Black Conical Unions
A black taper seat union is a three-piece malleable cast iron fitting that joins two threaded black steel pipes detachably and seals without a gasket through its taper metal-to-metal seat. When the nut is loosened the joint separates without cutting the line.
Fitted before and after equipment that needs maintenance, such as pumps, valves, meters and boilers, it makes removal easy. Since there is no gasket it is also preferred in high-temperature heating and steam lines; 9 sizes from 1/2″ to 4″ are available.
Main Applications
- Pump inlet and outlet connections
- Detachable mounting of valve, strainer and check valve groups
- Boiler and calorifier connections
- Upstream of heat meters and gas meters (in projects compliant with regulations)
- Maintenance points in steam and condensate lines
- Service separation in compressed air equipment
Technical Data
| Fitting type | Taper seat union: two bodies and a nut |
|---|---|
| Product standard | TS EN 10242, design symbol A (manufacturer information) |
| Material | Blackheart malleable cast iron B 350-10 (sales sheet information) |
| Surface | Black, without galvanized coating |
| Thread | ISO 7-1 Rp female thread (both ends) |
| Seat | Taper, metal-to-metal; no gasket |
| Sizes | 1/2″, 3/4″, 1″, 1 1/4″, 1 1/2″, 2″, 2 1/2″, 3″, 4″ (product range) |
| Pump union | With different end sizes, e.g. 1 1/4″ × 2″ (product range) |
| Permissible pressure | 25 bar, −20 … +120 °C (EN 10242, design A) |
| Pressure at high temperature | 20 bar, up to +300 °C (EN 10242, design A) |
| Leak test | At least 5 bar air or 20 bar water (sales sheet information) |
| Nut | Hexagonal, malleable cast iron |
Material Options
| Part | Black malleable iron | Galvanized malleable iron | Stainless steel casting |
|---|---|---|---|
| Body (two pieces) | Blackheart malleable cast iron B 350-10 | Malleable iron EN-GJMB-350-10, hot-dip galvanized | Investment casting 1.4408 (AISI 316 equivalent), depending on model |
| Nut | Blackheart malleable cast iron B 350-10 | Malleable iron, galvanized | Stainless casting, depending on model |
| Seat surface | Taper metal-to-metal | Taper metal-to-metal | Taper metal-to-metal, depending on model |
| Surface | Black, uncoated | Zinc coated | Stainless, uncoated |
| Pressure rating | 25 bar −20…120 °C, 20 bar 300 °C (EN 10242) | 25 bar −20…120 °C (EN 10242) | Depending on model |
Which material? Because no gasket is used, a black taper seat union stays tight for a long time in hot heating and steam lines; choose a galvanized union for drinking water and a stainless union for corrosive media.
Advantages
Easy Removal
- Loosening the nut separates the equipment without touching the pipes
Gasket-Free Sealing
- Taper metal-to-metal seat; no gasket to replace
- No gasket ageing at high temperatures
Reusable
- After maintenance the same union is retightened and reused
Pump Union Option
- Direct connection to the pump port with different end sizes
Construction and Design Features
- Two bodies with male and female taper faces and a hexagonal nut in the middle
- Sealing by contact of the taper faces instead of a gasket
- The nut clamps the bodies axially; the pipes are joined without turning
- TS EN 10242 design A pressure ratings
Send the union size, both end sizes for a pump union, and the quantity; we will confirm suitable black taper seat unions from stock.
How to Choose?
- Define the removal pointPlan a union on at least one side of every piece of equipment that needs maintenance, such as pumps, valves and meters.
- Measure the sizeDetermine the pipe size in inches; if the pump port differs, choose a pump union.
- Consider the temperatureIn hot and steam lines a gasket-free taper union is an advantage over gasketed types.
- Choose the surfaceUse black unions in closed circuits and gas lines, galvanized unions for drinking water.
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Why ORFA?
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