Mechanical devices are valves, and they are fundamental components that allow for the control of fluid flow and system pressure. They are mostly utilized to operate the amount of liquid passing through a given system or procedure as well as the flow direction. A broad range of industrial applications are reliably fitted by several types of valves.
The fundamental components of any type of valve are the body, actuator, bonnet, trim, and packing. We have included all the essential information in this diaphragm valve vs ball valve guide. You can find high-quality and sturdy valves from a decent industrial valve supplier.
What Is Diaphragm Valve
Diaphragm valves are all two-way valves, and they can function as throttling and on-off valves. In some low-pressure applications, diaphragm valves provide benefits that are not attainable with other types of valves. They have streamlined fluid passageways that reduce pressure drop. Even when transporting fluids with suspended solids, they display good leak-tight qualities and are ideal for applications requiring mild throttling.
The valve’s working components are separated from the liquid stream, deterring fluid contamination and functioning mechanism corrosion. The valve is essentially leak-tight because of the absence of a leak path around the stem of the valve. This characteristic makes the valve essential in situations where system leakage cannot be allowed.
The substance of the diaphragm and the service temperature affect the maximum pressure that these valves can withstand. The service conditions also affect the valve’s rated design lifespan. Additionally, the system hydrostatic test pressure should not be greater than the diaphragm’s absolute pressure rating.
What Is Ball Valve
A quarter-turn valve appropriate for clean gas, compressed air, and liquid service is the ball valve. They can also be utilized for slurry service, although precautions should be taken to avoid crud accumulation. Exceptional sealing ability is provided by the usage of soft-seat substances like nylon, synthetic rubbers, fluorinated polymers, and Delrin.
Ball valves can be utilized at service temperatures of between 450 and 500 degrees Fahrenheit (270 and 260 degrees Celsius). In addition, the service temperatures of graphite seats can go up to 1000 degrees Fahrenheit (538 degrees Celsius) or more. The valves can be utilized in services that are safe from fire since they have metal backing seats. In terms of operation, ball valves are comparable to plug valves, and they deliver leak-tight sealing and are non-binding.
The smooth body and port of the stainless steel ball valve models result in minimal flow resistance. The four different body types used to create ball valves are: side entry, top entry, three-piece body, and split body. The valve ends can be soldered, brazed, butt welded, socket welded, threaded, flanged, or soldered. Both high-pressure and low-pressure ball valves are produced.
Diaphragm Valve Vs Ball Valve: A Complete Comparison
Here we will compare some of the features and functions of the ball valve vs diaphragm valve to help one understand the specifications and purposes of these valves.
Valve Types
Here are the different subtypes of ball valves and diaphragm valves.
- Ball Valves
Here we have listed the different types of ball valves:
- The split-body ball valve’s two-part body is made up of a cover, a ball, seat rings, a stem, and various internals.
- With top-entry ball valves, the valve bonnet cover can be taken off to gain access to the internals for assembly, disassembly, restoration, or maintenance.
- End-entry ball valves are made of one piece, have a ball that is injected from one end, and are held in place by an insert.
- The stem of the three-piece body ball valve passes through a hole at the top, and the main middle portion houses all of the valve’s internals.
- The stem sealing on lubricated or non-lubricated ball valves is typically carried out by bolted packing glands and O-ring seals.
- Diaphragm Valves
Diaphragm valves can be divided into two categories: weir and straight-through variants. The diaphragm valves can be lined on the inside of the body and the end flanges in order to utilize them for corrosive applications. Based on the application, several lining substances might be employed.
Construction
- Ball Valves
The ball valve’s body, spherical plug, and seats are its main parts. There are three main patterns for ball valves: reduced port, full port, and venturi port. The inner diameter of the full-port valve is identical to the pipe’s interior diameter. The port is typically a single pipe size that is less than the line size in venturi and reduced-port types.
O-ring seals and bolted packing glands are used to seal the stem. A lubricant-seal system for valves that is comparable to plug valves is also accessible. Based on the quantity of valve ports and valve seats, a ball valve can be unidirectional, bidirectional, or multidirectional. Due to that, 2-way, 3-way, 4-way, or 5-way multiport valves are other names for ball valves.
- Diaphragm Valves
An adaptable diaphragm serves as the primary pressure barrier of a diaphragm valve. It is composed of a rigid body with a weir in the flow route, a compressor that pushes the diaphragm against the weir, and a bonnet and hand wheel that hold the diaphragm to the body and operate the compressor.
Diaphragm valves are produced with different end connections, including solvent cement joint ends for thermoplastic valves, male sanitary threaded ends, clamp ends, screwed ends, and flanged, screwed, or threaded ends.
Function
The main difference between a diaphragm and a ball valve function is the way the valve regulates flow.
- Ball Valves
A metal sphere that spins into and out of the flow passage is delivered by ball valves, and the best valves for on-off control are ball valves. A metallic ball is set in a straight-through flow route during a quarter rotation to begin or halt the flow. The pivoting hollow ball with holes regulates the flow through it. The ball valve rotates along an axis vertical to the flow by means of a transmission that pushes the valve handle.
- Diaphragm Valves
With a valve body and a seat onto which the diaphragm closes, an adaptable elastomeric diaphragm is delivered by the diaphragm valve. The diaphragm valve offers precision actuation and quick shutdown. It applies pressure to a flexible sheet that reduces the width of the liquid flow route. In comparison to other types of valves, diaphragm valves have the longest cycle life.
Flow
The amount of gallons for every minute of 60 degrees Fahrenheit water that will pass through the valve at a particular opening with a 1 psi pressure drop across the valve is known as the valve flow coefficient. The size of the valve that will let it pass the necessary flow rate while maintaining stable control of the procedure liquid is chosen using the coefficient.
- Ball Valves
A ball valve can be utilized to throttle or operate the flow or movement of media through a system in addition to halting and beginning. The total ports present can be one to four ports, and the ball’s ports might have a T-shaped or an L-shaped design. The T-shape permits flow in a single direction while the other side is closed or in two directions simultaneously. Only one direction of flow is possible in an L-shape pipe, and the port utilizes a diverter valve.
- Diaphragm Valves
The flow rate for a control valve is influenced by how wide the valve is opened. The linear and equal percentage can be used to calculate the flow rate. The amount the disc moves is precisely related to the linear flow rate. The flow rate is at 50 percent of ultimate flow when the disc is 50 percent open. The proportional flow rate is correlated with the incremental change in valve opening percent.
Materials Used
Valves are designed using a wide variety of materials, as required by their application.
- Ball Valves
Brass, bronze, metal alloys, ductile iron, stainless and other steel types, copper, cast iron, and plastics like PVC and CPVC are among the frequently used materials for ball valves. Most balls are made of metal, and the elastomeric substance or plastic is used for the trim. Different elastomeric substances, such as Teflon® (TFE), Neoprene, Nylon, Buna-N, and material mixtures are used to create resilient seats for ball valves.
- Diaphragm Valves
A variety of materials can be used to create diaphragms. The type of substance handled, as well as temperature, pressure, and frequency of use, all influence the substance choice. Elastomeric diaphragm substances are extremely chemical resistant at high temperatures.
The materials utilized in diaphragm valves are Butyl rubber, White natural rubber, Natural/synthetic rubber, Nitrile rubber, Butyl rubber, Neoprene, Viton, Hypalon, and White butyl. The body of a diaphragm valve can be constructed from a variety of solid metals and alloys, solid plastic, rubber, glass, and plastic materials.
Valve Sizing
- Ball Valves
The mechanism of valve sizing involves calculating the flow via the valve’s diameter. Two different-sized apertures in valves can be present to withstand a pressure decrease. For throttling valves, valve sizing is typically performed for this reason.
- Diaphragm Valves
When choosing a diaphragm valve as a throttle device, sizing is crucial. The intake and exit ports are typically of the exact size as the open or shut down system has no pressure drop. In this instance, the amount of media flowing through the system and the flow coefficient define the valve size.
While choosing the valve sizing, plenty of variables need to be considered.
- The type of media that the valve will be controlling comes first. The media’s viscosity and specific gravity will have an impact on the flow rate.
- The absolute inlet pressure, temperature, and output pressure at absolute load come in second.
- The maximum quantity comes in third place, followed by the greatest pressure drop that the valve must close against. One can alter the pipe geometry factor.
Different Applications
- Ball Valves
Ball valves offer simple operation and a long lifespan. They can endure high pressure, velocity, and temperature fluxes, and their manufacturing costs are minimal. Compared to gate valves and globe valves, less force is needed to activate the valve. Ball valves are a common process control option in common industrial applications due to these qualities. Moreover, it is not easy to clean the ball valves, which is why they are not much utilized in food and beverage and medical field applications.
- Diaphragm Valves
In applications involving corrosive and abrasive liquids, diaphragm valves are frequently used. For example, diaphragm valves are repeatedly used in chemical and electricity facilities, municipal, industrial, and wastewater applications as well. Diaphragm valves are also widely used in the pulp, paper, and other slurry generating and control-related sectors, including cement mining and ethanol production.
Rangeability
Rangeability is a crucial consideration when choosing a valve type. It is described as the range of flow rates that can be controlled by a specific type of valve. The standards are influenced by three variables: the valve’s geometry, seat leakage, and the actuator’s precision or stiffness when the valve is almost closed.
The geometry of the seat and closure is fundamental, and severe seat leakage can make the valve unstable as it pushes off the seat. Depending on the shape and valve actuator, rangeability can be estimated with ease. The rangeability is 20:1 if the valve is not precise at 5 percent of stroke. When the rangeability rises, the valve can regulate a broad span of flow rates.
Since several systems do not possess a very broad range of flow rates, it is not essential that the valve has the largest rangeability. The rangeability of ball valves with V-notches is 200:1, while that of globe valves is 100:1. High rangeability often means low sensitivity as the valve opens and decreases as the closing element is close to being shut down.
Are Ball Valves Better Than Diaphragm Valves
In comparison to diaphragm valves, the ball valves are far better. It is because the diaphragm valves have too many drawbacks, making them quite difficult to use. For instance, the diaphragm valves are ideal to be utilized in only moderate pressure situations and modest temperature ranges.
The diaphragm valves are not compatible with multi-turn operations. In addition to that, these valves do not have any face-to-face standard dimensions. Moreover, the body of the diaphragm valves should be prepared from a corrosive resistant substance only. The only drawback of ball valves is that they have poor throttling elements and are a bit hard to clean.
The ball valves offer exceptional ease of operation and are ideal to be used in high-temperature and high-pressure flow. They help to control and maintain the high volume and can perform even without side loads. The jagged construction of these valves assures a long lifespan.
With ball valves, it is possible to inspect and repair seats and seals even with the need to eliminate the valves’ body from the line. Besides that, it does not need lubrication. The cost to buy and maintain the ball valves is relatively less.
How To Choose Between Diaphragm Valve And Ball Valve
The chemical composition of the flow rate, temperature, system media, and pressure should all be taken into account when selecting a valve. It is also important to be aware of any actuation regulations and the intended shut-off reaction rate.
When To Choose Ball Valves
Ball valves are recommended when purchasing valves for the following applications:
- For services involving liquids, gases, and other fluids, low-point drains and high-point vents
- Applications needing bubble-tight service in the air, gas, and liquid
- Device root valves and steam applications
- Systems for feedwater and cooling water
When To Choose Diaphragm Valves
If your business plans to acquire valves for the below-listed applications, it is best to pick diaphragm valves:
- Applications for clean or unclean water and air service
- Systems for demineralized water
- Applications related to cleaning and vacuum
- Corrosive applications
- Systems for rad waste in nuclear facilities
- Systems for manufacturing pharmaceuticals, brewing, and food
Conclusion
Diaphragm or ball valves are used for irrigation, industrial process control, and domestic uses, including on or off valves and laundry washers. However, it is recommended to select ball valves or diaphragm valves based on the particular application and its temperature and pressure regulations.
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