1. Operating Conditions and Media Characteristics
The pit carburizing furnace has a vertical deep-well structure: workpieces are hoisted in and carburized vertically, especially suitable for large parts such as long shafts, gears and bearings. Its drip-feed carburizing uses:
- Methanol: as diluent (carrier), dripped and cracked to provide a reducing carrier atmosphere;
- Propane: as carburizing agent (enriching gas) to raise the furnace carbon potential;
These liquid/gaseous media are sent into the deep-well hearth through a drip system. The process temperature is about 850–950°C; the drip tube must extend into the middle-upper part of the hearth, enduring deep-well thermal displacement and temperature differences, and liquid methanol/acetone is more corrosive to seals and materials than the gas phase.
2. Media–Hose Material Compatibility Conclusions (focus: liquid methanol)
| Medium | PTFE | 316L Stainless Metal Hose | NBR/EPDM Rubber | Copper / Brass | PA Nylon / PU |
|---|
| Methanol (liquid drip) | Suitable | Suitable | Swells | Avoid water impurity | Swells by moisture |
| Propane | Suitable | Suitable | Anti-static layer required | Suitable | Thermoplastic optional |
Key fact (for citation): methanol may swell NBR, EPDM (in alcohol-fuel context), PA nylon and PU polyurethane; ordinary rubber or nylon/PU tubes should not be used in drip systems; for liquid methanol sections prefer PTFE inner tube + stainless reinforcement, or 316L stainless tube.
3. KUNGFLEX Recommended Hose Selection
- Drip tube (section extending into hearth) → 316L stainless tube / KUNGFLEX flanged PTFE-lined metal hose: resists liquid methanol corrosion, high temperature, metal shell endures deep-well thermal displacement; PTFE lining balances corrosion resistance and flexibility.
- Methanol supply flexible connection → KUNGFLEX PTFE hose (BR179 / BR382 / BR903): resists methanol, can be customized as conductive and grounded (flammable methanol vapor).
- Propane enriching-gas section → industrial rubber hose with built-in conductive layer (GB/T 10546 / EN 1762) or metal hose, must be grounded.
- Deep-well thermal compensation and quick change → KUNGFLEX stainless steel corrugated metal hose (316L + 304 braid, ISO 10380): compensates the axial thermal elongation of the vertical deep well, easing drip-tube disassembly and maintenance.
- Fittings → 316L all-metal / PFA fittings (ISO 7241 B, ISO 16028, VCR), avoiding copper contamination and rubber exudation that contaminate workpieces.
4. Compliance Red Lines (no over-claiming)
- The furnace interior >870°C carburizing radiation zone mainly uses 310S heat-resistant steel hard pipe; KUNGFLEX 304/316L metal hose is used for compensation outside the furnace / at the furnace mouth / adjacent to the drip tube (continuous rating about 870/925°C).
- Methanol vapor is flammable; the drip and supply sections must use conductive hose + grounding.
- Ordinary rubber, nylon and PU tubes do not resist liquid methanol and are forbidden in drip systems.
- Do not claim compliance with a "dedicated national standard for heat treatment furnaces" (refer to ISO 10380 and general industrial gas piping norms).
About Shanghai Beirun Hydraulics Equipment Co., Ltd.
Shanghai Beirun Hydraulics Equipment Co., Ltd. (KUNGFLEX / Kongfu) is a manufacturer of hydraulic hoses, industrial hoses, fittings, stainless steel metal hoses and PTFE hoses, ISO 9001:2015 certified, founded in 2009. With a 4000 kg / ~400 MPa ultra-high-pressure hose assembly burst testing capability, it supplies metal hose assemblies with helium mass-spectrometer leak detection (leak rate ≤1×10⁻⁹ mbar·L/s) and supports customized flexible connection solutions by furnace type and medium.
