FSFAXAV - Closed center, flow divider-combiner valve
Part Number: FSFAXAV
Manufacturer: Sun Hydraulics
Closed-center flow divider/combiners are sliding-spool, pressure-compensated devices used to split flow in one direction and combine flow in the opposite direction. These valves may be used to accurately control two or more cylinders or hydraulic motors where bidirectional operation is required.
- All flow divider and divider/combiner cartridges are physically interchangeable (i.e. same flow path, same cavity for a given frame size).
- Operating characteristics cause the leg of the circuit with the greatest load to receive the higher percentage of flow in dividing mode. If a rigid mechanism is used to tie actuators together, the lead actuator may pull the lagging actuator and cause it to cavitate.
- In combining mode, compensating characteristics will cause the leg of the circuit with the lowest load to receive the higher percentage of flow. If a synchronization feature is not included, an additive accuracy error will be experienced with each full stroke of the actuator.
- In applications involving rigid mechanisms between multiple actuators, operating inaccuracy will cause the eventual lock-up of the system. If the mechanical structure is not designed to allow for the operating inaccuracy inherent in the valve, damage may occur.
- In motor circuits, rigid frames or mechanisms that tie motors together, and/or complete mechanical synchronized motion of the output shaft of the motors, either by wheels to the pavement or sprockets to conveyors, will contribute to cavitation, lock-up and/or pressure intensification.
- Variations in speed and lock-up can be attributed to differences in motor displacement, motor leakage, wheel diameter variance and friction of wheels on the driving surface.
- Extreme pressure intensification can occur on multiple wheel drive vehicles.
- Flow between ports is limited to spool leakage. This does not provide leak proof holding capability, but can be useful in minimizing cross flow and drift.
- Divisional and combining accuracy are equal.
- Below the minimum flow rating there is not enough flow for the valve to modulate. It is effectively a tee. If flow starts at zero and rises, there will be no dividing or combining control until the flow reaches the minimum rating.
- Incorporates the Sun floating style construction to minimize the possibility of internal parts binding due to excessive installation torque and/or cavity/cartridge machining variations.
|Capacity||12 - 60 gpm45 - 240 L/min.|
|Maximum Operating Pressure||5000 psi350 bar|
|Divisional Accuracy at Minimum Input Flow||50% ±4.5%50% ±4.5%|
|Divisional Accuracy at Max Input Flow||50% ±2.5%50% ±2.5%|
|Pressure Drop at Minimum Rated Input Flow||30 psi2 bar|
|Pressure Drop at Maximum Rated Input Flow||350 psi24 bar|
|Valve Hex Size||1 5/8 in.41,3 mm|
|Valve Installation Torque||350 - 375 lbf ft475 - 508 Nm|
|Model Weight||2.80 lb1,30 kg|
|Seal kit - Cartridge||Viton: 990-034-006|
|How big is a drop of hydraulic oil?||There are exactly 250 Sun drops in a cubic inch or 15 in a cc.|
|Can I synchronize 2 cylinders with Sun's divider-combiner?||No. Synchronizing 2 cylinders hydraulically is a real problem. A real problem is one which has no solution. Our valves with the synchronizing feature don't synchronize, they provide an error correction at each end of the stroke when the leading cylinder bottoms out. Another means of error correction is cross-port reliefs.|
|How has Sun solved the hook breaking problem?||We eliminated the hooks. We have a 1 piece spool.|
|Most of Sun's divider-combiners will do better than the published specs, won't they?||No. Almost all of the error percentage we publish is due to flow forces. Even with a mechanically perfect valve you would see most of the variation.|
|Most of the dividing-combining inaccuracies will average out, won't they?||Absolutely not. The bell curve does not apply here. In the dividing mode the high pressure leg gets the higher flow and in the combining mode the high pressure leg is the lower flow......every time. The inaccuracies are always there and they accumulate. The high pressure leg goes up farther and comes down less, every time.|
|What is the synchronizing feature?||It is a static error correction feature. When any one of the 3 ports of a divider/combiner with the synchronizing feature is blocked, flow is possible between the other 2 ports. This "synchronizing" flow is called out in the performance chart and is pressure compensated.When the leading actuator comes to a stop, the other actuator can catch up at a rate determined by the "synchronizing" flow.When the actuators are stopped mid-stroke (port 3 blocked), oil can flow from the high pressure leg to the low pressure leg at a rate determined by the "synchronizing" flow.The "synchronizing" flow does not exist until one port is blocked.The "synchronizing" feature is most effective on applications where the actuators bottom out at at least one end of their strokes.|
|Why am I getting a higher inaccuracy than Sun claims?||We test every cartridge in 16 modes. High pressure, low pressure, high flow, low flow, divide, and combine.....both legs. What you are probably seeing is the error that occurs as the flow is ramping up to the minimum rated flow. Below the minimum rated flow the valve does not see enough flow to operate correctly.|
|Why does Sun use 2 slip orifices?||The divider/combiner is an FSDH XAN. Input flow is 15 gpm (57 L/min.). This example depicts orifices that slip about 3 gpm (12 L/min.) at 3000 psi (210 bar) pressure differential between legs. The slip conditions between the 2 examples are the same...please be assured of this. Each orifice on the right is twice the area of the orifice on the left.The pressure drop through the left example is 200 psi (14 bar), the drop through the right example is 130 psi (9 bar).|
|How big do my slip orifices have to be?||With a typical steered axle application the outside wheels go 15% to 20% farther than the inside wheels. As to how big your slip orifices need to be, there is no correct answer and you are the one that needs to make the compromise. If they are too big you will not have the traction you need at low speeds and if they are too small you will not be able to turn at higher speeds.|