The PTFE Solenoid Valve – Features and Applications

A device used to manage valve activation is referred to as a solenoid. These devices are electromechanical in nature and control the flow of gas or liquid. The operation of a PTFE Solenoid Valve includes an electrical current running through the coil which actuates the coil armature and opens the valve internal plunger. The coil is as traditional direct acting electro-mechanic device. Electrical current flowing through the coil windings creates a magnetic field. This magnetic field actuates the coil armature, which in turn actuates the valve plunger. De-energizing the coil allows an internal spring to return the valve to its natural state.

At iPolymer, we provide high quality PTFE Solenoid Valves for our customers.

Direct Acting versus Pilot Operated
When the plunger opens and closes the orifice within the valve directly, the PTFE Solenoid Valve is said to be direct-acting.

When the plunger opens and closes a pilot orifice, the solenoid valve is considered pilot-operated. In this configuration, the primary valve seal is opened and closed by the inlet pressure.

Applications
Various industries utilize direct acting solenoid valves. Their focus tends to be directly acting on the flowing media i.e. the media process. PTFE Solenoid Valves are a special class of solenoid valves, which primarily focus on high purity media (DI water, purified water or high purity chemistry) or highly corrosive media (high and low pH chemistries typically strong acids or chemical blends).

The PTFE Solenoid Valves are commonly controlling and distributing process chemistries throughout OEM Equipment for cleaning, mixing, blending, and etching. PTFE Solenoid Valves are frequently used side-by-side with PTFE Pumps, PTFE Check Valves and PTFE Tubing, Fittings and other devices.

Components
Solenoid valves can be manufactured out of various materials in order to complement different types of fluid management systems. A valve’s body must be manufactured with a material that functions properly with system media in order to avoid contamination or premature valve failure due to corrosion. High Purity Valves used for ultraclean application or chemically harsh application are commonly designed out of PTFE, PVDF, PFA, PVC and Polypropylene.

Other components must be properly selected as well. Those include the valve seat, ports, coil, and seals are the most crucial components to consider when choosing a valve.

Seat
The Valve Seat design includes the plunger or plug characteristic i.e. how the valve actuates to seals and block the flow and/or unseal to allow flow. Diaphragm Valve utilize a diaphragm like design to complete cover the Valve Seat and isolate the actuator region of the valve. Piston type designs utilize a simple plunger or plug. While Bellows are somewhat a mixed design: they utilize an outside diaphragm to seal the actuation region which drives an internal piston into a bellow. The bellows expands (stretches) and seal at the valve seat similar to a traditional plunger or plug.

All of these Valve Seats and its associated piston, plunger, plug will typically have a Valve Seal (O-Ring, Quad Ring or Cup Seal). There is one exception: the PTFE Hard Seat. PTFE is a very resilient polymer which can be highly polished. When properly designed and machined, PTFE on PTFE surfaces can create drip-proof bubble tight seals. The PTFE Hard Seat is a special design class of PTFE Valves. They allow the manufacturer to supply a valve with one less O-Ring. In fact, our iPolymer PTFE Diaphragm Valves both Solenoid and Pneumatic style can be configured with PTFE Hard Seats and no O-Rings within the wetted flow path.

Ports
PTFE Solenoid Valves typically will have two or three ports. Conveniently known as 2-Way and 3-Way valves, these two Port configurations dominate 80% of the Solenoid Valves on the market. 2-Way PTFE Solenoid Valves are simple on/off valves. They can be configured to be Normally Closed (NC) or Normally Open (NO). When energized they will actuate to the opposite configuration NC will open and NO will close. Whereas 3-Way PTFE Solenoid Valves allow the user to get much more creative: one port is considered Common, one port is considered A and the 3rd port is considered B. Depending on how the 3-Way valve is configured will define if A is Normally Open or Normally Closed. What always holds true is that B is the opposite of A, thus when energized the A and B roles flip. This valve effectively toggles the Common flow path between A and B. 3-Way valves are sometimes referred to as A-B Switching Valves and A-B Toggle Valves.

The physical connection of these Ports can vary. The most common are Female NPT (FNPT), Compression Tube, Flare and SAE Straight Thread w/O-Rings.

Coil
The actuation heart of a Solenoid Valve is its Coil. Solenoid Coils are electro-mechanical inductance wire wound coils. They create a magnet field when a voltage is applied across the load (power) and neutral (return) wire with sufficient current. The Coil’s magnetic field draws (pull) an armature inward and typically results in the compression of a return spring. When the power is turned off and the coil de-energizes, the return spring pushes the armature back to its unloaded position. The armature is attached to a valve stem or some other connective member to the plunger at the valve seat.

Seals
Seals are used in various locations within a valve design. Within the valve body, these seals are typically static (resting against all stationary surfaces) or dynamic (resting against at least one moving surface) and are more frequently considered part of the wetted flow path. As part of the wetted flow path, their material make up is critical. Common materials for high purity seals are EPDM, Viton, Aflas, and Kalrez (sequenced by increasing chemical resistance). These seals are most commonly found as traditional O-Rings. But can also be configured as Quad Rings and Cup Seals.