FNW TBM Bimetal Thermometers Instruction Manual
- June 13, 2024
- FNW
Table of Contents
INSTALLATION, OPERATION AND
MAINTENANCE INSTRUCTIONS
MODEL NUMBER
THERMOMETERS
BIMETAL THERMOMETERS,
LIQUID-IN-GLASS THERMOMETERS,
REMOTE READING THERMOMETERS
We reserve the right to modify or improve the designs or specifications of our products at any time without notice.
BIMETAL THERMOMETERS
NOTE:
If the thermowells are purchased separately from the thermometers, then a
suitable temperature transfer medium must be added to the well to properly
conduct the temperature to the thermometer bulb for all thermometers. A
mixture of graphite and oil, heat transfer paste, or even a light oil will
suffice.
BIMETAL THERMOMETERS (TBM, TNR)
FNW bimetal thermometers are direct sensing instruments that are hermetically
sealed and thus completely waterproof and dust proof.
For accurate temperature readings, the stem should be immersed past the groove
on the lower portion of the stem. All bimetallic thermometers are of 304
stainless steel construction to protect against corrosive conditions. An
external adjustment screw is conveniently located on the bottom of each case
for easy field recalibration of thermometers, which may have shifted out of
accuracy.
INSTALLATION OF BIMETAL THERMOMETERS
Location Vibration and extreme ambient temperatures can affect the dial
reading. These areas should be avoided as much as possible. Vibration effects
can be minimized by the use of a dampening liquid such as glycerin or
silicone. If vibration is extreme, then a remote reading filled thermometer
should be considered.
Mounting
A suitable thread sealant, such as pipe dope or PTFE tape, is required for
NPT. Never use any part of the thermometer other than the hex nut that is on
the stem of the thermometer just above the NPT threads for installation.
Always tighten with a wrench on the hex nut. Failure to do so will severely
damage the thermometer. Typically, bimetal thermometers are connected to the
process through a thermowell. This allows for the removal and testing,
calibration or replacement of the instrument without affecting the process
operations. The selection of thermowell material and stem lengths is critical
in order to properly monitor the temperature of the process.
OPERATION AND MAINTENANCE OF BIMETAL THERMOMETERS
Disassembly & Assembly/Spare Parts
It is not recommended to disassemble the thermometer for any reason. If the
thermometer is not functioning properly or if the lens is broken, the
thermometer should be replaced. Please contact FNW for replacement.
Inspection Frequency
These thermometers are ruggedly constructed to give a reliable process
temperature reading. The frequency of inspection is dependent on how critical
the reading is at that point in the process. The inspection frequency can
range from monthly to annual bases.
Over Range Protection
Over range protection allows the thermometer to function within its designed
parameters even when the media temperature may intermittently exceed the
thermometer range. The over range protection is 50% for ranges up to 500°F
(260°C) and 10% above ranges of 500°F (260°C).
Recalibration
A master thermometer with a high degree of accuracy should be used for
calibration. Immerse the bimetal thermometer alongside the master thermometer
into an agitated liquid for at least three minutes and compare temperature
readout. Note that both thermometers must be immersed at the same level. An
external adjustment screw is conveniently located on the bottom of the case
for easy field calibration. FNW can recalibrate and provide test
certification. Please contact us for more details.
Storage
Store in a dry area at ambient temperatures not exceeding the indicator range.
For example, if the indicator range is 0°C to 300°C, then the storage
temperature should not exceed 300°C.
Head Rotation
NOTE:
The bimetal thermometer head can be rotated as illustrated only when in back
connection position. Never rotate the thermometer head when it is in the
angled position.
To rotate thermometer head up to 360°, make certain thermometer is in back connected position. Loosen two screws on both sides (A) until harness revolves freely.
Now hold thermometer head and adjustable harness and rotate head to desired position. Retighten screws (A).
Angle Positioning
To tilt thermometer head up to a 90° angle or straighten it, loosen single screw (B) by 1/2 turn only.
Tilt to desired angle or straighten. Retighten screw (B).
LIQUID-IN-GLASS THERMOMETERS
LIQUID-IN-GLASS THERMOMETERS (TAG, TAS, TIM, TSW)
Liquid-in-glass thermometers have a glass tube in front of a metal scale. It
extends into a metal chamber and has a glass bulb attached.
This tube is completely sealed, and the bulb contains a predetermined amount
of liquid which, on expanding and contracting due to temperature changes, will
indicate the temperature for a given temperature range.
INSTALLATION OF LIQUID-IN-GLASS THERMOMETERS
NOTE:
Make sure that while connecting the thermometer to the process, the sensitive
portion of its stem (the last 2-1/2″ from the end) is located well within the
flow of the medium being measured for temperature. This will ensure accurate
readings with minimal response time.
Accuracy
Inaccuracy may be caused by a broken tube, scale shifting in slots from
original position, liquid separation, sensitive bulb not fully immersed in the
media or poor circulation. Poor circulation can be explained as follows: If
there is poor agitation in a fluid, the temperature stratifies or has hot or
cold spots. The thermometer will read only the temperature in which the
sensitive bulb is immersed. It is, therefore, important to locate on
installation the sensitive bulb in the correct position.
Corrosion
The use of separate sockets of special material is recommended for corrosive
or highly abrasive service.
Location
Care should be taken to locate the instrument on the equipment where vibration
is at a minimum.
Thermowell Connection
Remove the thermowell from the thermometer if supplied with one. Install this
thermowell in the pipeline or service as required. Insert the stem of the
thermometer through the thermowell. Position thermometer for best reading
position and tighten down.
Union Bushing (Hub) Connection
Remove the union bushing from the thermometer if supplied with it. Install
this union bushing in the pipeline or service as required.
Insert the stem of the thermometer through the union bushing hole, engaging
stem coupling nut with union bushing threads. Position thermometer for best
reading position and tighten down coupling nut.
LIQUID-IN-GLASS SEPARATION
All liquid-in-glass thermometers are subject to separation of the liquid
column. When this occurs, the thermometer will not read correctly.
Some ranges and types are more readily susceptible to separation than others.
Causes of Separation
- Rough handling in shipment causes most separations. If the thermometer is given a sudden jar, the weight of the liquid column in the bore has sufficient inertia to separate the column.
- If the thermometer with an expansion chamber at the top of the tube (away from the bulb) is accidentally overheated, some of the liquid is driven into the expansion chamber. As the thermometer later cools, the liquid column recedes towards the bulb. If the thermometer is left in a horizontal or inverted position while cooling, part of the liquid will remain in the expansion chamber. This would cause separation of the liquid column.
How to Reunite Separated Liquid Column
When the reservoir or expansion chamber is at top of the tube (away from the
bulb)/ranges below 550°F
Heat the bulb of the thermometer slowly, observing the rise of the liquid in
the tube. The point of separation should be driven into the expansion chamber.
Take care that the chamber never becomes completely filled or the internal
pressure will cause the tube to break.
After the separation enters the expansion chamber, put the thermometer in an
upright position. Give the tube a slight jar so that the particles of
entrapped gas will rise above the liquid. When the liquid recedes, the column
will be joined.
When there is no reservoir at the top of the tube/ranges above 550°F
Put the thermometer bulb in dry ice, so as to draw all the liquid into the
tube. Tap the bulb gently on a hard surface with the thermometer held in an
upright position, bringing the liquid together. When gradual heat is applied
and the liquid rises, the column will be joined.
Scale Rotation
Vari-angle Rotation
REMOTE READING THERMOMETERS
REMOTE READING THERMOMETERS (THR, TRR)
Remote reading thermometers are instruments used to measure temperature from a
remote source. By means of a capillary tube with a sensing probe at one end
and an indicating dial on the other, temperatures can be determined from a
source that is up to 30′ (100 m) away.
Remote reading thermometers are filled with either gas or vapor depending on
the specification. As temperature changes, the gas or vapor expands/contracts,
creating pressure that is measured by a Bourdon tube.
INSTALLATION OF REMOTE READING THERMOMETERS
Accuracy
The thermometer will read only the temperature in which the sensitive bulb is
immersed.
It is important to place at least 2-1/2″ of the sensitive bulb in the media to
ensure reading accuracy.
Corrosion
The use of separate sockets of special material is recommended for corrosive
or highly abrasive service. Capillaries are available in copper braided and
stainless steel (with or without flexible armor), in an assortment of lengths.
FNW recommends using a stainless steel bulb and capillary for all process
temperatures above 500°F (260°C).
Location
These thermometers offer the advantage of taking temperature readings away
from locations that have heavy vibration or are possibly dangerous. Each
thermometer with a front or back flange will have three mounting holes for
securing the thermometer to a panel. Alternatively, u-clamps are available.
Thermowell Connection
Remove the thermowell from the thermometer if supplied with one. Install this
thermowell in the pipeline or service as required. Insert the stem of the
thermometer through the thermowell. Position thermometer for best reading
position and tighten down.
Union Bushing (Hub) Connection
Remove the union bushing from the thermometer if supplied with one. Install
this union bushing in the pipeline or service as required.
Insert the stem of the thermometer through the union bushing hole, engaging
stem coupling nut with union bushing threads. Position thermometer for best
reading position and tighten down coupling nut.
GAS-FILLED THERMOMETERS
Gas-filled thermometers are designed for industrial applications requiring
accurate and uniform response over the entire range. The entire system is
filled under pressure with inert gas for positive movement, accuracy and
sensitivity. The accuracy delivered by this system is +/-0.5% of the full
scale value. We recommend the operating temperature range fall in the upper
half of the dial.
VAPOR-FILLED THERMOMETERS
Vapor-filled thermometers have nonlinear scales (non-equal graduations across
the entire scale). To ensure exceptionally close readings, the operating
temperature should fall in the 2/3 of the scale. The accuracy delivered by
this system is +/-2% of the full scale value.
Note: When selecting a thermometer, always refer to ASME B40.200 (2008)
BIMETAL THERMOMETERS, LIQUID-IN-GLASS THERMOMETERS, REMOTE READING THERMOMETERS
LIMITED WARRANTY
Warranty:
Subject to the limitations expressed herein, Seller warrants that products
manufactured by Seller shall be free from defects in design, material and
workmanship under normal use for a period of one year from installation but in
no case shall the warranty period extend longer than eighteen months from the
date of sale. This warranty is void for any damage caused by misuse, abuse,
neglect, acts of God, or improper installation. For the purpose of this
section, “Normal Use” means in strict accordance with the installation,
operation and maintenance manual. The warranty for all other products is
provided by the original equipment manufacturer.
Remedies:
Seller shall repair or replace, at its option, any non-conforming or otherwise
defective product, upon receipt of notice from Buyer during the Manufacturer’s
warranty period at no additional charge. SELLER HEREBY DISCLAIMS ALL OTHER
EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, ALL IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS OR FITNESS FOR A PARTICULAR PURPOSE.
Limitation of liability:
UNDER NO CIRCUMSTANCES SHALL EITHER PARTY BE LIABLE TO THE OTHER FOR
INCIDENTAL, PUNITIVE, SPECIAL OR CONSEQUENTIAL DAMAGES OF ANY KIND. BUYER
HEREBY ACKNOWLEDGES AND AGREES THAT UNDER NO CIRCUMSTANCES, AND IN NO EVENT,
SHALL SELLER’S LIABILITY, IF ANY, EXCEED THE NET SALES PRICE OF THE DEFECTIVE
PRODUCT(S) PURCHASED DURING THE PREVIOUS CONTRACT YEAR.
Labor allowance:
Seller makes NO ADDITIONAL ALLOWANCE FOR THE LABOR OR EXPENSE OF REPAIRING OR
REPLACING DEFECTIVE PRODUCTS OR WORKMANSHIP OR DAMAGE RESULTING FROM THE SAME.
Recommendations by seller:
Seller may assist Buyer in selection decisions by providing information
regarding products that it manufacturers and those manufactured by others.
However, Buyer acknowledges that Buyer ultimately chooses the product’s
suitability for its particular use, as normally signified by the signature of
Buyer’s technical representative. Any recommendations made by Seller
concerning the use, design, application or operation of the products shall not
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by Seller to make recommendations or give advice to Buyer shall not impose any
liability upon Seller.
Excused performance:
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Seller. Under no circumstances shall Seller be liable for any special,
consequential, incidental, or indirect damages, losses, or expense (whether or
not based on negligence) arising directly or indirectly from delays or failure
to give notice of delay.
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We reserve the right to modify or improve the designs or specifications of our
products at any time without notice.