Chlorine valves are critical in any chlorine system, providing essential control and safety measures. Selecting the right valve is crucial for system efficiency, safety, and longevity. This guide will help you navigate chlorine valve selection, ensuring you make an informed decision for your specific needs.
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Quick Takeaways
When it comes to chlorine valves, material selection is not just about durability—it’s a matter of safety and efficiency. The choice of materials directly impacts the valve’s ability to withstand chlorine’s corrosive nature and maintain system integrity.
The type of chlorine in your system – dry or wet – dictates the materials suitable for your valves:
Note that materials suitable for dry chlorine may corrode when exposed to wet chlorine, even at lower temperatures. Always ensure your valve is rated for the specific type of chlorine in your system.
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One must choose the right type of valve for optimal performance in a chlorine system. Here are the main types to consider:
Cylinder chlorine valves are specialized components designed for safe and efficient chlorine gas handling. Industry-leading valves incorporate several features to ensure reliable operation in various conditions.
Standard cylinder chlorine valves are designed for typical chlorine gas cylinders, featuring a 3/4″ NGT inlet thread and a CGA 660/820 outlet connection. These valves are equipped with a fusible plug pressure relief device that activates at 165°F, providing an additional safety feature. They typically have a flow coefficient (Cv) of about 0.733, suitable for the flow rates associated with standard cylinders. The valves incorporate a one-piece Monel stem and an Aluminum Silicon Bronze body for durability in corrosive chlorine environments, with options for PTFE or specialized packing materials to ensure a leak-resistant seal.
Ton container chlorine valves, designed for larger chlorine containers, share many similarities with their standard counterparts but have some key differences. These valves feature a higher flow capacity, with a Cv value of approximately 1.88, to accommodate the larger volume of chlorine in ton containers. Unlike standard cylinder valves, ton container valves do not include a pressure relief device. They maintain the same robust construction with Monel stems and Aluminum Silicon Bronze bodies and offer similar packing options. Both valve types are available with oversized thread combinations to extend the service life of their respective containers, and they share common specifications for working pressure, temperature range, and minimum cycle life.
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Ball valves are valued for their efficiency in high-flow applications but need careful consideration for chlorine use due to potential gas entrapment. Some advantages are:
Butterfly valves are popular in larger chlorine systems where space is limited, offering a good balance of flow control and compact design. Points of note include:
Several key factors must be considered when selecting a valve. The system’s required flow rate will influence the valve size and type. Balancing these factors will help you choose a valve that meets your operational needs while maintaining safety and efficiency.
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Beyond material and type, several other factors play a role in choosing the right chlorine valve:
The manufacturing process significantly impacts valve reliability and performance. Look for:
Proper installation and regular maintenance improve the longevity and performance of your chlorine valves. Ensuring correct installation by following manufacturer guidelines is the first step in maximizing efficiency.
Implementing a maintenance schedule is important for optimal valve performance. This should include routine inspections, cleanings, and part replacements as needed.
While it may be tempting to opt for cheaper valves, consider the long-term value. Higher-quality valves may cost more upfront but offer better performance and longevity. If you require multiple valves, consider exploring bulk purchase discounts, but never compromise on specifications to secure a lower price.
Remember, the cost of valve failure extends far beyond the price of the valve itself. System downtime, product loss, and potential safety hazards can quickly dwarf any initial savings. When selecting chlorine valves, prioritizing quality over upfront costs is not just a financial decision but a safety consideration.
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Selecting the suitable chlorine valve impacts your system’s safety, efficiency, and longevity. By considering factors such as material composition, valve design, type, operating conditions, and manufacturing quality, you can make an informed choice that best suits your needs. Remember, the cheapest option is rarely the best. In your selection process, prioritize safety, reliability, and long-term performance.
Chlorine is used in processes from the production of PVC (polyvinyl chloride) to water treatment. In our modern culture chlorine plays a huge role in refrigeration; it enables us to cool our homes, our vehicles, and our food.
As a disinfectant, it makes drinking water and swimming pools safe by killing dangerous bacteria. It works as a sanitizer in eliminating bacteria from non-porous surfaces.
Chlorine is used to make paper, textiles, medicines, insecticides, and solvents. PVC is used everywhere from water pipes and insulation for electrical wires to blood bags.
When combined with water, it forms hydrochloric acid (HCl), a widely used and commercially important strong acid.
Under normal conditions, chlorine is a gas. Liquid chlorine has been pressurized and the temperature lowered.
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Wet chlorine, that’s either gaseous or liquid chlorine having more than 150 parts per million of water by weight, is highly corrosive and will aggressively attack iron, steel, some stainless steel, Monel®, nickel, copper, brass, bronze, and lead. Dry chlorine can be handled by these metals at temperatures below 250°F without corrosion. And while titanium will react with dry chlorine causing corrosion or even combustion, it is a good option for wet chlorine.
Chlorine service comes with its share of risks. Some of the potential dangers and considerations are discussed here.
In its liquid form, chlorine has a high coefficient of thermal expansion, meaning that the volume increases as temperature goes up. Care must be taken to ensure that any chlorine that gets caught between valves can be released into an expansion chamber. Otherwise, the pipes or fittings could burst or rupture due to the pressure generated by expansion of the chlorine.
Chlorine is not flammable and does not, under normal conditions, support combustion. Because it is an oxidizer, however, care must be taken to avoid the potential of fire.
Oxygen cleaning of valves prior to installation and use is critical in chlorine applications. There can be no oil or grease residue or any other contaminant that could result in a fire in the valves or anywhere in the piping system. Processing in CPV’s class 10,000 clean room meets or exceeds the recommendations for manufacturers providing valves and fittings for chlorine use.
A co-product of chlorine that’s manufactured by electrolysis of sodium chloride solutions is hydrogen (H2). The hydrogen and chlorine gas mixture poses a risk of fire or explosion. Static electricity and impact, as well as ultraviolet light (from sunlight or elsewhere), can set off this reaction. These gases should not be allowed to mix.
Another potential by-product of chlorine manufacturing is nitrogen trichloride (NCl3), also known as trichloramine. This compound, which results from the reaction of chlorine and ammonium salts, irritates mucous membranes when inhaled. It’s also highly explosive.
Liquid chlorine will burn the skin. When the liquid mixes with certain other chemicals, especially ammonia or acids, it releases toxic gases.
Gaseous chlorine is a strong irritant of mucous membranes. It’s also toxic at a level as low as parts per million.
Chlorine itself is non-corrosive. In its liquid form, however, it is hygroscopic, attracting water from its surroundings. With the addition of water, both the liquid and the gaseous chlorine states form hydrochloric (HCl) and hypochlorous (HClO) acids, making it highly corrosive. It can also form ferric chlorides (Cl3Fe), which is damaging to Teflon™ surfaces.
A moisture-free environment preventing water from entering the system will reduce or eliminate this risk. All equipment should be kept dry and care taken to ensure no water remains after cleaning.
Some valve types are better than others when it comes to chlorine processes and operations.
Several factors make globe valves one of the best choices for chlorine use.
Any leakage will allow moisture from the air to enter the system causing corrosion so flexible graphite or PTFE should be used for packing.
In accordance with The Chlorine Institute’s Pamphlet 6, Piping Systems for Dry Chlorine, Edition 16, globe valves for chlorine service should have a bolted bonnet with at least four bolts, a blow-out proof stem, either Stellite hard-facing metal seating or PTFE soft-seating, and an outside screw and yoke gland for external packing gland adjustment.
Providing tight shutoff, the ball valve has a reliable stem seal design. They can be full-bore or reduced-bore. A full-bore (or full-port) valve has an opening the same diameter as the piping, so there’s no restriction in flow through the valve.
Because chlorine that gets trapped in the valve could expand, ball valves need to have a release for any resulting pressure. Either a relief hole bored into the ball or pressure self-relieving seats can be used.
Single-seated segmental ball valves, on the other hand, do not trap liquid when they are closed. They’re commonly used as control valves.
Fully-lined ball valves are lined with a fluoropolymer resin, so there is no metal to chlorine contact. They can be used with wet or dry chlorine gas without concern for corrosion.
Both soft-seated high-performance butterfly valves and fully-lined butterfly valves are options. The soft-seated valves are useful in large pipes.
In fully-lined butterfly valves, like fully-lined ball valves, the fluoropolymer lining prevents the chlorine from touching any metal. They can be used with wet or dry chlorine.
To prevent leakage through the stem seal in the presence of large or frequent temperature fluctuations, consider using bellows seals or live-loaded packing.
Consider both ambient and processing temperatures when selecting valve materials. Keep in mind that throttling applications can create pressure differentials, resulting in lower temperatures.
Wet chlorine is highly corrosive to a number of metals, whereas dry chlorine is not. If the chlorine being processed is dry but could become wet, select materials that are suitable for both.
The potential for flashing and cavitation should be considered and its avoidance considered when sizing the valve.
Where ferric chloride or sodium sulfate may be present, these compounds can build up in parts of valves where there’s low velocity. They also may adhere to some parts. Periodical stroking of the valve should free the build-up. Material that has been stuck for too long can harden, causing the valve to be unable to properly seal and to potentially leak.
All valves for use with chlorine service must be prepared for service according to The Chlorine Institute’s Pamphlet 6, Section 4.5 and labeled to show that it has met the requirements.
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