Pilot Valves - ASCO
Pilot valves are critical for operating larger valves or control actuators in fluid control systems. These valves act as control mechanisms, receiving signals from external devices such as sensors, controllers, or ...
Categories from ASCO (2)
Fuel, Gas, and Oil Valves
Fuel, Gas, and Oil Valves are specialized devices designed to control fuel, gas, and oil flow and regulation within various industrial applications. These valves ensure safe and efficient operation by managing the delivery and distribution of these volatile fluids. With robust construction and materials resistant to corrosion and high temperatures, they provide reliable performance in demanding environments. Fuel, Gas, and Oil Valves are crucial components in industries such as oil and gas, automotive, power generation, and heating systems, where precise control and safety are paramount.
Solenoid Valves
Solenoid valves provide fast, reliable on/off control of liquids and gases by utilizing an electric coil to actuate the valve. Compact and efficient, they integrate seamlessly into automated systems for applications such as cooling, lubrication, chemical dosing, and process isolation. Available in a variety of materials and designs to handle different pressures, temperatures, and media.
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The ASCO Series 551, also known as 8551, is a line of 1/4" 3-way and 4-way compact solenoid spool valves that are ideal for controlling air or inert gas in challenging environments. The valves’ unique design combines hard T-seals and flexible O-rings that provide bubble-tight shutoff, dirt resistance, and multi-million cycle reliability. The 551 Series comes in anodized aluminum, brass, and stainless steel bodies with ¼-inch NPT and BSP connections. It is suitable for the harsh conditions found in chemicals, refining, food & beverage applications and life science processing. Designed with a light alloy body material, G 1/4 (ISO 228/1) pipe size, and 6 mm orifice, this model provides a 3/2 normally closed valve function, solenoid - pilot operated actuation, 50 Hz frequency, and 115 VAC voltage.
$332.52$363.00
Available for Purchase
Subject to factory lead times
SCG551A017MS.110/50-60 VALVE / SOLENOID
$548.70$599.00
Available for Purchase
Subject to factory lead times
The ASCO Series 551, also known as 8551, is a line of 1/4" 3-way and 4-way compact solenoid spool valves that are ideal for controlling air or inert gas in challenging environments. The valves’ unique design combines hard T-seals and flexible O-rings that provide bubble-tight shutoff, dirt resistance, and multi-million cycle reliability. The 551 Series comes in anodized aluminum, brass, and stainless steel bodies with ¼-inch NPT and BSP connections. It is suitable for the harsh conditions found in chemicals, refining, food & beverage applications and life science processing. Equipped with a G 1/4 (ISO 228/1) pipe size, 6 mm orifice, and light alloy body material, this valve is configured with a 5/2 spring return valve function, solenoid - pilot operated actuation, and 24 VDC voltage.
$351.75$384.00
Available for Purchase
Subject to factory lead times
SCG551A018.110/DC VALVE / SOLENOID
$574.34$627.00
Available for Purchase
Subject to factory lead times
SCG551A065MS.115/50 VALVE / SOLENOID
$721.82$788.00
Available for Purchase
Subject to factory lead times
The ASCO Series 327, also known as 8327, is a line of 3/2-way direct-acting solenoid valves requiring zero minimum operating pressure. Its balanced poppet construction permits high flows at minimum power levels, making it ideal for power plants, refineries, and chemical processing facilities. The valve’s PTFE rider rings and graphite-filled seals reduce friction and eliminate sticking to provide exceptional service life. The 3/2-way direct-acting solenoid valves are ideal for process valve piloting applications.
$1,337.39$1,460.00
Available for Purchase
Subject to factory lead times
The ASCO Series 344, also known as 8344, 4-way solenoid valves incorporate a piston-operated poppet design for high flow in a variety of applications. Their sturdy, robust construction can be used with air or water media. The 344 Series is suitable for use in analytical and diagnostic instruments, biofuels, heating equipment, life science production, and refining. This valve features a 110 VAC voltage.
$6,323.29$6,903.00
Available for Purchase
Subject to factory lead times
The ASCO Series 344, also known as 8344, 4-way solenoid valves incorporate a piston-operated poppet design for high flow in a variety of applications. Their sturdy, robust construction can be used with air or water media. The 344 Series is suitable for use in analytical and diagnostic instruments, biofuels, heating equipment, life science production, and refining. This valve comes with a 24 VDC voltage.
$6,323.29$6,903.00
Available for Purchase
Subject to factory lead times
The ASCO Series 401, also known as 8401, is a line of pilot-operated air slide valves designed for air and inert gas service in heating equipment applications. The aluminum valves incorporate a unique sliding and sealing member that provides a durable and non-stick sealing method. Optional flow control regulates cylinder speed in either direction and permits adjustable Cv from 0.2 to 0.8. Specifications include a 110 VAC voltage.
$1,174.34$1,282.00
Available for Purchase
Subject to factory lead times
The ASCO Series 551, also known as 8551, is a line of 1/4" 3-way and 4-way compact solenoid spool valves that are ideal for controlling air or inert gas in challenging environments. The valves’ unique design combines hard T-seals and flexible O-rings that provide bubble-tight shutoff, dirt resistance, and multi-million cycle reliability. The 551 Series comes in anodized aluminum, brass, and stainless steel bodies with ¼-inch NPT and BSP connections. It is suitable for the harsh conditions found in chemicals, refining, food & beverage applications and life science processing. Configured with a 24 VDC voltage.
$571.60$624.00
Available for Purchase
Subject to factory lead times
SCXG551A001MS.120/50-60.26496 VALVE / SOLENOID
$402.13$439.00
Available for Purchase
Subject to factory lead times
The ASCO Series 262 & 263, also known as 8262 & 8263, is a line of 2-way general service and specialty service solenoid valves available in brass or stainless steel. These rugged valves handle media such as air/inert gas, water, hot water, steam, light oil, fuel gas, fuel oil, Biodiesel fuel (B100) and cryogenic fluids. The 262 & 263 Series are suitable for commercial and industrial applications such as car wash systems, dishwashing and laundry equipment, pumps, compressors, boilers, burners, food processing and many others. Designed with a 110 VAC voltage.
$262.90$287.00
Available for Purchase
Subject to factory lead times
The ASCO 300 Series is a line of general service solenoid valves designed for high-flow and high-pressure applications. The direct-acting valves have a choice of seating materials to handle aggressive fluids, plus resilient seating for airtight shutoff. The 300 Series is ideal for use in analytical and diagnostic equipment, power plants, biofuels, dust collector systems, heating equipment, and refining. This valve features a 120 VAC voltage.
$1,106.55$1,208.00
Available for Purchase
Subject to factory lead times
The ASCO 300 Series is a line of general service solenoid valves designed for high-flow and high-pressure applications. The direct-acting valves have a choice of seating materials to handle aggressive fluids, plus resilient seating for airtight shutoff. The 300 Series is ideal for use in analytical and diagnostic equipment, power plants, biofuels, dust collector systems, heating equipment, and refining. Designed with a 110 VAC voltage.
$1,392.35$1,520.00
Available for Purchase
Subject to factory lead times
The ASCO 300 Series is a line of general service solenoid valves designed for high-flow and high-pressure applications. The direct-acting valves have a choice of seating materials to handle aggressive fluids, plus resilient seating for airtight shutoff. The 300 Series is ideal for use in analytical and diagnostic equipment, power plants, biofuels, dust collector systems, heating equipment, and refining. Key details include a 120 VAC voltage.
$1,392.35$1,520.00
Available for Purchase
Subject to factory lead times
The ASCO 300 Series is a line of general service solenoid valves designed for high-flow and high-pressure applications. The direct-acting valves have a choice of seating materials to handle aggressive fluids, plus resilient seating for airtight shutoff. The 300 Series is ideal for use in analytical and diagnostic equipment, power plants, biofuels, dust collector systems, heating equipment, and refining. This valve is configured with a 120 VAC voltage.
$1,464.72$1,599.00
Available for Purchase
Subject to factory lead times
The ASCO 300 Series is a line of general service solenoid valves designed for high-flow and high-pressure applications. The direct-acting valves have a choice of seating materials to handle aggressive fluids, plus resilient seating for airtight shutoff. The 300 Series is ideal for use in analytical and diagnostic equipment, power plants, biofuels, dust collector systems, heating equipment, and refining. This model features a 1/2" NPT pipe size, 60 Hz frequency, and 120 VAC voltage.
$1,464.72$1,599.00
Available for Purchase
Subject to factory lead times
The ASCO 300 Series is a line of general service solenoid valves designed for high-flow and high-pressure applications. The direct-acting valves have a choice of seating materials to handle aggressive fluids, plus resilient seating for airtight shutoff. The 300 Series is ideal for use in analytical and diagnostic equipment, power plants, biofuels, dust collector systems, heating equipment, and refining. Configured with a 120 VAC voltage.
$4,024.08$4,393.00
Available for Purchase
Subject to factory lead times
The ASCO Series 316, also known as 8316, is a line of high-flow, 3-way solenoid valves, which can be used to pilot large actuators and provide quick closing of large control valves. The diaphragm poppet design is suitable for controlling air, inert gas and liquids. Its resilient seating achieves tight shutoff. This valve features a 24 VDC voltage.
$643.96$703.00
Available for Purchase
Subject to factory lead times
The ASCO Series 316, also known as 8316, is a line of high-flow, 3-way solenoid valves, which can be used to pilot large actuators and provide quick closing of large control valves. The diaphragm poppet design is suitable for controlling air, inert gas and liquids. Its resilient seating achieves tight shutoff. Key details include a 110 VAC voltage.
$687.93$751.00
Available for Purchase
Subject to factory lead times
The ASCO Series 316, also known as 8316, is a line of high-flow, 3-way solenoid valves, which can be used to pilot large actuators and provide quick closing of large control valves. The diaphragm poppet design is suitable for controlling air, inert gas and liquids. Its resilient seating achieves tight shutoff. This valve is configured with a 24 VDC voltage.
$609.15$665.00
Available for Purchase
Subject to factory lead times
The ASCO Series 316, also known as 8316, is a line of high-flow, 3-way solenoid valves, which can be used to pilot large actuators and provide quick closing of large control valves. The diaphragm poppet design is suitable for controlling air, inert gas and liquids. Its resilient seating achieves tight shutoff. Specifications include a 120 VAC voltage.
$706.25$771.00
Available for Purchase
Subject to factory lead times
The ASCO Series 316, also known as 8316, is a line of high-flow, 3-way solenoid valves, which can be used to pilot large actuators and provide quick closing of large control valves. The diaphragm poppet design is suitable for controlling air, inert gas and liquids. Its resilient seating achieves tight shutoff. Configured with a 110 VAC voltage.
$706.25$771.00
Available for Purchase
Subject to factory lead times
The ASCO Series 316, also known as 8316, is a line of high-flow, 3-way solenoid valves, which can be used to pilot large actuators and provide quick closing of large control valves. The diaphragm poppet design is suitable for controlling air, inert gas and liquids. Its resilient seating achieves tight shutoff. Key details include a 24 VAC voltage.
$706.25$771.00
Available for Purchase
Subject to factory lead times
The ASCO Series 551, also known as 8551, is a line of 1/4" 3-way and 4-way compact solenoid spool valves that are ideal for controlling air or inert gas in challenging environments. The valves’ unique design combines hard T-seals and flexible O-rings that provide bubble-tight shutoff, dirt resistance, and multi-million cycle reliability. The 551 Series comes in anodized aluminum, brass, and stainless steel bodies with ¼-inch NPT and BSP connections. It is suitable for the harsh conditions found in chemicals, refining, food & beverage applications and life science processing. Designed with a light alloy body material, G 1/4 (ISO 228/1) pipe size, and 6 mm orifice, this model provides a 3/2 normally closed valve function, solenoid - pilot operated actuation, 50 Hz frequency, and 115 VAC voltage.
$332.52$363.00
Available for Purchase
Subject to factory lead times
SCG551A017MS.110/50-60 VALVE / SOLENOID
$548.70$599.00
Available for Purchase
Subject to factory lead times
The ASCO Series 551, also known as 8551, is a line of 1/4" 3-way and 4-way compact solenoid spool valves that are ideal for controlling air or inert gas in challenging environments. The valves’ unique design combines hard T-seals and flexible O-rings that provide bubble-tight shutoff, dirt resistance, and multi-million cycle reliability. The 551 Series comes in anodized aluminum, brass, and stainless steel bodies with ¼-inch NPT and BSP connections. It is suitable for the harsh conditions found in chemicals, refining, food & beverage applications and life science processing. Equipped with a G 1/4 (ISO 228/1) pipe size, 6 mm orifice, and light alloy body material, this valve is configured with a 5/2 spring return valve function, solenoid - pilot operated actuation, and 24 VDC voltage.
$351.75$384.00
Available for Purchase
Subject to factory lead times
SCG551A018.110/DC VALVE / SOLENOID
$574.34$627.00
Available for Purchase
Subject to factory lead times
SCG551A065MS.115/50 VALVE / SOLENOID
$721.82$788.00
Available for Purchase
Subject to factory lead times
The ASCO Series 327, also known as 8327, is a line of 3/2-way direct-acting solenoid valves requiring zero minimum operating pressure. Its balanced poppet construction permits high flows at minimum power levels, making it ideal for power plants, refineries, and chemical processing facilities. The valve’s PTFE rider rings and graphite-filled seals reduce friction and eliminate sticking to provide exceptional service life. The 3/2-way direct-acting solenoid valves are ideal for process valve piloting applications.
$1,337.39$1,460.00
Available for Purchase
Subject to factory lead times
The ASCO Series 344, also known as 8344, 4-way solenoid valves incorporate a piston-operated poppet design for high flow in a variety of applications. Their sturdy, robust construction can be used with air or water media. The 344 Series is suitable for use in analytical and diagnostic instruments, biofuels, heating equipment, life science production, and refining. This valve features a 110 VAC voltage.
$6,323.29$6,903.00
Available for Purchase
Subject to factory lead times
The ASCO Series 344, also known as 8344, 4-way solenoid valves incorporate a piston-operated poppet design for high flow in a variety of applications. Their sturdy, robust construction can be used with air or water media. The 344 Series is suitable for use in analytical and diagnostic instruments, biofuels, heating equipment, life science production, and refining. This valve comes with a 24 VDC voltage.
$6,323.29$6,903.00
Available for Purchase
Subject to factory lead times
The ASCO Series 401, also known as 8401, is a line of pilot-operated air slide valves designed for air and inert gas service in heating equipment applications. The aluminum valves incorporate a unique sliding and sealing member that provides a durable and non-stick sealing method. Optional flow control regulates cylinder speed in either direction and permits adjustable Cv from 0.2 to 0.8. Specifications include a 110 VAC voltage.
$1,174.34$1,282.00
Available for Purchase
Subject to factory lead times
The ASCO Series 551, also known as 8551, is a line of 1/4" 3-way and 4-way compact solenoid spool valves that are ideal for controlling air or inert gas in challenging environments. The valves’ unique design combines hard T-seals and flexible O-rings that provide bubble-tight shutoff, dirt resistance, and multi-million cycle reliability. The 551 Series comes in anodized aluminum, brass, and stainless steel bodies with ¼-inch NPT and BSP connections. It is suitable for the harsh conditions found in chemicals, refining, food & beverage applications and life science processing. Configured with a 24 VDC voltage.
$571.60$624.00
Available for Purchase
Subject to factory lead times
SCXG551A001MS.120/50-60.26496 VALVE / SOLENOID
$402.13$439.00
Available for Purchase
Subject to factory lead times
The ASCO Series 262 & 263, also known as 8262 & 8263, is a line of 2-way general service and specialty service solenoid valves available in brass or stainless steel. These rugged valves handle media such as air/inert gas, water, hot water, steam, light oil, fuel gas, fuel oil, Biodiesel fuel (B100) and cryogenic fluids. The 262 & 263 Series are suitable for commercial and industrial applications such as car wash systems, dishwashing and laundry equipment, pumps, compressors, boilers, burners, food processing and many others. Designed with a 110 VAC voltage.
$262.90$287.00
Available for Purchase
Subject to factory lead times
The ASCO 300 Series is a line of general service solenoid valves designed for high-flow and high-pressure applications. The direct-acting valves have a choice of seating materials to handle aggressive fluids, plus resilient seating for airtight shutoff. The 300 Series is ideal for use in analytical and diagnostic equipment, power plants, biofuels, dust collector systems, heating equipment, and refining. This valve features a 120 VAC voltage.
$1,106.55$1,208.00
Available for Purchase
Subject to factory lead times
The ASCO 300 Series is a line of general service solenoid valves designed for high-flow and high-pressure applications. The direct-acting valves have a choice of seating materials to handle aggressive fluids, plus resilient seating for airtight shutoff. The 300 Series is ideal for use in analytical and diagnostic equipment, power plants, biofuels, dust collector systems, heating equipment, and refining. Designed with a 110 VAC voltage.
$1,392.35$1,520.00
Available for Purchase
Subject to factory lead times
The ASCO 300 Series is a line of general service solenoid valves designed for high-flow and high-pressure applications. The direct-acting valves have a choice of seating materials to handle aggressive fluids, plus resilient seating for airtight shutoff. The 300 Series is ideal for use in analytical and diagnostic equipment, power plants, biofuels, dust collector systems, heating equipment, and refining. Key details include a 120 VAC voltage.
$1,392.35$1,520.00
Available for Purchase
Subject to factory lead times
The ASCO 300 Series is a line of general service solenoid valves designed for high-flow and high-pressure applications. The direct-acting valves have a choice of seating materials to handle aggressive fluids, plus resilient seating for airtight shutoff. The 300 Series is ideal for use in analytical and diagnostic equipment, power plants, biofuels, dust collector systems, heating equipment, and refining. This valve is configured with a 120 VAC voltage.
$1,464.72$1,599.00
Available for Purchase
Subject to factory lead times
The ASCO 300 Series is a line of general service solenoid valves designed for high-flow and high-pressure applications. The direct-acting valves have a choice of seating materials to handle aggressive fluids, plus resilient seating for airtight shutoff. The 300 Series is ideal for use in analytical and diagnostic equipment, power plants, biofuels, dust collector systems, heating equipment, and refining. This model features a 1/2" NPT pipe size, 60 Hz frequency, and 120 VAC voltage.
$1,464.72$1,599.00
Available for Purchase
Subject to factory lead times
The ASCO 300 Series is a line of general service solenoid valves designed for high-flow and high-pressure applications. The direct-acting valves have a choice of seating materials to handle aggressive fluids, plus resilient seating for airtight shutoff. The 300 Series is ideal for use in analytical and diagnostic equipment, power plants, biofuels, dust collector systems, heating equipment, and refining. Configured with a 120 VAC voltage.
$4,024.08$4,393.00
Available for Purchase
Subject to factory lead times
The ASCO Series 316, also known as 8316, is a line of high-flow, 3-way solenoid valves, which can be used to pilot large actuators and provide quick closing of large control valves. The diaphragm poppet design is suitable for controlling air, inert gas and liquids. Its resilient seating achieves tight shutoff. This valve features a 24 VDC voltage.
$643.96$703.00
Available for Purchase
Subject to factory lead times
The ASCO Series 316, also known as 8316, is a line of high-flow, 3-way solenoid valves, which can be used to pilot large actuators and provide quick closing of large control valves. The diaphragm poppet design is suitable for controlling air, inert gas and liquids. Its resilient seating achieves tight shutoff. Key details include a 110 VAC voltage.
$687.93$751.00
Available for Purchase
Subject to factory lead times
The ASCO Series 316, also known as 8316, is a line of high-flow, 3-way solenoid valves, which can be used to pilot large actuators and provide quick closing of large control valves. The diaphragm poppet design is suitable for controlling air, inert gas and liquids. Its resilient seating achieves tight shutoff. This valve is configured with a 24 VDC voltage.
$609.15$665.00
Available for Purchase
Subject to factory lead times
The ASCO Series 316, also known as 8316, is a line of high-flow, 3-way solenoid valves, which can be used to pilot large actuators and provide quick closing of large control valves. The diaphragm poppet design is suitable for controlling air, inert gas and liquids. Its resilient seating achieves tight shutoff. Specifications include a 120 VAC voltage.
$706.25$771.00
Available for Purchase
Subject to factory lead times
The ASCO Series 316, also known as 8316, is a line of high-flow, 3-way solenoid valves, which can be used to pilot large actuators and provide quick closing of large control valves. The diaphragm poppet design is suitable for controlling air, inert gas and liquids. Its resilient seating achieves tight shutoff. Configured with a 110 VAC voltage.
$706.25$771.00
Available for Purchase
Subject to factory lead times
The ASCO Series 316, also known as 8316, is a line of high-flow, 3-way solenoid valves, which can be used to pilot large actuators and provide quick closing of large control valves. The diaphragm poppet design is suitable for controlling air, inert gas and liquids. Its resilient seating achieves tight shutoff. Key details include a 24 VAC voltage.
$706.25$771.00
Available for Purchase
Subject to factory lead times
FAQS
- A pilot valve is a small solenoid valve used to control a larger valve or actuator by managing the pilot air or hydraulic signal that operates the main valve. Rather than the solenoid directly opening and closing the main process valve (which would require an impractically large and expensive solenoid), a small pilot valve is energized to route control pressure to the actuator of the main valve, which then opens or closes. This two-stage approach allows a small, low-power electrical signal to control a large process valve handling high pressures and flow rates. Pilot valves are available in 3/2-way and 4/2-way configurations. A 3/2-way pilot valve is used to control single-acting actuators — it alternately supplies pressure to and exhausts one side of the actuator. A 4/2-way pilot valve controls double-acting actuators. Centro carries ASCO Series 327/8327 direct-acting pilot valves, Series 316/8316 high-flow 3-way pilot valves, and Series 344/8344 4-way piston-operated pilot valves.
- A direct-acting solenoid valve uses the electromagnetic force of the solenoid coil to directly lift or push the valve element to open or close the flow path. The solenoid provides all the force needed to operate the valve, regardless of line pressure. Direct-acting valves work at zero pressure differential and are used for smaller orifice sizes and lower flow rates. A pilot-operated solenoid valve uses the solenoid to open a small pilot orifice, which then allows line pressure to act on a larger diaphragm or piston to open the main valve. The line pressure does most of the work. This allows pilot-operated valves to handle much larger orifice sizes and higher flow rates with a compact, low-power solenoid. However, pilot-operated valves require a minimum pressure differential across the valve to function. The ASCO Series 327/8327 available through Centro is a direct-acting 3/2-way valve with balanced poppet construction that provides high flow at minimum power levels, with PTFE rider rings and graphite-filled seals that reduce friction and eliminate sticking — making it ideal for process valve piloting in power plants, refineries, and chemical processing facilities.
- Pilot valves serve several critical functions in industrial process applications. Process valve piloting is the primary use — pilot valves provide the control air signal that operates the pneumatic actuators on large ball valves, butterfly valves, plug valves, globe valves, and other process valves in chemical plants, refineries, power plants, and water treatment facilities. When a control system sends an electrical signal to open or close a process valve, the pilot valve converts that electrical signal into pneumatic energy to move the actuator. Safety shutdown systems use pilot valves to quickly vent actuator air pressure and drive process valves to their fail-safe position during an emergency. Actuator control packages use pilot valves to provide the directional air control needed for double-acting pneumatic actuators. They are also used to pilot larger solenoid valves, diaphragm valves, and piston valves where the main valve requires more flow than a direct solenoid can provide. The ASCO Series 316/8316 is specifically designed as a high-flow 3-way pilot valve for quick closing of large control valves.
- When selecting a pilot valve for industrial applications, several features determine its reliability and suitability. Construction materials must be compatible with the pilot medium and ambient environment — stainless steel bodies and trim for corrosive environments, brass or aluminum for general service. Low friction internal components (PTFE rider rings, graphite-filled seals) prevent sticking and ensure reliable operation even after extended periods in one position — this is a common failure mode where pilot valves seize because they sit energized for weeks or months without cycling. The ASCO Series 327/8327 specifically addresses this with PTFE rider rings and graphite-filled seals. Explosion-proof or intrinsically safe electrical ratings are essential for installation in hazardous classified areas. Low power consumption reduces heat buildup in the coil and extends service life. Manual override capability allows operators to manually actuate the valve during testing or control system failures. The valve should be rated for the actuator's air supply pressure and temperature, and port connections should match the actuator and control tubing.
- Sizing a pilot valve for a pneumatic actuator requires matching the pilot valve's flow capacity (Cv) to the actuator's air volume and required response time. Determine the actuator's air volume — the total volume of compressed air needed to stroke the actuator fully, measured in cubic inches or liters. Determine the required stroking time — how fast the actuator must move the process valve. Calculate the required Cv using the actuator volume, available air supply pressure, and required stroking time. The pilot valve's Cv must equal or exceed this value. Also consider the port size — the pilot valve connections must be compatible with the actuator's pilot air connections and the tubing used in the installation. For double-acting actuators, a 4-way pilot valve (like the ASCO Series 344/8344) is needed; for single-acting (spring-return) actuators, a 3-way pilot valve (like the ASCO Series 327/8327 or 316/8316) is used. Undersizing the pilot valve results in slow actuator response because the valve cannot supply enough air volume quickly; oversizing adds cost but does not harm performance.