The Densistat D56Hybrid is suitable for indoor and outdoor use. It incorporates an analog gauge for relative pressure, referenced to 20 °C. The measured values are also provided as a data output signal. Microswitches inside the device respond reliably to any decreases in the density and pressure of the SF6 insulating gas. The pressure connection is either straight or angled (several options are available).
Key Features
Design
The D56Hybrid consists of the following principal components:
The cover with cable gland and the connecting cable with connectors form a single unit that is easy to dismantle with a screwdriver. The device can be supplied with a concentric pressure connection or various angled connections.
Operating principle
The Densistat D56 / D56i0 monitors gas density by way of a reference chamber filled with SF6 gas. The gas and reference chambers are separated by a metal bellows. A pressure difference corresponds to a density difference between the two chambers and deflects the metal bellows. The movement of the bellows is transmitted by a switch rod. A switching plate activates the microswitches whose purpose is to indicate a pressure drop.
The operating points for triggering the signal can be set at the factory according to the customer’s requirements by way of lockable screws (plungers). Up to four microswitches with changeover contacts can be installed in the housing. The microswitches are installed on a circuit board together with a multipole terminal block within the housing.The connecting cable is connected to the terminal block and exits the device through a cable gland.
The analog pressure gauge shows the relative pressure of the SF6 gas, referenced to 20 °C in the gas chamber. A change in gas density attributable to a leak is indicated by deflection of the needle. The colors and transitions on the dial can be specified by the customer and calibrated to the relevant values.
The arrangement of the measuring mechanism and the use of vibration-resistant microswitches rule out any shock-induced chattering at the switching contacts. In order to prevent condensation, the unit is equipped with a Gore-Tex® equalizing membrane.
| Indicator | Analog indicator Ø 55 mm |
| Connector | Phoenix Combicon or PTR terminal clamp |
| Cable gland | M25 x 1.5 EMC |
| Cable gland | M16 x 1.5 |
| Microswitches | 3 (max. 2.5 mm² IAW IEC 60947) |
| Protection | IP 67 / IP X5 IAW IEC 60529 |
| Vibration stability | > 4 g (20 … 80 Hz), 0.05 bar from switching point |
| Pressure range | 0 … 10 bar rel. / 0 … 145 psi rel. |
| Hysteresis | < 0.1 bar / 1.5 psi (typ.) |
| Indicator tolerance at 20 °C | ± 0.1 bar / 1.5 psi |
| Switching accuracy | ± 0.08 bar / 1.2 psi |
| Response threshold | ± 0.05 bar / 0.7 psi |
| Reference chamber leakage rate | < 0.005 bar/year (5 * 10-9 mbar * l * s-1) |
| Electric strength | 2 kV (50/60 Hz) to ground |
| Rated surge voltage | 5 kV (1.2/50 μs) to ground IAW IEC 61000-4-5 |
| Electric switch rating, Resistive load (inductive load) |
AC 250 V, 10 (2) A DC 250 V, 0.2 (0.2) A DC 220 V, 0.25 (0.2) A DC 125 V, 0.4 (0.25) A DC 110 V, 0.5 (0.3) A DC 60 V, 1.5 (0.4) A DC 48 V, 1.9 (0.7) A DC 24 V, 3.0 (2) A |
| Operating temperature | –40 … +70 °C / –40 … +158 °F |
| Storage temperature | –60 … +80 °C / –76 … +176 °F |
| Weight | 630 g |
| Material pressure connection | AISi1MgMn, anodized |
| Material housing and connection box | AISi12, powder coated RAL 9006 |
| Material reference gas bellows system | Stainless steel 1.4541 (bellows) / 1.4301 (bellows housing) |
| Material indicator window | Plexiglas molding compound 8N |
| Material type plate, resistant to UV, ozone, climate, chemicals, and solvents | 3M Scotchcal foil 3690 |
