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(full power). When

  the

  furnace

  and

  furnace transformer

  are on

the signal light shows red.

After the selected temperature, which may

 be

 any value between

100 and   1000°C,  has  been reached,   the   furnace transformer will

be automatically switched into star-connection (one-third full

power) and the temperature kept constant

at

  the selected tempera-

ture (±20°C)  by automatic on-off control   of  the star contactor.

Should   the   temperature rise much above   the   selected value  for

any reason, e.g. sticking

 of the

 star

 or of the

  delta contactor,

 the

furnace will  be  automatically disconnected   by the  line contactor

and the alarm given. The same will happen should the temperature

controller (governor) fail, perhaps owing to   the pyrometer thermo-

couple burning

  out. The

 alarm bell

 can be

 switched

 off by

  hand,

but the orange emergency lamp will keep on  burning as long as  the

pointer of the temperature controller remains  in the alarm position.

Normal closing down of the plant  at the end  of  the working  day

is initiated automatically by the time switch.

Hand Operation

For  hand operation,   the   selector switch   is

brought into

  the

  hand position.

  A

  hand-operated pilot switch

enables on-load switching of  the furnace transformer into delta  or

star connection a t will, whereas another hand-operated pilot switch

serves

 for

  on-off control. When

 on

  hand control,

  the

  temperature

governor will act as an  indicating pyrometer only,   but the excess

temperature

  and

  thermocouple failure alarms

  are

 still available

 as

above. However  no automatic disconnection  of  the furnaces takes

place

 in

  hand operation.

Temperature Recording

A synchronous motor-driven chopper-bar-type two-colour

temperature recorder

  and

  direct-reading pyrometer

  is

  also

provided

 for

 the two furnaces. The range

 of

 the instrument

 is

0-1000° C,

  the

  chart feed being 20 mm /hour.

  A

  special

recording panel

  is

 provided between

  the two

 control boards

for this instrument.

Operating E xperience

The furnaces were commissioned

  in

  December, 1954,

 and

have been

  in

  commercial operation ever since. There have

been

 no

 initial troubles with the electrical pl ant.

Some minor mechanical difficulty

  has

  occurred—e.g.

cracking

  of the

  refractory liner, growth

  of the

  cast-iron

melting-pot,

  and the

 lining

  of the

  latter proving

  not

  quite

satisfactory;

  but it is

  understood that these have been

 or are

being overcome.

The heat insulation

 of the

 furnaces

  has

  proved very satis-

factory.

  The

  outside temperature

  of the

  furnace shell does

no t exceed 80-84° C with

  the

 melting-pot

  at

  9 ° C.   This

compares favourably with

  the old

  oil-fired furnaces

  of the

same establishment, which exhibit outside furnace

  tem-

peratures

  of

  about 180°C under similar melting-pot

temperatures.

  cknowledgments

The writer wishes

  to

  thank

  Mr. K.

  Pallo, Governing

Director,

  Die

 Castings

  Ltd. of

  Lower Hutt,

  New

 Zealand,

for the opportunity

 to

 carry

 out

 this work, his assistance over

it,

 and

 his permission

 to

 publish this letter.

  nnual Dinner  o the dmiralty Electrical Engineering Officers

On the 20th March, 1956,   the Admiralty Electrical Engineering

Officers held their annual dinner in Bath, under the chairman-

ship

 of Sir

 Hamish

  D.

  MacLaren,

  a

 Vice-President

  of The

Institution and Director

 of

 Electrical Engineering, A dmiralty.

The assembled company

 of

 225 included

  the

 Vice-Controller

of the Navy, Rear-Admiral

 G. B.

 Sayer,

 the

 heads

 of

 several

Admiralty departments, some

  60

 guests from

  the

  electrical

manufacturing

  and the

  shipbuilding industries,

 and

 members

of the civilian and naval staff

 of

 the Department

 of

 Electrical

Engineering, including the Royal Dockyards.

The Institution was represented,

 in

 addition

 to

 Sir Hamish,

by

 Mr. T. G.

 Dash, Chairman

 of

  the Western Centre. Rear-

Admiral  P.  W . Snyder  (U.S.   Navy Shipbuilding Representative

Europe)

  and the

  Assistant Naval Attache

  to the

  American

Embassy, Cmdr.

 D .

 Furlong, represented

  the

 U.S. Navy.

The principal speaker

 was

 Major

  C. A. J.

  Martin

  and in

his speech

  he

  commended

  the

 Admiralty e lectrical officers

for

  the

 skill

 and

  ability with which they tackled

 a

  very wide

field of technical problems—made very much more difficult

by

  the

 extreme conditions

  in

  which much naval equipment

had sometimes

 to

 operate.

In

  his

 reply

  Sir

  Hamish MacLaren referred

  to his

  recent

visit

  to the

  United States

  and

  particularly emphasized

  the

lead the Americans had taken by their rapid development an d

J U N E   1956

A group photographed

  at the

 dinner

Left to right F. N.

  SMITH;

  Rear-Admiral G. B.

  SAYER;

  Sir

  HAMISH

MACLAREN,  Chartered Electrical Engineer; Rear-Admiral P . W.   SNYDER,

U.S.N.; Major C. A. J.  MARTIN,  Chartered Electrical Engineer;   W. M.

COUCH,  Chartered Electrical Engineer.

quantity production

  of

  cables using silicone-compounded

insulants,

 an

 example which

 he

 hoped would

 be

 followed

 by

cable makers

 in

 this country.

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