旁路/节流, 优先调节单元
此旁通/限流调节单元外接节流孔将建立起旁通/节流流量控制。输入流量（口3）直接以优先或控制流量流出口2。当优先流量得到满足，多余的流量会从口4旁通流出。外接节流孔的流出端口与口1接通。此类阀的设计使油路优先级的压力和流量都得到控制，从而不受旁通油路压力影响。此类阀在中位关闭或者开启系统中都工作良好。当加入其他需要主机液压系统驱动的后配套系统时，使用此类阀可避免再添加额外的泵。
- 在满足优先流量之前，无法使用旁路流量。
- 可以在口1加入先导级电磁阀以实现优先流量打开或关闭。
- 口4的旁路压力可以高于控制口2的压力。
- 配置EPDM密封圈的阀适用于磷酸酯油，暴露在石油基液压油或润滑油中将会损坏EPDM密封圈。
- 利用Sun浮动结构减少由于过量安装扭矩或插孔/插装阀加工误差带来的内部零件粘结的可能性。
| 插孔 | T-34A |
| 系列 | 4 |
| 通流能力 | 120 gpm480 L/min. |
| 最大操作压力 | 5000 psi350 bar |
| 阀头部安装六角尺寸 | 1 5/8 in.41,3 mm |
| 阀安装扭矩 | 350 - 375 lbf ft474 - 508 Nm |
| 型号重量 | 3.30 lb1,50 kg |
| Seal kit - Cartridge | Buna: 990034007 |
| Seal kit - Cartridge | EPDM: 990034014 |
| Seal kit - Cartridge | Polyurethane: 990034002 |
| Seal kit - Cartridge | Viton: 990034006 |
There are exactly 250 Sun drops in a cubic inch or 15 in a cc.
The valve was developed originally to power demolition hammers. The hammers are aftermarket accessories that are mounted on a large variety of excavators. The "hammer" circuit provides a method of tapping into the existing hydraulic system of the excavator, turning the tool on and off, controlling flow, and limiting pressure.
Every manufacturer of hammers has very specific needs as far as flow and pressure and there is a large disparity of hydraulic systems in the excavators. For this reason, Sun has never had a catalog package for this circuit.
Sun does not and cannot provide technical support for "hammer valve" installations.
The LH*A family of valves has been optimized to be used in a package to provide a power source for hydraulic tools. We can quantify the performance of the valve in static conditions but we cannot tell you how it will do in your application.
For instance: You want to use the valve as a compensator for a load-sense power steering package. When you are steering the machine and raising an implement, the valve is in a bypass mode (throttling on the bypass side). When the implement actuator bottoms out, pressure jumps to maximum and now the valve needs to change to the restrictive mode. Since the LH*A is balanced against pressure on the bypass side the only thing moving the spool is its own spring. The time this takes is dependent on where the spool was to begin with and where it has to go.
During this transition the steering will see the pressure differential across it suddenly change from about 150 psi (10 bar) to a system pressure of say 3000 psi (200 bar) and suddenly back down to about 150 psi (10 bar). When this scenario was described to me it was termed the broken thumb syndrome.
Sun does not and cannot provide technical support for this type of application. The valve has been successfully used in similar applications. What is necessary to make it work is up to whoever is doing the application.