Help with Hydraulic Couplings

[mjo]

I was looking through an online catalog at some hydraulic fittings and had a few questions. How difficult are they to disconnect? Do the coupling ends close up when they are disconnected or would I need a valve in there to stop flow once I uncouple them?

Here's the catalog: hydraulic fitting

 

[mjo]

Specs on these couplings are:

Mating Half (Base #): Any BVHC4 Coupler

Maximum Working Pressure: 2,250psi (155 bar)

Seal Material: Buna-N (Nitrile)
Temperature Range: -40 Degrees to 250 Degrees F (-40 Degrees to 120 Degrees C)
Valved(Checked) Or Plain(Free Flowing): Valved
Valving Style: Poppet


Thanks.

 

[Pete C.]

The ones pictured will NOT cut off oil flow. There are ones with a built-in check valve. Simple to identify, you can't see through them.

 

[Gary Allan]

You need shut off couplers. There are single shut off and double shut off couplers. As implied, one will shut off the supply (if you've installed it on the correct hose) and the other style will prevent flow from both connectors.

I'm sure that I haven't seen them all ..but those that I used looked more like this

This is what was on a hydraulic driven sump pump with about 40ft of hose.

 

[mjo]

OK.

I've noticed that most of the couplers are made of some sort of steel. All of the pipe fittings that I have are made of brass. Would it be safe to assume it's fine to connect steel with brass because of the layer of teflon tape separating them? I've heard that when two dissimilar metals are in contact, one of them will corrode very quickly.
Although, from reading this website DOT
it looks like brass and steel may be compatible?

 

[Gary Allan]

I mix brass, steel, stainless steel, and aluminum without too much of a concern. I haven't noted any bimetal corrosion ...but I've used tape and dope where appropriate just for sealing purposes.

 

[mjo]

Thanks for the info, Gary.

I did some research of my own and after looking at the conductances of other oils (olive oil, hydraulic oil, etc) the conductance of the oil must be negligible. The corrosion concerns have to be for only water pipes because water is much more conductive than oil - especially if it contains minerals. For those that don't know, when two different metals come in contact, they make a battery the voltage of which increases with temperature. Examples are a thermocouple or shottkey diode. But the electrical current is microscopic because of the teflon tape and oil.

I bought some expensive Hansen hydraulic couplings on Ebay for a cheap price and am anxiously awaiting them. Their specs are way overkill so I don't have to worry about them leaking. With these dudes I can make some very interesting filter setups. I can disconnect one instantly if it leaks or just remove them all if I have to take the car to a mechanic. Oh the possiblities!

 

[Gary Allan]

Yes, the possibilities

 

[porcupine73]

That pic you posted mjo is for underground pipeline cathodic corrosion. The soil acts as an electrolyte thus providing a current path and resulting in corrosion. You wouldn't have an 'electrolyte' around your connectors so you should be fine.

The DOT has regulations for underground pipeline cathodic protection (using sacrificial metal pieces which corrode instead of the pipeline) because a rupture due to weakening from corrosion could be hazardous and even deadly depending on the product and pressure.