Piping Valves

Quick Reference

Main valve types for oil & gas: Gate (on/off, minimal pressure drop), Globe (flow regulation), Ball (shut-off, tight seal), Check (prevent backflow), Butterfly (low-cost, large sizes), Plug (quarter-turn on/off). Body: cast (>2”) or forged (<2”). Key specs: ASME B16.34 (ratings), ASME B16.10 (dimensions).

What Are Valves?

Introduction to Oil and Gas Valves

Definition: Valves are mechanical devices used in piping systems to control, regulate, and open/close the flow of fluids. They are manufactured with forged bodies for bore sizes below 2 inches and cast bodies for larger sizes.

Valves are the gatekeepers of every oil and gas piping system. These mechanical devices open, close, or partially obstruct pathways to manage the movement of oil, gas, water, and other process fluids. They govern extraction, processing, transportation, and storage operations, and when they fail, the consequences range from production loss to catastrophic release.

Petrochemical ValvesThis article covers the major valve types, their applications across the oil and gas supply chain, body construction methods, actuation options, and ordering considerations. Each valve type links to a dedicated article with full engineering detail.

Classification of valve types for oil and gas applications

Functions of Valves in Oil and Gas

Valves perform four core functions in oil and gas piping:

Function	What It Does
Flow control	Regulates the rate of oil and gas movement through pipelines: start, stop, modulate, or redirect flow
Pressure maintenance	Keeps pipeline and vessel pressures within safe operating limits, preventing overpressure events and protecting system integrity
Emergency isolation	Shuts off flow in emergency conditions to prevent leaks, spills, and cascading failures
Operational flexibility	Allows maintenance on individual sections without shutting down the entire system, minimizing downtime

Applications of Isolating Valve Types

Valve Type	General Applications	Actuation	Remarks
Globe valve	Shut-off/regulation of liquid/gas flow. Steam and condensate applications.	Usually manual, but may be: Electric, Manual, Hydraulic, Pneumatic	Usually applied to higher pressure or high volume systems, due to cost. Less suitable for viscous or contaminated fluids.
Piston valve	Used fully open or fully closed for on/off regulation on steam, gas and other fluid services. Typically used on fluids that cause excessive seat wear.	Usually manual, but may be: Electric, Manual, Hydraulic	Usually used where the valve body is to be permanently installed and maintenance needs to be minimised.
Gate valve	Normally used fully open or fully closed for on/off regulation on water, oil, gas, steam and other fluid services.	Usually manual, but may be: Electric, Manual, Hydraulic	Not recommended as a throttling valve. Solid wedge gate is free from chatter and jamming. Parallel slide valve used in steam systems.
Butterfly valve	Shut-off and regulation in larger pipelines in waterworks, process industries, HPI, power generation.	Handwheel, Electric motor, Pneumatic actuator, Hydraulic actuator, Air motor	Relatively simple construction. Can be produced in very large sizes. Eccentric design essential for steam systems. Typically used on liquid systems.
Ball valve	Wide range of applications in all sizes, including HPI. Steam and condensate applications.	Handwheel, Electric motor, Pneumatic actuator, Hydraulic actuator	Can handle all fluid types. Limited maximum pressure rating.

Pro Tip

When selecting valves for a new project, don’t just copy the valve type from the P&ID without verifying suitability. I’ve seen globe valves specified for dirty slurry service (wrong - they clog) and gate valves for throttling (wrong - they wire-draw and fail). Match the valve function to the actual service conditions, not just the instrument tag.

Types of Valves in Oil and Gas

The oil and gas industry uses a broad set of valve designs, each matched to specific functions, pressure ranges, and fluid types. The most common are:

• Gate Valves: On/off isolation with minimal restriction when fully open. The workhorse of process piping.
• Globe Valves: Purpose-built for throttling and flow regulation, with precise control over flow rate.
• Ball Valves: Quarter-turn operation provides quick shut-off and tight seal. Used for both on/off and moderate throttling.
• Butterfly Valves: A rotating disc opens or closes the flow path. Compact, cost-effective, and well-suited for large-diameter pipes with low-pressure drop requirements.
• Check Valves: Permit flow in one direction only, preventing backflow that could damage pumps, compressors, and other equipment.
• Safety Valves: Automatically release pressure when it exceeds the set point, protecting equipment and personnel.

ASME valves types by valve functionEach valve type has a dedicated article on this site with full engineering specifications. Follow the links above for deeper coverage of any specific category.

Applications of Valves in Oil and Gas

Valves appear throughout the oil and gas supply chain, from wellhead to terminal:

Supply Chain Segment	Valve Applications
Upstream Operations	In drilling rigs, production wells, and offshore platforms, valves control the flow of oil and gas from reservoirs to the surface and manage injection processes for enhanced recovery.
Midstream Infrastructure	Valves are used in pipelines, pumping stations, and compressor stations to transport oil and gas across long distances, maintaining flow and pressure levels.
Downstream Processing	In refineries and petrochemical plants, valves manage crude oil flow into separation, conversion, and treatment processes that produce fuels and chemicals.
Storage and Distribution	In tank farms and terminals, valves control the storage and loading of oil, gas, and finished products for distribution.

Valve Construction and Market

A valve is manufactured by assembling multiple mechanical parts, the key ones being the body (the outer shell), the trim (the combination of the replaceable wetted parts), the stem, the bonnet, and an actioning mechanism (manual lever, gear, or actuator).

Valves with small bore sizes (generally 2 inches) or that require high resistance to pressure and temperature are manufactured with forged steel bodies; commercial valves above 2 inches in diameter feature cast body materials.

The valve market was worth approximately 40 billion USD per year in 2018. Major manufacturers of oil and gas valves are located in the US, Europe (Italy, Germany, France, and Spain), Japan, South Korea, and China.

Valves are fundamental to safe, efficient oil and gas operations. Their variety and adaptability span the full spectrum of extraction, processing, transportation, and storage requirements.

Valve Types

Valves used in the oil and gas industry and for piping applications can be classified in multiple ways:

By Disc Type (Linear, Rotary, Quarter Turn)

Categorizing valves by how their disc moves to regulate flow reveals which designs fit specific service conditions. The three main motion categories are linear, rotary, and quarter-turn.

Linear Motion Valves

Linear motion valves move a closure element in a straight line to control fluid flow. This category includes:

• Gate Valves: A flat gate moves perpendicular to the flow, providing a straight-through pathway when open and a full seal when closed.
• Globe Valves: A plug moves up and down against the flow, delivering precise flow regulation and complete shut-off capability.
• Diaphragm Valves: A flexible diaphragm moves up and down to permit or restrict flow.

Advantages:

• Precise control of flow and pressure.
• Well-suited to both on/off and throttling applications where flow rate accuracy matters.

Typical Uses: Tight shut-off and flow regulation services, such as water treatment plants and steam or gas control systems.

Rotary Motion Valves

Rotary motion valves rotate a disc or element about an axis to control fluid flow. This group includes:

• Ball Valves: A ball with a through-bore rotates 90 degrees to open or close the flow path.
• Butterfly Valves: A disc mounted on a rod rotates to allow or block flow.

Advantages:

• Compact and lightweight design.
• Quick operation with low torque requirements.
• Generally lower cost than linear motion valves at the same size and rating.

Typical Uses: Applications requiring rapid operation and compact installation, such as chemical processing and water distribution.

Quarter-Turn Valves

Quarter-turn valves are a subset of rotary motion valves that go from fully open to fully closed with a 90-degree turn of the handle or actuator. Ball valves and butterfly valves both fall into this category.

Advantages:

• Speed and ease of operation.
• Effective shut-off capability for both isolation and control.
• Versatility across different media, pressures, and temperatures.

Typical Uses: Widely deployed across oil and gas pipeline flow control, manufacturing processes, and HVAC systems for water flow and temperature management.

Summary: Linear vs. Rotary vs. Quarter-Turn

The choice between linear, rotary, and quarter-turn valves depends on specific application requirements: need for precise flow control, space constraints, and operational speed. Linear motion valves deliver precision and tight shut-off. Rotary motion valves offer compact, quick-acting solutions. Quarter-turn valves combine the speed and simplicity of rotary action with broad versatility.

Oil & Gas Valve Types	Linear motion valves	Rotary motion valves	Quarter turn valves
Gate valve	X
Globe valve	X
Check valve		X
Lift check valve	X
Tilting-disc check valve		X
Stop check valve	X	X
Ball valve		X	X
Pinch valve	X
Butterfly valve		X	X
Plug valve		X	X
Diaphragm valve	X
Safety Valve / Pressure Relief Valve	X

Valves by Body Material (Cast, Forged)

The distinction between cast and forged valves comes down to how they are manufactured, which directly affects their mechanical properties, performance limits, and service suitability.

As a general rule, cast bodies are used for valves above 2 inches in bore size, whereas forged bodies are used for valves below 2 inches (or preferred to cast valves, regardless of the pipeline bore size, in mission-critical applications).

Both types serve defined roles in controlling liquid and gas flow across oil and gas, power generation, and water treatment. Knowing which to specify for a given service is a basic but critical piping engineering decision.

Cast Valves

Manufacturing Process

Cast valves are made by pouring molten metal into pre-shaped molds where it solidifies into the desired valve shape. Casting methods include sand casting, investment casting, and die casting, each producing different surface finishes, dimensional tolerances, and geometric complexity.

Characteristics

• Design Flexibility: Casting allows complex shapes and sizes, producing valves with intricate internal geometries that would be difficult or impossible to forge.
• Material Options: Steel, iron, and non-ferrous alloys can all be cast, giving engineers flexibility in material selection based on service conditions.
• Cost Advantage for Large/Complex Shapes: For complex geometries and larger sizes, casting is more economical than forging, especially at low to medium production volumes.

Limitations

• Defect Potential: Casting can introduce internal porosity, shrinkage cavities, and inclusions that compromise mechanical integrity.
• Quality Variability: Material properties can vary between production batches due to inherent process variations.

Forged Valves

Manufacturing Process: Forged valves are produced by heating a metal billet and deforming it into shape under high pressure. Forging techniques include open-die, closed-die, and ring rolling, selected based on the target geometry and required properties.

Characteristics

• Superior Strength: Forging produces valves with better strength, ductility, and fatigue resistance than casting. The process aligns the metal’s grain structure with the valve shape, enhancing mechanical performance.
• Consistent Quality: Forged valves show more uniform material properties with fewer internal defects than cast equivalents.
• High-Performance Service: Their strength and reliability make forged valves the standard choice for high-pressure, high-temperature, and safety-critical applications.

Limitations

• Geometric Constraints: Forging cannot match the geometric complexity that casting achieves, particularly for large or intricate valve designs.
• Cost Trade-offs: For complex shapes or low volumes, forging costs more than casting, especially at larger sizes.

The choice between cast and forged depends on mechanical strength requirements, pressure-temperature conditions, material needs, design complexity, and cost. Forged valves dominate in high-stress, high-performance services. Cast valves offer greater design flexibility and cost efficiency for complex shapes and large sizes.

To learn more about the difference between steel casting and forging please refer to the linked article.

Common Mistake

Accepting cast valves in sizes where forged bodies should be specified. For high-pressure, high-temperature, or sour service applications, always insist on forged bodies with full radiography - even above 2 inches if the service is critical. Cast valves can have hidden porosity that only shows up when they fail under pressure.

Valves by Type of Actuation (Manual, Actuated)

Valves can also be categorized by how they are operated: manually or through actuators. The choice between these depends on access, frequency of operation, precision needs, and whether remote or automated control is required.

Manually Operated Valves

Characteristics

Manually operated valves require physical effort from an operator via handwheels, levers, or gears. The manual input directly opens, closes, or throttles the valve. Their simpler design (no external power source or automation hardware) reduces installation complexity and upfront cost. With fewer components that can fail, they are highly reliable where valve adjustments are infrequent.

Limitations

For systems requiring frequent adjustments or where valves are hard to reach, manual operation becomes labor-intensive. Manual valves also cannot be operated remotely, which limits their use in large, distributed systems or hazardous environments.

Actuated Valves

Characteristics

Actuated valves use electrical, pneumatic, or hydraulic power to open, close, or modulate valve position. Actuators accept remote control signals, enabling full automation and integration with DCS/PLC systems. This delivers precise control over flow and pressure. Remote operation also allows valve placement in hard-to-access, hazardous, or harsh environments. Actuated valves can respond automatically to sensor inputs, adjusting flow conditions in real time.

Limitations

Higher complexity, cost, and maintenance requirements compared to manual valves. Dependence on an external power source (electrical, pneumatic, or hydraulic) limits deployment where such resources are unavailable.

The choice depends on automation needs, access conditions, safety requirements, and budget. Manual valves work well for simpler, cost-sensitive applications with infrequent adjustments. Actuated valves are the standard for complex systems demanding precise, remote, or automated control.

Valve by Design

Regarding their design, valves can be categorized as follows (our site features detailed articles on each type, so the descriptions here are brief overviews):

Gate Valve

Gate valves are the most used type in piping and pipeline applications. Gate valves are linear motion devices used to open and close the flow of the fluid (shutoff valve). Gate valves cannot be used for throttling applications, i.e. to regulate the flow of the fluid (globe or ball valves should be used in this case). A gate valve is, therefore, either fully opened or closed (by manual wheels, gears, or electric, pneumatic and hydraulic actuators)

Globe Valve

Globe valves are used to throttle (regulate) the fluid flow. Globe valves can also shut off the flow, but for this function, gate valves are preferred. A globe valve creates a pressure drop in the pipeline, as the fluid has to pass through a non-linear passageway.

Check Valve

Check valves are used to avoid backflow in the piping system or the pipeline that could damage downstream apparatus such as pumps, compressors, etc. When the fluid has enough pressure, it opens the valve; when it comes back (reverse flow) at a design pressure, it closes the valve, preventing unwanted flows.

Ball Valve

A Ball valve is a quarter-turn valve used for shut-off application. The valve opens and closes the flow of the fluid via a built-in ball, that rotates inside the valve body. Ball valves are industry standard for on-off applications and are lighter and more compact than gate valves, which serve similar purposes. The two main designs are floating and trunnion (side or top entry)

Butterfly Valve

Butterfly valves are versatile, cost-effective, valves to modulate or open/close the flow of the fluid. Butterfly valves are available in concentric or eccentric designs (double/triple), have a compact shape, and are becoming more and more competitive vs. ball valves, due to their simpler construction and cost.

Pinch Valve

This is a type of linear motion valve that can be used for throttling and shut-off applications in piping applications that handle solid materials, slurries, and dense fluids. A pinch valve features a pinch tube to regulate the flow.

Plug Valve

Plug valves are classified as quarter-turn valves for shut-off applications. The first plug valves were introduced by the Romans to control water pipelines.

Safety Valve

A safety valve protects a piping arrangement from dangerous overpressures that may threaten human life or other assets. It releases pressure once a set value is exceeded.

Choke Valve

Choke valves are critical in upstream oil and gas operations to control well flow rates and manage pressure. They handle the high-pressure drops and erosive service conditions typical of wellhead applications.

Control Valve

Control valves are automated devices that regulate flow in complex process systems and plants. More details about this type are given below.

Y-Strainers

While not properly a valve, Y-strainers have the important function of filtering debris and protecting downstream equipment that may be otherwise damaged.

Valve Sizes (ASME B16.10)

To make sure that valves of different manufacturers are interchangeable, the face-to-face dimensions (i.e. the distance in mm or inches between the inlet and the outlet of the valve) of the key types of valves have been standardized by the ASME B16.10 specification.

ASME B16.34: Valve Compliance

The ASME B16.34 standard, issued by the American Society of Mechanical Engineers (ASME), specifies the requirements for the design, material selection, manufacturing, inspection, testing, and marking of flanged, threaded, and welding end steel valves for pressure systems.

ASME B16.34 is also referenced in the more general ASME B31.1, “Power Piping Design”.

This standard governs the safety, reliability, and performance of valves across oil and gas, chemical, power generation, and water treatment applications. Engineers, manufacturers, and end-users involved in valve specification and procurement need a working knowledge of its requirements.

Key Aspects of ASME B16.34

Aspect	Coverage
Valve Design and Construction	Sets criteria for dimensions, pressure-temperature ratings, and other factors that determine safe operation. Covers gate, globe, check, ball, and butterfly valves.
Pressure-Temperature Ratings	Defines the maximum allowable working pressure at a given temperature for each material group. These ratings dictate safe operating limits for valve selection.
Material Specifications	Details the requirements for body, bonnet, trim, and gasket materials. Specifications address fluid compatibility and service environment to protect valve integrity and service life.
Testing and Inspection	Outlines requirements for shell strength tests, seat tightness tests, and backseat effectiveness tests to verify integrity and performance before commissioning.
Marking and Documentation	Specifies required markings: manufacturer identification, pressure-temperature rating, material designation, and other data for identification, traceability, and procurement.

Importance of ASME B16.34 in Valve Selection

Adherence to ASME B16.34 confirms that valves will perform safely under their specified conditions. Engineers and procurement specialists use this standard to match valves to process medium compatibility, operating pressures and temperatures, and durability requirements.

ASME B16.34 compliance is also a regulatory requirement in many jurisdictions and industries, and a mandatory factor in valve procurement for safety-critical applications.

Valve Compliance to ASME B16.34

A valve complies with ASME B16.34 when the following conditions are met:

• The valve body & shell materials comply with ASME and ASTM material standards for chemistry and strength
• Body & shell materials are heat-treated to achieve proper grain structure, corrosion resistance, and hardness.
• Wall thicknesses of the body and other pressure-containing components meet ASME B16.34 specified minimum values for each pressure class.
• NPT and SW end connections comply with ASME B1.20.1 or ASME B16.11.
• Stems are internally loaded and blowout-proof.
• All bolting will be ASTM grade with maximum applied stress controlled by B16.34.
• Each valve is shell tested at 1,5x rated pressure for a specific test time duration.
• Each valve is tested for seat leakage in both directions for a specific test time duration.
• Each valve is permanently tagged with materials of construction, operating limits, and the name of the manufacturer.

ASME B16.34 provides the framework for valve design, selection, and application in pressure systems. It establishes the baseline for safe, reliable operation across industrial processes.

Control Valves

Key Concepts

Control valves are essential devices in process plants spanning oil and gas, industrial, and nuclear applications. They are deployed in irrigation systems, water treatment plants, power generation facilities, fire prevention systems, pharmaceutical operations, and food processing lines, anywhere that process variables must respond dynamically to changing conditions.

The use of flow control valves has been increasing in recent years as process automation expands across most industries.

A control valve regulates the flow of fluids (gases, liquids, or slurries) by varying the size of the flow passage in response to a signal from a controller.

Control Valves for Oil & GasThis adjustment governs process quantities such as pressure, temperature, and fluid level. Control valves are the final control elements in process loops, and their performance directly determines whether the loop holds setpoint.

The valve achieves this by repositioning a closure element (a disc, plug, or ball) in response to signals from the control system. The control system acts on inputs from process sensors, continuously adjusting valve position to match demand. In a refinery or petrochemical plant, dozens to hundreds of control loops run simultaneously, and each one depends on its control valve responding accurately and repeatably.

Types of Control Valves

Control valves are available in multiple designs, each suited to particular functions and operating conditions. The most common types are globe, ball, butterfly, and diaphragm valves.

Globe valves provide the most precise flow control and dominate applications requiring accurate modulation. Ball and butterfly valves offer faster operation and are typically specified where rapid shut-off matters more than fine throttling. Diaphragm valves handle corrosive fluids well and minimize internal crevices that could trap contaminants, which matters in sanitary and chemical service.

Selection of Control Valves

Selecting the right control valve requires evaluating the fluid properties, the expected flow rate range, the pressure differential across the valve, and the process temperature. The valve material must be compatible with the process fluid to prevent corrosion or degradation.

Accurate sizing is equally critical. An oversized valve hunts and delivers poor control. An undersized valve cannot pass the required flow. Either error leads to valve wear, noise, cavitation, and system inefficiency.

Actuators for Control Valves

Actuators provide the motive force to position the valve based on the control signal. Pneumatic actuators dominate process industry applications due to their reliability and simplicity. Hydraulic actuators deliver high force in compact packages for high-pressure service. Electric actuators provide precise positioning and work well where instrument air or hydraulic power is unavailable.

The opening/closing cycle works through the combined action of an electronic controller, a positioner, and the actuator. The actuator repositions the valve in response to changes in key process parameters (pressure, level, temperature, and flow), keeping these parameters within the target range so the overall process produces the intended output in the required quantity and quality.

Control valves are the primary means of automated flow regulation in industrial processes. Advances in materials, design, and digital control technology continue to improve their performance and diagnostic capability.

Control Valves Types

Control valves are broadly divided into reciprocating (linear motion) and rotary stem designs, each with distinct operating characteristics.

Types of control valves

Reciprocating (Linear Motion) Valves

Reciprocating valves use a stem that moves in a straight line to control flow:

• Globe Valves: A plug moves up and down within the valve body to regulate flow. Well-regarded for precise throttling and modulation, globe valves are the default choice where accurate flow regulation is required.
• Gate Valves: A flat gate slides perpendicular to the flow path. Primarily an on/off device rather than a throttling valve, but provides minimal pressure drop in the fully open position.
• Diaphragm Valves: A flexible diaphragm moves up and down to open or close the flow path. Particularly useful with corrosive fluids, slurries, or where contamination prevention is critical.
• Pinch Valves: A pinching mechanism compresses a flexible tube or sleeve within the valve body. Simple and effective for slurries or fluids with suspended solids.

Rotary Stem Valves

Rotary valves rotate a closure element within the body to control flow:

• Ball Valves: A spherical ball with a through-bore rotates 90 degrees to open or close the flow path. Durable sealing and suitability for both on/off and throttling service across a wide range of fluids and gases.
• Butterfly Valves: A disc rotates around a central axis to regulate flow. Compact and quick-acting, butterfly valves handle large-volume flow and fit tight spaces.
• Plug Valves: A cylindrical or tapered plug with passages through it rotates to align with inlet and outlet ports. Used for on/off control, throttling, and flow diversion.

Specialized Control Valves

Beyond the standard types, specialized designs handle specific service conditions:

• Angle Valves: Similar to globe valves but with a 90-degree body turn. Specified where space prevents a straight valve installation or where the flow direction must change.
• Three-Way Valves: Mix flow from two inlets or divert flow to two outlets, used in blending and diverting applications.

Each control valve type has distinct advantages. Selection depends on the fluid properties, flow rate requirements, allowable pressure drop, and specific process needs.

Flow Control Valve Components

A control valve assembly consists of four primary components: the valve body, the actuator, the positioner, and (typically) a controller. Each one plays a specific role in converting a control signal into precise flow regulation.

Valve Body

The valve body is the pressure-containing casing that holds the internal trim (plug, seat, stem) responsible for flow modulation. It forms the main fluid pathway. Body design determines flow direction, pressure drop characteristics, and suitability for specific services. Body materials are selected based on fluid compatibility, pressure-temperature conditions, and corrosion resistance.

Actuator

The actuator moves the valve’s modulating element (plug, ball, or disk) to adjust the flow passage based on the control signal. Pneumatic actuators use air pressure, hydraulic actuators use fluid pressure, and electric actuators use electrical energy. The choice depends on available power sources, required control precision, and environmental constraints.

Positioner

The positioner receives the control signal from the process control system and converts it into an output signal that drives the actuator to the correct position. It compensates for friction, pressure fluctuations, and unbalanced forces that would otherwise cause positioning errors, improving both responsiveness and accuracy.

Controller

The controller determines the required valve position based on measured process variables. It processes signals from sensors monitoring flow rate, pressure, or temperature and sends a control signal to the positioner. Controllers can be standalone instruments or part of a larger DCS or PLC system.

The coordinated operation of valve body, actuator, positioner, and controller allows precise flow modulation matched to process requirements. This integration delivers the performance, efficiency, and safety that industrial processes demand.

Types of Control Valve Actuators

Control valve actuators fall into four categories based on their power source: pneumatic, hydraulic, electric, and electro-hydraulic. Each has distinct performance characteristics and application strengths.

Pneumatic Actuators

Pneumatic actuators use compressed air to generate the force that moves the valve stem. They are the most widely used actuator type in process industries because of their simplicity, reliability, and cost-effectiveness.

Advantages:

• Rapid response time.
• Simple and reliable operation.
• Inherently safe in explosive environments as they do not generate sparks.

Applications: Widely used in oil and gas, petrochemical, and water treatment facilities, especially where safety and speed of operation are critical.

Hydraulic Actuators

Hydraulic actuators use pressurized oil to move the valve. They produce greater force than pneumatic actuators for the same physical size, which makes them the choice for large valves or high-force applications.

Advantages:

• High force output relative to size.
• Strong performance in high-pressure applications.
• Precise valve positioning.

Applications: Heavy-duty service in power generation, marine, and offshore installations where large valve sizes and high pressures are standard.

Electric Actuators

Electric actuators use motors to drive the valve to the target position. They integrate readily with digital control systems and deliver precise positioning.

Advantages:

• Precise positioning and straightforward control integration.
• No compressed air or hydraulic fluid required, simplifying installation and maintenance.
• Work in environments where pneumatic or hydraulic power is unavailable.

Applications: Water treatment, HVAC, and manufacturing processes where precise control and position feedback are required.

Electro-Hydraulic Actuators

Electro-hydraulic actuators combine an electric motor driving a hydraulic pump, which in turn moves the actuator. This gives the high force of hydraulic systems with the precision and controllability of electric systems.

Advantages:

• High force with precise control.
• Well-suited for remote operation.
• Versatile, combining electric and hydraulic benefits.

Applications: Large valve operations in oil and gas and power generation where both high force and precise control are needed.

Actuator selection depends on required force, response speed, control precision, environmental factors, and available power sources. Matching the right actuator type to the application directly impacts control loop performance and reliability.

Flow Control Valve Accessories

Normally, the selection of accessories such as positioners, transducers, boosters, solenoid valves, limit switches, handwheels and travel stops, snubbers, regulators, and transmission lines, is based on engineering specifications.

Cost Considerations

Cost is a major factor in material selection. Not just the cost of material in dollars per pound, but also the cost of fabrication and inspection contribute to the uninstalled cost of the valve. Installed cost includes the cost of installation and the cost of any damage from improper installation and the costs of the inspection.

The latter consists of such things as analysis of material chemistry, radiographic and surface examination of castings and welds, and check to see that the installed valve is the correct one and that it is properly oriented.

Sizing and Leakage Classes

The selection of the appropriate or optimal control valve type depends on the particular study of the pipe system and the conditions of its fluid, but the size of the control valve should be such that pressure drops through it and not the drop of the pressure of the pipe is the one that controls the flow.

All valves, including steam control valves, must meet an allowable internal leakage standard (FCI / ANSI). The higher the number of leaks, the lower the permissible internal leakage rate.

A Class I valve will have the highest internal leakage rate and usually the lowest cost; While a Class VI valve will have the lowest allowable internal leakage rate. Steam valves must be specified to have a leak rate of not less than Class IV. A class IV steam control valve will maintain a long service life.

Control Valve Selection

Selecting the right control valve is a critical engineering decision that affects process efficiency, safety, and equipment longevity. The selection process involves evaluating fluid characteristics, the valve’s function in the process, and the operating conditions. The following is a structured approach:

1. Define the Process Requirements

• Fluid Characteristics: Identify the fluid type (liquid, gas, or steam), its corrosiveness, viscosity, solids content, and hazard classification.
• Flow Requirements: Determine maximum, minimum, and normal operating flow rates, plus the required turndown ratio, to confirm the valve can control flow accurately across the full operating range.
• Pressure Drop: Calculate the allowable pressure drop across the valve at full open and at normal operating conditions. The valve must operate efficiently within this envelope.

2. Determine the Valve Type

Based on the process requirements, choose between a linear (globe, diaphragm) or rotary (ball, butterfly, plug) valve design. Key factors:

• Control Precision: Globe valves deliver the most precise modulation and are the default for tight regulation applications.
• On/Off Operation: Ball and butterfly valves provide quick, efficient on/off operation.
• Special Fluids: Diaphragm and pinch valves handle corrosive or slurry fluids where eliminating internal cavities is critical.

3. Select the Valve Size

• Sizing Calculations: Use the manufacturer’s sizing software or ISA/IEC equations based on flow requirements and fluid properties to determine the correct valve Cv. The goal: match flow conditions without excessive pressure drop or noise.
• Oversizing and Under-sizing: Oversized valves oscillate and give poor control. Undersized valves cannot pass the required flow. Both cause accelerated wear and operational problems.

4. Material Selection

• Compatibility: Select materials compatible with the process fluid. Common choices: stainless steel for corrosive fluids, brass or bronze for water, and special alloys (Inconel, Hastelloy, duplex) for high-temperature or aggressive services.
• Temperature and Pressure: Confirm that the selected materials meet the maximum operating temperature and pressure requirements per ASME B16.34.

5. Choose the Actuator Type

• Actuation Method: Select pneumatic, electric, hydraulic, or manual actuators based on available power, control requirements, and environment. Pneumatic actuators are the process industry default; electric actuators work where instrument air is unavailable.
• Actuator Sizing: Verify that the actuator provides sufficient force or torque to operate the valve under all process conditions, including maximum differential pressure across the valve.

6. Ancillary Components and Accessories

• Positioners: Specify positioners for modulating applications to improve control accuracy.
• Limit Switches, Solenoids, and Transmitters: Include the feedback, safety, and system integration accessories required by the control philosophy.

7. Review and Compliance

• Standards and Regulations: Confirm that the selected valve meets industry standards (ASME, ANSI, API) and regulatory requirements.
• Manufacturer’s Data: Review technical datasheets and consult with manufacturers to validate the valve’s suitability for the intended service.

Control valve selection demands a thorough understanding of process conditions, fluid behavior, and operational constraints. Involving experienced instrument and process engineers, along with manufacturer consultation, produces the best outcomes.

Control Valves Installation

Step	Guideline
Discharge piping	Always expand the discharge steam line piping to at least one pipe diameter. It is not uncommon to expand the discharge piping by at least two or three pipe diameters. The expansion of the pipe reduces the valve outlet velocities thus prolonging the valve life. The valve manufacturer will provide the appropriate pipe size after the control valve. Match the pipe size to the heat transfer inlet connection.
Downstream spacing	The distance after the steam control valve should be at least ten pipe diameters before the inlet connection of any heat transfer. In pressure reduction applications at least 20 horizontal pipe diameters must be left before a change of flow direction.
Orientation	The control valve must always be installed in a horizontal vapor line, never vertically.
Low flow selection	It is more important to properly select the valve at low flow operating conditions than at its assumed high flow operating conditions.
Bypass valves	Bypass valves must be used in the control valve installation. The by-pass valve is used to allow the personnel of the industrial facility to operate the process without the control valve if valve failure or maintenance is reactive, preventive, and predictive.
Pressure gauges	Installing pressure gauges before and after the steam control valve allows line diagnostics in real-time. Proper installation is critical. In many cases, the source of a troublesome startup can be traced to a control valve that is not properly installed. It is strongly recommended that personnel with an instrumentation background be used at least to supervise the installation and setup of control valves.

Field Note

During commissioning, always stroke-test every control valve from 0 to 100% and back before introducing process fluid. Check for binding, hysteresis, and positioner calibration issues. About half the control valve problems I’ve seen at startup were discovered during stroke testing - problems that would have caused trips or unsafe conditions if found during operation.

How to Order a Valve

Manufacturers of valves used in the oil and gas industry need to know the following information to supply the right device:

Parameter	Details
Valve type	Gate, globe, ball, check, butterfly, plug, etc.
Bore size	NPS or DN
Pressure rating	Class range from 150# to 4500#
Specification	Example: API 6D, API 600, API 602, etc.
Materials	Body and trim materials (at least)
End connection	Flanged, threaded, butt weld, lug, and others
Fluid	Oil, gas, water, steam, solids
Operating conditions	Working temperature and pressure
Quantity	Number of units required
Delivery time	Required delivery schedule
Origin restrictions	Chinese and Indian origins allowed or not

EXAMPLE HOW TO ORDER OIL & GAS GATE, GLOBE, CHECK VALVES

Each manufacturer has own valves ordering sheets that map the valve configuration parameters that user has to consider:

GS - F - 6″ / 150 - 316 - B

1 2 3 4 5

1. Valve type	2. End type	3. Size / Class	4. Body Material	5. Options
C: Check Valve CL: Lift Check Valve CS: Check pressure Sealed Valve CW: Swing Check Valve G: Gate Valve GG: Forged Gate Valve GL: Light Type Gate Valve (API 603) GS: Gate Pressure Sealed Valve O: Globe Valve OB: Globe Bellowed Sealed Valve OS: Globe Pressure Sealed Valve Y: Y-strainer	F: Flanged End T: Threaded End W: Butt Weld End S: Socket Weld End	Size: NPS 1/2 - 80″ANSI Standard:150: 150 LB Class 300: 300 LB Class600: 600 LB Class 1500: 1500 LB ClassDIN Standard：PN16PN25PN40JIS Standard：10K: JIS 10K 20K: JIS 20K	GG: Forged Gate Valve316: Casting S.S CF8M 304: Casting S.S CF8 F316: Forgings S.S F316 F304: Forgings S.S F304 WCB: Steel WCB LCB: Steel LCB HB: Hastelloy B IN: Inconel	B: By-Pass G: Gear Operator D: Drains

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Frequently Asked Questions

What are the main types of valves used in oil and gas?

The main valve types are: gate valves (on/off isolation), globe valves (flow regulation), ball valves (quick shut-off), check valves (prevent backflow), butterfly valves (large diameter, low cost), and plug valves (quarter-turn on/off). Selection depends on the application, pressure class, fluid type, and whether the valve is used for isolation or throttling.

What is the difference between gate and globe valves?

Gate valves are used for on/off isolation with minimal pressure drop when fully open. Globe valves are designed for flow regulation and throttling, with better control but higher pressure drop. Gate valves have a wedge-shaped disc that moves perpendicular to the flow; globe valves have a plug-type disc that moves parallel to the flow path.

When should I use a ball valve vs a gate valve?

Use ball valves for quick shut-off (90° turn), tight sealing, and frequent operation. Use gate valves for infrequent operation, full-bore flow, and when minimal pressure drop is critical. Ball valves are generally better for smaller sizes (NPS 2 and below); gate valves are more common for larger sizes in process piping.

What does valve class 150, 300, 600 mean?

Valve class (150, 300, 600, 900, 1500, 2500) indicates the pressure-temperature rating per ASME B16.34. Higher class means higher pressure capability. Class 150 handles ~285 psi at ambient temperature, Class 300 ~740 psi, Class 600 ~1480 psi. Actual allowable pressure depends on the valve material and operating temperature ; it decreases at elevated temperatures.

What is the difference between forged and cast valves?

Forged valves are made from solid metal billets and used for small bore (typically NPS 2 and below) and high-pressure applications. Cast valves are made by pouring molten metal into molds and used for larger sizes (NPS 2 and above). Forged valves have superior grain structure and strength; cast valves are more economical for large sizes and complex geometries.