Stainless hydraulic fittings for mining machinery and mineral processing lines

Hydraulic and process lines at a mine site

• Underground coal and ore mines: emulsion pump stations and distribution lines for powered roof supports, shearer loader and armored face conveyor hydraulics.
• Underground machinery: cylinder and motor lines on underground loaders (LHD), jumbo drill rigs, roof bolters and roadheaders.
• Open-pit mines, stone and marble quarries: hydraulics on excavators, loaders, haul trucks and drill rigs; hoses on hydraulic breaker attachments.
• Crushing and screening: adjustment and clearing cylinders on cone and jaw crushers, conveyor and folding hydraulics on mobile crushing and screening plants.
• Mineral processing: flotation reagent dosing, leach solution distribution, filter press closing hydraulics, drainage and dust suppression lines.

Where does stainless steel make a difference?

Heavy machinery mostly comes with plated carbon steel fittings, and in dry, sheltered areas these may be sufficient. Stainless steel makes a difference at points where the connection stays permanently wet, is exposed to corrosive water or is frequently disassembled:

• Acid mine drainage: the oxidation of sulfide minerals such as pyrite by air and water acidifies the water; carbon steel fittings and clamps corrode rapidly in this water.
• Chloride-bearing water: saline groundwater in deep mines, or brackish water or seawater used as process water, increases the chloride load.
• Water-based fluids: roof support emulsion also creates a risk of corrosion on the inner surface of carbon steel fittings.
• Reagent and washdown lines: reagents, milk of lime and wash water attack the inner and outer surfaces at the same time.

In most of these environments, AISI 316L lasts far longer than carbon steel; however, as chloride levels rise, pH falls and temperature increases, the risk of pitting and crevice corrosion grows, particularly in stagnant gaps such as under seals and at clamp contact points. Share the pH, chloride content and temperature of the water in your quote request; since our raw material is AISI 316/316L, also state it if the specification calls for a different material.

Underground: emulsion, seal compatibility and safety requirements

Powered roof support systems generally run on a fire-resistant, water-based emulsion (HFA); this fluid lubricates less well than mineral oil, and seals should be selected to suit the fluid. Phosphate ester fluids are incompatible with NBR seals, and water-glycol fluids with zinc and cadmium plating. The roof support units' own quick-connect system is governed by the equipment manufacturer's standard; GÜNEYSS contributes on pump station, distribution and filter lines, test points, and adapters and transition pieces.

In coal mines, the flame-retardant and antistatic properties of hoses, and in mines with firedamp the requirements for explosive atmospheres (ATEX Group I), are subject to the relevant regulations and the operator's occupational health and safety requirements; they should be stated in writing in the quote request.

Fitting type by machine and line

Vibration, impact and hose abrasion

Hydraulic breakers, drills and crushers generate constant pressure fluctuation and vibration in the line; hose type (wire-braided or spiral-reinforced) and pressure rating should be selected with the frequency of pressure impulses in mind as well. The outer cover of a hose rubbing against rock or the edge of a chassis wears quickly; an abrasion sleeve, a spiral guard and correct clamp spacing extend its service life. An anti-seize compound should be used on stainless steel threads to prevent galling, and connections on vibrating lines should be checked at every maintenance.

Mineral processing: reagents, leaching and process water

In flotation, collector, frother and depressant reagents are fed at low flow rates with precise dosing; on metal-tubed dosing lines, stainless steel tubing, twin-ferrule fittings, needle valves and check valves can be used. In heap leaching, the solution varies with the ore: acidic solutions are used for copper and alkaline cyanide solutions for gold. With reagents such as sulfuric acid, the behavior of stainless steel depends on concentration and temperature; compatibility should be confirmed against the plant's process data and specification. The closing hydraulics of filter presses also work in a wet, muddy environment.

A spares list for remote sites

A mine is often far from its suppliers; a spare in the wrong size can leave a machine idle for several shifts. We recommend preparing a spares list for each machine that includes hose assembly, adapter, O-ring and valve sizes, and keeping critical items on site. In an emergency, send a photo of the part taken next to a caliper, the thread size and the quantity via WhatsApp; stock availability and thread type are confirmed by message, and a sample is requested for unclear threads. Unobtainable adapters and flange blocks for machines that are out of production can be remanufactured from samples.