PP plastic ring

Product Model	Injection Molded Spigot Ring Series
Category	PP Molded Products
Reference Price	Price on request

Hot Customizable for Working Conditions 11 Technical Parameters

Product Overview

PP sleeve rings, also known as direct or sleeve joints, are tubular connecting components with承口 at both ends, specifically designed for axial splicing of two sections of PP air ducts with the same diameter. During installation, each section of the air duct is inserted into one end of the sleeve ring, aligned, and then sealed with PP welding rods at the承口. This achieves pipe extension. The sleeve ring features a simple structure and low cost, making it a widely used standard component in straight splicing of corrosion-resistant ventilation pipes.

The sleeve ring is molded in one piece using injection molding technology, resulting in a seamless, uniformly thick wall. The inner surface aligns smoothly with the inner wall of the air duct, eliminating pronounced steps or ledges at the connection point, thereby minimizing airflow resistance and reducing dust accumulation. Compared to flange connections, sleeve ring connections offer a cleaner appearance and lower cost, making them suitable for fixed pipe sections that do not require disassembly. Compared to direct welding, sleeve ring承插定位 is easier and provides more stable alignment quality.

The PP sleeve rings supplied by Xicheng Environmental Protection are matched with the diameter series of formed air ducts and are available in both standard PP and flame-retardant PP materials. Flame-retardant sleeve rings, when used with PP air ducts, also exhibit self-extinguishing properties at the joint, ensuring fire consistency throughout the entire pipeline. Sleeve rings can also be used to connect air ducts to equipment interfaces with 承口.

Working Principle

Sleeve ring connections achieve sealing and fixation through 承插 plus welding. The inner diameter of the sleeve ring is slightly larger than the outer diameter of the air duct, forming a 承插配合. After insertion, the ends of the two air duct sections align at the center of the sleeve ring. The 承口 restricts radial misalignment of the air ducts, keeping the pipeline straight. The gap at the 承口 is sealed using a hot air welding gun and PP welding rods. The weld closes along the circular periphery of the sleeve ring's end, melting three plastic sections into one, preventing gas from escaping at the joint.

The 承插 structure enhances the load-bearing capacity of the joint. When the air ducts are subjected to wind pressure or slight vibration, the sleeve ring encases the pipe ends, with the weld primarily responsible for sealing, while axial and radial loads are distributed by the 承插配合 surface. This provides stronger anti-deformation capabilities compared to simple direct welding. The thermal expansion coefficients of PP sleeve rings and air ducts are identical, allowing them to expand and contract synchronously with temperature changes, preventing cracks at the joint due to uneven expansion or contraction.

Structural Composition

The PP sleeve ring consists of a short tube with a thickened 承口 at both ends. The inner diameter of the 承口 matches the outer diameter of the air duct, and a positioning step or equal-diameter straight cavity is provided at the center. The outer wall of the 承口 may feature a circumferential reinforcement ring to enhance rigidity, and the ends are chamfered for easier air duct insertion. The sleeve ring is molded in one piece, resulting in smooth inner and outer walls. Its length increases with the diameter to ensure sufficient 承插 depth and weld positioning.

Flame-retardant sleeve rings incorporate flame-retardant additives into the raw material, resembling standard sleeve rings in appearance but with self-extinguishing properties. The sleeve ring itself does not include components such as bolts or gaskets; only PP welding rods and a hot air welding gun are required for connection. For sections requiring inspection or disassembly, sleeve rings are not suitable, and flange connections should be used instead.

Specification Model Table

The table below shows the connection type and applicable locations of the sleeve rings, with diameters corresponding to formed air duct series.

Type	Connection Method	Applicable Location
Standard PP Sleeve Ring	承插 Welding	General Acid-Alkali Exhaust
Flame-Retardant PP Sleeve Ring	承插 Welding	Indoor Fire-Resistant Air Ducts
Thickened Sleeve Ring	承插 Welding	Large-Diameter Main Pipes

Product Features

PP sleeve ring connections are straight and fast to install, making them an economical solution for fixed straight sections of air ducts. Key features include:

Injection-molded in one piece, seamless, and fully corrosion-resistant
Two-end 承插 positioning ensures straight pipe alignment and quick installation
Smooth inner surface reduces airflow resistance and prevents dust accumulation or contamination
Combination of 承插 and welding provides dual protection for excellent sealing and crack resistance
Simple structure, lightweight, and lower cost than flange connections
Specifications match formed air ducts, with flame-retardant material options available
Expands and contracts synchronously with air ducts, excellent temperature adaptability

Material	PP / PPs Polypropylene
Molding Process	Integral injection molding
Connection Method	Two-end socket welding
Applicable Pipes	PP Duct with Same Flange
Corrosion resistance performance	Acid-alkali-resistant salt
Flame Retardant Options	PPs self-extinguishing
Inner wall features	Seamless connection with ductwork
Removability	Fixed connection, non-detachable
Function	Tube splicing reinforcement
Matching Port	Multiple size options available
Sealing Features	Welded Seam Connection Sealing

Application Industries

Linear extension and splicing of straight ducts in acid-alkali exhaust systems of electroplating workshops
Fixed pipe section connections of exhaust air ducts in chemical enterprises
Direct pipe connections in acid-alkali exhaust systems of semiconductor factories
Segment connections between laboratory exhaust shafts and horizontal main ducts
On-site splicing of corrosion-resistant exhaust ducts in metallurgical pickling lines
Extended connections of odor collection pipelines in wastewater treatment plants
Fixed section connections of tail gas emission ducts in pharmaceutical factories

Typical Process Locations

Collars are used for straight duct sections in ventilation systems that do not require disassembly, commonly found in horizontal main ducts along supports and vertical shafts. Due to the limited single length of standard formed ducts, collars are used for point-to-point connections over long distances. The collar is positioned between two hangers or near the support, forming a continuous and integrated pipeline after connection. Collars are not used for equipment inlets/outlets or areas requiring frequent maintenance.

In exhaust collection systems, the collared pipe sections are located in the transport paths between hood branch ducts and main ducts, as well as between main ducts and purification equipment. During installation, one end of the duct is fixed, the collar is inserted, and the other end is connected after alignment and leveling, followed by sealing along the flange circumference. Removable sections near fans and equipment are connected with flanges, while fixed transport sections primarily use collars to balance sealing performance and cost-effectiveness. Before collaring, verify that the outer diameters of both duct ends match the collar inner diameter, ensure uniform insertion depth and consistent annular gaps, and clean/dry the flanges before symmetrical welding around the circumference to avoid offset caused by unilateral buildup. Collared sections are positioned between two hangers and temporarily fixed, with sealing integrity checked after welding. Areas near fan vibration zones and those requiring disassembly are not connected with collars but instead use flanges or flexible connections.

The sleeve connection has low cost, a simple design, and excellent weld seam sealing, but it is non-detachable after welding, making it suitable for fixed, non-maintenance required straight pipe sections and long-distance dry pipe transportation. The flange connection has a slightly higher cost and larger dimensions, but it can be disassembled at any time, making it suitable for equipment inlets/outlets, valve and muffler ends, and areas requiring regular cleaning and maintenance. In engineering, sleeve connections are typically used for fixed transportation sections to control costs, while flanges are used for equipment and valve connections for maintenance. The two methods are used in combination based on the location. Detachable sections near vibrating equipment such as fans should be equipped with flexible connections and should not be welded shut with sleeves. When selecting, the connection type is determined based on whether the section requires disassembly, whether it is near equipment, while considering sealing performance, cost-effectiveness, and future maintenance.

Properly installed ring flanges with spigot welding will not leak air. The key lies in ensuring the two ends of the ducts are inserted correctly and the axes are aligned. The annular gap of the socket should be continuously welded around using a weld wire of the same material, without any breaks, pores, or incomplete welds. Before welding, clean the oil and oxide layers from the socket. During welding, ensure the weld wire fully fuses with the base material, and no stress should be applied to the weld before it cools. For systems with high sealing requirements, air leakage tests or segmented pressure checks can be conducted after welding. Air leakage typically occurs when the weld is not closed, the weld wire does not fully fuse with the base material, or the socket is not inserted properly. These are all construction quality issues. As long as the connection is properly inserted according to the process, fully welded around the circumference, and post-weld checks are performed, the sealing performance of the ring flange joint can meet the requirements of corrosion-resistant ventilation systems.

The inner diameter of the sleeve socket is designed according to the standard outer diameter of the ductwork. As long as the outer diameters of the two connected sections of ductwork are consistent, even with slight variations in wall thickness, they can generally be spliced together. However, significant differences in wall thickness can result in one end being too loose and the other too tight, affecting alignment and weld quality. Excessive looseness can also increase the amount of welding filler required. The outer diameter tolerances of ductwork from different series or manufacturers may vary. Purchasing matching ductwork and sleeve sockets from the same manufacturer ensures better dimensional fit. When the outer diameters are inconsistent, do not force the connection, as misalignment and stress can cause air leakage. Instead, replace with a matching sleeve socket or use machined parts or flanges for transition. Standardizing the outer diameter standards and tolerances of ductwork during ordering can prevent mismatched connections on-site.

The ring itself is merely a connecting piece and does not bear the weight of the pipeline. Support brackets should be independently installed based on pipeline weight, diameter, and span requirements, ensuring welds are not subjected to long-term load. The location of the ring joint should be near the support bracket arrangement to avoid placing the joint exactly at the position of maximum deflection between two brackets, preventing long-term bending stress on the joint. For vertical pipelines, fixed brackets should be installed below the ring joint to support the weight of the upper pipeline section. The spacing of horizontal pipeline brackets is determined based on pipe diameter and wall thickness, with appropriate densification for larger diameters. Proper bracket arrangement can reduce bending moments and vibrations at the joint, extending the service life of welds. During installation, brackets should be fixed first, followed by welding the joint, to prevent misalignment and additional stress caused by welding under suspended pipeline conditions.

The sleeve is a fixed joint for spigot welding, non-removable after welding, with a simple structure and low cost, used for extending and splicing large-diameter ventilation straight pipes. The slip joint consists of a nut and a seal ring, forming a detachable joint that can be sealed by hand or tool tightening without welding, suitable for small-diameter piping requiring frequent disassembly. Ventilation and exhaust pipes generally have large diameters, with welding being the primary method on-site, predominantly using sleeves and flanges; small-diameter water supply, drainage, chemical dosing, and instrumentation piping typically use slip joints. The sleeve excels in reliable sealing and low cost, while the slip joint excels in ease of disassembly. They differ in diameter range and application scenarios. Selection should be based on pipe diameter, the need for frequent disassembly, and connection method, with slip joints generally not used for large-diameter corrosion-resistant exhaust pipes.

The concentric sleeve has symmetrical structures at both ends and no installation direction requirement. However, it must ensure that both sections of the ducts are inserted to the same depth and aligned centrally in the sleeve. Avoid inserting one end fully while leaving the other end hanging, as this will cause uneven weld stress and potential air leakage. Before splicing, clean the pipe ends of burrs, debris, and oxidation layers. Align the duct axis and level it before welding circumferentially. For special sleeves with flow direction requirements or joints with internal flow guides, install them according to the shell's marked airflow direction and never in reverse, as this will increase resistance and affect flow guidance. When adjacent to eccentric components or flow guide fittings, verify the overall direction as well. Before installation, confirm the fitting type and flow direction against the drawings. After welding, recheck the alignment gap and centering.

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