The pressure measurement error depends on the instrumental errors of the measuring instruments, the operating conditions of the pressure gauges, the methods of taking pressure and transmitting it to the instruments. When choosing the measurement limits of the manometer, they are guided by the values of the measured pressure and the nature of its changes. With a stable measured pressure, its value should be 3/4 of the measuring range of the device, and in the case of variable pressure, 2/3. To eliminate the possibility of the formation of explosive and flammable mixtures, pressure gauges designed to measure the pressure of gases such as oxygen, hydrogen, ammonia are painted in blue, dark green, yellow in accordance with the standard.
Installation rules for pressure gauges at industrial facilities, the selection of pressure and its transmission to the devices using impulse lines are regulated by intradepartmental standards, which are guided by the installation of measuring devices. The main points of these guidelines are discussed below.
Manometers showing and with remote transmission of indications, as a rule, are installed near pressure tapping points in a place convenient for service. The exception is the pressure gauges used for in-reactor control and pressure control in devices located at NPPs in restricted areas. Modern serial pressure transducers cannot be placed inside the core; therefore, they are located at a considerable distance from the pressure tapping points, which leads to an increase in the inertia of the instrument readings. It should be borne in mind that the presence of a liquid column in the impulse line creates a systematic error in readings, which will have a negative or positive sign depending on whether the pressure gauge is above or below the pressure tapping point. The pulse lines of differential pressure gauges are long, the limit value of which is 50 m.
The pressure is taken using pipes connected to the pipeline or the interior of the object where the pressure is measured. In general, the tube should be made flush with the inner wall so that no stagnation of the flow is created at the protruding part. When measuring the pressure or pressure difference of liquid media, it is not recommended to take pressure off the lower and upper points of the pipeline so that sludge and gases do not get into the impulse lines, in case of gaseous media - from the lower points of the pipeline so that condensate does not get into the impulse lines. ...
When measuring pressure and vacuum in gas ducts, air ducts, dust pipelines, it is often necessary to smooth out pressure pulsations and separate suspended particles.
Rice. one. :
1 - cyclone; 2 - dust pipe; 3 - metal wall; 4.5 - tubes; 6 - hole with plug
In fig. 1 shows the installation of cyclone I on the pressure take-off line in the dust pipe 2, which has a metal wall 3. The dust-air mixture is supplied to the cyclone by the pipe 4 tangentially, the pressure to the device from the cyclone is taken from its middle part by the pipe 5. In the cyclone, suspended particles are separated and periodically removed from it through hole 6. To smooth out the pulsations, chokes are installed in front of the measuring device. The length of the lines from the pressure tapping point to the device must provide cooling of the measured medium to the ambient temperature. With the help of switch valves, one pressure gauge or traction gauge can be connected to several pressure or vacuum tapping points.
Rice. 2.:
1 - pressure gauge; 2 - three-way valve; 3 - shut-off valve; 4 - a tube bent by a ring
Installation diagram of pressure gauge 1 on the pipeline is shown in Fig. 2. To ensure the possibility of turning off the pressure gauge, purging the line and connecting the control pressure gauge, a three-way valve 2 is used, when measuring pressure over 10 MPa (100 kgf / cm2), as well as when monitoring the pressure of a radioactive coolant, an additional shut-off valve 3 is installed at the outlet from the pipeline. When measuring the pressure of media with a temperature above 70 ° C, tube 4 is bent into a ring, in which water is cooled and steam is condensed. At NPPs, the impulse lines of pressure gauges and differential pressure gauges operating with radioactive media are purged into a special drainage system.
When measuring the pressure of aggressive, viscous and liquid metal media, diaphragm and liquid seals are used to protect pressure gauges and differential pressure gauges. A diagram of a pressure gauge with a diaphragm seal is shown in Fig. 3.
Rice. 3.:
1, 2 - aggressive and neutral environment
1 - measured medium; 2 - separating vessel; 3 - a line filled with a neutral medium
An aggressive medium is fed under the membrane 7, the lower part of which and the adjacent walls are covered with fluoroplastic. The space above the diaphragm 2 and the inner cavity of the manometric spring are thoroughly filled with an organosilicon liquid. In order for the pressure above the diaphragm to correspond to the measured pressure during the measurement, it is necessary that the stiffness of the diaphragm be much less than the stiffness of the sensitive element. When using liquid separators (fig. 4), this limitation is absent.
Rice. 4. Installation diagram of pressure gauges with separating vessels when the density of the measured medium is less than the neutral density (a) and more (b):
The neutral separating liquid filling the part of the separating vessel 2, the measuring chamber of the device and the lines between them 3 should differ significantly in density from the medium 1 to be measured and should not mix with it. In fig. 4, and the density of the aggressive medium is less than the separation medium, and in Fig. 4, b - more.
When measuring the difference in pressure, the connection of differential pressure gauges should be made in such a way that the medium filling the impulse lines does not create errors due to the difference in density or the heights of the liquid columns in them. The lines should not have horizontal sections, the minimum angle of inclination should be at least 5 °. When measuring the pressure difference between water and steam, the measuring chambers of the differential pressure gauges must first be filled with water.
The correctness of the manometer readings depends not only on the efficiency of the operation of technological objects, but in many cases also on safety, in this regard, manometers and other pressure devices are subject to periodic checks. For most instruments, the calibration period is one year. If the devices are operated in conditions of increased vibration and temperature, then this period can be shortened. Calibration of instruments is carried out by representatives of metrological services.
For verification of working pressure devices, exemplary devices and devices that reproduce pressure are used. In deadweight testers, these functions can be combined. When verifying pressure gauges designed to measure the pressure of chemically active gases, such as oxygen, do not use deadweight testers filled with oil.
1. The scale must be clearly visible.
2. The approach to the pressure gauge must be free.
3. Depending on the height of the manometer installation, the diameter of the device is selected:
· Up to 2 meters - diameter 100mm;
· From 2x to 3x meters - diameter 160mm;
· Over 3 meters - installation of a pressure gauge is prohibited.
4. Each pressure gauge must have a shut-off device (3-way valve, valve or tap)
Pressure gauge maintenance rules.
According to the technical instructions, land on "O"
Departmental inspection once every 6 months.
State verification - once every 12 months.
Remove and install pressure gauges only with a wrench.
In case of pressure pulsation, measures must be taken:
· At low pulsation, the compensator is welded;
· In case of large ripple, a special device is used - an expander with two chokes.
4. First aid for loss of consciousness (fainting), heat and sunstroke.
Ticket number 2
1. Parameters characterizing the reservoir.
Oil and gas accumulate in cracks, pores and cavities in rocks. The pores of the strata are small, but there are many of them, and they occupy a volume sometimes reaching 50% of the total volume of the rocks. Oil and gas are usually trapped in sandstones, sands, limestones, conglomerates, which are good reservoirs and are characterized by permeability, i.e. the ability to pass fluids through oneself. Clays also have a high porosity, but they are not sufficiently permeable due to the fact that the pores and channels connecting them are very small, and the fluid in them is held stationary by capillary forces.
Porosity is the proportion of void space in the total volume of the rock.
Porosity depends mainly on the size and shape of the grains, the degree of their compaction and heterogeneity. In the ideal case (sorted uniformly sized spherical grains), the porosity does not depend on the size of the grains, but is determined by their mutual arrangement and can vary from 26 to 48%. The porosity of natural sandy rocks, as a rule, is significantly less than the porosity of fictitious soil, i.e. soil composed of spherical particles of the same size.
Sandstones and limestones have even lower porosity due to the presence of the cementitious material. The highest porosity in natural soil is inherent in sands and clays, and it increases (in contrast to fictitious soil) with a decrease in the size of rock grains, since in this case their shape becomes more and more irregular, and, consequently, the packing of grains is less dense. Below are the values of porosity (in%) for some rocks.
Clay shale 0.5-1.4
Clays 6-50
Sands 6-50
Sandstones 3.5–29
Limestones and dolomites 0.5–33
With increasing depth due to increased pressure, the porosity of rocks usually decreases. The porosity of the reservoirs on which the production wells are drilled varies within the following limits (in%):
Sands 20-25
Sandstones 10-30
Carbonate rocks 10–20
Carbonate rocks are usually characterized by the presence of fractures of various sizes and are estimated by the fracture coefficient.
One of the characteristics of rocks is their particle size distribution, on which other physical properties largely depend. This term is understood as the quantitative content in the rock of different grain sizes (in% for each fraction). The granulometric composition of the cemented rocks is determined after their preliminary destruction. The granulometric composition of rocks characterizes to a certain extent their permeability, porosity, specific surface area, capillary properties, as well as the amount of oil remaining in the reservoir in the form of films covering the surface of the grains. They are guided during the operation of wells when selecting filters to prevent the ingress of sand, etc. The grain size of most oil-bearing rocks ranges from 0.01 to 0.1 mm. However, usually when studying the granulometric composition of rocks, the following categories of sizes (in mm) are distinguished:
Pebbles, crushed stone> 10
Gravel 10–2
rough 2-1
large 1-0.5
average 0.5-0.25
fine 0.25-0.1
Siltstone:
large 0.1-0.05
fine 0.05-0.1
Clay particles< 0,01
Particles up to about 0.05 mm in size and their number are set by sieving on a set of sieves of the appropriate size, followed by weighing the residues on the sieves and determining the ratio (in%) of their mass to the mass of the initial sample. The content of smaller particles is determined by sedimentation methods.
The heterogeneity of rocks in terms of texture is characterized by the coefficient of heterogeneity - the ratio of the particle diameter of the fraction, which is 60% by weight of the entire mass of sand with all the finer fractions, to the diameter of the particles of the fraction, which, with all the finer fractions, is 10% by weight of the total mass of sand ( d60 / d10). For "absolutely" homogeneous sand, all grains of which are the same, the coefficient of heterogeneity Kн = d60 / d10 = 1; Kн for rocks of oil fields fluctuates in the range of 1.1–20.
The ability of rocks to pass fluids and gases through themselves is called permeability. All rocks are permeable to one degree or another. Under existing pressure drops, some rocks are impermeable, others are permeable. It all depends on the size of the interconnected pores and channels in the rock: the smaller the pores and channels in the rocks, the lower their permeability. Usually, the permeability in the direction perpendicular to the bedding is less than its permeability along the bedding.
Pore canals are super- and subcapillary. In supercapillary channels, the diameter of which is more than 0.5 mm, fluids move, obeying the laws of hydraulics. In capillary channels with a diameter of 0.5 to 0.0002 mm, when liquids move, surface forces (surface tension, capillary adhesion, adhesion, etc.) forces appear, which create additional forces of resistance to fluid movement in the formation. In subcapillary canals with a diameter of less than 0.0002 mm, surface forces are so great that practically no fluid movement occurs in them. Oil and gas horizons mainly have capillary channels, clayey - subcapillary.
There is no direct relationship between the porosity and permeability of rocks. Sandy strata can have a porosity of 10–12%, but be highly permeable, while clay strata, with a porosity of up to 50%, remain practically impermeable.
For one and the same rock, the permeability will change depending on the quantitative and qualitative composition of the phases, since water, oil, gas or their mixtures can move along it. Therefore, to assess the permeability of oil-bearing rocks, the following concepts are accepted: absolute (physical), effective (phase) and relative permeability.
The absolute (physical) permeability is determined when one phase (gas or homogeneous liquid) moves in the rock in the absence of physicochemical interaction between the liquid and the porous medium when the pores of the rock are completely filled with gas or liquid.
Effective (phase) permeability is the permeability of a porous medium for a given gas or liquid when there is another liquid or gaseous phase in the pores. The phase permeability depends on the physical properties of the rock and the degree of its saturation with liquid or gas.
Relative permeability is the ratio of effective permeability to absolute permeability.
Most of the reservoirs are heterogeneous in texture, mineralogical composition and physical properties vertically and horizontally. Sometimes significant differences in physical properties are found at short distances.
Under natural conditions, i.e. under pressure and temperature conditions, core permeability is different than under atmospheric conditions, it is often irreversible when reservoir conditions are created in the laboratory.
Sometimes the reservoir capacity and commercial oil and gas reserves in the reservoir are determined by the volume of the fractures. These deposits are confined mainly to carbonate, and sometimes to terrigenous rocks.
Usually, there is no strict regularity in the distribution of fracturing systems among the structural elements to which oil and gas-bearing deposits are confined.
To estimate the permeability, a practical darcy unit is usually used, which is approximately 10-12 times less than the permeability of 1 m2.
The unit of permeability in 1 darcy (1 D) is the permeability of such a porous medium, when filtering through a sample of which an area of 1 cm2 and a length of 1 cm at a pressure drop of 1 kg / cm2, the flow rate of a liquid with a viscosity of 1 cP (centipoise) is 1 cm3 / s. A value equal to 0.001 D is called millidarcy (mD).
The permeability of the rocks of oil and gas reservoirs varies from a few millidarsies to 2-3 D and is rarely higher.
There is no direct relationship between the permeability and porosity of rocks. For example, fractured limestones with low porosity often have high permeability, and, conversely, clays, sometimes characterized by high porosity, are practically impermeable to liquids and gases, since their pore space is formed by channels of subcapillary size. However, based on average statistical data, it can be said that more permeable rocks are often more porous.
The permeability of the porous medium depends mainly on the size of the pore channels, from which the pore space is composed.
2. Separators, purpose, device, principle of operation and maintenance.
During production and transportation, natural gas contains various kinds of impurities: sand, welded sludge, condensate of heavy hydrocarbons, water, oil, etc. The source of natural gas pollution is the bottomhole zone of the well, which is gradually collapsing and polluting the gas. Gas preparation is carried out in the fields, the quality of gas depends on the efficiency of their work. Mechanical impurities enter the gas pipeline, both during its construction and during operation.
The presence of mechanical impurities and condensate in the gas leads to premature wear of the pipeline, valves, blower impellers and, as a consequence, a decrease in the reliability and efficiency of the compressor stations and the gas pipeline as a whole.
All this leads to the need to install various process gas purification systems at the compressor station. At first, oil dust collectors were widely used at the compressor station for gas purification (Fig. 3), which ensured a sufficiently high degree of purification (up to 97-98%).
Oil dust collectors work on the principle of wet collection of various mixtures in the gas. The impurities wetted with oil are separated from the gas stream, the oil itself is cleaned, regenerated and again sent to the oil dust collector. Oil dust collectors were often made in the form of vertical vessels, the principle of operation of which is well illustrated in Fig. 3.
The gas to be cleaned enters the lower section of the dust collector, hits the baffle plate 4 and, in contact with the oil surface, changes the direction of its movement. In this case, the largest particles remain in the oil. At a high speed, the gas passes through the contact tubes 3 into the settling section II, where the gas speed decreases sharply and the dust particles flow through the drainage tubes to the lower part of the dust collector I. Then the gas enters the baffle section III, where the final gas purification takes place in the separator device 1.
The disadvantages of oil dust collectors are: the presence of a constant irretrievable oil consumption, the need to clean the oil, as well as to heat the oil under winter operating conditions.
At present, cyclone dust collectors operating on the principle of using inertial forces to trap suspended particles are widely used at the compressor station as the first stage of cleaning (Fig. 4).
Cyclone dust collectors are easier to maintain than oil dust collectors. However, the cleaning efficiency in them depends on the number of cyclones, as well as on the operation of these dust collectors by the operating personnel in accordance with the mode for which they are designed.
The cyclone dust collector (Fig. 4) is a cylindrical vessel designed for the operating pressure in the gas pipeline, with built-in cyclones 4.
The cyclone dust collector consists of two sections: the lower baffle 6 and the upper settling 1, where the final purification of the gas from impurities takes place. In the lower section there are 4 cyclone pipes.
Gas through the inlet nozzle 2 enters the apparatus to the distributor and the star-shaped cyclones 4 welded to it, which are motionlessly fixed in the lower lattice 5. In the cylindrical part of the cyclone tubes, the gas supplied tangentially to the surface makes a rotational movement around the inner axis of the cyclone tubes. Under the action of centrifugal force, solid particles and liquid droplets are thrown from the center to the periphery and flow down the wall into the conical part of the cyclones and then into the lower section 6 of the dust collector. The gas after the cyclone tubes enters the upper settling section 1 of the dust collector, and then, already cleaned, leaves the apparatus through the branch pipe 3. During operation, it is necessary to control the level of the separated liquid and mechanical impurities in order to remove them in a timely manner by blowing through the drain fittings. Level control is carried out with the help of sight glasses and sensors fixed to fittings 9. Manhole 7 is used for repair and inspection of the dust collector during scheduled shutdowns of the compressor station. The efficiency of gas cleaning by cyclone dust collectors is at least 100% for particles with a size of 40 microns and more, and 95% for particles of dropping liquid.
Due to the impossibility of achieving a high degree of gas purification in cyclone dust collectors, it becomes necessary to perform the second stage of cleaning, which is used as filter separators installed in series after the cyclone dust collectors (Fig. 5)
The work of the filter separator is carried out as follows: the gas after the inlet pipe is directed to the inlet of the filtering section 3 with the help of a special baffle plate, where the liquid is coagulated and cleaned from mechanical impurities. Through perforated holes in the housing of the filter elements, the gas enters the second filter section - the separation section. In the separation section, the final purification of gas from moisture takes place, which is captured using mesh bags. Through drainage pipes, solids and liquid are removed to the lower drainage collector and further to underground tanks.
For operation in winter conditions, the filter-separator is equipped with electric heating of its lower part, a condensate collector and instrumentation. During operation, mechanical impurities are captured on the surface of the filter separator. When a drop of 0.04 MPa is reached, the filter-separator must be turned off and the filter elements must be replaced with new ones in it.
As experience in the operation of gas transmission systems shows, the presence of two degrees of purification is mandatory at underground gas storage stations, as well as at the first downstream compressor station that receives gas from the UGSF. After cleaning, the content of mechanical impurities in the gas should not exceed 5 mg / m3.
The gas supplied to the head compressor stations from the wells, as noted, almost always in the same amount contains moisture in the liquid and vapor phases. The presence of moisture in the gas causes corrosion of equipment and reduces the throughput of the gas pipeline. When interacting with gas under certain thermodynamic conditions, solid crystalline substances-hydrates are formed, which disrupt the normal operation of the gas pipeline. Gas dehydration is one of the most rational and economical methods of hydrate control at large pumping volumes. Gas dehydration is carried out by devices of various designs using solid (adsorption) and liquid (absorption) absorbers.
With the help of gas dehydration units at the head facilities, the content of water vapor in the gas is reduced, the possibility of condensate falling out in the pipeline and the formation of hydrates is reduced.
3. Systems and schemes for collecting, transporting gas, their advantages and disadvantages
A pressure gauge is a special device that is designed to measure pressure. Such devices come in different types and are installed in different ways. Let's consider them in detail.
Methods for installing pressure gauges
Direct installation method
The pressure gauge with special thread seals is immediately screwed onto the pre-welded adapter. This method is considered the most affordable and is used to operate the device in a stable environment without strong pressure surges and without constant replacement of the device.
Installation method on a three-way valve
A three-way valve is screwed onto the pre-welded adapter using threaded connections, and a pressure gauge is screwed into it. A similar method is used if it is necessary to transfer the device to atmospheric pressure with this valve when checking the readings.
The latter allows you to change the device without interrupting the operating cycle, or to pressure the system and other work that is associated with an increase in pressure in the system.
Installation method with impulse tube 
In addition to the above two methods, the pressure gauge is also installed through the impulse tube, which is able to protect the sensitive mechanism of the device from damage.
To install a pressure gauge using a similar method, screw the impulse pipe vertically onto the pre-welded adapter, connect a three-way valve and the pressure gauge itself there.
The impulse tube is used in situations where the steam has a temperature that exceeds the possible norm of the measured parameters. It prevents the pressure gauge from contacting hot steam.
What rules should be followed when installing pressure gauges?
- The pressure gauge should be mounted exactly so that the readings are clearly recognizable. The scale is vertical or tilted at 30 °.
- The diameter of the device body, mounted at a height of up to two meters from the level of the platform, cannot be less than 100 mm, from two to three meters - not less than 160 mm. Installation of the device at a height of more than 3 m from the level of the site is strictly prohibited.
- Any pressure gauge should be well lit and protected from the rays of the sun and frost.
- When installing the pressure gauge, it is necessary to tighten it on the tee, moreover, not reaching the device itself, in order to release the air.
- The pressure gauge cannot be used if it does not have a seal with a note on the check carried out, the period of this check is overdue, the arrow of the device (when it is turned off) does not return to zero, the glass is cracked, there is even the slightest damage to the device.
If you find a device malfunction, then it should be handed over for repair, after having cleaned it from dirt and rust.
Thus, if you need to install a pressure gauge, be sure to contact a specialist. The installation of this device must be strictly carried out by a qualified employee of the organization using special equipment.
- Before starting work, the user must be sure that the manometer (vacuum gauge, manovacuum gauge) is correctly selected in terms of the measurement range and design. The measuring range is optimally selected when the working pressure is located at middle third range of indications.
- The instrument should be secured in a shock-free location and positioned so that easy access to it is provided for easy reading of the readings.
- The connections must be tight.
- Between pressure measuring point and pressure gauge it is recommended to install a shut-off device to ensure the replacement of the measuring device and control of the "zero" in working order.
- Depending on the purpose of the pressure gauge, it can be equipped with shut-off valves or valves.
- The place used on process equipment or pipeline to control pressure is called selection(impulse) pressure.
- The route connecting the pressure tap to the pressure gauge is called impulse line.
- Depending on the pressure value, aggressiveness, fire hazard and explosion hazard of the measured media, impulse lines consist of copper, steel seamless or PVC tubes.
- The diameter of the impulse pipes and their thickness during installation are selected based on the length of the route and the maximum working pressure of the medium.
- Impulse lines for measuring the pressure of controlled media must be laid in strict accordance with the installation diagram of the facility automation, which indicates the length of the route and the full characteristics of the line: type of material used; section and wall thickness.
- Taps (pulses) of pressure are usually installed on straight sections of pipelines and technological equipment, taking into account bends, bends, elbows and tees, where an additional measurement error occurs, caused by the centrifugal force of the measured flow of the medium.
- Diaphragm seals, vessels: in the presence of aggressive, hot, highly viscous, dirty or crystallizing media that must not penetrate the measuring element, media separators must be provided as separating devices. In this case, the inner space of the manometer and separator is filled with a working fluid, which serves to transfer pressure from the diaphragm of the separator to the manometer, which is selected depending on the measuring range, temperature and compatibility with the measured medium.
- When measuring the pressures of acids and alkalis, separating vessels are used to protect the inner surface of the sensitive element of the device, the inner cavity of which is filled with water, light mineral oils, glycerin, ethyl alcohol, etc.
- Overload protection of sensitive elements: in case the measured medium pulsates or if water hammer is likely, prevent their direct impact on the sensitive elements.
- To do this, it is necessary to ensure damping of hydraulic shocks by installing a throttle (reducing the cross-section of the pressure channel) or by installing an adjustable throttle device.
- Also, to eliminate and smooth the pulsation of the measured pressure of liquids, steam and gases at compressor stations, in pumps, technological equipment and pipelines, leading to failure of the transmission mechanism of devices, a special choke is installed in the pressure gauge fitting, which allows to significantly reduce the diameter of the inlet.
- In the event that the measuring range in order to obtain more accurate readings is chosen less than the magnitude of short-term pressure surges, it is necessary to protect the sensitive element from damage. For this, an overload protection device must be installed - a device that closes instantly with a hydraulic shock, with a gradual increase in pressure, it closes gradually.
- The set closing value therefore depends on the characteristic of the pressure change over a certain period of time.
- Another option is to use a pressure gauge that is resistant to overpressure (internal protection).
- Mounting the pressure gauge: if the connection to the pressure gauge does not provide sufficient fixing stability, thenprovide suitable fasteners on the wall and / or pipe; otherwise, provide the pressure gauge with a capillary line.
- Damping vibrations (vibrations) of the measuring system: If shocks cannot be prevented by proper installation, vibration-resistant instruments with liquid filling (liquid filling) should be used.
- As a rule, the pressure gauge is installed with a vertically standing dial. In case of deviations, you need to pay attention to the position sign on the dial.
- It is recommended to use a turnbuckle or a union nut to set the pressure gauge to a position that provides maximum reading.
- Do not screw in and out the pressure gauge by the body - for this, there are surfaces for a wrench on the connecting nipple.
- Gaskets, washers made of leather, fiber, lead or soft copper must be used as a seal at the junction of the instruments with the pressure source..
- For instruments used to measure oxygen pressure, use only copper and lead gaskets.
- For instruments measuring the pressure of acetylene, it is prohibited to use gaskets made of copper and copper alloys containing more than 70% copper..
- If the device is located below the pressure taps, thoroughly flush the measuring line before connecting in order to remove solid inclusions.
- To compensate for internal pressure, some types of devices have holes closed with a plug, which are labeled " CLOSED" and " OPEN". In the normal state, the vent hole is closed (lever in the" CLOSED "position) Before checking and / or after installation, as well as before starting work, these devices are filled with air, ie the lever is set to the" OPEN "position.
- When pressure testing or purging pipelines or containers, do not subject the pressure gauge to a load exceeding the limit mark on the dial. Otherwise, lock or dismantle the device.
- Before removing the pressure gauge, remove the pressure from the measuring element. Otherwise, remove the voltage from the measuring line.
- For pressure gauges with leaf spring, do not remove the tightening screws on the top and bottom flanges.
- Fluid residues in dismantled pressure gauges can be hazardous to people, the environment and premises. The necessary steps should be taken to ensure safety.
- Pressure gauges, the sensing elements of which are filled with water or a mixture of water, must be protected from freezing.
- The measuring line must be manufactured and installed in such a way as to absorb the stress caused by stretching, vibration and heat.
- If the measured medium is a gas, then at the lowest point, there should be a possibility for drainage, if it is liquid, then at the highest point, provide a possibility for deaeration.
- When working with gases and liquids containing solid impurities, cutting devices (separators) are provided, which can be separated through the shut-off valves from the installation during its operation and be freed from impurities.
And all your NOT zamorochki paid by the Customer (according to most designers, he has a grove of money trees - shook a branch, paid someone's laziness). Or maybe from ignorance of physics. And why is the valve block to the pressure gauge ??? As a rule, there are fewer thermometers than there are points for installing pressure gauges, or embedded ones, for connecting a pressure gauge if necessary (fittings). Sometimes it is helpful to ask the surveyor what the difference is. And why DN 50, if they put a thermometer there. According to Belarusian laws, a dilator is needed when DN is less than 65 (76 external), I think the requirement is justified.
And in the opinion of all customers, designers do not know how to design at all and only want to put the customer on the headstock. And I do not care what is being done according to the norms and there is a developed methodology - the main thing is that THEM IS SO INCONVENIENT, which means it is wrong.
I explain. Previously, specific devices with specific threads, etc. were ordered, so the selection device was selected based on the installation location and the ordered device. Now a specific device cannot be ordered - in 99% of cases the customer buys devices by tender. Likewise with valve manifolds. In order not to bother with the thread, both here and there, questionnaires have been developed, where valve blocks, diaphragm seals, siphon ring tubes, etc. go complete with devices. Our problem would be in the combination of all this and alterations if we bought another, additional order of connectors and adapters. The customer should conduct several tenders, plus the customer's representatives also analyze the proposed options, that is, they also spend a lot of time. In this regard, the OL were developed by the Rosneft design institute and approved by the relevant department. We also work a lot with Rosneft and have adopted the same OL. We offer the same OL to other Customers - there are some comments from them, but basically everyone agrees.
Now regarding the transition - the size of the boss allows you to install it at least on pipe 50 without significantly overlapping the pipe section. Our mechanics and installers forbid us to put on a smaller diameter. There remains one thing - to put the expander. Whether it will be ordered in the instrumentation part as a separate standard part or as a set of standard parts from installers (and they already have such parts in full - ordinary transitions and a piece of pipe), these are already parts. It's much easier for everyone if these standard parts are ordered by the installers, and not we will do the crap. You know - so far NOT ONE claims! More precisely, I'm lying - there was one ... In Saratov, instead of a boss, they wanted a branch pipe with an EXTERNAL thread for installing pressure sensors and manometers. But this, as you can imagine, is not so much related to small diameters as to pressure in general.
Why do you need a valve manifold for a pressure gauge? The pressure gauge also measures pressure and may fail like a conventional pressure sensor, which means it may need to be removed for replacement or verification. It is for these purposes that a valve block is installed. No, you can, of course, supply two conventional valves - a shut-off and a relief valve, you can order a design with one valve and a relief hole, a lot of things are possible. But the customer still wants unification - so that one part can be put in another place - to another manometer or pressure sensor.
Regarding thermometers - pipe DN 50, boss height 50, total 100mm. If you take an 80 mm sleeve, it will go into the pipe by 30 mm, that is, and once it falls into the second third - as is customary to put. If you put an expander (according to the ZK), then you can take a sleeve and take 100mm.
And we never had pipe 65 - only 50, 80, 100 and beyond.
