Hydraulic hoses - Metric vs BSP pro's and con's

[sonyduo]

At the moment we utilize all BSP hoses but we are told that we should be looking at moving to metric hose ends to replace these. Fitting solutions and sealing solutions seem to be a good advantage but after a lot of searching on Google and reading many articles and product literature we are still struggling to weight up the pro's and con's for either option. Comments and opinions are really welcome as we are leaning towards moving to metric ends but we would like some real justification to do this.

 

[hydromech]

I always tended towards metric hose ends because it is much easier to adapt between flexible and rigid tubing. It reduces the number of potential leak paths. Other than there is not much in it. Neither is being phased out as far as I understand. The pressure limitations on both are comparable and both are available with fixed or swivel ends. The difference in the type of fitting arrangement would not justify the cost of a wholesale swap from BSP to metric ends. However, for a new build, I would move on with metric ends.

Adrian

 

[Oldhydroman]

Sonyduo
There are many, many different standards for hose ends - so let's be clear about what you're asking.

Would it be correct that you are currently using hoses with BS 5200 / ISO 12151-6 BSP female-swivel-nut ends with a male "60 degree" cone inside the swivel nut? And would it also be correct that you are considering changing to hoses with a DIN 2353 / DIN 20066 / ISO 12151-2 metric female-swivel-nut with a male "24 degree" cone inside the swivel nut. These “metric” hose ends hoses would match the metric pipe work and the series of the fitting [light range (L) and heavy range (S)]?

If so, then the value of the tips I would give depend on whether you are making hoses assemblies for yourself or buying them in from your local hose supplier. In fact, all I can offer you are some observations and it depends on your particular circumstances whether or not this information will sway you.

Remember, the full range of BSP hose ends would be: G1/8", G1/4", G3/8", G1/2", G5/8", G3/4", G1", G1-1/4", G1-1/2" and G2". The G1/8" size isn't much used and, in industrial applications, the G5/8" size isn't much used either. So that's just 8 sizes you would need to keep in stock (or order regularly). In the world of DIN type hose ends, to cover the full range you would need to stock: 6L, 8L, 10L, 12L, 15L, 18L, 22L, 28L, 35L, 42L, 6S, 8S, 10S, 12S, 14S, 16S, 20S, 25S, 30S, and 38S. So that's 20 sizes (not counting the LL range of hose ends) and even then this range doesn't go as big as the G2" hose end.

Generally speaking, the range of [readily available] BSP hose ends to match each hose bore would be: size-on-size, one size below and one size above. For example, for a 1” bore hose you would normally expect to fit a 1” BSP hose end, but you would easily be able to get a 3/4” BSP hose end or a 1-1/4” BSP hose end to fit the same hose bore.

For the DIN hose ends the range is often more limited: typically size-on-size and one size above. And be aware that some suppliers match the bore of the hose to the typical bore of the tube for the “size-on-size” configuration. So if you were using 25 mm OD tube you would expect your DIN fittings (male stud couplings, female stud couplings, stud standpipes and banjos) to be available with 1” BSP ends. There are often more variations available with the male stud couplings (25 mm-1/2” BSP, 25 mm – 3/4” BSP & 25 mm – 1-1/4” BSP) but on the other fittings there isn’t usually much choice. On the hose ends though, you might find that the “standard” hose end to suit a 25S fitting actually goes on a 3/4” bore hose (because the bore of your 25 mm OD pipework will be closer to 3/4” than 1”).

An issue which sometimes occurs is when your hose needs two elbows and you have to ensure the correct orientation between the elbows at each end. Sometimes this is impossible to know or you need some sort of adjustability after the hose has been installed (if it is being threaded through a tortuous route). In the world of BSP you would have one elbow on the hose but make the other end straight. Onto this straight end you would fit a male/female-swivel-nut elbow adaptor. The choice of BSP hose end adaptors is extensive and they are readily available (swept 90 deg, compact 90 deg, swept 45 deg, compact 45 deg). In the world of DIN when the same situation occurs the fitting you use as the hose end adaptor would be an adjustable tube elbow. These are only available in the compact configuration (no “swepts”) … and the 45 degree ones might not be readily available. In defence of the DIN solution though, the pressure ratings of the DIN fittings are well established and quite impressive but the BSP adaptors have surprisingly low pressure ratings (especially in the larger sizes).

If you need a banjo end on your hose you can get a BSP banjo end quite readily, but if you want to stick to DIN hose ends you would have to use a straight hose end and a separate tube banjo. You can get a BSP banjo adaptor to use with a straight BSP hose end but these are rare and expensive.

To connect your hoses to your pipework ends you need some sort of adaptor. To connect the DIN end hose to the metric pipe you would use a simple tube union (or elbow). Any jump in size can be accommodated by: having the non-standard fitting on the hose end (limited number of non-standard variations), using an unequal tube union (sometimes long delivery), or using an equal tube union (or elbow) with a tube reducing adaptor. To connect the BSP swivel nut end to the pipework you would use a male stud coupling with a 60 deg internal cone (try to use the form A fitting for neatness). A greater variety of size combinations is available with the male stud couplings and also with the BSP hose ends so you might be able to accommodate quite a jump in size without having a whole multitude of fittings to tighten (or leak).

To connect your hose end into a DIN tube fitting (such as a tee branch in a tube run) then the DIN hose end is ideal. The BSP hose end will still require an adaptor – and the simplest solution is to use a straight standpipe with a BSP coned end. Avoid using the plain standpipe hose end because you can’t have this hose pressure tested until its end has been made off.

Where I work we actually use both types of hose end – taking the view that there’s very little difference in price of the hose ends so we use whatever is most convenient for the installation. We have, in the past, made up our own hose assemblies but used a Kanban system for the hose ends so the increased stock requirements [by using both types of ends] didn’t appear as a direct cost. More recently, we have been concentrating on building our own product and getting our local hose company to make the assemblies for us – so we just ask for whatever we want and let them worry about stocking levels (there’s a lot more than just BSP or DIN hose ends so it makes no difference to our supplier which type of end we ask for).