Model 30000-S DHPU Manual
Rev. 0
JRK
17SEP12
Page 14
Casing Mode
The power unit should be in casing mode when a casing tong is to be operated. Casing mode
allows both pump sections to contribute flow to the hydraulic circuit, so a higher flow at a
lower pressure is available. Once the load on the system increases past a factory preset
point, the rear section of the pump is shifted out of the circuit and circulates fluid internally
(tubing circuit mode). Therefore, less flow leaves the pump, but the maximum pressure that
can be achieved is higher. This high/low feature allows for faster use of the casing tong with
light loads while still providing high pressures for making/breaking of the connection.
Idle Mode
The power unit is equipped with a hydro-throttle as shown in the figure below. When the
system pressure exceeds the set point, the internal piston will extend thereby increasing the
motor speed. The cylinder is pushed back by the spring when the pressure drops back down
below the set point putting the engine into an idle mode to lower the motor's fuel
consumption. The set pressure is typically set around 500 to 800 PSI. This setting should be
higher than the back pressure experienced through the interconnect hoses and tong valve in
neutral. The setting can be adjusted if the back pressure is higher or lower. Refer to the
hydro-throttle cut sheet in the engine section.
Figure 7: Hydro-Throttle
Start Up
Ensure that the installation section has been followed and that the tong control valve handle
is in neutral. Review the included engine operation and Murphy panel manuals also prior to
operation. Make sure that the fan belt break trip lever and the Sentinel are reset. The
function of the Sentinel is described in the safety features section. To reset the valve, turn
the trip lever to clockwise. Refer to the previous picture for the location of these
components.
