HG /RKO Knife gate valves