People that work in process control call (and draw in plant blueprints)
thermometers as TI, TR, TIR and TRC (and TIRC).
TI is any kind of temperature indicator that gives a point (current)
indication of temperature; measurement could be based on different type of
devices from thermocouples to Hg thermometers. Usually a TI is placed right
in the action and the lecture is taken in the place of the action (e.g. at
the CCP).
TR are temperature recorders, and this could produce graphic records or be
eventually coupled to a data logger and/ or to a computer. TR could be in
remote positions, or positions not easily accessible, or positions that
require of a continued monitoring. Lecture of that kind of temperatures is
usually feasible from panels in the control room or from computer terminals.
TIR are indicators/ recorders of temperature. This means they give a point
lecture and produce a record (analogic or digital). This is the type of
equipment that could appear coupled to a manual retort.
TI, TR and TIR could have some additional functions like to make a ring bell
when the temperature is above or below certain value. The purpose is
obviously to assist in the manual control and avoid somebody should be
sitting by the thermometer looking all the time.
To make things a bit more complex in the physical word we have three
different "temperatures", dry bulb, wet bulb and radiation temperature. In
some type of processing (e.g. drying) we need indications of both the dry and
the wet bulb temperatures. This is not a scientific speculation without
practical interest. When we are putting a thermometer in a fresh fish, we are
actually measuring the "wet bulb" temperature, that according to the relative
humidity of the air around the fish, will be usually somewhat below the "dry
bulb" temperature of the surrounding air. The net result is that the fish
exposed to the air will star to dry, first of all in the surface, changing
the environment of the fish natural flora and allowing for instance the
development of contaminant flora. Ice not only keeps temperature low, it
keeps fish wet.
TRC are recorders/ controllers of temperature. This means the temperature is
recorded (analogically or digitally) and the signal of temperature is
utilized to control automatically the temperature in the case of deviation of
the desired value. This is the type of device that can be found for instance
in automatically controlled retorts, also in equipments like shrimp cookers.
TIRC, the same but point lecture is possible on the spot too. The big
difference between this type of equipment and the previous ones is that this
type of equipment, more than "thermometers" are "temperature controllers".
Whereas in all the cases the purpose of the measurement of temperature is to
control it, in the case of non-C "thermometers" the control should be
performed through an human operator.
In the industry blueprints thermometers usually appear as a circle inside
which appears the type, e.g. TIR and a code (place in the plant/ line, etc).
Of course there are drawing standards for them, and also standards of how a
TI should be (see for instance ASTM F2362-03
http://webstore.ansi.org/ansidocstore/product.asp?sku=ASTM+F2362-03).
Standards could vary somewhat from country to country. Good plants count with
a blueprint were all the measurement devices are properly identified and
located in the blueprint according with their actual position and purpose.
The code is important because any measurement device should be calibrated
periodically and therefore it should be possible to identify it properly in
the plant (and in the calibration logbook). Probably this is the key point of
all the discussion, thermometers should be calibrated, no matter the way they
are indicating, recording or storing data; they are always utilized to
control and/or monitoring.
Finally it is true that technical documents and even documents that refer to
regulations (or even in regulations) appear references to different type of
thermometers (and way of reading and/ or recording) and this is not always
clear. In new university curricula dealing with food (and fish) curricula
there is now a subject on measurement and control under industrial
conditions, however, this was not the case in the past.
The knowledge on different type of measurement and recording equipment (not
only for temperature) is becoming more and more important in the food and
fish industry, since very often essential parts of the process are automatic
(it means controlled automatically), for instance water chlorination today is
done automatically practically all around the world, and manual retorts for
canned food products are becoming a industrial museum item.
Kind regards.
Hector M. Lupin
Consultant
FAO of the UN
-----Original Message-----
From: owner-seafood@ucdavis.edu [mailto:owner-seafood@ucdavis.edu] On
Behalf Of Dr. R. Viswanathan
Sent: 27 July 2006 10:06
To: Vinod V
Cc: seafood@ucdavis.edu
Subject: Re: Indicating thermometer
It may be the thermometer with digital display that gives an
indication when the temperature reaches the set maximum level.
Also it may be the thermometer with digital display which facilitates
instant observation rather than looking at the dial, in the case of dial
thermometer / the scale in the stem type mercury or alcohol filled one.
Thu, 27 Jul 2006 Vinod V wrote :
>
>
>Dear List,
>
>In page 204 of the "Fish & Fisheries Hazards & Controls Guidance :
3rd edition, in the control strategy for hydrated batter mix control, under
the head - How will monitoring be done ? There are 5 options out of which the
5th option is, using an indicating thermometer.
>
>What is an indicating thermometer ? Aren't all the thermometers
indicating thermometers or are these any specific type of thermometers ?
>
>Please clarify.
>
>Regards
>
>Vinod
>INDIA
With regards,
Dr.R.Viswanathan,Ph.D.,
Professor,
Department of Food and Agricultural
Process Engineering,
Tamil Nadu Agricultural University,
Coimbatore -641 003.
Phone: 0422-5511272 / 5511282
Res: #12, Sowbhagya Nagar,
A - Block, Opp. to KMCH, Civil Aerodrome, P.O., Coimbatore -641 014.
Phone: 2629711
<http://adworks.rediff.com/cgi-bin/AdWorks/sigclick.cgi/www.rediff.com/signat
ure-home.htm/1507191490@Middle5?PARTNER=3>
This archive was generated by hypermail 2b29 : Thu Jul 27 2006 - 07:56:26 PDT