Prep low pressure D-FORCE pumps

Liquid chromatography pumps - Prep low pressure D-FORCE pumps

D-FORCE series comprises single-piston, double-action middle pressure pumps specially designed for heavy duty conditions of flash and plant preparative chromatography applications. They are less sensitive to solid impurities in the mobile phase that other pumps with only one large input ball valve. The unique design provides for almost pulseless flow even though the pumps have only one piston head. The flowrate is practically independent of the outside pressure.

D-FORCE pumps are corrosion resistant since the wetted parts are made only of HDPE (high density polyethylene), PEEK (polyetheretherketone), PTFE (polytetrafluoroethylene) and AISI 316 stainless steel. Pumping heads consist of a polished stainless steel cylinder with pistons inside. The piston front part is equipped with a ruff-shaped seal made of high density polyethylene. The cross-section of the piston rod is one- half that of the cylinder and the piston is sealed on the back side of the cylinder with the well-tried conical seal known from the Labio Express pump line.

A robust check valve with a large ball inside is on the bottom front part of the cylinder. The output valve is provided by the piston ruff. The function is apparent from the figure. During the first stage of piston stroke (backward movement) the liquid is sucked through the input valve to the front part of the head cylinder (A). At the same time liquid is expelled from the cylinder back space (B) to the system. 

In the second stage (piston forward movement) liquid in the front cylinder space is forced to the back as the input valve is closed. An the same time the back space between the cylinder and the piston rod expands but the amount of liquid transported from that part is two times the back side volume (due to the ratio of the two cross-sections). As a result the pump displaces the same amount of liquid as during stage one.

In D-Force pumps the flowrate is controlled by changing the stroke frequency, i.e., by varying the motor speed. The mechanical part of the pump, which transforms the rotary motion to linear piston displacement is equipped with a cam and is similar to that employed in the Express series.

All D-Force pumps are supplied in a simple rectangular cabinet provided with a two-line display and a keyboard on the front panel.  The cabinet houses a motor, a gearbox, a cam mechanism, a pressure gauge and electronics. The flowrate, the time of action and the pressure limit are controlled from the keyboard; the actual flowrate and the pressure are monitored.

In the laboratory D-Force version the piston is actuated by a quality dc motor with optoelectronic speed control between 1:1 and 1:200. The industrial versions D-Force 4 and, primarily, D-Force 8 employ an asynchronous motor of up to 500 W power transmitted by means of a multiple V-belt. The speed of the asynchronous motor is controlled by a frequency converter between 1:1 and 1:20.