INTERNALLY PILOTED 2-WAY VALVES

Automotive Lift Repair Tampa Florida Internally piloted solenoid valves feature either a 2- or 3-way pilot solenoid. A diaphragm or piston seals the main valve seat. A pressure differential between the inlet and outlet ports generates a shut-off force due to the larger effective area on the diaphragm’s upper side. Opening the pilot valve relieves pressure from above the diaphragm, allowing the greater pressure from below to lift the diaphragm and open the valve. Generally, internally piloted valves require a minimum pressure differential for effective operation. Omega also offers internally piloted valves designed with a coupled core and diaphragm that function at zero pressure differential (Fig. 5).

 INTERNALLY PILOTED MULTI-WAY SOLENOID VALVES

Internally piloted 4-way solenoid valves are primarily used in hydraulic and pneumatic systems to operate double-acting cylinders. These valves have four port connections: a pressure inlet (P), two cylinder ports (A and B), and an exhaust port (R). This connects port P to A, while B exhausts through a second restrictor to R.

 EXTERNALLY PILOTED VALVES

Automotive Lift Repair Tampa Florida Externally piloted valves use an independent pilot medium for actuation. Fig. 7 illustrates a piston-operated angle-seat valve with a closure spring. In its unpressurized state, the valve seat remains closed. When energized, the solenoid raises the piston against the spring’s force, opening the valve. A normally-open version is available by positioning the spring on the opposite side of the actuator piston, connecting the independent pilot medium to the actuator’s top. Double-acting versions controlled by 4/2-way valves do not include any springs.

 MATERIALS

All materials for valve construction are selected based on their application types. Body, seal, and solenoid materials are chosen to ensure reliability, fluid compatibility, durability, and cost-effectiveness.

BODY MATERIALS  

Automotive Lift Repair Tampa Florida Neutral fluid valve bodies are typically made of brass or bronze. For high-temperature fluids like steam, corrosion-resistant steel is used. Additionally, polyamide is utilized in various plastic valves for economic reasons.

SOLENOID MATERIALS  

All parts of the solenoid actuator in contact with the fluid are crafted from austenitic corrosion-resistant steel, ensuring protection against corrosive media.

SEAL MATERIALS  

The selection of seal materials considers the specific mechanical, thermal, and chemical conditions of each application. FKM is the standard for neutral fluids at temperatures up to 194°F. For higher temperatures, EPDM and PTFE are used, with PTFE being universally resistant to nearly all relevant fluids.

 PRESSURE RATINGS – PRESSURE RANGE

All pressure values presented in this section are gauge pressures measured in PSI. The valves are designed to operate reliably within specified pressure ranges, valid from 15% undervoltage to 10% overvoltage. When using 3/2-way valves in alternate operations, the permissible pressure range may vary; refer to our data sheets for specifics.

For vacuum operations, ensure the vacuum is applied to the outlet side (A or B) while the higher pressure (atmospheric pressure) is connected to the inlet port P.

 FLOW RATE VALUES

The flow rate through a valve depends on its Automotive Lift Repair Tampa Florida design and flow type. The appropriate valve size for an application is typically determined by its Cv rating, which is standardized for water at temperatures between 40°F and 86°F and a pressure drop of 1 PSI. Cv ratings for each valve are provided. A similar standardized system for pneumatics uses air flow in SCFM upstream with a pressure drop of 15 PSI at 68°F.

 SOLENOID ACTUATOR

All Omega solenoid valves feature an epoxy-encapsulated solenoid system, integrating the magnetic circuit—coil, connections, yoke, and core guide tube—into a compact unit. This design maximizes magnetic force while ensuring excellent electrical insulation and protection against vibration and corrosion.

 COILS

Omega coils are available for all standard AC and DC voltages. The low power consumption, especially in smaller solenoid systems, facilitates control via solid-state circuitry.

The magnetic force increases as the air gap between the core and plug nut decreases, regardless of whether AC or DC is used. An AC solenoid system generates more magnetic force at a greater stroke than a comparable DC system. The relationship between stroke and force is depicted in Fig. 8.

AC solenoid current consumption is influenced by inductance; as stroke increases, inductive resistance decreases, leading to higher current consumption. Conversely, DC solenoids rely solely on winding resistance for current consumption. A time-based comparison of AC and DC solenoid energization is shown in Fig. 9, illustrating that solenoid valves draw significantly higher currents when initially energized compared to when the core is fully retracted. Consequently, AC valves can manage higher pressures than DC valves of the same orifice size, while DC systems can achieve higher pressures only by reducing orifice size and flow capability.

 THERMAL EFFECTS

An Automotive Lift Repair Tampa Florida solenoid coil generates some heat. Standard solenoid valves are designed to limit temperature rise to a maximum of 144°F under continuous operation (100%) at 10% overvoltage, with a permissible ambient temperature of 130°F. Maximum fluid temperature limits depend on specific seal and body materials, which can be found in the technical data.

 TIME DEFINITIONS (VDE0580) RESPONSE TIMES

Due to their small volumes and high magnetic forces, solenoid valves achieve rapid response times. Various valves with different response times are available for specialized applications. The response time is defined as the interval between the switching signal application and the completion of mechanical opening or closing.

ON PERIOD  

The on period is the time from when the solenoid current is turned on until it is turned off.

CYCLE PERIOD  

The cycle period encompasses the total duration of both the energized and de-energized periods. Common cycle periods are 2, 5, 10, or 30 minutes.

RELATIVE DUTY CYCLE  

The relative duty cycle (%) is the ratio of the energized period to the total cycle period. Continuous operation (100% duty cycle) is defined as operation until steady-state temperature is achieved.

 VALVE OPERATION

Automotive Lift Repair Tampa Florida Valve operation coding consists of a capital letter. The accompanying summary details the codes for various valve operations along with their standard circuit symbols.

 VISCOSITY

The technical data is valid for the specified viscosities. Higher viscosities are permissible, but may reduce the voltage tolerance range and extend response times.

 TEMPERATURE RANGE

Fluid temperature limits are specified, but various factors (ambient conditions, cycling, speed, voltage tolerance, installation details, etc.) can affect temperature performance. The values provided should be regarded as general guidelines. For operations at temperature extremes, consult Automotive Lift Repair Tampa Florida’s Engineering Department for advice.