Solvents are almost the easiest media on this site for the metal and among the most demanding for everything else. Toluene, acetone, MEK, IPA, hexane and the rest do essentially nothing to austenitic stainless. They are volatile, they are flammable, they carry static, and they get through joints that hold water without difficulty. On this duty the hose is the simple part.
What this service does to a hose
Static, and a low-conductivity liquid. Most industrial solvents conduct electricity poorly, which means charge generated by flow does not bleed away — it accumulates. The charge separates at every interface: pump, filter, hose wall, the free surface in the receiving drum. Add a flammable vapour in the headspace and the ignition energy required is very small. A braided stainless assembly with welded end fittings is electrically continuous from flange face to flange face and bonds itself, which is a real and underrated advantage over the alternatives here — but only if every fitting in the run is metallic and every joint is made. One non-conducting coupling defeats the whole path. See anti-static and bonded assemblies.
Vapour pressure and the joints. Solvents have low surface tension and high vapour pressure. A threaded joint sealed with tape will pass solvent vapour. On a flammable duty that is a classified-area problem, not a housekeeping one.
Chlorinated solvents are the exception to “solvents are easy”. Perchloroethylene, trichloroethylene and methylene chloride can hydrolyse in the presence of water to release hydrochloric acid, and at that point the duty stops being a solvent duty and becomes a chloride one. If there is any water in the system, say so.
The bore matters for cross-contamination, not corrosion. On a multi-product line — a paint kitchen, a resin plant — the corrugation valleys hold the previous batch. Where that is a quality problem rather than a corrosion one, the answer is still a smooth bore.
What we would fit
| Element | What we would supply | Why |
|---|---|---|
| Hose | 316L annular corrugated for the great majority of solvents | The metal is comfortable; nothing more expensive is justified |
| Bore | PTFE smooth bore on multi-product lines or where full drainage is required | For cleanability and changeover, not for corrosion |
| Braid | 304 or 316 wire; double where the assembly is handled | Drum and IBC decanting lines are handled duty |
| Ends | Flanged or welded in preference to threaded, with the assembly continuous to earth | Threads pass vapour and can interrupt the bond path |
| Bonding | Continuity across the assembly verified and certified where the area is classified | It is a measurable property, so we measure it |
What we would not fit, and what happens
An assembly with a non-conducting coupling anywhere in the run. The bond path is only as good as its worst joint.
Threaded joints on a volatile flammable solvent. They pass vapour.
Bare stainless on a wet chlorinated solvent. The hydrolysis product is hydrochloric acid.
Interlock hose. Not pressure-tight, on a flammable liquid.
What we need to size it
| We need | Because |
|---|---|
| The solvent, by name, and whether it is chlorinated | Chlorinated plus water is a different duty entirely |
| Whether water can be present in the system | It is what turns a chlorinated solvent aggressive |
| Area classification and the bonding requirement | It decides whether we certify continuity and to what limit |
| Whether the line carries more than one product | It decides whether the bore has to drain fully |
| Working pressure, temperature and flow rate | The ordinary three, still required |
| How the assembly is handled — fixed, or connected and broken | Handled assemblies get double braid and guarded ferrules |