Stell, Bronze, Brass, and a Newbie 1

[Lorus]

Howdy:

I am a relatively new engineer, and my knowledge of some basic specification topics like pipe materials are just awful.

If anybody could toss me over some help it would be greatly appreciated.

1. For black steel pipe, is a di-electric union required when using malleable iron, cast iron, stainless, carbon or any other steel type fittings? When do you use which?

2. What is the difference between bronze and brass, and when should you use each?

3. Do you need a di-electric union between copper and bronze/brass fittings?

 

[ApC2Kp]

lorus,

1) Use the di-electric union to isolate steel / iron piping from copper / brass piping. This is based on the galvanic series for potential difference between metal elements.
2. Bronze materials would be mixture of copper, tin, and other elements such as aluminum, manganese, iron, lead, zinc, and silicon. Typical brass materials are copper and zinc with smaller amounts of other elements. The zinc in brass can be selectively attacked, as it is the second most active metal compared to magnesium in galvanic series. Gas vapor services or neutral liquid services (water) would be OK for brass. Bronze is more resistant than brass for a corrosion service like seawater. Zinc can be half the cost of copper $/lb. so expect to pay more for bronze.
3) Bronze to brass would have litttle galvanic potential difference, so connect bronze and brass together without a di-electric union between them.

 

[jsummerfield]

Become familiar with the ASTM or corresponding ASME material specifications. An example is SB-111, UNS C28000 for one grade of brass. One grade of steel is SA-105, UNS K03504. One grade of stainless steel is SA-336 F316L, UNS S31603. Many different grades exist for each metal. I do not use black steel, cast iron or malleable iron.

The galvanic series relates to the reactivity between the metals and the direction that the ions move.

Example bronze compositions follow for starters:
Tin Bronze, ASTM B564 Grade UNS C90500
Composition (Percent)
Cu 86.0 to 89.0
Sn 9.0 to 11.0
Pb 0.30 max
Zn 1.0 to 3.0
Ni 1.0 max
Fe 0.2 max
S 0.05 max
P 0.05 max

Manganese Bronze ASTM B584 Grade UNS C86500
Composition (Percent)
Cu 55.0 to 60.0
Sn 1.0 max
Pb 0.4 max
Ni 1.0 max
Fe 0.4 to 2.0
Al 0.5 to 1.5
Mn 0.1 to 1.5
Zn 36.0 to 42.0

Cast Aluminum Bronze ASTM B148 Grade UNS C95400
Composition (Percent)
Cu 83.0 min
Al 10.0 to 11.5
Fe 3.0 to 5.0
Mn 0.50 max
Ni 1.5 max



John