1. Uvođenje

At their essence, kuglični ventil i kuglasti ventil se razlikuju po načinu na koji kontroliraju protok:

• Globe ventili: Use a linear-moving plug (diska) that adjusts the gap between itself and a fixed seat, creating a tortuous flow path that enables precise flow tuning.
  They are the gold standard for applications where flow rate accuracy (±2%) je kritičan.
• Kuglasti ventili: Use a rotational spherical ball (with a port) that aligns with the pipeline (otvoren) or blocks it (zatvoreno).
  Njihova četvrtina okreta (90°) operation enables fast actuation, and their straight-through flow path minimizes pressure drop—ideal for high-flow, low-cycle service.

Both valve types can perform shut-off duties, but they differ fundamentally in internal geometry, hydraulic behaviour, sealing approach, actuation needs and long-term operability.

This article compares them from multiple engineering perspectives and gives practical guidance for selection.

2. Šta je globus ventil?

A Globe ventil je a linear-motion valve primarily designed for flow regulation and throttling, rather than just isolation.

Its name originates from the traditional spherical body shape, though modern designs are available in Z-body, Y-body, and angle-body configurations to balance flow efficiency and pressure drop.

Unlike quarter-turn valves (E.g., kuglični ventili), the globe valve’s axially moving plug and seat arrangement allows it to precisely control flow over the entire stroke (0–100%).

This makes globe valves the preferred choice for process control applications where accurate modulation, stabilnost, and repeatability are required.

Globally, globe valves are governed by industry standards such as:

• API 623 (requirements for globe valves in fossil fuel power plants)
• ASME B16.34 (pressure–temperature ratings and design criteria)
• IEC 60534 (control valve sizing and flow characteristics)

Princip rada

Globe valves operate via three key steps:

• Otvaranje: Pogon (handwheel/electric/pneumatic) lifts the plug vertically, increasing the flow area between the plug and seat.
  The tortuous flow path (Z/Y-angle body) creates controlled turbulence, stabilizing flow at partial openings.
• Zatvaranje: Lowering the plug reduces the flow area, increasing pressure drop and slowing flow. Soft-seated plugs compress against the seat to achieve tight shutoff.
• Gas: The plug’s position (E.g., 30% otvoren) maintains a consistent flow rate.
  Parabolic or V-notched plug designs ensure linear or equal-percentage flow characteristics (per IEC 60534-2-1), critical for process control.

Ključne komponente

3. Šta je kuglični ventil?

A kuglasti ventil je a četvrtokretni rotacioni ventil that uses a spherical closure element ("lopta") with a central bore to start or stop fluid flow.

Kada se bušotina poravna sa cevovodom, ventil je potpuno otvoren; kada se okrene za 90°, the bore is perpendicular to the pipeline, blokiranje protoka.

Ball valves are defined under international standards such as:

• API 608 / API 6D (ball valve design and testing requirements for pipeline and process service)
• ASME B16.34 (pressure–temperature ratings, design criteria)
• ISO 17292 (metal- and soft-seated ball valves for industrial use)

They are prized for low operating torque, mogućnost brzog isključivanja, čvrsto zaptivanje (bubble-tight leakage per ANSI/FCI Class VI), and compact construction, making them widely used in oil & plin, hemikalija, voda, and HVAC industries.

Princip rada

Ball valves operate via three key steps:

• Otvaranje: The actuator rotates the ball 90° clockwise/counterclockwise, aligning the ball’s port with the pipeline. Flow passes straight through the port with minimal resistance.
• Zatvaranje: Rotating the ball 90° blocks the pipeline— the ball’s spherical surface presses against the seat(s) to stop flow.
  Floating ball designs use line pressure to enhance sealing; trunnion designs use springs for bi-directional shutoff.
• Gas (Ograničen): V-port ball valves (with a notched port) can modulate flow, but their flow characteristics are less stable than globe valves (±5% accuracy vs. ±2%).

Ključne komponente

4. Dizajn & Internal Geometry of Globe Valve vs Ball Valve

Dizajn globus ventila

• Put protoka: Globe ventili koriste a tortuous S- or Z-shaped flow path, forcing fluid to change direction as it passes over the plug and seat.
• Element za zatvaranje: A priključak (diska) moves linearly perpendicular to the seat ring, controlled by the stem.
  This geometry makes globe valves ideal for throttling and flow regulation because the plug position correlates with flow area.
• Sjedalo & Plug Interface: The axial force of the stem presses the plug into the seat, producing reliable shutoff.
  Parabolic and V-notched plugs provide predictable linear or equal-percentage flow characteristics.
• Pad pritiska: The tortuous path increases head loss — pressure drop can be 3–5× higher than through a ball valve of the same bore size.
• Body Patterns:

• • Z-body: standard, highest pressure drop, robust for throttling.
  • Y-body: angled flow path reduces ΔP by ~30%.
  • Angle-body: 90° okret, useful for corner installations or slurry service.

Ball Valve Design

• Put protoka: Ball valves use a straight-through bore. In full-port designs, the bore equals the pipe diameter, rezultirajući nearly zero pressure drop (Cv close to straight pipe).
• Element za zatvaranje: A rotating spherical ball with a drilled bore, operated by a quarter-turn stem.
• Seat Design: The ball seals against resilient or metal seats with high contact pressure. This provides balonsko isključivanje but limits throttling due to erosion risk.
• Pad pritiska: Reduced-port balls create some restriction (ΔP increase ~5–10%), but still far lower than globe valves.
• Body Constructions:

• • Plutajuća lopta: jednostavno, used up to ~6″ size, seat sealing from upstream pressure.
  • Lopta montirana na palicu: supported ball, suited for large diameters and high pressure (API 6D).
  • V-port ball: specialized for throttling, engineered to act like a control valve.

5. metrika performansi

Performanse of globe valve vs ball valve can be quantified using standardized engineering metrics such as flow coefficient (CV), pad pritiska (Δp), throttling accuracy, and actuation dynamics.

These parameters directly influence energy efficiency, stabilnost procesa, i životni troškovi.

Comparative Performance Data (12-inč, Carbon čelik, Klasa 300)

Key Performance Insights

Energetska efikasnost

Ball valves excel in pipeline service. Na primjer, a 12-inch oil pipeline (100,000 bbl/day) using a ball valve saves an estimated $180,000 annually in pumping energy compared with a globe valve, due to a 67% Pad nižeg pritiska (5 psi vs. 15 PSI).

Throttling Stability

Globe valves are superior for precizna kontrola protoka, održavanje ±2% accuracy across 10–90% opening.
Nasuprot tome, V-port ball valves offer moderate control (±5%) but lose stability at low openings (<30%), making them less suitable for pharmaceutical dosing or chemical metering.

Brzina aktiviranja

Ball valves actuate 4–30× faster than globe valves. U emergency shutdown (ESD) sustavi, this speed advantage reduces response times by do 90%, which can be the difference between a safe shutdown and a catastrophic failure.

Pritisak & Temperaturna sposobnost

Both designs handle visoka temperatura (do 815 ° C) service with metal seats.

Međutim, kuglični ventili postavljeni na klin achieve higher ocene pritiska (Klasa 4500) compared to globe valves (Klasa 3000).

Izdržljivost & Životni ciklus

Globe ventili, with hardened trim options, može postići 100,000+ ciklusi, making them ideal for frequent throttling.

Kuglasti ventili, especially soft-seated, have shorter cycle lives (30,000–50,000 cycles) unless upgraded to dizajni sa metalnim sjedištima.

6. Sealing performance & klase curenja

• Leakage classes (industrija): soft-seated ball valves can achieve ANSI / FCI 70-2 Klasa VI (nepropusno za mehuriće).
  Globe valves with resilient seats may also achieve Class VI; metal-to-metal seats typically meet Class III–IV depending on finish.
• Bidirectional sealing: kuglični ventili (floating or trunnion types) generally provide reliable bidirectional sealing;
  globe valves can be designed for bidirectional sealing but many globe valves are optimized for one direction (upstream pressure assisting sealing).
• Effect of wear & čvrste tvari: ball valve soft seats may be damaged by abrasive particles;
  globe valves with robust trims can tolerate particulate-laden fluids better when used with appropriate cages and upstream filtration.

7. Operating speed, aktiviranje, and actuator compatibility

• Operating speed: ball valve — quarter-turn (obično <2 s with pneumatic actuator);
  globe valve — multiple turns; actuation time depends on size (minutes for large manual gear operators).
• Actuator compatibility:

• • Kuglasti ventili: highly compatible with quarter-turn actuators (pneumatic rack-and-pinion, scotch yoke, electric quarter-turn). ISO 5211 mounting is common.
  • Globe ventili: require multi-turn actuators (electric multi-turn, pneumatic linear, hydraulic linear).
    Actuators must provide sufficient thrust (axial force) to move the plug against differential pressure.

• Control integration: globe valves are commonly fitted with positioners and digital position feedback for precise control.
  Ball valves with control trims can also be instrumented but need different valve-positioning characteristics.

8. Pressure–temperature capability & material considerations

• Pressure ratings: both valve types are available across common pressure classes (ANSI 150 / 300 / 600 / 900 / 1500). Selection depends on body design and materials.
  Globe valves are commonly used in high-temperature steam service; ball valves with soft seats are temperature-limited by seat material. Metal-seated ball valves extend temperature capability.
• Temperaturne granice: meka sedišta (PTFE, Pik, elastomeri) limit max service temp (PTFE ~260 °C typical, elastomers lower). Metal seats allow hundreds of °C depending on alloy.
  Globe valve materials (for high temp steam) often include forged carbon or alloy steels; ball valves for high temp service use metal seats and special stem/seat designs.
• Materijali: Carbon čelik, Nerđajući čelici, dupleks, Legura čeli, nickel alloys — both valve types are available in a wide range.
  Korozija, erosion and fugitive emissions requirements drive material choice and sealing systems.

9. Izdržljivost, održavanje & common failure modes

• Kuglasti ventili: common failure modes include seat wear/tear (especially when throttled or when solids present), stem packing wear, and torque increase due to deposits.
  Održavanje: 2-piece/3-piece designs allow seat/ball replacement without removing the valve from line (3-piece particularly convenient).
  Ball valves generally require less routine maintenance in clean service.
• Globe ventili: seat and plug wear from cavitation and throttling; packing leaks due to high stem cycles; bonnet/seat repairs typically require bonnet removal and pipeline downtime.
  Globe valves are often easier to re-lap or replace seat and plug assemblies and are designed for finer control maintenance.
• Životni ciklus: ball valves excel in frequent on/off cycles (millions of cycles with proper actuation), while globe valves are designed for frequent modulation but slower cycling.

10. Economic considerations

• Initial cost: depends on size, klasa pritiska, material and trim complexity. For many standard sizes, a ball valve (especially reduced-port) may be less expensive than a control-grade globe valve.
  Control globe valves with special trims and actuators are typically more expensive than simple on/off globe valves or ball valves.
• Lifecycle cost: ball valves often have lower operation and maintenance cost for on/off service.
  For control applications, globe valves can reduce process variability and thereby save energy and improve product quality—offsetting higher initial cost.
  Consider total cost (purchase + aktiviranje + održavanje + energy loss due to pressure drop).
• Energy penalty: the higher pressure drop of globe valves increases pumping energy for a process; for many systems that run continuously, that can be a measurable operational cost.

11. Typical Industry Applications of Globe Valve vs Ball Valve

The choice between a Globe ventil i a kuglasti ventil is highly application-dependent.

While both designs regulate flow and provide shutoff, their inherent strengths dictate which industries favor one over the other.

Aplikacije za globus ventila

Globe valves excel where precision flow control, regulacija pritiska, or frequent throttling je kritičan:

• Generacija energije

• • Steam control valves in fossil fuel and nuclear plants, where throttling across wide load ranges is required.
  • Feedwater systems, handling high-pressure, high-temperature water (do 815 ° C).

• Petrohemijski & Rafiniranje

• • Process control loops requiring accurate modulation, such as hydrogen feed control.
  • Catalytic cracking units, where corrosion-resistant alloys like 316H or Inconel are used.

• Pročišćavanje vode & Desalinizacija

• • Chlorination and dosing systems requiring ±2% flow accuracy.
  • Brine recirculation lines with high differential pressures.

• Farmaceutski & Specialty Chemicals

• • Batch reactors needing precision dosing and throttling stability at low openings (<30%).
  • Clean-in-place (CIP) sustavi with high-purity requirements.

Primjena kugličnih ventila

Ball valves dominate in uključivanje/isključivanje usluge, brzo aktiviranje, and energy-efficient flow Aplikacije:

• Ulja & Gasovoda

• • Prenosni cjevovodi (12–48 inča, ANSI 600–2500), where full-bore ball valves minimize ΔP and pumping cost.
  • Emergency shutdown (ESD) ventili, where actuation time < 5 s is critical.

• Hemikalija & Petrohemijski

• • Storage tank isolation requiring bubble-tight shutoff (za API 598).
  • Slurry and abrasive service, with metal-seated or ceramic-coated designs.

• Power Plants

• • Fuel gas isolation in combined-cycle plants, where rapid actuation is essential.
  • Cooling water lines, where large bore and low pressure drop are advantageous.

• Marinac & Offshore

• • Ballast water systems for fast filling/draining.
  • Subsea manifolds, using trunnion-mounted ball valves with ROV actuation.

• Opšta industrija

• • Sistemi komprimovanog vazduha for quick isolation.
  • HVAC chillers i daljinsko grijanje, requiring low-resistance shutoff.

12. Comparative Summary Table of Globe Valve vs Ball Valve

13. Uobičajene zablude

“Ball valves cannot throttle.”

False: V-port ball valves can modulate flow with ±5% accuracy—sufficient for non-critical applications (E.g., slurry transfer).

Međutim, they cannot match globe valves’ ±2% accuracy for processes like API dosing.

“Globe valves have excessive pressure drop.”

Zavisno od konteksta: Globe valves’ ΔP is intentional—it stabilizes flow for throttling.

For full-flow applications (E.g., naftovode), this is a drawback, but for control applications (E.g., Dovozna voda kotla), it is necessary.

“Ball valves are always cheaper than globe valves.”

False: Upfront cost yes for small sizes (≤6 inches), but trunnion ball valves (≥8 inches) trošak 30% more than globe valves.

TCO depends on use case—ball valves are cheaper for high-flow, low-cycle service.

“Soft-seated valves are better for shutoff.”

Partially True: Mekana sjedala (PTFE) achieve Class VI shutoff, but they degrade above 260°C.

Za primjene na visokim temperaturama (E.g., pare), metal-seated ball/globe valves are more reliable—service life 2x longer.

14. Zaključak

Globe valve vs ball valve both have well-defined roles. Odaberite a Globe ventil when precise flow control, stability and valve authority are required—particularly in control loops and high-temperature services.

Odaberite a kuglasti ventil for fast, reliable isolation with minimal pressure drop and low lifecycle maintenance in clean or filtered services.

For borderline cases, razmotriti control-grade ball valves (V-zarez / multi-stage) ili globe valves with anti-cavitation trims.

Always match valve design, material and actuation to the process fluid, operating conditions and maintenance strategy—decision drivers that determine cost, safety and operating efficiency.

 

FAQs

Can I use a ball valve for throttling?

Standard ball valves are not designed for fine throttling—partial opening concentrates flow and causes seat/ball erosion and vibration.

If throttling is required, use control-grade ball valves (V-zarez) ili (preferably) a globe/control valve.

Which valve has lower maintenance needs?

For on/off service in clean fluids, ball valves generally require less routine maintenance and have longer trouble-free life.

For modulating service, globe valves are designed for repairable trim and predictable maintenance.

Are ball valves suitable for high-temperature steam?

Soft-seated ball valves are limited by seat material temperature.

For high-temperature steam (>200-300 ° C), metal-seated ball valves or globe valves with appropriate high-temperature trims are used.

How does valve choice affect energy consumption?

Globe valves usually cause higher pressure drop when open, increasing pumping/compression energy over long-running processes. Kuglasti ventili (pun provrta) minimize energy loss.

Which valve type provides better emergency shutdown response?

Kuglasti ventili (četvrtina okreta) actuated pneumatically or electrically provide much faster action (sekundi) suitable for ESD systems;

Globe valves are slower to stroke and less suitable for emergency rapid shut-off without specialized fast actuators.