Flat welding flanges are divided into two structures: plate-type flat welding (PL) and neck-type flat welding (SO). After the pipe is inserted into the inner ring of the flange, it is fixed by double-sided fillet welding, achieving a detachable sealed connection between pipe and pipe, valves, pump bodies, and equipment ports. Compared with butt welding flanges, flat welding flanges are easier to align, require lower welding construction difficulty, and save material, making them suitable for low-pressure and medium-pressure ambient-temperature pipeline networks with small pressure fluctuations and no severe impact or vibration. The flat welding flanges we produce comply with mainstream standards such as GB/T9113, HG/T20592, ASME B16.5, DIN, JIS, etc., with flat sealing surfaces, symmetrical bolt hole positions, and qualified end face perpendicularity. Materials cover carbon steel (Q235B, 20#, 16Mn, etc.), stainless steel, and alloy steel, with pressure ratings adapted to PN6, PN10, PN16, PN25, Class150, and Class300. Conventional small and medium diameters DN15–DN200 are sufficiently stocked, and custom non-standard sizes, special sealing surfaces, and surface treatments are supported according to project requirements. If you need selection assistance or batch quotations, please contact us and provide information on the medium, pressure, temperature, and quantity.
Overview
Slip-on flanges are standardized connecting components widely used in low-pressure systems of industrial pipelines, and are divided into two common structures: plate-type slip-on (PL) and slip-on with neck (SO). During installation, the pipe is inserted into the inner ring of the flange and fixed by double-sided fillet welding, used for detachable sealed connections between pipes and pipes, valves, pump bodies, heat exchangers, and equipment ports. It is suitable for normal-temperature pipe networks with small pressure fluctuations, no severe impact or vibration, and no extreme high temperature or high pressure, and is a basic accessory in projects such as municipal water supply and drainage, thermal heating, sewage treatment, general chemical engineering, and mechanical and electrical supporting facilities. The slip-on flanges we produce comply with standards such as GB/T9113, HG/T20592, ASME B16.5, DIN, and JIS, with nominal diameters covering DN15–DN2000, pressure ratings adapted to PN6 to PN25 and Class150 and Class300, and materials available in carbon steel, stainless steel, and alloy steel.
Key Features
The procurement value of slip-on flanges is mainly reflected in several aspects. First, the standard systems are complete, and national standards, American standards, German standards, and Japanese standards can all be supplied, with nominal diameters and pressure ratings covering conventional medium- and low-pressure pipeline needs, and good interchangeability with commonly used pipe fittings, valves, and equipment ports on the market. Second, the installation threshold is low, the pipe is inserted and formed by fillet welding, alignment is convenient, welding speed is fast, and it is suitable for large-scale conventional pipe network laying and on-site construction. Third, material selection is flexible, and carbon steel, stainless steel, and alloy steel can be matched according to medium corrosiveness and operating temperature; carbon steel is commonly used in conventional scenarios such as water heating, sewage, and circulating water, while stainless steel can be selected for weakly corrosive media. Fourth, conventional small and medium diameters from DN15–DN200 are sufficiently stocked, and after order confirmation, re-inspection, packing, and dispatch can be completed within 24 hours, making it suitable for project replenishment and bulk centralized procurement. Fifth, non-standard customization is supported, including special hole diameters, special bolt hole spacing, non-conventional sealing surfaces, surface treatment, and customized packaging, and production can be carried out according to project drawings or technical agreements.
Applications
Slip-on flanges are mainly used in medium- and low-pressure normal-temperature pipeline systems with stable operating conditions. In the municipal field, they are commonly found in urban water supply and drainage, rainwater and sewage diversion, tap water conveyance, and old pipe network renovation, and can be used in both open-air and buried environments. In thermal heating, they are used for valve and equipment port connections in central heating networks, factory circulating thermal pipelines, and low-temperature steam auxiliary pipe networks. In environmental water treatment, they are used for equipment connection and sectional maintenance in sewage conveyance, exhaust gas ventilation, and water treatment process pipelines. In general chemical and light industry fields, they are used in scenarios such as weakly acidic and weakly alkaline media, atmospheric-pressure process pipelines, and auxiliary tank connections, but are not recommended for high-temperature and high-pressure, flammable and explosive, or severely vibrating operating conditions. In mechanical and electrical equipment supporting facilities, they are used for port connections of water pumps, valves, heat exchangers, HVAC units, fire protection pipelines, and ventilation and oil supply systems, facilitating later maintenance and equipment replacement.
Specifications
Slip-on flanges cover nominal diameters from DN15–DN2000, and pressure ratings are adapted to PN6, PN10, PN16, PN25, Class150, and Class300. Sealing surface forms include RF raised face, FF full face, MFM male and female face, and TG tongue and groove face, which can be confirmed according to project requirements. Materials cover carbon steel (Q235B, 20#, 16Mn, S235JR, SS400, etc.), stainless steel, and alloy steel; please contact us to confirm the specific material selection. Surface treatment supports fine turning, galvanizing, anti-corrosion painting, sandblasting, polishing, etc. For conventional small and medium diameters from DN15–DN200 in national standard and American standard in-stock styles, the MOQ is as low as 10 pieces; please contact us to confirm other specifications and customization needs. Packaging adopts foreign-trade-grade solutions for scratch resistance, impact resistance, rust resistance, and moisture resistance; sealing surfaces are covered with protective film, bolt holes are fitted with protective plugs, small and medium diameters are wrapped in pearl cotton and then packed in hard cartons, large diameters are wrapped with film for reinforcement, and bulk shipments are secured on fumigation-free solid wood pallets.
Procurement & Delivery
We supply slip-on flanges to customers such as general engineering contractors, thermal supporting facilities, sewage treatment, chemical construction, mechanical and electrical installation, equipment and valve supporting facilities, and foreign trade wholesalers. For conventional DN15–DN200 carbon steel and stainless steel in-stock styles, re-inspection, packing, and dispatch are completed within 24 hours after order confirmation. Customized specifications need to be arranged for production after confirmation according to drawings, technical agreements, or samples; please contact us to confirm the delivery time. Regarding minimum order quantity, the MOQ for conventional small and medium diameter in-stock styles is as low as 10 pieces, suitable for sporadic project replenishment, small trial orders, and foreign trade sample orders; bulk centralized procurement and full-container distribution can be discussed separately. Packaging can be customized as needed with English shipping marks, specifications and models, batch numbers, customer LOGO, and packing lists. If you need a quotation, please provide the nominal diameter, pressure rating, material, sealing surface form, quantity, and destination, and we will assist in confirming the configuration and delivery plan.
Service & Support
We provide selection assistance and after-sales support for slip-on flange procurement customers. Before sale, we can assist in matching materials, pressure ratings, and sealing surface models according to the medium, pressure, temperature, and operating environment, reducing rework caused by improper selection. Before leaving the factory, products undergo dimensional calibration, end face inspection, material sampling inspection, and other processes. For quality issues such as our manufacturing process, machining accuracy, material ratio, or specification mismatch, we support free returns and exchanges and free replacement, and bear the round-trip logistics costs. After sale, we provide guidance on pipeline slip-on welding construction processes, flange installation alignment, bolt tightening specifications, and daily operation and maintenance Q&A, with full-process logistics tracking and assistance for overseas customers with customs clearance. The product warranty is 18 months, with 7×24-hour response. If you have technical or order questions, please contact us.
FAQ
What is the difference between slip-on flanges and butt-welding flanges?
Slip-on flanges adopt a structure in which the pipe is inserted into the inner ring of the flange and then double-sided fillet welded, with no high-neck transition, and are suitable for medium- and low-pressure normal-temperature pipeline systems with stable operating conditions, with convenient installation alignment, low construction difficulty, and relatively economical cost. Butt-welding flanges have a high-neck tapered neck structure and adopt butt welding, and are suitable for harsher operating conditions such as high temperature and high pressure, vibration, and impact, with higher cost. When selecting, please confirm according to medium pressure, temperature, and operating conditions, and if you have any questions, please contact us for assistance in judgment.
How to select common pressure ratings?
For conventional plumbing, sewage, municipal water supply and drainage, and similar scenarios, PN10, PN16, or Class150 are usually selected; for medium-pressure pipelines in circulating processes, PN25 or Class300 may be selected. The specific selection needs to be confirmed in combination with the medium, temperature, pipe diameter, and engineering specifications. You are welcome to contact us to provide operating condition information, and we will assist in matching the pressure rating and sealing face form.
What materials are available for slip-on flanges?
We provide three major categories of materials: carbon steel, stainless steel, and alloy steel. Common carbon steels include Q235B, 20#, 16Mn, S235JR, SS400, etc., suitable for conventional water, sewage, circulating water, and ordinary oil and gas media; stainless steel is suitable for mildly corrosive media such as weak acids and weak bases; alloy steel can be confirmed according to project requirements. For specific material selection, please contact us and provide the medium type and operating temperature.
What are the delivery time and minimum order quantity for conventional specifications?
For conventional DN15–DN200 small and medium diameter national standard and American standard in-stock styles, the MOQ is as low as 10 pieces, and re-inspection, packing, and outbound shipment are completed within 24 hours after order confirmation. For the delivery time and minimum order quantity of other diameters, pressure ratings, or customized specifications, please contact us for confirmation. For bulk centralized procurement and full-container shipments, packaging and logistics solutions can be discussed separately.
Do you support non-standard customization and custom packaging?
Yes. We can customize non-standard dimensions, special hole diameters, special bolt hole spacing, non-conventional sealing faces, surface treatment, and packaging markings according to customer drawings, technical agreements, or samples. In terms of packaging, English shipping marks, specifications and models, batch numbers, customer LOGO, and packing lists can be customized. Please provide specific customization requirements and quantities, and we will assist in confirming the production plan and delivery time.
