Analysis of Pipeline Valve Functions

Valves are essential components in pipeline systems, controlling the flow, direction, pressure, and release of fluids. Different types of valves serve specific purposes. This question asks us to identify the pair where the valve type is incorrectly matched with its function.

Examining Each Pipeline Valve Option

Let's analyze each option provided:

1. Scour valve – To drain or empty the pipe line section.

   A scour valve, also known as a drain valve, is typically located at low points in a pipeline. Its primary function is to drain the water or fluid from a section of the pipe, allowing for maintenance, cleaning, or emptying for other reasons. This description is correct.

2. Check valve – To check the water flow in pipes, in all directions.

   A check valve, also known as a non-return valve, is designed to allow fluid flow in only one direction. It automatically prevents backflow, meaning it stops the fluid from flowing backward in the pipe. Therefore, stating that it checks flow in 'all directions' is incorrect. A check valve restricts flow, but only in the reverse direction, permitting flow in the forward direction.

3. Surge arrestor – Control of water hammer in pipe lines.

   A surge arrestor, or surge suppressor, is a device installed in pipelines to absorb or dissipate the energy caused by sudden changes in flow velocity, which can lead to pressure surges known as water hammer. By mitigating these pressure fluctuations, surge arrestors protect the pipeline and connected equipment from damage. This description is correct.

4. Air valve – To release the accumulated air in pipelines.

   Air can accumulate in pipelines, especially at high points, causing blockages and operational problems. An air valve is installed to automatically release trapped air from the system and, in some cases, to allow air to enter the pipe when the pressure drops below atmospheric pressure, preventing vacuum conditions. This description is correct.

Identifying the Incorrectly Matched Pair

Based on the analysis of each option:

• Scour valve function: Correct.
• Check valve function: Incorrect.
• Surge arrestor function: Correct.
• Air valve function: Correct.

The pair that is INCORRECTLY matched is the Check valve paired with the function "To check the water flow in pipes, in all directions." Check valves only prevent flow in the reverse direction, not in all directions.

Revision Table: Common Pipeline Valves

Additional Information on Pipeline Valves and Water Hammer

Understanding the function of different valves is crucial in designing and operating pipeline systems efficiently and safely. For instance, water hammer, mentioned in relation to surge arrestors, is a phenomenon caused by the sudden stoppage or change in speed of fluid flow. This creates a pressure wave that travels back and forth in the pipe, potentially causing significant damage. Surge arrestors or other measures like surge tanks are used to manage this effect.

Different types of check valves exist, such as swing check valves, lift check valves, and dual plate check valves, but their fundamental principle remains preventing reverse flow. Similarly, air valves can be single orifice, double orifice, or kinetic types, each suited for different conditions of air accumulation and release.