Spiral Pipe Installation

 Slip Joints & Flange-to-Flange Joints

 There are two basic methods for connecting Spiral Pipe

The first, and simplest method, is by using Slip Joints. Since all spiral pipe ends are female, and all spiral pipe fittings are male, they can be easily slipped together and fastened. However many installations have additional performance requirements, and to meet these requirements a number of Flange-to-Flange connection methods have been developed. Spiral Manufacturing offers a complete array of both slip joint and flange joint options to meet any system requirements, and we offer technical assistance to help you choose the best option for your application.

Single-Wall Connection Methods

Slip Joints
Flange-to-Flange Joints
Angle Ring Flanges
Vanstone Flange
Spiralmate Flanges

Spiral Pipe Installation

Slip Joints

Fastening and Sealing Slip Joints

Slip joints can be fastened with Tek-Screws or Pop-Rivets. The standard recommendation is for screws or rivets to be used at maximum of 15″ intervals with no fewer than three screws or rivets per joint. Spiral Manufacturing recommends a maximum of 6″. When additional air tightness is required, duct sealant or sealant tape can be used. The screws or rivets hold the duct in place as the sealant cures.

Fitting-to-Fitting Slip Joint

Coupling: Fitting-To-Fitting (male-to-male) slip joints require a separate coupling (C-1-F, see below). When a coupling is not available, a short length of spiral pipe can be used for a quick, in the- field connection.

C-1-F Coupling

Spiral Pipe Installation

Pipe-to-Pipe Slip Joint

Coupling: Pipe-To-Pipe (female-to-female) slip joints require a standard C-1 coupling, which is male. C-1 couplings are also used with flexhose.

C-1 Coupling


Pipe-To-Fitting Slip Joint

No coupling required: Since pipe sections are female and fittings male, they just slip together.

No Coupling Required


Flange-to-Flange Joints

flange-to-flangeFlange-to-flange joints are widely used to connect pipes in dust and fume control applications, in outdoor applications, and for additional strength in high positive or high negative pressure applications.

The basic flange-to-flange joints consist of two facing flanges which are fastened to the ends of the the spiral pipe with screws, pop-rivets, or sometimes by tack welding-except in the case of Vanstone flanges, which do not require fastening to the duct under standard loading conditions. The two flanged ends are then fastened together with bolts, screws, or flange clamps.

Bolts are used for permanent installations and when the pipe must mate with fans or other air moving equipment. In installations where there is a need for frequent maintenance or cleaning, flange clamps are used.

Spiral Manufacturing offers three configurations of flange-to-flange joints: (1) Angle Ring flanges, (2) the most-widely-used Vanstone flanges, and (3) Engineered flange systems, such as Accuflange, Spiralmate, and Wonderflange.

Spiral Manufacturing offers precision-made, labor-saving, and installation-ready Vanstone flanges direct from our factory.

Flange-to-flange joints are available for both single and double wall spiral pipe.

Types of Flange-to-Flange Joints

Basic Angle Ring Flanges

Pressed and rolled steel angle rings are used widely in joining ductwork in dust and fume control work. Available in 3″ to 96″ diameters, standard rings are unpainted, mild steel. (Galvanized and Stainless Steel available). They are available with or without holes. Nearly any bolt circle spacing or hole size is available.

View Angle Ring Sizes and Dimensions

Vanstone Flanges

Vanstone Flanges are a very practical and labor saving method for connecting Spiral duct and fittings. Vanstone connections consist of a “face flange” and a separate “backing flange or angle ring” that is slip fit over the Spiral duct. (See illustration below.)

The face flange is mechanically formed on the end of the duct section by turning the end of the duct to form a “‘lip” or “face flange” with an outside diameter just small enough to clear the necessary connecting hardware.

Spiral Manufacturing has developed a specially designed machine which automatically turns the “face flange”. It has the capability to provide precision aligned, secure, and consistent Vanstone flange assemblies at our factory, thus, eliminating hours of field labor.


The complete joint consists of a matching set of “face flanges” (already Factory formed from the duct wall), and “the backing flange of the angle ring”, which is slip-fit over the end of the pipe OD prior to forming the face flange.

If the duct selection for an industrial duct application does not require a “stiffened” result from the flange connector, the backing flange of the angle ring remains as an unattached slip fit around the duct wall. If the design does require a “stiffening” capability, the angle ring must be stitch-welded (per your specifications) to the duct wall to ensure a dependable load-sharing contribution from the Vanstone joint.

View Vanstone Field-Mounting Instructions

Sheet Metal Accuflange Joint

AccuFlange is a patented connecting system, which, when installed and sealed per recommendations, is suitable for use on all systems across a range of internal duct pressures from -10″W.G. to +10″W.G. It is available for both single and double wall pipe, and in a variety of materials.

AccuFlange is easy and efficient to install, and reduces field labor. It is fastened internally to pipe and fittings with tack welds or Tek-screws and sealed with mastic, and it is joined to its mating flange with gasket and Tek-screws or Quick Draw clamp, thus eliminating concerns about aligning bolt holes.


6″ – 28″ (Even & Odd Sizes)’ 18 Gauge ( 6″- 8″ have 1″ small face)
30″ – 58″ (Even Sizes) 18 Gauge
60″ – 96″ (Even Sizes) 14 Gauge
Double wall pipe and fittings are available in 1″, 2″ and 3″ thicknesses.

Spiralmate Flanges

Spiralmate® flanges are easy to install, and they are airtight without the need for additional sealants. The joint allows perfect alignment, and is attractive when exposed.

The Spiralmate system is comprised of four components: two flanges with an integral mastic injected into the duct receiving pocket, a neoprene gasket to seal the mating surface of the flanges, and a one bolt closure ring. Installed properly, there is virtually no leakage up to 18″ WG positive pressure, or down to 10″ negative pressure.

Spiralmate is available for spiral duct from 8″ to 72″. Galvanized material is standard, but Gavannealed, Stainless, and PVS Coated are available.