Fixed orifice, flow fuse valve

Capacity: 50 gpm200 L/min. | Cavity: T-18A
FQIA : Fixed orifice, flow fuse valve
Technical Features [ + ]

Flow fuse cartridges are used to maintain the position of a hydraulic actuator in the event of a hose or line break. The valve allows flow to and from the actuator but closes instantly if flow from the actuator exceeds the setting of the valve. NOTE: Because the valve responds so rapidly, it is sensitive to any transient flow above the valve setting.

  • Customer must specify a flow rating. Factory set flow ratings are within +/- 10% of the requested setting.
  • Valve closes when flow from port 1 to port 2 exceeds the setting of the valve. Valve resets when pressures at port 1 and port 2 are equal.
  • Flow setting should be at least 25% above maximum normal system flow. Customer must specify flow when ordering valve.
  • These are spool type valves, therefore there is leakage. Some actuator drift may occur.
  • 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.
Technical Data [ + ]
Note: Data may vary by configuration. See CONFIGURATION section.
Cavity T-18A
Series 4
Capacity 50 gpm200 L/min.
Maximum Operating Pressure 5000 psi350 bar
Maximum Valve Leakage at 110 SUS (24 cSt) 5 in³/min.@1000 psi80 cc/min.@70 bar
Valve Hex Size 1 5/8 in.41,3 mm
Valve Installation Torque 350 - 375 lbf ft474 - 508 Nm
Model Weight 2.90 lb1,30 kg
Seal kit - Cartridge Buna: 990018007
Seal kit - Cartridge Polyurethane: 990018002
Seal kit - Cartridge Viton: 990018006
Performance Curves [ + ]
FAQs [ + ]

NO! Flow fuses are meant to prevent the uncontrolled movement of an actuator in case of hose failure. To avoid false tripping they must be set above the typical system flow, usually 50% above. On a 4 gpm (15 L/min.) circuit the flow fuse may need to be set at 6 gpm (23 L/min.) to avoid false tripping. Hoses do not normally fail totally, they spring a leak. If the hose springs a 5.5 gpm (21 L/min.) leak the flow fuse will not trip. 5.5 gpm (21 L/min.) of hydraulic fluid will feed a fire that would heat a small town in Ohio (Denmark) in January!

It is very, very difficult to predict the transient flows in a system. We say at least 25% above maximum normal system flow and should say 50%. Don’t back yourself into a corner by sizing a flow fuse at the top end of its range unless you can test it. If you have an FQCA in a 4 gpm (15 L/min.) circuit, set at 6 gpm (23 L/min.) and it false trips, you are out of luck. Select an FQEA and leave yourself some room for tuning.

What's wrong is that every time you start to lower your load, you get a flow transient that exceeds the setting of the flow fuse and trips it. Sun's flow fuses are very consistent and very fast.

There are exactly 250 Sun drops in a cubic inch or 15 in a cc.

NO! Flow fuses are meant to prevent the uncontrolled movement of an actuator in case of hose failure.

Only external seals are serviceable.  Sun offers replacement seal kits for all cartridge models. The applicable kit part number can be found in the product page's Technical Data table or by using our Cartridge Seal Kit search function located under Accessories. Please note: Converting the external seals from one material to another does not ensure fluid compatibility with that material due to the existence of internal seals within the cartridge.
Additional Resources [ + ]