Selecting the pressure gauge scale.

Need to know:

1 Instrument scales according to GOST

2 Requirements of the rules for pressure gauges (the optimal reading of the pressure gauge if the needle of the device at operating pressure is at 2/3 of the scale).

To solve the problem we have the formula Rshk=3/2Rrab.

For example: Given: Prab=36kgf/cm2. Determine Rshk?

Solution: Rshk = 3 36/2 = 54 kgf/cm 2.

We select the nearest scale according to GOST in the upward direction. This is 60 kgf/cm 2

Thus: Rshk=60

5. Indirect cardiac massage.

Ticket number 4

1. Basic properties of rocks

A reservoir is a rock that has geological and physical properties that ensure the physical mobility of oil or gas in its void space. The vast majority of oil and gas fields are confined to reservoirs three types– granular, cracked and mixed structure. The first type includes reservoirs composed of sandy-silty rocks, the pore space of which consists of intergranular cavities. Some layers of limestone and dolomite are also characterized by a similar structure of the pore space. In purely fractured reservoirs (composed predominantly of carbonates), the pore space is formed by a system of fractures. In this case, the reservoir sections between the fractures are dense, low-permeability, non-fractured blocks of rock, the pore space of which practically does not participate in filtration processes. In practice, however, most often there are mixed-type fractured reservoirs, the pore space of which includes both systems of fractures and the pore space of blocks, as well as caverns and karst.

The analysis shows that about 60% of the world's oil reserves are confined to sand formations and sandstones, 39% to carbonate sediments, 1% to weathered metamorphic and igneous rocks. Consequently, rocks of sedimentary origin are the main reservoirs of oil and gas.

Due to the diversity of sediment formation conditions, the reservoir properties of layers of different fields can vary within wide limits. The characteristic features of most reservoirs are their layered structure and changes in rock properties, layer thickness and other parameters in all directions.

An oil or gas reservoir is a rock saturated with oil, gas and water.

Rock is understood as a natural solid mineral aggregate of a certain composition and structure, forming bodies of various shapes and sizes in the earth's crust. Rocks are divided into three groups: sedimentary, igneous (igneous) and metamorphic. Sedimentary rocks arise as a result of the transformation under thermal conditions of the surface part of the earth's crust of sediments, which are products of the destruction of older rocks, erupted volcanoes, and the vital activity of organisms and plants that have fallen mechanically or chemically.

The properties of a rock to accommodate (due to the porosity of the rock) and to pass (due to permeability) liquids and gases through itself are called filtration-capacitive properties (FEC).

Filtration and reservoir properties of oil reservoir rocks are characterized by the following main indicators:

· granulometric composition of rocks

· porosity;

· permeability;

· saturation of rocks with water, oil and gas;

· specific surface area;

· capillary properties;

· mechanical properties.

2. Purpose of direction, conductor, technical and production tubing strings

In a well construction project, developing its design is a very important section. The reliability of the structure depends on correct consideration of the nature of loading, operating conditions and wear of columns during the life of the well. At the same time, the selected design determines the volume of work in the well and the consumption of materials and therefore significantly affects the cost indicators of construction and operation of the well.

The development of a well design begins with solving two problems: determining the required number of casing strings and the depth of descent of each of them; justification by calculation of the nominal diameters of casing strings and diameters of rock-cutting tools.

The number of casing strings is determined based on an analysis of the geological section at the location of the well, the presence of zones where drilling is associated with major complications, an analysis of the pattern of changes in reservoir pressure anomaly coefficients and absorption indices, as well as accumulated practical experience well drilling. The results of studying a specific geological situation allow us to draw conclusions about the incompatibility of drilling conditions and, on this basis, identify individual intervals that are subject to isolation. Based on the available data, a graph of changes in the anomaly coefficient of reservoir pressure ka and absorption pressure index kп is plotted with depth, and intervals are identified on it that can be passed using a solution of the same density.

Rice. 3.1. Casing pipe in the well Fig. 3.2. Well casing diagram

The running depth of each casing string is specified so that its lower end is located in the interval of stable monolithic low-permeable rocks and that it completely covers the intervals of weak rocks in which hydraulic fracturing can occur when opening zones with abnormally high reservoir pressure (AHRP) in the underlying interval.

Thus, as a result of drilling a shaft, its subsequent fastening and isolation of layers, a stable underground structure of a certain design is created.

Well design is understood as a set of data on the number and dimensions (diameter and length) of casing strings, wellbore diameters for each string, cementing intervals, as well as methods and intervals for connecting the well to the productive formation.

Information about the diameters, wall thicknesses and steel grades of casing pipes at intervals, about the types of casing pipes, and equipment at the bottom of the casing string are included in the concept of casing string design.

Casing strings for a specific purpose are lowered into the well: direction, casing, intermediate columns, production casing.

The direction is lowered into the well to prevent erosion and collapse of rocks around the mouth when drilling under the conductor, as well as to connect the well to the drilling fluid cleaning system. The annular space behind the direction is filled along the entire length with cement mortar or concrete. The direction goes down to a depth of several meters in stable rocks, to tens of meters in swamps and muddy soils.

The conductor usually covers the upper part of the geological section, where there are unstable rocks, layers that absorb drilling fluid or produce formation fluids that supply the surface, i.e. all those intervals that will complicate the process of further drilling and cause pollution of the environment. The conductor must cover all layers saturated with fresh water.

Rice. Well design diagram

The conductor also serves for installation of blowout prevention equipment and suspension of subsequent casing strings. The conductor is lowered to a depth of several hundred meters. To ensure reliable separation of layers and impart sufficient strength and stability, the conductor is cemented along its entire length.

Intermediate (technical) columns must be lowered if it is impossible to drill to the designed depth without first isolating the zones of complications (shows, collapses). The decision to lower them is made after analyzing the pressure ratio that occurs during drilling in the well-reservoir system.

The production string is lowered into the well to extract oil, gas or inject water or gas into the productive horizon in order to maintain reservoir pressure. The height of the rise of the cement slurry above the roof of productive horizons, as well as the stage cementing device or the connection unit for the upper sections of casing strings in oil and gas wells should be at least 150-300 m and 500 m, respectively.

In some cases, when the available geological information is insufficient to justify the number of columns and the designers have serious concerns that unforeseen complications may arise in the well, a reserve column may be provided in the design of the first exploration and exploration wells.

Having determined the number of casing strings and the depth of their descent, they begin to coordinate by calculation the normalized diameters of the casing strings and the rock-cutting tool. The starting point for the calculation is either the diameter of the production string, which is set depending on the expected flow rate of the well, or the final diameter of the well, determined by the size of the tools and devices that will be used in the well.

Based on the calculated value of the internal diameter in accordance with the dimensions specified in GOST 632, the normalized diameter of the casing is selected. The calculation is repeated in a similar way for each subsequent column up to the top one.

If the well is completed without running the casing to the final depth, the initial bit diameter for the final interval is used.

3. Reception and delivery of the watch by the operator

4. Instruments for measuring pressure, types, accuracy class, measurement range.

The text uses the term “pressure gauge”; the name pressure gauge is a general one. This concept also includes vacuum gauges and pressure and vacuum gauges. This material is not related to digital devices.
Pressure gauges are devices that are widely used in industry and housing and communal services. At enterprises in the production process there is a need to control the pressure of liquids, steam and gas. Depending on the specialization of the enterprise, there is a need to measure various media. Pressure gauges have been developed for this purpose. for various purposes. The difference between devices is determined by the medium being measured and the conditions under which the measurement is made. Pressure gauges differ in design, size, connection thread, units of measurement and possible measurement range, accuracy class, as well as material of manufacture, which determines the possibility of using the device in aggressive environments. Choosing a device that does not correspond to the tasks performed entails failure of the device before its expected service life, errors in measurement results, or overpayment for unused functions of the device.

Classification of pressure gauges depending on criteria

Depending on the application.

Standard technical pressure gauges are used to determine excess and vacuum pressure of non-aggressive, non-crystallizing media: liquids, steam and gas.

Technical special - this type of pressure gauges is used to measure specific media (for example, aggressive) or under special conditions (increased vibration or temperature, etc.).

Special devices:

Ammonia and corrosion resistant pressure gauges in their design they have parts and mechanisms made of stainless steel and alloys that are resistant to aggressive environments, as a result of which this type of device can be used for work where interaction with an aggressive environment is provided.

Vibration-resistant pressure gauges can be used under conditions of exposure to vibration that is 4-5 times higher than the vibration frequency permissible for the operation of a conventional pressure gauge.
The main distinguishing feature of vibration-resistant pressure gauges is the presence of a special damping device, which is located in front of the pressure gauge. This device helps reduce pressure pulsation.
Some types of vibration-resistant pressure gauges can be filled with damping fluid. Vibration resistance is achieved thanks to a vibration-absorbing substance, which is glycerin.

Pressure gauges for precise measurements used in government sectors. merthological control, in heat supply, water supply, energy, mechanical engineering, etc. In addition, they are used as a standard for verification and calibration of pressure measuring instruments in compliance with the requirements for compliance with the accuracy classes of the device used as a sample and the device being verified.

Railway pressure gauges used for measuring excess vacuum pressure of media that are non-aggressive towards copper alloys in systems and installations of rolling stock and for measuring the pressure of freons in refrigeration machines in refrigerator cars.
The pressure gauge housings are painted in appropriate colors depending on the application. Ammonia - yellow, for hydrogen - dark green, for combustible flammable gases - red, for oxygen - blue, for non-flammable gases - black.

Electric contact pressure gauges. The peculiarity of electric contact pressure gauges is that they are devices with an electric contact group. Designed to measure the pressure of non-aggressive, non-crystallizing media (steam, gas, including oxygen), as well as short circuit and open circuit electrical circuits when a certain pressure limit is reached. The electric contact mechanism allows for adjustment of the variable environment.
Possible design options for contact groups of electric contact pressure gauges, according to GOST 2405-88:
III – two normally open contacts: left pointer of blue color(min), right red color (max);
IV – two normally open contacts: the left indicator is red (min), the right indicator is blue (max);
V – left normally open contact (min); right normally open contact (max) – color of indicators – blue;
VI – left normally open contact (min); right NC contact (max) – color of indicators – red.
Option V is mainly accepted by enterprises as standard. If the type of execution is not specified, as a rule, it will be option V. In any case, you can identify the type of contact group depending on the color of the indicators.
Depending on the purpose and area of ​​application, electrical contact (signaling) pressure gauges are either general industrial or explosion-proof.
The type of explosion-proof device (its explosion protection level) must correspond to the conditions of increased danger of the facility.

Pressure units. Graduation of pressure gauge scales.

Pressure gauge scales are calibrated in one of the following units: kgf/cm2, bar, kPa, MPa, provided that the device has one scale. For pressure gauges with a double scale, the first is graduated in the above units of measurement, the second in psi - pound-force per square inch. Psi is a non-systemic unit used in the USA.
In table Figure 1 shows the relationship of units of measurement relative to each other.

Table 1. Ratio of pressure units.

Type of pressure gauges with a scale in units of kPa are instruments designed to measure low pressures substances in a gaseous state. In their design, a membrane box serves as a sensitive element. In contrast, pressure gauges for measuring high pressure have a sensing element - a curved or spiral tube.

Range of measured pressures.

There are the following types of pressure: absolute, barometric, excess, vacuum.
Absolute – pressure value measured relative to absolute vacuum. The indicator cannot be negative.
Barometric – atmospheric pressure. It is affected by altitude, humidity and air temperature. At zero altitude above sea level, the barometric pressure is taken to be 760 mmHg.
For technical pressure gauges, this value is assumed to be zero. This means that the measurement results do not depend on the barometric pressure.
Excess pressure is a value indicating the difference between absolute and barometric pressure. This is relevant when the absolute pressure exceeds the barometric pressure.
Vacuum is a value showing the difference between absolute and barometric pressure, in conditions where barometric pressure exceeds absolute pressure. Therefore, vacuum pressure cannot be higher than barometric pressure.
Based on the above, it becomes obvious that vacuum gauges measure vacuum. Pressure and vacuum gauges cover the vacuum region and overpressure.
The function of pressure gauges is to determine excess pressure.
As a result of standardization of the ranges of measured pressures, they were accepted to correspond to a certain range of values ​​(Table 2).
Table 2. Standard range of values ​​for calibration of scales.

Accuracy class of pressure gauges.

The accuracy class of a device means the permissible error, which is expressed as a percentage of the maximum value of the pressure gauge scale. The lower the error, the higher the accuracy of the device. The accuracy class is indicated on the instrument scale. Pressure gauges of the same type can be with different class accuracy.

Diameter of the pressure gauge body.

The most common diameters of pressure gauge housings are 40, 50, 60, 63, 100, 150, 160, 250 mm. But there are devices with other body sizes. For example, vibration-resistant pressure gauges produced by UAM, type D8008-V-U2, an analogue of DA8008-Vuf produced by Fiztekh, have a diameter of 110 mm.

Construction of pressure gauges.

A fitting is used to connect the device to the system. The location of the fitting can be of two types - radial (bottom) and axial (rear). The location of the axial fitting can be central or offset relative to the center. The design of many types of pressure gauges provides exclusively for a radial fitting. For example, electric contact pressure gauges.
The thread size of the fitting corresponds to the diameter of the body. Pressure gauges with diameters of 40, 50, 60, 63 mm have threads M10x1.0-6g, M12x1.5-8g, G1/8-B, R1/8, G1/4-B, R1/4. Pressure gauges with a larger diameter are made with M20x1.5-8g or G1/2-B thread. European standards apply, in addition to the above-mentioned thread types, conical threads - 1/8 NPT, 1/4 NPT, 1/2 NPT. In industrial conditions, depending on the tasks and types of measured media, specific connections are used. Pressure gauges operating with high and ultra-high pressure levels are characterized by internal conical threads or a cylindrical thread option.
Depending on the type of equipment, when ordering the device, you should indicate the required type of thread. This will help avoid additional unforeseen costs that would entail replacing installation fittings.
The design of the pressure gauge body is also selected according to the installation method and location. For open highways, the design of the devices does not provide additional fastenings. For devices installed in cabinets or control panels, a front and rear flange is required.

Depending on the design, the following types are distinguished:

• with radial fitting without flange;
• with radial fitting with rear flange;
• with axial fitting with front flange;
• with axial fitting, no flange.

The standard level of protection for pressure gauges is IP40. Special pressure gauges, according to the conditions of their use, are manufactured with degrees of protection IP50, IP53, IP54 and IP65.
In order to prevent unauthorized opening of the pressure gauge, the device must be sealed. To do this, an eye is made on the body, equipped with a screw with a hole in the head for installing a seal.

Protection against high temperatures and pressure changes.
The measurement error of the pressure gauge depends on the influence of temperature environment and temperature of the measured medium.
For most devices, the temperature measurement range is no more than +60°C, maximum +80°C. Devices from some manufacturers have the ability to measure pressure at high temperatures of the measured medium up to +150°C, or even 300°C.
For standard pressure gauges, operation in such conditions is only possible if there is a siphon outlet (cooler) through which the pressure gauge is connected to the system.
This is a special tube, of a special shape, at the ends of which there is a thread for connecting to the main line and connecting a pressure gauge. The siphon outlet creates a branch in which the measured medium does not circulate. Due to this, the temperature at the connection point of the device is much lower than in the main line.

In addition, the durability of the pressure gauge is affected by sudden changes in measured pressure and water hammer. In order to reduce the influence of these factors, damping devices are used. The damper is installed in front of the device as a separate device, or mounted in the channel of the pressure gauge holder.
If there is no need to constantly monitor the pressure in the system, you can install a pressure gauge through a push-button valve. This allows you to connect the device to the main line only for the duration of pressing the tap button. This will protect the device without the need for a damper device.

Each vessel and independent cavities with different pressures must be equipped with direct-acting pressure gauges. The pressure gauge is installed on the vessel fitting or pipeline between the vessel and the shut-off valve.

Pressure gauges must have an accuracy class of at least:

2.5 - at a vessel operating pressure of up to 2.5 MPa (25 kgf/cm 2);

1.5 - when the operating pressure of the vessel is above 2.5 MPa.

The pressure gauge must be selected with a scale such that the limit for measuring working pressure is in the second third of the scale.

The owner of the vessel must mark the pressure gauge scale with a red line indicating the operating pressure in the vessel. Instead of the red line, it is allowed to attach a pressure gauge to the body metal plate, painted red and tightly adjacent to the glass of the pressure gauge.

The pressure gauge must be installed so that its readings are clearly visible to operating personnel.

The nominal diameter of the body of pressure gauges installed at a height of up to 2 m from the level of the observation platform must be at least 100 mm, at a height of 2 to 3 m - at least 160 mm. Installation of pressure gauges at a height of more than 3 m from the site level is not permitted.

A three-way valve or a device replacing it must be installed between the pressure gauge and the vessel, allowing periodic checking of the pressure gauge using a control valve.

Pressure gauges and pipelines connecting them to the vessel must be protected from freezing.

The pressure gauge is not allowed for use in cases where:

There is no seal or stamp indicating verification;

The verification period has expired;

When it is turned off, the needle does not return to the zero scale reading by an amount exceeding half the permissible error for this device;

The glass is broken or there is damage that may affect the accuracy of its readings.

Checking of pressure gauges with their sealing or branding must be carried out at least once every 12 months. In addition, at least once every 6 months, the owner of the vessel must carry out an additional check of the working pressure gauges with a control pressure gauge and record the results in the control check log.

Lecture 11

Marking, installation, vessel fastening, technical

Documentation

Vessel marking

A label must be attached to each container. For vessels with an outer diameter of less than 325 mm, it is permissible not to install a sign. In this case, all the necessary data must be applied to the vessel body using the electrographic method.

The plate must contain:

Trademark or manufacturer's name;

Name or designation of the vessel;

Serial number of the vessel according to the manufacturer's numbering system;

Year of manufacture;

Working pressure, MPa;

Design pressure, MPa;

Test pressure, MPa;

Permissible maximum and (or) minimum operating wall temperature, °C;

Vessel mass, kg.

For vessels with independent cavities that have different design and test pressures and wall temperatures, these data should be indicated for each cavity.

Pressure units

The basic SI unit of pressure is the pascal (Pa).

« One pascal - this is the pressure on a flat surface under the influence of a force that is directed perpendicularly and uniformly distributed to the surface and is equal to 1 Newton.”

In practice they use kilopa rock (kPa) or megapascal (MPa), since the Pa unit is too small.

The pressure gauges currently in use also use the MKGSS system unit (meter, kilogram-force, second) kilogram-force per square meter () and non-system units of measurement for example kilogram-force per square centimeter ().

Another common unit of measurement is bar (1 bar = 10 Pa = 1.0197 kgf/cm). It is in the bars that the pressure gauges under study are calibrated.

The relationships between pressure units can be calculated using the formula:

P 1 =KЧP 2, (1.4 )

Where P 1 - pressure in the required units; P 2 - pressure in original units.

The values ​​of coefficient K are given in Table 1.1.

Table 1.1.

Pressure gauges. Classification of pressure gauges

GOST 8.271-77 defines a pressure gauge as a device or measuring setup to determine the actual pressure value or pressure difference.

Pressure gauges are classified according to the following characteristics:

• the type of pressure for which the pressure gauge is designed;
• operating principle of the pressure gauge;
• purpose of the pressure gauge;
• pressure gauge accuracy class;
• characteristics of the measured environment;

Classifying pressure gauges according to the type of pressure measured, they can be divided into:

• - measuring absolute pressure;
• - measuring excess pressure;
• - measuring discharged pressure, which are called vacuum gauges;

Most manufactured pressure gauges are designed to measure excess pressure. Their peculiarity is that when atmospheric pressure is applied to the sensitive element, the devices show “zero”.

There are also many variations of instruments, united by the common name “pressure gauge”, for example pressure and vacuum gauges, pressure gauges, draft gauges, draft pressure gauges, difnanometers.

Pressure-vacuum meter- pressure gauge, with the ability to measure both excess pressure and rarefied gas pressure (vacuum).

Pressure meter- a pressure gauge that allows you to measure ultra-low values ​​of excess pressure (up to 40 kPa).

Traction gauge- a vacuum gauge that allows you to measure small values ​​of vacuum pressure (up to -40 kPa).

Diffnanometer- a device designed to measure the difference in pressure at two points.

“According to the principle of operation, pressure gauges are classified into:

• - liquid;
• - deformation;
• - deadweight piston;
• - electric;

TO liquid include pressure gauges, the principle of operation of which is based on the pressure difference between the pressure of a liquid column. An example of such a pressure gauge is U-shaped pressure gauges. They consist of graduated communicating vessels in which the measured pressure can be determined by the level of liquid in one of the vessels.

Rice. 1.1. U-shaped liquid glass pressure-vacuum gauge:

1 -- U-shaped glass tube; 2 -- fastening brackets; 3 -- the basis; 4 -- scale.

Strain gauges are based on the dependence of the degree of deformation of the sensing element on the pressure applied to this element. Basically, a tubular spring acts as a sensing element. We will learn more about them later.

Electrical pressure gauges operate on the basis of the dependence of the electrical parameters of the sensitive element of the converter on pressure.

IN deadweight pressure gauges a liquid is used as a working fluid, which creates pressure. This pressure is balanced by the mass of the piston and weights.

By the number of loads required for balance, we determine the pressure that the liquid creates.

Rice. 1.2. Schematic diagram deadweight pressure gauge:

1 --oil tank, 2 --pump, 3 --valves, 4, 5, b--inlet, drain and measuring column valves, respectively, 7 --measuring column, 8, 9 -- racks, 10, 11 -- rack valves, 12 --press.

According to their purpose, pressure gauges are divided into general technical and standard. General technical are intended for carrying out measurements during production activities. In general technical ones, vibration resistance to frequencies in the range of 10-55 Hz is structurally provided. Also provide resistance to external influences such as:

• - ingress of external objects;
• - temperature effects;
• - water ingress;

« Reference manometric instruments are designed to store and transmit the size of pressure units to ensure consistency, reliability and guarantee high accuracy of pressure measurements.”

“According to the characteristics of the medium being measured, all pressure gauges are classified into:

• general technical;
• corrosion-resistant (acid-resistant);
• vibration-resistant;
• special;
• oxygen;
• gas."

General technical pressure gauge instruments are designed for measurements under normal conditions. Made from aluminum and copper alloys.

Corrosion resistant devices are made from chemically resistant materials such as steel of various grades. Also supplied with tempered laminated glass.

Special pressure gauges are designed to measure media different from normal conditions, for example for measuring the pressure of viscous substances or containing solid particles.

Vibration resistant Pressure gauges are used in operating conditions where the vibration frequency exceeds 55 Hz. The internal volume of such pressure gauges is filled with a viscous liquid, such as glycerin or silicone. The housing in a vibration-resistant pressure gauge must be sealed and contain special rubber seals.

In gas a number of pressure gauges are used constructive solutions, which should ensure safety in the event of a rupture of the sensitive element. A dividing partition is installed between the scale and the sensitive element. The viewing window in such pressure gauges is multi-layered and reinforced. There is a relief valve on the rear wall, which, if the permissible pressure is exceeded, opens and relieves pressure. During production, special attention is paid to materials because many gases have specific properties.

“Oxygen pressure gauges are used to measure pressure in environments with an oxygen content of 23% or more.” Since when oxygen comes into contact with some organic substances and mineral oils, it detonates, there are strict requirements for cleanliness of oils. Structurally they do not differ from general technical pressure gauges.

Required marks on pressure gauges

The following must be marked on the pressure gauge dial:

• 1) Units of measurement;
• 2) Operating position of the device;
• 3) Accuracy class;
• 4) Name of the measured medium in the case of a special version of the device;

• -trademark of the manufacturer;
• - sign of the State Register;

Table 1.2 shows the main symbols on the dial of pressure gauges.

Table 1.2

Labels indicating resistance to external conditions should also be indicated.

Table 1.3

And the degree of protection from external influences is also indicated.

Pressure gauges. Pressure units

Pressure gauges are designed to measure pressure and vacuum. Pressure gauges installed on GP, ​​TP (pipelines), and devices indicate excess pressure. To obtain absolute pressure, it is necessary to add 1 (atmospheric pressure) in kgf/cm2 to the number of excess pressure measured on the pressure gauge.

Pressure gauges installed in gas supply systems are divided into:

· Liquid;

· Spring;

· Electric contact;

· Pressure and vacuum gauges.

Pressure and vacuum gauges, intended for measuring not only Rizb, but also for measuring rarefaction, i.e. pressure is less than atmospheric.

Liquid pressure gauges. They are designed to measure small pressures.

The zero mark of the scale is in the middle. One end of the tube communicates freely with the atmosphere. The second one is connected to the GP medium being measured through a rubber hose. The tube is filled with water (tinted) to the “0” mark; You can use alcohol, antifreeze, etc., but you need to make an adjustment for density, i.e. reduce its density to the density of water.

To take readings fromU-shaped liquid pressure gauge, it is necessary to add up the decrease in level in one knee with its increase in the other.

Spring pressure gauges. They are designed to measure all pressures. A spring pressure gauge consists of a round box - a housing, in which there is a curved brass tube of oval cross-section. One end of the tube is sealed, and the other is connected through a three-way valve to the medium being measured. The sealed end of the tube (Bourdon) is connected through a lever to a gear sector associated with a gear, on the axis of which there is an arrow.

The pressure gauge has a scale (dial) on which the following data is printed:

1. GOST pressure gauge;

2. Case size (100, 160mm);

3. Date of issue;

4. Pressure gauge accuracy class;

5. Error expressed in %;

6. Pressure gauge scale units (MPa, kgf/cm, bar, KPa, Pa);

7. The pressure measurement limit of this pressure gauge;

8. Type (MTP, OBM, MO, etc.).

Electric contact pressure gauges. This is a variation of the conventional spring pressure gauge. (ECM).

In addition to the black indicating arrow, the ECM has one or more light contact arrows. Voltage is supplied to the ECM through a special device.

ECMs operate in a system of automation, safety and regulation.

ECMs are installed on boiler drums, in front of boiler burners to control pressure, on the burner strictly according to the design.

Pressure gauge malfunctions:

· There is no stamp or government seal.

· The state verification of the pressure gauge is overdue.

· The glass is broken, the body is dented, the glass is dirty.

· There may be gas leaks through a leaky Bourdon tube of the pressure gauge.

· When landing at “0” the needle does not land at the zero mark.

· When checking the working pressure gauge, the readings do not coincide with the control one.

The serviceability and correctness of the pressure gauge readings is checked in the following periods:

1. Once a year - state verification in the laboratory of the state verifier.

2. At least once per shift – landing at “0”.

3. At least once every 2 months - check with a control pressure gauge.

The working position of the pressure gauge needle should be in the second third of the scale.