There is the possibility of offering valves practically with every fitting. In case of non standard fixtures, there is a possibility of preparing a special offer, after prior confirmation and determining of the availability of required equipment on the Polish market.

All the dimensions of the manufactured by us valves are given in the cards of the valves on the website accessible via the page “OFFER”.  In some cases, there is a possibility of offering other valves dimensions after prior agreement with the producer.

In the absence of information about valve number or in case when a valve was produced before 2004, the following information must be given:

• Type of valve, diameter DN and nominal pressure PN,
• For heads Kvs shall be given as well as the sort of characteristics, material,
• For valve seats Kvs shall be given and material,
• For valve stems: Kvs, type of gland, type of actuator and material,
• For seals: factor and temperature shall be given.

For the selection of a valve, the following information shall be provided:

• the pressure before the valve p1,
• the pressure beside the valve p2,
• flow,
• media,
• temperature of the medium (preferably measured at 3 points).

Additional data which will facilitate the submission of an offer are as follows:

• type of actuator,
• type of valve fittings,
• the diameter of pipeline,
• fixtures,
• ambient temperature.

To send RFQ please, use this form.

The design version aspect applies only to valves.
Valves can be subdivided using the following criteria:

a) position of body inlet and outlet
• globe,
• three-way,
• angle,

b) closing component
• with linear motion valve plug,
• with rotary motion valve plug,

c) shape of closing component
• profile valve plug,
• perforated valve plug,
• multi-stage valve plug,
• cage valve plug,

d) balancing of axial forces
• unbalanced,
• balanced,

e) reversibility of operation
• reversible design double-ported valves,
• irreversible design single-ported valves.

Globe valves with linear situation of input and output are the basic, most common group of valves. Three-way valves are used in installations where mixing or separation of fluid is required. Angle valves are preferred option in applications where flashing (evaporation) and large pressure drops occur. A variation of angle valves are „Z” valves, with parallel but not axial body ends.

Rotary plug globe valves are recommended in cases of large flows and demand for precise adjustment in the beginning of opening. Perforated (perforated) components are used mostly to reduce noise emissions. Multi-stage valve plugs reduce cavitation and choked flow.

In cage valves there is a piston valve plug, working with perforated control cage. They are used for large pressure drops applications.

Pressure balancing of valve aims at equalization of static pressure on both sides of valve plug, by means of balance holes or internal valve plug (pilot).

For selection of the valve balancing method the following factors must be taken into account:
a) plug - pilot
- flow direction - above the plug (Flow To Close - FTC),  
- high leakage class - (V class),
- enhanced rangeability, 
- limited possibility to manufacture two-stage plugs to apply throttling cages.
b) balancing and relieving holes in the plug
- flow direction under the plug (Flow To Open - FTO),  - max. leakage class (IV class),
- plug sealing subjects to wearing - it must be replaceable,  - possibility to manufacture multi-stage plugs to and apply throttling cages.
Reversibility of valve operation denotes possibility of changing its function (pressing the valve plug stem can cause opening or closing of valve) in the consequence of different assembly of valve internal parts.
While selecting valve design one should consider the following aspects:
• leakage class
Single-ported valves are more tight than double-ported ones.
• balancing of axial forces
Double-ported valves require smaller resetting forces and allow transferring of larger pressure drops than in the case of single-ported valves with same actuators.
• flow coefficient
Single-ported valves feature better possibility of flow reduction, whereas double-ported valves and rotary plug valves feature better flow coefficients than single-ported ones, with same valve diameter.
• nominal pressure
Irreversible valves are used in applications with higher nominal pressure than in the case of reversible valves.
• fluid viscosity

It is recommended, that single-ported valves are used with dense fluids, with viscosity v>10-5 [m²/s], where laminar flow may be observed.

Material execution is determined by material in which body is executed.
Basic material executions of the body casts:

• cast iron:       

EN-GJL 250,    per PN-EN 1561

• spheroidal iron: 

EN-GJS-400-15,   per PN-EN 1563
EN-GJS-400-18LT,   per PN-EN 1563

• carbon steel:     

GP240GH, (1.0619),  per PN-EN 10213-2
G20Mn5, (1.6220)  wg PN-EN 10213-3
WCB,    per ASTM A216

• alloy steel:        

G17CrMo9-10, (1.7379), per PN-EN 10213-2
WC9,    per ASTM A217

• stainless steel:   

GX5CrNiMo19-11-2, (1.4408), per PN-EN 10213-4
CF8M,    per ASTM A351

Criteria for selection of material:

•  corrosion proofness,
•  working temperature,
•  nominal pressure,
•  requirements of technical specifications (AD 2000 Merkblatt, WUDT-UC, ASME Code)

Material corrosion proofness depends on type of fluid, its temperature, concentration, etc. It is to be assessed base don generally available tables and recommendations, or information by valve manufacturer. Relationship between working temperature and pressure are illustrated in tables in catalog product charts. Minimum operating temperature for all materials is -10°C.

There is a possibility of lowering operating temperature, as below:
  - 40°C   for spheroidal irons, EN-GJS-400-18LT,
  - 60°C   for carbon steels, GP240GH, (1.0619) i WCB,
  - 90°C   for carbon steels G20Mn5, (1.6220),
  -196 °C  for stainless steels, GX5CrNiMo19-11-2, (1.4408) i CF8M, provided that:

• design pressure is reduced respectively,

• results of impact strength tests at working temperature are positive,

• heat treatment (stress relieving) of casting is performed.

Requirements of AD 2000 Merkblatt specification, sheet A4, do not allow pressure equipment execution in grey iron, with exception of products executed under Article 3.3 of Pressure Equipment Directive in accordance with Technical Specification WUDT-UC.

Nominal pressure is a dimensionless marking of maximum operating pressure at ambient temperature, preceded with PN or CL symbol.

Control valves are executed in following nominal pressures:

PN6; 10; 16; 25; 40; 63; 100; 160; 250; 320; 400  per PN-EN 1092-1, DIN2548, DIN2549, DIN2550,
                                                                                DIN2551, PN-H-74306, PN-H-74307
CL150; 300; 600; 900; 1500; 2500                         per ANSI/ASME B16.5, PN-EN 1759-1
PN20; 50; 110; 150; 260; 420                                 per PN-EN 1759-1, PN-ISO 7005-1

Pressures PN20…420 are equivalent to CL150…2500.

Flow coefficient Kv is the stream of water in [m³/h], with temperature 5°C to 40°C, flowing through the valve, at pressure drop 1 [bar], for specific stroke of valve.

Kv coefficient describes minimum hydraulic resistance of valve. Familiarity with Kv coefficient allows to directly determine valve nominal size DN and diameter of pipe the valve is to be connected to.

Many different Kv values can be obtained for same nominal sizes DN, in the consequence of application of reduced passages of valve seats. Nominal (catalog) value of flow coefficient is marked Kvs.

Relationships between flow coefficient, flow rate and pressure drop for various states of aggregation and flow conditions can be determined using formulas on page 5.

Said formulas allow approximation of Kv coefficient. They however do not account for effects of fluid viscosity, change in density of flowing fluid, critical flow, etc. For more details refer to PN-EN 60534-2-1 “Industrial-process control valves. Flow capacity-sizing equations for fluid flow under installed conditions.

It is advised that DIVENT valve calculation and calculation program is used, which can be downloaded from the following website
www.polna.com.pl

To ensure correct work of automatic controls and to avoid oversizing of the valve, adopted catalog value of flow coefficient is to be higher than calculated. It is assumed that maximum value of calculated flow coefficient is to be achieved within the 70…90% range of valve plug stroke.

Valve flow characteristics is the relation between flow value and closing component stroke. Regarding pressure drop we can divide characteristics into internal and working characteristics.
Internal characteristics describes relation between relative flow coefficient “kv” and relative stroke “h” at constant pressure drop in valve, where:

Working characteristic describes change in flow in function of stroke at variable pressure drop in valve, in installation conditions.

Valves have the following flow characteristics:
• linear    - „L”
• equal percentage - „P”
• modified  - „M”
• quick opening  - „S”

Valve characteristic is obtained by proper design of fluid flow area between valve choking components regarding the stroke. This function is realized through contoured valve plugs or perforated components (perforated valve plugs, control cages):

• linear characteristic: equal increase in relative stroke “h” correspond with equal increase in relative flow coefficient “kv”.

where: k_v0 - is a minimum controlled relative flow ratio,

m - characteristic inclination

For POLNA valves: kv0 = 0,02; m = 1

• qual percentage characteristic: equal increase in relative stroke “h” corresponds with equal per cent increase in relative flow coefficient „kv”

where: n is characteristic inclination drawn in semi-logarithmic coordinates (h, lg kv).

• modified characteristic: is a characteristics in between “L” and “P”, created for individual needs and specific installations. It mostly is of equal percentage nature at the beginning of stroke (h=0…0.3) and linear in the subsequent part of stroke.

• quick opening characteristic: used for “open-close” on-off operation; it allows achievement of nominal flow at low stroke (h=0.6…0.7) and increase in flow coefficient by ca. 20% regarding catalog value, at full stroke.

Selection between value with equal percentage and linear characteristics depends on requirements concerning changes in flow rate and pressure on valve.

With small changes in flow rate during valve operation, up to 50%, selection of characteristics has no material effect to performance of control system. However for valves operating at large changes in flow rate, with variable pressure drop, and in case of doubt selection of constant per cent characteristics is recommended.

Valves with linear characteristics are recommended for systems, where pressure drop on valve is independent from flow rate, e.g. control of fluid level.

Valve plugs with quick opening characteristics are designated exclusively for on-off operation.

Limitations in application of perforated components are due to their susceptibility to contaminants suspended in fluids, hence the need for their permanent filtering.

Three way and rotary valve plug valves feature linear characteristics, whereas butterfly valves feature characteristics similar to equal percentage characteristics in the range of opening angles 0°…60°    (Fig.  2).

Checking the internal tightness is carried out as part of acceptance tests of the product with the use of air with pressure 3…4 [bar] (for valves in classes II, IV and VI) and with water with working pressure conforming to the order (for valves in class V).

Valves in class VI have seats (single-seat valves) or plugs (two-seat valves) equipped with packing rings made of PTFE reinforced with glass fibre.

Because of durability of the packing material, pressure drop on the valve must not exceed 35 bar.

Valves in class V require careful and laborious fitting of closing elements and a greater disposition force of the drive.

Another acceptance criterion is the norm PN-EN 12266-1 “Industrial valves. Testing of metallic valves. Part 1: Pressure tests, test procedures and acceptance criteria. Mandatory requirements.”

The following can be used as test media:

• Air  (for pressure  6 bar),
• Water   (for pressures  1,1 • Dpmax.).

where: Dp [bar]   -  working pressure drop
D [mm]   -  valve seat diameter

Internal tightness is checked during acceptance tests, using air at pressure 3…4 [bar] for valves of class II, IV, VI, and using water at working pressure as per order, for valves of class V.

Class VI valves valve seats (single-ported valves) or valve plugs (double-ported valves) are equipped with PTFE seal ring reinforced with glass fiber. Due to durability of sealing material pressure drop on valve cannot exceed 35 bar.

Class V valves require precise and time-consuming fitting of valve closing components and higher available force of drive.

Bonnet is a pressure equipment used to contain and seal the component (valve plug stem, shaft) transmitting motion from drive to closing component.
Bonnet can be integral part of body or be separated from body.
Control valves are fitted with following types of bonnets:

• standard bonnet
• extension bonnet
• bellow seal bonnet

The basic criterion in selection of bonnet is fluid temperature. Extension bonnets are used in both high and low temperatures. There is a execution of extension bonnet specially designed for cryogenics (temperatures up to -196°C).

Bellow seal bonnets ensure absolute internal tightness and they are used mostly for aggressive media. Standard bellow seal bonnets can be used up to pressure 35 bar. Application for higher pressures require to use multi-layer bellows.

Cast iron valves are only fitted with standard bonnet. Control valves DN150…250, PN160…CL2500 can be equipped with self-sealing bonnets. Type of valve plug stem packing in bonnet depends on temperature and type of fluid. In majority of cases PTFE rings with graphite are applied. Pure graphite packing is recommended for steam and high temperature operations. Such packing does not require lubrication, although they do require adjustment during operation, due to relaxation and wearing-off.
Among maintenance-free packings are PTFE-V and TA Luft packings. PTFE-V ones are executed in PTFE in the form of V-profile rings, pressed to sealed surfaces with spiral spring. TA Luft packing comprises two kits of seal rings loaded with package of disk springs, and compliant in terms of tightness requirements of TA Luft:2002, Clause 5.2.6.4, and VDI 2440:2000.

Body connections are used to connect valve to pipeline and they should provide tightness, pressure resistance, vibration resistance and pipeline deformations.Valves are executed with following types of connections:

•     flanged,
•     flangeless,
•     welding.

Flanged connections are executed as per European (PN-EN 1092-1, PN-EN 1092-2, PN-EN 1759-1, DIN 2548, DIN 2549, DIN 2550, DIN 2551, PN-ISO 7005-1, PN-H-74306, PN-H-74307) and American
(ANSI/ASME B16.5) standards.

Regarding sealing surface type flanges can be executed with:

•     raised face type B1, B2, B, RF
•     groove, type D, D1, GF, DL
•     recess type F, F1, FF
•     ring-joint, type J, RTJ

Rotary plug valves and butterfly valves have flangeless connections of Sandwich type. Body is fitted between pipeline counter-flanges by means of bolted ends.

Valves with welding connections are designed for butt welding, BW type, or socket welding, SW type. Pipe dimensions and body lengths specified in catalog apply to execution of connections from body casting. Application of smaller pipe dimensions is limited due to minimum internal diameter of pipe that can be achieved from casting (D1 min). In such case reduction stub is to be welded to body, which shall cause elongation of valve body by 100 mm (DN15…50), 150 mm (DN80, 100), 200 mm (DN150) and 300 mm (DN200, 250) – in case of stubs fixed on both sides of the valve.

In standard execution valve internal parts: valve plugs, valve seats, valve plug stems, cages, guiding sleeves are executed in high-alloy austenitic steel X6CrNiMoTi 17-12-2 (1.4571) as per PN-EN 10088-1.

In order to improve mechanical and chemical resistance to fluid the following hardening methods of internal parts are used: stelliting, nitriding, heat treatment, protective coatings.

Stelliting hardens the surface down to ca. 1 mm, to hardness of ca. 40 HRC. Stelliting can be applied to sealing phases of valve plug and valve seat, or additionally valve plug trim surfaces, openings of valve seats and guiding sleeves, valve plug stem friction surfaces.

Plugs with the diameter smaller than 10mm can be made of solid stellite.

Nitriding (CrN) consists in hardening of component surfaces down to ca. 0.1 mm, to hardness of ca. 900HV, in the effect of plasma or diffusion processes. Nitriding is recommended for application with surfaces exposed to friction or erosion. Heat treatment is applied in order to achieve high durability and resistance to wear. Depending on the material type hardness achieved is up to 45 HRC (1.4057) or 55 HRC (1.4125).

Composite protecting coatings (BELZONA) are applied on body internal surfaces in order to protect them from erosion (flashing, abrasive fluids).

Hardening of valve internal parts is recommended in the following cases:

• handling of erosive fluids,
• wet gas or saturated steam,
• dry, pure gas
• (Dp> 25 bar (up to DN100), Dp> 12 bar (DN>100)),
• chocked flow,
• initial cavitation: (liquid Dp> 10 bar, temp. > 315°C).

Contraindications for stelliting

• boiler water pre-treated with hydrazine,
• perforated components,
   

Valves and butterfly valves can be equipped with spring diaphragm pneumatic actuator, piston actuator, electric actuator, electro-hydraulic actuator, handwhell, or no drive at all.
Equipment without drives can be completed by end user with other types of actuators, such as springless diaphragm pneumatic, piston pneumatic acutator, crank actuator, and others, provided that such actuators are adapted to connection with valve bonnet and valve plug stem.
Hand operated equipment is mostly used for applications requiring on-off regulation.
While selecting spring diaphragm pneumatic actuator the following is to be determined:

• actuator type,
• actuator size,
• spring range,
• supply pressure,
• stroke,
• requirements concerning accessories.

Selection of pneumatic actuator (whether direct or reverse action) depends on equipment operation control signal failure. Whether the valve is to stay open or closed on control signal failure is the technical requirement of installation.
Actuator size, spring range and supply pressure are to be taken from tables in catalog, depending on required available force of actuator. Available force of actuator is to be lower than Fs calculated using the below formula:

where: Fs [kN] - available force
Dp [bar] - pressure drop on closed valve
D [mm] - valve seat diameter
Fd [kN] - tightening force
 

Values D and Fd are to be taken from catalog charts, and Δp from order.

Disposition force of type „P” actuators - F_SP [kN] is dependent on the active flank of the actuator A [cm²], supply pressure pZ [kPa] and the final spring travel p₂ [kPa].
 

Disposition force of type “R” actuators – F_^SR [kN]  is dependent on the active flank of the actuator A [cm²] and the initial spring travel p1 [kPa].

Disposition forces  F_SP and F_SR calculated that way are established without consideration of friction force of movable elements (spindle of the actuator and the valve) or tolerances of spring manufactures, hence they should be treated with a 20% reserve regarding those factors.

The calculations refer to single-seat valves type Z, Z1A and Z1B in a closed position.

Catalog charts provide allowable pressure drops for various pneumatic actuators and various internal leakage classes of valves.
Those values apply to single-ported valves, unbalanced, with fluid fed under the valve plug (FTO).

With fluid fed above the valve plug (FTC) allowable pressure drop may be higher, however such an arrangement causes valve plug hitting the valve seat when closing and disturbances to control. Hence it is used mostly in on-off operations, with actuator equipped with higher stiffness springs. For valves with valve plug unbalanced it is assumed that available force Fs is at least equal to tightening force for class V leakage.

In the case of double-ported valves it is not possible to procure a table of allowable pressure drops, due to dynamic forces occurring, which depend on i.a. actual flow conditions (pressure, fluid type, valve plug type, valve operation type). In case when knowledge of forces acting on double-ported valve plug stem is required, please contact manufacturer, stating all the data related to valve operation.

Pneumatic actuator accessories may comprise the following:

• top-mounted or side-mounted handwheel,
• positioner: pneumatic, electro-pneumatic with analog or digital signal (smart positioner),
• air set,
• three-way solenoid valve,
• position transmitter,
• limit switches,
• lock-up valve,
• volume booster,
• quick exhaust valve.

Handwheel is applied in case of control signal failure, as well as to limit valve stroke.

Application of positioners is recommended in following cases:

• for systems requiring large pressure drops on valve,
• for high working pressure,
• for valves of nominal diameter DN > 100 mm,
• for distance between valve and reducing valve exceeding 50 m,
• for three-way valves,
• for systems requiring high-speed action,
• for viscous or highly contaminated fluids sedimenting on valve seat,
• for media of temperature higher than 250°C or lower than -20°C,
• when spring range does not correspond with range of out signal from controller.

Designation of accessories:

• filter reductor is used to reduce supplying pressure to required value and to clean incoming air.
• solenoid valve assists remote switching of control circuit on and off.
• position transmitter is used to reflect position of valve plug stem in the form of unified pneumatic (e.g. 20…100 kPa) or electric (e.g. 4…20 mA) signal.
• limit switches are used to signal preset positions of actuator stem.
• lock-up valve is used to block valve plug stem movement in current position with control signal missing.
• volume booster is used to accelerate actuator time of action.
• quick drain valve allows to reduce actuator chamber drainage time.

The flow of medium through the valve (depending on the kind and parameters of the medium) may cause phenomena having a negative impact on the environment and be destructive to the product’s durability.

Risk factors should be diagnosed in detail in order to be used for actions aimed at limiting or eliminating their negative influence.
Harmful phenomena connected with the flow include the following factors:

• Noise
• Cavitation
• Evaporating (flashing)
• Choked flow

The conditions in which the above-mentioned phenomena occur are explained by the following graphs:

where:
p1  - pressure before the valve,
p2  - pressure after the valve,
pvc - pressure in the “vena contracta” zone,
pv  - pressure of evaporating.

Medium flowing through valve shall invariably cause noise.

Adverse effect of noise is due to its harmful effect to health and working environment. Noise is also the symptom of processes inside the valve, generally reducing durability of appliance, including damage.

Noise level is measured in [dBA] units, 1 m from the pipeline surface and valve axis, in the direction to medium outlet.
Human ear is most sensitive to frequencies 3000 to 4000 Hz. Allowable workplace noise level depends on duration of exposure. For continuous work it is 85 dB(A), for short exposures, say 15 minutes a day, it is up to 115 dB(A). 3 dB(A) difference means double increase in noise level; hence two appliances generating 82 dB(A) are equivalent to one appliance generating 85 dB(A). Noise level drops by 3 dB(A) with each doubling of distance from pipeline.

Sources of valve noise emissions may be as follows:

• mechanic noise,
• aerodynamic noise,
• hydrodynamic noise.

Mechanic noise may be caused by vibrations of valve internal parts, resonance, misguiding of moving parts, excessive clearance. One of the methods to eliminate such noise is application of cage construction and selection of proper clearances to valve working conditions.

In Fig. 1 a valve is shown designated for operation at temperatures up to 500°C, with possibility of thermal shocks. Valve plug is guided in valve seat and in cage. Application of steel spring ring allows increase of clearance between valve plug and cage without causing vibrations and loss of tightness. Mechanic vibrations can also be reduced through change in valve plug weight and direction of medium flow.

Aerodynamic noise is generated when mechanic energy of compressible medium flow is transformed to acoustic energy. Source of noise is increase in flow speed due to medium decompression, often exceeding speed of sound.
Noise reduction can be achieved by means of using proper installation (insulation on outlet pipeline, increased thickness of pipeline walls), or by means of selecting proper valve construction. The most important and most efficient way is to apply in valve perforated control structures in the form of perforated valve plugs (Fig. 2) or cages (Fig. 3).

Splitting of a single stream to multitude of smaller, well adjusted streams, causes reduction in noise emission as high as by 10 dB(A), due to following:

• reduction in efficiency of mechanic to acoustic energy transformation,
• smaller spin causes generation of higher frequency energy, which is easier to damp by walls and insulation,
• high frequency sound (> 10 000 Hz) is less harmful to human ears.

Another way of reducing aerodynamic noise (by ca. 5 dBA) is reduction in medium outflow speed at outlet. The most common method of doing so is increasing the outlet pressure by application of choking structures in the form of perforated cages and plates, and application of diffusers. In cases of high noise level it is often necessary to apply all those solutions at the same time (Fig. 4).

Hydrodynamic noise is generated by flow of fluids, and its sources can be as follows:

• turbulent flow interacting with valve and pipeline walls,
• cavitation,
• evaporation (flashing).

Cavitation consists in local, usually in vena contracta area, evaporation of fluid due to pressure drop below evaporation pressure pv. Then, due to valve outlet pressure increase to value p2 > pv, implosion of generated steam bubbles occurs. In addition to noise, such a phenomenon features sudden accelerations and blows of two-phase mixture (fluid-steam), and resulting damages (Fig. 5) to valve or pipeline surfaces.

Should outlet pressure stay lower than evaporation pressure (p2 < pv) fluid is permanently turned to mixture of fluid and steam, with steam share depending on pressure and temperature. This phenomenon is called evaporation (flashing).

Then  sudden increase in flow volume and speed occurs. Mixture stream erodes internal valve surfaces (Fig. 6) and pipeline, and is the source of noise as well. The most harmful phenomenon is however cavitation. Its effect can be reduced by means of application of proper materials and surface hardening technologies on one hand, and application of design methods for elimination or controlling of cavitation on the other hand.

Another proven methods are: improving valve plug and valve seat durability by stelliting their phases or whole trims, diffusion or plasma nitriding, allowing achievement of surface hardness 950 HV to the depth of ca.0.1 mm, or through hot-setting to hardness 55 HRC. The basic design solution of anti-cavitation valves is execution with multi-stage valve plug (Fig. 7). The concept behind that solution is possibility of achieving pressure drops on each stage below critical value. It is however difficult to achieve effective choking on individual stages at the beginning of valve opening. In such cases we use contoured and perforated multi-stage valve plugs, with active structures which  resistance depends on valve opening, and passive structures, in the  form of cages and perforated plates (Fig. 8).

Although occurrence of flashing depends only on flow parameters, and cannot be eliminated through design changes, its damaging effects can - and have to – be eliminated. In addition to above discussed methods of improving durability of valve components, POLNA offers also application of hardening coatings on internal valve body surfaces, and application of valves fitted with anti-corrosion bushing (Fig. 9); angle valves (Fig. 10); and valves with protective cage (Fig. 11).

All above noise reduction methods applied in control valves by Zakłady Automatyki POLNA SA in Przemysl, are tailored to Customers’ needs. We design our valves after thorough analysis of phenomena occurring in flow process, based on detailed data and using specialized computer software DiVent and CONVAL®. Not only do our designs meet all standards, but also they solve problems the Customer’s are unaware of.

CONVAL® software has a Polish version, made by our own company, and contains data about the POLNA product offer.

Fluid flow ratio regulation appliances, which keep the required regulation characteristics, are critical in industrial automatics systems.

The main component of such appliances are controllers, which adjust the resistance for flowing fluid, and drives (actuators), which provide mechanic energy required in setting of controllers.

The following are representatives of this group of appliances, manufactured by Zakłady Automatyki  POLNA SA:

• globe and angle control valves,
• three-way control valves,
• butterfly valves.
• Regarding the type of drive, controllers are manufactured in following executions:
• with spring diaphragm pneumatic actuators,
• with electric and electro-hydraulic actuators,
• with pneumatic piston actuators,
• with hand operated drive,
• without drive.

Regarding the fact that valves are the largest group of controllers, the expression “valves” is hereinafter often interchangeable with expression “controllers”.

While selecting valves for specific working conditions one should consider the following aspects:

• valve design version,
• material execution,
• nominal pressure,
• flow coefficient,
• flow characteristics,
• internal tightness,
• bonnet type and packing,
• body connection types,
• hardening of valve internal parts,
• selection of drive,
• harmful effects in valve operation.