Plug valve VS ball valve

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Plug valve with one piece top -entry design has a lot of similarities with a one piece top – entry ball valve. Strictly speaking, ball valve and plug valve are the same types of valve due to their similar function and characteristics and both of them have a very wide range of applications. Today we will introduce the difference of plug valve and ball valve.

Plug valve also known as cock valve, rotating plug valve, is a kind of oldline valve. The valve “plug” (mostly conical or cylinder) combined and the body of the conical hole surface of the sealing, to move depending on the plug body around the center line of the valve to achieve open and close. It is mainly used for cutting, distribution and change the flow of media. The plug valve is simple in structure and small in size. It can be opened and closed by only 90% rotation. It is widely used in a low pressure, small diameter and medium or low-temperature occasions. Plug valve sealing surface is easy to wear, also easy to get stuck in the occasion of high temperature or high pressure, not suitable for flow regulating.

The ball valve is evolved from the plug valve with a ball as its closing parts, it around the center of the valve to achieve the opening and closure, mainly used to cut off, distribution and change the flow direction of the medium. Ball valves can close tightly just 90 degrees of rotation or a small torque. Full horizontal of the valve body cavity provides little resistance, through the flow path for the medium. The main characteristics of the ball valve are compact structure, easy to operate and maintenance, suitable for water, solvent, acid and natural gas and other general media, also suitable for working conditions of harsh media, such as oxygen, hydrogen peroxide, methane and ethylene. The ball valve body can be one piece, can also be combined. It is generally considered that ball valves are most suitable for opening and closing directly, but recent developments have designed them for throttling and flow control.

 

Plug valve VS ball valve

Different principle

The ball valve is evolved from the plug valve. They have the same 90-degree rotation operation, but depends on the “plug” is a plug or a ball with a circular through hole or channel passing through its axis. The ball and the ports should look like this: when the sphere rotates by 90 degrees, it will appear as a sphere at the inlet and outlet to cut off the flow. For the plug valve, the conical plug and the body surface formed by the conical pressure, the upper parts are sealed with packing between the plug and the gap between the body. Plug valve is simple and often economical because it usually does not have bonnets, but the handle exposed outside at the end instead.

Different application

Plug valves offer better performance in the term of cutting than ball valves, but that doesn’t show obviously. The sealing surface of the plug valve is much larger than the ball valve and supplies a better sealing effect, but a greater torque and small diameter. The ball valve is ideal for switching pipeline medium, not as a throttle valve to avoid the valve long time by medium erosion and loss of tightness. Now the sealing effect of the ball valve has been greatly improved with the progress of the sealing technology, so we can say that the plug valve is used for the sealing requirements are strict but the diameter is not large, and the ball valve is used for the sealing effect is not too strict and the diameter is large.

Plug valve is lower cost

For the plug valve, the “plug” is completely covered by the bushing, making the valve body and plug free from wear. Replacement of the bushing and top seal can complete the repair and update of the valve, which can meet the long-term service requirements of 300℃. This has considerable competitive advantages over other hard-sealed metal ball valves in this temperature range. In addition, the plug valve processing area only is the top face and flange, other parts all one-step casting molding and the internal body need no processing. Compared with the ball valve, it offers low processing allowance, when making the INCONEL, MONEL, HAST alloy and other special materials as its materials, plug valve has an obvious price advantage.

What’s the difference between metal seat valves and soft seat valves?

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When choosing an industrial valve, you will face numerous choices. Available materials, proper size, and design (1, 2, or 3 pieces, end connections, etc.) are the key factors to decide which type of valve to use. Equally important is the type of valve seats which directly determines the leakage class of the valve. Before you choose the right valve seats, you must know the following question: Is the medium corrosive? Contains abrasive particles? For high temperature or high pressure? Once you know these things, you will make the right choice. Therefore, the first step to fully understand your craft condition: choose a suitable valve seat.

Almost all the industrial valves are metal seat and soft seat available. Both of them offers excellent sealing performance and have their unique and irreplaceable advantages, and inevitably, due to the shortcomings, costs, abrasion resistant performance, working conditions of different materials, metal-seated valves and soft-seated valves both have their markets and long-lasting solutions for critical applications. The table below showed the advantages and disadvantages of metal seat valves and soft seat valves.

Metal seat VS soft seat:

Valves Metal seat Soft seat
Material Copper alloy (for low-pressure valves);

Chrome stainless steel (for medium and high-pressure valves);

Satellite Seat Surface (High temperature and pressure valves and highly corrosive valves);

Nickel-based alloys (for corrosive media);

Metal-ceramic sealing material, etc

 The elastic nonmetallic material such as PTFE（Temperature -50°F to 400°F);

modified PTFE( Temperature -50°F to 450°F);

Delrin（High pressure up to 5000psi dependant on valve size and temperature range of -50°F to 180°F）；

Nylon（Temperature rating -30°F to 200°F;

PEEK（Temperature -70°F to 550°F）；
Manufacturing  process

 

 Need grinding, hardening and other precision processing. High precision requirements, complex processing and long production cycle Easy deformation, low processing accuracy, even free-processing
Medium

 

 Hot water, gas, gas, oil, acid and alkali medium Air, water and other non-corrosive media
Working pressure Medium or high pressure above 3.5mpa Medium or low pressure
Working  temperature

 

 Metal seated valves are suitable for temperature up to 540℃ (Higher based on the material of body and trim). Soft seated ball valves are suitable for the working temperature lower than 260℃. Aging easily affected by temperature, used in room temperature environment. Fire protection is needed to prevent leakage at high temperatures.
Leakage class(Ball valve) Class V and VI VI
Cost & Price Metal seat valve is much higher than soft seat valves Cheaper than metal seat valves
Sealing performance Wear resistance but easy to leak relatively poor sealing performance Easy to wear and can achieve a high level of sealing performance or even zero leakage

 

 

New products: Intelligent voice-activated valve

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There are too many types of valve in industrial fields. Intelligent valve transmission command information through digital communication and network, such as valve opening, operation times, operation speed, output torque and other valves. It can remotely set the valve opening range, change valve characteristics, adjust blind area and remote adjustment.

The PERFECT factory has developed a unique intelligent voice-controlled valve. The in-ear earphone has the ability to sense the environment and can connect the external cavity of the earphone with the internal cavity. Most products on the market receive external sound through the electrical signal of the microphone, which will increase the power consumption, while the first miniature acoustic control valve will not. Due to the fact that the micro-acoustic electronic valve is a physical channel, the ambient sound received by it has not been processed twice. Compared with the electrical signal of the microphone, it sounds more natural without delay and distortion.

Over the past years, PERFECT has cooperated with many research and development institutions to make every product in good faith. With our unique technical advantages and rich production experience, coupled with strict product testing, our company has always been committed to providing innovative solutions to optimize the user experience.

What’s the advantages and disadvantages of plug valve?

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Plug valve is a kind of fast on-off through conduit valve, the friction caused by the movement between the sealing surface under the condition of fully-open can completely prevent the contact with the flowing medium, therefore it can usually be used for the medium with suspended particles. In addition, plug valves are easily adapted to a multi-ports design, where a valve can have two, three, or even four different ports, which simplifies piping design and reduces valve usage and connection accessories. Plug valve is characterized by its long service life and high reliability, which is a good choice for many corrosive, abrasive, toxic, continuous operation and other media and devices, widely used in the chemical industry. Here we will discuss the advantages and disadvantages of plug valve in details?

The advantages of the plug valve:

  1. The one-piece, top entry body of plug valve design, simple structure, easy maintaining in line, leak free and can withstand more strength piping system. The medium used in the chemical industry has strong corrosion, so the valve body used in the chemical process must have strong permeability and resistance to intergranular corrosion. The valve body of the plug valve is made of grade II casting quality, grade V precision high grade casting steel.
  2. The open and close parts namely the plug is completely covered by the bushing, making the valve body and plug without wear. The valve can be repaired and updated by simply replacing the economical bushing and the top seal, which can meet the long-term service requirements under the high-temperature environment up to 300℃. Compared with the metal-sealed ball valves in the same application, it offers a considerable competitive advantage.
  3. The plug valve parts are all cast one-off except the top and flange, the valve body without processing. compared with the ball valve it has the advantage of low processing allowance, when the material for INCONEL, MONEL, HAS alloy and other special materials, supplying an obvious price advantage.
  4. Plug valve can be customized according to the needs of users with a variety of designs, can be made into three ports, four ports, five ports, six ports, multi-valve group or jacket types, etc.
  5. The cover seal plug valve without a gap is similar to a no-gap ball valve that reducing the gap between the valve ball and the valve body to 1-3 mm ball valve design, can not achieve the advantages of an enveloped cover seal. This special feature makes the plug valve suitable for many harsh media such as easy crystallization, viscosity, containing catalyst particles and corrosion fluid deposition.

The disadvantages of plug valve compared with ball valve:

  1. It can be said that the ball valve is developed based on the plug valve, the plug valve cover sealing design improves the requirements of driving torque. When valves equipped with pneumatic actuator, plug valve needs to be equipped with a larger actuator and accessories than the ball valve, increasing the use cost. For PP material, the plug valve used for the main shutoff valve, but the high-frequency shutoff valve used the ball valve, so the pneumatic plug valve is used in the key cutting position as a high-reliability shutoff valve, but is not recommended for the regulating application, because high-frequency shutoff is not the advantage of the plug valve.
  2. plug valve cannot be used as throttling. In some applications, inappropriate lined material or lined release areas improper design of the valve body will result in swelling of the PTFE liner and multiple changes in the drive torque required for the plug valve.
  3. The plug valve one-time investment is higher than the ball valve, but for the long run, plug valve is economical due to its high reliability, low total cost and other incomparable advantages.

How to distinguish the globe valve and gate valve?

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Globe valve and gate valves are the most frequently valves in piping systems, someone may be confused about them due to their similarities in structural construction, material grades, trims and other technical specifications. Here we will teach you how to distinguish the globe valve and gate valve.

 

Difference structural and installation

Gate valves are more complex in structure and larger in size than globe valves. In the case of the same diameter, gate valves are higher than globe valves. So please note that rising stem gate valves require higher height space. In addition, the gate can be structural shaped like a wedge, knife, or parallel construction but globe not。

A gate valve can be installed in various directions while a globe valve only goes in one direction. The globe valve has two ways of installation, one is making the medium bottom entry from the valve core, when the valve is closed the disc is not under pressure, thus can extend the service life of the disc and can be replacement disc in front valve pipe pressure, however, the disadvantage is that the drive torque of the valve is large, which is about 1 time of the upper flow, and the axial force of the valve stem increases, which makes it easy to bend. So this method is generally only applicable to small diameter globe valve (DN50 below). The globe valves above DN200 are designed to make the medium top entry(The electric globe valve generally uses top entry).

 

Difference working principle

Globe valve can be used not only on cutting off, but also throttling and flow regulation applications. The fluid resistance of the globe valve is large, while the distance between the valve plate and the sealing surface is short, so the opening and closing is laborious and the travel is short. When the globe valve opens and closes, the handwheel rotates and lifts with the stem. But for gate valves, the stem moves up and down without changing the position of the handwheel itself. Gate valve is only fully open or fully closed, the travel of the gate is large and cost long the closing time. Gate valve is a general service valve that is used primarily for on-off, non-throttling applications.

 

Different flow

Gate valve operates in two direction and two-way flow. Gate valve runner in a horizontal line and the ordinary gate valve has a small flow resistance coefficient, that is about 0.08~0.12.

Globe valves will only work in one direction and it has a larger amount of fluid trapping in the line due to the direction of flow. The flow resistance of ordinary globe valve is 3-5 times that of gate valve, and the sealing can only be achieved by forced closing. The valve core of the globe valve only contacts the sealing surface when it is completely closed, so the wear of the sealing surface is very small. Globe valves with actuators should pay attention to torque control mechanisms.

 

Different sealing

The sealing surface of the globe valve comes from a small trapezoidal-shape side of the valve core (refer to the shape of the valve center for details), and the valve can be closed when the valve center falls off (large pressure difference leading to poor closure effect but good anti-reverse). Gate valve can be sealed by means of media pressure and sealing surface, the valve core and valve seat sealing surface always contact and rub each other when opening and closing, the sealing surface is easy to wear, the sealing effect is not as good as the globe valve, even if the valve center falls off, it will not cause the valve closure like the globe valve.