\begin{tabular}{ll} QUESTION 4 (PUMPS) \ 4.1 & Give THREE moving parts of a reciprocating pump. \ 4.2 & $$ \begin{array}{l} ext { List THREE advantages of a pump with external packing. } \ ext { What is the difference between the flooding head and suction head, support your } \ ext { answer by means of a sketch. }\end{array} $$ \ \hline 13$$ ) $$\end{tabular}

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\begin{tabular}{ll} QUESTION 4 (PUMPS) \ 4.1 & Give THREE moving parts of a reciprocating pump. \ 4.2 & $$ \begin{array}{l}	ext { List THREE advantages of a pump with external packing. } \ 	ext { What is the difference between the flooding head and suction head, support your } \ 	ext { answer by means of a sketch. }\end{array} $$ \ \hline 13$$ ) $$\end{tabular}

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**4.1. Three Moving Parts of a Reciprocating Pump**

1. **Piston (or Plunger):** Moves back and forth to create the pressure differential needed for suction and discharge.  
2. **Connecting Rod (or Crosshead):** Transmits the reciprocating motion from the crankshaft to the piston.  
3. **Valve Assembly (Inlet/Outlet Valves):** Opens and closes cyclically to control the admission of fluid into the pump and its discharge.

---

**4.2. Advantages of a Pump with External Packing**

1. **Ease of Maintenance:**  
   With external packing, adjustments or replacement of the packing material can be done without disassembling the pump. This simplifies routine maintenance and inspection.

2. **Better Leakage Control:**  
   External packing allows for fine adjustment to minimize leakage and control the balance between fluid loss and friction, making it easier to achieve the desired performance.

3. **Reduced Contamination Risk:**  
   Since the sealing interface is external, the process fluid does not mix with any lubricating or packing fluids. This separation helps prevent contamination of the process fluid.

---

**Difference Between Flooding Head and Suction Head**

- **Flooding Head:**  
  This is the static head (height) available at the pump suction when the pump is placed in a flooded condition. In a flooded suction system the pump inlet is located below the free surface of the liquid (or in a sump), so the liquid surrounds the inlet. The flooding head, often denoted as $$ H_f $$, is essentially the vertical distance from the liquid surface to the pump centerline and provides a positive pressure at the pump inlet.

- **Suction Head:**  
  This refers to the vertical distance through which the pump must lift the liquid when the pump is not flooded. It is the net positive suction head (NPSH) required to overcome the effects of gravity and friction in the suction piping. The suction head, usually denoted as $$ H_s $$, represents the lift portion of the system and is limited by atmospheric pressure. Excessive suction head may lead to cavitation.

**Sketch Illustrating the Difference**

$$
\begin{array}{c}
\textbf{(a) Flooded Suction Condition} \[8pt]
\begin{array}{c}
\text{Water Surface} \[4pt]
\framebox(100,20){\ \ \ \ \ } \[4pt]
\text{$$ H_f $$: Flooding Head \ (Vertical distance from water surface to pump centerline)} \[8pt]
\downarrow \quad \quad \quad \quad \quad \quad \quad \quad \downarrow \
\text{Pump Suction Intake (Submerged)} \[4pt]
\framebox(80,20){\ \ Pump\ } \[4pt]
\text{Pump Body}
\end{array}
\end{array}
$$

$$
\begin{array}{c}
\textbf{(b) Non-Flooded (Suction Lift) Condition} \[8pt]
\begin{array}{c}
\text{Water Surface} \[4pt]
\quad \quad \quad \quad \quad \quad \nwarrow \text{Suction Line (with $$ H_s $$)} \[4pt]
\text{Pump Suction Intake (Above Water)} \[4pt]
\framebox(80,20){\ \ Pump\ } \[4pt]
\text{Pump Body}
\end{array}
\end{array}
$$

In the flooded condition, the pump inlet is surrounded by liquid, and the available head ($$ H_f $$) is the difference between the free water level and the pump centerline. In contrast, when the pump is not flooded, the suction head ($$ H_s $$) is the vertical lift the pump must overcome to draw liquid from the source, and it is limited by atmospheric pressure.
**4.1. Three Moving Parts of a Reciprocating Pump** 1. **Piston:** Moves back and forth to create pressure. 2. **Connecting Rod:** Transmits motion from the crankshaft to the piston. 3. **Valve Assembly:** Controls fluid flow into and out of the pump. --- **4.2. Advantages of a Pump with External Packing** 1. **Ease of Maintenance:** Simplifies repairs without disassembling the pump. 2. **Better Leakage Control:** Allows precise adjustments to minimize fluid loss. 3. **Reduced Contamination Risk:** Keeps process fluid separate from packing materials. --- **Difference Between Flooding Head and Suction Head** - **Flooding Head ($$ H_f $$):** The vertical distance from the liquid surface to the pump centerline in a flooded suction system, providing positive pressure at the pump inlet. - **Suction Head ($$ H_s $$):** The vertical lift the pump must overcome to draw fluid from the source in a non-flooded system, limited by atmospheric pressure. **Sketch Illustration:** - **Flooded Suction:** Pump inlet submerged below the liquid surface with $$ H_f $$ providing positive pressure. - **Non-Flooded Suction:** Pump inlet above the liquid surface requiring $$ H_s $$ to lift the fluid. In flooded conditions, $$ H_f $$ ensures sufficient pressure, while in non-flooded conditions, $$ H_s $$ must be managed to prevent cavitation.

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