POCKETS/THERMOWELLS
Some sensors can be fitted directly into the process by means of an integral process connection or by using an appropriate compression fitting. Other applications require a pocket or thermowell which is a permanent fitting into the process yet allows the sensor to be inserted or removed without interruption.
Pockets invariably increase the response time and obviously the thicker and heavier the pocket the more the response time will be increased. Some styles use spring loading which keeps the inset in permanent contact with the pocket. However, it is the radial clearance between the inset and pocket which has the greatest influence on response time.
For improved response the inset should be assembled into the pocket using thermally conductive grease. The following illustrations show the six most popular styles of pockets/thermowells.
Note: Pocket immersion lengths are relative to the probe lengths shown.
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STW Style 1
All welded 316 ST/STEEL construction for screw fitting into process connection, suitable for STS sensors Style 1 and 9. Sheath 7.9 dia x 71, 96, 146, 196, 246 immersion
Probe lengths 75, 100, 150, 200, 250
Process thread 3/4" BSP Parallel
Internal thread 1/2" BSP |
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STW Style 2
All welded 316 ST/STEEL construction with brass compression gland, suitable for style 2, 4 & 6 sensors.Sheath 7.9 dia x 23, 48, 98,148, 198 immersion
Probe lengths 75, 100, 150, 200, 250
Process thread 1/2" BSPT
Compression fitting 1/4" BSPT x 6.0 dia. |
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STW Style 3
All welded 316 ST/STEEL construction "weld-in" pocket, suitable for Style 1, 9 and Style 2, 4 & 6 sensors when used in conjunction with a compression gland. Sheath 7.9 dia x 55, 80, 130, 180, 230 immersion
Probe lengths 75, 100, 150, 200, 250
Head 25.4 dia x 26 long typical
Internal Thread 1/2" BSP Parallel |
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STW Style 4
Solid turned 316 ST/STEEL construction sensor for screw fitting into process connection, suitable for Style 1 sensors. Parallel Sheath 13.4 dia x 57 & 82 immersion
Probe lengths 75 & 100
Tapered Sheath 13.4 to 19.0 dia x 132, 182, 232 immersion
Probe lengths 150, 200, 250
Process Thread 3/4" BSP Parallel
Internal Thread 1/2" BSP Paralle |
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STW Style 5
All welded 316 ST/STEEL construction for bolting to a flanged process connection. Due to the wide variety of, dimensional, material, pressure and pipe size requirements, all thermowells of this style are manufactured to customers specifications. |
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