TOTAL CAPABILITIES IN THE PIPELINE · PDF fileRELIEF VALVE SIZING GUIDELINES PRESSURE...

TOTAL CAPABILITIES IN THE PIPELINE INDUSTRY

UTILITY TECHNOLOGIES INTERNATIONAL CORPORATION Cincinnati Columbus West Jefferson

COMMON NATURAL GAS

ENGINEERING PROBLEMS

OGA SEMINAR

DECEMBER 3, 2012

RELIEF VALVE SIZING GUIDELINES

PURPOSE

RULES

PRESSURE LIMITATIONS

REGULATOR MAXIMUM CAPACITY

RELIEF VALVE CAPACITY

RELIEF VALVE VENT PIPINE SIZING

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PURPOSE

Protection against accidental over

pressuring of a pipeline

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192.195 Protection against accidental over pressuring

192.199 Requirements for design of pressure relief and limiting devices

192.201 Required capacity of pressure relieving and limiting stations

192.739 Inspection and testing

192.743 Capacity of relief devises.


Rules of pressure limitations

MAOP ≥ 60psi ..................... MAOP +10%

(or 75% SMYS) which ever is less

MAOP ≥ 12psi < 60psi ......... MAOP + 6psi

MAOP < 12psi .................... MAOP + 50%

LP – prevent unsafe operation of any

appliance

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PRESSURE LIMITATIONS

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MAOP+ Allowable over-pressure build-up

System Pressure

MAOP

Normal Operation

MAOP+ Allowable over-pressure build-up

System Pressure

MAOP

Accidental Operation


REGULATOR MAXIMUM CAPACITY

The regulator capacity to be vented is

maximum capacity based on the maximum

inlet pressure (upstream MAOP) and

maximum outlet pressure

Assume that no flow is going into the

downstream system

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In sizing relief valves assume that no flow is going into the downstream system

Relief valves are sized using:

oThe manufacturer's Capacity tables

o The manufacturer's Flow coefficients for relief valve sizing

oThe manufacturer's Sizing equations

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Required pressure buildup from set point

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SET POINT


Inlet piping Keep it as short as possible

Same size as the relief valve inlet

A full port shut-off valve

Vent piping Keep it as short as possible

Same size as the relief valve outlet or larger

Double the size if longer than 10 feet or

Use vent line sizing equations

NOTE: If relief valve is located inside a building o vent to the outside

10

RELIEF VALVE SIZING

Example

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Relief Valve Sizing Problem - Annual Verification Existing system consists of a single regulator and a relief valve. The system has a volumetric requirement of 2.3 MSCFH. You are responsible for the annual capacity verification of the relief valve. Problem 1: Perform the annual capacity calculation. 1) Is regulator capacity adequate ? 2) Is relief valve capacity adequate ? 3) Correct any discrepancies

RELIEF VALVE SIZING

Example

Determine system parameters

a. Upstream MAOP

b. Downstream MAOP

c. Downstream maximum operating pressure

d. Regulator maximum capacity

1) Use the maximum inlet pressure: That is the MAOP

2) Determine the set point of the relief valve

e. Determine the pressure that will produce the set point plus the

allowable maximum pressure build-up

f. Verify relief valve capacity at the stated conditions

g. Compare the maximum capacity of the regulator to the capacity

of the relief valve

h. Verify that the capacity of the relief valve is greater than that of

the regulator.

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RELIEF VALVE SIZING

Example

Calculate the maximum capacity of the regulator

Select from the 1” Fisher 627 bulletin the 1/4” orifice flow

coefficient Cg = 50 & C1=29.3

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REGULATOR SIZING

Regulator Capacity Calculation

degP

PP

C

3417sinPC

S

1=Q

Inlet

OutletInlet

1Inletg

g

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Inletg PC1.291=Q

Non-Critical (sub sonic) Flow

Critical (sonic) Flow 1.814

P

P

Outlet

Inlet

1.814P

P

Outlet

Inlet

use the Universal Sizing Equation

REGULATOR SIZING


Determine if Pin/ Pout > than 1.814

Calculate regulator capacity use

Equation:

Q = 1.29 x 50 x 39.48

Q = 2,546.4 Cu Ft/hr

Determine relief valve capacity at 7.5 psig set point

Determine MAOP Plus Allowable build-up =15 + 6

Maximum pressure build up at full relief = 21 psig

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Inletg PC1.291=Q

02.248.145

48.1425

RELIEF VALVE SIZING

Relief Valve Capacity Calculation

Determine relief valve capacity using the Fisher 1805

relief valve Figure 3. Capacity Curves

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PR

ES

SU

RE

PS

IG

FLOW MSCFH

RELIEF VALVE SIZING

Example

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RELIEF VALVE SIZING

Example

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RELIEF VALVE SIZING

Example

Compare the capacity of the regulator to the capacity of

the relief valve

Regulator capacity

Q= 2.546 MSCFH

Relief Valve capacity from curves

Q = 5.3 MSCFH

The capacity of the relief valve is greater than that of the

regulator therefore we have adequate capacity for over-

pressure protection of the downstream system

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RELIEF VALVE SIZING

Solution

From the relief valve chart we determine the pressure

build up at the failed regulator capacity is 17.5 psi

The maximum downstream pressure can build up to 21

psig (15 +6)

The17.5 psig pressure build up is less than the 21 psig

allowed

RELIEF VALVE SIZING

23 OGA Seminar Dec 3, 2012

Problem 2: Relief Valve Sizing Problem - Annual Verification Existing system consists of a single regulator and a relief valve. The system has a volumetric requirement of 30 MSCFH. You are responsible for the annual capacity verification of the relief valve.

1) Is regulator capacity adequate ?

2) Is relief valve capacity adequate ?

3) Correct any problems and specify any new

equipment that maybe necessary.

15 MAOP 60 MAOP

45-60 Psig 10-15 Psig

1” Mooney Flowgrid

What is max pressure at full relief? __________

RELIEF VALVE SIZING (Solution)


Problem 2: Relief Valve Sizing Problem - Annual Verification Existing system consists of a single regulator and a relief valve. The system has a volumetric requirement of 30 MSCFH. You are responsible for the annual capacity verification of the relief valve.

1) Is regulator capacity adequate ?

2) Is relief valve capacity adequate ?

3) Correct any problems and specify any new

equipment that maybe necessary.

15 MAOP 60 MAOP

45-60 Psig 10-15 Psig

1” Mooney Flowgrid

What is max pressure at full relief 21 Psig

20 Psig

15 MAOP 60 MAOP

45-60 Psig 10-15 Psig

RELIEF VALVE SIZING

System Parameters


Set up system parameters:

MAOPs

Operating Pressures

Regulator

Select from the 1” Mooney Flowgrid

flow coefficient table

Cg = 450 & C1=34

What is max allowed pressure at full relief? _________

Set Point ? Psig

15 MAOP 60 MAOP

45-60 Psig 10-15 Psig


System Parameters


What is max allowed pressure at full relief? _________

Set up system parameters:

MAOPs

Operating Pressures

Regulator

Select from the 1” Mooney Flowgrid

flow coefficient table

Cg = 450 & C1=34

Set Point 20 Psig

RELIEF VALVE SIZING

Flow Equations

(Determine which equation to use)


degP

PP

C

3417sinPC

S

1=Q

Inlet

OutletInlet

1Inletg

g

Inletg PC1.291=Q



P

P

Outlet

Inlet

1.814P

P

Outlet

Inlet

Use the Universal Sizing Equation


Flow Equations


degP

PP

C

3417sinPC

S

1=Q

Inlet

OutletInlet

1Inletg

g

Inletg PC1.291=Q



P

P

Outlet

Inlet

1.814P

P

Outlet

Inlet

Use the Universal Sizing Equation

USE THIS

EQUATION

Pin = (60+14.48) Pout = (15+14.48)

= 2.5 > 1.814

1” Mooney FlowGrid Pressure Regulator

2” Mooney FlowGrid Relief Valve

Reference materials (Solution)

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for relief sizing



Calculate regulator capacity use

Equation:

Q = 1.29 x 450/1000 x 74.48

Q = 43.2 MSCFH

Determine relief valve capacity of a 2” Mooney Flowgrid at maximum pressure of 21 psig

Inletg PC1.291=Q

5.248.1415

48.1460


Calculate regulator capacity of a

2” Mooney Relief valve

Equation:

Q = 1.29 x 1130/1000 x 34.48

Q = 50.3 MSCFH

50.3 MSCFH is the max capacity of the relief valve at 20 psig set point

Note: The Mooney pilot only requires a pressure build up of only 0.5 psig above set point for max capacity


Relief valve Capacity Calculation


Inletg PC1.291=Q

38.248.14

48.1420


Relief Valve Capacity Verification

Compare the capacity of the regulator to the capacity of

the relief valve

Regulator capacity

Q= 43.2 MSCFH

Relief Valve capacity from curves

Q = 50.3 MSCFH

The capacity of the relief valve is greater than that of the

regulator therefore we have adequate capacity for over-

pressure protection of the downstream system


TOTAL CAPABILITIES IN THE PIPELINE · PDF fileRELIEF VALVE SIZING GUIDELINES PRESSURE...

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