News Archives

What is butt welding? (1)

September 29, 2020

Butt resistance welding (hereinafter referred to as butt welding) is a type of resistance welding method that uses resistance heat to weld two workpieces along the entire end surface at the same time. Butt welding has high

welding

productivity and easy automation, so it is widely used.
Application of butt welding:
Butt welding has high productivity and easy automation, so it is widely used. Its application range can be summarized as follows:
(1) The length of the work piece, such as the butt welding of strip steel, profile, wire, steel bar, rail, boiler steel pipe, oil and natural gas transportation pipeline.
(2) Butt welding of annular workpieces, such as car rims and bicycles, motorcycle rims, butt welding of various chain links, etc.
(3) Assembling welding of components The simple rolling, forging, stamping or machining parts are butt-welded into complex parts to reduce costs. For example, butt welding of automobile steering shaft shell and rear axle housing, butt welding of various connecting rods and tie rods, and butt welding of special parts.
(4) Butt welding of dissimilar metals can save precious metals and improve product performance. For example, the butt welding of the working part of the tool (high-speed steel) and the tail (medium carbon steel), the butt welding of the head (heat-resistant steel) and the tail (structural steel) of the exhaust valve of an internal combustion engine, the butt welding of aluminum and copper conductive joints, etc. .
Classification of butt welding:
Butt welding is divided into resistance butt welding and flash butt welding.
Resistance butt welding
Resistance butt welding is a method in which the end faces of the two workpieces are always pressed tightly, heated to a plastic state by resistance heat, and then upset pressure is quickly applied (or no upset pressure is applied and only the pressure during welding is maintained) to complete the welding.
One, resistance and heating of resistance butt welding
The resistance distribution during butt welding is shown in the figure. The total resistance can be expressed by the following formula:
R=2Rω+RC+2Reω
where Rω-the internal resistance of the conductive part of a workpiece (Ω);
Rc–the contact resistance between two workpieces (Ω);
Rω–The contact resistance between the workpiece and the electrode (Ω);
The contact resistance between the workpiece and the electrode is usually ignored due to its small resistance and far from the joint surface.
The internal resistance of the workpiece is proportional to the resistivity ρ of the welded metal and the length l0 of the workpiece extending from the electrode, and inversely proportional to the cross-sectional area s of the workpiece.
Same as spot welding, the contact resistance of resistance butt welding depends on the surface condition, temperature and pressure of the contact surface. When the contact resistance has obvious oxides or other stolen goods, the contact resistance is large. The increase in temperature or pressure will reduce the contact resistance due to the increase in the actual contact area. At the beginning of welding, the current density at the contact point is very large; after the end surface temperature rises rapidly, the contact resistance decreases sharply. When heated to a certain temperature (steel 600 degrees, aluminum alloy 350 degrees), the contact resistance disappears completely.
Like spot welding, the heat source during butt welding is also the resistance heat generated by the resistance of the welding zone. In resistance butt welding, the contact resistance exists for a very short time, and the heat generated is less than 10-15% of the total heat. But because this part of the heat is generated in a very narrow area near the contact surface. Therefore, the temperature in this area will increase rapidly, and the internal resistance will increase rapidly. Even if the contact resistance disappears completely, the heat generation intensity in this area is still higher than other places.
The harder the welding rod used (that is, the larger the current and the shorter the energization time), the smaller the pressing force of the workpiece, and the more obvious the influence of contact resistance on heating.

Classification and characteristics of welding

September 29, 2020

Metal welding can be divided into three categories: fusion welding, pressure welding and brazing according to the characteristics of the process. The characteristics are:
1. Fusion welding: heat the workpiece to be joined to partially melt it to form a molten pool. The molten pool will be joined after cooling and solidification. If necessary, a filler can be added to assist. It is suitable for welding of various

welding

metals and alloys without pressure. .
2. Pressure welding: The welding process must apply pressure to the weldment, which belongs to the processing of various metal materials and some metal materials.
3. Brazing: Use metal materials with a lower melting point than the base material as the brazing filler metal, and use the liquid brazing filler metal to wet the base material, fill the joint gap, and mutually diffuse with the base metal to realize the connection of the weldment. Suitable for welding of various materials, and also suitable for welding of different metals or dissimilar materials.

Welding equipment can be divided into manual welding equipment and automatic welding equipment according to the degree of welding automation.
During the welding process, if the atmosphere is in direct contact with the high-temperature molten pool, the oxygen in the atmosphere will oxidize metals and various alloying elements. Nitrogen and water vapor in the atmosphere enter the molten pool, and will also form pores, slag inclusions, cracks and other defects in the weld during the subsequent cooling process, which will deteriorate the quality and performance of the weld.
There are many energy sources for modern welding, including gas flame, electric arc, laser, electron beam, friction and ultrasonic. In addition to being used in factories, welding can also be carried out in a variety of environments, such as the field, underwater and space.

No matter where it is, welding may bring danger to the operator, so appropriate protective measures must be taken when welding. The possible harm caused by welding to the human body includes burns, electric shocks, visual impairment, inhalation of toxic gases, and excessive ultraviolet radiation.
In order to improve the welding quality, various protection methods have been developed. For example, gas shielded arc welding is to isolate the atmosphere with argon, carbon dioxide and other gases to protect the arc and molten pool rate during welding.

For example, when welding steel, adding ferro-titanium powder with high oxygen affinity to the electrode coating for deoxidation can protect the beneficial elements such as manganese and silicon in the electrode from oxidation and enter the molten pool. After cooling, high-quality welds can be obtained.

The common feature of various pressure welding methods is to apply pressure during the welding process without adding filler materials. Most pressure welding methods, such as diffusion welding, high frequency welding, cold pressure welding, etc., do not have a melting process, so there is no problem like fusion welding, which has beneficial alloying elements burning and harmful elements intruding into the weld, thus simplifying the welding process. It also improves welding safety and health conditions.

At the same time, because the heating temperature is lower than that of fusion welding and the heating time is shorter, the heat affected zone is small. Many materials that are difficult to weld by fusion welding can often be welded by pressure welding to form a high-quality joint with the same strength as the base metal.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Valve model establishment and meaning

September 27, 2020

The latest valve model compilation method
Nowadays, there are more and more types of valves and materials, and the compilation of valve models is becoming

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

more and more complicated. The standardization of valve models provides convenience for valve design and selection. Although my country has a unified standard for valve model compilation, it is gradually unable to meet the needs of the development of the valve industry. At present, valve manufacturers generally adopt a unified numbering method; if a unified numbering method cannot be used, each manufacturer can work out a numbering method according to its own situation.
The valve model compilation method specifies the valve model description, valve type, drive mode, connection form, structure form, sealing surface material, pressure and the expression method of the valve body material code. The valve model preparation method is suitable for all kinds of pipeline valves such as gate valves, globe valves, throttle valves, butterfly valves, ball valves, diaphragm valves, plug valves, check valves, drain valves, plunger valves, pressure reducing valves, traps, and safety valves. product. Standard valve model representation method The valve model compilation method should usually indicate the valve type, drive mode, connection form, structural characteristics, nominal pressure, sealing surface material, valve body material and other elements.
Unit One , valve type (code name):

butterfly valve	safety valve	Diaph-ragm valve	ball valve	gate valve	check valve	plug valve	Pressure reducing valve	globe valve	filter	Disch-arge valve
D	A	G	Q	Z	H	X	Y	J	GL	FL

Unit two, valve drive mode (code name):

drive mode	Electro-magne-tism	Electro-magnetic hydraulic	Electro-hydraulic	tur-bine	Spur gear	Bevel gear	pneu-matic	Hydr-aulic	Gas-hydr-aulic	elec-tric	han-dle	Hand-wheel
code	0	1	2	3	4	5	6	7	8	9

Unit three, valve connection method (code name):

connection	internal thread	external thread	two different connections	flange	welding	wafer	clamp	ferrule
code	1	2	3	4	6	7	8	9

Unit Four, valve structure (code name):

Butterfly valve structure (code name):

butterfly structure		butterfly code	butterfly structure		butterfly code
sealed	singl eccentric	0	unsealed	single eccentric	5
	center vertical plate	1		center vertical plate	6
	double eccentric	2		double eccentric	7
	triple eccentric	3		triple eccentric	8
	linkage mechanism	4		linkage mechanism	9

Gate valve structure (code name):

gate valve structure types				gate valve code
valve stem lift type	Wedge gate plate	Flexible gate plate		0
		rigid gate plate	single gate	1
			double gates	2
	Parallel gate plate		single gate	3
			double gates	4
non-lifting valve stem	Wedge gate plate		single gate	5
			double gates	6
	Parallel gate plate		single gate	7
			double gates	8

Ball valve structure (code name):

ball valve structure		code	ball valve structure		code
floating ball	Straight flow channel	1	fixed ball	Straight flow channel	7
	Y type three-way channel	2		four-way channel	6
	L type three-way channel	4		T type three-way channel	8
	Y type three-way channel	5		L type three-way channel	9
				Hemisphere through	0

Check valve structure (code name):

check valve structure		code	check valve structure		code
lifting disc	straight flow channel	1	swing disc	single disc	4
	vertical structure	2		multiple discs	5
	angle channel	3		double disc	6
			butterfly type check valve		7

The structure of stop valve, throttle valve and plunger valve (code name):

globe valve structure		code	globe valve structure		code
disc type unbalanced	straight flow channel	1	disc type balanced	straight flow channel	6
	Z channel	2		angle channel	7
	three-way channel	3
	angle channel	4
	DC runner	5

Diaphragm valve structure (code name):

diaphragm valve structure	code	diaphragm valve structure	code
Roof circulation	1	straight flow channel	6
DC runner	5	Y type angle channel	8

Plug valve structure (code name):

plug valve structure			plug valve structure
packing seal	straight flow channel	3	oil seal	straight flow channel	7
	T type three-way channel	4		T type three-way channel	8
	four-way channel	5

Safety valve structure (code name):

safety valve structure		code	safety valve structure		code
Spring loaded spring seal structure	full open type with heat sink	0	spring loaded,spring not close, with wrench	micro-open, double valve	3
	micro-open	1		micro-open	7
	full open	2		full open	8
	full open with wrench	4
leverage	single leverage	2	with actuator full open		6
leverage	double leverage	4	pulse		9

Structure of pressure reducing valve (code name):

pressure reducing valve structure	code	pressure reducing valve structure	code
film type	1	bellows type	4
spring film type	2	leverage type	5
piston type	3

The structure of the trap (code name):

trap	trap code	trap	trap code
float ball type	1	steam pressure type or bellows	6
float bucket	3	bimetallic	7
liquid or solid expansion type	4	pulse	8
bell float	5	disc thermaldynamic	9

The structure of the blowdown valve (code name):

blowdown valve structure		code	blowdown valve structure		code
liquid level connection discharge	cut-off straight through	1	Discontinuous discharge	Cut-off type DC	5
	cut-off angle	2		Cut-off straight-through	6
				Cut-off angle	7
				Floating gate type straight-through	8

Unit five, valve sealing material (code name):

material	Babbitt alloy	enamel	Nitrided steel	18-8series stainless steel	Fluoroplastic	hard alloy
code	B	C	D	E	F	Y
material	nylon plastic	monel	lead lining	Mo2Ti stainless steel	plastic	monel alloy
code	N	P	Q	R	S	M
material	glass	copper alloy	Cr13 stainless steel	rubber	lining	valve material machined directly
code	G	T	H	X	J	W

Unit six, valve nominal pressure (code name): The valve nominal pressure value is directly expressed with Arabic numerals, which is 10 times of MPa. The pressure of 1.0MPA is DN=1.0MPA and the nominal pressure is 10kg. Indicates the nominal pressure of the valve!
Unit seven, valve body material (code name):

valve body material	Titanium and titanium alloys	carbon steel	Cr13 series stainless steel	Chrome-molybdenum steel	malleable cast iron	aluminum alloy
code	A	C	H	I	K	L
valve body material	ductile cast iron	Mo2Ti series stainless steel	plastic	copper and copper alloy	18-8series stainless steel	grey cast iron
code	Q	R	S	T	P	Z

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Types of valve accessories

September 25, 2020

Types of valve accessories: The valve itself is composed of a valve body and various operating mechanisms, which also contain many parts and accessories, including manual, pneumatic, electric and so on. The components assembled in different ways of use are also different.
Valve accessories mainly include:
1. Pneumatic actuator: It is mainly divided into single-acting and double-acting. Single-acting is a spring-return

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

structure, and double-acting is the principle of air opening and closing. Generally, double-acting pneumatic actuators are used for adjustment types. 2. Electric actuators: the common ones are linear, angular, compact and explosion-proof. The structure of the electric actuator is relatively complex and the cost is high, but its performance is stable, open and close quickly, and it is suitable for remote control systems.
3. Hydraulic actuator: A hydraulic actuator is a device that converts hydraulic energy into mechanical energy. There are mainly linear and rotary types. The cost is relatively high and the structure is relatively complex. It is a product with special working conditions and high requirements, and the market generalization rate is low.
4. Gas-liquid linkage actuator: The gas-liquid linkage actuator uses pipeline natural gas or nitrogen as power and hydraulic oil as the transmission medium to drive the opening and closing of pipeline valves. It is mainly used as a multifunctional driving device in natural gas, liquefied gas, nitrogen, gas liquid tank, gas, etc.
5. Electro-hydraulic linkage actuator: The electro-hydraulic linkage actuator is composed of a control module and a power module. The intelligent controllable motor accepts the function commands of the control module, controls the power module, and outputs the large distance in line or angular displacement, pneumatic control The object, at the same time, completes the adjustment process through its own displacement feedback, and realizes various functional controls.
6. Manual actuator: The manual actuator is to perfect the manual control when the current is unstable and the air pressure is insufficient. When the air pressure and current cannot be controlled under special circumstances or there is no current and air pressure for installation and maintenance, the manual feedback device can be turned on, which can be carried out quickly Manual control.

Valve components:
Handle, handwheel, worm gear, valve body, valve core, valve stem, valve cover, valve silencer, blank, bolt and nut, clamp, spring, diaphragm, packing, packing, O-ring, PTFE products Gaskets, flanges, non-standard solid parts, etc.
Positioner and accessories:
Pneumatic valve positioner, electric valve positioner, intelligent valve positioner, electro-hydraulic server, servo amplifier, electric converter, filter pressure reducing valve, valve position transmitter, position valve, solenoid valve, limit switch, pneumatic Amplifier, smart module, electro-hydraulic server, servo amplifier, alarm, explosion-proof coil, quick exhaust valve
Other valve accessories:
Valve testing machine Handle Handwheel Worm gear valve Body Valve core Valve cover Valve silencer Signal generator Rough mold bolts and nuts Clamps Springs Diaphragm Packing O-rings Flow juice Polytetrafluoroethylene products Gaskets Flanges Fast elbows Joint expander Flow meter Filter non-standard solid parts

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Working principle diagram of three-way valve

September 25, 2020

What is a three-way valve? Simply put, a three-way valve has three inlets and outlets; when the three-way merges, there are two in and one out, and the three-way split is one in and two out. It is controlled according to the shape of the spool. The most obvious difference in appearance between a three-way valve and a two-way valve is one more flow passage. The three-way valve is mainly used to change the flow direction of the medium. In addition to the inlet A, the outlet B, and the reversing port C, ordinary valves do not have the function of changing the flow direction of the medium.

T, L type port valve

Three-way valve structure: Three-way valves are generally divided into L-type and T-type. The T-shape can connect three orthogonal pipelines with each other and cut off the third channel, which can split and merge. The L shape can only connect two orthogonal pipes, and cannot maintain the third pipe to communicate with each other at the same time. It only plays a role of distribution.
Principle of three-way valve:
When the valve opens, the medium enters the valve from A, and flows out of the valve through B. When the bypass requires medium to flow in, the actuator is opened, the valve core is reversed, and medium A enters C out. When the pipeline does not require medium to flow in, the actuator is opened and the valve close Cut off the media.
Three-way solenoid valve:
There are several working positions of the spool. The solenoid valve is called several solenoid valves: the interface on the valve body, which is the number of passages of the solenoid valve, has several passage ports, and the solenoid valve is called a few-way solenoid valve, which means two Position means that there are two working positions that can be switched, and the three-way has three channels for ventilation.
Two-position, two-way, two-position, three-way solenoid valve principle The solenoid valve is one in and one out (two channels); one channel is connected to the air source, and the other channel is connected to the air inlet of the actuator;

Three-way solenoid valve

The two-position three-way solenoid valve controls the gas to be one inlet, one outlet and one exhaust (there are two working positions); one channel is connected to the air source, the other two channels are connected to the air inlet of the actuator, and one Adjacent to the exhaust port of the actuator;
The two-position five-way solenoid valve controls the gas to be one inlet, two outlets and one exhaust (the working position is also two); 1 air inlet (connected to the air source), 1 positive action vent hole and 1 * as a vent hole (Separately provide the target equipment with one positive and one* air source), 1 positive action exhaust hole and 1 *exhaust hole (installation*);
The three-position five-way solenoid valve controls the gas to be one in, two out and one exhaust (but there are three working positions); 1 air inlet (connected to the air source), 1 positive action vent hole and 1 * as a vent hole (Separate the air source provided for the target equipment in one positive and one *), 1 positive action vent and 1 ** vent (installation*).
Principle of three-way solenoid valve:
One in and one out: Normally closed (ZC2/3)—When the solenoid valve coil is energized, port 2 leads to port 1, and port 3 is closed; when the solenoid valve coil is de-energized, port 2 is closed and port 1 leads to Port 3; Normally open (ZC2/3K) When the solenoid valve coil is powered off, port 3 leads to port 1, and port 2 is closed; when the solenoid valve coil is energized, port 3 is closed, and port 1 leads to port 2;
One input and two output: (ZC2/31) When the solenoid valve coil is energized, the first circuit of the medium outlet (2) is opened and the second circuit (3) is closed; when the solenoid valve coil is de-energized, the first circuit of the medium outlet is closed. (2) Close, the second way (3) opens;
Two in and one out: (ZC2/32) When the solenoid valve coil is energized, the first circuit (2) of the medium inlet is opened, and the second circuit (3) is closed; when the solenoid valve coil is de-energized, the first circuit of the medium inlet (2) Close, and the second way (3) opens; (Check valves must be added before the two inlet ends of the inner valve)

World Famous Valve Brand Ranking

September 24, 2020

If you talk about trusted brands abroad, different valves have different manufacturers, and each imported valve

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

company is involved in different fields, and each brand has its own advantages. The explanation for imported valve brands is to let users know more about imported valve brands. It is a comprehensive selection based on the brand awareness, quality level, after-sales service, innovation ability, consumer reputation and other indicators of each imported valve company. Customers can help when purchasing imported valve products.
FISHER Fisher valve (USA), According to different requirements, Fisher valve adopts American ANSI/API, British BS, Japanese JIS, German DIN, national standard GB and other standards for design, manufacture and inspection. The main products are soda ash special valve, ceramic ball valve, clay valve, oxygen special valve, pneumatic/electric control valve, self-operated control valve, metal hard seal ball valve, high temperature butterfly valve, air separation system butterfly valve, disc valve, metal hard seal butterfly valve, thick Special valves for nitric acid, ball valves, globe valves, check valves, flat gate valves, power station valves and non-standard special valves.

Masoneilan Valve (United States), In the field of valve control, Masoneilan has set a number of firsts: the first to develop a design concept that greatly simplified the valve diameter; the first to develop the top guide and bottom guide technology of the control valve; First developed the first universal control valve (Camflex); first invented a method to reliably predict the noise during the calculation and design of the control valve.
kitz Kitzawa Valve (Japan), Kitz Kitzawa Valve (Japan) was founded in 1951 and has become one of the world’s leading integrated valve factories. The company not only produces valves for general equipment and various industrial complete sets of equipment, but also produces valves for automatic operation and testing equipment. In Beize, from casting, forging processing to assembly, serial production is carried out under strict quality management. In addition, when leaving the factory, the products are strictly inspected in accordance with the “Quality Assurance Regulations” formulated by the company, so they are well received by users all over the world.
HANK Hank Valve (Germany), HANK Hank Valve was founded in Mönchengladbach in 1852. Hank Valve is a multinational production company that is famous for producing high-quality, advanced valves, measurement and control systems. It has subsidiaries and branches in dozens of countries around the world. The main products are pneumatic valves, water supply and drainage valves, hydraulic ball valves, cryogenic valves, high temperature and high pressure valves, imported butterfly valves, imported plug valves, imported stop valves, hydraulic ball valves, imported needle valves, imported ball valves, etc.
OTTO Valve (France), The French OTTO Valve Company was established in Paris, France in 1805 and has a history of more than 100 years. At the beginning of its establishment, France OTTO Valve was only a stainless steel valve manufacturer, but now France Otto is one of the top 500 companies in the Midwest of France, with 15 manufacturing centers in the United States, Germany, the United Kingdom and Italy. Among them, 10 manufacturing centers have passed ISO9001 quality certification, and their products cover a variety of fields in the fluid control industry.
KSB Valve (Germany), Germany KSB is a world-renowned modern large company that manufactures pumps and valves. It is one of the three largest pump and valve manufacturing companies in the world. Founded in 1871, it is an international company directly managed by the headquarters. There are six factories in Germany and France. The main products of KSB in Germany include: globe valves, filters, ball valves, gate valves, traps, butterfly valves and other general valves.

Danke Valve (United States), Danke Group is the world’s leading supplier of fluid control products and services. Products designed and manufactured are used in various industrial and general commercial applications. Since its establishment for nearly a century, more than 300 dedicated engineers have continuously developed high-quality valves and accessories to meet different market needs. All products are completed under a strict quality system that complies with the ISO9001 international standard. Danke products and distributors are located in 43 countries around the world. The main products are: ball valves, gate valves, check valves, butterfly valves, etc.
ARI Valve (Germany), ARI Valve was founded in 1952 and is headquartered in STUKENBROCK, Germany. ARI has three factories in Germany. The total output of valves is second to none in Germany. The products cover four series of globe valves-safety valves-control valves-traps. In the past 50 years, German iResearch Valve has been committed to providing comprehensive technology and perfect services for industrial processes, process, chemical, shipbuilding and building automation fields, which can meet the needs of system cutoff, safety, control and Hydrophobic function requirements.
SpiraxSarco Valves (UK), SpiraxSarco Valves SpiraxSarco, UK, is committed to promoting the effective application and control of steam and other industrial fluids on a global scale. It has a history of more than 100 years. The history of SpiraxSarco Valve Company can be traced back to 1888. It was established in the United Kingdom in 1937. In 1959, SpiraxSarco Valve Group Company was listed on the London stock market and has outstanding performance reports every year.
Dongguang Valve (Taiwan), In 1962, Dongguang Faner Industrial Co., Ltd. was reorganized and moved to Hami Street, Taipei, covering an area of approximately 1,650 square meters, and adding semi-automatic casting equipment. It has a history of 60 years. Later, due to business development needs, Shenzhen Dongguang Faner Valve Co., Ltd. was officially registered in the mainland in 2010.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D
URL: http://www.tanghaivalve.com
Name: Harry Li
Email: harry@tanghaivalve.com

Types and working principles of electric valves

September 18, 2020

The so-called electric valve, as its name implies, is to drive the opening and closing of the valve through the power

U type flange butterfly valve (6)

supply. It is mainly composed of two parts. The upper part is an electric actuator and the lower part is a valve. In industrial processes, it is used to control the travel and flow of various fluids, such as water, oil, chemical liquids, etc., based on parameters such as temperature, pressure and flow. Electric valve is a kind of self-control valve that has been widely used in recent years. With its stable reliability and multiple control functions, it can meet the requirements of most common valves that cannot be used. It has become an indispensable control device in the process pipeline.
Electric ball valve; Electric regulating valve; Electric butterfly valve;
The electric valve has a simple structure and a long service life. It is suitable for almost all media and can greatly reduce the labor intensity of the operator. It is suitable for equipment where it cannot be manually operated or is difficult to approach. It can complete remote operation of the valve, and the height of the equipment is not restricted.
Types and classifications of electric valves:

electric stainless steel gate valve

1. According to different actuators, electric valves are generally divided into two categories, one is angular stroke, the other is linear stroke, angular stroke electric valve controls 90 degree rotation to achieve the on and off of the valve, and linear stroke realizes the valve plate. The up and down actions are usually used in conjunction with equipment with a higher degree of automation.

2. According to the function, it can be divided into switch type and regulation type, intelligent type and explosion-proof type; the switch type is fully open and fully closed, and the regulation type can control any opening degree to achieve the function of adjusting the flow rate!

3. According to the valve position, it can be divided into common electric ball valves, electric butterfly valves, electric regulating valves, solenoid valves, electric gate valves, electric shut-off valves, etc., which can be applied to various occasions.

4. According to the shape of the valve body, it can be divided into ordinary electric valve and micro electric valve. The working principle of the electric valve: The electric valve is connected by the electric actuator and the valve. After installation and debugging, the valve is driven by the power supply to realize the opening and closing action of the valve, so as to achieve the purpose of switching or adjusting the pipeline medium. The opening degree of the electric valve can be controlled, and the state is open, closed, half-open and half-closed, which can control the flow of the medium in the pipeline, but the solenoid valve cannot meet this requirement.

Solenoid valve is a type of electric valve, which uses the magnetic field generated by the solenoid coil to pull the valve core, thereby changing the on and off of the valve body, the coil is de-energized, and the valve core retreats by the pressure of the spring.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Valve flow characteristic curve and classification

September 18, 2020

The flow characteristic of the valve is the relationship between the relative flow of the medium flowing through the regulating valve and its opening under the condition that the pressure difference between the two ends of the valve remains constant. Flow characteristic is an important technical index and parameter of regulating valve. It is very important to make the correct selection in the application process of the control valve.

Flow characteristics of regulating valve

Valve flow characteristics can be defined as: the relative flow of the controlled medium flowing through the valve, and the relationship between the relative opening (relative displacement) of the valve is called the flow characteristics of the regulating valve. Generally speaking, it is divided into four types: straight line, equal percentage (logarithm), parabola and quick opening! The specific description and advantages are as follows:

1. The linear characteristic refers to the linear relationship between the relative flow of the valve and the relative opening, that is, the time constant of the flow change caused by the change of unit opening. The relative stroke of the linear characteristic is linear with the relative flow. The flow change caused by the change of unit stroke is constant. When the flow is large, the relative value of the flow changes little, and when the flow is small, the relative value of the flow changes greatly.

2. the equal percentage characteristic (logarithm) means that the relative flow change caused by the change of the unit opening is proportional to the relative flow at that point, that is, the amplification factor of the regulating valve changes, and it increases with the increase of the relative flow. The relative stroke and relative flow of equal percentage characteristics are not in a linear relationship. The change in flow caused by the change of unit stroke at each point of the stroke is proportional to the flow at this point, and the percentage of flow change is equal. Therefore, its advantage is that when the flow rate is small, the flow rate changes small, and when the flow rate is large, the flow rate changes greatly, that is, it has the same adjustment accuracy at different opening degrees.

3. the parabolic characteristic means that the relative flow change caused by the change of the relative opening of the unit is proportional to the square root of the relative flow value at this point. The flow rate changes in proportion to the two sides of the stroke, and generally has an intermediate characteristic between linear and equal percentage characteristics.

4. the quick opening flow characteristic means that there is a larger flow when the opening is small. With the increase of the opening, the flow can reach the maximum quickly, and then the opening is increased, and the flow change is small, so it is called For quick opening characteristics.

The flow characteristic of the diaphragm valve is close to the quick opening characteristic, the flow characteristic of the butterfly valve is close to the equal percentage characteristic, the flow characteristic of the gate valve is the linear characteristic, the flow characteristic of the ball valve is linear in the middle opening and closing stage, and the equal percentage characteristic in the middle opening.

Globe valve (9)

Under normal circumstances, ball valves and butterfly valves are usually not used for adjustment. If they are used for adjustment, they are only used for adjustment when the opening is small. Generally, they can be classified as quick-opening, and they are really used for adjustment. Most of them are basically cut-off valves (globe valve). The valve head is processed into a parabolic cone, spherical shape, etc., and different curve characteristics are used. Generally speaking, as an adjustment, the basic percentage characteristic is used more.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

installation principle and setting of the bypass valve

September 17, 2020

Whether the valve needs to be installed with the principle and setting of the bypass valve.
We occasionally see relatively large valves in some pipelines and always install bypass valves. Why is this? What is its main function? Under what circumstances does it need to be installed? And what is the size of the bypass valve of the corresponding equipment?

bypass valve installation

In fact, by setting a bypass valve in the pipeline, its role can be divided into two major points in general: one is to protect (balance the pressure at both ends), and the other is to make emergency use!
First, the protective effect can also be said to be a protective measure for the main valve to prevent the large opening resistance caused by the excessive pressure difference between the front and rear of the valve and the difficult opening of the valve, especially in some large diameter or high pressure pipeline. Before the high-pressure pipeline is opened, the pressure is released through the bypass valve to avoid the sudden influx of high pressure and impact on the pipeline below the valve. Or the pressure difference between the two ends of the valve is too large, and the opening torque is too large. In order to avoid torsion damage to the valve, the valve should be opened after bypassing and releasing the pressure.

butterfly valve and bypass valve

Second, the emergency function, used as a backup pipeline, the biggest advantage is that when the main valve fails or needs maintenance, it can flow through the bypass valve without affecting normal production.
Whether the valve needs to be installed with the specific requirements and settings of the bypass valve: (for reference only)
2.5MPa level, above DN400; 4.0MPa level, above DN250; 6.4MPa level, above DN200; 10MPa level, above DN150; For valves from DN100 to DN200, the bypass pipe and bypass valve are DN20;
For valves from DN250 to DN600, the bypass pipe and valve are DN25; for valves above DN600, the bypass pipe and valve are DN40.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

The difference of cryogenic valve and ordinary temperature valve

September 17, 2020

Cryogenic valves, as the name implies, are valves that can work in cryogenic and cryogenic conditions. The operating temperature is demarcated. Valves with operating temperatures below -40°C are usually called cryogenic valves, which are mainly used for gas liquefaction, For separation, transportation and storage equipment, the operating temperature can reach below -270℃. Currently, there are butterfly valves, check valves, gate valves, globe valves, ball valves, and throttle valves.

In recent years, ultra-low temperature valves have been used more and more widely, and they are one of the

lug type butterfly valve, ductile iron, center lined,

indispensable important equipment in petrochemical, air separation, natural gas and other industries. The working medium is not only low in temperature, but most of them are toxic, or flammable and explosive. , And strong permeability, so it determines many special requirements for valve materials and design. It is not only required to work normally at the set temperature, but also to ensure the working performance at room temperature.

Compared with the normal temperature valve, the low temperature valve has a higher packing part and uses an extended stem. Its purpose is to reduce the heat transferred from the outside into the device; to ensure that the temperature of the stuffing box is above 0℃, so that the stuffing can work normally; to prevent the valve stem and the upper part of the valve cover at the stuffing box part from being too cold The parts are frosted or frozen.

The design of the long-neck bonnet is mainly the design of the neck length L. L refers to the distance from the bottom of the stuffing box to the upper surface of the upper sealing seat. It is related to the thermal conductivity of the material, the thermal conductivity area, the surface heat dissipation coefficient, and the heat dissipation area. , The calculation is relatively cumbersome, and it is generally obtained by experimental methods.

Ferritic stainless steel can be used when the temperature is higher than -100℃, austenitic stainless steel can be used when the temperature is lower than -100℃, copper alloy or aluminum alloy can be used for low pressure and small diameter valves, and the valve body should be able to withstand temperature changes sufficiently. The expansion and contraction, and the structure of the valve seat part will not be permanently deformed due to temperature changes.

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