Double pipe heat exchangers are simple, versatile units consisting of one tube inside another. Their modular construction means individual sections can be replaced without affecting the rest of the assembly. AQ Process Systems sources and exports all components needed for double pipe and hairpin exchanger maintenance.
We source inner tubes and outer pipes in carbon steel, stainless steel, and alloy grades. Return bends (U-bends), closure fittings, gland packing, and gaskets are available for all standard double pipe and multi-tube hairpin designs from Brown Fintube, Koch, and other manufacturers.
For finned double pipe exchangers, we also supply longitudinally finned inner tubes, welded or extruded fin types, to enhance heat transfer in gas-to-liquid or viscous fluid applications.
| Component | Specification | Description |
|---|---|---|
| Tubes & Pipes | ||
| Inner Tubes | CS, SS, alloy | Plain or longitudinally finned | Inner (tube-side) pipes, plain for liquid/liquid service or longitudinally finned for enhanced heat transfer. |
| Outer Pipes (Shell) | CS or SS | Standard pipe sizes | Outer (annulus-side) pipes, typically standard NPS sizes cut to length. |
| Longitudinal Finned Tubes | Welded or extruded fins | CS/SS/alloy base | Inner tubes with longitudinal fins for increased surface area in gas cooling or viscous fluid applications. |
| Returns & Closures | ||
| Return Bends (U-bends) | Forged or fabricated | CS or SS | Hairpin return bends connecting the inner tubes at the far end of each section. |
| Return Headers (Multi-tube) | Fabricated header boxes | CS or SS | Multi-tube return headers for hairpin exchangers with multiple inner tubes per shell. |
| Closure Fittings | Threaded or flanged | CS or SS | End closures (bonnets, plugs, or caps) providing access to tube ends for inspection and cleaning. |
| Sealing & Support | ||
| Gland Packing | Graphite, PTFE, or combination | Various sizes | Packing sets for the gland where the inner tube passes through the outer pipe end fitting, prevents annulus leakage. |
| Gaskets | Spiral wound, compressed fibre, or PTFE | Closure and flange gaskets, replaced during every maintenance opening. |
| Support Saddles & Clamps | CS | Pipe support hardware | Pipe support saddles and U-bolt clamps for mounting double pipe sections on pipe racks or structures. |
| Spacer Bands | SS or CS | Centering inner tube in outer | Spacer rings or bands maintaining concentricity of the inner tube within the outer pipe. |
Parts are matched to OEM material specifications and dimensional tolerances. Please provide the equipment manufacturer, model number, and serial number (if available) for precise part identification. Mill Test Certificates (MTC) supplied with all tube materials per EN 10204 3.1.
The most common replacement parts are inner tubes (corrosion or fouling), gland packing (the primary wear/seal item), gaskets (replaced every opening), return bends (erosion in high-velocity service), and spacer bands (wear from thermal movement). The outer pipe rarely needs replacement unless it corrodes externally.
Yes, this is one of the main advantages of double pipe design. Individual hairpin sections can be isolated and replaced without affecting the remaining sections. AQ Process Systems can supply replacement sections matched to the existing pipe sizes and configuration.
Yes. We supply inner tubes with longitudinal fins, welded, extruded, or mechanically bonded types, for enhanced heat transfer in gas cooling and viscous fluid heating applications. Fin height, count, and material are matched to the original equipment specification.
Gland packing lifespan depends on thermal cycling frequency and process pressure. In stable operation, packing may last 2-5 years. With frequent thermal cycling or high pressure, replacement may be needed annually. We recommend inspecting packing during every shutdown and tightening or replacing as needed.
A multi-tube hairpin exchanger has multiple inner tubes inside a single outer shell pipe, typically 2-9 tubes, with a return header at one end. This provides more surface area than a single-tube double pipe while maintaining the simplicity and modularity of the double pipe concept. We supply all spares including return headers and individual inner tubes.
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