fusible plug on absorption cooling unit

[Marco Jiang]

Hi, everyone, i am new here. According to CSA requirement:" 1.10.2 A system, unless constructed so it will not
burst due to expansion of the refrigerant when subjected
to abnormal outside temperatures, such as those
generated by a fire, shall be protected by one of the
following types of pressure relieving devices:

a. A safety valve having a 1/4-inch (6.4 mm)
outlet;

b. A rupture member having an outlet not less
than 1/16 inch (1.6 mm) in diameter; or

c. A fusible plug having a maximum fusing point
of 280 F (138 °C) and an outlet not less than
1/16 inch (1.6 mm) in diameter. "
We are following the C option. Consul and dometic are doing in different ways.Can anybody explain how to do this? Our questions:
1, When to weld the fusible plug into cooing unit? Before or after passivation/ painting?
2, if before passivation, will the oven temperature melt the alloy?
3, If after passivation, how to treat the pipe inside of fusible plug?

[frank]

Absorption chillers should incorporate a bursting disc

here's a link http://www.bsb.ie/Rupture_Disks/Reverse_Buckling_Disks/Safety_relief_valves-77-1006.html

[Brian_UK]

Also you can not weld a fusible plug, it will melt and become a welded hole.

[Marco Jiang]

2. CSA requirement:

“1.10 SEALED ABSORPTION SYSTEM

1.10.1 The manufacturer shall present evidence,
acceptable to the testing agency, that the burst strength
of the self-contained refrigerant system is not less than 5
times the maximum working pressure determined at an
ambient temperature of 110 F (43.5 °C).

1.10.2 A system, unless constructed so it will not
burst due to expansion of the refrigerant when subjected
to abnormal outside temperatures, such as those
generated by a fire, shall be protected by one of the
following types of pressure relieving devices:

a. A safety valve having a 1/4-inch (6.4 mm)
outlet;

b. A rupture member having an outlet not less
than 1/16 inch (1.6 mm) in diameter; or

c. A fusible plug having a maximum fusing point
of 280 F (138 °C) and an outlet not less than
1/16 inch (1.6 mm) in diameter. ‘
3, Our questions.

See the above illustration and CSA requirement. Consul is using “fusible plug” as the illustration. We are planning to do the same.We have some questions regarding how to implement this requirement.

3.1 When to weld this plug into the cooling system? Before the passivation and electrophoretic painting? The absorption system should be baked in an oven prior to filling to complement the inside surface passivation at temperature 230°C for 12 hours. If welding the plug before passivation, the plug alloy would melt..

3.2 If we weld the fusible plug after passivation and electrophoretic painting, then the inside surface of the fusible plug would not be passivated. And the welding would also damage the inside passivated surface of cooling tube coil a little bit. Furthermore, the fusible plug with anticorrosion paint would not look so nice like electrophoretic paint..

Could you help us to understand how to produce the absorption cooling system with such fusible plug?

[Brian_UK]

Fusible plugs are normally screwed in not welded.

Why go for the difficult choice?

[Marco Jiang]

Hi,Brian, thanks for information.
Srewed solution is patented by Dometic and also related to charging method.
We are tying other alloy. Let us see if we can solve this problem. Thanks