POPPET VALVE SYMBOL AMBIGUITY

[Oilyguy90]

Hello,

Please refer to the attached hydraulic symbols for 3 way 2 position poppet type direction control valves. My question is regarding the orientation of the check valve symbol on the different ports. Manufacturers sometimes show the arrow of the check valve on the 'T' port to be pointing downward. What does this mean and does this matter? Does this indicate some sort or anti-cavitation function? If so, where is the anti-cav oil being delivered to? Is this any different in function from a manufacturer who shows the arrow pointing up on the 'T' port?

Furthermore, I am looking for a hydraulically actuated 3/2 poppet valve as shown attached. Can someone please recommend a valve model from a reliable manufacturer for the same. I do not care about mounting style. 300 bar working pressure and low flow application. Any help would be appreciated.

 

[MikeHalloran]

The symbols as drawn seem like nonsense to me.


Mike Halloran
Pembroke Pines, FL, USA

 

[73lafuite]

You can use Hawe component
valve réference NBVP16
data sheet D7765N
Symbol is correct on this data sheet
If you can have overflow (accumulator): you must put orifice(s) in the port(s)

 

[Oilyguy90]

Hi 73lafauite,

Thank you for your response. I was of the opinion of using the same manufacturer (HAWE) but have been referring a different datasheet D7300. I have attached this here for your reference. If you look at "Table 1: Flow Pattern" on page 2; under "3/2-way valves", you will find symbols '3' and 'Z3'. What I am confused about is the direction of the check valves in the two symbols. Is the 'P' to 'A' connection blocked on actuation of Z3? Also in D7765N, Table 2: 'Y' symbol, why is there a check valve symbol on the flow direction arrow? Not sure which valve I should use of these two. Leak free operation is critical for my application. Below I will briefly mention my application..

Application: Piloting of logic cartridge valve
In un energized condition, P connected to A and holding 300 bar load pressure. There should be no leakage from P/A to T. When energized, P should lock shut under load and A should vent to T. Therefore only momentary flow exists at the time of venting to tank.

Connections:
Connected to Port P = Annulus chamber of cylinder which is pressurized due to load
Connected to A Port = Spring chamber of logic cartridge valve
T = Direct tank return line
No. of hydraulic cylinders in circuit = 2

I am considering using either one solenoid operated valve to give pilot signal to two hydraulically actuated valves which inturn vent logic cartridge valves(since cylinders are close to sea water) or directly controlling both logic cartridges by a single solenoid operated valve. In the later case I end up pressurizing a loop of pipeline/hose unnecessarily during load holding but simplifies circuit and reduces cost.

Features:
D7300 = Ball seated valves; pressure drop in the direction of flow, P>A,B>R
D7765N = Cone seated valves, any flow direction, internal pressure compensation

Since both the above are negatively overlapped type, will be using orifice as suggested by you as I am using accumulator.

Hope the above is clear and would appreciate your feedback!

 

[73lafuite]

Do not worry the D7300 or D7765 distributors have no internal leaks, even if the symbol on D7300 is poorly represented.
The differences :
D7765 can have the flow in any direction so pressure in A can be higher than pressure in P. It is a balanced spool with check, in the D7300 it is a ball with push button.
D7765: much cheaper in 24V than D7765, standard mount Cetop 3, and also less sensitive to oxidation and humidity. On the other hand, it does not have the small filtration screen in the orifice P.
Often for your type of application I use a 2-way distributor (EM at hawe or WSM at hydac) that exists in all manufacturers. I put a nozzle between the B and the X of the cartridge. And I put the 2-way distributor between the X and the A.

Hydraulically operated valves are expensive. Why not put one electro-distributor per cartridge?
Also pay attention to temperature variations in systems without internal leakage: the pressure increases by 10bar per ° Celsius.

 

[Oilyguy90]

Hello 73lafuite,

Many thanks for your quick response! Please find my replies in Red below:

Do not worry the D7300 or D7765 distributors have no internal leaks, even if the symbol on D7300 is poorly represented.
Great! I thought there was something I was missing with the weird check valve orientations.

The differences :
D7765 can have the flow in any direction so pressure in A can be higher than pressure in P. It is a balanced spool with check, in the D7300 it is a ball with push button.
D7765: much cheaper in 24V than D7765, standard mount Cetop 3, and also less sensitive to oxidation and humidity. On the other hand, it does not have the small filtration screen in the orifice P.

Often for your type of application I use a 2-way distributor (EM at hawe or WSM at hydac) that exists in all manufacturers. I put a nozzle between the B and the X of the cartridge. And I put the 2-way distributor between the X and the A.
Why put 2 way distributor between X & A? Shouldn't it be between X and Tank so that on energizing the 2/2, you vent spring chamber of cartridge (X) to tank, thereby allowing allowing flow from port B (cylinder annulus) to A? I was thinking of a similar solution to my problem by using nozzle as mentioned by you and a Pilot check valve between 'X' and tank. Therefore when pilot signal is given to Pocv, X is vented to tank. However in my application (split barge hull), cylinder has regeneration from annulus to bore during extension and the cylinder also wants to open under its self weight. Therefore if bore pressure in practice is not high enough (thereby pr drop across nozzle is not high enough), I run the risk of the cartridge valve chattering. Also as the pr drop across orifice depends on flow passing through it, I run the risk of contamination blocking the nozzle.
The reason I chose PoCV instead of 2/2 solenoid was because I want to directly mount logic cartridge on cylinder annulus port to prevent hull suddenly opening in case of hose burst. Therefore did not want to keep a solenoid valve on my powerpack or somewhere between PP and cylinder as the entire length of hose/pipe till the 2/2 would be pressurized.

Now I think I have a solution. I am going to mount 3/2 solenoid valve directly on logic cartridge. this manifold (1 for each cylinder) will be close to but not mounted on cylinder. It would therefore take 2 hose bursts simultaneously for hull to drop open suddenly. A single hose burst would mean all the weight goes to other cylinder. As both cylinders have annulus to bore relief for thermal expansion, the hull would only gradually open partially.


Hydraulically operated valves are expensive.(& virtually impossible to locate ex-stock in India)Why not put one electro-distributor per cartridge? Putting One 3/2 for each logic element as mentioned above.
Also pay attention to temperature variations in systems without internal leakage: the pressure increases by 10bar per ° Celsius.
Taken care of Have dealt with the consequences once! Lol

Thank you for your help. Much appreciated. Do let me know if you have any suggestions for what I have mentioned above or if something isn't quite clear.

 

[73lafuite]

Hello,

I think your analysis is very good and it will work well.

It is good, if possible, to put the 2-way distributor between X and tank. It depends on your need and the schema I do not know.

However, if the 2-way valve is placed between X and A, the flow can pass from B to A. Simply the pressure drop in the logic valve is that of the logic valve spring until the pressure drop of the flow reaches the taring of this spring. And if an anti-return valve is added in the P of the 2-way valve then the flow can pass from A to B.

Prefer in your application a area ratio 2: 1 for the logic valve

Cordially