Hot dip continuous galvanizing line

Current + Pressure + Speed + Overlap
= Proper Fusion

“High Current = Hole”
“Low Current = Weak Joint”

Proper Fusion
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Improper Fusion
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PHP NOF Continuous Galvanizing Mills Limited

Executive- Sales & Marketing

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Q: Dew point changes from −40°C to −60°C. What happens?
Options:

A) Dew point increased
B) Dew point decreased
C) Gas moisture increased
D) No effect

✍️ Question (Galvalume Line – Sink Roll Rotation)

Read the passage and answer the questions below:

In a continuous Galvalume coating line, the sink roll inside the coating pot plays a critical role in guiding the steel strip and maintaining coating quality. Sometimes the sink roll does not rotate properly during operation, which causes coating defects and line instability. This problem is influenced by several factors such as sink roll pickup, dross jamming, bearing condition, strip tension, bath temperature, misalignment, and blockage of holes in hole-type sink rolls. Understanding the probability distribution of these causes helps operators to identify the root cause quickly and take corrective action.

(a)
What is meant by sink roll pickup in a Galvalume coating pot? Explain briefly.
(2 marks)

(b)
Mention any four causes of sink roll not rotating in a Galvalume pot.
(4 marks)

(c)
Explain why excessive strip tension can stop sink roll rotation, especially for thicker strips.
(2 marks)

(d)
The causes of sink roll not rotating are distributed as follows:
Pickup 35%, Dross jamming 20%, Bearing problem 15%, Strip tension 10%, Temperature imbalance 8%, Misalignment 7%, Hole blockage 5%.
Draw a simple bar chart or pie chart to show this 100% probability distribution.
(2 marks)

Galvalume bath-এ Aluminium (Al) খুব সহজে Oxygen-এর সাথে reaction করে।

N₂ একটি inert gas, তাই bubbling করলে
👉 molten metal-এর ভিতরে O₂ কমে যায়
👉 Al oxidation কম হয়
👉 dross (Al₂O₃, ZnO) তৈরি কম হয়।