On a steam line the question is not what the fitting is rated at cold, but what it is rated at once the line is hot. TUPY Brazil threaded fittings are rated at 25 bar up to 120 °C, and the permitted pressure falls on a defined curve from there to 20 bar above 300 °C.
From -20 to +120 °C the maximum working pressure is 25 bar. Between 120 and 300 °C the permitted pressure is obtained by linear interpolation, and above 300 °C it is 20 bar. Two worked examples from the TUPY technical catalogue: at a working temperature of 180 °C the permitted pressure comes to 23.33 bar; at a working pressure of 22 bar the maximum permitted temperature comes to 228 °C.
One bar is 1.02 kgf/cm² or 14.5 psi. In system design a safety factor of at least four times the maximum working pressure must be allowed for — on steam that margin is the whole point of specifying a rated fitting rather than a generic one.
TUPY BSP fittings are blackheart malleable cast iron, grade JMB 350-10 to ISO 5922, EN 1562 and ABNT NBR 6590: minimum tensile strength 350 MPa, minimum yield 200 MPa, minimum elongation 10 per cent, Brinell hardness about 150. The coefficient of thermal expansion is 12 per °C over the range 20 to 400 °C, and thermal conductivity is 0.42 W/cm·K — figures that matter when a hot line is being anchored and guided.
Every fitting is hydrostatically tested at 100 bar in sizes 1/8 to 4 inch, and 64 bar in 5 and 6 inch.
The fittings seal on the thread itself to ISO 7-1 — an internal parallel thread Rp against an external taper thread R — so there is no elastomeric seal in the joint to age at temperature. Pressure-tight threads are inspected to ISO 7-2 with number 1 and number 3 gauges.
TUPY does not approve welding of its fittings. On a steam line, where the joint is cycled hot and cold, a welded malleable iron fitting is a poor risk: the heat-affected zone picks up martensite and cementite and turns brittle.
| Material | Blackheart malleable cast iron JMB 350-10 (ISO 5922, EN 1562, ABNT NBR 6590) |
|---|---|
| Standards | EN 10242, ISO 49, ABNT NBR 6943 |
| Sizes | 1/4 inch to 6 inch |
| Maximum working pressure | 25 bar from -20 to +120 °C |
| Hydrostatic test pressure | 100 bar (1/8 to 4 in), 64 bar (5 to 6 in) |
| Threads | Internal parallel Rp, external taper R, to ISO 7-1 |
| Finish | Hot-dip galvanised to ISO 1461 and ABNT NBR 6323, or black (oiled) |
25 bar from -20 to +120 °C. Between 120 and 300 °C the permitted pressure is interpolated — 23.33 bar at 180 °C, for example — and above 300 °C it is 20 bar.
The rating continues above 300 °C at 20 bar. Working the other way, a line running at 22 bar is permitted up to 228 °C.
Yes. The same range is used for hot and cold water, steam, fuels, hydraulic oil, compressed air and gases.
At least four times the maximum working pressure, per the TUPY technical catalogue.
Stocked in Dubai and shipped across the Gulf, Iraq, Turkey, the Caucasus and South Asia.
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