flowserve 2 control valve actuators 2.2 selection of control valve

Selection and sizing of control valves Page2/1

VHB2_Actuators.doc/05.02.09/AMU Flowserve Villach Operation

2 Control valve actuators

2.2 Selection of control valve actuators The selection of an appropriate valve actuator depends on technical and economical factors. Manual control, external piloting, or internal piloting is possible. Usually control valves are operated with pneumatic diaphragm actuators, pneumatic piston actuators, electrical linear actuators and electrical rotary actuators. Electro-hydraulic actuators are used sometimes. Actuator type Advantages Disadvantages Pneumatic Explosion-proof, relatively simple

Relatively insensitive to corroding environments if control air is used Unsophisticated design Use of control gas possible Interlocking of signals can easily be achieved Relatively low costs High stroking velocities can be achieved In case of an auxiliary energy failure, safety position occurs (spring-loaded design)

Distance to the source of energy is limited (dead time!) Actuating force for spring-loaded units is limited Auxiliary energy must be generated, not available (costs!) Auxiliary energy system requires maintenance Small systems are normally not economical Sensitive to changing process pressure

Electric Large distance to the source of energy, easily to compensate Accessories and parts are standard supplies Easy interlocking of signals High operating and controlling accuracy- easy to achieve Large actuating force- easy to achieve Remote control and monitoring functions can be implemented easily

Larger actuating forces difficult to achieveLimited stroking velocity compared to pneumatic or hydraulic actuators; Explosion-proof difficult Safety position: in case of an auxiliary energy failure, additional measures are required High maintenance costs

Hydraulic High actuating forces High stroking velocities are possible In case of an auxiliary energy failure, safety position occurs (accumulator) High stability

Distance to the source of energy is limitedTransferring actuating power requires pipes (leakage risks!) Costly control and operating Maintenance required

Table 2/1: Advantages and disadvantages of different control valve actuator series



2.2 Manual actuation Manual actuation for control valves If there is no auxiliary energy available, the closure element is moved by means of a trapezoidal threaded spindle (generally using a hand wheel) to achieve an accurate flow. Larger actuating forces require transmission by means of gearing.

Figure2/1: Manual actuation for control valves

A coupling transforms the actuating forces to the valve’s stem. A screw safety device prevents, that the sealing areas between plug and seat do not abrasive, in case of rotation. The maximum permitted operating force should not be ignored because operating differential pressures are limited. Permitted manual forces for operating industrial valves, according to EN 12570 1.

1 EN 12570: Industriearmaturen; Verfahren für die Auslegung des Betätigungselementes



2.3 Pneumatic operating actuators For installation on control valves pneumatic operating actuators is the most popular type in use on/off valves and control valves. Pneumatic operating actuators are advantageous because they are explosion proof and have a simple design. Pneumatic diaphragm actuators Pneumatic diaphragm actuators are designed as single acting multi-spring actuators, central-spring actuators or double acting actuators. Pneumatic diaphragm actuators operate by means of a controller signal, the positioner or another source. Because of different spring ranges, diaphragm areas and the various accessories cover a very large application range.

Figure 2/2: Single-seat control valve with a standard bonnet and a pneumatic multi-spring diaphragm actuator FlowTop and FlowAct Series

Advantageous of a pneumatic diaphragm actuator: Robust and reliable Temperature resistant to a large extent Rapid positioning time In case of an auxiliary energy failure, safety positions react immediately (open/close function). Operates in intrinsically safe and explosion proof areas (EEx). Easy maintenance Simple mechanic construction- inexpensive



Flexible, pre-formed diaphragms (roll diaphragms) made from reinforced elastomer materials are used to achieve higher strokes, vast linear actuator characteristics and negligible low friction force. The diaphragm material dominates the permitted surrounding temperatures. Because of the normally used Acrylnitril-Butadien-Rubber (NBR), temperatures reach -40°C to 80°C. Below -40°C, the actuators require diaphragms made from silicon. Disadvantageous are the limited positioning forces of spring loaded actuators and that the air pipe distance regarding the energy source is limited. Another disadvantage is the complex construction and the supply of auxiliary energy. Single acting actuators In pneumatic diaphragm actuators, the diaphragm operates in means by pneumatic signals. A retracting or an extending of the actuator stem occurs, when the diaphragm force is larger than the installed actuator spring. The spring returns to its starting position in case of a signal failure (safety position of valves). A huge advantage of single-acting actuators is the construction-conditioned safety position. The spring force and the number of springs are defined by the existing additional air pressure. A central-spring actuator has an adjustable spring (To vary the positioning force and the spring range) and a double guided actuator stem. The double guided stem makes a reversing of the effective direction without a reconstructing of the actuator possible. Diaphragm actuators are designed as multi-spring actuators because of costs and height.

Figure 2/3: Central-spring actuator effective direction; stem extended (Design Flowserve Villach, Series 151 PA 1000)

Upper or lateral manual operations are often attached to operate control valves in case of a pneumatic signal failure. Upper or lower stroke limitation is adjusted by manual operations.



Figure 2/4a and 2/4b: Pneumatic multi-spring diaphragm actuator with upper manual operation. Series: FlowAct Single acting linear actuators with gear box are also used for rotary valves. In this case a motion conversion mechanism between the valve and the pneumatic power unit is necessary to convert between linear and rotary motion.

Figure 2/5: Butterfly valve with gear box and pneumatic linear actuator Valve and gear box design Böhler (BHDT), actuator Series FlowAct



Double-acting actuators Both effective directions require auxiliary energy. A double acting actuator has no adjustable spring and therefore no constructive safety positioning.

Figure 2/6: Double-acting diaphragm actuator (design based on Series FlowAct)

Pneumatic piston actuators Pneumatic piston actuators are primarily designed for open/close functions. A piston sealing causes friction- hysteresis occurs. If enough additional air pressure is available, pneumatic piston actuators (compared to diaphragm actuators) can cope with higher positioning forces. Even if high strokes are demanded, pneumatic piston actuators are required. If a safety positioning is required, the pneumatic piston actuators are designed with actuator springs.

Figure 2/7a and 2/7b: Pneumatic spring cylinder actuator A: spring action close B: spring action open Type: Valtek VL Aluminium actuator



Figure 2/8: Pneumatic piston actuator with double pistons, double-acting (Design Flowserve Villach, Type KO 300-2)

Pneumatic rotary actuators Pneumatic operating rotary actuators are designed for rotary valves (ball valves, plug cock, butterfly control valve or rotary plug valve). In order to operate double-acting piston actuators, pneumatic rotary valves are predominately designed with an open/close function. If a safety positioning is required, pneumatic rotary actuators are even designed with an adjustable spring. The standard interface between valve and actuator, according to DIN ISO 5211. Typical designs are:

Rock and pinion actuator The linear motion of the pistons is transferred into pivoting by rock and pinion. The course of torque is linear.

Scotch yoke type actuator

The linear motion is transferred over an arrangement of levers into rotation. The gear ratio makes at the beginning and at the end a higher torque possible. This torque is ideal for valves with distinctive breakaway torque and for valves with a higher closing torque (e.g. ball valve, rotary plug valve).



Figure2/9: Pneumatic rotary actuator Type NORBRO

Diaphragm actuator with Gear box

Because of its low hysteresis, diaphragm actuators are preferred controlling functions.

Figure 2/10: Rotary plug valve with pneumatic diaphragm actuator Type Valtek MaxFlow



Energy supply Pneumatic actuators and the appropriate auxiliary equipment operate only with pneumatic energy supply. Compressed air is normally used and provided by a compressor. The pressure supply must be higher than the minimum required pressure of any single equipment. If a high reliability of the systems (e.g. control loops with safety functions or a continuity of operating process) is required, an additional auxiliary supply source (besides the auxiliary equipment) is set up. This essential supply comes from a volume tank. The capacity of volume tanks must be measured carefully. Operating over a defined period of time must be assured when an energy supply failure occurs. According to the safety concept, the process must be in good order and condition. In case of an operating fault, this process must be guaranteed as well. In order to operate failure-free, most pneumatic additional equipment requires dry instrumental air. The instrumental air must be free from oil. The pneumatic supply must be free from impurity (e.g. solids, liquids, vapor or aggressive elements) otherwise the pneumatic equipment is damaged or its function is affected. Even a total breakdown cannot be excluded. A dust filter, smaller than 10 μm is required Free from oil In order to prevent an icing of the pneumatic equipment, the dew point of the air should stay about

10°C lower than the lowest surrounding temperature. Quality of the industrial plant air supply, according to: ISO 8573-12 .

2 ISO 8573 Teil 1: Druckluft; Verunreinigungen und Reinheitsklassen



2.4 Accessories for pneumatic actuators In order to meet the demands of functioning as a controlling or operating element, the valve and actuator unit require a device. Accessories influence the auxiliary power of the actuator and signal the stroke position of the actuator. Advantageous are actuators and pneumatic additional equipment with standardized connection possibilities according to IEC 60534-6-13, IEC 60534-6-24 (NAMUR), VDI/VDE 3845 5 or VDI/VDE 3847 6. An easy construction, without adapter parts for pneumatic additional equipment from different manufacturers is possible. It is advantageous to directly construct the positioner, solenoid valve or filter regulator with internal air ducts. Then, a demounting of pneumatic additional equipment without any additional air or instrumental air pipes can be guaranteed. Piping and screw connections can be dropped out, high reliability (because of possible leakage reduction) is assured.

Figure 2/11a, 2/11b and 2/11c: Pneumatic operated single-seat control valves A: NAMUR Interface (FlowPro with FlowAct size 700 and Logix 520) B: VDI/VDE3847 Interface (FlowTop with FlowAct size 252, direct mounted positioner Logix 520 and direct mounted filter regulator) C: FlowTop Interface (Flowtop with FlowAct size 252, top mounted hand wheel and Logix 520)

3 IEC 60534-6-1: Stellventile für die Prozessregelung; Montage-Einzelheiten zur Befestigung von Stellungsreglern an Stellventil-Antriebe; Montage von Stellungsreglern an Hubantriebe 4 IEC 60534-6-2: Stellventile für die Prozessregelung; Montage-Einzelheiten zur Befestigung von Stellungsreglern an Stellventil-Antriebe; Montage von Stellungsreglern an Schwenkantriebe 5 VDI/VDE 3845: Stellgeräte für strömende Stoffe; Verbindungsstellen zwischen Stellglied, Stellantrieb, Stellgeräte-Zubehör 6 VDI/VDE 3847: Stellgeräte für strömende Stoffe; Schnittstelle zwischen Stellgerät und Stellungsregler



The yoke from Flowserve Villach allows a directly setting up of the positioner, solenoid valves and filter regulators as a compact function unit with internal routing of air flow. A processing alternative would be an adapter with a standardized interface according to VDI/VDE 3847 and VDI/VDE 3845. Some designs allow conducting the discharged air of the pneumatic accessories into the spring room of the actuator. Air ventilation with instrumental air prevents humidity or aggressive surrounding air from entering the spring room (stroke is working). Valve positioners A positioner is used when the position of the plug must be proportional to the instrument signal of the controller. In case of controlling deviation, the positioner makes fast tracking possible. Stuffing box friction, forces on the plug or actuator and hysteresis are compensated.

Figure 2/12: Pneumatic scheme of a control valve system

The standardized signal for pneumatic performances averages 0,2 bar (20 kPa) to 1,0 bar (100 kPa). The standardized pressure supply is defined with 1,4 bar (140 kPa) and a minimal value of 1,3 bar (130 kPa). Actuators can achieve enormously high pressure levels with a positioner (compared to the standardized signal). A higher positioning force can be achieved with small diaphragm areas or piston areas. The control valves can also operate in Split-Range. There are single and double acting positioners for globe valves and rotary valves. Most positioners are equipped with inductive or mechanic limit switches, position transmitter (4 to 20 mA), booster relays or gauge. Pneumatic Positioner (P/P) The pneumatic positioner is used to operate pneumatic actuators by a pneumatic positioner with an input signal 0,2 - 1,0 bar (3 – 15 psi) or partitions. Maximum pressure supply 6 bar

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Analog electro-pneumatic Positioner (I/P) The electro-pneumatic positioner is used to control pneumatic actuators by a electric positioner or a control device with an input signal 0/4 - 20 mA or partitions (Split-Range Operating) User-defined characteristics intrinsically safe (EEx ia) or explosion proof (EEx d) Digital electro-pneumatic Positioner (D/P) Input signal 0/4 - 20 mA or Split Range Operating Micro-process controlled Self calibration Intrinsically safe (EEx ia) or explosion proof (EEx d)

Digital Positioner with micro processor Communicating positioners are used to control actuators through control systems and electrical controllers supported by HART-communication, FoxCom, Profibus PA or Foundation Fieldbus H1 (FF)

Figure 2/13: Electro-pneumatic positioner Type Foxboro/Eckardt SRD 986

Figure 2/14: Digital positioner Type Flowserve Logix 3200 IQ

Figure 2/15: Digital positioner Type Flowserve PMV D3



User-defined characteristics Status- and diagnostic feedback Intrinsically safe (EEx ia) or explosion proof (EEx d) Some manufacturers offer diagnostic possibilities in order to monitor the valve’s condition. Unexpected failures can be prevented. Diagnostic tests can be done offline or online, without any interruption of the process. Communicating positioners allow a remote diagnostic. Pneumatic booster relay

Figure 2/16: Pneumatic booster relay Type Valtek Flow Booster

The volume booster is mounted between positioner and actuator in order to increase the additional air flow for the actuator. Higher positioning speed occurs. Several actuators can work at the same time. Input- and output signal are equal in pressure. Position transmitter A position transmitter is used where a surveillance of the closure member’s position is required. The position transmitter signalizes the position of the control valve by an analogue electrical signal (4 - 20 mA) or a pneumatic signal (0,2 - 1,0 bar). Lock- up relay In case of pressure supply failure, a lock-up relay (safety element) closes the supply line to the actuator. The actuator remains in its last position. When the supply pressure is restored, the pneumatic control signal is released to the actuator again. Solenoid valve Solenoid valves are used to control pneumatic diaphragm actuators for open/close functions, to interlock or for safety circuit systems. Direct or indirect controlled 3/2-wege-solenoid valves are used for most applications.



The interface between actuator and solenoid valve is standardized: VDI/VDE 38457. Limit switch Limit switches are used for limit signals of one or two end positions. Inductive limit switches or micro switches are applied. Barrier Barrier for signal loops divide equipment. In explosive areas mounted equipment is divided from non- intrinsically safe controllers or other additional equipment. Filter regulator In order to protect pneumatic equipment, filter regulators are used to reduce the pressure of plant air supply.

Figure 2/17: Filter regulator Type Foxboro/Eckardt FRS 923

The pneumatic equipment is protected from incorrect high pressure. Solid particles which are larger than 3 μm or 5 μm and liquids are filtered out. The adjusted secondary pressure and the fluctuating inlet pressure stay constant.

7 VDI/VDE 3845: Stellgeräte für strömende Stoffe; Verbindungsstellen zwischen Stellglied, Stellantrieb, Stellgeräte-Zubehör



2.5 Electrical operating actuators Electrical operating actuators cope with high operating forces and dynamic forces. Electrical operating actuators cope where auxiliary energy is plant air supply or at low surrounding temperatures. Electrical operating actuators are required to dry instrumental air. The electric actuators are more complex and more expensive than pneumatic actuators. A disadvantage is that explosion protection can only be guaranteed under extraordinary charges. The positioning speed is relatively low. The actuators don’t operate appropriate at too high or too low temperatures and are sensitive to humidity and corrosion. Electrical operating actuators are not equipped with a safety position. The safety position can only be applied under extraordinary charges and works only with batteries. A disadvantage is the must of periodic maintenance and the recharging of the battery. Standard electric gear type actuators are ideal, when the valve must remain in the last operating position (fail-in-place mode). For fail-safe action a standby power source (e.g. a relay switch, actuated battery pack and a hand wheel for manual control) is required. Electric linear motion actuators Electric linear motion actuators operate when the auxiliary energy is electrical power and explosion protection is not required. Electric linear motion actuators are not very robust and more expensive, compared to electrical rotary actuators with linear thrust unit.

Figure 2/18: Electric linear motion actuator Type Haselhofer

Optional accessories are switches depending on the torque, stroke-dependent limit switches, potentiometer, electrical positioning feedback, position electronic, break and thermo-elements.



Electric linear motion actuators are switched off in closing direction. Electric linear motion actuators depend on the torque and make safe closing possible. The opening direction corresponds to the valve’s stroke and is limited by a stroke-dependent limit switch. Electric linear motion actuators only achieve low positioning forces (up to 25 kN). Electrical engineering is a preferred application field for electric linear motion actuators. Electrical rotary actuators Electrical rotary actuators are required to cope with high operating forces and when dynamic forces occur. Great distances to an energy source are easily to bridge. High control- or operating accuracy, a remote control and a surveillance function are easily to achieve. A disadvantage is that an explosion protection can only be guaranteed under extraordinary charges. The positioning speeds are low and a safety position is normally non-existent. The actuators don’t operate appropriate at high or low temperatures and are sensitive to humidity and corrosion. Motion conversion mechanism like the l inear thrust uni t are designed in connection wi th electrical rotary actuators and to operate control valves or rather open/close valves. The rotation of the electrical rotary actuator is transferred from a linear thrust unit into an axial stroke movement. Power plants are a preferred application field for control valves with linear thrust units and electrical rotary actuators.

Figure 2/19: Linear thrust unit, suitable for electrical rotary actuators Design: Flowserve Villach



2.6 Electro-hydraulic actuators Electric-hydraulic linear- or rotary actuators cope with very high positioning force, long strokes and relatively high positioning speeds. In case of an auxiliary energy failure (pressure accumulator) the electro-hydraulic actuator design makes a safety position possible. A disadvantage is that the distance to an energy source is limited, the extensive operating/controlling and the substantial maintenance. An explosion protection can only be achieved under extraordinary expense. The actuators aren’t fully functional in every installation position and therefore shouldn’t be exposed to extremely high or low temperatures. Depending on a certain operation, the proper hydraulic fluid must be chosen. In case of an oil pressure failure (failure of a pressure stressed or a pressure generating part or electrical energy failure), designs with a closed end position accumulator is capable of transforming the actuator over a hydraulic valve into a closed end position. The electro-hydraulic actuators are equipped with manual operating possibilities (hand wheel). The piston (stagnant engine only!) can only be operated with a hand pump.

Figure 2/20: Elektro-hydraulic actuator in compact design Type Reineke

flowserve 2 control valve actuators 2.2 selection of control valve

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