The isolator valve type SL is a releasable check valve for subplate mounting or threaded connection. It is used for the leakage-free blocking of one actuator port, also in case of longer standstill times.
The valve basically consists of a housing (1), a seat poppet (2), a compression spring (3), a control spool (4) as well as of an optional pre-opening as ball seat valve (5).
The seat valve can be flown through from A to B without external pilot pressure. In the opposite direction, the seat valve closes hydraulically tight.
Condition: pA > pB + cracking pressure (compression spring).
A sufficiently high pilot pressure at port X moves the control spool (4) in the direction of the ball seat valve (5) (version “A”) and pushes the seat poppet (2) out of its seat. This allows for a free flow in both directions (active keeping open).
In order to ensure that the seat valve actively opens, the pressure ratios on both sides of the control spool (4) are just as important as the area ratios at the control spool (4) or seat poppet (2).
This results in the versions with pre-opening “A” and without pre-opening “B” for type SL (small annulus area). A4 (9).
Version “A” (with pre-opening)
This valve is provided with an additional pre-opening. By pressurization at the X port, the control spool (4) is moved to the right. As a result, the ball (5) is pushed off the seat first and the seat poppet (2) afterwards.
Notes:
- Version “A”:
- The two-stage set-up with an increased control open ratio means even low pilot pressure can be unloaded securely.
- Avoidance of switching shocks due to dampened decompression of the pressure volume on the actuator side.
- Version “B”:
- In case of valves without pre-opening, the included pressure volume may be unloaded suddenly. Resulting switching shocks may lead to premature wear on installed components, as well as noise formation.
Type SL..PB.-4X/… (with pilot oil return, without pre-opening)
| 6 | Area A1 (seat poppet) |
| 7 | Area A2 (ball) |
| 8 | AreaA 3 (control spool) |
| 9 | Area A4 (control spool) |
Notice:
The modification of type SV to type SL is possible by exchange of plugs (10) and (11). One of the both plugs must always be installed.
| NG | Plug (10) |
Plug (11) |
| 10 | M3 | M6 |
| 20 | M4 | M6 |
| 30 | M4 | M6 |
Version “6U” (with built-on directional valve)
At direct operated, pilot operated check valves type SL with built-on directional valve, the control spool (4) may be controlled directly via the directional valve to open the seat poppet (2) against the system pressure, i.e. the blocking direction.
Notice:
When ordering the directional valve, please observe the different position of port A at versions “P” and “G” (porting pattern rotated by 180° at version “G”, see “Dimensions”).
Type SL..PB.-4X/6U… (with pilot oil return, without pre-opening)
| 6 | Area A1 (seat poppet) |
| 8 | AreaA 3 (control spool) |
| 9 | Area A4 (control spool) |
