BL OJEU- UK SBS RE150260NERC- Thermistor Cables

THERMISTOR CABLES We require two cables, one 1400 m in length, the other 1500 m in length. 1. The cable will have a minimum of 26, multi-stranded copper conductors, each with a minimum cross sectional area 0.14 mm2. 2.

The minimum voltage rating for the insulation will be 24 V. 3. The minimum current rating will be 100 mA. 4.

The cable will have an aramid, central strain member. 5. The cable will have an outer jacket of polyurethane, with a minimum thickness of 1.4 mm. 6.

The cable will be able to support all but 100 m of its own length in water (ie 1300 and 1400 m), 100 m of its own length in air, and a 100-kg ballast weight that will be suspended from the bottom end. 7. The cable will be supplied on a drum with the deep end on the outside of the reel. 8.

The stretch in the cable when deployed will be less than 1% of its unloaded length. 9. The cable will be able to withstand the hydrostatic pressure it is under when deployed.

At its deepest point, the pressure will be 130 bar for the 1400-m cable, and 140 bar for the 1500-m cable. The pressure decreases linearly from that the deepest point to sea level. 10.

The free-issued thermistors will be wired into the cables as in the attached diagram. 11. A polyurethane (or equivalent) potting compound will be used to form the termination that seals the cable after the thermistors have been inserted. 12.

The shape of the terminations will be axially smooth to assist in their passage through the ice borehole. 13. A polyurethane (or equivalent) potting compound will be used to form the termination at the deep end of the cable.

Description of the thermistor elements The thermistor elements as issued are installed in 3 mm diameter, 15 mm long, stainless steel tubes. The 50-mm long, tinned copper wires for the thermistors emerge from each end of the tube.

Requirements for the cable plus termination assembly 14. During deployment, the cable, under the load described in 6, is lowered over a 400-mm radius sheave wheel.

The terminations will be required to traverse the sheave wheel without damage. The radius of the inside of the bottom of the sheave’s ‘U’-shaped cross section is 17 mm. 15. To maximise the thermal lagging between thermistor and water, the thermistor will be located as near to the axis of the cable as practicable.