current to pressure converter

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Group No.: 18

Team Members Internal Guide

Darshik Sheth Hetal Chauhan

Meet Patel External Guide Shravan Ranade Pankaj Shah

Vaishal Shah Vipul Shah

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Design, Analysis, and Manufacturing of

Current to pressure converter for

Steam Turbines.

Industrial Defined Project


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Industry Details

Name: Siemens Ltd.

Plant location: G.I.D.C., Maneja

This plant mainly manufactures steam turbines (up to

120 MW) and condensers. It also has a service shop to

meet offsite overhaul/repair requirements.

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AGENDA

Objective of project

Need of control system in Turbines.

Role of CPC in control system.

What is CPC? In brief.

Design Phase

Future Plans

Expected outcomes

References11-10-2014 4


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Objective Of project

To facilitate the localization of the product

and make the product in-house.

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So at different Electrical load, If speed will remain

same then we will get constant frequency.

Initially when steam/gas turbines were developed,

mechanical governors were used. But due to less

efficiency, wear and friction problems now it is

replaced by electronic governors.

If electrical load

increases

Speed of turbine

decreases

To maintain

constant speed

steam flow rate

should increase

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Role of CPC

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What is CPC?

CURRENT TO PRESSURE CONVERTER

Solenoid operated control valve.

As name suggest its main function is to

convert the current signal from the governor

to corresponding pressure signal.

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Simple Line diagram

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Control loop across CPC

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Cross section

of CPC

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So there are two sections in CPC:-

1) Electronic &2) Mechanical

So briefly we can say this is Mechatronics project.

CPC controls servomotor and servomotor controls

steam flow

(Servo word is used when we control big thing by

small thing).

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Design Phase

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Bore diameter


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Topics

Design of Hydraulic portion of CPC Includes:

1) Orifice size

2) Spool diameter

3) Bore diameter

4) Seal selection

5) Gland diameter

6) Gland thickness

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Orifice size calculations

Fundamentals:

Pressure difference and voltage difference analogy

For a given Resistance

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So,

I (Current) Q (Flow) &

V (Voltage) P (Pressure)Pressure = Flow*Resistance

Pressure = Flow*(1/Conductance)

And this Conductance= Cvvalue is known as Flow

coefficient.

In our project after finding out Cv value we are able

to find out minimum orifice size that is required tomeet the specifications.

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Mathematically the flow coefficient can be

expressed as:

where:Cv= Flow coefficient or flow capacity rating of

valve.

F = Q=Rate of flow (US gallons per minute).SG = Specific gravity of fluid (Water = 1).

P = Pressure drop across valve (psi).

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Input parameters

Specific gravity of oil = 0.9

For P A

Q = 24 Lpm at 1 bar pressure difference

For A T

Q = 30 Lpm at 1 bar pressure difference

*Lpm= Liter per minute of oil

1 LPM= 0.264172052 Gpm (Us)

1 Bar= 14.503 Psi

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Cv Values for A & T orifice

Cv = 1.5793 For Aorifice

Cv = 1.9724 For Torifice

Now from this values we can find the orifice size byusing different manufacturers calculator and select .

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Calculator For orifice size

Note: This is a experimentally found value by spirax sarco Valve manufacturer we

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Bore diameter calculation

r2= (7.12/2)2= 39.79511

This area should be maintain inside cylinder including 5mmof spool.

So,

( R2-r2)= 39.79511 here r = 0.25cm spool radii D= 2R= 8.70025 mm

Gland Cylinder

Where, D is the diameter of cylinder ( Bore diameter )

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Oil Seals

The oil seal is anintegral part of any

hydraulic circuit. In CPC,static as well as

dynamic O-rings areused for facilitating leak

proof operation.

Note: The following calculations have been done in accordance to the Parker O-Ring

Handbook.

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Selection of O-Ring

The size of O-Ring is selected on the basis of

following dimensions:

Bore Diameter= 8.7 mm

Spool Diameter= 5 mm

Cross Section of O-Ring= 1.78 mm

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Selection of O-Ring contd..

So, we select the ring 2-009.

According to it, the inside

diameter of the ring is5.280.13

ID=5.28,C/S=1.78

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Material Selection contd..

Various material options are available from the

standard catalogue.

We select Polyurethane due to following reasons

It has high abrasion resistance, low friction

Suitable for high pressure, shock load

Temperature range of -50 to 150 degree Celsius

Shore hardness of 95-105A

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Future Plan

Gland Design

Valve orifice configuration

Spool design(detail engineering)

Force Calculations

Electronic controller of CPC..

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References

Spirax sarco Online calculator

http://www.spiraxsarco.com/resources/calcul

ators/orifice/flow-coefficient-to-orifice-

diameter.asp

Parker Hand book for seal selection

Hydraulic and Pneumatic systems by

S.R. majumdar for understanding concepts.

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The End

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