Introduction

A solenoid valve is an electrically controlled valve. The valve features a solenoid, which is an electric coil with a movable ferromagnetic core (plunger) in its center. In the rest position, the plunger closes off a small orifice. An electric current through the coil creates a magnetic field. The magnetic field exerts an upward force on the plunger opening the orifice. This is the basic principle that is used to open and close solenoid valves.

characteristic

• It is only used for clean liquids and gases.
• Indirect-operated valves require a pressure differential to function.
• Are used to close, open, dose, distribute, or mix the media with 2 or more inlets/outlets.
• Fast acting.
• Options for manual overrides, ATEX, gas approval, media separation and more.
• Can get hot as it requires energy to switch and stay in that position (depending on type).
• Common in heating systems, compressed air, vacuum, irrigation, car washes, etc.

let's see how it works a solenoid valve

A solenoid valve consists of two main components: a solenoid and a valve body (G). The figure above shows the components. A solenoid has an electromagnetically inductive coil (A) around an iron core at the center called the plunger (E). At rest, it can be normally open (NO) or normally closed (NC). In the de-energized state, a normally open valve is open and a normally closed valve is closed. When current flows through the solenoid, the coil is energized and creates a magnetic field. This creates a magnetic attraction with the plunger, moving it and overcoming the spring (D) force. If the valve is normally closed, the plunger is lifted so that the seal (F) opens the orifice and allows the flow of the media through the valve. If the valve is normally open, the plunger moves downward so that the seal (F) blocks the orifice and stops the flow of the media through the valve. The shading ring (C) prevents vibration and humming in AC coils.

Solenoid valves are used in a wide range of applications, with high or low pressures and small or large flow rates. These solenoid valves use different operating principles that are optimal for the application. The three most important ones are explained in this article: direct acting, indirect acting, and semi-direct acting operation.

The solenoid in the figure above is built by Lucifer Company. Almost all oil & gas companies use it, especially in security systems where reliability must be at 100%.

For more information click here and download the datasheet

Asco Solenoids

Another type of very reliable solenoid is built by Asco company. there are two types, seal from disk (Figure 1) or sliding shaft (Figure 2)like Bifold solenoid

A solenoid valve is an electromechanical valve which is normally used for the fluid control of water, air, oil or gas. They are made up of two components:

• The solenoid (essentially consisting of a coil, core, core tube, shading coil and spring)
• The valve (the body containing orifices in which the disc, diaphragm or piston is positioned).

This type of solenoid is suitable for cut-off direct which could be fuel gas, diesel, water, etc, its soft seal guarantees excellent reliability

Principles of Operation

A solenoid valve is a combination of two basic functional units:

• A solenoid (electromagnet) with its core
• A valve body containing one or more orifices

Flow through an orifice is shut off or allowed by the movement of the core when the solenoid is energised or de-energized. ASCO valves have a solenoid mounted directly on the valve body. The core is enclosed in a sealed tube, providing a compact, leaktight assembly.

 Direct Acting Valves (Figures 1A, 1B)

When the solenoid is energized in a direct-acting valve, the core directly opens the orifice of a normally Closed valve or closes the orifice of a normally Open valve. When de-energized, a spring returns the valve to its original position. The valve will operate at pressures from 0 psi to its rated maximum.

The force needed to open the valve is proportional to the orifice size and fluid pressure. As the orifice size increases, so does the force required. A pilot-operated construction is used to open large orifices while keeping solenoid size small.

Internal Pilot Operated Valves (Figures 2A, 2B)

Normally, these valves have a pilot and bleed orifice which enables them to use line pressure for operation.

When the solenoid is de-energized, the pilot orifice is closed and full line pressure is applied to the top of the piston or diaphragm through the bleed orifice, providing seating force for tight closure.

When the solenoid is energized, the core opens the pilot orifice, relieving pressure from the top of the piston or diaphragm via the outlet side of the valve. The line pressure then opens the valve by lifting the diaphragm or piston off the main orifice.

Two constructions are available for 2-way valves:

• Floating diaphragm or piston which requires a minimum pressure drop across the valve to remain in the open position (Figures 2A, 2B).
  
• Hung-type diaphragm or piston held open mechanically by the solenoid core. The valve opens and remains open with zero pressure drop(Figures 3A, 3B).
  

  Solenoids in Figure 2

Historically, a typical solenoid valve deployed in such an environment and application would consume upwards of 20 Watts per unit. With the new design 327 operating with a much lower power consumption of only 2 Watts per unit, losses are minimised and operational running costs are greatly reduced. As a direct consequence, there is much less heat generated leading to extended operational life and of course – enhanced safety

The new design of the valve features a more efficient solenoid with an optimised magnetic performance. This improved design efficiency has contributed greatly to reduced power consumption of the valves to 1W when cold and 1.5W DC when hot. The Series 327 valves have a 3/2 direct-operated solenoid valve configuration and can be mounted in any orientation. The valve is compact and lightweight and is no longer constrained by the requirement for a minimum operating pressure – quite simply, it has no minimum operating pressure requirements.

The valve is rated to 10 Bar and comes in a flame-proof IP67 Ex d aluminium or 316 stainless-steel enclosure is rated to II 2G/D Ex d IIC T6 Ex tD.

Below Figure/drawing with the internal parts of the solenoid

The ASCO solenoid valves are a quality and reliable solution that provide real benefits to installation engineers and end users throughout the whole lifecycle of the product – they are the most specified valves for critical and safety-related applications.

Advantages of the Asco 327 solenoids

• Corrosion-resistant and NACE-compliant valve for the ambient including the solenoid internals
• Direct acting; functioning on very low electrical power without the need for piloting
• Same solenoids for different ATEX/IECEx protection methods covering most common zones: Ex d – Ex emb – Ex ia
• Compact, low weight with good connectivity
• Latest ATEX/IECEx explosion safety classifications for highest safety
• Low power consumption – minimum of 1.8 watts for Ex d & e mb and 0.5 watts for “ia
• Suitable for safety systems; Exida certified; SIL 3 capable

For more information click here and download the datasheet

We have been working in oil and gas for more than 10 years and never found a problem with this type of solenoid, except once time only, the solenoid was damaged because the line was full of dirty.

There are many models on the market but according to our experience, this is the most reliable.