Quick Disconnect

10 things we have learnt about snap couplings

How there are lots of good things about quick disconnects but a few bad.

Picture Above: A typical male and female quick disconnect pair from Snaptite/Parker

Quick disconnects or “snap couplings” are indispensible for hydraulics professionals.

Where would you use them?

Either where you need to swap around hoses, cylinders, pumps and other components everyday or where you need to be able to swap out or modify a system easily in the longer term. You are just snapping together the male probe and female coupler to provide a quick and leak tight connection. You also need to prevent contamination entering a system.

A few examples might be:

• You have a swaging tool using two Enerpac cylinders and need to swap between one and the other without using spanners. Fit quick disconnects and do the job in seconds.
• You have a water pressure test pump and need to boost productivity. Fit stainless quick disconnect fittings and you can test components in quick succession by putting a mating fitting on a run of parts. A cheap boost to productivity!
• Send a service engineer a hundred miles to “fix” a machine.” Much easier if he only has to un-snap an assembly, snap in a new one and run the unit up again.

Add in all the other users of quick disconnects for areas outside the mainstream hydraulic world and you are talking of a massive market. Air quick connect fittings and air quick connect hose fittings are the mainstay of most engineering shops. Water quick disconnect fittings and propane quick disconnect fittings are others that we have all used. Even fuel systems use fuel quick disconnect fittings.

Picture Above: Quick disconnect on a Hitachi excavator http://www.hitachicm.co.uk/

Why?

You use quick disconnect couplings to eliminate spillage and take away the need to bleed systems through again when reconnecting. Add in the ability to de-skill the connections on a complex hydraulic system by using a mixture of male and female quick disconnects, different sizes or even just colour coding or labelling and you have a great time saver. Even our workhorse 316 Drum pump could easily be fitted with quick disconnects for no-spill connection.

Industry standard sizes or odd-balls? Or why wouldn’t you use ISO/DIN interchange?

The big players tend to offer their own unique profiles and also ISO or DIN industry standards as well. If it is your own kit and you have decent stocks of replacement couplings, and are not going to be left high and dry if the supplier is sold out, we don’t think it particularly matters. Some particular series and shapes are entrenched in particular industries and pieces of equipment. We don’t mind buying a specific Hansen coupling from Guyson for an aircraft cowl reverser pump but start to get nervous when very specialist aerospace couplings are a few thousand pounds each on 14 weeks lead time. Maybe having more than one supplier of a particular coupling is a better strategy. The Holmbury ISO/DIN guide is good on http://holmbury.com/gb/products/iso-and-din-couplings/

Mainstream suppliers or cheap?

There must be lots of people who judge a coupling to be just a “commodity” but our take is why would you risk an expensive system by skimping on parts? We would focus in on Parker, Hansen, Snaptite, Cejn and the big players and pay a modest premium.

Links have been provided at the end of the blog and we apologise if we have left anybody out.

Snap couplings don’t leak. Really?

That may well be right, but after a certain amount of use, they do wear and weep. Our tip is that if you have a system that needs to be zero leakage and you have too many quick disconnects in the system or ones being used a lot, you are taking a risk.

Flat face?

After 30 years, we reckon contamination is the number one risk on faulty hydraulics. If you can wipe off a flat face on the male and female before connecting that is a big plus for us. The pioneers, Holmbury, are still very good with these, although most of the other manufacturers do flat face as well now.

Picture Above: A selection of Holmbury flat face couplings

Buy exactly what you need.

Brass, plated carbon steel, 303 stainless, 316 stainless, assorted seal compounds and even the ability to cope with vacuum. Yes, you can specify exactly what you need. There is still a place for a specialist supplier who really knows their stuff. We know our hand pumps. Actually talk to somebody who knows quick disconnects.

Get caps and plugs ordered as part of the kit?

If contamination is a big issue, why would you not spend pence on a plastic dust plug or dust cap. Couplings with no protection being dragged along a concrete floor are a sad and worrying sight.

Picture Above: Caps and plugs from Parker

Get couplings working for you!

They may be low tech but can be so handy in design. Lots of actuators in the field? Just buy one Sarum Micropac (http://www.sarum-hydraulics.co.uk/ ) pump trolley unit fitted with hoses and a female coupler on the free end. Fit the cheaper male probe to each actuator and one pump will operate lots of individual actuators. Even better, use a pair of couplings swapped backwards and forwards to allow you to dispense with an expensive four way directional valve. Or use males and females of different sizes to deskill connecting something up.

Picture Above: Micropac Ground Support oiling trolley complete with Snaptite coupler.

Try to recycle knowhow or people will learn the hard way!

Never connect or disconnect under pressure. Always make sure that the knurled ring is screwed right home to unseat the ball on those 700 bar Safeway type couplings used pretty universally on 700 bar gear. Lots of stuff like this needs to be shared with people who are learning.

As always, feel free to comment or correct our blog.

Snap couplings are a great product to use in conjunction with our gear here in the Pump Shop Pro shop or with the bigger range of Micropac hydraulics. Our 3 Metre hose can easily be fitted with stainless steel quick disconnects. For us, quick disconnects are another part of the productivity story.

Useful Links

-Parker Hannifin on http://ph.parker.com/us/en/quick-couplings-and-accessories

-Cejn on http://www.cejnuk.com/

-Hansen on http://www.guyson.co.uk/hose-couplings/hansen-quick-release-couplings

-Snaptite (now part of the Parker family) on http://www.snap-titequickdisconnects.com/

-Holmbury on http://holmbury.com/gb/holmbury/