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2. Thus the period taken to deal with "Three Pots" in succession
is approximately six minutes and the actual period is easily
adjustable by means of a clock or Timing glass to the accurate six
minutes required by the Regulations without appreciable loss of
time to the operators .
3. With the "Two Pots System" the time taken to sieve the cockles and
replenish the baskets of two pots is approximately four minutes.
Thus a wait of two minutes is necessary after two pots have been
sieved to maintain the six minutes routine
During busy periods there is a tendency to reduce this waiting
period. This is noticeable even when the Port Health Inspector
is present.
4. The "Three Pots System" as at present installed always includes a
Reducing Valve by means of which the steam is admitted to the
cooking pots at a pre-arranged and constant pressure. This makes
for steady and comparatively slow cooking.
5. With the "Two Pots System", with no Reducing Valve, steam is admitted
to the cooking pots at boiler pressure. Where this pressure is high
the result- is a very sudden charging of the pot with steam} and
violent cooking.
It is true the operator usually controls the admission of steam
by manipulation of the hand valve to each pot, but this is a very
haphazard method and results are most erratic.
Pressure at the Reducing Valve.
The correct setting of the Reducing Valve is essential to the success
of cooking cockles by steam. There is bound "Co be some difference of opinion
between the various members of the Industry as to the ideal pressure at which
to work, and it is not the duty of the Port Health Inspector to dictate the
actual pressure to be used.
The following notes will, it is hoped, be of some value s-
1. It will be appreciated that no matter what the pressure at the
Reducing Valve, the pressure of the steam in the cooking pot is
constant at just above atmospheric pressure, since the vent; in the
cooking pot is always open, and no pressure can possibly build up
inside.
2. Though the pressure (and temperature) of the steam in the cooking
pot is constant, the higher the pressure at the reducing valve, the
greater the quantity of steam which is admitted to the pot. Consequently
the contents are more quickly and thoroughly heated through,
resulting in slightly quicker cooking.
3. The higher the pressure at the reducing valve, the more quickly will
a pot "blow"; i.e. become completely charged with steam. It is when
this has happened that cooking starts.
Since the system of installation in every establishment with a "Three
Pots System" comprises a §" diameter steam pipe from the boiler, which
branches after the Reducing Valve into three separate diameter pipes for
the separate cooking pots$ it is not surprising to find that the effective
steam pressure drops as one, two and then three pots are turned on.
The ratio of fall in the steam pressure varies a little from one
apparatus to the next, but this should not make any material difference once
an apparatus is adjusted to give satisfactory resultso
Referring again to the second part of the attached table, it will be
seen that pressures at which the Reducing Valve is set have varied from 151bs.
per square inch at rest (lowest) to 50 lbs. per square inch at rest (highest).
Example No. 11. 15 lbs. pressure at rest. This was staged as an
experiment only.
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