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Resilient seated socket end gate valve

November 18, 2020

GATE VALVE-resilient seated SOCKET END
Standard: EN1074; EN1171

Socket ended resilient seated wedge gate valve-ductile iron (1)

CAST IRON / DUCTILE IRON GATE VALVE SOCKET END
NON RISING STEM
Pressure: PN10 / PN16
Connection ends: Socked ends, for PVC pipes, uPVC pipes
FACE TO FACE: ACCORDING TO BS, DIN, ANSI, AWWA, SABS STANDARD ETC.
BODY:CAST IRON/DUCTILE IRON
BONNET:CAST IRON/DUCTILE IRON
WEDGE:CAST IRON/DUCTILE IRON, fully vulcanized with EPDM rubber
STEM: SS/BRASS
Coating: fusion bonded expoxy coating

The opening and closing part of the socket gate valve is a gate. The movement direction of the gate is perpendicular to the direction of the fluid. The gate valve can only be fully opened and fully closed, and cannot be adjusted or throttled. The gate has two sealing surfaces. The two sealing surfaces of the most commonly used mode gate valve form a wedge. The wedge angle varies with valve parameters, usually 50, and 2°52′ when the medium temperature is not high. The gate of the wedge gate valve can be made into a whole, called a rigid gate; it can also be made into a gate that can produce slight deformation to improve its manufacturability and compensate for the deviation of the sealing surface angle during the processing. The plate is called an elastic gate.

Socket gate valve can be divided into wedge gate valve and parallel gate valve according to the sealing surface configuration. The wedge gate valve can be divided into: single gate, double gate and elastic gate; parallel gate valve can be divided into It is single gate type and double gate type. According to the thread position of the valve stem, it can be divided into two types: rising stem gate valve and non-rising stem gate valve.

When the socket gate valve is closed, the sealing surface can only rely on the medium pressure to seal, that is, rely on the medium pressure to press the sealing surface of the gate against the valve seat on the other side to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves use forced sealing, that is, when the valve is closed, the gate must be forced against the seat by external force to ensure the sealing performance of the sealing surface.

The gate of the socket gate valve moves linearly with the valve stem, which is called rising stem gate valve (also called rising stem gate valve). Usually there is a trapezoidal thread on the lifting rod, through the nut on the top of the valve and the guide groove on the valve body, the rotary motion is changed into linear motion, that is, the operating torque is changed into operating thrust.

When the valve is opened, when the lifting height of the gate is equal to 1:1 times the valve diameter, the fluid passage is completely unblocked, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as a mark, that is, the position where it cannot be opened, as its fully open position. In order to take into account the locking phenomenon of the temperature change, it is usually at the top position of the opening, and then rewind 1/2-1 turn as the position of the fully open valve. Therefore, the fully open position of the valve is determined by the position of the gate (that is, the stroke).

Socket ended resilient seated wedge gate valve-ductile iron (2)

In some gate valves, the stem nut is set on the gate, and the rotation of the handwheel drives the rotation of the valve stem to lift the gate. This kind of valve is called a rotating stem gate valve or a dark stem gate valve.

advantage:
The fluid resistance is small, and the sealing surface is less brushed and corroded by the medium.
It is easier to open and close.
The flow direction of the medium is not restricted, does not disturb the flow, and does not reduce the pressure.
The shape is simple, the length of the structure is short, the manufacturing process is good, and the scope of application is wide.

Disadvantages:
It is easy to cause erosion and scratches between the sealing surfaces, which makes maintenance difficult.
The overall size is large, opening requires a certain amount of space, and the opening and closing time is long.
The structure is more complicated.

The types of socket gate valves can be divided into wedge gate valves and parallel gate valves according to the sealing surface configuration. Wedge gate valves can be divided into: single gate type, double gate type and elastic gate type; parallel gate type Gate valves can be divided into single gate type and double gate type. Divided according to the thread position of the valve stem, it can be divided into two types: open stem gate valve and dark stem gate valve.

Matters needing attention in installation and maintenance
Handwheels, handles and transmission mechanisms are not allowed to be used for lifting, and collisions are strictly prohibited.
The double gate valve should be installed vertically (that is, the valve stem is in the vertical position and the handwheel is at the top).
The gate valve with bypass valve should be opened before opening (to balance the pressure difference between inlet and outlet and reduce the opening force).
The gate valve with transmission mechanism should be installed according to the product manual.
If the valve is frequently opened and closed, lubricate at least once a month.

Structural features:
The general gate valves used on the market for a long time generally have water leakage or rust. The company introduces the elastic seat seal gate valve produced by European high-tech rubber and valve manufacturing technology, which overcomes the defects of poor sealing and rust of general gate valves. The sealing gate valve uses the compensation effect of the elastic gate plate to produce a small amount of elastic deformation to achieve a good sealing effect. The valve has the obvious advantages of light switch, reliable sealing, good elastic memory and service life. It can be widely used as a regulating and intercepting device on the pipelines of tap water, sewage, construction, petroleum, chemical industry, food, medicine, textile, electric power, shipbuilding, metallurgy, energy system, etc.

Types and classifications of gate valves

November 13, 2020

Gate valve, also called plate gate valve, is mainly composed of valve body, bonnet, disc, valve stem, valve seat and sealing packing. It is one of the most common valve types in isolation valves. The main purpose of the gate valve is to cut off the fluid. For this reason, it is usually called a “cut off” valve or a “blocking” valve. The gate valve has many different structural forms, and the sealing element structure used in it is different. According to the structure of the sealing element, it can be divided into several different types.

ductile iron soft seal gate valve-non rising stem

Classified by valve stem:
According to the stem type, it can be divided into rising-stem gate valve and non rising-stem gate valve. The valve stem is the operating part of the gate valve, and its function is to transmit the opening and closing force to the opening and closing parts.
1. The trapezoidal thread of the rising-stem gate valve is placed outside the valve body and located on the upper part of the valve stem. By rotating the valve stem nut, the valve stem drives the disc to rise and fall synchronously to realize the opening and closing of the valve, so it is easy to identify the valve The opening and closing state of the machine can avoid misoperation. Since the stem nut is outside the body cavity, it is beneficial to lubrication, and the opening and closing state is intuitive and obvious, so it is widely used. However, in harsh environments, the exposed threads of the valve stem are vulnerable to damage and corrosion, even affecting operation. Its disadvantage is that the height of the valve after opening is large, usually a stroke is added to the original height of the valve, which requires a lot of operating space.

rising stem gate valve-OS&Y (3)

2. Non rising-stem gate valve is also called rotating stem gate valve (also called non rising-stem wedge gate valve). The stem nut is placed inside the valve body and is in direct contact with the medium and is often fixed on the disc. Through the rotation of the valve stem, the valve stem nut drives the disc to move up and down to complete the opening and closing. Usually there is a trapezoidal thread at the bottom end of the valve stem. Through the thread at the bottom end of the valve and the guide groove on the valve disc, the rotary motion is changed into linear motion, that is, the operating torque is turned into operating thrust. Since the trapezoidal thread for transmission is located inside the valve body, it is easily corroded by the medium and cannot be lubricated. The opening degree cannot be directly observed, and an indicating device is required. However, its valve stem does not move up and down, and requires small operating space, so it is suitable for occasions with limited locations and dense pipelines.

Classified by structure:
According to the structure type, it can be divided into two types: wedge gate valve and parallel gate valve. That is, the disc is a wedge type is called a wedge gate valve, and the disc is a parallel type is a flat gate valve.
1. The flat gate valve means that the sealing surface is parallel to the vertical centerline, so the sealing surfaces on the valve body and the disc are also parallel to each other. The most common type of this kind of gate valve is the double disc type. In order to make the valve body and the two sealing surfaces of the disc tightly contacted when it is closed, a double-sided thrust wedge is often used between the two discs. It is mostly used in low pressure pipelines such as small pipelines. Parallel gate valves using a single disc are also available but rare.
2. Wedge gate valve means that the sealing surface is at a certain angle with the vertical center line, that is, the two sealing surfaces are wedge-shaped gate valves. The disc of wedge gate valve is single and double. The advantage of the double disc type is that the accuracy of the sealing angle is lower, the temperature change is not easy to make the disc wedged, and the sealing surface wear can be compensated with gaskets. The disadvantage is that the structure is complex, and it is easy to stick in dry media, and the main reason is that the disc is easy to fall off after the upper and lower baffles are rusted for many years.

non-rising stem gate valve-open and close position

rising stem gate valve-open and closed position

Classification by other methods:
According to different standards: national standard gate valve, American standard gate valve, German standard gate valve, Japanese standard gate valve
According to the connection method: flange gate valve, welded gate valve, threaded gate valve (divided into internal thread and external thread)
According to pressure level: high pressure gate valve, low (medium) pressure gate valve
According to the driving mode: electric gate valve, pneumatic gate valve, manual gate valve
Classified by material: stainless steel gate valve, forged steel gate valve, cast steel gate valve, carbon steel gate valve, cast iron gate valve, copper gate valve (also divided into bronze gate valve, brass gate valve), ceramic gate valve, plastic gate valve

The main difference:
1. The lifting screw of the concealed rod flange gate valve only rotates and moves up and down. Only a rod is exposed. The screw cap is fixed on the disc. The disc is raised by the rotation of the screw, and there is no visible electric gate valve frame. ; The lifting screw of the rising stem flange gate valve is exposed, and the screw cap is close to the hand wheel and is fixed (not high-pressure gate valve rotation nor axial movement), the disc is improved by rotating the screw, the screw and the disc have only relative rotational movement There is no relative axial displacement, and the appearance is a gate-shaped bracket.
2. The valve stem with dark stem cannot be seen, while the stem with open stem can be seen.
3. The steering wheel and the valve stem are connected and relatively immovable when the dark stem valve is opened and closed. The valve stem rotates at a fixed point to help the valve clack move upward and downward to complete the opening and closing. The rising stem valve is driven by the turnbuckle of the valve stem and the steering wheel to raise or lower the disc.
To put it simply, the rising stem valve is that the disc and the stem move up and down together, and the steering wheel is always at a fixed point.
Is rising-stem gate valve or non rising-stem gate valve used outdoors?
For the valves installed in the outdoor valve wells, according to the experience of Tanghai valves, it is recommended that you use dark stem valves. The use of rising stem valves has the following disadvantages: 1. When the valve is opened and closed, the valve stem has to rise and fall, which takes up a lot of space. If the pipeline is not buried very deep, the valve well will hinder the opening of the valve. When the valve is opened, the valve well cover will not be closed or the valve cannot be fully opened. 2. After the number of switches is increased, the contact surface of the valve stem and the pressure flange will leak more seriously, and the packing should be replaced frequently. 3. If you don’t switch frequently, a part of the valve stem will be exposed to the valve body for a long time. In the humid environment of the valve well, the exposed valve stem is very easy to oxidize and rust. Once it needs to be closed, it will not be closed. Otherwise, grease must be applied frequently. In short, the maintenance workload is large. Dark stem valves do not have these problems, the probability of water leakage is also small, and of course the maintenance workload is also small. for reference only.

The opening and closing part of the rising-stem gate valve (gate valve) is a disc, and the movement direction of the disc is perpendicular to the direction of the fluid. The rising-stem gate valve can only be fully opened and fully closed, and cannot be adjusted or throttled.

Disc has two sealing surfaces. The two sealing surfaces of the most commonly used mode disc valve form a wedge. The wedge angle varies with valve parameters, usually 50, and 2°52′ when the medium temperature is not high. The disc of the wedge gate valve can be made into a whole, called a rigid disc; it can also be made into a disc that can produce slight deformation to improve its manufacturability and make up for the deviation of the sealing surface angle during the processing. This disc is called an elastic disc .

The types of rising-stem gate valve can be divided into wedge disc gate valve and parallel disc gate valve according to the sealing surface configuration. Wedge disc gate valve can be divided into: single disc type, double disc type and elastic disc type; parallel disc Type gate valve can be divided into single disc type and double disc type. According to the thread position of the valve stem, it can be divided into rising-stem gate valve and non rising-stem gate valve.

When the rising-stem gate valve is closed, the sealing surface can only rely on the medium pressure to seal, that is, only rely on the medium pressure to press the sealing surface of the disc to the valve seat on the other side to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves adopt forced sealing, that is, when the valve is closed, the disc must be forced to the valve seat by external force to ensure the tightness of the sealing surface.
The working principle of rising-stem gate valve
Rotate the hand wheel, through the advance and retreat of the thread of the hand wheel and the valve stem, raise or lower the valve plate connected with the valve stem to open and close
The rising-stem gate valve has the following advantages:
The fluid resistance is small, and the sealing surface is less eroded and eroded by the medium.
It is easier to open and close.
The flow direction of the medium is not restricted, does not disturb the flow, and does not reduce the pressure.
The shape is simple, the length of the structure is short, the manufacturing process is good, and the scope of application is wide.
The disadvantages of rising-stem gate valve are as follows:
It is easy to cause erosion and scratches between the sealing surfaces, and maintenance is difficult.
The overall size is large, opening requires a certain amount of space, and the opening and closing time is long.
The structure is more complicated.
The types of gate valves can be divided into wedge disc gate valves and parallel disc gate valves according to the sealing surface configuration. Wedge disc gate valves can be further divided into: single gate, double disc and elastic disc; parallel disc gate valves can be Divided into single disc type and double disc type. According to the thread position of the valve stem, it can be divided into rising-stem gate valve and non rising-stem gate valve.
Installation and maintenance of rising-stem gate valve:
Handwheels, handles and transmission mechanisms are not allowed to be used for lifting, and collisions are strictly prohibited.
The double disc gate valve should be installed vertically (that is, the valve stem is in the vertical position and the handwheel is at the top).
The gate valve with a bypass valve should be opened before opening (to balance the pressure difference between the inlet and outlet and reduce the opening force).
The gate valve with transmission mechanism should be installed according to the product manual.
If the valve is frequently opened and closed, lubricate at least once a month.

Structural characteristics of rising-stem gate valve:
The general gate valves used on the market for a long time generally have water leakage or rust. The company introduces the elastic seat seal gate valve produced by European high-tech rubber and valve manufacturing technology, which overcomes the defects of poor sealing and rust of general gate valves. The sealing gate valve uses the compensation effect of the elastic disc to produce a small amount of elastic deformation to achieve a good sealing effect. The valve has the obvious advantages of light switch, reliable sealing, good elastic memory and service life. It can be widely used as a regulating and intercepting device on the pipelines of tap water, sewage, construction, petroleum, chemical industry, food, medicine, textile, electric power, shipbuilding, metallurgy, energy system, etc.

Features of rising-stem gate valve:
Light weight: The body is made of high-grade ductile iron, which is about 20% to 30% lighter than the traditional gate valve, and is easy to install and maintain.

Flat-bottomed gate seat: The traditional gate valve often deposits in the groove at the bottom of the valve due to foreign objects such as stones, wood, cement, iron filings, and other debris after the pipe is washed with water. The bottom of the elastic seat-sealed gate valve adopts the same flat-bottom design as the water pipe machine, which is not easy to cause debris siltation and makes the fluid flow unimpeded.

Integral encapsulation: The disc adopts high-quality rubber for the overall inner and outer rubber. European first-class rubber vulcanization technology enables the vulcanized disc to ensure accurate geometric dimensions, and the rubber and ductile disc are connected firmly, not easy to fall off, and have good elastic memory . water

Precision casting valve body: The valve body adopts precision casting, and the precise geometric dimensions make the inside of the valve body without any finishing to ensure the sealing of the valve.
Features of dark-rod soft-seal gate valve:
The overall valve encapsulation is used to produce a deformation compensation effect to achieve a good sealing effect, overcome the poor sealing, water leakage and rust of the general gate valve, and save installation space more effectively. It can be widely used in tap water, sewage, construction, petroleum, chemical, It is used as a regulating and intercepting device on fluid pipelines such as food, medicine, textile, electric power, shipbuilding, metallurgy, energy systems. Our factory introduces European high-tech valve manufacturing technology to produce elastic seat-sealed gate valves, which are deformed by the overall encapsulation of the gate. The compensation effect achieves a good sealing effect and overcomes the phenomenon of poor sealing, water leakage and rust of general gate valves. It can be widely used as a regulating and intercepting device on fluid pipelines such as tap water, sewage, construction, petroleum, chemical industry, food, medicine, minor injuries, electric power, ships, metallurgy, and energy systems.
1. The gate adopts integral rubber encapsulation, and its good covering performance and precise geometric dimensions ensure reliable sealing and longevity.
2. Light weight: The valve body is made of ductile iron, which is light in weight and easy to install.
3. Flat-bottomed valve seat: The bottom is designed with the same flat-bottomed valve seat as the water pipe, which does not produce debris and makes the seal more reliable.
4. Corrosion resistance: The inner cavity is coated with non-toxic epoxy resin to prevent corrosion and rust. Not only can it be used for raw drinking, but also can be used in sewage systems.
5. Three “0” seal: The valve stem is sealed with three O-rings, with low friction resistance, light switch and no water leakage.
How to select the non rising-stem gate valve and rising-stem gate valve?
For oil and natural gas pipelines, single disc or double disc gate valves are used. If you need to clean the pipeline, use a single disc or double disc rising-stem gate valve with diversion holes.
For the transportation pipeline and storage equipment of refined oil, select single disc or double disc gate valve without diversion hole.
For oil and natural gas mining wellhead devices, single disc or double disc gate valves with dark rod floating valve seats and diversion holes are selected, most of which are API16A standards, and the pressure levels are API2000, API3000, API5000, API10000, API15000, API20000.
For pipelines with suspended particulate media, use knife-shaped plate gate valves.
The city gas transmission pipeline adopts single disc or double disc soft-sealed rising-stem gate valve.
For urban tap water projects, single disc or double disc rising-stem gate valve without diversion hole is used.

Valve material comparison table-valve pressure-temperature

October 27, 2020

The relationship between valve temperature and pressure:
The valve operating temperature and pressure have a certain internal connection and influence each other. Among them, temperature is the dominant factor affecting the valve. A valve with a certain pressure is only suitable for a

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

certain temperature range, and changes in valve temperature can affect the valve’s operating pressure. E.g:
The nominal pressure of a carbon steel valve is 10MPa. When the medium working temperature is 200℃, its maximum working pressure P20 is 10MPa; when the medium working temperature is 400℃, its maximum working pressure P40 is 5.4MPa; when the medium works When the temperature is 450℃, the maximum working pressure P20 is 4.5MPa.

Valve material temperature and pressure comparison table:
Valve material and applicable pressure, temperature and grade
Gray cast iron is suitable for water, steam, air, gas, oil and other media with nominal pressure PN≤1.0MPa and temperature -10℃～200℃. Commonly used grades are: HT200, HT250, HT300, HT350.
Malleable cast iron Suitable for water, steam, air and oil media with nominal pressure PN≤2.5MPa and temperature -30～300℃. Commonly used grades are: KTH300-06, KTH330-08, KTH350-10.
Nodular cast iron is suitable for water, steam, air and oil with PN≤4.0MPa and temperature of -30～350℃. Commonly used grades are: QT400-15, QT450-10, QT500-7. At present, the level of domestic technology varies among factories, and it is often difficult for users to inspect. It is recommended that PN≤2.5MPa, and steel valves are used for safety.
Acid-resistant high-silica ductile iron Suitable for nominal pressure PN≤0.25MPa, suitable for corrosive media with temperature lower than 120℃.
Carbon steel is suitable for water, steam, air, hydrogen, ammonia, nitrogen and petroleum products with a nominal pressure of PN≤32.0MPa and a temperature of -30～425℃. Commonly used grades are WC1, WCB, ZG25, high-quality steel 20, 25, 30 and low-alloy structural steel 16Mn.
Copper alloy is suitable for water, sea water, oxygen, air, oil and other media with PN≤2.5MPa and steam media with temperature of -40～250℃. Commonly used grades are ZGnSn10Zn2 (tin bronze), H62, Hpb59-1 (brass) , QAZ19-2, QA19-4 (aluminum bronze).
High-temperature copper is suitable for steam and petroleum products with nominal pressure PN≤17.0MPA and temperature≤570℃. The specific selection must be in accordance with the valve pressure and temperature specifications. Commonly used grades are ZGCr5Mo, 1Cr5M0.ZG20CrMoV, ZG15Gr1Mo1V, 12CrMoV, WC6, WC9, etc.
Low-temperature steel is suitable for media with nominal pressure PN≤6.4Mpa and temperature≥-196℃ ethylene, propylene, liquid natural gas, liquid nitrogen, etc. Commonly used grades are ZG1Cr18Ni9, 0Cr18Ni9, 1Cr18Ni9Ti, ZG0Cr18Ni9
Stainless and acid-resistant steel Suitable for media such as nitric acid and acetic acid with nominal pressure PN≤6.4Mpa and temperature≤200℃. Commonly used grades are ZG0Cr18Ni9Ti, ZG0Cr18Ni10<nitric acid>, ZG0Cr18Ni12Mo2Ti, ZG1Cr18Ni12Mo2Ti<acid and urea>

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 seal (ring) material usage range comparison table

October 27, 2020

The selection of valve sealing material is determined according to the operating conditions of the valve, such as: pipeline medium, temperature range (high and low temperature), pressure and internal structure of the valve. For

soft sealing marine valve, rubber sealing, valve seat parts

different occasions, the selected seals are also different. Valve seals can generally be divided into two categories: soft seals and hard seals. Users should have a detailed understanding of their codes, operating temperature, pressure, medium and other parameters.

Comparison table of valve sealing material usage range:
Valve sealing material and valve sealing material use range:
Rubber (X) Nominal pressure PN ≤ 1 MPa, operating temperature t ≤ 150℃, applicable valves: globe valves, diaphragm valves, butterfly valves, check valves, etc.
Nylon (N) Nominal pressure PN ≤ 32 MPa, operating temperature t ≤ 90°C, applicable valves: globe valves, ball valves, etc.
PTFE (F) Nominal pressure PN ≤ 6.4 MPa, operating temperature t ≤ 180°C, applicable valves: globe valves, ball valves, gate valves, diaphragm valves, butterfly valves, check valves, etc.
Bus alloy (B) Nominal pressure PN ≤ 2.5 MPa, operating temperature t ≤ 150°C, applicable valves: stop valves for ammonia, etc.
Ceramic (G) Nominal pressure PN ≤ 1.6 MPa, operating temperature t ≤ 150°C, applicable valves: ball valves, plug valves, etc.
Enamel (C) Nominal pressure PN ≤ 1.0 MPa, operating temperature t ≤ 80°C, applicable valves: globe valve, diaphragm valve, check valve, discharge valve, etc.
Copper alloy (T) Nominal pressure PN ≤ 1.6 MPa, operating temperature t ≤ 200℃, applicable valves: gate valve, globe valve, check valve, plug valve, etc.
Stainless steel (H) Nominal pressure PN ≤ 32 MPa, operating temperature t ≤ 450°C, applicable valves: globe valves, ball valves (medium and high pressure valves), etc.
Nitrided steel (D) Nominal pressure PN ≤ 10 MPa, operating temperature t ≤ 540℃, applicable valves: power station gate valves, only for general use
Cemented carbide (Y) Nominal pressure (PN) and operating temperature (t) are determined according to the material of the valve body. Applicable valves: high pressure, ultra high pressure valves, high temperature and low temperature valves

What is the positive transmission of gears

October 23, 2020

When the total displacement coefficient of a pair of gears is greater than 0, it is a positive transmission.
Positive transmission refers to the positive displacement design of the gear. If two gears meshing with each other are in positive displacement, their center distance is greater than (the pair of gears) standard center distance. Conversely, if both gears use negative displacement, the center distance is smaller than the standard center distance. To judge whether the position is shifted, it is mainly to compare the measured gear parameters (including center distance) with the standard parameters of the gear to draw a conclusion.
Gear transmission is the most widely used transmission form in mechanical transmission. It has relatively

accurate transmission, high efficiency, compact structure, reliable work and long life. At present, the achievable indexes of gear technology: peripheral speed v=300m/s, rotation speed n=105r/min, transmitted power P=105KW, modulus m=0.004~100mm, diameter d=1mm~152.3mm
Features
1, the instantaneous transmission ratio is constant. The instantaneous transmission ratio of non-circular gear transmission can be designed according to the required change law.
2, the transmission ratio range is large, which can be used to decelerate or increase speed.
3, the range of speed (pitch circle speed) and transmission power is wide, and it can be used for high-speed (v>40m/s), medium-speed and low-speed (v<25m/s) transmission; power is from less than 1W to 105KW.
4, high transmission efficiency. A pair of high-precision involute cylindrical gears has an efficiency of over 99%.
5, compact structure, suitable for short-distance transmission.
6, the manufacturing cost is higher. Certain gears with special tooth shapes or high precision require special or high-precision machine tools, cutting tools and measuring instruments, so the manufacturing process is complicated and the cost is high.
7, low-precision gears, noise, vibration and shock during transmission, pollute the environment.
8, no overload protection
According to the relative position of the two shafts and the direction of the gear teeth, it can be divided into the following types:
<1>Straight tooth cylindrical gear drive;
<2> Helical cylindrical gear drive
<3> herringbone gear transmission;
<4> bevel gear transmission;

bevel gear

<5> cross-axis helical gear transmission.
According to the working conditions of the gear, it can be divided into:
<1>; Open gear transmission type gear transmission, the gears are exposed, and good lubrication cannot be guaranteed.
<2>; half-open gear transmission, the gear is immersed in the oil pool, with a protective cover, but not closed.
<3>; closed gear transmission, gears, shafts and bearings are all installed in a closed box, with good lubrication conditions, difficult for dust and sand to enter, accurate installation,
Gear transmission has good working conditions and is the most widely used gear transmission.
Gear transmission can be classified according to the relative position of its axis.
Gear drive can be divided into cylindrical gear drive, bevel gear drive, non-circular gear drive, rack drive and worm drive according to the shape of the gear.
According to the tooth profile curve, it can be divided into involute gear transmission, cycloid gear transmission and arc gear transmission. A transmission composed of more than two gears is called a gear train. The gear transmission can be divided into ordinary gear transmission and planetary gear transmission according to whether there are gears with axis movement in the gear train. The gears with axis movement in the gear train are called planetary gears. Gear transmission can be divided into closed type according to its working conditions
Gear transmission calculation
Open and semi-open transmission. Sealing the transmission in a rigid case and ensuring good lubrication is called closed transmission, which is more commonly used, especially for higher-speed gear transmissions, which must be closed transmission. Open transmission is exposed and cannot guarantee good lubrication. It is only used for low speed or unimportant transmission. Half-open transmission is somewhere in between.
The law of meshing: 　The smoothness of gear transmission requires the instantaneous transmission ratio in the process of gear tooth meshing i=angular speed of driving wheel/angular speed of driven wheel=ω1/ω2=constant, this requirement is guaranteed by tooth profile. Figure 2 shows that the two meshing tooth profiles E1 and E2 are in contact at any point K, and the common normal line N1N2 of the two tooth profiles is made through the point K, which intersects the connecting center line O1O2 at point C. The condition for maintaining contact during the meshing process of the two tooth profiles is that the velocity of the K point on the tooth profile E1, vK1, and the K point velocity on the tooth profile E2, vK2, are equal in the direction of the common normal line N1N2, that is, vKn1=vKn2=vKn. Make perpendicular lines from O1 and O2 to the N1N2 line and intersect at points N1 and N2. The above formula shows that the two-wheel tooth profile must meet the following conditions: “No matter where the two-wheel tooth profile is in contact at any position, the common normal line passing through the contact point must pass the fixed point C ─ ─ node on the connecting center line.” This is a circular gear. The basic law of tooth profile meshing. There are many curves that can meet this law. In fact, the requirements of manufacturing, installation and load-bearing capacity should be considered. Generally, only involute, cycloid and arc are used as the working tooth profile of the gear. Part of the tooth profile is involute.
For involute gears, the base radius rb1 and rb2 of wheel 1 and wheel 2 are respectively. The N1N2 line is the internal common tangent of the two base circles, that is, the common normal of any contact point of the two tooth profiles coincides with it. Because the two base circles have only one internal common tangent in one direction, the common normal of any contact point passes through the fixed point C, which shows that using an involute as the tooth profile conforms to the basic law of tooth profile meshing.
The two circles drawn through node C with O1 and O2 as the centers are called pitch circles. The pitch radius of wheel 1 and the pitch radius of wheel 2 Involute gears have the following characteristics: ①N1N2 is the trajectory of the contact points of the two tooth profiles, called the meshing line, which is a straight line. ②The common tangent line tt of the two pitch circles of gear transmission through node C is called the meshing angle α’between it and the meshing line N1N2, which is a constant. ③The pressure between the tooth surfaces is always along the direction of the common normal line N1N2 of the contact point, so the pressure direction between the tooth surfaces does not change when the involute gear transmits power. ④The transmission ratio is inversely proportional to the radius of the base circle of the two wheels. After the gear is made, the base circle is determined. Therefore, even if the center distance is slightly deviated from the design during operation, the transmission ratio will not be affected. This feature is called the separability of the transmission. It affects the processing, assembly and Maintenance is very beneficial. ⑤The two tooth profiles only have no sliding between the tooth surfaces when the node C is in contact, and there is sliding between the tooth surfaces when they are in contact at other points, and the farther away from the node, the greater the sliding. ⑥Since the involute gear can mesh with a rack with a linear tooth profile, it can be processed by a tool with a linear tooth profile. The tool is easy to manufacture and the machining accuracy can be high.
Coincidence degree: Coincidence degree is an important parameter that affects the continuous transmission of gears. As shown in Figure 2, gear tooth meshing starts from the contact between the tooth root of the driving wheel and the tooth tip of the driven wheel, that is, the intersection A of the tooth tip circle of the driven wheel and the meshing line is the starting point of meshing. As the wheel 1 rotates, the wheel 2 is pushed to rotate, and the contact point moves along the meshing line. When the contact point moves to the intersection E of the addendum circle of the wheel 1 and the meshing line (the dotted line in the figure), the tooth profile When the meshing ends, the two tooth profiles begin to separate. Point E is the meshing end point, which is the actual meshing line length. If the front pair of teeth are still in contact at point D before point E, and the latter pair of teeth are in contact at point A, then the transmission is continuous; if the front pair of teeth has left at point E, and the latter pair has not yet entered meshing , Then the transmission is interrupted. Considering the influence of gear manufacturing, installation errors and deformation, ε≥1.1～1.4 is often required in practice. The greater the coincidence degree, the more stable the transmission. The above refers to the coincidence degree of the end face of the cylindrical gear, and there is a longitudinal coincidence degree for the helical cylindrical gear.
The condition for a pair of gears to be able to mesh correctly is that they must have equal modulus and equal pressure angle.

Accuracy requirements of Equipment installation

October 23, 2020

1. For static equipment
The vertical deviation of vertical equipment should not be greater than L/1000 and not greater than 10mm. Unless the drawings have special requirements.

lug type butterfly valve, ductile iron, center lined,

The horizontal deviation of horizontal equipment should not be greater than L/1000 in the axial direction and 2D/1000 in the radial direction.

2. For moving equipment
When the pump is aligned, the selection of the installation datum and the allowable deviation of the level must meet the requirements of the “special specification” or the pump technical file. Generally, the allowable deviation of horizontal horizontality is 0.10mm/m, and the allowable deviation of vertical horizontality of the installation datum part is 0.05mm/m. The leveling and alignment values must not be adjusted by loosening the anchor bolts.
1. The pump that is disassembled and installed is based on the processing surface of the pump body, and the allowable deviation of the horizontality of the pump in the vertical and horizontal directions is 0.05mm/m.
2. The integrally installed pump should be leveled based on the inlet and outlet flange surface or other horizontal processing datum plane. The allowable deviation of horizontality is 0.05mm/m in the longitudinal direction and 0.10mm/m in the transverse direction.
3. When the driving shaft and the driven shaft are connected by a coupling, the centering deviation of the two shafts and the gap between the end faces of the two shafts should be:
Centering deviation: the radial displacement is not more than 0.03mm.
The axial tilt should not be greater than 0.05/1000.
The end face gap is 1.00~3.5mm.

What is assembly error and how to control it?

October 23, 2020

Assembly error refers to the difference between the installation position of the parts and the ideal position required by the assembly specifications and design regulations and processes.

Causes of assembly errors:

Double flange butterfly valve (1)

①Part error: the additional error caused by the manufacturing error of the part and the deformation and wear after operation and use.
② Errors in tools and measuring tools: tools and quantities have manufacturing errors, and system errors will occur if they are used for measurement and positioning.
③Operation error: due to hand feeling (such as tightness, flatness, sharpness, smoothness, beating, shaking, vibration, spacing, pulling force, hand tapping, hand-hand gap, hand feeling loose, etc.), visual inspection (size, level, straight , Vertical, parallel, aligned, tangent, etc.), ear hearing (various abnormal noises), nose smell (leakage, etc.), the error generated by the human sensory identification.
④Environmental errors: errors caused by temperature, relative humidity, light direction, air flow direction, movement of the foundation, etc.
⑤ Consciousness error: error caused by lack of concentration or lack of responsibility.
How to control assembly error:
1. Choose a reasonable assembly benchmark
In order to make the assembly position of the part accurate, select a certain part (point, line, surface) of the already positioned part as the positioning basis for the part to be installed. This part is called the assembly datum. The correct choice of assembly benchmark is an important factor in improving assembly accuracy and reducing assembly errors, and must be taken seriously. The following factors should generally be considered for the correct selection of the assembly datum.
(1) Try to choose parts with higher machining accuracy, that is, parts with small dimensional tolerance, high shape accuracy, small position deviation, and low roughness as the reference. For example, the diameter tolerance and radial runout of the groove part during the manufacturing of the roller are lower than those of the smooth surface. Therefore, when checking the roller bending and correcting the roller gauge, the groove part is the reference.
(2) The reference position should be as close as possible to the assembly adjustment point. For example, when the car surface is flat, the height of the car surface should be adjusted by the frame lifting screw, so the flat ruler should be placed as close to the frame as possible. For example, if the flat-foot iron rest is placed far away from the frame, and the reference point is far away from the frame, when the height of the adjacent frame is adjusted, the iron rest will be driven to rise and fall to make the reference drift. As shown in Figure 1, suppose the center distance ab of the two frames is 1008mm, point a is the point where the top surface of the car has been leveled, and point b is the point where the top surface of the car is to be leveled. The flat ruler should be placed at point a. If it is not placed at point a, it should be placed at point d, 100mm (ad) away from point a. When correcting the length of the car to be horizontal, the car surface at the adjustment point is from point b Adjusted to point c, increased by 0.10mm (bc), this flat ruler bar was also driven to rise from point d to point e, rising by 0.01mm (de), that is, the benchmark is raised by 0.01mm.
This shows that the farther the flat-foot rail is from the frame, the greater the change in the height of the reference plane, which affects the assembly accuracy.
(3) Try to reuse the same datum as much as possible to eliminate the deviation of the part surface shape. For example, because the top surface has a certain degree of lengthwise bending and widthwise distortion, it is necessary to look at the length of the car surface to the level of the flat ruler, the level to look at the width of the car surface and the level of the front roller to support the height line. Line round rollers are placed in the same position to avoid additional errors caused by uneven top surface of the car.
(4) When selecting the benchmark, the convenience of flat mounting operation should also be considered. For example, there are generally two methods for positioning the helical gear of the spindle shaft: one is to insert the spindle, and use the spindle as the reference, and use the card board to locate; the other is to not insert the spindle, and the lower dragon-jin oil cup is the reference. Although the tolerance of the spindle diameter is smaller than the tolerance of the oil cup hole, it is more difficult to locate after inserting the spindle. Taking the oil cup hole as the reference, it can meet the left and right positioning requirements of the spindle gear, and the spindle can not be inserted, which makes the operation convenient.
(5) Try to be consistent with the reference parts of the machine manufacturer’s parts processing and pre-assembly.
2. Avoid multiple transmissions of assembly standards (reduce cumulative errors)
There are two ways to divide a 1m long straight line into ten equal parts: one is to use a 150mm steel ruler, and the steel ruler is moved every 1oomm for ten times; the other is to use 1m steel The ruler does not move, but takes ten points in sequence according to the corresponding scale line. It is obvious that the error of the second method is relatively small. Because of the former method, due to multiple movements of the measurement reference, two or more assembly errors (tools, operating errors) are superimposed together, and cumulative errors are generated. By the same token, when measuring the gap with a feeler gauge of specified degree, a single-page feeler gauge should be used as much as possible to measure more accurately, and avoid using two or more thin feeler gauges to measure.
3, master the law of change of error (eliminate system error)
If the variation law of the error is found and the value is ascertained, it is like trying to eliminate the error value during assembly. This kind of regular error is called systematic error. For example, when the inner diameter measuring claw of a vernier caliper wears out 0.02mm, making the reading of each measurement imaginaryly larger by 0.02mm, you can automatically subtract 0.02mm from the reading to get the actual reading you need. Another example is when the level of the bubble is inaccurate, after the positioning and U-turn inspection, it is found that the bubble is inaccurate. After positioning to a certain end, it is horizontal. Therefore, when looking at the level, you should deliberately make the main bubble to a certain end. , So that the parts reach a level state.
4. Reasonable allocation or adjustment error value (reduce assembly error)
1). Mutual loan
When large castings such as the drawing locomotive face, bottom plate, roving frame head and tail wall panels, frame, and face are twisted and deformed, due to the inconvenience of orthopedics, only the verticality or levelness of multiple points can be checked to make the readings positive and negative after flat mounting The maximum value of the direction is equal, or the difference after subtracting the maximum value of the positive and negative directions is not greater than the allowable error. This method is called the mutual loan method.
2). Adjustment method
When the cumulative error in assembly exceeds the allowable error, the size, shape or shape of one of the links can be changed, or an unimportant size can be discarded without control, so that the total size is within the allowable range. This changeable link is called the “adjustment ring”. For example, when adjusting the draw frame roller seat to open the gear, first determine the left and right positions of the upper wall panel from the outer line of the front of the car, and then set the first roller seat position based on the upper wall panel of the front of the car. Set the position of the second, third, and fourth roller seat in turn, and the size between the fourth roller seat and the upper wall panel of the car can only be abandoned, and it is impossible to correct it. In actual work, the size, shape or position of the adjustment ring Changes are often achieved by filing, padding, welding, or adjusting with adjustable parts, such as adjusting screws, adjusting washers, and foot pads. Using these parts to adjust can improve assembly accuracy and save manual work. File repair and other work.
3). Select right assembly method
In order to reduce assembly errors and improve the accuracy of parts assembly, parts with certain errors can also be matched or grouped through selection, so that the upper and lower errors between the parts can be matched to appropriately improve the accuracy, which is called selective assembly. For example, group the rubber roller core and the iron shell to make the gap consistent; divide the diameter of the rubber roller into several gears to make the diameter of the rubber roller of the same machine or the same zone be the same.

What is machining accuracy, machining error, tolerance?

October 23, 2020

1. Machining accuracy: the degree to which the actual geometric parameters (size, shape and position) of the part after processing are in line with the ideal geometric parameters. The higher the degree of conformity, the higher the processing accuracy.
2. Machining error: the degree of deviation of the actual geometric parameters of the part from the ideal geometric

U-type-flange-butterfly-valve-2

parameters after processing is called the machining error. The magnitude of machining error indicates the level of machining accuracy, and machining error is a measure of machining accuracy.
3. Tolerance refers to the allowable error of the part processing clock.
What is the difference between them? “processing accuracy” and “processing error” are two different concepts for evaluating the accuracy of geometric parameters of parts. In the actual production, the method of controlling the processing error or the modern active adaptation processing method is used to ensure the processing accuracy.
Machining accuracy and machining error are described from different angles, but the size of the machining error is measured by the deviation of the actual measurement of the part, and the level of machining accuracy is measured by the tolerance level or tolerance value, and by the machining error To control the size. Generally speaking, the machining accuracy can only be guaranteed when the machining error is less than the tolerance.

Types of mechanical transmission

October 23, 2020

There are many forms of mechanical transmission, which can be divided mainly into two categories:
1. Friction transmission that transmits power and motion by friction between parts, including belt transmission, rope transmission and friction wheel transmission. Friction transmission is easy to achieve stepless speed change, and it can mostly adapt to transmission occasions with large shaft spacing. Overload and slip can also play a role in buffering and protecting the transmission device. However, this type of transmission is generally not used in high-power applications and cannot guarantee accuracy. The transmission ratio.
2. The meshing transmission of power or movement by the meshing of the driving part and the driven part or the meshing of intermediate parts, including gear transmission, chain transmission, spiral transmission and harmonic transmission. The meshing transmission can be used in high-power applications with accurate transmission ratio, but generally requires higher manufacturing accuracy and installation accuracy.

According to the forms of force transmission, mechanical transmission can be divided into:

1 Friction drive.
2 Chain drive.
3 Gear drive.
4 Belt drive.
5 Turbo worm drive.
6 Ratchet drive.
7 Crankshaft connecting rod drive
8 Pneumatic transmission.
9 Hydraulic drive (hydraulic planer)
10 Universal joint drive
11 Wire rope drive (most widely used in elevators)
12 coupling drive
13 Spline transmission.
1. Features of belt drive
Including driving wheel, driven wheel and endless belt.
1) It is used in the situation where the two axes are parallel and the rotation direction is the same, which is called the concept of opening motion, center distance and wrap angle.
2) The belt type can be divided into three categories: flat belt, V belt and special belt according to the cross-sectional shape.
3) The focus of application is: calculation of transmission ratio, stress analysis and calculation of belt, and allowable power of a single V belt.
Advantages-suitable for transmission with a large center distance between two axles; the belt has good flexibility, can alleviate impact and absorb vibration; slip when overloaded to prevent damage to other parts; simple structure and low cost.
Because the belt is elastic and is driven by friction, it has a simple structure, stable transmission, low noise, and can buffer and absorb vibration. When overloaded, the belt will slip on the pulley and protect other parts from overload. It is suitable for center distance Advantages such as larger transmission.
But belt transmission also has many shortcomings. The main ones are: accurate transmission ratio cannot be guaranteed, transmission efficiency is low (approximately 0.90～0.94), belt service life is short, and it is not suitable for use in high temperature, flammable, oil and water situations.
2. Gear transmission
Classification: plane gear transmission, space gear transmission.
Features
Advantages-Wide range of applicable peripheral speed and power; accurate, stable, and high-efficiency transmission ratio; high reliability and long life; transmission between parallel shafts, intersecting shafts at any angle and intersecting shafts at any angle can be realized.
Disadvantages-requires higher manufacturing and installation accuracy, higher cost; not suitable for long-distance transmission between two shafts.
The names of the basic dimensions of involute standard gears include addendum circle, tooth root circle, index circle, touch number, pressure angle, etc.
1. The range of power and speed transmitted by the gear is very large, the power can be as small as hundreds of thousands of kilowatts, and the peripheral speed can be as small as more than one hundred meters per second. The gear size can range from less than 1mm to more than 10m.
2. Gear transmission belongs to meshing transmission, the gear tooth profile is a specific curve, the instantaneous transmission ratio is constant, and the transmission is stable and reliable.
3. High gear transmission efficiency and long service life.
4. There are many kinds of gears, which can meet the needs of various transmission forms.
5. The manufacturing and installation of gears require high precision.
4. Features of chain drive
1) To ensure a more accurate transmission ratio (compared with belt transmission)
2) Power can be transmitted when the center distance between the two shafts is far (compared to gear transmission)
3) Can only be used for transmission between parallel shafts
4) After the chain wears out, the chain links become longer, which is easy to cause chain disconnection.
5. Worm gear drive
It is suitable for movement and dynamics between two axes that are vertical and not intersecting in space.
Features
Advantages-large transmission ratio. ; Compact structure size.
Disadvantages-large axial force, easy to heat, low efficiency; only one-way transmission.
The main parameters of the worm gear drive are: modulus, pressure angle, worm gear index circle, worm index circle, lead, number of worm gear teeth, number of worm heads, transmission ratio, etc.
Single-stage transmission can obtain a large transmission ratio, compact structure, smooth transmission, no noise, but low transmission efficiency. Two-stage transmission solves the shortcomings of single-stage transmission.
6. The characteristics of spiral transmission: high transmission accuracy, stable operation, no noise, easy to self-lock, and can transmit greater power.

In the valve industry, there are many ways to open and close the valve plate. we call it valve drive method. as below:

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

See the link for more details: https://www.tanghaivalve.com/valve-model-establishment-and-meaning/

Form and types of Gear transmission

October 23, 2020

Gear transmission types:

As per the mutual position of the two wheel axes, gear transmission can be divided into plane gear transmission and space gear transmission.
According to the type of gear transmission:

BS5163-BB-NRS-soft seated-wedge gate valve-DN700-PN16-bevel gear (8)

1. According to the relative position of the two shafts and the direction of the gear teeth, it can be divided into the following types:
<1>Cylinder gear drive;
<2>Bevel gear transmission;
<3> Cross-axis helical gear transmission.
2. According to the working conditions of the gear, it can be divided into:
<1> Open gear transmission, the gears are exposed, and good lubrication cannot be guaranteed;
<2>Half-open gear transmission, the gear is immersed in the oil pool, with a protective cover, but not closed;
<3> Closed gear transmission, gears, shafts and bearings are all installed in a closed box, with good lubrication conditions, difficult to enter dust, accurate installation, gear transmission with good working conditions, and it is the most widely used gear transmission.
3. According to the hardness of the tooth surface:
<1>Soft tooth surface gear The hardness of the tooth working surface is less than or equal to 350HBS or 38HRC;
<2>Hard tooth surface gear The hardness of the tooth working surface is greater than 350HBS or 38HRC. When a pair of gears are driven.

The form of gear transmission:
1. Parallel shaft gear (cylindrical gear)
(1) Spur gear: A straight cylindrical gear with tooth ribs parallel to the axis.
(2) Rack (Rack): A linear gear that meshes with a spur gear. It can be said to be a special situation when the pitch of the gear becomes infinite.
(3) Internal gear: The inner gear of a straight cylinder that meshes with the spur gear.
(4) Helical gear: Cylindrical gears with helicoid teeth.
(5) Helical rack: a linear gear that meshes with a helical gear.
(6) Double helical gear: a helical gear formed by left and right spiral tooth ribs.

2. Right-angle shaft gear (bevel gear)
(1) Straight bevel gear: A bevel gear whose tooth ribs are consistent with the generatrix (straight line) of the pitch cone.
(2) Spiral bevel gear: A bevel gear with a bevel line with a spiral angle.
(3) Zero helical bevel gear (Zerol bevel gear): a bevel gear with zero helix angle.

3. Gears with staggered shafts (worm gear and worm)
(1) Cylindrical worm gear: Cylindrical worm gear is the general name of worm (Worm) and gear (Wheel).
(2) Staggered helical gear (screw gear): This is a cylindrical helical gear, which is called when it is used for transmission between staggered shafts (also known as skew shafts).
(3) Other special gears: Face gear: a disc-shaped face gear that can mesh with a spur gear or a helical gear. Concave worm gear: Concave worm gear and its meshing gear. Hypoid gear: Conical gear that conveys the wrong axis. The shape is similar to a curved bevel gear.

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Types of mechanical transmission

Form and types of Gear transmission

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