How to Select a Hose

To help determine the proper hose for an application, use the acronym:

STAMPED - from Size, Temperature, Application, Materials, Pressure, Ends, and Delivery.

Here is what to consider in each area:

SIZE - To select the proper hose size for replacement, it is important to measure the inside and outside hose diameters exactly using a caliper, as well as the length of the hose. Hose OD is particularly important when hose-support clamps are used or when hoses are routed through bulkheads. When replacing a hose assembly, always cut the new hose the same length as the one being removed.

If known or can select for application. The hose I.D. must be sized accurately to obtain the proper flow velocity.

NOTE: Changes in hose length when pressurised range between +2% to 4% while hydraulic mechanisms are in operation. Allow for possible shortening of the hose during operation by making the hose lengths slightly longer than the actual distance between the two connections

TEMPERATURE - All hoses are rated with down to a minimum -58° (-50°) F/C maximum working max temperature ranging from 200° (93°) to 400° (204°) F/C based on the fluid temperature.

Both media temperature (the temperature of the media conveyed through the hose) and the ambient temperature (the temperature around the hose where it is being used) need to be considered when selecting the hose.

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Exceeding these temperature recommendations can reduce hose life by as much as 80%. Depending on materials used, acceptable temperatures may range from -65° F (Hytrel and winterised rubber compounds) to 400° F (PTFE). External temperatures become a factor when hoses are exposed to a turbo manifold or some other heat source.

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When hoses are exposed to high external and internal temperatures concurrently, there will be a considerable reduction in hose service life. Insulating sleeves can help protect hose from hot equipment parts and other high temperature sources that are potentially hazardous. In these situations, an additional barrier is usually required to shield hydraulic fluid from a potential source of ignition.

APPLICATION - Will the selected hose meet bend radius requirements? This refers to the minimum bend radius (INCHES/MM) that a hydraulic hose must meet.

Route high-pressure hydraulic lines parallel to machine contours whenever possible. This practice can help save money by reducing line lengths and minimising the number of hard-angle, flow-restricting bends. Such routing also can protect lines from external damage and promote easier servicing.

MATERIALS - It is mandatory to consult a compatibility chart to check that the tube compound is compatible with the fluid used in the system.

E.g., petroleum-based hydraulic fluids, raw water, water/glycol, and water/oil emulsion hydraulic fluidsISO Viscosity Grade: 32, 46, 68,… 220, 320

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Elevated temperature, fluid contamination, and concentration will affect the chemical compatibility of the tube and fluid. Most hydraulic hoses are compatible with petroleum-based oils. Note that new readily biodegradable or green fluids may present a problem for some hoses.

PRESSURE CAPABILITIES - Hose working pressure must always be chosen so that it is greater than or equal to the maximum system pressure, including pressure spikes.

Other info? E.g., surge pressures and spikes

ENDS - HOSE ENDS - The coupling-to-hose mechanical interface must be compatible with the hose selected. The proper mating thread end must be chosen so that connection of the mating components will result in leak-free sealing.

A caliper can measure both inside and outside dimensions of the threads. ODs are measured on male couplings, while IDs are measured on female couplings.

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In most situations, the only differences between an SAE coupling and an imported coupling are the thread configuration and the seat angle. International thread ends can be metric, measured in mm, but also include BSP (British Standard Pipe) threads, which are measured in inches. Knowing the country of origin provides a clue as to what type of thread end is used. DIN (Deutsche Industrial Norme) fittings began in Germany and now are found throughout Europe, while BSP is found on British equipment. Japanese Komatsu machinery uses Komatsu fittings with metric threads, while other Japanese equipment most likely uses JIS (Japanese Industrial Standard BSP threads), or, in some cases, BSP with straight or tapered threads.

Three determinations are required to identify these couplings correctly:

• Type of seat - inverted (BSPP & DIN), regular (JIS & Komatsu) or flat (flange, flat-face)

• Seat angle - 30° (JIS, BSP, DIN and Komatsu) or 12° (DIN), and

• Type of threads - metric (DIN or Komatsu), BSP (BSPP, BSPT or JIS), or tapered (BSPT or JIS Tapered)

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SAE standards relating to hydraulic/pneumatic fittings and assemblies specifically designed to eliminate leakage include:

• J514 - straight thread ports/fittings

• J518c - 4-bolt flange ports/fittings, and

• XJ1453 - the number provisionally assigned to O-ring face seal fittings.

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