\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}

Question

\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: Moving Parts of a Reciprocating Pump**

Three moving parts of a reciprocating pump are:  
1. **Piston:** Moves back and forth in the cylinder to change the pressure.  
2. **Connecting Rod:** Transmits motion from the driving mechanism (e.g., crankshaft) to the piston.  
3. **Valve Assembly:** Includes the inlet and outlet valves that open and close to control fluid flow.

---

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

Three advantages of using external packing in a pump are:  
1. **Ease of Maintenance:** The packing is accessible from outside, making inspection and replacement simpler.  
2. **Adjustability:** The external packing can be tightened or adjusted without disassembling the pump, allowing precise control over leakage.  
3. **Reduced Downtime:** Since servicing the packing does not require significant pump disassembly, maintenance can be performed faster, minimizing downtime.

---

**Difference Between Flooding Head and Suction Head**

Let  
- $$ h_f $$ denote the flooding head, and  
- $$ h_s $$ denote the suction head.

- **Flooding Head:**  
  This exists when the pump inlet is completely submerged under the liquid. The flooding head is the vertical distance from the pump centerline to the free surface of the liquid when the sump or reservoir floods the suction chamber. It provides a positive pressure feed to the pump and generally helps in reducing the risk of cavitation.

- **Suction Head:**  
  This is the vertical distance from the pump centerline to the free surface of the liquid when the pump is not flooded, i.e., the pump relies on creating a partial vacuum to draw the liquid. It represents the available head (or lift) that the pump must overcome during suction.

**Sketch Illustrating the Difference:**

$$
\begin{array}{c}
\text{Liquid Surface} \
\quad \downarrow\ h_f\quad \text{(Flooding Head)}\[1mm]
\overbrace{\rule{3cm}{0.4pt}}^\text{Pump Inlet (Flooded)}\[1mm]
\qquad\quad \downarrow\ h_s\quad \text{(Suction Head)}\[1mm]
\text{Pump Centerline}
\end{array}
$$

In the flooded condition, the pump inlet is immersed (with a head $$ h_f $$) ensuring a constant supply by gravity. In contrast, if the pump is not flooded, the available head is $$ h_s $$, which is the vertical lift from the free surface to the pump inlet that the pump must create via vacuum.

**4.1: Moving Parts of a Reciprocating Pump** - **Piston:** Moves back and forth in the cylinder. - **Connecting Rod:** Transmits motion from the crankshaft to the piston. - **Valve Assembly:** Controls fluid flow with inlet and outlet valves. --- **4.2: Advantages of a Pump with External Packing** - **Ease of Maintenance:** The packing is easily accessible for inspection and replacement. - **Adjustability:** Allows precise control over leakage by adjusting the packing. - **Reduced Downtime:** Maintenance can be done quickly without major pump disassembly. --- **Difference Between Flooding Head and Suction Head** - **Flooding Head ($$ h_f $$)**: The vertical distance from the pump centerline to the liquid surface when the pump is fully submerged, providing positive pressure. - **Suction Head ($$ h_s $$)**: The vertical distance from the pump centerline to the liquid surface when the pump is not submerged, requiring the pump to create a vacuum to draw the liquid. **Sketch:** $$ \begin{array}{c} \text{Liquid Surface} \ \quad \downarrow\ h_f\quad \text{(Flooding Head)}\[1mm] \overbrace{\rule{3cm}{0.4pt}}^\text{Pump Inlet (Flooded)}\[1mm] \qquad\quad \downarrow\ h_s\quad \text{(Suction Head)}\[1mm] \text{Pump Centerline} \end{array} $$ In the flooded condition, the pump inlet is fully submerged with head $$ h_f $$, ensuring a constant liquid supply. In the suction condition, the pump must create a vacuum to lift the liquid a distance $$ h_s $$.

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