GB 50873-2013Design code for piping of water supply and drainage in chemical industry (English PDF)

2.0.1 Piping system

A group of pipes connected by multiple pipes divided by fluid and design conditions.

2.0.2 Launder flume

In order to maintain the stability of the flow state and avoid the eddy current caused by the change of the cross section of the water flow, the arc-shaped water tank is set inside the inspection well.

2.0.3 Covered depth

The vertical distance from the buried pipe, the top of the canal to the ground surface.

2.0.4 Buried depth

The vertical distance from the buried pipe, the inner bottom of the canal to the ground surface.

2.0.5 Water hammer surge or water hammer

In the pressure pipeline, the hydraulic shock phenomenon in which the pressure rises and falls alternately due to the drastic change of the flow velocity.

2.0.6 Cathodic protection

It is an electrochemical protection method to prevent pipeline corrosion by using an external anode or DC power supply to protect the metal as a cathode.

2.0.7 Flexible joint of piping

A pipe joint that can withstand a certain amount of axial line displacement and relative angular displacement.

2.0.8 Composite pipe

The pipe wall structure is a round pipe composed of two or more materials.

3.1 General provisions

3.1.1 The division of the water supply pipeline system shall be determined according to the requirements of the device (unit) for water quality, water pressure and water temperature.

3.1.2 The division of the drainage pipeline system shall be classified according to the water quality, following the principles of separation of clean and sewage, and separation of sewage and sewage, and shall be determined according to the water quality, water volume, water pressure and whereabouts of the drainage. Different chemical plants discharge different types of sewage, and separate or combined sewage pipeline systems should be set up in accordance with the principle of easy transportation and treatment. A separate sewage pipeline system should be installed for the following sewage.

1 Sewage mixed with other sewage that is prone to sedimentation, aggregation or generation of refractory biodegradable substances;

2 Sewage containing relatively high concentrations of refractory and biotoxic substances that require targeted treatment;

3 Sewage containing corrosive media such as acid and alkali.

3.1.3 It is strictly forbidden to connect non-fire-fighting water pipes to independent fire-fighting water supply pipes.

3.1.4 The fire water supply system should not be combined with the circulating cooling water system.

3.1.5 The circulating cooling water pipeline should not be connected with other production water supply pipelines.

3.1.6 The reuse water system shall adopt an independent water supply pipeline.

3.1.7 The domestic drainage of the factory should adopt an independent drainage piping system.

3.1.8 Accident fire-fighting drainage pipes in polluted areas such as production units and tank farms can be installed in combination with production sewage pipes and rainwater pipes (canals) or independently, but should not pass through explosion-proof areas; when crossing cannot be avoided, protective measures should be taken.

3.1.9 The quantity and orientation of the inlet and outlet of the water supply and drainage pipes of the device (unit) shall be determined according to the pipeline layout in the device (unit) and the layout of the water supply and drainage pipes of the whole plant.

3.1.10 The installation of sewage pipelines containing flammable liquids shall comply with the relevant provisions of the current national standard "Code for Fire Protection Design of Petrochemical Enterprises" GB 50160.

3.1.11 The setting of fire-fighting water supply pipes and their facilities shall comply with the relevant provisions of the current national standards "Code for Fire Protection Design of Petrochemical Enterprises" GB 50160 and "Code for Fire Protection Design of Buildings" GB 50016.

3.1.12 When the outlet of the gravity flow drainage pipe is supported by the flood or tidal water level of the water body, anti-backflow facilities shall be installed.

3.1.13 The drainage piping system in the plant area shall be equipped with emergency facilities to prevent accidental fire-fighting wastewater from flowing into the environment outside the plant.

3.1.14 Water hammer analysis and calculation should be carried out for pressure transmission pipelines. When the water hammer generated endangers the safety of the pipeline, measures to reduce the water hammer should be taken.

3.2 Piping system

3.2.1 When the main water supply pipe in the factory area is connected to the urban water supply pipeline or the industrial park water supply pipeline, facilities such as shut-off valves and flow meters shall be installed. When domestic water supply may cause backflow pollution, anti-backflow facilities should be installed at the pipe connection.

3.2.2 The setting of valves in the water supply pipeline system should meet the requirements of safe production and maintenance, and valves should be set in the following situations.

1 Connected to the pipeline of the device (unit) by the main pipe.

2 Segmentation and connection of two or more water pipelines.

3 Crossing, the upstream side of a railway or river pipeline.

4 The circulating cooling water feed water and return water pipes are on the connecting pipes set in the adjacent equipment area.

3.2.3 An exhaust valve should be installed at the high point of the pressure flow pipeline, and a vent valve should be installed at the low point.

3.2.4 When a large pressure adjustment is required in the pressure flow pipeline, a pressure reducing valve or a safety valve should be installed. No valve shall be installed before the safety valve.

3.2.5 The inlet and outlet pipes of the water pump should be provided with valves, and the outlet pipe should be provided with check valves. When the valve is connected with an expansion joint, the expansion joint should be fixed with limit bolts.

3.2.6 Valves should be installed at the outlets of production devices, tank area drainage pipes (ditches) and pipe outlets to prevent backflow of drainage.

3.2.7 Drop wells shall not be installed in the pipeline system containing volatile toxic, harmful and combustible gas sewage.

3.2.8 Measuring and monitoring instruments shall be installed at the following positions of the water supply and drainage pipelines.

1 The main pipeline of production and domestic water supply systems should be equipped with measuring instruments, and should be equipped with pressure monitoring instruments; measuring instruments should be installed on the branch pipelines of the access devices (units).

2 The fire water supply piping system shall be equipped with pressure monitoring instruments.

3 Flow, temperature and pressure gauges shall be installed in the main pipe of circulating cooling water supply and the inlet and outlet main pipes of each unit production device; Measuring instruments shall be designed for pipelines and side water pipelines.

4 The production sewage pipeline of the discharge device (unit) should be equipped with metering and sampling facilities, and the outlet pipeline of the factory should be equipped with measuring instruments, on-line testing instruments and sampling facilities according to the requirements of the local environmental protection department.

3.3 Piping arrangement

3.3.1 The plane and vertical layout of water supply and drainage pipes shall be determined according to the plant topography, the general plan of the plant area, the water consumption and drainage of the device (unit), the depth of frozen soil, engineering geological conditions and pipe materials.

7 When the rainwater pipeline is laid above the freezing line, measures shall be taken to prevent soil frost heave from damaging the pipeline and joints.

8 When the pipeline crosses the railway in the factory area, the distance between the top of the pipeline and the bottom of the railway track shall not be less than 1.2m, and shall comply with the relevant regulations of the railway industry.

9 When the pipeline crosses the green belt, the minimum soil covering depth of the pipeline shall meet the freezing requirements of the pipeline.

3.3.12 The buried water supply and drainage pipes should not be arranged under the ground where heavy objects are piled up. The pipeline shall not pass through the foundation of the production equipment; when passing through under special circumstances, protective measures shall be taken.

3.3.13 Water supply and drainage pipes shall not pass through the column foundation of buildings (structures); they shall not pass through the expansion joints and settlement joints of buildings (structures). When it cannot be avoided, compensation facilities such as bellows, short rubber pipes and compensators should be provided.

3.3.14 When the pipeline passes through the load-bearing wall or foundation of the building (structure), holes should be reserved, and the height of the hole should ensure that the clearance at the top of the pipe should not be less than the settlement of the building, and should not be less than 0.15m.

3.3.15 Safety protection measures should be taken for plastic pipes installed outdoors.

3.3.16 The expansion and contraction compensation amount of the water supply pipeline arranged overhead shall be calculated and determined according to the linear length of the pipeline, the linear expansion coefficient of the pipeline, the ambient temperature, the change of the water temperature in the pipeline and the allowable displacement of the pipeline nodes.

3.3.17 Indoor water supply and drainage pipes shall not be laid in flue ducts, air ducts, elevator shafts, and drainage ditches, and shall not pass through firewalls and explosion-proof walls, and shall not be arranged in places where the ambient temperature is lower than 4°C or higher than 70°C.

3.3.18 Indoor water supply and drainage pipes should not pass through rooms where water will damage equipment and cause accidents, such as power transformer and distribution room, control room, elevator machine room, communication machine room, large and medium-sized computer rooms, and audio-visual warehouses; Chromatography room and other rooms pass through; it must not be arranged on places or equipment that may cause fire or explosion when exposed to water.

3.3.19 Indoor overhead drainage pipes shall not be laid in production plants or valuables warehouses that have special requirements for production technology and sanitation; drainage pipes shall not pass through the top of the drinking water pool.

3.3.20 When water supply and drainage pipes pass through roofs or floors, waterproof measures shall be taken; water supply and drainage pipes shall be provided with waterproof casings when passing through the following parts.

1 The outer wall of the basement or underground structure.

2 pool wall.

3 Reinforced concrete well chamber.

4.1 General provisions

4.1.1 Water supply and drainage pipes should be equipped with auxiliary facilities and corresponding structures according to the use function and needs.

4.1.2 The well chamber size of various functional wells shall meet the requirements for equipment installation, maintenance and maintenance.

4.1.3 The design of the well chamber shall meet the following requirements.

1 For valve wells, instrument wells, and underground fire hydrant wells whose groundwater level is higher than the bottom of the well, reinforced concrete well chambers should be used, and sumps should be set at the bottom of the well.

2 Reinforced concrete well chambers should be used for inspection wells, water sealing wells, and water drop wells of production sewage pipelines.

3 Reinforced concrete well chambers should be used for inspection wells and septic tanks of domestic sewage pipelines.

4 For transporting corrosive sewage, the well chamber should be treated with anti-corrosion treatment, and fixed ladders are not allowed in the well.

5 Waterproof casings shall be installed where the pipeline passes through the wall of the reinforced concrete well.

4.1.4 The material of well cover, well seat and step can be ductile iron, steel fiber concrete and polymer composite material.

4.1.5 Valve wells, instrument wells, and underground fire hydrant wells in cold regions should use inner thermal insulation well covers.

4.1.6 Heavy-duty manhole covers and well seats should be used for well chambers under the roadway; light manhole covers and well seats should be used for well chambers in sidewalks and green belts. The manhole cover on the roadway should be level with the road surface; the manhole cover on the sidewalk should be 0.05m above the ground; the manhole cover in the green belt should be 0.20m above the ground.

4.1.7 Pipelines containing flammable liquids or toxic gases that may cause fires, explosions, and poisoning accidents in sewage shall be installed in accordance with the relevant provisions of the current national standards "Code for Design of Fire Prevention in Petrochemical Enterprises" GB 50160 and "Code for Design of Outdoor Drainage" GB 50014 Corresponding ancillary structures and safety facilities.

4.2 Valve wells, fire hydrant wells

4.2.1 The size of the valve well shall meet the following requirements.

1 When the valve diameter is less than or equal to 300mm, the distance from the outer edge of the valve flange to the well wall should not be less than 400mm, and the distance to the bottom of the well should not be less than 300mm.

2 When the diameter of the valve is greater than 300mm, the distance from the outer edge of the valve flange to the well wall should not be less than 600mm, and the distance to the bottom of the well should not be less than 400mm.

3 For vertical valve wells operated underground, when the valve is at the maximum opening, the distance from the highest point of the valve to the inner top of the well cover should not be less than 300mm.

4 When installing valves and expansion joints in the valve well, the installation and maintenance requirements of the valves and expansion joints should be met at the same time.

4.2.2 The size of the fire hydrant well shall meet the following requirements.

1 The distance from the center of the hole of the underground fire hydrant to the well wall shall not be less than.200mm.

2 The distance from the mouth of the underground fire hydrant to the well cover should be.200mm-400mm.

3 The distance from the socket edge of the water supply socket pipe to the well wall should not be less than 400mm.

4 When the pipeline is connected by flanges, the size of the well chamber shall meet the relevant requirements for flange installation in the valve well in Article 4.2.1 of this code.

4.3 Inspection well

4.3.1 Gravity flow drainage pipes shall be provided with inspection wells at regular intervals at intersections, bends, pipe diameter or slope changes, water drops and straight pipe sections. The maximum spacing of inspection wells on straight pipe sections should not be greater than those specified in Table 4.3.1.

Table 4.3.1 Maximum spacing of inspection wells on straight pipe sections

4.3.2 The size of the inspection well shall be determined according to the number, diameter and depth of the drainage pipes connected to it. When the diameter of the branch pipe connected to the inspection well is greater than 300mm, there should not be more than 3 branch pipes.

4.3.3 Launders should be installed at the bottom of inspection wells. The top of the chute of the sewage inspection well should be level with the diameter of 0.85 times the large pipe, the top of the chute of the rainwater or clean wastewater inspection well should be level with the place of 0.5 times the diameter of the large pipe, and the bending radius of the centerline of the chute at the corner of the pipe should not be less than Large pipe diameter.

4.3.4 It is advisable to set up sedimentation tanks in the inspection wells at appropriate distances on the drainage pipes in the factory area. In the inspection wells before the lifting pump station and the inverted siphon inlet wells, the sedimentation tanks should be set up. The depth of the sedimentation tanks should be 0.3m~ 0.5m.

4.3.5 In Category A and B process units, exhaust pipes should be installed at the top inspection wells of production sewage branch pipes and main pipes containing flammable liquids in Category A and B tank farms, and the arrangement of exhaust pipes should comply with the current national Relevant provisions of the standard GB 50160 "Code for Fire Protection Design of Petrochemical Enterprises".

4.3.6 The joints between the manhole cover and the well seat of the following sewage pipeline inspection wells shall be sealed, and the manhole cover shall not have holes.

1 Production sewage pipes in Class A and Class B process units.

2 Production sewage pipelines in Type A and Type B tank farms.

3 Pipes that emit toxic and harmful gases that may cause fire, explosion, and poisoning accidents.

4.3.7 Underground sewage pipes and sludge pipes for pressure conveyance should be provided with pressure inspection wells.

4.4 Water seal well

4.4.1 The setting of water seal wells shall be carried out in accordance with the relevant provisions of the current national standards "Code for Fire Protection Design of Petrochemical Enterprises" GB 50160 and "Code for Design of Outdoor Drainage" GB 50014.

4.4.2 The water seal height of the water seal well should not be less than 250mm.

4.4.3 The bottom of the water-sealed well should be provided with a sedimentation tank, and the depth of the sedimentation tank should not be less than 0.3m.

4.4.4 The head loss of the water-sealed well shall not be less than 0.05m.

4.4.5 Water sealing wells should not be set on the roadway, should avoid pedestrian passages, and should be far away from places where open flames may occur.

4.5 Drop wells

4.5.1 The setting of the drop well shall meet the following requirements.

1 When the drop water head is 1.0m~2.0m, drop wells should be installed.

2 When the falling water head is greater than 2.0m, a falling water well shall be provided.

4.5.2 It is not advisable to set a drop well at the turning of the pipeline.

4.5.3 The drop head height of the drop well shall meet the following requirements.

1 When the diameter of the water inlet pipe is not greater than.200mm, the head height of one drop should not be greater than 6m.

2 When the diameter of the water inlet pipe is 300mm-600mm, the height of the water head for one drop should not be greater than 4m.

3 When the diameter of the water inlet pipe is greater than 600mm, the height of the water head and the way of the water drop should be determined according to the hydraulic calculation.

4.6 Gullies

4.6.1 The layout of storm water outlets should be determined according to catchment area, road form, vertical layout and terrain conditions.

4.6.2 The distance between storm water outlets should be 25m~50m. When the longitudinal slope of the road is greater than 0.02, the distance between gullies can be greater than 50m. When the slope is short, water can be collected at the lowest point.

4.6.3 The form and quantity of the gullies shall be determined according to the catchment volume and the drainage capacity of the gullies. For rainwater outlets that are easily blocked by debris during heavy rain, the drainage capacity should be multiplied by a coefficient of 0.5 to 0.7.

4.6.4 When the gully outlets are connected in series, there should be no more than 3, and the length of the gully outlet connecting pipe should not exceed 25m.

4.6.5 The diameter of the connecting pipe between the rainwater outlet and the inspection well shall be calculated and determined according to the number of connected rainwater outlets and the discharge volume.

4.6.6 The depth of the rainwater outlet should not be greater than 1.0m, and a sedimentation tank should be provided as required. Reinforcement measures should be taken when shallow burial is required, and the depth of gullies in areas affected by ice swelling can be determined according to local experience.

4.7 Inverted siphon

4.7.1 When installing inverted siphons for pipelines crossing river courses and important obstacles, they shall comply with the relevant provisions of the current national standard "Code for Design of Outdoor Drainage" GB 50014.

4.7.2 The design of the inverted siphon in the factory area shall meet the following requirements.

1 The minimum pipe diameter should not be less than.200mm.

2.The flow velocity in the pipe should be greater than 0.9m/s. If the requirements cannot be met, regular flushing facilities should be added.

3 The inverted siphon should be made of metal pipe and should be treated with anti-corrosion treatment.

4 Measures should be taken to prevent uneven settlement at the joints of the inverted siphon inlet and outlet wells and pipelines.

5 The inverted siphon should be provided with an emergency outlet.

4.8 Water outlet

4.8.1 The location and form of the outlet of the drainage pipe (canal) shall be determined according to the discharge water quality, flow rate, function of the receiving water body, water level, local geology and climate and other conditions.

4.8.2 Outlets of drainage pipes (canals) should have anti-scouring, energy dissipation, reinforcement and other measures, and obvious signs should be set up where the outlet pipes extend into the water body.

4.8.3 Anti-frost measures shall be taken for water outlets in areas affected by frost heave. The outlet foundation should be set below the freezing line.