What is machining accuracy, machining error, tolerance?

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

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.

What is the transmission ratio

In a mechanical transmission system, the ratio of the angular velocity or rotational speed of the driving wheel at the beginning and the driven wheel at the end.
Transmission ratio (i) = ratio of driving wheel speed (n1) to driven wheel speed (n2) = inverse ratio of gear index circle diameter = ratio of driven gear teeth (Z2) to driving gear teeth (Z1).
That is: i=n1/n2=D2/D1 i=n1/n2=z2/z1
For multi-stage gear transmission
1: The transmission ratio between every two shafts is calculated according to the above formula
2: The total transmission ratio from the first axis to the nth axis is calculated according to the following formula: Total transmission ratio ι=(Z2/Z1)×(Z4/Z3)×(Z6/Z5)……=(n1/n2)× (N3/n4)×(n5/n6)……

For multi-stage gear transmission

For multi-stage gear transmission

Extended information

The ratio of the angular velocities of the two rotating components in the mechanism is also called the speed ratio. The transmission ratio of component a and component b is Ⅰ=ωa/ωb=na/nb, where ωa and ωb are the angular velocities (radians/sec) of components a and b, respectively; na and nb are the rotational speeds of components a and b respectively ( Rpm) (Note: a and b after ω and n are subscripts).
When the angular velocity in the formula is an instantaneous value, the obtained transmission ratio is the instantaneous transmission ratio. When the angular velocity in the formula is an average value, the obtained transmission ratio is the average transmission ratio. For most gear transmissions and friction wheel transmissions with the correct tooth profile, the instantaneous transmission ratio is unchanged; for chain transmission and non-circular gear transmission, the instantaneous transmission ratio is variable.
For meshing transmission, the transmission ratio can be expressed by the number of teeth Za and Zb of wheel a and wheel b, i=Zb/Za; for friction transmission, the transmission ratio can be expressed by the radius Ra and Rb of wheel a and wheel b, i=Rb/Ra, At this time, the transmission ratio generally means the average transmission ratio.
In hydraulic transmission, the transmission ratio of the hydraulic transmission element generally refers to the ratio of the turbine speed S and the pump wheel speed B, that is, =S/B. Hydraulic transmission elements can also be combined with mechanical transmission elements (generally with various gear trains) to obtain various transmission ratios of different values ​​(see gear trains for gear train transmission ratios).

Types of mechanical transmission

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/

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife 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

Related news/knowledge:
What is the transmission ratio
What is the positive transmission of gears
Form and types of Gear transmission
Stainless steel valve material parameters and specific applications

Form and types of Gear transmission

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)

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.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife 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

Related news/knowledge:
What is the positive transmission of gears
Types of mechanical transmission
Stainless steel valve material parameters and specific applications

How to Find Gear Modification Coefficient

How to calculate gear modification coefficient:
1. Total displacement coefficient:

Total displacement coefficient

Total displacement coefficient

2. Coefficient of variation of center distance:

Coefficient of variation of center distance

Coefficient of variation of center distance

3. Coefficient of change of addendum height:

Coefficient of change of addendum height

Coefficient of change of addendum height

4. The modification coefficient table of the number of teeth z=8~20 cylindrical gear:

The modification coefficient table of the number of teeth z=8~20 cylindrical gear

The modification coefficient table of the number of teeth z=8~20 cylindrical gear

Gear Modification Coefficient

Gear Modification Coefficient

What is the gear modification coefficient

The standard gear transmission has some limitations:
(1) Limited by undercutting, the number of teeth should not be less than Zmin, making the transmission structure not compact enough;
(2) Not suitable for occasions where the installation center distance a’is not equal to the standard center distance a. When a'<a, it cannot be installed, when a’>a, although it can be installed, it will produce excessive backlash and cause shock and vibration, which will affect the stability of the transmission;
(3) When a pair of standard gears are driven, the pinion has a small tooth root thickness and more meshing times, so the strength of the pinion is low, and the wear of the tooth root is also serious. Therefore, the pinion is easy to be damaged, and it also limits The carrying capacity of the big gear.
In order to improve the performance of gear transmission, a shifted gear appeared. As shown in the figure, when the tooth top line of the rack slotting tool exceeds the limit meshing point N1, the cut gear will undercut. If the rack is inserted away from the wheel center O1 for a certain distance (xm) and the tooth top line no longer exceeds the limit point N1, the cut gear will not undergo undercutting, but at this time the index line of the rack and the division of the gear The degree circle is no longer tangent. The gear cut after changing the relative position of the tool and the tooth blank is called the displacement gear, the distance xm the tool moves is called the displacement, and x is the displacement coefficient. The displacement of the tool away from the wheel center is called positive displacement, at this time x>0; the displacement of the tool moving closer to the wheel center is called negative displacement, at this time x<0. The standard gear is the gear with the modification coefficient x=0.

what is bevel gear?

The bevel gear is used to transmit the movement and power between the two intersecting shafts. In general

bevel gear

bevel gear

machinery, the angle of intersection between the two shafts of the bevel gear is equal to 90° (but it may not be equal to 90°). Similar to cylindrical gears, bevel gears have indexing cones, addendum cones, tooth root cones and base cones. The cone has a big end and a small end, and the circle corresponding to the big end is called the index circle (its radius is r), the addendum circle, the root circle and the base circle. The movement of a pair of bevel gears is equivalent to a pair of pitch cones for pure rolling.
Application field
Industrial transmission equipment, vehicle differential
Classification
Straight tooth, helical tooth, curved tooth
Features
Noise reduction, shock absorption, light weight, low cost, etc.

Bevel gear actuator is coded 5 in the valve naming system in China, see link: https://www.tanghaivalve.com/valve-model-establishment-and-meaning/

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

1. Formation of tooth profile
The formation of the tooth profile of bevel gears is similar to that of cylindrical gears, except that the base cone is

The formation of spherical involute

The formation of spherical involute

used instead of the base cylinder. As shown on the right, the generating surface S is tangent to the generatrix of the base cone. When the generating surface S is purely rolling along the base cone, any straight line OK on the

generating surface contacting the generatrix ON of the base cone will form an involute curved surface in space. This curved surface is the tooth profile curved surface of the straight bevel gear. The trajectory of each point on the line OK is an involute (the involute at the vertex O is a point). Each point on the involute NK is equidistant from the cone O, so the involute must be on a spherical surface centered on the cone O and the radius is OK, that is, NK is a spherical involute.
2. Back cone and equivalent gear
The following figure shows a pair of special bevel gear drives. Among them, the number of teeth of wheel 1 is, the indexing circle radius is, and the reference cone angle is; the number of teeth of wheel 2 is, the indexing circle radius is, the indexing cone angle=90°, and the indexing cone surface is A plane, this kind of gear is called a crown gear.

Equivalent gear of bevel gear

Equivalent gear of bevel gear

The large end node P of the wheel 1 is used as the vertical line of the indexing cone generatrix OP, crossing its axis and point O1, and then taking O1 point as the cone tip and O1P as the generatrix, making a cone tangent to the large end of wheel 1 , Call this cone the back cone of wheel 1. In the same way, the back cone of wheel 2 can be made. Since wheel 2 is a crown wheel, its back cone becomes a cylindrical surface. If the back cones of the two wheels are expanded, the back cone of wheel 1 will be expanded into a sector gear, and the back cone of wheel 2 will be expanded into a rack, that is, after the back cone is expanded, the two are equivalent to gears and teeth. Strip meshing transmission. According to the Fan Cheng principle, when the tooth profile of the rack (that is, the back cone of the crown wheel) is a straight line, the tooth profile of the wheel 2 on the back cone is an involute.

Imagine filling up the gap of the unfolded sector gear, and you will get a cylindrical gear. This imaginary cylindrical gear is called the equivalent gear of the bevel gear, and the number of teeth Zv is called the equivalent number of teeth of the bevel gear. The tooth profile of the equivalent gear and the tooth profile of the bevel gear on the back cone (that is, the big end tooth profile) are consistent, so the modulus and pressure angle of the equivalent gear are consistent with the modulus and pressure angle of the large end of the bevel gear. As for the equivalent number of teeth, it can be obtained as follows:

As can be seen from the figure above, the index circle radius of the equivalent gear of wheel 1 is
γv1=γ1/cosδ1=z1m(2cosδ1)

So
zv1=z1/cosδ1

For any bevel gear there is
zv=z/cosδ

With the help of the concept of bevel gear equivalent gear, the correct meshing condition of a pair of bevel gears should be that the modulus and pressure angle of the large ends of the two wheels are equal respectively; the coincidence degree of a pair of bevel gear transmission can be calculated approximately according to the coincidence degree of the equivalent gear transmission ; In order to avoid undercutting of gear teeth, the minimum number of teeth for bevel gears without undercutting zmin=zvmincosδ
3. Analysis of gear tooth force
Similar to the cylindrical gear, the nominal normal load Fn is decomposed into the circumferential force Ft1, the radial force Fr1 and the axial force Fa1 at the average index circle of the pinion gear. The direction of each force is shown in the figure on the right, and then according to the force balance The geometric relationship between the conditions and the forces is calculated, namely

bevel gear force analysis

bevel gear force analysis

Force Analysis of Straight Bevel Gear

Force Analysis of Straight Bevel Gear

 

The force analysis on the big gear is similar to that on the small gear.
4. Geometric parameters and calculations
Bevel gears use the big end parameter as the standard value, so when calculating their geometric dimensions, the big end should also prevail. As shown in the figure below, the index circle diameters of the two bevel gears are respectively
d1=2Rsinδ1, d2=2Rsinδ2

In the formula, R is the distance from the tip of the indexing cone to the large end, which becomes the cone distance; δ1 and δ2 are the indexing cone angles of the two bevel gears (referred to as the cone angle for short).
The transmission ratio of the two wheels is

i12=w1/w2=z2/z1=d2/d1=sinδ2/sinδ1

When the shaft angle Σ=90° between the two bevel gears, the above formula becomes due to δ1+δ2=90°

i12=w1/w2=z2/z1=d2/d1=cotδ1=tanδ2

Geometry of bevel gear transmission

Geometry of bevel gear transmission

When designing bevel gear transmission, the value of the cone angle of the two wheels can be determined according to the above formula according to the given transmission ratio.

As for the size of the bevel gear tip cone angle and the tooth root cone angle, they are related to the head clearance requirements of the two bevel gears when they are meshed and driven. According to national standards (GB/T 12369-1990, GB/T12370-1990), equal head-clearance bevel gears are now used for transmission. The head clearance of the two wheels is equal from the big end to the small end of the gear. The cones of the degree cone and the root cone coincide at one point. However, because the generatrix of the tooth tip cone of the two wheels is parallel to the generatrix of the tooth root cone of the other bevel gear meshing with it, the cone tip no longer coincides with the indexing cone cone tip. This kind of bevel gear is equivalent to reducing the tooth tip height of the small end of the tooth, thereby reducing the possibility of the tooth tip being too sharp; and the tooth root fillet radius is larger, which is beneficial to improve the load capacity of the tooth, tool life and storage Oil lubrication.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife 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

Related news/knowledge:
Form and types of Gear transmission
What is the positive transmission of gears
what is Spur gear?
What is the gear modification coefficient

what is Spur gear?

Spur gear is a classification of gears. According to the relative position and tooth direction of a pair of gear axes (whether the two circles are parallel), it can be divided into plane gear rotation and space gear rotation; according to

Spur gear

Spur gear

the working conditions of the gears, it can be divided into open transmission and closed transmission; according to gear teeth or tooth profile. The gear is divided into straight teeth, helical teeth, herringbone teeth, or straight teeth, curved teeth, as per the shapes.

The code name is 4 for valve drive mode. see details at: https://www.tanghaivalve.com/valve-model-establishment-and-meaning/

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

Classification
Straight cylinder/spur gear
Meshing mode: external meshing, internal meshing, gear and rack
Basic characteristics: The tooth profile contact line is a straight line parallel to the axis. A pair of tooth profiles enter or exit the mesh at the same time along the tooth width, which is likely to cause shock and noise, and the transmission stability is poor.

Straight bevel gear:
Pitch cone, index cone, tooth tip cone, tooth root cone, base cone; used for transmission between intersecting two shafts, the gear teeth are distributed along the cone surface, and the size of the starting gear teeth gradually decreases toward the cone tip.
In order to enable the gear to rotate in both directions, the tooth profile on both sides of the gear tooth is composed of involute surfaces with the same shape and opposite directions. The names and symbols of each part are: addendum circle, tooth root circle, tooth Slot, tooth thickness, tooth pitch, modulus m, index circle d, tooth top and tooth root, top clearance

Gears are divided into spur gears, helical gears, herringbone gears, and curved gears according to the shape of the tooth line. The spur gears are gears whose teeth are parallel to the axis.

Surveying method:
The spur gear is one of the most common gears in actual production and use. Damage is inevitable during use. Therefore, it is necessary to make a new gear that is the same as the original one. For various reasons, the customer cannot provide the required spur gear. In order to ensure the normal use of the processed products, the gear drawings need to be accurately surveyed and mapped. The surveying and mapping work is a complicated task. Since there are few data on the surveying and mapping of spur gears, it is naturally inconvenient to consult. The work experience and methods of surveying and mapping spur gears in several actual production are summarized by the operation. The introduction is as follows:

First of all, although there are many parameters and dimensions of spur gears, the standard system of various gears stipulates the modulus or diameter pitch as the calculation basis for other parameters and the dimensions of each part. Therefore, the surveying and mapping work should make every effort to accurately determine the size of the modulus or the diametral pitch. At the same time, the pressure angle is the basic parameter to determine the tooth profile, and accurate determination is equally important.

Secondly, we need to understand the usage and production country of the gear being surveyed, so that we can estimate the standard system adopted by this gear. Generally speaking, China, Japan, Germany, France, Czech Republic, and the former Soviet Union all adopt the modular system. You can also observe the tooth profile of the gear. If the tooth profile is curved and the bottom of the tooth groove is narrow and arc-shaped, it can be preliminarily judged as a modular system. The standard pressure angle is mostly 20 degrees; the United States and the United Kingdom adopt diameter control, and the standard pressure angles are 14.5 degrees and 20 degrees. Observing that the tooth profile is relatively straight and the bottom of the tooth groove is wider and the arc is small, it can be preliminarily judged as the diameter control. The pressure angle is 14.5 degrees. You can also use gear hobs or standard rack samples to determine which pressure angle is. If you know the above conditions, you can actually survey and map:

(1) Method of measuring the diameter of the addendum circle Dm

First count the number of teeth Z of the gear, and then use a vernier caliper to measure the diameter Dm of the addendum circle. If it is determined that the gear is a modular standard tooth profile, its modulus:

m = Dm/Z+2

If it is determined that the gear is a standard tooth profile with diameter control, its diameter pitch is

Dp=25.4*(Z+2)/ Dm

However, it should be noted that if the number of teeth of the gear is even, it can be directly measured; if the number of teeth is odd, the measured size is not the addendum diameter Dm, but two teeth from the tip of a tooth to the opposite tooth space. The distance D between the intersection of the face and the addendum circle is smaller than the diameter of the addendum circle. Usually, Dm is multiplied by the correction coefficient k to get the addendum circle diameter D, namely:

Dm=k*D

In practice, the diameter of the addendum circle calculated by the odd-numbered gear addendum circle diameter correction coefficient k (Table 1) is generally small. The diameter of the addendum circle calculated using the corrected correction coefficient k (Table 2) according to the above formula is more Close to the real value, Table 2 is more accurate than Table 1, and the number of teeth is finer, for reference.

fig.1-Odd tooth gear Addendum circle diameter Correction coefficient K

fig.1-Odd tooth gear Addendum circle diameter Correction coefficient K

fig.2-Correction coefficient after correction k

fig.2-Correction coefficient after correction k

If the odd-numbered gear is not a gear shaft but has a hole, you can also measure the inner hole diameter d and the distance H from the hole wall to the tooth tip, and get the tooth tip circle diameter by the following formula:

Dm=2*H+d

(2) Method of measuring the height of the tooth

When the gear is inconvenient to measure the diameter of the addendum circle due to large modulus, tooth punching, etc., the full height h of the tooth can be measured to determine the modulus or diametral pitch. The total tooth height h can be measured with the depth tail needle of a vernier caliper, and other depth measuring tools are also available, depending on the site conditions; if the gear has a hole, the tooth total height h can be obtained indirectly by measuring the inner hole wall to the tooth tip and tooth root The subtraction of the distance is the total tooth height h, and the modulus or diametral pitch is calculated as follows:

m=h/2f+c Dp=25.4*(2f+c)/h

f:: Addendum height coefficient c: Radial clearance coefficient

f, c can be found by checking the gear standard system parameter table[3]

(3) Method of measuring center distance A

When the gear teeth are sharp, worn, or rolled, the above two methods cannot be measured. At this time, we can ask the customer to provide the center distance A of the two paired gears and the number of teeth of the two gears. These are easy to do. Calculate the modulus or diametral pitch as follows:

m=2*A/Z1+Z2 Dp=25.4*(Z1+Z2)/2*A

Z1, Z2: Number of teeth of matched gear

The modulus or diametral pitch calculated by any one of the three methods is compared with the standard modulus or diametral pitch series, and the closest one is fine.

The above are the commonly used methods for surveying and mapping spur gears in actual work. It is best to use two methods to check each other, so that the determined modulus or diameter section is more accurate, and the surveying and mapping work is basically completed. Special attention: The above surveying and mapping methods are carried out under the condition that we can pre-determine or investigate the standard system adopted by the gear. If the gear’s “all conditions are unknown”, the above methods can only be referred to, and then comprehensively judged by other means. It is believed that the above several surveying methods will be helpful to colleagues who have just joined the work soon or for the first time to survey and map spur gears. It is worth referring to.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife 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

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Check valve model designation method

Check valve model representation method  Check model preparation instructions
Check valve (one-way valve) model compilation instructions:
Check valve (one-way valve) is also called check valve or reverse flow valve. It is an automatic valve that opens or

tilting disc swing check valve (3)

tilting disc swing check valve (3)

closes the disc through the flow of the medium itself, and can only flow in one direction and cannot be reversed. It is mainly used for In the piping system, prevent the medium from flowing back or flowing backward. Check valves have a wide range of uses and types. Different types of check valves are also different in different pipelines, operating conditions and connection methods. In order to avoid selecting the wrong model when purchasing a valve, and causing unnecessary working conditions during the application process due to improper model selection, users should have more understanding and awareness of the following check valve model preparation instructions. Check valve (check valve) model compilation instructions are mainly to make a detailed analysis of the additional conditions, connection methods, structural forms, sealing materials, pressure ratings and shell materials of the check valve. Hope it helps you when you buy check valves.

Check valve (check valve) model representation method:
Additional code of check valve: HH: micro-resistance slow-closing check valve, BH: heat preservation check valve, HQ: rolling ball check valve;
Check valve code: H stands for check valve;
Connection code: 4 flanges, 6 welding, 7 wafer;
Code of structural form: 1: lift type, 2: vertical type, 4: swing type, 6: double flap type, 8: butterfly type;
Sealing material code: B: babbitt alloy, F: fluorine plastic, H: stainless steel, M: Monel alloy, X: rubber, Y: cemented carbide, W: direct processing;
Pressure grade code: 16=16 kg pressure, PN1.6-25mpa, pound grade 150LB-2500LB, Japanese grade 5K-63K;
Shell material code: Q: ductile iron, C: carbon steel, P:304, R:316, A: titanium alloy, I: chromium molybdenum steel;

Example of model preparation of check valve (check valve):
H44H-16C swing flange check valve
H: indicates the check valve;
4: Flange link;
4: Swing type;
H: The sealing material is stainless steel;
16: The pressure is 16 kg (1.6mpa)
C: The valve body is carbon steel.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife 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

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Valve model establishment and meaning (2)

In the previous article, we have introduced the establishment of code number of the valve model in China. However, there are more and more types of valves and materials, and the compilation of valve models is becoming more and

U-type flange butterfly valve, ductile iron, DI, center line,

U-type flange butterfly valve, ductile iron, DI, center line,

more complicated. Although China has a unified standard for valve model formulation, 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; each manufacturer that cannot use a unified numbering method can develop its own numbering method according to its own situation.
Here we mainly introduce the method of Chinese valve numbering, and we will give examples.
For example, the Z543H-16C bevel gear drive, flange connection, flat gate valve, nominal pressure 1.6MPA, valve body material is carbon steel.
Please refer to the previous article for the specific number code: Valve model establishment and meaning

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

Another example: D341X-16Q: Double flange butterfly valve, worm gear, soft centerline seal, nominal pressure 1.6Mpa, valve body material is ductile iron
Another example: D371X-10C: Wafer butterfly valve, turbo drive, soft centerline seal, nominal pressure 1.0MPA, and the valve body material is cast steel.
The valve number has 7 digits, and each position has a different code, so there are many changes in the valve, and the price will not be too uniform. And these 7 codes can’t represent the details of all materials. In addition to these 7 codes, there are many components that will greatly affect the use of the valve and the cost and price of the valve, such as the material of the valve plate, the material of the valve shaft, and the length of the valve structure.
Therefore, in the valve industry, there are many special products that need to be customized, and individual inquiries need to be checked separately, and special circumstances require special treatment.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife 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

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