Process Piping Engineering (Reading Drawings)

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Section 1: Reading Construction Drawings for Installation Projects I. Preparatory work before compilation: (Several conditions that must be met) 1. Complete construction drawings: including general drawings and detailed drawings. A. The basic drawings include a drawing catalog, construction details, a list of equipment and materials, flow diagrams, floor plans, axonometric views, and elevation (section) views. The details include node diagrams, detail drawings, and standard drawings (reusable diagrams). B. Drawing index: For a large number of construction drawings, designers organize them into a drawing index based on specific drawing names and order to facilitate reference. C. Construction drawing instructions: These are technical and quality requirements that cannot be shown on the drawings but which workers need to be aware of; they are generally explained in written form. D. List of equipment and materials: A detailed list showing the names, specifications, models, and quantities of various equipment, as well as different types of pipes, fittings, valves, and anti-corrosion and insulation materials required for this project. The above three points are textual descriptions, but they are essential components of construction drawings. E. Flowchart: It represents the process changes in a production system. Through it, a clear understanding can be obtained of the specifications of equipment, buildings, instruments, and pipelines, as well as the medium being transported and the main control valves. F. Plan: The basic drawing in the construction drawings. It mainly shows specific data such as the planar layout of the equipment, the direction and arrangement of pipelines, as well as their elevations, so that construction workers can gain a comprehensive understanding of the project. G. Elevation and sectional views: The most common types of drawings in construction plans, showing the vertical arrangement and orientation of the equipment, as well as the pipe diameters and elevations. M, Details: Node diagram: It shows in detail the structure and dimensions of a specific section of the piping system; it is an enlarged view of certain elements that cannot be clearly depicted in floor plans or other diagrams. Detail drawing: A detailed view of the equipment piping and pipe fittings assembly, characterized by a double-line representation that gives the objects a sense of realism. Standard pattern: (Reusable pattern) A pattern with universal properties. It cannot be used as a drawing for construction on its own; it serves only as a component of certain construction drawings. Standard atlases are generally published by ** or relevant departments. 2. The current engineering budget quotas and unit price lists. 3. The current budget prices of materials in the location of the project, along with the relevant regulations regarding material price adjustments (prices are adjusted accordingly based on coefficient adjustments or as stipulated). The charging standards are determined based on the type of project and the company’s tier. 4. Construction organization measures approved by the relevant departments, including the transportation, lifting of large-scale equipment, as well as tasks such as three connections and one leveling. The work items that are not covered by the standard construction drawing budget are prepared in accordance with the construction organization measures. II. Several issues that should be understood by examining the drawings: 1. Project overview: For example, in a oil transfer station, there are pump rooms, tank areas, heating furnace areas, as well as a network of pipelines that connect these different areas; in addition, there are heating systems and water supply and drainage systems. For example: 2. Understand the materials specified by various systems, as well as the operating pressure and temperature of the media, and be aware of the weld grade of the pipes, in order to ensure proper treatment of the welds (heat treatment and non-destructive testing). 3. Based on the preparation instructions and blueprints, determine the location of the pipes (above ground, underground, inside ditches, outside ditches), as well as the requirements regarding pipe anti-corrosion, coating, and insulation. III. Symbols and Legends: 1. Line types: Thick solid line: Main pipelines; Solid line within the frame: Auxiliary pipelines and branch pipelines; Thin solid line: Lines representing fittings and valves, outlines of buildings and equipment, dimension lines, and leader lines. Dashed-dotted line: Positioning axis; solid dashed line: Underground pipelines, those covered by equipment. Dashed line: Auxiliary pipelines inside equipment, connection wires for automatic control instruments, invisible contour lines. Wavy line: Boundary lines at the break points of pipe fittings and valves. 2. Standard codes for pipelines: Commonly used codes: Oil pipeline – Y; Oil and gas mixture pipeline – YM; Crude oil pipeline – Y1; Crude oil with water – SY; Natural gas pipeline – M; Water supply pipeline – S; Drainage pipeline – X; Circulating cooling water – XH; Steam pipeline – Z; Hot water pipeline – R; Hot water for production – R1; Hot water return pipeline – R4; Return pipeline (condensate water) – N. 3. Common legends: See Table 2-2-1. Common legends for process pipeline installation construction drawings Table 2‑2‑1 Serial Number Name Symbol Serial Number Name Symbol 1 Threaded valve Elbow 2 Flanged valve Tee 3 Welded valve Equal-diameter reducer 4 Globe valve Unequal-diameter reducer 5 Gate valve Plug 6 Check valve Coupler 7 Corner valve Threaded pipe cap 8 Spring-loaded safety valve Quick connector 9 Flange Wave compensator 10 Blind flange Square compensator 11 Pipe cap Sleeve compensator Y-filter Movable support T-filter Guiding support Fixed support 3. Representation methods in construction drawings: A. Title block: Project: Specific name of the project Drawing title: Name and main content of this drawing Design number: Number assigned by the design department to this project Drawing code: Sequence number of this professional drawing B. Scale: Reduction scale: 1:2, 1:3, 1:5, …… Enlargement scale: 2:1, 4:1, 10:1, …… How to determine the scale when there is no specified scale? Common scales used in pipeline construction drawings: 1:25, 1:50, 1:100, 1:200, 1:500 C. Elevation: The height of pipelines is indicated using elevations. In elevation (section) drawings, to indicate the vertical spacing between pipes, only relative elevations are usually indicated, without specifying the actual spacing dimension. The relative elevation of the pipeline is taken with the indoor floor level of the lower floors of the building as zero. For pipes with a larger diameter, it is possible to specify not only the elevation at the center of the pipe but also the elevations at the bottom and top of the pipe. General elevation: Elevation of the pipe center; Elevation of the top and bottom of the pipe. D, Slope and direction indicators: E. Dimension lines: Starting line (arrow), dimension lines, dimension numbers, dimension boundaries. Starting line, Dimension line, 400, Dimension number, Dimension boundary. IV. Reading construction drawings for pipe installation projects: Construction drawings represent the designer’s complete intentions regarding the project being designed. Reading these drawings is an important and crucial step for estimators to understand the details of the project; it is also a fundamental requirement and stage in preparing cost estimates based on the construction drawings. (1) Single-line and double-line diagrams of pipelines: Pipeline construction drawings can be divided into single-line diagrams and double-line diagrams based on the layout of the drawings. The method of representing the shapes of pipes and fittings with only two lines in a diagram is called the double-line representation; the diagrams created using this method are known as double-line drawings. Additionally, since the cross-sectional dimensions of pipes are much smaller, in construction drawings at small scales, the wall thickness of the pipes as well as their hollow interiors are often represented as the projection of a single line. This style of drawing, in which pipes and fittings are represented by a single thick solid line in the diagram, is commonly known as the single-line representation method; the diagrams created using this method are called single-line drawings. Next, we will focus on learning the representation method of pipeline single-line diagrams. 1. Single-line diagram of the pipe: Figure 2-2-1 shows the single-line diagram of the pipe. According to the principles of projection, its planar projection should converge into a small dot; however, for easier identification, we have drawn a small circle outside that dot. In most construction drawings, only a small circle is shown in Figure 2-2-1, with no dot at the center; the meaning conveyed is the same in all cases. The elbow represented by a line diagram is shown in Figure 2-2-2: on the plan view, the break in the vertical pipe is seen first, followed by the horizontal pipe. The break in the vertical pipe is represented as a small circle, while the horizontal pipe is represented as a line. In the side view, the vertical pipe is visible on the line, while the break of the horizontal pipe is not visible on the back side; at this point the horizontal pipe appears as a small circle, and the vertical pipe is drawn at the center of this small circle, indicating that in Figure 2-2-2 the vertical pipe extends downward and then backward. Figure 2-2-3 shows a single-line diagram of the 450 elbow. The drawing method for the 450 elbow is similar to that of the 900 elbow; the only difference is that the 900 elbow is depicted as a complete small circle, while the 450 elbow is shown as half a small circle. Figure 2-2-3 Figure 2-2-4 Figure 2-2-5 Figures 2-2-4 and 2-2-5 are single-line diagrams of the San Tong. Figure 2-2-4: On the plan view, the break of the vertical pipe is visible first; therefore, the vertical pipe is drawn as a small circle, with the horizontal pipes drawn on either side of this circle. On the left elevation view, the cross-section of the horizontal pipe is visible first; therefore, the horizontal pipe is drawn as a small circle, with the vertical pipe placed above that circle. The plan view in Figure 2-2-5 shows a tee; in the elevation view, the horizontal pipe is visible first – it appears as a line, and the end of the pipe extending backward is not visible, so the horizontal pipe passes through the center of the circle. In the left view, the cross-section of the horizontal pipe is seen first, with the pipeline extending backward to the left side of the small circle. In a single-line diagram, whether it is a equal-diameter tee or a reduced-diameter tee, their graphical representation is the same. Figure 2-2-6 Figure 2-2-6 is a single-line diagram of the four-way valve. The schematic representations of equal-diameter tees and unequal-diameter tees are the same. Figures 2-2-7 and 2-2-8 show the schematic of concentric reducers; concentric reducers are depicted as isosceles trapezoids or isosceles triangles, and these two representations have the same meaning. Figure 2-2-8 shows the eccentric large and small ends. If the pattern of the eccentric reducing fitting in the plan view is the same as that of a concentric reducing fitting, the word \"eccentric\" must be indicated in writing to avoid confusion. Figure 2-2-9 shows several ways of representing valves: handle facing forward, handle facing backward, handle facing right, handle facing left. Figure 2-2-9 2. Accumulation of pipes: Accumulation of elbows: An elbow consists of a straight pipe section and an elbow fitting. After accumulation along the straight pipe, a small circle is formed; the elbow connected to the straight pipe also results in a small circle as its projection before the bend, and this projection coincides with the one formed by the accumulation along the straight pipe, as shown in Figure 2-2-10. Figure 2-2-10: Accumulation at the elbow. As shown in the plan view on the right side of Figure 2-2-10, first the break point of the right vertical pipe is visible; this pipe is represented by a small circle. Next, the horizontal pipe can be seen, with the straight line representing it drawn to the edge of the small circle. Then the left vertical pipe, which curves downward, appears; however, in the plan view only the projection of the back side of the elbow is shown, so the horizontal pipe is drawn to the center of the circle representing the left vertical pipe. From the plan view, the projection of the straight pipe connected to the valve appears to be just a valve without any pipes; in reality, the small circle formed by the accumulation of the straight pipe overlaps with the projection of the valve’s inner diameter, as shown in Figure 2-2-11. The single-line diagram showing the connection between the straight pipe and the valve is essentially just a plan view of the valve itself. The valve is connected to the elbow; first, the back side of the elbow can be seen, and then the valve in Figure 2-2-11. The standpipe section is not visible on the plan; the small circle it forms is covered by the projection of the elbow, as shown in Figure 2-2-11. On the plan, a horizontal pipe line is first seen, and the standpipe that bends downward on the left side is connected to the valve; at this point, the horizontal pipe is drawn to the center of the small circle representing the standpipe and the valve. The riser goes downward and then turns forward; in the elevation view, what is seen is a cross-section of the pipeline running back and forth, appearing as a small circle. 3. Overlap of pipes: When two pipes of the same length are overlapped, their projections coincide completely; on the projection plane, it appears as if there is only one pipe’s projection. This phenomenon is known as overlap of pipes. Method of representing two overlapping straight pipes: As shown in Figure 2-2-12, when two pipes overlap in the projection, it is assumed that the front (upper) pipe has had a section removed from its upper part and lower part (with a break symbol added), thereby revealing the rear (lower) pipe. Using this method, two or more overlapping pipes can be clearly displayed, as illustrated in Figure 2-2-12. This method of representing pipelines is called broken-line display. As shown in Figure 2-2-13, it is a plan view of two pipelines, one bent and the other straight, overlapping each other. High (front) Low (back) High (front) Low (back) High (front) Figure 2-2-13: As shown in the left figure, the bent pipe is at a higher level than the straight pipe; no break symbol is needed – it is sufficient to separate the bent pipe from the straight pipe by 3–4 mm to indicate that they are not at the same elevation. As shown in the figure on the right: when the bent pipe is below the straight pipe, a break symbol is generally used to break the straight pipe, thereby revealing the bent pipe. Representation of multiple overlapping pipelines: As shown in Figure 2-2-14, the lowest pipe, the second-lowest pipe, and the highest pipe. Figure 2-2-14 4. Pipe intersections: Intersecting pipelines often appear in drawings; these occur where the projections of the pipelines intersect. If the projections of two pipelines intersect, the higher pipeline should generally be displayed in its entirety, while the lower pipeline should be shown as broken. See Figure 2-2-15. Figure 2-2-15 Intersection of multiple pipelines: As shown in Figure 2-2-16, it is a plan view formed by the intersection of the projections of four pipelines, namely a, b, c, and d. In the diagram, tube C being disconnected reveals tubes B and D; tube D being disconnected reveals tube B; when tubes A, B, C, D, and B are disconnected, tube A is visible. Therefore, the order from top to bottom should be a, b, d, c. Figure 2-2-165: Reading pipeline projection drawings: A: Steps and methods for viewing: (1) Examine the view and imagine the shape: After obtaining a plan view of the pipelines, it is necessary to determine how many views are used to represent the shape and direction of these pipelines. By looking at the elevation views or side elevation views, one can understand the relationship between the plan view and the elevation views, and then imagine the general outline of these relationships. (2) Lines and relationship identification: After visualizing the general outline of the pipelines, the relationships between various views can be determined by analyzing the lines (that is, the projection relationships), in order to identify the corresponding projection relationships between the views, especially those involving stacked, overlapping, or intersecting pipelines. (3) Consider the whole as a whole: After understanding the shapes of the various parts in each view, combine them based on their corresponding projection relationships to form a complete understanding of all the pipelines. This allows one to visualize in the mind the three-dimensional shape of the entire pipeline, its spatial orientation, and its overall structure. B. Examples of reading: Example 1: Using the principle of orthographic projection, draw a elevation view from a plan view: as shown in Figure 2-2-17, the pattern of the plan view is known. By applying the methods of \"identifying lines, finding relationships, combining elements, and considering the overall picture\", an analysis of the plan view shows that this pipeline consists of two elbow bends, with its elevation gradually decreasing from left to right. Elevation view, Elevation view, Plan view, Plan view. Figure 2-2-17: Creating an elevation view from a plan view. Figure 2-2-18: Example 2: As shown in 2-2-18, this is a type of diagram that is commonly found in piping installation drawings. Summary: Based on the above guidelines for reading diagrams, the following summary can be made regarding pipe bends: For pipe bends, look at the circles; on floor plans, horizontal pipes bend into circles, while vertical pipes turn into circles as they go downward inside those circles ； On the elevation view, the line turns; the pipes at the front and back become circles, with the line bending backward inside the circle ； The left (right) view tube bends; the horizontal pipeline turns into a circle, with the line bending right (left) as it enters the circle. Practice*: Using the projection principle, draw the elevation view based on the plan view (the length of vertical pipes can be determined arbitrarily). 1, 2, 3, 4, 5, 6, 7, 8, (II) Cross-section of the pipeline: 1. Cross-section of a single pipeline: The characteristics of cut symbols, which can indicate both the line of cutting and the direction of projection, are utilized to represent a certain projection plane of the pipeline. As shown in Figure 2-2-19, the pattern depicted in B A A B A――A B――B corresponds, from the perspective of the three-view projections, to the front view; whereas the B-B sectional view represents the left view. 2. Cross-section view between pipelines: Between two or more pipelines, it is assumed that a cutting plane is used to cut through them; then all the pipelines located in front of this cutting plane are removed, and the remaining pipelines are projected again. The resulting projection is known as the cross-section view between pipelines. As shown in Figure 2-2-20 A A A–A cross-section, Figure 2-2-20 3: Cross-section showing the bend between pipelines: A cross-section obtained by using two parallel cutting planes to cut through the pipelines is called a cross-section showing the bend. As shown in Figure 2-2-21, cross-section A A A–A. Figure 2-2-21: Exercise *1. Draw the A–A and B–B cross-sections based on the plan view; B A A B. 2. Based on the cutting symbols in the plan view, draw the corresponding plan views: A A. V. Painting for corrosion prevention and insulation work: (I) Units of measurement for the project: For painting and corrosion prevention work, equipment and pipelines are measured in units of “10 m2”, while metal structures are measured in units of “100 Kg”. 2 In insulation engineering, the insulation layer is measured in units of “m3”. The moisture barrier and protective layer are measured in units of “10 m2”. (II) For computing the volume of work required for corrosion protection on the inner walls of pipelines in computing equipment, when the wall thickness is 10 mm or more, the calculation is based on the inner diameter ； For those smaller than 10 mm, it is calculated based on their outer diameter. (III) Formulas for calculating the volume of work 1: Volume of work for rust removal, painting, and corrosion prevention (1) Various pipe fittings, valves, manholes, and uneven surfaces on pipe ends are already taken into account in the standard rates, and no separate calculation is required. (2) Formulas for calculating the surface area of valves, elbows, and flanges:
Valves: S (m2) = π × D × 2.5D × 1.05 × N
Elbows: S (m2) = π × D × 1.5D × 2π × N/B; the value of B is as follows: B = 4 for 90-degree elbows, and B = 8 for 45-degree elbows.
Flanges: S (m2) = π × D × 1.5D × N

(IV) Quantities required for insulation work
1. Formulas for calculating the volume required for pipe insulation, as well as the areas for moisture-proofing and protective layers:
Insulation volume: V (m3) = π × (D + 1.033δ) × 1.033δ × L
Areas for moisture-proofing and protective layers: S (m2) = π × (D + 2.1δ + 0.0082) × L²

Formulas for calculating the quantities required for insulation of heated pipes:
For single-or double-tube heating (with identical pipe diameters and an angle less than 90 degrees): D = D1 + D2 + (10–20 mm)
For double-tube heating (with identical pipe diameters and an angle greater than 90 degrees): D = D1 + 1.5D2 + (10–20 mm)
For double-tube heating (with different pipe diameters and an angle less than 90 degrees): D = D1 + D2 + (10–10 mm)
Use D as the outer diameter of the pipe to apply the above formulas and calculate the quantities required for pipe insulation, moisture-proofing, and protective layers. 3. Formulas for calculating the insulation, moisture-proof layer, and protective layer for valves: V (m3) = π×(D+1.033δ)×1.033δ×2.5D×1.05N; S (m2) = π×(D+2.1δ)×2.5D×1.05N. 4. Formulas for calculating the insulation, moisture-proof layer, and protective layer for elbows: V (m3) = π×(D+1.033δ)×1.033δ×1.5D×2π×N/B; S (m2) = π×(D+2.1δ)×1.5D×2π×N/B. The value of B is set as follows: B = 4 for 90-degree elbows, and B = 85 for 45-degree elbows. Formulas for calculating the insulation, moisture-proof layer, and protective layer for flanges: V (m3) = π×(D+1.033δ)×1.033δ×1.5D×1.05N; S (m2) = π×(D+2.1δ)×1.5D×1.05N. 6. Pipeline flaw detection: Welding at the ends of low-pressure carbon steel pipes is carried out in accordance with the quality standards for non-destructive testing, but this does not include the task of performing X-ray inspections on the welds. If it is difficult to make calculations before construction, the total number of welds can be estimated based on the length of the pipeline as designed and the number of fittings per 10 meters of pipeline ； By then calculating the number of welds that need to be inspected according to the inspection requirements, the number of films required can be determined. If it is less than one weld joint, it is counted as one weld joint. The number of radiographs required for each weld joint can be calculated with reference to the attached table when no clear rules are specified in the design. After the welding work is completed, the volume of work must be calculated based on the actual number of films used, excluding the number of films required for re-inspection after weld repairs, as specified in the standards. The number of X-ray examinations depends on the type of pipeline and the weld grade. Classification of pipes by material, temperature, and pressure: (GBL235-82) Material, Operating Temperature (°C), Operating Pressure (MPa): I II III IV V Carbon steel ≤370 >370 >32 >10 >10–32 >4–10 >4–10 >1.6–4 >1.6–4 ≤1.6 ≤1.6 – Alloy steel and stainless steel ≤-70 or ≥450 -7–540 Any >10 ->4–10 ->1.6–4 - ≤1.6 -- Aluminum and aluminum alloys Any ---- ≤1.6 Copper and copper alloys Any >10 >4–10 >1.6–4 ≤1.6 – Table for determining the number of welds at pipe ends: Item, Number of welds on 10m of straight pipe (pieces), Number of welds on 10 pieces of fittings, Determined length per pipe (m): Carbon steel, stainless steel, chromium-molybdenum steel, welded low-temperature steel pipes: 1.27 20.6 6.000 Carbon steel coil pipes, DN200–600: 1.56 20.6 6.400 Carbon steel coil pipes, DN700–900: 1.96 20.6 6.400 Carbon steel coil pipes, DN1000–1400: 2.48 20.6 4.800 Carbon steel coil pipes, DN1600–3000: 2.38 20.6 4.800 Stainless steel coil pipes: 2.22 0.6 4.500 Number of X-ray inspections per weld; if not specified, follow the table below: Pipe diameter DN15 20 25 32 40 50 65 80, Number of X-ray inspections: 2 2 2 2 2 2 2 Pipe diameter DN100 125 150 200 250 300 350 400, Number of X-ray inspections: 3 3 4 4 5 5 Pipe diameter DN450 500 600 700 800 900 1000, Number of X-ray inspections: 6 7 8 9 10 12 13 Note: 1. For pipes with a nominal diameter of 80 mm or less, at least two X-ray inspections are required per weld. 2. The effective length of the strip is calculated as the total strip length minus the overlap, which is 25 mm on each side. 3. The number of radiographic inspections for pipe welds = Percentage specified by the pipe grade × Number of welds × Number of inspections. The number of radiographic inspections for welds at each level of the pipeline shall be calculated in accordance with design specifications. If the design does not specify, follow the table below ； ×(GBJ235-82) Number of weld inspections by grade (%) Scope of application: Ⅰ – 100%; Welds that meet higher quality requirements than those specified for grade II. ⅡA – 100%; Fixed joints in Class I and Class II pipes. B – 15%; Rotating joints in Class II pipes (for fixed joints in Class III pipes, the inspection rate is 400/0). ⅢA – 10%; Fixed joints in Class IV pipes. B – 5%; Rotating joints in Class IV pipes. ⅣA – 5%; Welds of aluminum and aluminum alloys in Class IV (for fixed joints, the inspection rate is 150/0). B – Depending on the actual conditions, up to 1% for welds in Class V pipes. Example: In a certain project, there are 400 meters of pipelines with a diameter of Φ219×10, operating at a pressure of 16.0 MPa; there are also 20 pipe fittings. What is the number of X-ray inspections required for these pipelines? Solution: (1) Number of welds on this pipe and its fittings: 1.27×40 + 20×2.06 = 92. (2) The operating pressure is 16.0 MPa; according to the tables, this pipe belongs to Category II. Per the table regarding the number of inspections required, 100% inspection is needed for fixed welds ； Rotate weld joint by 15% ； Under normal construction conditions, the total number of welds is such that fixed joints account for 20% and movable joints account for 80%. The number of items that need to be inspected is: 92×0.2×100% + 92×0.8×15% = 30. (3) Referring to the table of required X-ray films, 4 films are needed for each connection on a Φ219 pipeline; therefore, 4×30 = 120 films are required. Example: In a certain project, there is a 500-meter-long Φ273×11 pipeline, with an operating temperature of 375°C and an operating pressure of 5.0 MPa. There are also 2 pipe fittings; determine the number of X-ray films required for this pipeline.