Stainless steel fittings and threaded accessories for immersion heaters

1. Immersion heater stainless steel fittings

Set for brazing Set for TIG welding


1.1 Brazing assembly description


1: Assembly screw, M4
2: Heating element terminals
3: Grounding nuts
4: Dented washer
5: Grounding stud M4
6: Dented washer
7: Silicone waterproof gasket
8: Hexagonal top plate
9: Brace
10: Fitting with machined sealing surface
11: Thread with gasket groove
12: Pocket extension
13: Bottom plate
14: Heating element brazing
15: Pocket tube
16: Rotation ring with centering bossings
17: Enclosure
18: Unlosable fitting gasket


1.2 TIG welding assembly description

1: Assembly screw, M4
2: Heating elements terminals
3: Grounding nuts
4: Dented washer
5: Grounding stud M4
6: Rotation ring
7: Dented washer
8: Silicone waterproof gasket
9: Hexagonal top plate
10: Brace
11: Fitting with machined sealing surface
12: Ceramic spacer
13: Pocket extension
14: Thread with gasket groove
15: Standard ceramic insulator
16: Bottom plate
17: Pocket tube
18: Centering bossings
19: Enclosure
20: Unlosable fitting gasket


2. Immersion heater stainless steel fittings

– Fittings for incorporation by immersion heater manufacturers
– Designed to make 100% stainless steel immersion heaters, TIG welded, without brazed joints at a price similar to brazed brass fittings
– Exist in TIG version (unassembled) or brazed joint version (assembled)
– Fit the full range of immersion heater enclosures
– Compact size and short length result in reduced weight (Save + / -70% compared to plain stainless steel fittings)
– The fittings thread length allows throw wall mounting with fiber gasket and nut on wall of 6 mm thickness or on threaded socket with flat gasket
– Allows a 360° rotation of enclosure when mounted with their rotation ring

Range: BSPP1”1/2 and M45x2
– Threads rolled according to:
– ISO965-1 and 2 for metric threads
– ISO228-1 (Pipe threads without sealing in the thread) for thread called “Gas Thread”, also known as BSPP.
– Thread clearance for captive gasket
– Large chamfer facilitating correct assembly
– Large machined gasket seat

Manufacturing process:
Deep stamping, followed by threads rolling.
This technique allows a very limited machining, without material losses, and provides a good surface without porosity.

Assembly on enclosures:
– Through a hole in the enclosure. The enclosure is sandwiched between the fitting and a stamped inner ring. Bumps in the ring provide self-centering. This stamped ring costs only 10% of the conventional threaded inner rings.

Gasket between fitting and enclosure:
– The 3 mm thickness, ribbed, 50 Shore silicone gasket, absorbs flatness differences, and remains in place during tightening.
– Guaranteed IP65 ingress protection up to 200 ° C between fitting and enclosure, provided it has a flat bottom without asperities.

Grounding (earthing):
The grounding terminal does not impinge on the surface used for the heating element brazing, allowing the larger diameter heating element tubes and larger bending radius, and room for a center pocket tube. See general design of the grounding hereunder.

Heating element terminal numbering:
Heating element terminal numbers are stamped on the hexagonal top bracket.

Fitting gasket:
Three models of captive gaskets can cover all applications
– Non-asbestos fiber gasket, thickness 2 mm
– NBR O-ring, dia. 4 mm
– Flat PTFE gasket, thickness 2 mm

Inner stamped ring:
– The outside diameter less than or equal to the threaded rings allows to replace them without footprint problem.
– Its large inner diameter does not reduce the passage for heating elements
– The clamping with 3 BTR screws at 120° ensures a good pressure distribution and an excellent mechanical strength. These screw positions increase the clearances between the screw heads and live parts of the heating elements (If respecting the most favorable angle when drilling heating elements holes)
– The M4 recessed hexagonal hole screw heads allow easy and stable entry of hex wrench when adjusting angular position
– Ring made of stainless steel for better durability
– Unalterable stamped earthing logo

Fitting clamping: 9 mm wide hex part, 54 mm on flat for easy passage of wrench

Pressure resistance: 2 MPa (Fitting undrilled and without heating elements). Minimum wall thickness 1.2 mm

Fitting material:
Aisi 304L or Aisi316L stainless steel

– Special position or diameter of holes for heaters according to customer drawing (MOQ apply)
– Customizing or customer references marking (MOQ apply)

2.1 Stainless steel raw material

Designation Nearest equivalences Specific gravity (g/cm3) HRB hardness Tensile

Strength, Stress, N/mm2

Elongation, %
Aisi 304L SUS304L (JIL)
X2CrNi1811 1.4306 (DIN)
Z3CN18-10 (NF)
02Cr18Ni11 (GB)
S30403 (ASTM)
7.93 <92 >485 >40
Aisi 316L SUS316L (JIL)
X2CrNiMo17132 1.4404 (DIN)
Z3CND17-12-02 (NF)
02Cr17Ni12Mo2 (GB)
S31603 (ASTM)
7.98 <95 >485 >40



C Si Mn P S Ni Cr Mo
SUS 304L ≤ 0.03% ≤1.00% ≤2% ≤0.045% ≤0.030% 9.00-13.00% 18.00-20.00%
SUS 316L ≤ 0.03% ≤1.00% ≤2% ≤0.045% ≤0.030% 16.00-18.00% 12.00-15.00% 2.00-3.00%


2.2 Stainless steel Rohs compliance

According to the Directive 2011/65/ dated June 8, 2011 (Rohs), stainless steel alloys are allowed to have a maximum of 0.1% by weight of lead, lead, mercury, hexavalent chromium, PBB (Polybrominated biphenyls), PBDE (Polybrominated Diphenyl Ethers) and 0.01% of Cadmium in weight.
(Provisions of Article 4 and paragraph 1 of Annex II)


3. Assembly process of stainless steel fittings on heating elements (TIG welding)

Make heating elements with extended terminals
TIG butt weld heating elements on
the washer. Pocket must be welded
first. (Welding lines are figured in
Fill with resin, and put usual ceramic
Proceed to TIG weld of washer on
fitting frame
(Att.: for correct welding position,
tentatively put hexagonal plate and
ceramic spacers )


Assemble ceramic spacers
Assemble hexagonal plate and spacer
ring on heating element outputs
TIG weld of hexagonal plate at the
same level than the fitting frame edge
Fit terminals with nuts and washers
and screw the grounding terminal

4. Assembly process of stainless steel fittings on heating elements (Brazed)

Make heating elements as usual

Insert heating element tubes in the bottom plate holes, until they protrudes from hexagonal plate of the insulation distance requested by standards
Proceed to brazing of heating elements on the
bottom (Brazing lines shown in brown)


Fill with resin or elastomere and put usual ceramic insulators
Clean the brazing areas
Fit terminals with nuts and washers and screw the grounding terminal