Common Metals & Materials Used in Butterfly Valve Manufacture

Many different materials can be used in the design of a butterfly valve. A typical butterfly valve will use several different materials within its construction to achieve the best combination of functionality and cost. The following briefly describes the most common materials that may be used in the design of an effective butterfly valve, highlighting their relative advantages and disadvantages. 

Advantages of materials used for Butterfly Valves

Carbon Steel

Carbon steel is an alloy of iron where the main alloying element is carbon. Generally, no other alloying elements are added to control the properties of the material. For butterfly valve construction, carbon steel is most often used to form the body and disc of the valve using the sand casting process.

Carbon steels are available in several different grades. The most common grades used for valve bodies and discs are cast grades ASTM A216 WCB (Weldable Cast B-grade) and LCC (Low Carbon Content) steels. WCB material is most suitable for high temperature use, whereas LCC can be used at low (sub-zero) temperatures.

Main Advantage of carbon steel:

The cost - carbon steels are relatively cheap, and valves produced from carbon steels provide a cost-effective solution in environments where other factors are considered less important than cost.

Main disadvantage of carbon steel:

Poor corrosion resistance. This can be overcome by surface protection such as paint, provided that the line media does not corrode the valve from the inside.

Stainless Steel

The definition of a stainless steel is an alloy of iron with a minimum chromium content of 10.5%. The effect of the chromium is to form a self-healing layer of chromium oxide on the surface of the material. When the surface is broken by mechanical damage such as scratching, the chromium quickly reacts with oxygen in the air, so preventing the oxygen from reacting with the iron and forming iron oxide (rust). An ever-increasing number of stainless steels are available, of which the simple iron-chromium-nickel grades are most often termed 'stainless steel'.

Stainless steels can be further classified as ferritic, austenitic, martensitic, duplex and precipitation hardenable. This classification is based on the microstructure that is developed in the material by varying the alloying elements present. For valve construction, the most common grades used are austenitic and duplex. These are described briefly below.

Austenitic stainless steels

Austenitic stainless steels, in addition to chromium, contain elements such as nickel, which have the effect of retaining the high temperature face-centred-cubic austenitic structure at temperatures where it would normally have transformed to the ferritic body-centred-cubic structure. This face-centred cubic structure gives the material improved toughness and ductility compared to the ferritic grades. Depending on the nickel content, the tough austenitic structure can be retained even at extremely low temperatures, allowing the material to be used in cryogenic applications. Improved resistance to pitting corrosion can be achieved by adding molybdenum to the alloy.

Duplex stainless steels

Duplex stainless steels contain a balanced structure of both the austenitic face-centred cubic and ferritic body-centred structure of iron. This structure is developed by carefully controlling both the alloying elements and the heat treatment performed on the alloy to obtain a structure consisting of 50% austenite and 50% ferrite. The result is an alloy that combines the higher strength of ferrite with the improved toughness of austenite. The super duplex grades contain higher levels of chromium and molybdenum to enhance their resistance to pitting and crevice corrosion.

Nickel Alloys

Nickel alloys are used in valve components where severe service conditions are encountered. These alloys are particularly useful in harsh corrosive environments, which would attack stainless steels by breaking down their protective oxide layer.

Hastelloy nickel-based alloys are most often used in valve construction. There are several different forms of Hastelloy, with each being tailored by adding specific alloying elements is varying proportions to suit particular service conditions.

The main disadvantage of nickel alloys is their weight and cost. Nickel alloys have a high density and their cost can be many times that of basic stainless steels.

Titanium Alloys

Titanium alloys combine high strength with light weight and excellent corrosion resistance, having the highest strength-to-weight ratio of any metal. In a similar manner to stainless steels, titanium alloys gain their corrosion resistance by the development of a protective oxide layer on its surface. They are particularly resistant to corrosion by seawater, in particular in systems where hypochlorite is present to prevent biofouling.

The main disadvantage of titanium alloys is their cost, being around ten times as expensive as basic stainless steels or nickel aluminium bronze. The material is also difficult to process due to its highly reactive nature. Special casting techniques are required to prevent reaction with oxygen during melting and pouring.

Nickel Aluminium Bronze

Nickel aluminium bronze is a copper-based alloy containing approximately 10% aluminium, 5% nickel and 5% iron. The nickel aluminium bronze alloys provide excellent corrosion resistance, particularly in seawater environments. They also strongly resist the formation of a bio-film, which can cause increased corrosion problems in stainless steels.

Nickel aluminium bronze has a cost approximately equivalent to that of basic grades of stainless steel. One disadvantage of this material is that it is more anodic than most materials, so that if a nickel aluminium bronze valve is coupled to a stainless steel pipe, then corrosion of the valve in seawater could be fairly rapid.

The above shows that many different materials can be used in valve construction. The ultimate choice depends on several factors including service conditions, cost and required life expectancy. Choice can also be strongly influenced by the material of construction of the pipeline, where galvanic corrosion issues must also be taken into account.

Maharashtra Govt. approves 1600 cr desalination project

 Maharashtra Chief Minister Uddhav Thackeray has approved to set up a desalination project with a capacity of 200 MLD in Mumbai.The project will entail an investment of Rs 1,600 crore. The project will be set up over 30 acre at Manori, Malad, and is expected to be completed in four years. After tapping about six possible locations, the Brihanmumbai Municipal Corporation (BMC) has finalised Manori for setting up the project.The capacity of the plant can be raised to 400 MLD in the future, which can make up for the shortfall of 10 percent of the total water consumption of the city of 3,800 MLD when there is poor rainfall.

The detailed project report will be prepared in around nine months and take another three months to complete the tendering process.The actual completion of the project will need around three more years. The site has been finalised by the technical team as it has no mangroves around it, good quality of water and connected by roads, among other reasonsBMC had tapped five other locations, including Versova, Gorai, Malad, among others for the project. The project will help to make up the shortfall of potable water in summer due to the late arrival of monsoon or shortfall in expected water stock. The operational cost of the project will reduce significantly if operated on solar power.The operational cost of the desalination plant is higher than the dam-based water-supply projects and has been one of 

the reasons behind the delay to the project, which has been planned for years. BMC expects it to be 50% more than its existing system of dam-based water supply.

Desalination is a process that takes away mineral components from saline water. More generally, desalination refers to the removal of salts and minerals from a target substance,as in soil desalination, which is an issue for agriculture.

Saltwater (especially sea water) is desalinated to produce water suitable for human consumption or irrigation. The by-product of the desalination process is brine. Desalination is used on many seagoing ships and submarines. Most of the modern interest in desalination is focused on cost-effective provision of fresh water for human use. Along with recycled wastewater, it is one of the few rainfall-independent water sources.

There are approximately 16,000 operational desalination plants, located across 177 countries, which generate an estimated 95 million m3/day of freshwater.Currently, desalination accounts for about one percent of the world’s drinking water.Desalination is particularly prevalent in countries located in the Middle East and North Africa region, such as Saudi Arabia, the UAE, and Kuwait.Desalination is also an important source of water in the Small Island Developing States.

Due to its energy consumption, desalinating sea water is generally more costly than fresh water from surface water or groundwater, water recycling and water conservation. However, these alternatives are not always available and depletion of reserves is a critical problem worldwide. Desalination processes are usually driven by either thermal (in the case of distillation) or electrical (in the case of reverse osmosis) as the primary energy types.

Currently, approximately 1% of the world's population is dependent on desalinated water to meet daily needs, but the UN expects that 14% of the world's population will encounter water scarcity by 2025.Desalination is particularly relevant in dry countries such as Australia, which traditionally have relied on collecting rainfall behind dams for water.

Kuwait produces a higher proportion of its water through desalination than any other country, totaling 100% of its water use.

Butterfly valves take control

Mark Nymeyer discusses the advantages and limitations of butterfly valves, and highlights developments that are making them more suitable for flow control.

Butterfly valves are lighter, smaller and weigh less than other kinds of control valves, making them the best choice for regulating flow in many applications. Standard butterfly valves have, traditionally, been used for automated on/off applications, a role for which they are well suited. However, when it comes to regulating flow in a closed-loop system, some engineers consider them unacceptable.

Butterfly valves use a rotating disk to control flow through a pipe. The disk is generally operable through 90 degrees, so they are sometimes called quarter-turn valves. Typically, they are used when economy is a consideration. When tight shutoff is needed, butterfly valves with soft elastomer seals and/or coated disks can be used to deliver the required performance. High performance butterfly valves (HPBVs) - or double offset valves - are now the industry standard for butterfly control valves and are widely used for throttling control. They do a good job for applications that have a relatively constant pressure drop or for slow process loops.

Advantages of HPBVs include a straight through flow path, high capacity, and the ability to easily pass solids and viscous media. They generally have the lowest installed cost of any valve type, especially in NPS 12 and larger sizes. Their cost advantages compared to other types of valves, increase dramatically in sizes over 12in.

They can offer good shutoff performance over a wide range of temperatures, and are available in different body designs including wafer, lugged and double flanged. They weigh much less than other types of valves and are more compact. For example, a 12in ANSI class 150, double flanged segmented ball valve weighs 350lb and has a 13.31in face to face dimension, while a 12in lugged butterfly valve equivalent weighs only 200lb and has a 3in face to face.

Limitations

Butterfly valves do have limitations that make them unsuitable for flow control in some applications. These include a limited pressure drop capability compared to globe ball valves with greater potential for cavitation or flashing.

Because the large surface area of the disk acts like a lever, applying the dynamic forces of flowing media to the drive shaft, standard butterfly valves are generally not used in high pressure applications. When they are, actuator sizing and selection becomes crucial.

Oversizing of butterfly control valves sometimes occurs and will negatively impact process performance. This can result from using line-size valves, especially with high-capacity butterfly valves. It can increase process variability in two ways. Firstly, oversizing puts too much gain in the valve, leaving less flexibility when adjusting the controller. Secondly, an oversized valve is likely to operate more frequently at lower valve openings, where seal friction can be greater in butterfly valves. Because an oversized valve produces a disproportionately large flow change for a given increment of valve travel this phenomenon can greatly exaggerate the process variability associated with deadband due to friction.

Specifiers sometimes use butterfly valves for economy or to fit a given line size, without considering their limitations. There is a tendency to oversize butterfly valves to avoid swaging down piping, which contributes to poor process control.

The largest limitation is that the ideal throttling control range is not as wide as a globe or segmented ball valve. Butterfly valves generally do not perform well outside a control range from about 30 to 50% open.

Optimal control performance

In general, when a control loop behaves in a linear manner and the process gain is close to unity, a loop is easiest to control. Therefore, a process gain of 1.0 becomes the objective for good loop control, with an acceptable range of 0.5 to 2.0 (a range of 4:1).

Best performance results when most loop gain comes from the controller. Notice in the gain curve of Figure 1, the process gain gets quite high in the region below about 25% valve travel.

Process gain defines the relationship between changes in process output and input. The travel over which process gain stays between 0.5 to 2.0 is a valve’s optimal control range. When process gain is not within 0.5 to 2.0, poor dynamic performance and loop instability can occur.

Butterfly valve disk design has a significant effect on valve flow rate as the valve travels from closed to open. A disk with an inherent equal percentage characteristic can better compensate for changing pressure drops as the flow changes. Equal percentage trim will give a linear installed characteristic for changing pressure drops, which is ideal. The result is a more accurate, one-to-one change between flow rate and valve travel.

Figure 1: Comparison of globe valve and butterfly valve. The best control occurs when gain is 0.5 to 2.0. Globe valves control well across a broad travel range, but standard butterfly valves are limited to 30-50% travel.

Butterfly valves recently became available with disks having an inherent equal percentage flow characteristic. This delivers an installed characteristic that results in an installed process gain within the desired 0.5 to 2.0 range over a wider travel. This results in significantly improved throttling control, especially in the lower travel ranges.

This design provides good control with acceptable gain of 0.5 to 2.0 from about 11% open to 70%, a control range improvement of nearly threefold when compared to a typical high-performance butterfly valve (HPBV) of the same size. The equal percentage disk thus delivers overall lower process variability.

Butterfly valves with an inherent equal percentage characteristic, such as the Control-Disk Valve, are ideal for processes that require precise, throttling control performance. They can control closer to the target set point regardless of process disturbances, which results in a reduction in process variability.

Improving control

If a butterfly valve is operating poorly, simply replacing it with a properly sized valve may solve the problem. For example, a paper company was using two oversized butterfly valves to control water removal from pulp stock. The two valves were operating below 20% travel, causing process variability of 3.5 and 8.0%, respectively. They spent most of their service life in manual mode.

Two properly-sized NPS 4 Fisher Control-Disk butterfly valves with digital valve controllers were installed. The loops now operate in automatic mode, and process variability went from 3.5% to 1.6% for the first valve, and 8% to 3.0% for the second valve, without any special loop tuning required.

Poor water pressure and flow control from the coolant system in a steel mill caused end product inconsistency. Nine installed HPBVs could not effectively control the flow of water as required.

The mill wanted to install valves that would better control the process, and needed to minimise installed cost. The mill would have spent $10,000 for piping changes per valve to switch from the HPBVs to segmented ball valves. Instead, Emerson suggested its Control-Disk butterfly valves fitting the current HPBV face-to-face dimensions.

One Control-Disk valve was tested side-by-side with one of the nine existing HPBVs, and it performed to specified requirements. The mill replaced the remaining eight HPBVs within the year, each with a Control-Disk valve and this eliminates the need for $90,000 in piping changes for segmented ball valves, and the roughly 25% increased cost of ball valves versus butterfly valves.

The Control-Disk valves provide precise control and help eliminate end-product variability. The steel mill estimated the nine installed Control-Disk valves result in annual savings of about $1 million.  

Conclusions

HPBVs with digital positioners have a lower initial installed cost than most other valve types, and can provide an adequate control range when sized properly. They have high capacity and minimal flow restriction. Butterfly valves with inherent equal percentage trim offer an opportunity for an expanded control range, similar to that of a globe or ball valve and only take up the space of a HPBV.

When selecting valves, especially HPBVs, make sure they are sized correctly, or they could wind up being controlled manually from the control room. It is also important to consider the valve style, inherent characteristic and valve size that will provide the broadest control range for the application.

Mark Nymeyer is a global marketing communications manager at Emerson Automation Solutions for flow controls.

http://handavalve.com/en/article-11441-35247.html

DESW Notice of official holidays-Chinese New Year

Dear Clients and customers, 

We will be off in the period of Feb14-Feb25 during the Chinese New Year celebration.  We accept the quotation at this period of time, but the delivery time will delay. 

The company & factory will be re-opened on Feb 26. 

If there is any urgent matter to contact us in the holidays, please send your message to our mail box, we shall be at your services as soon as possible.

email address: info@deswchina.com or

                      offer@deswchina.com 

DESW

DESW will be at booth T055 16th China International Exhibition on Gases Technology, Equipment and Application (IG, CHINA 2014 ),September 24th-26th,2014 Beijing National Agriculture Exhibition Center,China

DESW will be at 16th China International Exhibition on Gases Technology, Equipment and Application (IG, CHINA 2014 ),September 24th-26th,2014 Beijing National Agriculture Exhibition Center,China

IG, China is an annual event of industrial gas industry, which has been held for 15 years since 1999. With its annually increased number of exhibitors and visitors, this event has won higher appraise from exhibitors and visitors. In order to present the most developed achievements, promote the technical exchanges and enhance the business network and partnership, we choose to head back to Beijing for IG, China 2014 after a marketing survey.

IG, CHINA 2014 will be held at Beijing National Agricultural Exhibition Center (New Hall & Hall 1) on September 24-26, 2014, Welcome to join us!

General Information

16^th China International Exhibition on Gases Technology, Equipment and Application

September 24^th-26^th, 2014   
Beijing National Agricultural Exhibition Center (New Hall & Hall 1)

Organizer:                              
China Gases Industry Association

Co-organizer:

China LNG Association

Producer:
AIT-Events Co., Ltd.  
International Partners：
Asia Pacific Gases Manufacturers Association           
Korean Gases Safety Corporation
Ukraine Association of Industrial Gases Manufacturers 
All India Industrial Gases Manufacturers Association
Korean High Pressure Gases Cooperative Union        
Gases and Welding Distributors Association, USA

India cryogenics Council

Special Endorsement by:
General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic ofChina
State Administration of Work Safety National Energy Administration 

China Petroleum and Chemical Industry Federation
National Technical Committee on Gas Cylinders of Standardization Administration of China
National Technical Committee on Gas of Standardization Administration of China

National Energy Administration

Exhibit Profile

1. Industrial Gases Equipment, System and Technology

Air Separation Solvent Acetylene Vacuum;  Hydrogen Production Pressure Swing Adsorption; Membrane Separation Carbon Dioxide Production; Special Gases and Other Industrial Gases; Special Gases Equipment and Recapture Technology

2. Gases Applications in Food, Environment Protection, Lighting, Building, Material, Mechanical, Electrics, High-Tech,Semi-conductors, Plasma production, Glasses etc.

3. Affiliated Equipment and Suppliers

Air Compressors; Oxygen, Nitrogen, Hydrogen, Carbon Dioxide and Natural Gas Compressors ;Diaphragm Compressors and Turbine Expanders;Valves & Pumps;Thermal Isolation Materials;Gases Cylinders Adsorbent Materials;Gas Filling, Cutting &Welding Equipment;Molecular Sieve Desiccation Equipment

4. Transportation & Packing Suppliers

Various High &Low Pressure Cylinders Hypothermic Liquid Storage Tanks; Aluminum Cylinders Cryogenic Liquid Trucks& Trailers

5 .Gas Analyzers & Instruments and Meters

Dew Point Testers; Mass Spectrometers, Gas Chromatogtraph and Spectrum Analyzer; Alumna Oxygen Content Analyzer Micro-analyzers

6. Cylinder Testing Equipment

Cylinder Hydro Static Testers; Metal Thickness Indicators; Metal Thickness Indicators; Metal Flaw Detectors and Industrial Endoscope; Cylinder Valve Demounting Machines; Automatic-dump Water Machines

7. Medical Gas Equipment

Home-use Oxygen Respirators ;High Pressure Oxygen Cabinets; Hospital Oxygen Supply System and Products

8. Latest Energy Saving Gases and Equipment

Natural Gases & Its Facilities ;New Petrol Welding Gases; Energy Saving; Gasoline Welding Gases

9.Clean fuel gas refueling station and vessels for vehicle
Liquefied Petroleum Gas(LPG) vehicle gas refueling station and cylinder; Compressed Natural Gas(CNG) vehicle gas refueling station and cylinder; Liquefied Natural Gas(LNG) vehicle gas refueling station and cylinder; Natural Gas(NG) and Liquefied Natural Gas(LNG) vehicle gas refueling station and storage tank.

10.RFID and Internet of Things (IOT) In Gas Industry Applications

www.igchina-expo.com/msg.php

Xiamen Valve industry association have officially established in 26th, Jan, 2014. The general manager of DESW(Xiamen) Fluid control Ltd,. Co Dean Chen have selected as the 1st president

Reported by Siting Wu, Xiamen Valve industry association have officially established in 26^th, Jan, 2014. The general manager of DESW(Xiamen) Fluid control Ltd,. Co Dean Chen have selected as the 1^st president.

From the history, Minnan area is famous for manufacturing valve in mainland China. Since 2005, many elites originally from Minnan come to invest in valve manufacturing in Xiamen from all around China. For now, reaching more than 200 valve factories and trading companies established in Xiamen and reached 20 hundred million output valves. Also, more than 10 thousand valve practitioners worked in valve industry and more than 3000 experts in this field. Hence it formed a high quality of industrial chain in valve that reach the international advanced level.   

Our new factory tour photo.

Flickr 上 deswchina 的所有相片。

Our new factory tour photo.

DESW just received AAA enterprise credit

According to Ministry of Commerce of the PRC and new character and problem related to enterprise credit occurred in the internet and B2B environment, based on open, justice and scientific principals, appraised by the third professional organization, the China Association of small and medium enterprise (www.12312.gove.cn ) have shown to the public that the average credit level of enterprise in China. 

 

DESW (Xiamen) Fluid Control equipment Ltd., Co is in the list as follows, 

行业企业信用等级评价初评结果

　序号         企业名称  name of enterprise                 信用等级 Credit level 

1     黑龙江省瑞麒投资担保有限公司                            AAA

2     厦门德尔斯威流体控制有限公司DESW (Xiamen) Fluid Control equipment Ltd., Co   AAA

3     黑龙江龙航工程总承包有限责任公司                     AAA

4     湖南筱沅水利水电建设有限公司                            AAA

5     广饶县大王镇水利建筑安装公司                            AAA

6     北京伟发建筑装饰有限公司                                   AAA

7     厦门天重钢结构有限公司                                       AAA

8     东营市河口区六合水利工程有限责任公司              AAA

9     山东临沂水利水电建筑安装公司                            AAA

10   中科筑城建设工程有限公司                                   AAA

11   北京洛德文博装饰工程有限公司                            AAA

12   北京冠华装饰设计有限公司                                   AAA

13   辽宁发电厂电力建筑安装公司                                AAA

14   厦门敦禾建筑装饰工程有限公司                            AAA

15   北京四方工程建设监理有限公司                            AAA

16   张家界永定水利水电工程有限责任公司                  AAA

17   湖南省桃江县湘中水工机械有限公司                     AAA

18   北京腾境装饰工程有限责任公司                            AAA

19   北京鹤延龄中药饮片有限公司                                AAA

20   湖南鑫旺水利水电建设有限公司                            AAA

21   湖南兴盛水利水电工程建设有限公司                     AAA

22   北京万兴世贸国际家居建材有限公司                     AAA

23   厦门日华科技股份有限公司                                   AAA

24   湖南联邦建筑装饰工程有限公司                            AAA

25   深圳市金运视讯设备有限责任公司                         AAA

26   东莞市东尚木业有限公司                                       AAA

27   兰州昱瑞暖通设备有限公司                                   AAA

28   甘肃南园清真食品有限公司                                   AAA

29   重庆博张机电设备有限公司                                   AAA

30   重庆巴牛食品有限公司                                          AAA

31   陕西康鼎建筑劳务有限公司                                   AAA

32   陕西普华兔业专业合作社                                       AAA

33   陕西凯林信息科技工程有限公司                            AAA

34   西藏金凯新能源技术开发有限公司                         AAA

35   山西新域房地产开发有限公司                                AAA

36   云南加顺饲料有限责任公司                                   AAA

37   云南昊宸钢结构工程有限公司                                AAA

38   吉林省晟瑞建筑材料有限公司                                AAA

39   陕西海兰净合环境治理工程有限公司                     AAA

　

 联系地址：北京市海淀区中关村大街19号新中关大厦B座1109

　联系人：闫敏 电话： 010-53697782

　　                                                                                      中国中小企业协会

　　                                                                                       2014年1月10日

bcp.12312.gov.cn/article

Dec 18th CEC forum webinar-DESW foreign trade department attended 10th practical manager forum webinar in China in 2013: China Entrepreneurs exploration aboard strategy.

DESW foreign trade department attended 10th practical manager forum webinar in China in 2013: China Entrepreneurs exploration aboard strategy faced with Francisco J. Sánchez former vice deputy of US business department and Yifu Lin, vice president of World bank. 

Faced with opportunities, challenges are still obstacles while the suppliers need to rethink about all the raising costs in many perspectives.   

Yifu Lin is talking about the economy status around the world. 

According to the data collected by Global Sources, the manufacturer in China for next year is still prospective and promising. 

 Due to the overweighting of costs in producing includes labor, raw materials, and money rotation, competition merits count much in terms of innovation, brand, quality, service, marketing, human resources and productivity ability.

Finally, the hoster advice the buyers to cooperate deeply to win win situation. 

New samples in carbon and stainless high performance butterfly valves and ball valves.

Flickr 上 deswchina 的所有相片。

New samples in carbon and stainless high performance butterfly valves and ball valves.