01
What are the requirements for piping layout design?
(1) The piping layout design shall meet the requirements of process piping and instrument flow charts;
(2) The pipeline layout should be planned as a whole, so as to be safe, reliable, economical and reasonable, meet the requirements of construction, operation, maintenance, etc., and strive to be neat and beautiful;
(3) When determining the orientation and laying method of pipelines entering and exiting devices (units), internal and external coordination should be achieved;
(4) The laying of plant-wide pipelines in the plant area should be coordinated with the devices (units), roads, buildings, etc. in the plant area to avoid surrounding devices (units) with pipelines and reduce the intersection of pipelines with railways and roads;
(5) The pipeline should be set up overhead or on the ground. If necessary, it can be buried or laid in trenches;
(6) The pipelines should be arranged in rows, and the pipelines on the ground should be laid on pipe racks or pipe piers;
(7) When arranging pipes on pipe racks and pipe piers, the vertical load and horizontal load on pipe racks or pipe piers should be balanced;
(8) A margin of 10%-30% should be left on the plant-wide pipe frame or pipe piers (including crossing culverts), and its load should be considered. A 10%-20% margin should be reserved for the pipe frame of the main gallery of the device, and its load should be considered;
(9) The layout of pipelines with special requirements for distance, angle, height difference, etc. and large-diameter pipelines for conveying medium shall meet the requirements of equipment layout design;
(10) The pipeline layout should not hinder the installation, maintenance of equipment, pumps and their internal components, and the passage of fire-fighting vehicles;
(11) The piping arrangement should make the piping system have the necessary flexibility. In the case of ensuring the flexibility of the pipeline and the force and moment of the pipeline on the nozzle of the equipment and the pump do not exceed the allowable value, the pipeline should be the shortest and the components should be the least;
(12) The support point set should be considered while planning the pipeline. The natural shape of the pipeline should be used to achieve self-compensation;
(13) The pipeline layout should be “step-by-step high” or “step-by-step low” to reduce air pockets or liquid pockets. When unavoidable, venting and cleaning should be set according to the operation and maintenance requirements, and the pipeline layout should reduce “cecum”;
(14) When the gas-liquid two-phase flow pipeline is divided into two or more pipelines from one pipeline, the layout of pipelines should consider symmetry or meet the requirements of pipeline and instrument flow charts.
(15) Pipelines shall be connected by welding, except those that need to be connected with valves, instruments, equipment, etc. by flanges or threads.
Flanges, threads or other detachable connections shall be considered for the following idle conditions:
Occasions that need to be disassembled for maintenance, cleaning and purging;
Lined or jacketed pipes;
The pipeline is composed of two sections of dissimilar materials and it is not suitable to be connected by welding;
Pipe connection points where welding seams are difficult to heat treat on site;
Galvanized pipes with a nominal diameter less than or equal to 100mm;
Set the position of the blind plate or “8” figure blind plate.
(16) The gas branch pipe should be connected from the top of the main pipe.
(17) Toxic medium pipelines shall be connected by welding, and shall not be connected by flanges or threads unless there are special needs. Toxic medium pipelines should have obvious signs to distinguish them from other pipelines, and toxic medium pipelines should not be buried underground.
(18) When arranging solid materials or pipelines containing solid materials, the pipeline should be as short as possible. Less turns and no dead ends:
The connection between the solid material branch pipe and the main pipe should be mitered along the flow direction of the medium, and the included angle should not be greater than 45°;
The bending radius of the elbow on the solid material pipeline should not be less than 6 times the nominal diameter of the pipeline;
Slurry pipelines and high-viscosity liquid pipelines containing a large amount of solid materials should have slopes.
(19) For pipelines that require thermal compensation, the entire piping system should be analyzed from the beginning to the end of the pipeline to determine a reasonable thermal compensation scheme.
(20) For pipes that require a slope to be laid on the pipe gallery, the height of the pipe support can be adjusted. It can be realized by adding section steel or steel plate cushion on the pipe support. The main pipe for venting gas (or the main pipe for torch removal) should be arranged at the top of the column of the pipe gallery to facilitate the adjustment of the elevation.
(21) When arranging the piping connected with the rotating mechanical equipment, the piping system should be flexible enough to meet the allowable force requirements of the equipment nozzle. The following measures can be taken when necessary:
Change the pipeline direction and enhance the natural compensation ability;
Choose a spring support hanger;
Use metal bellows compensator;
Set the limit bracket at the appropriate position.(22) When arranging the pipeline connected to the reciprocating compressor, the mechanical vibration natural frequency of the pipeline system and the gas column natural frequency of the pipeline should avoid the excitation frequency of the machine. The following measures can be taken when necessary:
Add anti-vibration support;
Appropriately expand the pipe diameter;
Add a pulsation attenuator or orifice;
Reasonably set the buffer, avoid the length of the resonance tube, and reduce the bend as much as possible.(23) Branch pipes should not be installed at the parts with large bending moments on the vibrating pipe.
(24) At the turning of pipelines that are prone to vibration (such as reciprocating compressors, outlet pipelines of reciprocating pumps, etc.), elbows with a bending radius of not less than 1.5 times the nominal diameter should be used. The branch pipe is directly connected to the outside along the medium flow.
(25) When a branch pipe with a nominal diameter less than or equal to 40mm is connected from a pipeline that may vibrate, no matter whether there is a valve on the branch pipe, strengthening measures should be taken at the connection.
(26) The self-flowing horizontal pipeline should have a gradient of not less than 3‰ along the flow direction of the medium.
(27) When the pipe passes through the floor, roof or wall of the building, a sleeve should be added, and the gap between the sleeve and the pipe door should be sealed. The diameter of the sleeve should be larger than the outer diameter of the pipe insulation and must not affect the thermal displacement of the pipe.
The weld on the pipe shall not be inside the casing and shall not be less than 150mm from the end of the casing. The casing should be 50mm higher than the floor and roof. When the pipeline passes through the roof, a rain cover shall be installed, and the pipeline shall not pass through the firewall or explosion-proof wall.
(28) When arranging corrosive media, toxic media and high-pressure pipelines, hazards to personnel and equipment caused by leakage of flanges, threads and packing seals should be avoided. The parts prone to leakage should avoid being located above the pedestrian passage or the pump, otherwise, safety protection should be provided.
(29) For pipes with a heat insulation layer, pipe brackets should be provided at pipe piers and pipe supports. For pipelines without a heat insulation layer, if there is no requirement, no pipe support is required.
When the thickness of the heat insulation layer is less than or equal to 80mm, a pipe support with a height of 100mm is selected; when the thickness of the heat insulation layer is greater than 80mm, a pipe support with a height of 150mm is selected;
When the thickness of the heat insulation layer is greater than 130mm, use a pipe support with a height of 200mm;
The cold insulation pipe should use the cold insulation pipe support.(30) When the terrain height difference in the plant area is large, the plant-wide pipeline laying should be consistent with the terrain height difference. Adjust the elevation of the pipe gallery at the appropriate position. The minimum slope of the pipeline should be 2‰. The slope change point of the pipeline should be set at the turning point or near the fixed point.
(31) For pipelines that cross or pass through railways and roads in the plant area, valves, metal bellows compensators, flanges, threaded joints and other pipeline components shall not be installed on the crossing section or crossing section.
(32) For buried pipelines with thermal displacement, retaining piers can be installed if the arc of the pipeline is allowed, otherwise, thermal compensation measures should be taken.
(33) The setting of pipeline welds during pipeline layout shall meet the following requirements:
The distance between the center of the pipe butt weld and the bending point of the elbow should not be less than the outer diameter of the pipe: and not less than 100mm;
The distance between the centers of two adjacent butt welds on the pipe: a. For pipes with a nominal diameter less than 150mrn, it shall not be less than the outer diameter, and shall not be less than 50mm; b. For pipes with a nominal diameter equal to or greater than 150m, it shall not be less than 150mm;
The clear distance between the girth weld and the edge of the support and hanger should not be less than 50mm; the minimum clear distance between the weld that needs heat treatment and the edge of the support and hanger should be greater than 5 times the width of the weld and not less than 100mm.
02
What factors should be considered in determining the width, span and height of the main corridor in the device?
The width of the corridor:
l) The width of the pipe gallery is mainly determined by the number of pipes and the size of the pipe diameter. And consider a certain reserved width. Generally, the pipe frame of the main main corridor should have a margin of 10%-20%, and its load should be considered. At the same time, the impact of structures such as equipment and passages under the pipe gallery and air cooling equipment on the pipe gallery should be considered. If it is required to lay instrument cable troughs and power cable troughs, the required width should also be considered. The pipes on the pipe gallery can be arranged in single layer or double layer, and can also be arranged in three layers if necessary. The width of the pipe corridor should generally not be greater than 10m;
2) When the air cooler is arranged on the pipe gallery, the span of the pillars should be the same as the spacing of the air cooler, so that the pillars of the pipe gallery are aligned with the centerline of the air cooler pillars;
3) When the pump is arranged under the pipe gallery, the layout of the pump and the width of the required operation and maintenance passages should be considered. If the cable for the pump driver is laid underground, the required width of the cable trench should also be considered. In addition, the width required for the main pipe of the cooling water pipe for the pump and the drain pipe should also be considered;
4) Since the arrangement density of pipes in the whole pipe gallery is not the same, the number of pipes in the first and last section of the pipe gallery is usually less. Therefore, when necessary, the width of the first and last sections of the pipe gallery can be reduced or the double-layer pipe gallery can be changed into a single-layer pipe gallery.
The span of the corridor:
The column spacing of the pipe gallery and the span of the provincial gallery are determined by the allowable bending deflection of the pipes laid on it due to the vertical load, usually 6-9m. For example, in small and medium-sized installations, when there are many small-diameter pipes, a sub-beam can be installed between the two pillars to reduce the span of the pipes. In addition, the spacing of the pillars of the pipe gallery should be consistent with the spacing of the equipment frame pillars to facilitate the passage of pipelines. If it is a concrete pipe frame, a φ20 round steel or steel plate should be buried on the top of the beam to reduce the friction between the pipe and the beam.
The height of the pipe gallery can be determined according to the following conditions:
1) Space across the road. When the pipe gallery crosses over the road, its clearance height is:
The inspection road in the device should not be less than 4.5m;
The factory road should not be less than 5.0m;
The railway should not be less than 5.5m;
The maintenance passage under the pipe gallery shall not be less than 3m.
When the pipe gallery has trusses, it shall be calculated according to the bottom height of the trusses.
2) The minimum height of the pipe under the pipe gallery. In order to effectively use the space of the pipe gallery, the pumps are often arranged under the pipes. Considering the operation and maintenance of the pump, at least 3.5m is required; when the pipeline on the pipe gallery is connected to the partition equipment, it should generally be 600-1000mm lower or higher than the bottom pipe level of the pipe gallery. Therefore, the minimum pipe base standard at the bottom of the pipe gallery is 3.5m. When the shell-and-tube cooling equipment is arranged under the pipe gallery, due to the increase in equipment height, it is necessary to increase the clearance under the pipe gallery.
3) The height difference of vertically intersecting pipe galleries. If the direction of the provincial corridor changes or the two pipe corridors intersect at right angles, the height difference depends on the minimum size of the interconnection of the pipes, generally 500-750mm is appropriate. For large installations, a height difference of 1000mm can also be used.
Structural dimensions of the pipe gallery. When determining the height of the provincial corridor, the structural section and type of the beam and longitudinal beam of the pipe gallery should be considered, and the height of the bottom of the beam and the bottom of the frame must meet the above-mentioned requirements for determining the height of the pipe gallery. For the double-layer pipe gallery, the distance between the upper and lower floors is generally 1.2-2.0m, which is mainly determined by the diameter of the largest pipe on the pipe gallery.
As for the height of the pipe gallery between the devices, it depends on the specific conditions of the area where the pipe rack passes. If a tank area is formed along the edge of the factory, it will not affect the traffic and expansion of the factory area. Considering economy and maintenance convenience, pipe piers can be used for laying, and the height from the ground of 300-500mm can meet the requirements.
03
What are the principles of pipeline design for flammable liquids, flammable gases, and liquefied hydrocarbons?
The principles of pipeline design for flammable liquids, flammable gases, and liquefied hydrocarbons are:
(l) Pipelines must not pass through buildings that have nothing to do with them;
(2) The pipeline should be laid overhead or along the ground;
(3) When pipe trenches must be used for laying, measures should be taken to prevent gas or liquid from accumulating in the pipe trenches, and the entrance and exit devices and workshops should be sealed off;
(4) The sewage in the pipe ditch shall be water-sealed and discharged into the production sewage pipeline;
(5) The sampling pipeline should not be introduced into the laboratory;
(6) Metal pipes shall be connected by welding except for special flange connections.
04
Which media pipelines must be electrostatically grounded? What are the requirements for the ground connection point and ground resistance value of the pipe network?
Pipelines for combustible gas, liquefied hydrocarbons, combustible liquids, and combustible solids should be provided with electrostatic grounding facilities at the following locations:
(1) The pipelines in each relatively independent building (structure) in the installation area can be electrostatically grounded through the connection (flange connection) with the metal shell of the process equipment;
(2) Pumps, filters, buffers, etc. in the pipe network should be provided with grounding connection points;
(3) The pipe network should be grounded at the entrance and exit of the device area, the boundary of different explosive hazardous environments, and the pipeline bifurcation. For long-distance branchless pipelines, it should be reliably connected to the grounding body every 80-100m;
(4) For the non-conductor pipe section (such as polyvinyl chloride pipe) in the middle of the metal pipe, in addition to shielding protection, the metal pipes at both ends should be connected to the grounding trunk line respectively, or after jumping with 6mrn multi-strand copper core insulated wires grounding;
(5) Metal parts on non-conductor pipe sections should be grounded.
The grounding resistance value of each set of specially designed electrostatic grounding bodies should be less than 100Ω; in places with high soil resistivity in mountainous areas, the grounding resistance value should be less than 1000Ω.
05
What are the types of pipeline laying? What are its advantages and disadvantages?
There are two types of pipeline laying methods: above-ground and below-ground:
(1) Overhead laying
Above the ground, commonly known as overhead laying, is the main way of laying pipelines in industrial production equipment. It has the advantages of convenient construction, operation, inspection, maintenance and economy;
(2) Underground laying
1) Buried laying:
Advantages: It makes use of the underground space to make the space above the ground relatively simple and does not require support measures;
Disadvantages: The pipeline is highly corrosive, difficult to inspect and maintain, sometimes special treatment is required at the roadway to withstand a large load, it is inconvenient to drain at low points, and it is difficult to handle when condensable oil solidifies in the pipeline, and the insulation layer It is difficult for the pipeline to maintain its good heat insulation function, so it is only used when it is impossible to lay it overhead;
2) Pipe trench laying:
Advantages: It can make full use of the underground space and provide more convenient inspection and maintenance conditions; it can also lay pipes with high temperature, condensable or corrosive media with heat insulation layers;
Disadvantages: high cost, large floor area, need to set up drainage points, easy to accumulate or single-entry oil and gas increase unsafe factors, easy to accumulate dirt and difficult to clean up, etc. Therefore, pipe trenches are only used when necessary in the device.
06
What are the conditions for pipelines that allow direct burial of pipelines?
(1) Liquid and gas pipelines with non-corrosive, non-toxic and non-explosive conveying media cannot be laid on the ground for some reason;
(2) Process medium pipelines related to underground storage tanks or underground pump houses;
(3) Cooling water and fire-fighting water or foam fire-fighting pipes;
(4) Heat pipes with an operating temperature less than 150°C.
07
What are the requirements for the buried depth of buried pipelines?
The burial depth of the buried pipeline should be based on the principle that the pipeline will not be damaged, and the influence of the maximum frozen soil depth and groundwater level should be considered.
The distance from the top of the pipe to the ground should not be less than 0.5m; if there is a concrete floor indoors or outdoors
