MIL-J-26149E
3 8 1 Pump. The pump shall be of the hand-operated, piston type. The ratio between the jack rain and pump piston shall be such as to require a force not greater than 100 pounds (445 N) at the end of a pump handle extension to raise a load equivalent to the jack capacity. The pump handle extension shall be at least 27 inches (686 mm) long and shall be provided with a suitable
grasp (knurled) surface. For jacks of less than 10 tons (9070KG) capacity a
shorter handle may be provided ie 18" (0.456M) or 20" (0.51M). Provisions
*shall be made to stow the pump handle on the jack. The pump inlet shall be provided with a screen of approximately 50-mesh, 0 007-inch (0.18 mm) diameter brass wire, The internal leakage of the pump shall not exceed 5.0 cc per hour.
* 3 8.2 Safety Bypass valve. The jack shall be equipped with a bypass valve adjusted and set to 105 to 110 percent of the rated capacity of the jack.
This valve shall be located between the pump check valve and the jack ram to prevent overload and shall vent into the reservoir.
3.8.3 Safety device. The tripod jack ram(s) shall be provided with a mechanical safety device capable of supporting the rated load with the
hydraulic pressure removed. The safety device shall prevent dropping the load
3.8.4 R eservoir.
The hydraulic fluid reservoir shall have a capacity
sufficient to fully extend the jack ram plus a 10-percent minimum reserve. An air relief valve and filler plug in accordance with Drawing 1128AS121 shall be
provided on top of the reservoir (not shown in Figure 1).
* 3.8.4.1 Reservoir Dumping or safety valve. The dumping or safety valve (not shown in Figure No. 1) shall be located on or near the top of the reservoir. This valve shall automatically vent excess air from the reservoir
when this air is being replaced by hydraulic fluid. This valve shall be sized to accommodate the maximum flow of hydraulic fluid that may pass through the
release valve. Also when relatively small-sized jacks are tipped or
overturned this valve may not leak hydraulic fluid.
* 3.8.4.2 Reservoir overflow vent valve. Those hydraulic jack systems that include a connection for an external pumping source connector shall also include an overflow vent valve located at the top of the reservoir (not shown in Figure No. 1). This vent shall relieve excess fluid that may be inadvertently transferred from the external pumping source. The vent valve shall open at about 100 psig pressure to prevent any damage to the reservoir by relieving the pressure under the most extreme operating conditions (full opening the release valve while under maximum load of the jack). In order to prevent injury to the operating personnel the overflow from this valve shall be directed downward.
3.8.5 Ram cylinder. The internal surface of the ram cylinder shall be chrome plated.
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