Quality control of pipeline system installation

With the acceleration of industrialization, all sectors of society are showing vigorous vitality. In this historical environment, industrial pipelines have developed rapidly and the scope of application has gradually expanded. How to carry out effective installation quality control has become particularly important. This paper will focus on the key technologies and quality control measures of pipeline system installation, so as to further improve the quality of pipeline construction, accelerate the development of pipeline industry, and provide effective reference for relevant work in the future.

20220208111555 29953 - Quality control of pipeline system installation

Quality control of pipe installation

1. Must be familiar with the process of this position, the flow direction of the process pipeline and the installation direction of the valve.

2. The pipe, valve orchid, should be checked one by one for its material, specification, type and quality before use, and those who do not meet the design requirements and quality should not be used; at the same time, the pipe, pipe fittings, should be inspected for appearance, and there should be no cracks, shrinkage, slagging, sand sticking, heavy skin and other defects.

3. Pipe installation, the flange sealing surface and sealing piece should be inspected for appearance, there shall be no defects affecting the sealing performance exists.

4The flange shall be kept parallel when connected, and its deviation shall be no more than 1.5/1000 of the outer diameter of the flange, and no more than 2. The skew shall not be eliminated by the method of strong tightening bolts.

5The gasket can be installed with graphite powder, molybdenum disulfide grease, graphite oil and other coating agents respectively as needed.

6. Flange connection should use a specification bolt, installation direction consistent. When tightening the bolts, should be symmetrical and uniform, loose and tight, the length of the exposed at the tightening is not more than 2 times the pitch.

The distance between the two welds of the straight pipe section is not less than 100; the distance between the welds and the starting point of the bent pipe is not less than 100, and not less than the outer diameter of the pipe; no hole shall be opened in the pipe welds.

7. The pipeline on the instrumentation contact opening and welding should be carried out before the installation of the pipeline.

8. Pre-buried casing to be accurate, while other pipes should be considered not to prevent compensation.

9. In the construction of strict control of the instrument air pipe welding must be used argon electric coupling welding.

Valve installation quality control

1. The valve should be checked before installation, the valve should have the manufacturer’s nameplate, the nameplate should indicate the nominal pressure, nominal through, working temperature and working medium and other relevant instructions.

2. The appearance should be inspected before installation and should not be damaged, rusted, missing parts, dirty, name plate off and color code discrepancy.

3. The handle or handwheel of the valve should be operated flexibly and lightly, no jamming phenomenon unqualified shall not be installed.

4. The general valve body has a sign on the valve body, the arrow points to the direction of the forward flow of the medium. Special care must be taken not to install the reverse.

5. Installation location from the operation and maintenance focus, as far as possible to facilitate the operation and maintenance, the valve hand wheel shall not be down.

6. Large valve lifting, the rope can not be tied to the handwheel or stem.

Pipe welding quality control

1Oxygen-acetylene welding is adopted for carbon steel pipe with outer diameter less than or equal to 57and wall thickness less than or equal to 3.5. The outer diameter greater than 57adopts argon-electric coupling welding and then manual electric arc welding. Stainless steel pipe using manual electric arc welding.

2. Welding auxiliary equipment should have: welding rod drying box, welding rod insulation barrel, oxygen reducer, acetylene reducer, oxygen bottles, acetylene bottles, temperers, etc..

3. Carbon steel and low alloy steel pipe bevel using mechanical or oxyacetylene flame, mechanical method to remove the oxide skin, etc. for processing.

4. Check that the paint, scale, rust, burr, etc. on the surface of the bevel and the inside and outside of the edge of the bevel are cleared within not less than 10, and there shall be no cracks, laminations and other defects.

5. The bevel processing size meets the requirements; the surface of the weld mouth should be free of cracks and interlayer. Pipe end 10-20mm inside and outside wall without paint, oil, rust, and polished to a metallic luster. Pipe weld mouth group should be flush with the inner wall, the amount of the wrong side of the inner wall shall not exceed 10% wall thickness, and not more than 2mm.

6. After welding the pipeline, the weld must be inspected for appearance, inspection should be cleaned before the slag skin, spatter that prevents inspection. Non-destructive testing of the weld, its failure parts must be repaired after still need to be tested according to the original method.

Anti-corrosion quality control

1. Equipment and pipelines must be combined with a sander and manual rust removal to remove the rust, and use cotton yarn and cloth to remove the surface floating rust and apply anti-rust paint.

2. Oil two anti-rust paint must wait for a paint dry, and to ensure that the surface is clean paint the second time, oil top coat the same.

3. Paint must be lifted evenly brushed on the metal surface, to prevent leakage, flower coating, flow hanging, biting bottom, back to paste, wrinkles and other effects of anti-corrosion;.

4It is strictly forbidden to construct in rain, snow, fog and environment with high relative humidity.

Anti-corrosion and insulation standards

The construction requirements of anti-corrosion and insulation projects

  1. The thickness of the equipment and pipeline insulation is calculated according to the medium temperature of the equipment and pipeline, the thermal conductivity of the insulation material and other parameters, plus a certain amount of insulation margin (insulation thickness reference table).
  2. The composite silicate sheet is used to lay insulation layer, more than two layers of construction, need to apply bonding agent bonding layer by layer, the bonding agent is applied evenly, each layer. Seams should be evenly staggered, there shall be no lack of flesh between the layers, the inner and outer joints staggered 100-150mm, and fill all the gaps and interfaces with binder, and finally on the protective layer. (Can not be timely on the protective layer, the surface using plastic film winding to prevent insulation material moisture.)
  3. The pipe insulation using composite silicate pipe, with adhesive to fill the pipe gaps and interfaces smoothed, and finally on the protective layer. (Can not be timely on the protective layer, the surface using plastic film winding, to prevent moisture insulation materials.)
  4. The longitudinal seam position of the metal protection layer of the horizontal pipeline should be arranged at the horizontal centerline450150, with the seam opening facing downward. When there is an obstacle on the side or bottom, the longitudinal joint can be moved to the horizontal center line above.600
  5. After insulation, according to the surface temperature of the protective layer is not greater50 than (ambient temperature of 25 ) acceptance
  6. When the equipment and pipes are kept cold, then a layer (δ = 30mm) is laid with rubber material, first fill all the gaps and interfaces with special glue and apply evenly, then bundle with self-adhesive tape, and the surface is required to be smooth and round.
  7. According to the average28 temperature of the hottest month , the relative7 humidity of the hottest month 3%, the corresponding dew point temperature of the surface of the insulation layer is 23. (Note: the surface of the insulation layer does not condense, subject to)

The general thickness of the insulation and cooling layer

Temperature (unit ) (holding)

Thickness (in mm)



















Temperature (unit ) (cold retention rubber and plastic)

Thickness (in mm)












(A). The site for anti-corrosion construction, the project unit should be sent by the section leader to monitor the quality of the site, the quality of each process must be signed by the section leader to confirm before the next process

(B). Major anti-corrosion project for construction, engineering construction unit should be combined with the construction project, written construction plan or construction technology description, after approval of the implementation.

(C). The section chief should be used for anti-corrosion construction unit inspection of raw materials (paint, etc.), including manufacturing plants, product quality inspection certificates, certificates of compliance, construction materials and wash material ratios.

(D). Equipment, pipeline surface rust removal inspection standards.

  1. After rust removal, the metal surface should be free of oxidation, rust, welding slag, dust, paint, and metallic luster.
  2. The quality of metal surfaces such as hand or power tools for rust removal, sandblasting, etc. is according to GB 8923-88“Steel surface rust prevention grade and rust removal grade before painting”, and special requirements are according to the design requirements.
  3. At the corner of the metal surface, where the power tool is not suitable for complete derusting, it must be derusted manually or with special tools until it passes the acceptance.

(E). The inspection of the paint.

  1. After coating, it should be even and consistent in color.
  2. The product should be firmly attached, no flaking, wrinkles, pinholes and other defects.
  3. Should be complete, no damage, no flow.
  4. The thickness of the final coating should meet the requirements of the program.

(F). The construction environment: paint construction should be below 15~ 30temperature, the environment of high humidity should take protective measures to carry out. Rainy weather, pipeline surface below the atmospheric temperature shall not be constructed.

(G). The type of paint, color, layers and markings should be in line with the program requirements of the equipment pipeline


In the construction quality inspection and assessment, the inspection of sub-projects is the basis for quality control and quality assessment. Sub-engineering inspection projects are divided into3 classes according to the provisions: a class for the assurance project; content to ensure the safety of the project and the use of the function, the quality of the project has a decisive impact on the inspection project; two classes for the basic project, the content to ensure the safety of the project and the use of the function, the quality of the project has an important impact on the inspection project; three classes for the allowable deviation project, the content of the test allows a small number of test points in the standard proportion of the range The third category is the allowable deviation project, content in the test allows a small number of test points in the standard proportion of the range, can still meet the project safety and use of the test project.

To ensure the quality of the project inspection.

1. Material inspection (inspection of its factory material certification, if necessary, on-site sampling sent for inspection, performance test report).

  • (1) Material, specification and performance of insulation materials and products.
  • (2) Materials, specifications and performance of cold retention materials and products.
  • (3) Binder, preservative, sealant performance.
  • (4) The material, specification and performance of the protective layer material and products.
  • (5) Whether the material of fixed parts and supporting parts matches the material of equipment and pipeline.

2. Insulation layer inspection

  • (1). Layered construction of thermal insulation layer: check whether layered construction is carried out when the thickness of thermal insulation layer is greater than 100mm or the thickness of cold insulation layer is greater than 80mm.
  • (2). Inspection equipment nameplate: insulation construction shall not cover the equipment nameplate.
  • (3). Cold insulation check: fixed parts are strictly prohibited to penetrate the cold insulation layer; support hangers, bearing parts, bearing boarding parts should be equipped with hardwood blocks dipped in asphalt; seal treatment should be done between the demountable structure and fixed structure; the outside of the expansion joints should be re-insulated, etc.
  • (4). The heating space of the tracing tube and the main tube is strictly prohibited to be blocked.
  • (5). Filling insulation structure shall not have filler bridging and leakage plugging phenomenon.
  • (6). The inspection of expansion joints: the use of rigid products to do insulation layer need to stay according to the design requirements of expansion joints; multi-layer insulation layer laid, each layer expansion joints should be staggered.
  • (7). Using masonry, pouring, spray construction insulation layer, should be masonry mortar material, pouring
  • and spraying materials and ratios for inspection. If necessary, test blocks can be made and sent for inspection.

3. Moisture-proof layer inspection

  • (1). The moisture barrier material material, performance checks, whether its factory certificate of compliance with the design requirements, if necessary to take samples sent for inspection.
  • (2). The tightness and integrity of the damp-proof layer laying, there shall be no leakage of laying and gap existence.

4. Protective layer inspection

  • (1). The protective layer is laid, and each joint is lapped up and down in the direction of the following water flow.
  • (2). The metal protective layer, composite products hard protective layer construction, damage to the moisture-proof layer is strictly prohibited.
  • (3). The expansion joints of metal and hard protective layer are strictly forbidden to have fixed parts.

The quality inspection of basic items.

1. Fixed parts, support parts installation inspection
After the installation of fixed parts and supporting parts, check whether their solidity meets the design requirements and check them against the following.
(1)Fixed parts installation quality requirements

Inspection items

Insulation layer

Quality requirements

Hooks and pins

Insulation layer

There shall be no less than 6 sides and 8 bottoms per square meter, with a spacing of no more than 350mm

Cooling layer

There are 4 fixings in each piece, and the length shall be 10mm less than the thickness of the cold insulation layer, but not less than 20mm

(2). The distance between the installation of the support parts

Inspection items

Insulation layer

Spacing requirements


Support plate

Support ring

Insulation layer

Vertical equipment and D > 100mm vertical pipeline; The flat wall is 1.5 ~ 2m; Cylinder: 2 ~ 3M at high temperature and 3 ~ 5m at medium and low temperature. The width of the support shall not be less than 10mm, but not less than 20mm

Cooling layer

Flat-walled, round tanks and pipes shall not be larger than 5m, and the width and structure of the supporting members shall be in accordance with the design provisions

Support ring

Soft goods

Horizontal and vertical position, protective layer support ring installation spacing of 0.5 ~ 1m, the structure should be in line with the design provisions

2. Insulation layer inspection

(1). Insulation material spacing, seam width and laying requirements

Inspection items

Insulation layer

Seam width/mm

Laying requirements


Insulation layer


Staggered seams on the same layer, pressed seams on the upper and lower layers, corner seams are capped lap seams

Cooling layer


(2). Bundling spacing and requirements

Inspection items

Thermal insulation products

Thermal insulation object

Strapping distance/ mm

Bundling requirements





Firmly tied

Wire head wrenching, embedded, each piece of product bundling not less than the 2 turns









(3). Other inspection of insulation layer

Inspection items

Inspection object

Quality requirements


Insulation rope

Wrapping rope tightly against each other, no loose, multi-layer pressure seam

Jedi Tropics

The lap is 1/2 of the bandwidth, tightly wound, and multi-layer crimped


solid layer

The solid layer and anti-sink layer are set correctly, and the filling material is close to the workpiece


Insulation layer

Firmly pasted, with regular and tight seams

Cooling layer

The paste is firm, the spelling seam is neat and tight, and the equipment support, pipe hanger and cold layer paste meet the requirements.

Pouring, spraying

Polyurethane foam

Paste firmly, no peeling, brittle, shrinkage, soft and foam red phenomenon

Lightweight granules

Uniform thickness, no honeycomb, hollow, obvious shrinkage, cracking phenomenon

Detachable construction

Insulation layer

Insulation products installed flat, squeezed solid, solid, and easy to install and remove

Cooling layer

In addition to meeting the requirements of the insulation layer, the joints and corner joints are tight, and the sealing treatment is good

Expansion joints

Insulation layer for rigid products

Set up the correct position, no impurities in the seam, filler plugging tightly, tied firmly, expansion joints outside the insulation layer, firmly laid

3. Moisture-proof layer inspection

Inspection items

Inspection object

Quality requirements




Moisture barrier

The lap amount is 50mm, the seam mouth is facing down, the lap is dense and continuous

Each layer thickness 5mm, no bubbles, warping, delamination, cracking and other defects

4. Protective layer inspection

(1). Metal and FRP protective layer lap

Inspection items

Inspection object

Overlap size/ mm


Indoor equipment and piping

General parts 20, expansion joints 50

Open air or wet environment

General parts 50, expansion joints 75

Elbow and straight pipe lap joint

75~150 at high temperature, 50~70 at medium and low temperature, 30~50 for keeping cold

Equipment flat wall surface plugging


(2). Appearance and seam inspection

Inspection items

Inspection object

Quality requirements


Metal protection layer

No flanges, openings and obvious pit defects

Composite protective layer

No loosening, flanging, gaps, bubbles and other defects

Plastered protective layer

No dry shrinkage cracks, surface flakiness, no exposed wire head


Metal protection layer

The position of the joints meets the design requirements

Composite protective layer

Paste tightly and firmly, in line with the design requirements

(3). Plastering layer expansion joints left to test

  • a. high-temperature pipe smear layer of broken joints, and insulation layer expansion joints remain in the same location.
  • b. outdoor plastered layer of the expansion joint parts, the surface covered with metal sheathing or take other waterproofing measures.
  • c. large equipment plastering, leaving a square or ring-shaped groove, the width and depth of the groove should meet the design requirements.

The quality inspection of the allowable deviation items.

Inspection items

Inspection object

Allowable Deviation

Inspection method


Rigid insulation

+10mm, -5mm

ruler measurement

Semi-rigid, soft insulation

+10mm, -5mm,and ≤10mm, ≤-10mm

Needle pricking, ruler measurement

Cooling layer


Needle pricking, ruler measurement

Installation density

Hard and semi-hard products


Sampling and weighing

Soft goods


Sampling and weighing


Moisture barrier


Scale or wedge

Protective layer


Plug gauge inspection


Expansion joints


Plug gauge inspection

The number of inspection provisions

1. Insulation, cooling materials and their products, binders, abrasion inhibitors, sealants and other materials, materials, performance checks on the number, according to the following provisions.

  • a. from each batch of incoming materials, according to different materials, performance, specifications, respectively, a random sampling inspection, sample size can be determined by the construction unit and supply manufacturers in consultation.
  • b. if one of the results of the sampling test is unqualified, another sampling retest is allowed.
  • c. the re-inspection still has an indicator failed, the batch of product quality should be judged as unqualified. However, the performance inspection of the material or product should be the same sample of all performance inspection.

2. The number of inspection should be 100% of the material, specification and variety of the fixed parts and supporting parts of the insulation structure.

3. Insulation layer, moisture-proof layer, the number of protective layer inspection is carried out as follows.

  • a. When the equipment area is every 50 ㎡ or less and the pipeline length is every 50 m or less, three spots shall be spot checked; Each inspection area of equipment is 0.5 m2, and there are no less than 3 inspection points for equipment and pipeline. When the area of the same equipment exceeds 500 ㎡ or the length of the same pipeline exceeds 500 m, the distance between the sampling inspection points can be appropriately increased. The average value of inspection points at each inspection office represents its construction quality.
  • b. The inspection quantity of removable thermal insulation structure is 3 for every 50 or less.
  • c. If one of the quality inspection places is unqualified, double the inspection place within 300m around the unqualified place for recheck. If there is still one unqualified place, it shall be deemed as unqualified.
  • d. The unqualified works of the inspection items of subdivisional works can be ordered to rework or modify. The reworked or modified works can be inspected and evaluated again.

China Pipeline System Manufacturer – Yaang Pipe Industry Co., Limited (www.pipelinedubai.com)

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