Engr Polash Biswas Tech-Bangla

Engr Polash Biswas Tech-Bangla Automation Engineer, PLC, VFD, HMI ( Maintenance & Utility )

Learning of Engineering Tropics





আমি হেঁটে এগিয়ে যেতে দৌড়ে হাফিয়ে উঠতে চায় না... ‘পুতুলের জায়গায় নিজেকে প্রতিস্থাপন করতে চায় না. Profession Engineerin...
18/04/2026

আমি হেঁটে এগিয়ে যেতে দৌড়ে হাফিয়ে উঠতে চায় না... ‘পুতুলের জায়গায় নিজেকে প্রতিস্থাপন করতে চায় না. Profession Engineering ( Maintenance & utility ) :

Thanks a lot of dear Malobi Mondol Tuli

Delta VFD Basic Parameter Setting (Easy Guide)ধরি তুমি একটি 3 Phase Motor (415V, 50Hz) চালাবে🔹 Step 1: Factory Reset (শু...
26/03/2026

Delta VFD Basic Parameter Setting (Easy Guide)
ধরি তুমি একটি 3 Phase Motor (415V, 50Hz) চালাবে

🔹 Step 1: Factory Reset (শুরু করার আগে)

👉 পুরানো সেটিং থাকলে সমস্যা হবে
Parameter: P00.02 = 10 (Factory Reset)
🔹 Step 2: Control Mode নির্বাচন
P00.00 = 0 → Keypad control
P00.00 = 1 → External (Terminal control)
📌 Beginner হলে:

👉 P00.00 = 0 (Keypad দিয়ে চালাও)
🔹 Step 3: Frequency Setting
P00.01 = 0 → Keypad frequency
P00.01 = 1 → External (Analog input)

👉 সেট করো:
P00.01 = 0
🔹 Step 4: Maximum Frequency
P00.02 = 50 Hz

👉 বাংলাদেশে standard: 50Hz
🔹 Step 5: Acceleration & Deceleration Time
P00.10 = 10 sec (Start time)
P00.11 = 10 sec (Stop time)

📌 মানে: 👉 Motor 0 থেকে 50Hz যেতে 10 সেকেন্ড লাগবে
🔹 Step 6: Motor Data Setting (খুব গুরুত্বপূর্ণ ⚠️)
Motor nameplate দেখে সেট করো:
P01.00 = 50 Hz
P01.01 = 415 V
P01.02 = Motor Current (Amp)

👉 যেমন: 12A হলে → P01.02 = 12
🔹 Step 7: Run Command
P04.00 = 0 → Keypad run
P04.00 = 1 → External switch

👉 Beginner: P04.00 = 0
🔹 Complete Basic Setting (Ready List)

P00.00 = 0
P00.01 = 0
P00.02 = 50
P00.10 = 10
P00.11 = 10
P01.00 = 50
P01.01 = 415
P01.02 = 12 (motor অনুযায়ী)
P04.00 = 0
🔵

PLC Input & Output Devices–এর বিষয়টা basic থেকে clearভাবে ব্যাখ্যা করছি।🔷 PLC কীভাবে কাজ করে (Overall Concept)PLC আসলে ৩...
02/02/2026

PLC Input & Output Devices–এর বিষয়টা basic থেকে clearভাবে ব্যাখ্যা করছি।
🔷 PLC কীভাবে কাজ করে (Overall Concept)
PLC আসলে ৩টা ধাপে কাজ করে—
INPUT ➜ LOGIC (Program) ➜ OUTPUT
মানে,
👉 মাঠের ডিভাইস থেকে সিগন্যাল নেয়
👉 প্রোগ্রাম অনুযায়ী সিদ্ধান্ত নেয়
👉 তারপর যন্ত্র চালু/বন্ধ করে

🟢 INPUT DEVICES (PLC-তে সিগন্যাল দেয়)
এগুলোকে বলা হয় Sensors / Command devices
এরা PLC-কে বলে দেয় “কি হচ্ছে”

1️⃣ Push Button
Manual switch
মানুষ চাপ দিলে সিগন্যাল দেয়
উদাহরণ: START / STOP বোতাম
Signal টাইপ: Digital (ON/OFF)
🧠 PLC বুঝে:
Button চাপা হয়েছে = 1
না চাপা = 0

2️⃣ Limit Switch
কোনো বস্তু শেষ পজিশনে পৌঁছালে কাজ করে
Conveyor, lift, machine safety তে ব্যবহৃত
Signal: Digital
উদাহরণ:
➡️ Door পুরো বন্ধ হলে limit switch ON

3️⃣ Proximity Sensor
স্পর্শ ছাড়াই বস্তু detect করে
Metal / object থাকলে সিগন্যাল দেয়
Signal: Digital
উদাহরণ:
➡️ Conveyor-এ লোহা আসছে কিনা detect

4️⃣ Photo Sensor
আলো দিয়ে object detect করে
Packaging, counting system এ ব্যবহৃত
Signal: Digital
উদাহরণ:
➡️ Bottle এসেছে কিনা detect

5️⃣ Temperature / Pressure Sensor
Actual value মাপে
Boiler, compressor, HVAC system এ ব্যবহৃত
Signal: Analog (0–10V / 4–20mA)
উদাহরণ:
➡️ Temp = 85°C
➡️ Pressure = 6 bar
🧠 PLC (Logic / Brain)
PLC এখানে—
Input পড়ে
Program execute করে (Ladder / FBD / STL)
Decision নেয়
উদাহরণ logic:
Copy code

IF Push Button = ON
THEN Motor = ON

🟠 OUTPUT DEVICES (PLC থেকে কাজ নেয়)
PLC যেগুলোকে চালায়

1️⃣ Relay
Small load control
Isolation দেয়
PLC output → Relay → Load

2️⃣ Contactor
High power load (Motor, Heater)
PLC সরাসরি motor চালায় না
➡️ Contactor দিয়ে চালায়

3️⃣ Solenoid Valve
Air / Water / Steam control
Pneumatic & Hydraulic system এ ব্যবহৃত
উদাহরণ:
➡️ Valve open / close

4️⃣ Indicator Lamp
Status দেখায়
Green = RUN
Red = FAULT

5️⃣ Motor / Buzzer
Final action device
Production কাজ এখানেই হয়

🔁 ছবির Example টা বুঝি
Example Flow:
Copy code

Push Button Press
↓
PLC Input ON
↓
PLC Logic Execute
↓
Output ON
↓
Motor / Lamp ON

🧩 Real Industrial Example
Boiler System
Temp Sensor → PLC Input
PLC Logic → High Temp?
Solenoid Valve → Open
Alarm / Buzzer → ON

Weekly Diesel Fire Pump – Maintenance & Testing SOP (10–15 minutes)1) Safety & Pre-Start ChecksEnsure pump room ventilat...
22/01/2026

Weekly Diesel Fire Pump – Maintenance & Testing SOP (10–15 minutes)

1) Safety & Pre-Start Checks
Ensure pump room ventilation is running (exhaust/fresh air OK).
Check for fuel/oil/coolant leaks around the engine, pipes, and tank.

Check the controller: no alarms/faults, “Auto” healthy indication.
Fuel tank ≥ 75% full.

Engine oil level: dipstick between MIN–MAX.
Coolant level: radiator/expansion tank at correct level.

Battery terminals: clean, tight, no corrosion.
Battery charger ON and showing normal charging status.

2) Weekly No-Load Run Test (10–15 minutes)
Put the controller in Manual/Test mode (as per your site SOP).
Start the diesel engine.
Run for 10–15 minutes and observe/record:
Oil pressure: stable/normal
Coolant temperature: rising normally, not overheating
Charging voltage / alternator: charging OK
Smoke / vibration / abnormal noise: none
Leaks: none (fuel/oil/coolant)
Stop the engine properly and return the controller to Auto.

✅ Note: Weekly no-load test confirms engine health. It’s also good practice to do a flow test (test header/return line) monthly or as required by your SOP/standard.
3) After-Test Checks
Recheck for new leaks or loose connections.
Confirm the controller shows normal status (no new alarm).
Confirm battery charger is back to normal charging.
Write all readings in the logbook and sign.

MWM Gas Engine–based CHP (Combined Heat & Power) সিস্টেমের।1️⃣ Gas Generator → Electricityগ্যাস ইঞ্জিন (Natural Gas / Bi...
20/01/2026

MWM Gas Engine–based CHP (Combined Heat & Power) সিস্টেমের।

1️⃣ Gas Generator → Electricity
গ্যাস ইঞ্জিন (Natural Gas / Biogas) ঘুরে Generator চালায়
এখানে সাধারণত
Electrical efficiency ≈ 40–43%
অর্থাৎ জ্বালানির ~43% বিদ্যুতে রূপান্তরিত হয়

2️⃣ Jacket Water Heat Recovery (78–90°C)
ইঞ্জিন সিলিন্ডার ঠান্ডা রাখতে Jacket Water ব্যবহার হয়
এই পানির তাপমাত্রা:
78–90°C (Hot Water)
ব্যবহার:
Process Hot Water
Boiler Feed Water preheating
Space Heating
Absorption Chiller (Cooling)

3️⃣ Intercooler Heat (42–45°C)
Turbocharger থেকে আসা বাতাস ঠান্ডা করতে Intercooler ব্যবহৃত হয়
তাপমাত্রা:
42–45°C (Warm Water)
ব্যবহার:
Low temperature washing
Pre-heating
HVAC support

4️⃣ Exhaust Gas Heat (≈450°C)
সবচেয়ে বেশি শক্তি নষ্ট হয় এক্সহস্ট দিয়ে
Exhaust gas ≈ 450°C
Heat Recovery Boiler (HRSG) ব্যবহার করে পাওয়া যায়:
🔥 Steam
🔥 Hot Water
❄️ Chilled Water (Absorption Chiller)

5️⃣ Overall Efficiency “Boost Up”
শুধু বিদ্যুৎ: ~43%
বিদ্যুৎ + Heat Recovery:
⚡🔥 Total efficiency ≈ 80–86%
এটাকেই বলে CHP / Cogeneration

6️⃣ কেন CHP এত গুরুত্বপূর্ণ?
✔ Fuel saving
✔ Electricity cost কম
✔ Boiler fuel কম লাগে
✔ CO₂ emission কম
✔ Industry energy efficiency বাড়ে

7️⃣ Garments / Industry Example
আপনার আগের আগ্রহ অনুযায়ী (Garments / Utility system):
Generator → Electricity (machine, lighting)
Jacket water → Process hot water
Exhaust gas → Steam for boiler / ironing
Intercooler → Washing / HVAC support

সংক্ষেপে মনে রাখার ট্রিক 🧠
Gas → Power + Heat → Zero Waste Energy

1️⃣ What is the function of a chilled water pump in an HVAC system?The chilled water pump circulates chilled water from ...
18/01/2026

1️⃣ What is the function of a chilled water pump in an HVAC system?
The chilled water pump circulates chilled water from the chiller evaporator to the cooling coils of AHUs, FCUs, or process heat exchangers and then returns the warmed water back to the chiller.
Main functions:
Maintains continuous water circulation
Transfers heat from the building/process to the chiller
Ensures proper flow rate and pressure
Prevents chiller trip due to low flow

🔹 Without the pump, cooling cannot occur, even if the chiller is running.

2️⃣ What is the difference between primary and secondary chilled water pumps?
Item
Primary Pump
Secondary Pump
Purpose
Circulates water through the chiller
Distributes water to AHUs/FCUs
Flow type
Constant flow (mostly)
Variable flow (VFD controlled)
Control
Based on chiller requirement
Based on cooling demand
Energy efficiency
Lower
Higher
Application
Small or basic systems
Medium & large HVAC plants
Why Primary–Secondary system is used:
Protects chiller minimum flow
Improves energy efficiency
Allows variable flow on load side

3️⃣ How do you calculate the flow rate (GPM) of a chilled water pump?
Standard Formula:
Copy code
LaTeX

\textbf{GPM = \frac{TR \times 24}{\Delta T}}

Where:
TR = Cooling load (Ton of Refrigeration)
ΔT = Temperature difference between supply and return water
Example:
Cooling load = 100 TR
Supply temperature = 7°C
Return temperature = 12°C
ΔT = 5°C

🔹 This flow rate is used along with head loss to select the pump.

4️⃣ What are common problems in chilled water pumps and their causes?
Common issues and causes:
1. Low Flow
Air trapped in the system
Blocked strainer
Partially closed valves
Damaged impeller
2. Cavitation
Low suction pressure
High water temperature
Poor NPSH design
3. High Power Consumption
Oversized pump
No VFD
Excessive throttling
4. Seal and Bearing Failure
Shaft misalignment
Dry running
Poor water quality
5. Vibration and Noise
Unbalanced impeller
Loose foundation
Coupling problems

5️⃣ Why is balancing important in a chilled water pumping system?
Balancing ensures:
Design flow reaches each AHU/FCU
Uniform cooling throughout the building
Stable control valve operation
Reduced energy consumption
Without balancing:
Some areas overcool, others undercool
Pump energy is wasted
Chiller efficiency drops
System becomes unstable

🔹 Balancing is done using:
Balancing valves
Differential pressure measurement
Flow meters

🔹 What is E7018 Welding Electrode?E7018 is a low-hydrogen, iron powder–coated SMAW (Stick Welding) electrode.It is widel...
17/01/2026

🔹 What is E7018 Welding Electrode?
E7018 is a low-hydrogen, iron powder–coated SMAW (Stick Welding) electrode.
It is widely used for high-strength and critical welding applications such as structural steel, boilers, pressure vessels, bridges, and power plants.

🔹 Meaning of E7018 (AWS Classification)
▶ E – Electrode
Indicates it is a welding electrode used in Shielded Metal Arc Welding (SMAW).
▶ 70 – Tensile Strength
Weld metal tensile strength: 70,000 PSI
Approximately 490 MPa
Suitable for medium to high-strength carbon steels
▶ 1 – Welding Position
Means All Position Welding:
Flat
Horizontal
Vertical
Overhead
▶ 8 – Coating & Current Type
Low Hydrogen
Iron Powder Coated
Produces smooth arc and strong weld metal
Resistant to hydrogen-induced cracking
🔹 Why Low Hydrogen is Important?
Low hydrogen coating:
✔ Prevents weld cracking
✔ Improves toughness and ductility
✔ Ensures strong weld in thick sections
✔ Ideal for critical and load-bearing structures
⚠ Moisture absorption can cause hydrogen cracking
🔹 Polarity & Current
Parameter
Value
Current
AC or DC
DC Polarity
DCEP (Reverse Polarity)
Arc Stability
Very stable
Pe*******on
Medium to deep
🔹 Recommended Amperage Range
Electrode Size
Current Range
2.5 mm
70–100 A
3.2 mm
90–130 A
4.0 mm
120–170 A
5.0 mm
160–220 A
🔹 Storage & Baking Requirements (Very Important)
❌ If electrode becomes moist:
Porosity in weld
Hydrogen cracking
Weak weld joint
✅ Proper storage:
Re-baking temperature: 250–300°C
Holding oven temperature: 100–150°C
Must be stored in rod oven, not open air
👉 E7018 must always be kept dry
🔹 Applications of E7018
Structural steel fabrication
Boilers & pressure vessels
Bridges and heavy structures
Power plants and refineries
Shipbuilding
Heavy machinery fabrication
🔹 E6013 vs E7018 (Quick Comparison)
Feature
E6013
E7018
Tensile Strength
Lower
Higher
Hydrogen Level
High
Low
Crack Resistance
Low
High
Skill Requirement
Low
High
Critical Jobs

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