In a quarry, a hydraulic leak is a product-spec failure.

A common hydraulic cause is loss of internal pressure in the clamping cylinders. Those cylinders hold the adjustment ring; if pressure is lost the hydraulic lock breaks, the ring slips and the setting drifts wider, so the plant starts producing oversized, out-of-spec material. It usually shows up as a product-quality problem before anyone investigates it as a hydraulic one.

Both are four-spiral constructions to EN 856, with four layers of high-tensile wire laid in parallel spirals rather than braided. 4SH uses a heavier wire gauge than 4SP, which supports a higher working pressure at the same inside diameter. Both exist because spiral construction survives repeated pressure impulses far better than braid.

ISO 18752 classifies hose by pressure class and by impulse grade rather than by reinforcement type. The grades, A to D, are defined by the number of impulse cycles the hose must survive at a stated temperature and impulse pressure. Grade D is the most demanding, requiring over one million impulse cycles at 120 degrees Celsius at 133% of maximum working pressure. Note that ISO 18752 covers the hose and hose assembly, not the end connections, so the coupling has to be qualified separately.

Three things, in order of impact. Route and clamp so hose does not rub on hose or on steel, which SAE J1273 covers directly. Specify a cover with abrasion resistance tested to ISO 6945 rather than described in marketing language. And sleeve the contact points that routing alone cannot eliminate.

No. A hose can comfortably pass a burst test and still fail within weeks on a breaker circuit, because the damage mechanism is impulse fatigue rather than a single over-pressure event. Specify by impulse grade under ISO 18752, or by a spiral construction such as EN 856 4SP or 4SH which exists for exactly this duty.

Both are tapered at the same 1:16 rate, but the thread form angle differs, 55° for BSP and 60° for NPT. In several common sizes they will screw together and appear correct, then weep under pressure because contact is incomplete. BSPP, by contrast, is a parallel thread that seals on a bonded seal against the port face, so without that washer it will not seal at any torque.

Four-bolt split flange to SAE J518 is part of our fittings range, with Code 61 as the standard series and Code 62 as the high-pressure series, corresponding to ISO 6162-1 and ISO 6162-2. Send the size, pressure rating and port standard and we will confirm what we can hold. Note that flange heads are interchangeable across SAE J518, DIN 20066, ISO 6162 and JIS B8363 except for bolt sizes.

Be careful with this question, because the answer is jurisdictional. Underground coal in the United States carries specific flame-resistance obligations for hose covers and minimum burst requirements, administered under MSHA, and Indian mines fall under DGMS instead. We do not make a blanket flame-resistance claim. Tell us the exact regulatory requirement your site is held to and we will tell you honestly whether we can meet it.

Yes, and that is the normal route. Share a drawing, a specification or a sample and we confirm dimensions, material, thread standard and pressure rating in writing before production. Where a requirement is beyond what we can reliably hold, we say so at that point rather than after the order.

Tell us anyway. We supply hydraulic valves, fittings and hose pipes. If your requirement sits inside that we would like to take it on, and we will tell you exactly what we can hold and what we cannot. If it sits outside, you will hear that from us up front rather than three weeks into a quote, and where we can we will point you toward a route more likely to work.