I have three questions:
1. Why is the control valve size less than line size
2. How we will prepare item code for elements and equipment
3. If all the elements in discharge line of a pump do not fit in less than 1.8 meters, what should we do?

1. Why is the control valve size less than line size
It has to do with with the control valve Cv (Control Volume).


2. How we will prepare item code for elements and equipment?
First, I what to know what is your position of responsibility on the project?
Are you a Piping Designer"
Are you a Piping Material Engineer?
Are you an Equipment Engineer?

Second, What elements?

3. If all the elements in discharge line of a pump do not fit in less than 1.8 meters, what should we do?
Why do you think all of the elements should fit in the first 1.8 meters?
Who told you this?

Jop,
No need for new link I got the handbook via emersions site only.
Thank You
Siddharth Jain

Mr jop
i am a trainee in a company( piping designer).

for 3rd question to access all the valves,instruments.

You wrote:
"for 3rd question to access all the valves,instruments."
I assume you are asking, "What are the considerations or guideline for access for all Valves and Instruments?"

First, there are more than one reason for access it these items. These are operation, maintenance and emergency.
So what should be considered:

Normal Operations:
Instruments - All instruments such as Pressure and Temperature gauges shall be accessible from Grade, a platform or ladder. Control Valve manifolds shall be accessible from grade or platform. Orifice runs may be located in an elevated position but must be accessible from grade via a portable ladder. If located at a higher point the Orifice Flanges and the associated shall be accessible from a platform.

2" (DN 50) valves and smaller operating valves - Accessible from grade, platform or permanent ladder(*).

3" (DN 80) valves and larger operating valves - Shall be located at grade or on a platform (inside the handrail)

Maintenance:
Instruments - Same as Operating

2" (DN 50) valves and smaller hydro-test vent valves - No access requirements

All other valves same as Operating

Emergency:
All valves identified on the P&ID as an Emergency Shut-Down Valve (ESV) shall be motor operated and controlled via a switch (push-button) station at grade and in a location that is a safe distance from any possible hazard.

(*) Accessible from a platform or permanent ladder means that the valve hand wheel or lever shall not be more than "Arms reach" away from the platform handrail or ladder cage.

I hope I understood your question.

Dear Sravan,

Small questions have a lot of wisdom hidden in them.

http://people.clarkson.edu/~wilcox/Design/valvselc.pdf
This link will help you with Control Valves.

Regards,

Hello everyone
on the same topic---
how the type of bypass valve and size of bypass valve is decided for any control station manifold.
I have seen use of both globe and gate valve as bypass.
Why we use a gate valve as it is not a good option for flow regulation.

Thank You
Siddharth Jain

"how the type of bypass valve and size of bypass valve is decided for any control station manifold.
I have seen use of both globe and gate valve as bypass.
Why we use a gate valve as it is not a good option for flow regulation."

Control valve manifold Bypass type: The valve should be a "Throttling" type valve (Globe, Ball, etc.) and shall be consistent with the piping line class material specification for that service.

The size of the bypass valve is normally the same size as the Control so as to replicate the same pressure drop as the Control Valve

Globe or Gate in the bypass: The globe valve should always be used for the bypass valve where globes valves of the proper size are available. When the bypass valve is needed that is larger than what globe valves are made then you must use a gate valve or other line class valve.

Correct a gate valve is not a good valve for flow regulation but when they don't make globe valves that big then you have no choice?