Solenoid valves are electromechanical valves that are used to control the flow of liquids or gases. Consisting of a solenoid coil and a valve, solenoid valves function by converting electrical energy into mechanical energy, which can open or close the valve in order to shut off, dose, release, mix or distribute the fluids or gases.
Offering advantages such as rapid and safe switching, a compact design, high reliability and typically long service life, solenoid valves are used in a wide range of industries; particularly, commercial, industrial, residential and appliance. Solenoid valves are mainly categorized in three ways: material being controlled; such as solenoid air valves and solenoid water valves; design, such as 3 way solenoid valves, proportional solenoid valves or plastic solenoid valves; or how they are being powered, such as pneumatic solenoid valves and 12 volt solenoid valves. Each type of solenoid valve is best suited for certain flow control applications. For example, miniature solenoid valves are commonly used in medical industries for applications such as gas analyzers, biotechnology equipment, and portable medical devices, while stainless steel solenoid valves are ideal for chemical processing applications due to high corrosion and abrasion resistance that allows for excellent control of acids, analytical reagents and bases. Additionally, high pressure solenoid valves allow flow control in areas in which other valves could not operate, such as potentially dangerous machinery or inaccessible lines.
The two main components of a solenoid valve are a solenoid coil and a valve. A solenoid coil is a magnetized wire coil that becomes activated through electrical charges, resulting in current flow. The current flow creates a magnetic field, thus converting the electrical energy to mechanical energy and moving the actuator. The actuator is attached to the valve, and causes valve movement. A spring returns both the actuator and the valve back to their un-activated state when the current flow is no longer present. Solenoid valves typically are configured in two main ways: normally open (NO) or normally closed (NC). In a normally closed (NC) valve, a plunging pin or rod within the valve is held in place by solenoid coil to block flow. In order for gas or fluid to flow through the valve, an electromagnetic charge is run through the solenoid coil, which becomes active and lifts the plunger out of the passage to allow flow. Normally open (NO) valves are the opposite; they remain open until the solenoid is activated and pushes down the plunger, blocking flow and creating pressure to keep the valve closed. In addition, solenoid valves can be direct-acting or pilot-operated. Direct-acting solenoid valves have a plunger that is in direct contact with the in-flow opening in the valve body, or orifice. This plunger is used to open and close the orifice, which permits or hinders flow. The pilot-operated solenoid valve, which is actually a combination of a pneumatic or hydraulic valve and a smaller solenoid valve, works with a diaphragm rather than a plunger, using differential pressure to control the flow of gases or fluids.
The many different types of solenoid valves have varied configurations and actuation methods. Pneumatic solenoid valves are one of the most common types, and are used to regulate the flow of air and other gases through the use of diaphragms and gas pressure. While some pneumatic valves regulate air or gas flow at relatively normal pressures, such as in home heating and cooling applications, other pneumatic valves are designed to output gas at extremely high pressures, such as in power tools. Pneumatic valves can also be referred to as gas solenoid valves, solenoid air valves, or just air valves. Another common type is a proportional solenoid valve, which functions by utilizing the same elements as a regular pneumatic or hydraulic solenoid valve but with more advanced flow control capabilities due to allow variable flow that is proportional to the electrical control signal. Solenoid water valves, or hydraulic solenoid valves, are less common than pneumatic solenoid valves but still vital to many applications. Solenoid water valves are typically NC as well as pilot-operated, as opposed to direct-acting. While most solenoid valves are 2-way, meaning that they have two connection areas and one orifice; however, 3-way solenoid valves are also available, with three connections and two orifices. Another highly common solenoid valve type is a 12 volt solenoid valve. The 12 volt refers to the amount of voltages supplied by the direct current (DC) power source, which could also be 3v, 6v and 24 volt solenoid valves; however, 12 volt solenoid valves are the standard. All of these solenoid valve types can be constructed from a range of materials such as plastic solenoid valves, which can be PTFE, PVC, natural polypropylene, CPVC and PVD, or metal solenoid valves, such as stainless steel, bronze, aluminum and brass.
One type of valve that is particularly comparable to solenoid valves is an actuated ball valve. An actuated ball valve is mostly used to shut flow off or turn flow on, not necessarily for flow control. A ball valve contains a ball with a small hole in the middle that helps to control the flow of materials through the pipe, and an actuator that rotates the ball to start or stop flow. While there are many applications in which solenoid valves should be used instead of ball valves, such as low flow and high speed cycles, there are also applications in which a ball valve should be used instead of a solenoid valve, such as high flow and applications requiring a manual override option. However, there are many beneficial characteristics of solenoid valves that give them advantages over other valve types. For example, since solenoid valves are powered by natural pressure and electromagnetic force, they generally have fewer moving parts than other valves. This is widely considered to be a good design, since moving parts require maintenance. In addition, solenoid valves can be easily operated by remote devices that activate the solenoid coil, making solenoid valves extremely useful for hazardous applications. Also, solenoid valves can use either hydraulic or pneumatic power because both can be activated or piloted by solenoids. However, pneumatic power is more commonly used because it considered cleaner and lower maintenance than hydraulic power, due to the absence of degrading fluids which produce waste and must be maintained.
Solenoid Valve Manufacturers - Humphrey Products
Solenoid Valve Manufacturers - International Polymer Solutions
Solenoid Valve Manufacturers - Jefferson Solenoid Valves USA, Inc.
Solenoid Valve Manufacturers - International Polymer Solutions, Inc.
Solenoid Valve Manufacturers - Burkert Fluid Control Systems
Solenoid Valve Manufacturers - International Polymer Solutions, Inc.
A solenoid valve, an electromechanical valve, incorporates an electric coil to regulate or control the flow of liquid and gas. The solenoid features a ferromagnetic core, also known as plunger, which moves in its center as the electricity passes through the device.
Principle of Working
As electric current passes through the coil, it creates a magnetic field, which in turn, exerts force on the plunger, and it moves under the action of magnetic field towards the centre of the coil, and in the process, opens the orifice. It is the basic principle that opens and closes solenoid valves, irrespective of type, whether it is pneumatic solenoid valves, high-pressure solenoid valves, proportional solenoid valves, 2 way solenoid valves or 4 way solenoid valves, they all work on the same principle.
Since they are highly reliable and work in different conditions, they are among the most frequently used flow control related products. They have an array of applications, from heating systems to compressed air technology, to industrial automation to sprinkler systems, including many others.
Common types of Solenoid valves
Most common type of solenoid valves in which the medium flows, either liquid or gas, through an orifice that is closed by a plunger, which has a rubber gasket on its bottom to choke the flow effectively. They are used for relatively small flow rates and are used from 0 bar up to the maximum pressure that is allowable. It can be a 2 or 4 way solenoid valve.
There are two types:
This type of valve regulates opening and closing by the differential pressure of the medium. They need a minimum differential pressure to operate, which is around 0.5 bar. They have applications only in devices that need one-way flow, such as in showers, irrigation systems, and car wash systems.
There is another type, known as semi-direct operated solenoid valves, that combines the attributes of direct and indirect valves, which allows them to work from zero bar, and can handle a high-flow rate. This construction is normally used in high-pressure solenoid valves.
Solenoid valves are an important component in the reverse osmosis (RO) process. They are installed at critical points, giving the system the ability to work optimally for several years.
However, to select an appropriate valve, there are a number of considerations, other than usual right size and wattage, such as availability, certifications, ease of assembly and support. The factors discussed in this article have significant impact on equipment life, availability, and time-to-market.
The U.S. state drinking water and plumbing codes requires RO equipment to meet NSF 61-G, a leachate and lead-free regulation. A buyer or manufacturer should check if Original Equipment Manufacturers (OEMs) are complying with the regulations. A special caution is advised while specifying composite valves for the RO systems. In North American locations, like Vermont or California, all RO systems must have a NSF certification.
To reduce lead amounts in drinking water, all pipes, plumbing fittings, fixtures and flow control related products, including electric solenoid valves, should be lead free, one should look for valves that passes and possess all the certifications. For international use, the valves should get certification NSF International and accredited by ANSI and the Standards Council of Canada.
Lean manufacturing methodologies demand that OEM provide composite valves readily. Non-availability of parts results in uncertain scheduling and longer lead times, which ultimately threats assembly line and target dates.
When evaluating a valve maker, determine whether supplier has quick-shipment programs and what the standard lead times and delivery schedules are.
It has been observed that composite valves fail only after a few operating cycles, the issue may emanate from poor connection system design; however, it is mainly because of specification pressure or thermal stress. It is important to consider high-pressure solenoid that are designed and rated for higher temperatures and higher pressures.
The other issue is whether the valve connects easily; go for valves that utilize NPT and solvent bond connections. The alternative to these conventional solvent bonded valves are the quick-connect valves, however, they are inherently proven to be leaky.
Most of the time, integration of components into systems proves time-consuming and difficult. This mainly happens when vendors present pressure switches in closed versions, which may result in purchasing diverter valves. Therefore, it is important to find a vendor that provides valves with both open and normally closed versions.
Other than hardware characteristics, you need to have a proper support system from the vendors. Some suppliers put resources and energy to maintain a quality support system and some do not. Some vendors end up providing bad service without intending to because of a geographical disadvantage. That is why, for North American customers, Asian or European products are not deemed appropriate because of these logistical challenges. Find a vendor that can answer your queries related to 2-way solenoid valves, 4-way solenoid valves or 12-volt solenoid valves, give technical fixes, and provide onsite training.
There is not much equipment that is used as extensively as solenoid valves in the world of flow control related products. Its electro mechanical functions and different types, such as 2, 4 way solenoid valves, high pressure solenoid valves and proportional solenoid valves, complement applications from refrigeration and air conditioning, to automobiles, to hydraulics and pneumatics.
In air-conditioning systems, electric solenoid valves are used to control the flow of the refrigerant to heat exchangers. The efficiency of an air conditioning unit or refrigeration unit can be affected greatly, if a defected solenoid is used.
Pneumatic and Hydraulic Systems
Pneumatic systems require specially designed pneumatic solenoid valves or air valves, similarly hydraulic systems have their own valves. They are used to regulate the flow to hydraulic and pneumatic motors, buffers and cylinders.
Solenoid valves used in car wash systems are Normally Closed (NC) and made from stainless steel. They regulate the flow of detergent mixed water and release it at high pressure. For other applications in car washes, low-pressure valves are used; for example, foam brushes use Normally Open (NO) valves.
Compressed Air systems
In compressed air systems, solenoid valves are used to control air supply, actuators, or as an unloader valve. Almost all compressed air systems have a high Kv value, which minimizes the pressure drop. Usually, direct valves are generally used since there is always a pressure difference. And in some cases of low pressures, for example after a reducer, a semi-direct or direct type of valve perform better.
They are readily used in reverse osmosis water purifier system. The other home appliance that use pressure switches is central heating system. The valve works in conjunction with the thermostat, controlling the flow of hot water to the radiators. Moreover, all washing machines and dishwashers make use of solenoid valves that control and provide the correct amount water.
The valves used for irrigation supply a high flow rate. Commonly, they are indirectly operated-also known as servo controlled.
Given the number and types of solenoid valves available on the market, it gets daunting to select a valve that will perform optimally in a challenging environment. Solenoid valves are mainly categorized based on three attributes, first the material they control, for example solenoid air valves and water valves; second is the design, such as proportional solenoid valves and plastic solenoid valves, and 3 way solenoid valves; third based on power, that includes 12 volt solenoid valves and pneumatic solenoid valves.
Here, we are presenting pertinent information that will help to choose an appropriate valve for your need.
It has become a common practice to select electric solenoid valves based on line size. Many times this has been proved to be risky. For many, a 5/8" ODF sweat connection and 5/8" line size seems a perfect match that works in every application. However, there are other factors should be considered. For example, a solenoid valve used in the suction line might have a capacity of 0.52 tons, whereas the same solenoid valve used in the liquid line will need a capacity of 8 tons. An oversized valve may not close properly, and it might cost more. Therefore, valves should not be selected just by line size. Other factors should also be considered, like application.
Different types of valves are designed for different types of fluids. Therefore, one should use valves only with the fluids they were originally designed to work with, since materials used to make may not be compatible with other fluids.
Many people use a general-purpose valve to regulate combustion exhaust, such as propane or natural gas, never do that. This is a recipe of disaster, since vales used for shutting off combustibles need a solenoid valve that has passed some special safety agency requirements for safety shut-off service.
Solenoid valves come with a range of coil housing types. American National Standards Institute (ANSI) and National Electrical Manufacturers Association (NEMA) designates standards for suitability of a valve. The general rule is, the higher the ANSI/NEMA type number, the greater the exposure to the elements that can be permitted.
A NEMA Type 1 is well suited for indoor applications, whereas NEMA Type 4 is suitable for outdoors. Gradually the number goes upwards, and a NEMA Type 7 or Type 9 is required for locations where there are explosive vapors or dust.
Types of valve
There are usually two types of solenoid valves that are used in refrigeration. First is normally closed (NC), it remains closed when de-energized, and other is normally open (NO), which remains open when de-energized. For installation in the liquid line, NC is used, as it remains closed when the system is not running, preventing refrigerant migration. NO types of valves are used when valve only has to be closed for brief intervals.
3 way solenoid valves are for hydraulic and pneumatic applications. 3-Way solenoid valves have three ports, one being the pressure port, one the tank and the last, the service port.
12 volt solenoid valves are the standard amount of voltages supplied by the direct current (DC) power source.
regulate the release of air.
Gas solenoid valves are one of the most common flow control valves that that handle and control the flow of gaseous media.
use fluid pressure and are ported through the return
line to the reservoir.
Miniature solenoid valves fit easily into a
small area and also measure or dispense small amounts of material.
Mini solenoid valves are particularly useful in medical applications.
Plastic solenoid valves are primarily used in applications that involve corrosion
Pneumatic solenoid valves are similar to the hydraulic version in that they both use pressure. However, the return port of a pneumatic valve, which uses air, is exhausted to the atmosphere.
High pressure solenoid valves are solenoid valves that control the flow of fluids or gases in high pressure applications.
have direct-acting control valves with linear characteristics.
Proportional solenoid valves control accuracy, hysteresis and repeatability
within close tolerances.
have three bearing balls that ride on an inclined plane and turn linear motion into rotary motion. The magnetic arrangement permits direct rotational motion.
Solenoid air valves control are electrical valves that regulate the flow of air.
are electrical devices that control water flow.
- Position sensor whose
voltage output differs through various values.
- A circumstance in which there is no leakage of air from between the internal sealed ports of the valve, whether in the energized position or not, in a five second time period. Soap bubbles are used to detect leakage.
- A situation in which the tubing is pinched in the valve.
- The maximum voltage to which the coil must be energized for the valve to achieve its highest specified capacity.
- Energizing a solenoid valve at a constant level of power for its entire on-time.
- The quantity of current in amperes flowing through a solenoid valve coil when it is energized.
- The normal opening and closing of a valve.
- The measure of how many times a valve is able to open and close within a set period of time.
- Proportion of time that the solenoid receives power.
- A feature that allows for the manual reducing or controlling of flow.
- Magnetic steel plate that helps transmit magnetic flux in the magnetic circuit of a solenoid valve from the enclosure to the sleeve construction. A flux plate is necessary on valves with a body construction consisting of a non-metallic body.
- Changes with the output variable in steady-state conditions, caused by a sinusoidal input variable.
- Association of input to output or the sensitivity of a device.
- The variation between up-scale and down-scale outcomes in equipment response, when exposed to the same input from the opposite direction.
- A term that refers to a valve that is closed when unenergized.
- A term that refers to a valve that is open when unenergized.
- A system in which direct feedback is not supplied to gauge the response.
- Employing electronic sensors to watch the position of the valve and provide electronic feedback.
- Increases function of solenoid valves by reducing power consumption and heat generation. The valve is opened and held open at decreased power.
- A technique that utilizes a modulated wave function to control analog devices.
- The ability of the equipment to generate consistent results on successive tests.
- The space the plunger covers during a state change.