Technical information

Nozzle designs - location of a support collar
WIKA data sheet IN 00.26

This technical information describes the influence of theflange nozzle on the construction details of the thermowellthat has to be optimised after a wake frequency calculation towithstand the process loads.
In general, for standard thermowells the flange nozzle design
has only little influence on the thermowell geometry. It justneeds to be assured that the stem will fit into the flange
nozzle and the flange face of the thermowell matches theflange face of the nozzle flange.

In case the thermowell didn´t pass the wake frequency
calculation and there is no possibility to optimise thethermowell by a reduced and reinforced stem, in many cases
the support of the thermowell in the flange nozzle by one
or two support collars is the first choice (for further detail
information please see Technical information IN 00.15).
In this case, the flange nozzle has a high influence on thecorrect thermowell design - especially considering thefollowing aspects:■■ Nozzle flange design■■ Excess penetration inside the nozzle pipe■■ Weld seam between the nozzle and the piping wall

Nozzle flange design
Any flange design (e.g. welding neck flange, threaded flange,
slip-on flange) can be used as a nozzle flange, as long as theinside diameter of the flange is equal to or bigger than theused nozzle inner diameter. Problems can arise if the flange/
pipe combination provides a small inside diameter, e.g.
socket weld flanges:

Flange ID “c”

Nozzle ID (pipe schedule)

Possible combinations

Inside diameter cNozzle ID

DN 1" class 150 or 300

1.05" (26.7 mm)

Schedule 40, 80 or 160

DN 1.5" class 150 or 300

1.61" (40.9 mm)

Schedule 40, 80 or 160

DN 2" class 150 or 300

2.07" (52.6 mm)

Schedule 40, 80 or 160

Class 600 and higher

To be specified

Individual check required

WIKA data sheet IN 00.26 ∙ 04/2016

Page 1 of 4

Excess penetration inside the nozzle pipe
The welding connection between nozzle flange and stand-off
pipe has to be done to avoid any kind of excess penetration.
This would reduce the inner diameter of the nozzle pipe andprevent the correct installation of a support collar. If there isexcessive excess penetration, this irregularity needs to beremoved (e.g. by grinding) to allow the correct installation of
the support collar. The same is needed for the weld seam
between the pipe and the weld stub, if the support collar islocated below this welding connection.

Any excess
penetrations orirregularities of theweld seam need tobe removed

Weld seam between the nozzle and the piping wall

Excessive
excess penetration
not acceptableNozzle projection length

Excessive
excess penetration
not acceptable

UNLUNLFor standard nozzle designs this formula is correct, butdifferent nozzle designs require different methods ofcalculation.

Nozzle projection length

Excessiveexcess penetration
not acceptableNozzle projection length

UNL

In the Technical information IN 00.15, the location for the first
support collar is defined as:
Nozzle projection length - 1" (25.4 mm)

1" (25.4 mm)

UNL = usable nozzle length; Details see on page 3

Page 2 of 4

WIKA data sheet IN 00.26 ∙ 04/2016

For instance, if the nozzle pipe is welded to the pipeline via a
reducer, the “1-inch-rule” will not apply, because the support
collar will be located in the large diameter without any contact
to the nozzle pipe.

Wrong positioning of
support collar without
nozzle contact

1" (25.4 mm)

Calculation of the “usable nozzle length”
The wide variety of nozzle designs require that each
installation has an individual calculation of the usable nozzle
length. The general statement in the Technical information
IN 00.15 “Nozzle projection length – 1" (25.4 mm)” needs
to be verified for each nozzle design. As shown, the usable

nozzle length does not only depend on the fittings (e.g.
flange, stand-off pipe, reducer, etc …), but also on existing
excessive welding irregularities, machining these welding
defects is generally not done.

Nozzle projection length

Excessive
excess penetration
not acceptable

UNL

UNL
Excessive
excess penetration
not acceptableNozzle projection length

Excessive
excess penetration
not acceptableNozzle projection length

UNL

Examples of “usable nozzle lengths” (UNL)

1" (25.4 mm)

WIKA data sheet IN 00.26 ∙ 04/2016

Page 3 of 4

Welding irregularities which make a proper “interference fit” installation impossible
The ASME PTC 19.3 TW-2016 defines the term of rigid
support as an “interference fit” between the support collar
and the installed “nozzle pipe”.
Any kind of displacement or angular offset between theflange connection of the nozzle will not allow for a proper
installation of the support collar inside the nozzle piping withan interference fit.
Displacement

Displacement

Angular displacement

Angular displacement

Any displacement
or angulardisplacement needs
to be avoided

If welding irregularities exist, the oversized support collar will
be over-machined for installation – an interference fit is now
impossible and the engineered thermowell is unusable.

Any displacement
or angulardisplacement needs
to be avoided

Inside diameter J

In case of increasing inner diameter (flange ID “J” <nozzle ID), too much material will be cleared away fromthe oversized support collar – an interference fit is now
impossible and the calculated thermowell is unusable.

© 2014 WIKA Alexander Wiegand SE & Co. KG, all rights reserved.
The specifications given in this document represent the state of engineering at the time of publishing.
We reserve the right to make modifications to the specifications and materials.

Page 4 of 4WIKA data sheet IN 00.26 ∙ 04/2016

WIKA Alexander Wiegand SE & Co. KG
Alexander-Wiegand-Straße 30
63911 Klingenberg/GermanyTel.
+49 9372 132-0
Fax+49 9372 132-406
info@wika.de
www.wika.de04/2016 EN

Nozzle ID(pipe schedule)