The ABYC Standards & Compliance department frequently receives questions regarding hose clamp requirements and installation, which is addressed in several of our standards. In a previous article, we discussed common questions and requirements. This second article will address applications where two hose clamps are required and installation tips.
Two Clamps or One?
Ever wonder when ABYC standards call for two hose clamps instead of one? Here’s what the materials say:
- H-24 and H-33 – Fuel Tank Fill System
- Hose used in the fuel tank fill system shall be secured to pipes (smooth pipes are acceptable), spuds, or other fittings at each connection, by at least two corrosion resistant metallic clamps with nominal band widths of at least 0.5 in (12.7 mm).
- P-1 Flexible Exhaust Hose Connections
- Every exhaust hose connection shall be secured with at least two non-overlapping clamps at each end to produce a secure, liquid- and gas-tight joint.
Tech Tip: Adding an extra clamp on a barb designed for a single clamp can actually damage the hose and weaken the connection.
Hose Clamp Installation
A secure connection starts with a correct installation.
- Be sure the hose is designed to be clamped. Some Type A fuel hose, and certain wire or mesh reinforced hoses are not designed to be clamped.
- Match the hose inside diameter to the outside diameter of the connecting spud, pipe, or fitting. Fuel hose has actual tolerances on the hose to spud connection. Check H-24 Table 2 to be sure.
- Clamps shall be beyond the bead or flare – or over the serrations on the connecting fitting.
- Use the proper size clamp for the installation. Clamps oversized for the hose do not seal properly.
- Do not overtighten hose clamps. Follow manufacturer recommend torque specifications.
- If using double clamps on connections where it is not designed or required, avoid the clamp being placed on the bead or beyond the barb as it can deform or cut the hose and weaken the connection.
For more information on hose clamps, read last week’s article on common questions and requirements: abycinc.org/hose-clamps-questions-and-requirements.
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