PVC Flange Fittings and considerations for Torque Settings
Please read all instructions before attempting to install flanges.
Materials – Vinyl Flanges PVC
Visually inspect flanges for cracks, deformities, and solvent cement or other obstructions on the sealing surfaces.
A gasket must be used between the flange faces in order to ensure a good seal. For Schedule 80 flanges, GF recommends a 0.125 – ½ thick, full-face gasket with a ‘Shore A scale hardness’ of 70±5, and the bolt torque values published below are based on this specification.
For other hardness requirements, contact GF Technical Services.
Select the gasket material based on the chemical resistance requirements of your system.
A full-face gasket should cover the entire flange-to-flange interface without extending into the flow path.
It is critical to avoid excessive compression stress on a vinyl flange. Therefore, only low-friction fastener materials should be used. Low-friction materials allow torque to be applied easily and gradually, ensuring that the flange is not subjected to sudden, uneven stress during installation, which can lead to cracking.
Either the bolt or the nut, and preferably both, should be zinc-plated to ensure minimal friction. If using stainless steel bolt and nut, lubricant must be used to prevent high friction and seizing. In summary, the following fastener combinations are acceptable:
Cadmium-plated fasteners, while becoming more difficult to obtain due to environmental concerns, are also acceptable with or without lubrication. Galvanized and carbon-steel fasteners are not recommended. Use a copper-graphite anti-seize lubricant to ensure smooth engagement and the ability to disassemble and reassemble the system easily.
Bolts must be long enough that two complete threads are exposed when the nut is tightened by hand. Using a longer bolt does not compromise the integrity of the flange connection, although it wastes material and may make tightening more difficult due to interference with nearby system components.
* Assumes the use of SS, zinc- or cadmium-plated bolt and/or nut along with copper-graphite antiseize lubricant brushed directly onto the bolt threads.
** Assumes the use of zinc- or cadmium-plated bolt, nut, or both. Never use unlubricated, uncoated bolts and nuts with vinyl flanges, as high friction and seizing lead to unpredictable torque and a high incidence of cracking and poor sealing.
Note that the torques listed in Table 3 are for flange-to flange connections in which the full faces of the flanges are in contact. For other types of connections, such as between a flange and a butterfly valve, where the full face of the flange is not in contact with the mating component, less torque will be required. Do not apply the maximumlisted torque to the bolts in such connections, which may cause deformation or cracking, since the flange is not fully supported by the mating component. Instead, start with approximately two-thirds of the listed maximum torque and increase as necessary to make the system leak-free after pressure testing.
Keep Instructions Available
Provide a copy of these instructions to every installer on the job site prior to beginning installation. Installers who have worked primarily with metal flanges often make critical mistakes when installing vinyl flanges. Even experienced vinyl installers will benefit from a quick review of good installation practices before starting a new job.
Best practices include tagging each flange with
This information can be recorded on pre-printed stickers, as shown below, and placed on each flange immediately after installation.
Experience has shown that installation tags speed up the process of resolving system leaks and product failures, improve communication between the contractor and distributor or manufacturer, highlight training opportunities, and promote worker diligence.
© Georg Fischer LLC 2009 Link to original data
Consider Installing an ” Expansion Joint” allowing for lateral, vertical, compression, torsional and tangential movement of your process connections.
Why Choose a PVC – CPVC Flange?
Like all vinyl pipe and fittings, vinyl flanges are lightweight, inexpensive, and easy to install. However, PVC and CPVC have different physical properties than metals, and therefore special care is required to ensure that your vinyl flanges have a long, reliable service life. Installers should study these instructions and follow them carefully in every installation in order to ensure satisfactory performance and enjoy the full benefits of the GF warranty.
When using a vinyl flange, ensure that the entire system is well-supported and that the flange does not bear the weight of a massive, unsupported system component such as a cast iron valve.
See support instructions in the GF Technical Manual online: