1.
Standard for ¼" and 3/8" element with
options of male(1/2"npt,3/4"npt,1"npt)
and female threads(1/2"npsm ,1/2"npt)
2. Heavy duty for ¼" and 3/8" element
with options of male(1/2"npt,3/4"npt,1"npt)
and female threads(1/2"npsm ,1/2"npt)
3. Limited space wells
4. Socket weld series standard and Heavy duty
5. Sanitary type thermowells
6. Flanged thermowells
7. Teflon thermowells
Selection of Thermowells
Material : The longevity factor
Material chosen for Thermowells is governed by the corrosion
conditions the well will face.The high polish given
to all stainless and other wells provide maximum corrosive
resistance.
Strength of material is considered rather than corrosion,
Brass well may be good for corrosion standpoint but
stainless steel well may be required for high pressure
requirements.
Always consult pressure- temperature ratings given for
each well type.
Connection : The installation factor
Wells are available of threaded, flanged and socket
weld type with standard bore sizes
Threaded wells are all made in readily welded or brazed
materials. This is important for installations requiring
seal welding or Brazing. The pipe thread provides the
mechanical strength, the weld merely seals. Flanged
wells (other then Van Stone type) consist of a bar stock
well which is solidly welded to a top quality flange.
Standard construction uses a primary "J" groove
weld and a bevel groove secondary weld. Both welds are
machined to produce a clean fillet. This double welded
construction eliminates possibility of crevice corrosion
and stress problems since no open joints are exposed
from either inside or outside the installation.
Socket weld wells are simple to install - merely weld
them into place. These wells fits A.S.A standard socket
weld couplings or flanges. The resulting installation
is clean and tight.
Insertion Length : The accuracy factor
The distance from the tip of the well to the underside
of thread is the insertion length named as "U"
Length. For best results and accuracy, insertion length
should be long enough to permit the entire temperature
sensitive part of the element to project into the medium
being measured.
A properly installed thermometer bulb will project into
liquid an amount equal to its sensitive length plus
at least one inch.
In air or gas , the bulb should be immersed to its sensitive
length plus at least three inches.
Thermocouples and thermistors have shorter sensitive
lengths, therefore can use the smallest insertion lengths,
Bi- metal thermometers, resistance thermometers and
liquid-in-glass thermometers have bulbs with sensitive
portions between one and two inches long. Therefore,
the minimum standard insertion length of 2 ½"
must be entirely immersed in liquid for proper accuracy.
Always determine the sensitive length of the bulb before
choosing an insertion length.
The most important is Dead length, i.e that are required
to pass through walls, pipe fittings, etc., is taken
into account when choosing the necessary well insertion
length.
Bore Size : The interchangeability factor
Several type of temperature measuring instruments are
used in any installation. With the standard bore size
selection, maximum flexibility can be achieved within
the plant.
The same well can accommodate either thermocouple, resistance
thermometer,bi-metal thermometer, or test thermometer.
Following bore sizes cover the most commonly used temperature
sensing elements
260 Diameter Bore: Bi - metal Thermometers (1/4"
Stem)
Thermocouples- (# 20 Gauge )
Liquid-in-gas test Thermometers (Unarmored)
Other elements having .252 maximum diameter
.385 Diameter Bore : Bi - metal Thermometers (3/8"
stem)
Thermocouples - (# 14 Gauge)
Liquid-in-glass Test Thermometers (Unarmored)
Other elements having .377 maximum diameter
Tapered or Straight Shank : The Velocity Rating
Factor
Tapered shank wells provide greater stiffness for the
same sensitivity. The higher strength-to-weight ratio
gives these wells a higher natural resonant frequency
than for an equivalent length straight shank well, permitting
operation at higher fluid velocities.
Quality Procedures and Tests
Stress Relieving by solution annealing
Electopolishing/Buffing
Full penetration weld
Positive Material Identification
Stellite and other wear -resistant coatings
Hydrostatic test internally and externally
Dye penetration tests
Ultrasonic tests
X -rays
Stress calculations
Visual inspection of raw material
- Ultrasonic testing of raw material
- Chemical analysis
- Dimensional check
- Thread Go/No Go check
- Pneumatic pressure test
- Impulse test
- Pressure impulse test
- Vibration test
- Make & break hydrostatic test
- Wet calibration of flow elements
- Temprature cyclic test
- Helium leak test
- Radiographic test for welds
- Crush test
- Blend test
- Tensile test
- Flexibility test |
