Firma:              Merck-Hitachi

Modell:                         L-6000 A

Kommentar:     Dokumente engl.

Functions

Operating Principle

Fig. 2.1 shows the mechanism of the L-6000A Pump.

Two plungers are moved by cams toward the pump head and are returned by springs. The reciprocal movement of the plungers feeds the liquid. To drive the cams, a stepping motor is used. The discharge rate is controlled by changing the pulse frequency supplied to it.

Fig. 2.1 Pump Mechnism

Liquid Supply Method

The time during which the sample moves in the column (retention time) is used for identification of the separated component. A precision of ± 1 % or better is required for the flow stability of the liquid supply which determines the reproducibility of the retention time. The pump must provide a constant flow rate regardless of the eluent compression ratio or the pump delivery pressure. In case of a reciprocal pump, the flow stops when the piston is at a suction status. The pulsation generated appears as noise at the detector output and creates an undulatory (sometimes almost sinuous) baseline at the recorder or integrator.

The L-6000A eliminates pulsation by a fully automatic function (liquid supply monitor-ing function) explained below.

Automatic Pulsation Eliminating Function (Liquid Supply Monitoring)

Under a high pressure of 400 bars used in HPLC, the liquid is compressed. The compression ratio differs depending on the liquid. For both reasons, the discharge pressure changes, or the time required for compression or the time during which the 1st cylinder delivery is stopped varies depending on eluents.

While the 1st cylinder is compressing the liquid (before the discharge valve opens) there is a short drop of discharge pressure. This pressure variation is detected and, at the next cam rotation, the rotation is increased at the right moment to twice the steady rotation rate (within a predetermined range), thereby compensating the re-duced pressure. This function, to stabilize the liquid flow rate by adjusting the double speed range of the cam, is referred to as an automatic pulsation eliminating function.

Its mechanism is shown in Fig. 2.2.

Fig.2.2 Liquid supply mechanism of the L-6000A Pump

SPECIFICATIONS

(1)      Liquid Supply System Dual plunger reciprocating pump

(2)      Maximum Discharge Pressure 400 bar (1 to 9990 m l/min)

(3)      Range of Discharge Flow Rate

          1 to 999 m l/min in 1 m l/min steps, 1000 to 9990 m l/min in 10 m l/min steps

(4)      Flow Rate Setting System

          Digital switch (in 1 or 10 m l/min steps depending on range)

(5)      Pressure Indicating System LCD in 1 bar steps

(6)      MAX Pressure Limiter

          0 to 420 bar in 1 bar steps by 3 digit switch. 420 bar is set when an attempt

          is made to set 421 to 999 bar.

(7)      MIN Pressure Limiter

          0 to 420 bar in 1 bar steps by 3 digit switch. 420 bar is set when an attempt is          made to set 421 to 999 bar.

(8)      Discharge of 1st Cylinder 100 p~./stroke

(9)      Accuracy of Flow Rate Setting

          For distilled water at a constant room temperature of 20°C:

          ±2 m l/min (10 to 100 m l/min, 5 to 400 bar)

          ±2 % (101 to 5000 m l/min, 5 to 400 bar)

          ±2 % (5010 to 9990 m l/min, 5 to 20 bar)

          +2 % to -0.1 x P % where P denotes discharge pressure in bar (5010 to 9990          m l/min, 21 to 400 bar)

(10)    Flow Rate Stability

          For distilled water at a constant room temperature of 20°C:

          ±0.3 % (10 to 5000 m l/min, 5 to 400 bar)

(11)    Correction for Solvent Compression

          Automatic pulsation eliminating function

(12)    Pressure Indication Accuracy ±5 %

(13)    Constant Pressure Liquid Supply 20 to 400 bar

(14)    Materials of Parts in Contact with Liquid

          SUS 316, ruby, sapphire, carbon-impregnated PTFE

(15)    Dimensions

          260 (W) x 400 (D) x 150 (H) mm excluding standouts

(16)    Weight 12 kg

(17)    Power Source

          100 to 115 or 220 to 240 V AC, 50/60 Hz

          Switch selectable at rear panel

(18)    Power Consumption 8OVA

(19)    Ambient Temperature 10 to 35°C

(20)    Ambient Humidity 45 to 85 %

(21)    Control Mode Switch (front panel) For high pressure gradient

(22)    Output Signals

          (a)          Pressure Signal (analog signal) o 10 mV/bar

                        (for controller connection, PRESSURE terminal on rear panel)

          (b)          Pressure Limiter Signal Limit out, relay contact

(23)    Input Signals

          (a)          External Start Signal

                        PUMP START IN 1, PUMP START IN 2

          (b)          External Stop Signal

                        PUMP STOP IN 1, PUMP STOP IN 2

          (c)           I/O BUS (option)