Calculation task.
Task: Calculate the diameter of the diaphragm hole installed on a section of the pipeline at which the maximum pressure drop Δр would correspond to the maximum flow rate Q m = 80 t/hour. Also calculate the value of irretrievable pressure loss corresponding to the maximum flow rate
Initial data:
Pipeline diameter at normal temperature (20°C) D 20 = 200 mm;
Pipeline material Steel 20;
Diaphragm material Steel 1Х18Н9Т;
Pressure in front of the diaphragm p 1 = 100 kgf/cm 2 ;
Steam temperature t = 400 °C;
Pressure drop Δр = 0.4 kgf/cm 2 ;
Pipe diameter at operating temperature
where is selected from table 15.1 (S. F. Chistyakov, D. V. Radun Thermal measurements and instruments) depending on the operating temperature and pipeline material.
D = 200 mm∙1.0052 = 201.04 mm
Let us determine the vapor density at p = 100 kgf/cm 2 and t = 400°C from the tables of the thermophysical properties of water and water vapor.
p = 100 kgf/cm 2 = 9.8066 MPa
r = 36.9467 kg/m 3
Let's determine the average consumption.
It is known that for this method of determining flow 
Then 
t/h
Let us determine the product am from formula (15-14) (S. F. Chistyakov, D. V. Radun Thermal measurements and instruments):
,
where e is a correction factor taking into account the compressibility of the medium. As a first approximation, we assume that steam is not compressible, then e = 1.
Δр = 0.4 kgf/cm 2 = 39226.4 Pa
Let's use table 15.3 (S.F. Chistyakov, D.V. Radun Thermal measurements and instruments) to compile a table of coefficients a and am for a pipeline diameter D = 200 mm depending on the diaphragm module m.
The calculated value of am corresponds to the values of m belonging to the interval 0.5¸0.6.
Using linear interpolation, we determine the exact value of m.
Let's define e in the second approximation.
The correction factor e depends on the modulus m, the adiabatic expansion index, as well as on the ratio Δр ср /р 1 .
Let's determine the ratio Δр ср /р 1 .
From formula (15-29)
The adiabatic expansion index is determined from Table 15.5 depending on the operating temperature of the steam.
At t = 400°C c = 1.29
Let's determine e using the formula:
We determine am in the second approximation, since the difference between the values of e obtained in the first and second approximation is more than 0.0005
e 1 - e 2 = 1 – 0.99900 = 0.001 > 0.0005
where is the coefficient of thermal expansion of the diaphragm material, determined from Table 15.1 depending on the diaphragm material and operating temperature.
mm
The value of irretrievable pressure loss will be determined from Table 15.2 depending on the module m.
then p n = 0.412∙0.4 = 0.165 kgf/cm 2
Homework tasks.
Task No. 1
Initial data:
t 1 = 100°C; t 2 = 50°C; t 0 = 0°C
Define: E(t 1, t 0); E(t 2 , t 0)
E Fe-Cu (t, t 0) = E Pt-Fe (t, t 0) + E Pt-Cu (t, t 0)
Let's use Table 4.1 from this textbook to determine the thermo-EMF of Pt – Fe, Pt – Cu pairs at t 1 = 100°C, t 0 = 0°C.
Pumps K 20/18a create a pressure in the networks that exceeds the maximum permissible
45 m p.6.7 at 5 m, pumps K 45/30 - at 20 m.
To reduce the hydrostatic pressure at fire hydrants on floors 1–7, we provide for the installation of diaphragms.
Fire hydrants on the 1st floor are located at a height of 2.35 m from the ground surface, and each one located above is 2.8 m higher than the one below. The magnitude of excess hydrostatic pressure at fire hydrants is equal to the difference between the excess pressure in the network and the geometric height of the hydrants. The diameter of the diaphragm opening is determined by the nomogram of the drawings. 5 . Diaphragms are installed between connecting heads and fire hydrants.
The calculation results are shown in Table 9.
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Table 9. Calculation of diaphragm hole diameters |
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Floor number |
The amount of excess pressure at the PC and connections, Нср, m |
Diaphragm hole diameter, mm |
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Household drinking water supply |
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5 - 2,35 = 2,65 | ||||||||
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Household fire water supply |
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Hot water supply |
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To reduce the excess hydrostatic pressure in the hot water supply network at water taps on the 1st–7th floors, in accordance with the recommendations of clause 10.9, we provide for the installation of pressure regulators KFRD-10-2.0 on the supply lines to apartments. The pressure after the regulator is 0.05 MPa (5 m).
5. Calculation and design of sewerage
When designing the internal sewage system of buildings, they are guided by the requirements. In a residential building, we design a domestic sewage system to drain wastewater from sinks, washbasins, bathtubs, and toilets installed in kitchens and bathrooms. The diameters of outlet pipes from sanitary fixtures are assigned no less than those given in Appendix 2. We lay pipes with a slope of 0.03 with a nominal diameter
50 mm and 0.02 at 100 mm. We assign the diameter of the riser no less than the largest diameter of the outlet pipes connected to it and check for missing the calculated flow rate in clause 18.5.
The maximum second wastewater flow rate q s, l/s, is determined according to clause 3.5 using the formulas
a) with a total maximum second water flow in a building or structure q tot 8 l/s
b) at q tot 8 l/s
, l/s.
Size 
– wastewater flow rate from sanitary fixtures, l/s, is taken in accordance with Appendix 2. The device with the greatest water removal is taken as the design one.
In accordance with clause 17.29, we assign the outlet diameter to be no less than the largest diameter of the risers connected to it.
For the designed residential building, we provide for the installation of an internal sewer network (outlet pipes and risers), as well as sections laid in the basement, and outlets from low-pressure polyethylene pipes HDPE in accordance with GOST 22689.2-89 with a diameter of 50 mm and 110 mm for outlet pipes, 110 mm for risers.
Calculation of sewer pipelines should be carried out in accordance with clause 18.2, assigning the fluid speed V, m/s, and filling H/d in such a way that the condition is met
,
taking K = 0.5 – for plastic pipelines.
In this case, the fluid speed must be at least 0.7 m/s, and the filling of pipelines must be at least 0.3.
We check the designated pipe diameters for missing calculated flow rates using hydraulic calculations.
Total maximum second flow rate q tot = 4.05 l/s* (Table 1), i.e. less
8 l/s. Therefore, the estimated wastewater flow is determined by the formula
, l/s.
CALCULATION OF THE DIAPHRAGM FOR MEASURING THE FLOW OF DRY GAS AND STEAM;
CALCULATION OF DIAPHRAGM FOR WET GAS MEASUREMENT;
CALCULATION OF DIAPHRAGM FOR MEASURING LIQUID FLOW;
REGULATORY AUTHORITY CALCULATIONS;
SELECTION OF ACTUATOR MECHANISM.
FOR A COURSE PROJECT IN A SPECIAL DISCIPLINE
"INSTALLATION, ADJUSTMENT AND OPERATION OF ACS"
For students of specialty 220301. Automation of technological
Processes and production (by industry)
Lipetsk 2010
COLLECTION OF TECHNIQUES FOR A COURSE PROJECT IN THE DISCIPLINE
"Installation, adjustment and operation of self-propelled guns"
The collection of methods is intended for 4th year full-time students in specialty 220301. Automation of technological processes and production (by industry).
Compiled by: Polyakova T. F. – teacher of special education. disciplines
Reviewer: _______Kurlykin A.F. Deputy. Head of the Instrumentation and Automation Department of NLMK OJSC
Approved by the methodological council of the Lipetsk Metallurgical College and recommended for use by students as guidelines for the development of a course project in special fields. discipline "Installation, adjustment and operation of self-propelled guns."
| Sheet | |
| Introduction | |
| 1. Calculation of a diaphragm for measuring the flow of dry gas and steam | |
| 1.1 Necessary initial data | |
| 1.2 Determination of missing data for calculation | |
| 1.3 Determining aperture parameters | |
| 1.4 Checking the calculation | |
| 2. Calculation of a diaphragm for measuring wet gas flow | |
| 2.1 Necessary initial data | |
| 2.2 Determination of missing data for calculation | |
| 2.3 Determining aperture parameters | |
| 2.4 Checking the calculation | |
| 3.Calculation of a diaphragm for measuring liquid flow | |
| 3.1 Required input data | |
| 3.2 Determination of missing data for calculation | |
| 3.3 Determining aperture parameters | |
| 3.4 Checking the calculation | |
| Appendix A | |
| 4. Calculation of the regulatory body | |
| 4.1 Calculation based on throughput | |
| 4.2 Determination of the nominal diameter of the regulatory body | |
| 4.3 Determination of performance characteristics | |
| 5 Selection of actuator | |
| List of sources used | |
| Appendix B | |
| Appendix C | |
| Appendix D | |
| Appendix E |
Introduction
The discipline “Installation, adjustment and operation of automatic control systems” is one of the basic ones for training in specialty 220301 (2101) “Automation of technological processes and production”). While studying it, the student must know the main components of the ATS, the operating principle of all components and the structure of the relationship between all components. To ensure high-quality consolidation of the material being studied and the acquisition of practical skills, an individual course project is provided.
The ultimate goal of the course project is the construction of a substance consumption control system, implemented on a specific element base and aimed at performing certain tasks, which is determined by the course design task and an individual additional task. In addition to calculations, the course project requires the development of an Automation Scheme and a Principal Electrical (Pneumatic) Scheme and technological programming of the ACS. The course project is carried out individually on the basis of lectures, reference and other additional materials. The course project is designed for 30 hours. During the implementation of the project, 20 hours of consultations are provided. To assess student performance, the work is divided into stages, where each stage is a logically completed task:
the first stage is the implementation of calculation tasks;
the second stage is the development of an Automation Scheme;
the third stage – development of the electrical circuit diagram (Pneumatic);
the fourth stage is the development of technological programming of the substance consumption ATS.
Method for calculating a diaphragm for measuring the flow of dry gas and steam.
(according to Rules RD 50-213-80)
Table 1.1 - Required initial data
| Asked and accepted | Parameter designation | Unit |
| Maximum flow rate of the measured medium For gas (volume flow normalized to standard conditions): For steam (mass flow) | Q nom. max Q m. max | m 3 /hour kg/hour |
| Average flow rate of the measured medium For gas: For steam: | Q nom.avg Q m.avg | m 3 /hour kg/hour |
| Molar concentration of components of a dry gas mixture 1st component (name): 2nd component (name): * * nth component (name): | N 1 N 2 * * N n | share of units share of units * * share of units |
| Temperature of the medium in front of the diaphragm: | t | ºС |
| Excess pressure in front of the diaphragm: | R and | kgf/cm 2 |
| Average barometric pressure: | R b | mmHg. |
| Permissible pressure loss at Q max | R′ p | kgf/cm 2 |
| Internal diameter of the pipeline at t=20ºС | D 20 | mm |
| Absolute pipeline roughness | δ | |
| Available length of straight pipeline section: | L fri | |
| Type of local resistance at the beginning of a straight pipeline section: | - | |
| Pipe material | - | |
| Diaphragm material | - | |
| Differential pressure gauge type | - |
Note 1. The sum of the molar concentrations of all components of the gas mixture must be equal to 1.
Note 2. The absolute roughness of the pipeline depends on the material and condition of the inner surface of the pipeline. In the absence of data, you can take the value of absolute roughness according to (Appendix A, paragraph 1).
Note 3. Instead of the permissible pressure loss at maximum flow (Table 1.1 “Required initial data”), the maximum nominal pressure drop of the differential pressure gauge ΔР n can be set. The ΔР n values are selected from a number of numbers established by the standard, according to the expression:
ΔР n = n 1 10 x, where x is an integer, n 1 – 1; 1.6; 2.5; 4; 6.3.
Note 4. In the absence of data on the diaphragm material, one of the following grades of stainless steel X23N13, X18N25S2, 1X18N9T should be used.
January 22 2018
Aperture selection
1. General concept of diaphragms
The diaphragm is a washer with a certain hole diameter. Diaphragms increase the resistance of the fire hydrant, as a result of which the flow of water through it decreases. The diameter of the diaphragms is selected in such a way that all fire hydrants provide water flow close to the calculated value, regardless of the height of the building.
2.Calculation of diaphragms
The diameter of the diaphragm hole, depending on the bore diameter of the fire hydrant valve, pressure and flow rate, is determined by the calculation method or by a nomogram.
2.1.Calculation method for determining the diameter of diaphragms
The aperture diameter d is determined as follows:
d 2 /D 2 =F/F pc or d=D*(F/F pc) 0.5
Q=10*μ*F*(2*g*P) 0.5 ; Q n =Q in *(P n /P in) 0.5
according to the Darcy-Weisbach formula:
ΔР=Р n -Р in =ε*V 2 /(200*g);
from the formula we learn ε=200*g*ΔР/V 2
V=Q/F pc,
where D is the bore diameter of the fire hydrant valve; F, F pk - the area of the passage opening of the diaphragm and the fire hydrant valve, respectively; Qn, Qv - flow rate through the diaphragm and fire hydrant valve, respectively; ΔР is the difference in pressure between the locations of the lowest and highest fire hydrant valves; P n, P in - pressure, respectively, of the lowest and highest valves of fire hydrants; ε—diaphragm resistance coefficient; V is the speed of water flow through the valve.
Table 1. Relationship between the diaphragm drag coefficient and the ratio of the diaphragm orifice area to the fire hydrant valve.
| index | meaning | ||||||
| diaphragm resistance coefficient, ε | 226,0 | 43,8 | 17,5 | 7,8 | 3,75 | 1,8 | 0,8 |
| F/F ratio pc | 0,1 | 0,2 | 0,3 | 0,4 | 0,5 | 0,6 | 0,7 |
2.2. Determining the diameter of diaphragms using a nomogram
To determine the diameter of the disk diaphragm according to the nomogram (Figure 1), on the left ruler (P) mark the point corresponding to the maximum pressure value on the fire hydrant valve, and on the right ruler (q) mark the point corresponding to the required or calculated flow rate. A straight line is drawn through these points. The point of intersection of this straight line with the middle ruler (Ø50-70) will be the desired value of the diaphragm diameter: on the left side - for the diameter of the fire hydrant valve DN50, and on the right - for the diameter DN65.
An example of determining the diaphragm diameter using a nomogram:
For example, it is necessary to determine the diameter of the diaphragm for valves DN 50 and DN65, if their pressure is 0.4 MPa, the flow rate through a manual fire nozzle is q = 5 l/s. To solve this problem, it is necessary to draw a straight line connecting these two values on the nomogram. The intersection point of this straight line with the middle ruler (Ø50-70) will give the desired value for the diaphragm diameter - Ø19mm (for a DN65 valve), or Ø18.7 mm (for a DN50 valve).
Picture 1.
Note: To determine the numerical value of the pressure at the fire hydrant valve in “MPa”, you need to divide the number on the left ruler (P) by 100.
The diaphragm should be installed between the fire hydrant valve and the connection head. This way, when the fire hose is disconnected from the valve, the diaphragm will be open to observe and check the diameter of the hole. The number of diaphragms of different diameters should be as small as possible. It is allowed to install diaphragms with the same hole diameter on 3-4 floors of a building.
In simple terms, a camera's aperture is the device through which light enters the camera's sensor. The diaphragm consists of so-called “petals”, the number of which can vary from three to twenty pieces. Depending on the light intensity, the petals reduce or increase the diameter of the light-transmitting hole. The principle of their action is similar to the pupil: in dim light it expands, in bright light it contracts.
To better understand the principles of calculating lens characteristics (including aperture values), you need to know what the focal length of the lens is.
Lens focal length
Focal length– this is the distance between the camera matrix and the main optical plane of the lens, provided it is focused to infinity. This indicator determines the viewing angle achieved by a particular lens. The larger the focal length, the smaller the viewing angle. The specifications usually indicate the minimum and maximum focal lengths that the lens provides. It is usually measured in millimeters.
The ratio of focal length to aperture size is called f-number. This is what determines the aperture value. The smaller this indicator, the larger the hole, and the more light penetrates the camera matrix. It is worth considering that the aperture value is often indicated as a fraction denominator, without specifying the focal length.
Possible f-number values are described by a special aperture scale, which is a sequence of numbers:
1 – 1.4 – 2 – 2.8 – 4 – 5.6 – 8 – 11 – 16 – 22 and so on.
The essence of the scale is that narrowing the lens aperture by half leads to a fourfold decrease in the amount of light entering the matrix. Doubling the focal length has a similar effect. The aperture scale is often placed on the lens barrel for the convenience of the photographer.
Lenses with the smallest f-numbers (f/1.2 – f/1.8) transmit the maximum amount of light. Such lenses are called fast lenses.
Lens aperture
Aperture- this is the degree to which the camera lens attenuates the light flux, or, in other words, the ability of the lens to convey the real brightness of the object. The higher the aperture, the better the quality of photographs taken in poor lighting conditions without the use of a tripod or flash. In addition, fast lenses allow you to take photographs with the fastest possible shutter speed.
The aperture value is determined by the maximum open aperture value. Together with the focal length, it is usually indicated on the rim of the lens. So, for example, the inscription 7-21/2.0-2.8 means that with a focal length of 7 millimeters, the aperture ratio is 2.0. Accordingly, with a focal length of 21 millimeters – 2.8.
When choosing a lens, it is worth considering that the maximum open aperture is used very rarely. At the same time, the price of fast lenses is significantly higher. For most buyers, there is no point in overpaying for an aperture ratio of 1:1.2; it is quite enough to buy a more budget option with an aperture ratio of 1:1.8.
Relative hole
The reciprocal of the aperture number is called relative hole. The relative aperture size determines how many times the focal length of the lens exceeds the diameter of its aperture. On the lens barrel, this indicator usually appears as a 1:2 fraction. These numbers mean that the hole diameter is half the focal length.
In various sources, the concepts of aperture value, relative aperture size and aperture itself are often described in scientific, obscure language. In order not to make a mistake when choosing a camera and not to get confused in the characteristics of the lens, it is worth remembering the dependencies that exist between them.
Thus, aperture is a constant property of optics that cannot be changed or adjusted. It should be remembered that aperture has no relation to the current aperture value. As mentioned above, its value is equal to the aperture value in the maximum open position.
Relative aperture, unlike aperture, is a variable value. You can adjust it using the aperture.