The calculation of variable pressure differential flow meters comes down to determining the hole diameter and other dimensions of the nozzle or diaphragm, the flow coefficient, the dynamic measurement range determined by the Reynolds numbers, the pressure drop and pressure loss on the orifice, the correction factor for expansion, as well as the error in measuring gas flow. For the calculation, the maximum (limit), average and minimum flow rates, ranges of changes in gas pressure and temperature, internal diameter and material of the measuring pipeline, gas composition or its density under normal conditions, permissible pressure loss or maximum pressure drop corresponding to the maximum flow rate must be specified. as well as the average barometric pressure at the installation site of the differential pressure meter-flow meter.

Calculation method. Before starting the calculation, we select the types and accuracy classes of the differential pressure gauge-flow meter, pressure gauge and thermometer. The calculation is carried out as follows.

1. Determine the auxiliary coefficient rounded to three significant figures WITH when substituting the value of the maximum (limit) flow into it Q n. etc, temperature and pressure, gas density under normal conditions ρ n, compressibility coefficient Z and diameter of the measuring pipeline D:

With the found value of C, two types of calculations are possible: based on a given pressure drop or based on given pressure losses. If the limit pressure drop Δ is set r pr, then according to the nomogram Fig. 11 we determine the preliminary relative narrowing m (module) of the narrowing device according to the found coefficient WITH and a given maximum pressure drop across the restriction device Δ r pr, . Found preliminary modulus value m substitute into the formula by definition tα and calculate the preliminary flow coefficient α .

2. We calculate the auxiliary coefficient accurate to four significant figures mα

Where ε - correction factor for gas expansion for the upper limit pressure drop of the differential pressure gauge Δ r pr , ; Δ r pr, - upper limit pressure drop across the restriction device, kgf/m 2.

3. Determine the refined value of modulus m with an accuracy of four significant figures using the formula

m = mα/α.

4. According to the specified module value m we find the new value of the correction factor for the expansion e and calculate the difference between the originally calculated value ε and clarified. If this difference does not exceed 0.0005, then the calculated values m And ε are considered final.

5. Determine the diameter d aperture holes with the finally selected m

6. Found values ​​of flow coefficients α , expansion correction factor ε , diameter d aperture openings, as well as Δ r pr, p 1, T 1, pH And Z we use it to determine gas consumption and check the calculation of the maximum gas consumption Q n. etc. Received value Q n. etc. should not differ from the specified value by more than 0.2%. If the found value of the maximum gas flow rate differs from the specified value by more than 0.2%, then the calculation is repeated until the required error in calculating the maximum gas flow rate and diaphragm parameters is obtained.

7. Determine new updated module values m, diameter d diaphragm openings, as well as flow coefficient α and recalculate. If the adjusted calculated value of the maximum gas consumption does not differ from the specified value by more than 0.2%, then the adjusted values m, d And α , are recorded in the calculation sheet of the restriction device.

8. Calculate the minimum and maximum Reynolds numbers and compare the minimum Reynolds number with the boundary values

9. Determine the thickness of the diaphragm E, width of the cylindrical part of the diaphragm e c, width of the annular slot With, as well as the dimensions of the annular chambers a And b.

10. Select the lengths of straight sections of measuring pipelines before and after the diaphragm.

11. Calculate the error in flow measurement

The obtained data is recorded in the calculation sheet of the restriction device and is the basis for its manufacture and installation.

Gas metering unit

Designed for commercial gas metering (measuring its consumption). The number of measurement lines depends mainly on the number of gas outlet pipelines from the gas distribution system. The technical design of gas flow measurement units must comply with the “Rules for measuring the flow of gases and liquids using standard restrictive devices” RD50-213-80.

Restriction device opening area ratio F 0 k The cross-sectional area of ​​the gas pipeline F G is called the module T(or relative area): m = F 0 /F G.

On gas pipelines, a diaphragm with a diameter of at least 50 mm is used as a constriction device, provided that its module has the following limits:

m = 0.05-0.64 - for diaphragms with an angular method of selecting differential pressure and gas pipelines with D y = 500-1000 mm;

t = 0.04 - 0.56 - for diaphragms with a flanged method of selecting differential pressure and gas pipelines with D y = 50 -760 mm.

Rice. 27 - Temperature-enthalpy graph of natural gas

The smaller the module, the higher the accuracy of gas flow measurement, but the greater the pressure loss Δр in the diaphragm.

The diameter of the diaphragm opening, regardless of the method of pressure drop, is taken to be d ≥ 12.5 mm, and the ratio of the absolute pressure at the exit from the diaphragm and at the entrance to it is ≥0.75.

In the gas pipeline near the diaphragm, the following conditions must be observed:

1) turbulent and stationary movement of gas flow in straight sections must be ensured;

2) there should be no changes in the phase state of the gas flow, for example, condensation of vapors followed by precipitation of condensate;

3) sediments in the form of dust, sand, etc. should not accumulate inside straight sections of the gas pipeline;

4) deposits (for example, crystalline hydrates) that change its design parameters should not form on the diaphragm.

However, on the inner wall of the gas pipeline, at the site where the restriction device is installed, deposition of solid crystalline hydrates is quite possible. And this leads to a significant error in measuring gas flow and a decrease in pipeline capacity, as well as clogging of impulse lines.

When designing a gas metering unit for a gas distribution system operating in hydrate formation mode, it is necessary to provide measures to prevent hydrate formation. Their occurrence can be prevented by heating the gas, introducing inhibitors into the gas pipeline, and purging the restriction device. A hole should be provided in the gas pipeline to remove sediment or condensate. The diameter of such a hole should not exceed 0.08D20, and the distance from it to the hole for measuring the pressure drop should be at least D20 or found from the table. 6. The axes of these holes should not be located in the same plane passing through the axis of the pipe.

There must be a straight section between the local resistance on the gas pipeline and the diaphragm, the length of which is understood as the distance between the end surfaces of the diaphragm and the local resistance (Fig. 28). The boundaries of local resistance are considered to be:

1) for an elbow - a section passing perpendicular to the axis of the gas pipeline through the center of the bending radius;

2) for welded contractions and expansions - welded seam;

3) for a tee at an acute angle or a branching flow - a section located at a distance of two diameters from the point of intersection of the pipeline axes;

4) for a welded group of elbows - a section located at a distance of one diameter from the weld closest to the diaphragm of the elbow.

Fig. 28. Installation diagram of diaphragm 1 - pressure gauge, 2 - thermometer, 3 - local resistance

In accordance with the requirements of Rules RD50-213-80, the measuring section of the gas pipeline must be straight and cylindrical, with a circular cross-section. The actual internal diameter of the section in front of the diaphragm is determined as the arithmetic mean of the measurement results in two cross sections directly at the diaphragm and at a distance from it 2D 20, moreover, in each of the sections in at least four diametric directions The results of individual measurements should not differ from the average value by more than 0.3% The internal diameter of the section at a length of 2D 20 after the diaphragm may differ from the internal diameter of the section before the diaphragm by no more than ±2%.

Maximum deviations for the internal diameter of pipes should not exceed the corresponding maximum deviations for the outer diameter, i.e. ±0.8%. It is allowed to mate the flange and pipeline holes along a cone that has a slope towards the diaphragm of no more than 1:10 and smooth roundings at the ends.

The sealing gaskets between the diaphragm and the flanges should not protrude into the internal cavity of the gas pipeline. When installing a diaphragm between the mounting flanges, the end of the gas pipeline must be directly adjacent to it.

The temperature behind the restriction device is measured at a distance of at least 5 D 20, but no more than 10 D 20 from its rear end. The diameter of the thermometer sleeve should not exceed 0.13 D 20. Thermometer sleeve immersion depth (0.3 - 0.5) D 20.

The inner edge of the hole for tapping pressure in the gas pipeline, in the flange and in the chamber should not have burrs; it is recommended to round it along the radius r = 0.ld of the hole. The angle between the axes of the hole and the chamber diaphragm is 90°.

Size d(diameter of individual hole) with module T< 0,45 не должен превышать 0,03D 20, and with modulus m > 0.45 it is within 0.01 D 20 d< 0.02D 20.

If the distance between the knees exceeds 15 D 20, then each knee is considered single; if it is less than 15 D 20, then this group of knees is considered as a single resistance of this type. In this case, the internal radius of curvature of the elbows must be equal to or greater than the diameter of the pipeline. The shortened length of the straight section in front of the diaphragm for any type of resistance, except for the thermometer sleeve, must be less than 10 D 20.

Gas consumption in general

Where Q M And Q V , - mass and volumetric flow rates of gas flow; A - diaphragm flow coefficient; ξ- gas expansion coefficient; d- diaphragm opening diameter; ΔP- pressure drop across the diaphragm; ρ - gas density.

In addition to diaphragms, restriction devices complete with differential pressure gauges, as well as pressure gauges, are used to measure gas flow.

Narrowing quick-change device (USB). When combined with a differential pressure gauge, this device (Fig. 29) allows you to measure the flow of gas transported through the gas distribution system by measuring the pressure drop occurring across the diaphragm and recording it with a differential pressure gauge.

Rice. 29 - Quick-change narrowing device USB 00.000.

1 - body: 2, 18 - loops; 3 - flange: 4, 16 - linings: 5. 9 - gaskets: b - cap nut: 7. 11 - rubber rings: 8 - studs: 10 - diaphragm: 12 - traffic jams: 13 - cuff: 14 - pipe: /5 - handle: 17 - cover: /9 -plate.

The gas pressure in front of the diaphragm is taken from cavity B of the positive chamber, made in the chamber body, and behind the diaphragm - from the cavity IN negative chamber in the flange (Fig. 29). Pressure is taken from these cavities through holes above the horizontal axis of the diaphragm (Fig. 29) A-A, and static pressure - from the cavity B through a separate hole (Fig. 29) B-B.

The tightness between the positive and negative chambers is ensured by uniform pressing of the rubber ring to the plane of the flange with studs. The movement of gas through the gas pipeline causes additional pressure on the diaphragm by the high-speed pressure. The window for removing the diaphragm is sealed with a gasket. Pre-tensioning of the gasket is ensured by studs. As the pressure in the pipeline increases, the gasket is additionally pressed against the surface of the positive chamber. In order to prevent the gasket from being bitten by the threads of the stud, a copper cuff is provided.

The joint between the flange and the body is sealed with an O-ring. Drainage lines are located at the bottom of the USB. Impulse and drain lines are plugged with process plugs. To facilitate the installation and dismantling of linings with D y = 200 mm and above, two handles allow.

The pad is designed to increase the rigidity and centering of the cover, and the hinge is used to install the cover in its working position.

Differential bellows recorder pressure gauges (DSS). Used to measure gas flow at gas distribution stations based on pressure drop in standard restriction devices.

The sensitive part of these differential pressure gauges is the bellows unit, the operating principle of which is based on the relationship between the measured pressure difference and the elastic deformation of helical coil springs, bellows and torque tube. The diagram of a recording bellows differential pressure gauge and the structure of the bellows block are shown in Fig. thirty.

The bellows block has two cavities (+ and -), separated by a base 8 and two bellows units 5 and //. Both bellows are rigidly connected to each other by a rod 12, the protrusion of which rests lever 7, fixed on axle 2. The axle is removed from the working pressure cavity using a torque tube /, the inner end of which is welded to the axle 2. a external - with the base of the torsion bar. Rod end 12 connected to a block of range helical coil springs using a bushing 10. The movement of the rod by lever 7 is converted into a rotation of axis 2, which is perceived through a system of levers by the arrow of a recording or indicating device. The internal cavity of the bellows and the base to which they are attached are filled with a liquid consisting of 33% pure glycerin and 67% distilled water. The freezing point of such a mixture is 17°C.

Both bellows have special valve devices that reliably keep liquid from flowing out of the bellows during unilateral overloads. The valve device consists of a cone at the bottom of the bellows and a sealing rubber ring 6. In case of one-sided overload, the conical valve of the bellows with an O-ring sits on the conical seat of the base and blocks the passage of fluid flow from the bellows, protecting it from destruction.

To reduce the influence of temperature on instrument readings due to changes in the volume of liquid, bellows 5 has a temperature compensator. Each nominal pressure drop corresponds to a specific range spring block 9.

Adjustment of bellows differential pressure gauges is carried out by changing the length of the adjustable leads. Setting the flow arrow to zero is achieved by changing the angle of the lever 4. The zero position of the device corresponds to an inclination angle of 28". The upper limit of measurement is adjusted by changing the rod lengths 3.

Odorization block

For timely detection of gas leaks in gas pipeline connections, in seals of shut-off and control valves, in connections of control and measuring equipment, etc., it is necessary to add substances with a sharp unpleasant odor, called an odorant, to natural gas. As such, ethyl mercaptan, pentalarm, captan, sulfan, etc. are used, most often ethyl mercaptan (its chemical formula is C 2 H 5 SH), which is a colorless transparent liquid with the following basic physicochemical properties:

The minimum amount of odorant in the gas must be such that the presence of gas in the room is felt at a concentration equal to 1/5 of the lower explosive limit, which corresponds for natural gas to 16 g of odorant per 1000 m 3 of gas.

Currently, synthetic ethyl mercaptan, which has the same chemical formula C 2 H 5 SH and is a deficiency, is used as an odorant. Instead, they use the SPM odorant developed by VNIIGAZ (TU 51-81-88), which is a mixture of low-boiling mercaptans: 30% ethyl mercaptan and 50-60% iso- and n-propyl mercaptans and 10-20% isobutyl mercaptans. Industrial tests of the SPM odorant have shown that its effectiveness is higher than ethyl mercaptan at the same consumption rate: 16 g per 1000 m 3 of gas.

Mixtures of C 3 - C 4 mercaptans are widely used abroad as odorants. It has been established that they are chemically more stable than ethyl mercaptan.

In winter it is usually greater than in summer. During the initial period of operation of a newly built gas pipeline, the odorization rate is also insufficient.

For odorization of gas, drip-type odorizers (manual), universal UOG-1 and automatic AOG-30 are used.

Odorization installation of drip type. It is universal, but is mainly used for gas flow rates of more than 100,000 m3/h. The odorization installation consists of (Fig. 33) a supply container 5 with a supply of odorant, which is a cylindrical vessel with a level measuring tube 13, which serves to determine the amount of odorant in the container and its consumption per unit of time: observation window /6 and the corresponding piping with impulse tubes and valves; underground tank 7 for storing odorant and valves 8, 10 for connecting hoses when transferring odorant from a supply container to an underground one.

Universal gas odorizer type UOG-1 (Fig. 34). When the main gas flow passes through the flow-measuring diaphragm, a pressure difference is created across which, under the influence of which, when the plus and minus cavities of the diaphragm are connected, a branch gas flow is formed. This flow flows through an injection dispenser, in which it is used as an ejector flow.

The latter, passing through the dispenser along the annular gap, creates a vacuum in it, under the influence of which the gas pipeline with a branch flow through the filter and the float chamber from parallel containers (consumable and measuring, having a level glass and a scale for monitoring the consumption of odorant per unit of time) enters odorant

The float chamber is designed to eliminate the influence of the odorant level on dosing. For this purpose, the float chamber and dispenser are positioned in such a way that the nozzle through which the odorant enters the dispenser coincides with the level of odorant maintained in the float chamber using a float. When the chamber is filled with odorant, the float moves down and opens the valve. During normal operation of the dispenser, the float makes an oscillatory movement with an amplitude of 3-5 minutes and a frequency proportional to the consumption of the odorant.

In order to reduce the consumption of odorant, the dispenser is equipped with a valve that shuts off the flow of odorant into the injector for a specified time. The valve is controlled by membranes. When applying pulse pressure to the cavity A(see Fig. 35) the valve blocks the passage of the odorant; when releasing pressure from the cavity A the membrane, under the influence of odorant pressure, returns to its original position and the valve opens the passage for the odorant.

Pressure setter in the cavity A The dispenser is served by a control system consisting of a time relay, an adjustable container and a valve.

Gas from the outlet gas pipeline enters the gas preparation unit to power the odorizer pneumatic system. The preparation unit consists of a filter, gearbox and pressure gauge. The gas in this unit is purified, the pressure is reduced to a supply pressure of 2 kgf/cm 2.

The cyclicity of the command to the dispenser valve is regulated by moving the piston of the adjustable container; the ratio of the time of the entire cycle to the time of the open position of the valve - by throttle using a stopwatch and a pressure gauge.

Below are the technical characteristics of odorizers UOG-1 and AOG-30

Technical characteristics of the universal odorizer UO G-1
Operating gas pressure, kgf/cm 2 ............ 2-12
Pressure drop across the diaphragm, kgf/cm 2, at a maximum gas flow of 0.6
Odorant throughput, cm 3 /h.. 57-3150
Maximum gas consumption to power the installation, m 3 /h 1
Odorization accuracy, % ± 10
Ambient temperature. ° C. . . .	.... From -40 to 50
Overall dimensions, mm: length.............	.... 465
width.................	.... 150
height.................	. . 800
Weight, kg...................	. . 63
Technical characteristics of the automatic odorization unit AOG-30
Operating gas pressure, kgf/cm 2 ............	2-12
Odorant throughput, cm/h....
Ratio of the highest flow rate of odorized gas to the smallest..................... Nominal number of strokes of the pump plunger in 1 min. Odorization accuracy, %................	5:1 4 to 12 ±10
Maximum gas consumption to power the installation, m 3 /h
Ambient air temperature, °C........	-40 to 50

Odorization block. Consists of an odorant dispenser, a float chamber, an inspection window, an odorant filter, a valve, a ball valve, a filter, a reducer, pressure gauges, a time relay, an adjustable container and a valve.

Odor dispenser(Fig. 35). It is an injector, where the odorant is supplied through nozzle 1, and the ejecting gas flow is supplied through the annular gap

RU. The dispenser chambers are sealed with rubber rings 3.

The operation of the dispenser with a control system for blocking the flow of odorant is carried out using valve 5 and a seat 4. Spring 8 ensures tight overlap of valve 5 with seat 4. Cavity pressure A The seat is closed under the action of the movement of the membrane 7. When pressure is released from the cavity A valve 5 returns to its original position. Under the influence of odorant pressure, membrane 6 moves.

The dispenser is equipped with a coupling 9, due to the rotation of which the gap changes T between nozzle 1 and mixer 10. Gap size T changes when calibrating the dispenser according to productivity, after which the position of coupling 9 is fixed with a lock nut 2.

Float chamber(Fig. 36). It consists of a body with a lid, inside of which there is a hermetically sealed float, attached to the rod with a cotter pin. The rod is equipped with a spool, which sits on the seat in the upper position. An alarm system sensor is installed in the cover on the bracket. A flag is mixed in the sensor slot, which, crossing the sensor’s working area, causes it to operate.

viewing window(Fig. 37). Consists of a body, a sleeve and a glass tube. The elements of the viewing window are sealed using rubber sealing rings.

Odorant filter(Fig. 38). It is a cylindrical body with a lid into which a cassette with a mesh bottom is screwed. The cassette is filled with a filter element - glass wool. The lid is sealed with an O-ring. The lower part of the housing is used as a sump and has a valve for draining the sludge.

Rice. 39. Time relay.

/ - throttle: 2 - intermediate ring: 3, 5 - membranes: 4 -

rod: b - cover: 7 - flange: 8 - screw: 9 - guides: 10 -

spring: 11 - valve: 12 - start button

Time relay(Fig. 39). Gas pressure is supplied to the cavity formed by an intermediate ring and two membranes, which are rigidly connected by screws through a flange and a ring with a rod. The rod has axial and radial holes. Under the action of the spring, the rod is in the upper position and rests against the flange.

The gas, through the axial hole in the rod and the throttle, enters the cavity formed by the lid and membrane, on which it presses. The rod moves down and opens the relief valve. A button is provided to start the time relay.

Adjustable capacity(Fig. 40). Consists of a body, covers, piston, screw and sealing tracks. Designed to regulate the supply of odorant to the gas pipeline.

Valve(Fig. 41). Its main elements are membranes, which have different affective areas and form two cavities: L and b, connected to each other by a valve through a regulating throttle. The flow area of ​​the throttle is adjusted by a needle. The needle is moved by a screw with a handwheel. There is a scale on the front side of the flywheel. The scale indicator is secured to the valve body with two screws.

Measuring capacitance (Fig. 42). It is a cylindrical vessel with a level measuring glass tube equipped with a scale 2. The glass tube is protected by a casing and sealed with rubber rings.

Proportional gas odorizer OGP-02. Designed to automatically introduce an odorant (ethyl mercaptan) into a natural gas stream (in proportion to its flow rate) in order to give the gas a specific odor that will facilitate the detection of leaks. Odorizer OGP-02 can be used outdoors in moderately cold climates at facilities with a nominal pressure of 16 kgf/cm2 and gas flow from 1000 to 100,000 m3/h.

The odorizer consists (Fig. 43) of a dispenser and a control container. The dispenser contains a nozzle and an odorant level regulator. Inside the control tank there is a stainless steel float, a rod, on the top of which a magnet is fixed. A magnetic odorant level indicator slides along the outer surface of the tube.

The operating principle of the OGP-02 odorizer is as follows (Fig. 43, 44). The odorant flows from the control tank through the valve until its level overlaps the lower edge of the level regulator. In the dispenser, using a level regulator and technological piping of containers, a constant, specified level of odorant is maintained. It is supplied to the gas pipeline due to the pressure drop across the flow meter diaphragm with the help of gas flow from the “plus” chamber through the impulse tube, nozzle, collector, and through tubes through the “minus” chamber into the gas pipeline. The gas flow from the nozzle, passing through the odorant layer, carries its vapors and small droplets into the collection, and from it into the gas pipeline.

The dispenser is refilled with odorant from the supply and control containers with the valve open.

Setting the odorizer to the required degree of gas odorization is carried out by changing both the thickness of the odorant layer above the upper end of the nozzle with a level regulator and the gas flow through the nozzle with a valve.

The consumption of odorant at any time during a certain interval (15-30 minutes) can be measured using a control container by closing the valve. The odorizer is adjusted for odorant consumption in proportion to gas consumption twice: when switching from winter to summer gas consumption, and vice versa.

Subsequently, the odorant consumption is automatically adjusted depending on changes in gas consumption.

Maintenance of the OGP-02 odorizer comes down to periodically filling the working container with odorant and then putting the odorizer into operation.

Rice. 44. Scheme of gas odorizer OGP-02.

/ - dispenser: // - working (consumable) capacity. /// - control capacity. 1 - 10 - valves.

Switch block

Designed, firstly, to protect the consumer’s gas pipeline system from possible high gas pressure; secondly, to supply gas to the consumer, bypassing the gas distribution system, through a bypass line using manual control of gas pressure during repair and maintenance work of the station.

The switching unit consists of valves on the inlet and outlet gas pipelines, a bypass line and safety valves. As a rule, this unit should be located in a separate building or under a canopy that protects it from precipitation.

Safety valves. Two safety valves are installed on the gas pipeline, one of which is working, the other is backup. Valves of the type SPPK (special full-lift safety valve) (Fig. 45; Table 10) and PPK (spring-loaded full-lift safety valve) are used. A three-way valve of the KTRP type is installed between the safety valves, always open to one of the safety valves. Shut-off valves should not be installed between the gas pipeline and the valves. The setting limits of the safety valves must exceed the rated gas pressure by 10%.

During operation, the valves should be tested for operation once a month, and in winter - once every 10 days with an entry in the operational log. Safety valves are checked and adjusted twice a year. about which they make a corresponding entry in the journal.

The rod of the safety relief valve SPPK4R (Fig. 45), on the one hand, is affected by gas pressure from the outlet gas pipeline, and on the other hand, by the force of a compressed spring. If the gas pressure at the outlet of the gas distribution system exceeds the specified value, then the gas, overcoming the force of the compressed spring, lifts the rod and connects the outlet gas pipeline to the atmosphere. After the gas pressure in the outlet gas pipeline decreases, the rod returns to its original position under the action of the spring, blocking the passage of gas through the valve nozzle, thus disconnecting the outlet gas pipeline from the atmosphere. Depending on the setting pressure, safety valves are equipped with replaceable springs (Table 11). Table 11 - Selection of springs for safety valves type SPPK and PPK

Valve	Setting pressure, kgf/cm	Spring number	Valve	Setting pressure. kgf/cm 2	Spring number
SPPK4R-50-16	1.9-3.5		PPK4-50-16	1,9-3,5
	3.5-6.0			3,5-6,0
SPPK4R-80-16	2.5-4.5			6,0-10,0
	4.5-7,0			10,0- 16,0
SPPK4R-100-16	1 ,5-3,5		PPK4-80-16	2,5-4,5
	3,5-9,5			4,5-7,0
SPPK4R-150-16	1,5-2,0			7.0-9.5
	2,0-3,0			9.5-13.0
	3,0-6,5		PPK4-100-16	1.5-3.5
SPPK4R-200-16	0,5-8,0			3.5-9.5
				9.5-20
			PPK4-150-16	2.0-3.0
				3.0-6.5
				6.5-11.0
				11 - 15,0

Table 12 - Overall and connecting dimensions, mm, and weight of valves type PPK4

In addition to valves of the SPPK type, spring safety flange valves of the PPK-4 type (Fig. 46, Table 12) for a nominal pressure of 16 kgf/cm 2 are widely used. Valves of this type are equipped with a lever for forced opening and control purging of the gas pipeline. The spring is adjusted with an adjusting screw.

Gas pressure from the gas pipeline enters the shut-off valve, which is held in the closed position by a spring through a rod. The spring tension is adjusted with a screw. The cam mechanism allows for control purging of the valve: by turning the lever, the force is transmitted through the roller, cam and guide bushing to the rod. It rises, opens the valve and a purge occurs, which indicates that the valve is working and the discharge line is not clogged.

PPK-4 valves, depending on the number of the installed spring, can be configured to operate in the pressure range from 0.5 to 16 kgf/cm 2 (Table 13).

Capacity of safety valves G. kg/h:

G - 220Fp .

Where F- valve cross-section, cm, determined for full-lift valves at h ≥ 0.25d according to addiction F = 0.785d2; for people with limited lift h≥ 0.05d - F= 2,22dh; d- internal diameter of the valve seat, cm; h- valve lift height, cm; R - absolute gas pressure, kgf/cm2; T - absolute gas temperature, K; M - molecular weight of gas, kg.

To discharge gas into the atmosphere, it is necessary to use vertical pipes (columns, candles) with a height of at least 5 m from ground level; which lead beyond the GDS fence to a distance of at least 10 m. Each safety valve must have a separate exhaust pipe. It is allowed to combine exhaust pipes into a common manifold from several safety valves with the same gas pressures. In this case, the common collector is designed for simultaneous discharge of gas through all safety valves.

Cranes. The valves installed in switching blocks, as well as in other sections of gas distribution pipelines, differ in the types of drives (Table 14).

1) crane type 11s20bk and 11s20bk1 - with a lever drive (Fig. 47, Table 15);

2) crane type 11s320bk and 11s320bk1 - with a worm drive (reducer) (Fig. 48; Table 16);

3) crane type 11s722bk and 11s722bk1 - with pneumatic drive (Fig. 49; Table 17);

4) faucet type 11s321bk1 - for installation without wells (Fig. 50; Table 18);

5) tap type 11s723bk1 - for installation without wells (Fig. 51, Table I9)

Rice. 47. Cranes 1c20bk and 11s20bk1.

1 - body; 2 - cork; 3 - bottom cover: 4 - adjusting screw; 5 - spindle 6 - check valve for lubrication: 7 - lubrication bolt. 8 - lever: 9 - oil seal.

Rice. 48. Cranes 11s320Bk and 11s320bk1.

1 - body: 2 - plug: 3 - bottom cover; 4 - adjusting screw: 5 - worm sector: b - worm. 7 - flywheel: 8 - lubrication bolt: 9 - check valve: 10 - gear housing: 11 - oil seal. 12 - spindle: 13 - lid.

Rice. 49. Cranes 11s722bk (a) and 11s722bk1 (b) with D at 50 and 80 mm.

/ - body: 2 - plug: 3 - heel; 4 - ball. 5 - set screw; 6 - coupling bolt: 7 - cap; 8 - bottom cover: 9 - stuffing box: 10 - spindle: 11 - bracket: 12 - lever arm; 13 - in and lk: 14 - stock: 15 - pneumatic drive; 16 - multiplier: 17 - terminal switch; 18 - nipple. / - version of flanged valves 1s722bks D 50, 80, 100 mm.

Rice. 50 Crane 11s321bk1

All of the listed valves are manufactured with ends for both flanged connections (the designation ends with the letters “bk”) and welded ends (the designation ends with the letters and number “bk1”). The valve body is made of steel, and the plug is made of cast iron. The taps are installed at ambient temperatures from -40 to 80° C.

On valves with a bypass, a pass-through valve D y = 150 mm is installed to facilitate opening the main valve by equalizing the pressure on both sides of the valve. The bypass valve is connected to the body of the main valve by bypass pipes.

A pneumatic drive crane consists of a crane assembly, a pneumatic drive and a multiplier. If necessary, the crane is controlled manually using a flywheel. The pneumatic actuator is pivotally connected to the valve body and provides reciprocating movement of the rod and rotation of the lever, rigidly connected to the spindle by a key. The position of the rod is adjusted by a fork pivotally connected to the lever.

A limit switch is installed on the gearbox cover, which cuts off the electric current in the control circuit at the end positions of the valve plug.

The multiplier is designed to supply special lubricant into the cavity under the top cover, as well as into the grooves of the body and plug. Lubricant ensures tightness and makes turning easier

traffic jams. To fill the multiplier with special lubricant, as it is consumed, a pneumatic lubricant pump is used.

The valve assembly consists of the following main parts: body, plug, bottom cover and an adjusting screw that presses the plugs against the body seal. A faucet with a lever (manual) drive consists of a faucet assembly, a gearbox or a handle.

The main unit of three-way valves used at gas distribution stations is a shut-off valve, consisting of a body, a plug and a gearbox.

6) Ball valves are also used at gas distribution stations (Fig. 52), the advantages of which over others are simplicity of design, direct flow, low hydraulic resistance, and constant mutual contact of sealing surfaces. Distinctive features of ball valves from others:

1) the body and plug of the faucet, due to their spherical shape, have

smaller overall dimensions and weight, as well as greater strength;

2) the design of valves with a spherical valve is less sensitive to manufacturing inaccuracies and provides much better tightness, since the contact surface of the sealing surfaces of the body and the plug completely surrounds the passage and seals the valve valve;

3) the manufacture of these taps is less labor-intensive. In ball valves with plastic rings, there is no need to grind in the sealing surfaces. Usually the cork is chromed or polished.

Ball valves are distinguished from others by a wide variety of designs. There are two main types of taps: with a floating plug and with floating rings.

Ball valves type KSh-10 and KSh-15 are designed to shut off pipelines, process, control and safety equipment.

The tightness of the shut-off assembly (ball plug-seat) is ensured by tight coverage of part of the spherical surface of the ball plug by the seat with some interference due to the ability of the seat material to deform when fastening the valve parts with coupling bolts. The materials for making the seat can be fluoroplastic, vinyl plastic, rubber or others that have plastic deformation properties close to the properties of the above materials. In case of wear of the sealing surfaces of the seat and loss of tightness of the shut-off assembly, the valve design provides for the possibility of restoring tightness by removing one or two gaskets installed on both sides between the body and the cover.

The Aleksin plant "Tyazhpromarmatura" has mastered the serial production of ball valves with D y - 50, 80, 100. 150. 200. 700, 1000. 1400 mm per r y - 80 kgf/cm 2 of a modernized design with a plug in the supports and a seal made of elastomeric material (polyurethane or other materials with high wear resistance).

The valve bodies with D y - 50 - 200 mm are stamped, with a flange connector, and with D y = 700. 1000. 1400 mm - all-welded, made of stamped hemispheres (Fig. 53). The control units used in cranes (BUEP-5; EPUU-6) do not require additional wiring under operating conditions, since they have a built-in terminal box and limit switch. The balloonless design of the drives has significantly reduced the consumption of scarce hydraulic fluid for the crane hydraulic system. In addition, the cranes use manual hydraulic pumps of a fundamentally new design.

Rice. 52. Ball valve KSh without lubrication.

1- body: 2 - ball plug (butterfly valve). 3 - saddle: 4 - spindle; 5 - cover (flanks): b - handle: 7 - sealing gasket: 8. 9 - sealing rubber rings: 10 - bolt: 11 - gasket

The plant produces the following ball valves:

MA39208 - D U 50, 80, 100, 150, 200 mm; RU 80 kgf/cm2; with manual and pneumatic drive

MA39003 - D at 300 mm; r y 80 kgf/cm 2; with manual and pneumatic drive MA39113 - D 400 mm; r y 160 kgf/cm 2 ; with pneumohydraulic drive

MA39I12 - D at 1000 mm; p at 80 and 100 kgf/cm 2

MA39183 - D at 700 and 1400 mm: p at 80 kgf/cm 2

MA39096 - DN 1200 mm; RU 80 kgf/cm 2

MA39095 - D at 1400 mm; r y 80 kgf/cm 2

MA39230 - D at 50. 80. 100. 150. 200 mm; p y 200 kgf/cm 2

Ball valves MA39208 with manual control D y - 50, 80, 100, 150 mm; r y 80 kgf/cm 2 are intended for use as a shut-off device on pipelines transporting natural gas (Table 20). The design of the cranes contains a large number of original devices. The valve assembly D y 50, 80. 100. 150 mm consists of two compact stamped half-bodies with one connector; the presence of one connector reduces the likelihood of depressurization of the valve assembly relative to the external environment. The central connector is sealed with a specially shaped rubber seal.

The design of the shut-off body is made according to the “plug in supports” scheme, with self-lubricating sliding bearings made of metal fluoroplastic. The valve seal is made of polyurethane, which

Rice. 53. Ball valve with pneumatic-hydraulic actuator.

1- valve body: 2 - manual gearbox: 3 - flywheel; 4 - column pipe. 5 - extension; 6 - Column: 7 - pipeline for supplying sealant to the seal: 8 - hydraulic drive: 9 - oil cylinders

Table 20 - Overall, connecting dimensions, mm, and weight of ball valves

0,	p	ABOUT	D 1	A		L	WITH	N	H,	Weight, kg
with pneumohydraulic drive	with manual drive
	80- 160	190- 205					2155 (360)			580 (470)
							2215 (440)			820 (650)
	80- 125		386-398				2420 (625)	2815 (1020)	-	1475- 1480	-
							2530 (935)	3670 (2055)	3570 (1975)	4000 (3600)	3800 (3400)
							2610 (1015)	3970 (2375)	-	5560 (5110)	-
	80- 100		978- 988				2480 (1180)	4010 (2770)	-	10815 (10020)	-
									-		-
									-		-

Note. Dimensions and weight in brackets - for overhead cranes

pressed into a metal seat. Soft polyurethane valve seals are highly wear-resistant, abrasion-resistant, erosion-resistant and provide reliable valve sealing in all pressure ranges. The seats are pressed against the valve due to the pressure of the transported medium and the force of the springs, which serve to ensure reliable tightness of the valve at low pressures. The taps are manufactured with a manual drive, which is a lever. Below is the technical specification of the crane.

A camera's aperture is one of three factors that affects exposure. Therefore, understanding the action of the aperture is a prerequisite in order to take deep and expressive, correctly exposed photographs. There are both positives and negatives to using different apertures, and this tutorial will teach you what they are and when to use which one.

Step 1 - What is a camera's aperture?

The best way to understand what aperture is is to think of it as the pupil of the eye. The wider the pupil is, the more light enters the retina.

Exposure is made up of three parameters: aperture, shutter speed and ISO. The diameter of the aperture regulates the amount of light entering the sensor, depending on the situation. There are various creative uses for apertures, but when it comes to light, it's important to remember that wider openings let in more light, while narrower openings let in less.

Step 2 - How is aperture determined and changed?

The aperture is determined using the so-called aperture scale. You can see the F/number on your camera's display. The number indicates how wide the aperture is, which in turn determines the exposure and depth of field. The lower the number, the wider the hole. This may cause confusion at first - why does a low number correspond to a higher aperture ratio? The answer is simple and lies in the plane of mathematics, but first you must know what the aperture range or standard aperture scale is.

Aperture row:f/1.4,f/2,f/2.8,f/4,f/5.6,f/8,f/11,f/16,f/22

The main thing you need to know about these numbers is that between these values ​​there is one exposure stop, that is, when moving from a lower value to a higher one, half as much light will enter the lens. Modern cameras also have intermediate aperture values ​​that allow you to more accurately adjust the exposure. The tuning step in this case is ½ or 1/3 step. For example, between f/2.8 and f/4 there will be f/3.2 and f/3.5.

Now about more difficult things. More precisely, why the amount of light between the main aperture values ​​differs by a factor of two.

This comes from mathematical formulas. For example, we have a 50 mm lens with an aperture of 2. To find the aperture diameter, we must divide 50 by 2. The result is 25 mm. The radius will be 12.5 mm. Formula for area S=Pi x R 2.

Here are some examples:

50 mm lens with f/2 = 25 mm aperture. The radius is 12.5 mm. The area according to the formula is 490 mm 2. Now let's do the math for f/2.8 aperture. The diaphragm diameter is 17.9 mm, the radius is 8.95 mm, and the opening area is 251.6 mm 2.

If you divide 490 by 251, you won't get exactly two, but that's only because f-stop numbers are rounded to the first decimal place. In fact, the equality will be exact.

This is what the aperture hole ratios really look like.

Step 3 - How does aperture affect exposure?

As the aperture size changes, the exposure also changes. The wider the aperture, the more strongly the matrix is ​​exposed, the brighter the image is. The best way to demonstrate this is to show a series of photographs where only the aperture is changed and the rest of the parameters are constant.

All images below were taken at ISO 200, shutter speed 1/400 sec, no flash, and only the aperture was changed. Aperture values: f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22.

However, the main property of the aperture is not to control exposure, but to change the depth of field.

Step 4 - Depth of Field Effect

Depth of field is a broad topic in itself. It takes several dozen pages to cover it, but now we will look at it very briefly. We are talking about the distance that will be transmitted sharply in front and behind the subject.

All you really need to know, in terms of the relationship between aperture and depth of field, is that the wider the aperture (f/1.4), the shallower the depth of field, and the narrower the aperture (f/22), the larger the field of field. Before I show you a selection of photos taken at different apertures, take a look at the chart below. It helps to understand why this happens. If you don't understand exactly how it works, that's okay, as long as it's important for you to know about the effect itself.

The bottom picture shows a photo taken at f/1.4 aperture. It clearly shows the effect of depth of field (depth of field)

Finally a selection of photos taken in aperture priority, so the exposure remains constant and only the aperture changes. The aperture row is the same as in the previous slideshow. Notice how the depth of field changes as you change the aperture.

Step 5 - How to use different apertures?

The first thing to remember is that there are no rules in photography, there are guidelines, including when it comes to choosing aperture. It all depends on whether you want to use an artistic technique or capture the scene as accurately as possible. To make it easier to make a decision, I present several of the most traditionally used aperture values.

f/1.4: Excellent for low light shooting, but be careful, this setting has very little depth of field. Best used for small subjects or to create a soft focus effect

f/2: The use is the same, but a lens with this aperture may cost one third of a lens with an aperture of 1.4

f/2.8: Also good to use in low light conditions. It is best used for shooting portraits, since the depth of field is greater and the entire face will be included in it, not just the eyes. Good zoom lenses usually have this aperture value.

f/4: This is the minimum aperture used to photograph a person in sufficient light. The aperture can limit autofocus performance, so you run the risk of missing shots wide open.

f/5.6: Good for photography of 2 people, but for low light it is better to use flash light.

f/8: Used for large groups as it ensures sufficient depth of field.

f/11: Most lenses are sharpest at this setting, so it's good for portraits

f/16: Good value when shooting in bright sunlight. Large depth of field.

f/22: Suitable for landscape photography where attention to detail in the foreground is not required.

Pumps K 20/18a create pressure in 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.

Table 9. Calculation of diaphragm hole diameters
Floor number		The amount of excess pressure at the PC and connections, Нср, m				Diaphragm hole diameter, mm
Household drinking water supply
		5 - 2,35 = 2,65
Household fire water supply
Hot water supply

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.

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Course work

in the course “Technical measurements and instruments”

“Calculation of standard narrowing devices”

• 1. Assignment for a course project
• 2. Calculation of standard aperture
• 2.1 Theoretical part
• 2.2 Calculation procedure
• 2.3 Calculation part
• Conclusions on course work
• Bibliography

1. Assignment for a course project

The standard aperture is calculated using the following data.

Medium being measured: steam.

Highest measurable mass flow.

Lowest measurable mass flow.

Absolute steam pressure before the control unit.

Steam temperature before the control unit.

The greatest pressure drop across the control unit.

Inner diameter of the pipeline at a temperature of 20 o C.

The length of straight sections of the pipeline before and after the control unit.

Radius of the leading edge of the control unit.

Steel grade SU: 08Х22Н6Т.

Pipeline steel grade: 20L.

Pressure selection method: flange.

Condition of the inner wall of the pipeline: new.

Permissible calculation error.

2. Calculation of standard aperture

2.1 Theoretical part

Flow is one of the most important technological parameters in thermal and nuclear power plants. Accurate flow measurement is necessary to ensure the required quality of process control, maintain reliable and trouble-free operation of equipment, and calculate technical and economic performance indicators of an energy enterprise.

The method of measuring flow using a variable pressure difference on a restriction device (SU) is one of the most common and well-studied. The advantages of this method include the comparative simplicity of the design and the compactness of the primary flow transducers.

Among the orifice devices of various designs (diaphragms, nozzles, pipes and Venturi nozzles), diaphragms are most widespread. Their main advantages are the ease of manufacture and installation, as well as the possibility of using them to measure the flow rate of a substance in a wide range of flow rates in pipelines with a diameter of 0.05 to 1 m.

In this course project, a standard diaphragm with a flange method of selecting pressure through annular chambers was calculated.

nuclear power plant constriction diaphragm

Fig.1. Standard aperture.

1 - input end of the diaphragm; 2 - output end of the diaphragm.

2.2 Calculation procedure

1. Based on the given parameters of the measured medium (temperature t and pressure p), density, dynamic viscosity and adiabatic index k are found.

2. Based on the given temperature of the measured medium, the temperature expansion coefficients of the pipeline and diaphragm material are found using the formula adj. 2:

,

,

Where

4. Determine the value of the equivalent roughness of the pipeline surface and the arithmetic mean deviation of the roughness profile according to the appendix table. 3.

5. Calculate the upper and lower limits of the working range of Reynolds number values:

;

,

6. Calculate the value of the auxiliary quantity A:

,

7. The values ​​of the lower and upper limits of the range of change relative to the diameter of the restriction device are set.

8. Determine the values ​​of the expansion coefficients of the measured medium (at) and (at) by the expression:

,

9. Calculate the values ​​of the entry speed coefficients (at) and (at) using the formula:

.

10. Calculate the values ​​of the outflow coefficients (at Re=Re max and) and (at Re=Re max and) using the formula app. 4

Where, .

Values ​​and accept

- for the angular method of pressure selection;

, - for the three-radius method of pressure selection.

11. Determine the values ​​of the roughness coefficients of the inner surface of the pipeline (at Re=Re max and) and (at Re=Re max and) according to the formulas of App. 5

If the value of the standard deviation of the pipeline roughness profile satisfies the condition

, That.

Values ​​are calculated using the formula

The values ​​of the coefficients A 0 , A 1 and A 2 are determined by the formula

where are constant coefficients, the values ​​of which are given in

table P5.1.

If

, That.

The value is calculated using the formula

If or then.

If or, then the correction factor is calculated using the expression

Coefficients and are calculated using the formula

,

where, and are coefficients whose values ​​are given

in table P 5.2.

12. Determine the values ​​of the diameter of the orifice of the restriction device (at) and (at using the formula.

13. Determine the values ​​of the blunting coefficients of the input edge of the tapering device (at and (at.

If the radius of the leading edge, then the dullness coefficient.

If the radius of the leading edge, then the value is calculated by the expression

.

14. Calculate the value of auxiliary quantities using the expressions:

,

.

15. Consider the values ​​of auxiliary quantities and formulas

,

.

If the values ​​have the same sign, then the calculation is stopped, since in the range of acceptable values ​​there is no value that satisfies the original data.

If the quantities have different signs, then the calculation continues.

16. Calculate the value using the formula

.

17. Calculate the value of the auxiliary quantity B:

,

where the calculation of E is carried out similarly to paragraph 9, - similar to paragraph 13, C and in accordance with paragraphs 10 and 11 at, and the value in accordance with paragraph 8 at, and.

18. Check the fulfillment of the inequality.

If the above inequality is not satisfied, then repeat points 16 - 18, replacing in the formula of point 16 and with and (for B A).

If the above inequality is satisfied, then the found values ​​are considered final.

19. Check the fulfillment of the condition

.

20. Determine the diameter of the hole under operating conditions d using the expression from paragraph 12.

21. Calculate the diameter of the hole of the narrowing device when

temperature 20:

.

.

,

where is the highest mass flow rate, kg/s; - permissible calculation error, %.

,

- yield strength of the diaphragm material under operating conditions, Pa

,

,

.

,

where, is the elastic modulus of the diaphragm material, Pa.

The values ​​are found by .

.

27. The remaining diaphragm sizes are selected depending on the type according to ,,,,.

2.3 Calculation part

1. Using the given parameters of the measured medium (temperature t and pressure p), we find the density, dynamic viscosity and adiabatic index k.

Po and Pa:

2. Based on the given temperature of the measured medium, we find the temperature coefficient of expansion of the pipeline material and diaphragm using the formula adj. 2:

,

where t is the temperature of the measured medium, o C; - constant coefficients, the values ​​of which are given in table. P2.1.

Because the steam temperature in front of the SU is 415 o C, and the temperature measurement limits for the SU 08Х22Н6Т material are from -40 о С to 300 о С, then I choose another SU material - 08Х18Н10Т.

Temperature expansion coefficients of pipeline material

Temperature expansion coefficients of diaphragm material

3. We calculate the value of the internal diameter of the pipeline under operating conditions:

,

where is the diameter of the pipeline at a temperature of 20 °C, m; t - temperature, °C.

m.

4. Determine the value of the equivalent roughness of the pipeline surface and the arithmetic mean deviation of the roughness profile according to the appendix table. 3.

5. Calculate the upper and lower limits of the working range of Reynolds number values:

;

,

where and are the highest and lowest mass flow rates, respectively, kg/s.

6. Calculate the value of the auxiliary quantity A:

,

where is the greatest pressure drop across the restriction device, Pa.

7. We set the values ​​of the lower and upper limits of the range of change relative to the diameter of the restriction device.

;

.

8. We determine the values ​​of the expansion coefficients of the measured medium (at) and (at) by the expression:

,

where is the absolute steam pressure in front of the restriction device, Pa.

At:

.

At:

.

9. We calculate the values ​​of the entry speed coefficients (at) and (at) using the formula

.

At:

.

At:

.

10. Calculate the values ​​of the outflow coefficients (at and) and (at and) using the formula in Appendix 4

Where,

.

- for the flange method of pressure tapping;

When and:

,

,

.

When and:

,

,

.

11. Determine the values ​​of the roughness coefficients of the inner surface of the pipeline (at and) and (at and) using the formulas of Appendix 5

When and:

.

m.

The value is calculated using the formula

Since, then m.

Since, then.

When and:

The value is calculated using the formula

The value is calculated using the formula

, because Re<3·10 6 , то

Since then

12. Determine the values ​​of the diameter of the orifice of the restriction device (at) and (at using the formula

.

At:

m.

At:

m.

13. Determine the values ​​of the blunting coefficients of the input edge of the tapering device (at and (at.

At:

Since then

.

At:

Since then

14. We calculate the value of auxiliary quantities and expressions

15. We consider the values ​​of auxiliary quantities and according to the formulas

.

.

Since the quantities and have different signs, we continue the calculation.

16. Calculate the value using the formula

.

17. Calculate the value of the auxiliary quantity B:

Let's calculate the value of the entry speed coefficient

.

Let's calculate the value of the expiration coefficient

When and:

.

.

Let us determine the value of the roughness coefficient of the internal surface of the pipeline

When and:

The value is calculated using the formula

.

Because

>15, then.

The value is calculated using the formula

,

Because.

Since, then.

Let us determine the value of the blunting coefficient of the input edge of the tapering device

At m.

Since then

.

Let us determine the value of the expansion coefficient of the measured medium

At:

.

18. Checking the inequality

,

.

Since the above inequality is not satisfied, we repeat points 16 - 18, replacing in the formula of point 16 and with and (for B A). We summarize all subsequent iterations in a table.

	1 experience	2 experience	3 experience	4 experience	5 experience	6 experience	7 experience
	8 experience	9 experience	10 experience	11 experience	12 experience	13 experience	14 experience	15 experience

Since the above inequality holds (0.0000346<0.00005), то найденные значения считают окончательными.

19. Checking the fulfillment of the condition

.

Since for diaphragms with a flanged pressure tap

,

.

The condition is met.

20. Determine the diameter of the hole under operating conditions d using the expression from point 12:

m.

21. Calculate the diameter of the hole of the restriction device at a temperature of 20:

m.

22. Calculate the value of the mass flow corresponding to the largest pressure drop across the restriction device:

.

23. Check the fulfillment of the condition

,

,

.

The condition is met.

24. Select the thickness of the diaphragm disk using the formulas adj. 6

MPa, E y =1.623·10 11 Pa.

The maximum value of the disk thickness must satisfy the condition

,

where is the diameter of the pipeline opening under operating conditions, m.

m.

.

.

The values ​​of quantities and are found by expressions

,

.

The values ​​of the coefficients and included in the formula are found using the expressions

.

The minimum disc thickness must satisfy the following conditions

;

,

where is the greatest pressure drop across the restriction device, Pa;

- yield strength of the diaphragm material under operating conditions,

- relative diameter of the diaphragm.

Accepted mm.

25. Select the length of the cylindrical part of the diaphragm hole e within

.

.

Accepted mm.

26. The angle of inclination of the cone generatrix to the axis of the diaphragm opening is selected within the limits.

Accepted

27. Other diaphragm sizes are selected depending on the type.

For diaphragms with a flanged pressure tap, the location of the holes is shown in Figure b. Distance l 1 is measured from the input end of the diaphragm, and the distance l"2 - from the output end of the diaphragm.

Values l 1 and l" 2 can be within the following limits:

(25.4 ± 0.5) mm at β > 0.6 and D< 0,15 м;

(25.4 ± 1) mm in other cases.

l 1 =26.4 mm, l" 2 =26.4 mm.

The centerline of the hole must intersect with the centerline of the IT at an angle of 90° ± 3°.

The edges of the opening where the IT exits should be flush with the internal surface of the IT and as sharp as possible. To eliminate burrs on the inner edge of the hole, it is allowed to blunt it with a radius of no more than one tenth of the hole diameter. Any irregularities on the inner surface of the hole and on the IT itself near the hole are not allowed.

The diameter of the holes should be no more than 0.13 D and no more than 13 mm. I took the hole diameters to be 10 mm.

When choosing the diameter of the hole, it is necessary to exclude the possibility of clogging.

The surface of the inlet end of the diaphragm (see Figure 1) must be flat. The non-flatness of the surface of the inlet end of the diaphragm is determined before its installation.

The slope, characterized by the ratio N D /l D, must satisfy the condition:

If l = D, That

2H D /( D - d) < 0,005.

Table 1 (GOST 8.586.2-2005) shows the highest permissible values ​​of H D depending on D and at l = D.

At b=0.3405 and D=0.35213 m, N D max =0.58109·10 -3 m.

Let's take N D = 0.55 10 -3 m, l D = 0.116115 m.

Conclusions on course work

During the course work, a standard diaphragm with a flange method of pressure selection was calculated.

The calculation of a standard diaphragm is based on solving the flow equation and consists in determining the relative diameter of the hole in an iterative manner.

At the first stage, the relative diameter was determined iteratively and the value of the mass flow rate kg/s was calculated.

At the second stage, the necessary dimensions for the manufacture of a standard diaphragm m, m, were calculated.

At the third stage, a drawing was made based on the found dimensions.

Bibliography

1. Kochetkov A.E., Malkova E.L. Calculation of a standard diaphragm: methodological instructions / Ivan. state energy univ. - Ivanovo, 2014.

2. GOST 8.586.2-2005 State system for ensuring the uniformity of measurements. Measurement of flow and quantity of liquids and gases using standard restriction devices. Part 2. Diaphragms. Technical requirements. - M.: Standartinform, 2006. - 43 p.

3. GOST 8.586.1-2005 State system for ensuring the uniformity of measurements. Measurement of flow and quantity of liquids and gases using standard restriction devices. Part 5. Methodology for performing measurements. - M.: Standartinform, 2006. - 87 p.

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course work, added 06/17/2011


Analysis of a technological object as an object of automation. Selection of sensors for measuring temperature, pressure, flow, level. Linking process parameters to analog and discrete input modules. Calculation of the main parameters of the regulator settings.

thesis, added 09/04/2013


Heat supply project for an industrial building in Murmansk. Determination of heat flows; calculation of heat supply and network water consumption. Hydraulic calculation of heating networks, selection of pumps. Thermal calculation of pipelines; boiler room technical equipment.

course work, added 11/06/2012


Modern requirements for instruments for measuring liquid flow. Chamber flow transducers without moving separating elements. Diagram of a gear counter with oval gears. Chamber flow transducer with elastic walls.

Purpose of the product

The diaphragm for fire hydrants DU65 is used to limit the pressure between the fire hydrant itself and the connecting head.

According to an excerpt from SNiP 2.04.01-85*“Internal water supply and sewerage of buildings” when pressures at fire hydrants are more than 40 m between the fire hydrant and the connecting head, it is necessary to install diaphragms that reduce excess pressure. It is allowed to install diaphragms with the same hole diameter on 3-4 floors of a building.

The diaphragm for fire hydrants DU65 is made of stainless steel, in accordance with the current GOST, 3 mm thick . It is a washer with a hole in the center. Depending on the pressure in the pipeline, diaphragms with holes of different diameters are used. The diaphragm is used in cases where it is necessary to reduce the pressure on fire hoses. The diaphragm is installed at the outlet of the fire hydrant directly between the valve and the connection head. The diaphragm is used to reduce excess pressure in fire water supply systems. By installing diaphragms to reduce excess pressure, the water pressure at fire hydrants on all floors of the building is regulated. Thus, in the event of a fire, with the simultaneous opening of fire hydrants on different floors, the water pressure will be the same everywhere.

It is advisable to use a diaphragm with a sleeve length of more than 40 meters. The internal diameter of the hole is made from 10 mm to 40 mm in increments of 0.5 mm.

If the connecting head at the outlet is a coupling head GM65, then the diaphragm is placed inside the head, the head is screwed onto the tap and clamps the diaphragm:

If the connecting head at the outlet is a pin-type GC65, then the diaphragm is placed inside the head and secured with a retaining ring, after which the head is screwed into the tap:

Determining the required aperture diameter

Diaphragms differ:

• internal diameter of the hole;
• outer diameter.

The internal diameter of the diaphragm for a fire hydrant is determined according to SNiP 2.04.01-85* “Internal water supply and sewerage of buildings” according to the nomogram:

1) Place point 1 on the Hsr axis (number of meters of excess pressure);

2) Place point 2 on the q-axis, l/s (scale of the required water pressure);

3) Draw a line from point 1 to point 2;

4) Find the point of intersection of the line with the central axis, the value in mm will be the diameter of the internal hole of the diaphragm:

• If the diaphragm is for a DN50 fire hydrant, take the value on the left side of the central axis (rounded to 0.5 mm increments).
• If the diaphragm is for a fire hydrant DU65, we take the value on the right side of the central axis (rounded to 0.5 mm increments).

The outer diameter of the diaphragm depends on two factors :

1) The diaphragm goes under a fire hydrant DN50 or DN65.

2) The outlet of the fire hydrant has an internal or external thread, i.e. the connecting head at the output will be pin-type (GC) or coupling head (GM), respectively.

If the fire hydrant outlet has an external thread, i.e. The connection head at the outlet will be a coupling head GM50/GM65, there will be the following options:

• For DN50 taps, the outer diameter of the diaphragm will be 56 mm.
• For DU65 taps, the outer diameter of the diaphragm will be 72 mm.

If the fire hydrant outlet has an internal thread, i.e. The connecting head at the output will be a pin head GC50/GC65, then the outer diameter of the diaphragm is determined by the internal diameter of the pin head GC:

• For DU50 taps, the outer diameter of the diaphragm will be from 43 mm to 48 mm.
• For DU65 taps, the outer diameter of the diaphragm will be from 63 mm to 68 mm.

* This diameter varies depending on the manufacturer. To avoid mistakes, be sure to measure the diameter of your nut.

The ALARM 01 company will produce:

• any internal diameter of the diaphragm at the request of the customer, depending on the required pressure;
• any external diameter of the diaphragm.