Shanghai Hongguan alloy flange is an indispensable detachable pipeline sealing connector in the entire industrial water treatment, sewage treatment, pure water purification, and reclaimed water reuse equipment pipeline system. It is also a core accessory for water treatment equipment assembly, pipeline docking, and equipment maintenance. Whether it is integrated sewage equipment, RO reverse osmosis pure water equipment, circulating cooling water systems, or dosing and anti-corrosion pipelines, pump room boosting pipelines, flanges are responsible for the core functions of pipeline connection, pressure sealing, disassembly and maintenance. Many water treatment projects have problems with leakage, interface corrosion, and pressure cracking due to improper flange model, material, and sealing surface selection. This article comprehensively explains the application, classification, material selection, and usage precautions of flanges in water treatment equipment, helping to avoid pitfalls in project selection.

1、 The core function of the water treatment flange is to adapt to the exclusive working conditions of water treatment

Different from ordinary pipeline flanges, water treatment special flanges are suitable for water containing, acid-base agents, sediment impurities, high and low pressure water flow, and long-term humid and corrosive conditions. The five core functions support the stable operation of the system:

1. Detachable docking:Replace welding fixed connections, facilitate pipeline disassembly, equipment dismantling, tank maintenance, pipeline dredging and renovation, and meet the needs of regular cleaning, membrane replacement, and sewage maintenance of water treatment equipment;

2. Sealing and leakage prevention:Equipped with specialized gaskets to isolate water bodies and prevent the outflow of chemicals, and to prevent the leakage of sewage, pure water, and acid-base chemical pipelines, meeting the requirements of environmental protection, anti-seepage, and pure water cleanliness;

3. Pressure resistance and deformation resistance:Adapt to high-pressure reverse osmosis pipelines and pump outlet high-pressure water flow, counteract water flow pressure and pump body vibration, and avoid interface cracking and detachment;

4. Suitable medium anti-corrosion:Multiple materials to choose from, suitable for different water qualities such as raw water, sewage, acid-base agents, ultrapure water, etc., to prevent flange corrosion and pollution of water bodies;

5. Standardized adaptationNational standard universal specifications, compatible with water pumps, membrane housings, filters, tanks, valves, flow meters and other water treatment accessory interfaces, with strong universality.

2、 Common installation and application positions of flanges for water treatment equipment

The entire water treatment system covers the entire process from inlet, filtration, purification, discharge to reuse, with flange coverage applied at all points. The core usage scenarios are as follows:

1. Pipeline segmentation docking position

The main water pipeline, sewage pipeline, circulating water branch pipeline, and concentrated water return pipeline in the factory area are connected in sections using flanges uniformly. Long distance pipelines are segmented and joined with flanges, which eliminates the need to cut pipes for later pipeline blockage, aging, and replacement, significantly reducing operation and maintenance costs. It is the most commonly used connection method for small and medium-sized water treatment plants.

2. Import and export interfaces for water treatment equipment

Almost all complete sets of water treatment equipment come standard with flange interfaces for inlet and outlet: high-pressure water pump, security filter, quartz sand activated carbon filter tank, softened water resin tank, RO ultrafiltration membrane shell, integrated sewage treatment tank, mixing and dosing tank, sterile pure water tank, etc. The equipment flange is connected to the pipeline and can be disassembled separately without damaging the original pipeline structure.

3. Pipeline valves and instrument connections

The regulating valve, check valve, butterfly valve, electromagnetic flowmeter, pressure gauge, sampling joint, reducing elbow, and tee fittings at both ends of the water treatment system are all equipped with flange connections. Easy to replace faulty valves and calibrate instruments separately, without the need to disassemble the pipeline as a whole, suitable for normal operation and maintenance of water plants.

4. Reserved pipe openings for the tank body of the pool

Biochemical sewage tank, regulating tank, clean water tank, chemical dissolution tank side inlet, bottom discharge, top overflow pipe mouth, external welded flange external pipeline, strong waterproof sealing, long-term immersion in water body is not easy to peel off or leak.

5. High voltage backup partition pipeline

The high-pressure production water and concentrated water pipelines of reverse osmosis, as well as the high-pressure section at the outlet of the booster pump, are reinforced with high-pressure flanges; The spare pipe openings and maintenance partition points of the equipment are sealed with blind flanges to facilitate system expansion and segmented water outage maintenance.

3、 Common flange types and applicable working conditions for water treatment (high-frequency engineering selection)

Based on water treatment pressure, pipe diameter, water quality, and installation conditions, the industry mainstream selects 5 types of flanges, which are specifically adapted to high and low pressure, anti-corrosion, and clean working conditions:

1. Plate type flat welding flange (PL) - water treatment universal version

The most cost-effective, easy to install, and preferred for low-pressure and room temperature working conditions. It is commonly used for municipal ordinary sewage, circulating cooling water, large-diameter pipelines for raw water transportation, interfaces for low-pressure filtration equipment, small-scale water purification equipment for civilian use, and the largest amount of low-pressure water supply and drainage in factory areas. It is easy to weld and suitable for sealing with conventional rubber gaskets.

2. Neck welding flange (SO) - specialized for pump room vibration pipelines

The overall stiffness is better than that of plate welding flanges, with stronger resistance to vibration and deformation. It is suitable for water pump inlet and outlet, medium frequency pressurized sewage pipelines, and branch pressure pipelines, alleviating bolt loosening and gasket leakage problems caused by pump start stop vibration.

3. Neck welding flange (WN) - special for high-pressure water treatment

Good welding sealing and high pressure rating, belonging to high-pressure special flanges. The core is used for high-pressure pipelines of RO reverse osmosis pure water equipment, concentrated water reflux high-pressure pipelines, high-pressure booster pump outlets, and high-pressure units for reclaimed water reuse. It can withstand high-pressure water flow of 1.6-10MPa and prevent interface rupture and leakage.

4. Threaded flange (Th) - specialized for small diameter dosing pipelines

No welding required, direct threaded connection, suitable for DN15-DN50 small-diameter pipelines, mostly used for acid-base dosing small pipes, water quality sampling pipes, and small metering pump interfaces. No need for hot work on construction sites, suitable for use in explosion-proof water treatment workshops.

5. Blind flange (blind plate) - dedicated for partition sealing

The main purpose is to block the spare interfaces of equipment and idle pipeline openings. During system maintenance, flange blind plates are used to isolate water flow in sections, achieving local water cut-off operations without affecting the operation of the entire water treatment unit. It is an essential accessory for water plant operation and maintenance.

Addendum: Flange selection for the three major sealing surfaces in water treatment

-RF protruding flange: universal, suitable for all scenes of clean water and ordinary sewage, matched with PTFE and rubber gaskets;

-MFM concave convex flange: specialized for anti-corrosion agents and corrosive wastewater pipelines to prevent gasket displacement and leakage;

-Mortise and tenon flange: specially designed for food grade pure water and medical grade ultra pure water equipment. The gasket is resistant to water flow erosion, with no residual impurities and a higher level of hygiene.

4、 Classification of flange materials for water treatment, precise selection based on water quality

The corrosiveness and cleanliness of water quality directly determine the material of flanges. Choosing the wrong material can easily lead to rusting, secondary pollution of water bodies, and corrosion and fracture of interfaces. The selection criteria for the three mainstream materials are as follows:

1. Carbon steel flange (Q235)

Low cost, suitable for ordinary municipal sewage, industrial circulating cooling water, and primary water transmission pipelines; Before use, anti-corrosion painting treatment must be carried out to isolate water oxidation. It is strictly prohibited to use it in pure water, acid and alkali agent pipelines to avoid rust pollution of water quality.

2. Stainless steel flange (304/316L)

High end mainstream materials for water treatment. 304 stainless steel flange suitable for pure water, ultrafiltration water, and domestic water purification equipment; 316L stainless steel flange is resistant to acid and alkali, chloride ion corrosion, suitable for chemical wastewater, acid washing wastewater, disinfection and dosing pipelines, seawater desalination water treatment equipment, rust and corrosion resistance, and meets water related hygiene standards.

3. Plastic anti-corrosion flange (UPVC/PP/FRP)

Fully corrosion-resistant and lightweight material, only suitable for low pressure and room temperature working conditions, suitable for small and medium-sized acid-base wastewater, laboratory water purification, and small dosing equipment pipelines; Weak compressive strength, prohibited for use in high-pressure pump outlets and high-pressure reverse osmosis pipelines, prone to cracking and damage under high pressure.

5、 Precautions for Sealing and Installation of Water Treatment Flanges

1. Selection of gasket for working condition matching

-Ordinary clean water and circulating water: natural rubber gasket with good elasticity and low cost;

-Acid and alkali agents, pure water system: PTFE PTFE gasket, corrosion-resistant, no precipitation;

-High pressure and high temperature pipelines: metal wrapped gaskets, high-strength pressure bearing seals.

2. Key points for avoiding pitfalls during on-site use

1. Pump body vibration points: It is prohibited to use ordinary flat welding flanges alone. Priority should be given to using neck flanges and thickened elastic gaskets to reduce bolt loosening and leakage;
2. Ultra pure water purification system: Eliminate carbon steel flanges and use stainless steel flanges throughout the entire area to prevent secondary pollution of water quality by rust impurities;
3. Outdoor outdoor water treatment unit: The flange bolts are made of stainless steel to prevent bolt corrosion and prevent disassembly;
4. Corrosive wastewater system: Prioritize sealing flanges on concave and convex surfaces and mortise and tenon surfaces to enhance anti-seepage capabilities.

6、 Summary of flange application in mainstream complete water treatment equipment

1. Integrated sewage treatment equipment: box inlet and outlet, aeration pipeline, sludge discharge pipeline, mainly made of carbon steel anti-corrosion and 304 stainless steel flat welding flange;

2. RO reverse osmosis pure water equipment: high-pressure pump, membrane housing, security filter, concentrated water pipeline, standard 304/316L neck welded high-pressure flange;

3. Softened water filtration and purification equipment: resin tank, multi way valve interface, often using national standard plate welding stainless steel flanges;

4. Fully automatic dosing system: medication tank, metering pump small tube, using PP anti-corrosion flange and small threaded flange.

Conclusion

Although flanges are small pipeline accessories for water treatment, they directly determine the sealing, maintenance convenience, and service life of the entire water treatment system. Engineering selection should be based on pipeline pressure, water quality corrosiveness, and installation environment, matched with corresponding connection forms, sealing surfaces, and materials of water treatment special flanges. For low-pressure sewage, carbon steel flat welding flanges should be selected, for high-pressure pure water, stainless steel butt welding flanges should be selected, and for acid-base media, plastic or 316L anti-corrosion flanges should be selected. Compliance selection can effectively reduce pipeline leakage, corrosion, and maintenance costs, ensuring long-term stable operation of the water treatment system.

Core keywords: water treatment flange, sewage equipment flange, reverse osmosis high-pressure flange, water treatment pipeline flange, stainless steel water wading flange