This range of equipment has been designed to provide a modular range of FLP relays and FLP relays with self-contained power supplies for control and monitoring applications in coal mines.  This range of equipment is fully compatible with the Davis Derby 12DC, 18DC and 15AC power supplies.

The range consists of three basic types:

• FLP/IS Relay Transformer Unit type 25816/RR
• FLP Dual Relay type 25817
• FLP/IS Dual Relay type 25818 and 25818/RR

The range of equipment is designed to provide compact, reliable and extremely light weight units meeting the requirements of BS5501 parts 1, 5 and 7 (EExdi I).  The design of the power supply incorporated in the Relay Transformer Unit type 25816 also complies with BS6182 part 2.

Construction

The enclosure construction and cable entry facilities of this range of equipment is similar in specification to the Davis Derby range of I.S power supplies.

Types Available

FLP/IS Relay Transformer Unit type 25816/RR

This unit is equipped with an intrinsically safe transformer providing two segregated 15 volt as outputs which are available for external use.  Versions are available suitable for operation from a 120V or 240V 50/60 Hz mains supply.

A relay is also provided which has two sets of segregated single pole changeover contacts.  One set of contacts is wired to the i-s. chamber and the second set is wired to the FLP terminal block.  The relay contact which is wired to the FLP terminal block is normally light duty paladium rated at 250V, 1A, IOOVA maximum. Alternatively, elkonite contacts rated at up to 250V 5A, 1OOVA maximum may be specified when ordering the unit.

The relay which is energized from one of the 15V supplies, is designed to fail safe in the event of a short circuit in the cable to the remote initiating contacts.  This is achieved by connecting a diode in series with the initiating contacts.

A power on indicator is also provided which may be viewed through a window in the FLP front cover.

FLP Dual Relay Unit type 25817

This unit is equipped with two relays which are energized from a non - i.s. supply of 120-240V 50/60Hz. Relay coils which have a lower operating voltage can be fitted to special order.

Initiating contacts used to switch the energizing supply to the relay coils must in this instance be flameproof.

Each relay has two sets of segregated single pole change over contacts.  One set of relay contacts is wired to the i.s. chamber and the second set is wired to the FLP terminal block. As in the case of unit type 25816, the contacts wired to the FLP terminals are normally light duty paladium. Heavy duty elkonite may be specified when ordering.

FLP/IS Dual Relay type 25818 and 25818/RR

This unit is equipped with two relays which are energized from an external 15V - 18V intrinsically safe supply. In the case of unit type 25818/RR the relays are designed to fail safe in the event of a short circuit cable to the remote Initiating contacts.  This is achieved by connecting a diode in series with the initiating contacts.

FLP relay unit type 25818 is designed to be supplied from an ac or dc intrinsically safe supply. This unit is fully compatible with the Davis Derby 'MineWATCH', PMCU 1 and PMCU 2 outstations.

Alternative relay coils can be fitted to special order, one such alternative is suitable for operation from an intrinsically safe input of up to 18V ac or dc.

Each relay has two sets of single pole changeover contacts.  One set of contacts is wired to the i.s chamber and the second set is wired to the FLP terminal block.  As in the case of Relay Transformer Unit type 25816, the relay contacts wired to the FLP terminals are normal light duty paladium.