spring loaded safety relief valves_design

7/27/2019 Spring Loaded Safety Relief Valves_Design

1/50

Disclosure to Promote the Right To Information

Whereas the Parliament of India has set out to provide a practical regime of right to

information for citizens to secure access to information under the control of public authorities,in order to promote transparency and accountability in the working of every public authority,

and whereas the attached publication of the Bureau of Indian Standards is of particular interest

to the public, particularly disadvantaged communities and those engaged in the pursuit of

education and knowledge, the attached public safety standard is made available to promote the

timely dissemination of this information in an accurate manner to the public.

!"#$% '(%)

!"# $ %& #' (")* &" +#,-.Satyanarayan Gangaram Pitroda

Invent a New India Using Knowledge

/0)"1 &2 324 #' 5 *)6Jawaharlal Nehru

Step Out From the Old to the New

7"#1&"8+9&"), 7:1&"8+9&")Mazdoor Kisan Shakti Sangathan

The Right to Information, The Right to Live

!"# %& ;


2/50


3/50


4/50

IS 12992 Part 1)

:

1993

wTiif9 WIT

I ndi avz t andard

SAFETY RELIEF VALVES - SPRING LOADED -

SPECIFICATION

PART 1 DESIGN

UDC 621.646~28

0 BIS 1993

BUREAU OF INDIAN STANDARDS

MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

( Reaffirmed 2006 )


5/50

Chemical Engineering Plants and Related Equipment Sectional Committee, HMD 17

FOREWORD

This Indian Standard ( Part 1 ) was adopted by the Bureau of Indian Standards after the draft finalized

by the Chemical Engineering Plants and Related Equipment Sectional Committee, had been approved

by the Heavy Mechanical Engineering Division Council.

In the formulation of this standard assistance has been derived from API 526 : 1984 Flanged steel

safety relief valves, issued by the American Petroleum Institute.

This standard is being issued in two parts, Part 1 covers design and Part 2 testing.

For the purpose of deciding whether a particular requirement of this standard is complied with, the

final value, observed or calculated, expressing the result of a test or analysis, shall be rounded off in

accordance with IS 2 : 1960 Rules for rounding off numerical values (

revised .

The number of signs_

cant places retained in the rounded off value should be the same as that of the specified value in this

standard.


6/50

IS 12992 ( Part 1)

:

1993

I ndian St andard

SAFETYRELIEFVALVES SPRINGLOADED

SPECIFICATION

PART

1

DESIGN

1 SCOPE

1.1 This standard covers the specification for flanged

steel spring loaded safety relief valves. Basic require-

ments are given for:

a) orifice designation and area;

b) valve size and rating, inlet and outlet;

c) materials, body and spring;

d) pressure-temperature limits; and

e) centre-to-face dimensions, inlet and outlet.

1.2 The valves regulated by IBR (Indian Boiler

Regulations) are

excluded from the scope of this

standard.

1.3 For ihe convenience of the purchaser, a sample

specification sheet is given in Annex A.

1.4 Name plate nomenclature and requirements for

stamping are detailed in Annex B.

1.5 The purchaser is primarily responsible for:

a) Selection of type of valve and desired pressure-

temperature ratings; and

b) Specification of materials which will satisfac-

torily resist corrosion from the process fluid or

environmental conditions.

1.6 Whenever the information included on the

purchasers specification sheet or purchase order con-

flicts with the provisions of this standard, the

purchasers specification sheet or purchase order shall

govern. The manufacturer shall call such conflicting

requirements to the attention of the purchaser whenever

possible.

2 REFERENCES

IS No.

2825 :

1969

28.56 : 1979

3038 : 1983

3233 : 1965

4899 : 1976

Tide

Code of unfired pressure vessels

Carbon steel castings for pressure

containing parts suitable for high

temperature

service (fusion

welding

quality) ( second

revision )

Alloy steel castings for pressure

containing parts suitable for high

temperature

service

( second revision )

Glossary of terms for safety valves

and their parts

Ferritic steel castings for use

at low temperatures (first

revision

7806

:

1975 Ferritic and austenitic steel cast-

ings for high temperature service

12992

Spring loaded safety relief valves :

(

Part 2) :1990

Part 2 Testing

13159

Steel pipe flanges and flanged fit-

(Part 1) :1993

tings : Part 1 Dimensions

3 DEFINITiONS

For definitions ofvarious terms used in connectionwith

spring loaded pressure relief valves, refer to IS 3233 :

1965.

4 DESIGN

4.1 General

Safety and safety reliefvalves discussed in this standard

shall be designed and manufactured in accordance with

the applicable requirements of IS 2825 : 1969.

4.2 Determination of Orifice Area

The required orifice area shall be determined in ac-

cordance with Annex C and Annex D. The standard

orifice areas and the corresponding letter designa-

tions are :

Orifice Area

Orifice

Area

64 mm

69 mm

D 71 L 1841

E 126

M

2323

F 198

N

2800

G 325

P

4116

H

506

Q

7129

J 830

R

10323

K

1186

T

16774

4.3 Valve Selection

For valves described in this standard, inlet and outlet

flange sizes and pressure-temperature ratings shall con-

form to the data in Tables 1 to 14. Inlet pressure limits

are governed by inlet flange pressure limits or by

manufacturer.s spring design limits, whichever is

smaller. Outlet pressure limits are determined by valve

design.

4.4 Dimensions

Centre-to-face dimensions shall be in accordance with

Tables 1 to 34 with tolerances as follows:

Val ve n let Size

Tolerance

Up to and including 100 mm

* 1.6 mm

Above 100 mm

rt 3.2 mm

1


7/50

IS 12992 ( Part 1)

:

1993

Flange facings and dimensicns shall be in accordance

with IS 13159 (*Part 1)

:

1993, the inlet flange may be

modified to increase the height of the raised face.

43

Lifting Levers

Plain lifting levers shall be provided on all safety valves

for steam or air service and on safety relief valves when

designated on the purchasers specification sheet; pack-

ed lifting levers shall be provided on hot water service

and wheri specified by purchaser. Lifting levers shall be

capable of relea&ng the seating force on the disc when

the valve is subjected to a pressure of at least 75 percent

of the set pressure of the valve. All safety relief valves

shall be furnished with a threaded cap over the spring

adjusting screw unless otherwise stated.

45.1 Means shall be provided in the design of all valves

for sealing all adjustments which can be made without

disassembly of the valve before or after it is installed.

4.6 Special Construction

Features

Special construction features shall be provided as

agreed upon by the manufacturer and the purchaser.

5

MArnRL4L

5.1 General

For special corrosion problems and applications

beyond the pressure temperature limits of this stand-

ard, constructioh materials shall be those agreed upon

by the manufacturer and the purchaser.

5.2 Body

and Spring

The

body and spring material shall be in accordance

with Tables 1 through 14 for the required temperature

range. The valve body material shall be equivalent to,

or better @an, the following types and grades:

Cast carbon Steel

IS 2856, Gr 2

Cast carbon molybdenum steel IS 3038, Gr 4

Cast 3; percent nickel steel

IS 4899, Gr 7

Cast austenitic steel

IS 7806, Gr 3 or 5

5.3

Inter& Parts

Materials for the internal parts of the valve shall be in

accordance with the manufacturers standards for

temperature and service and indicated on the

purchasers specification sheet.

6 INSPECTION AND SHOP TESTS

6.1 Inspection

The purchaser reserves the right to witness the shop

tests and inspect valves in the manufacturers plant

according to the extent specified on the purchase order.

6.1.1. Shell

Test.

The

primary pressure parts ofeach valve exceeding DN

25 or 21 bar set pressure where the materials used are

either cast or welded shall be tested at a pressure of at

least 1.5 times the design pressure of the parts. These

tests shall be conducted after all machining operations

have been completed. The secondary pressure zone of

each closed bonnet valve exceeding DN 25 inlet size

wheri such valves are designed for discharge to a closed

system shall b$ tested with air or other gas at a pressure

of at least 2 bar. There shall be no visible sign of

leakage.

6.2

Set P&we Test

All safety and safety relief valves shall be set and

adjusted to the specified set pressure in accordance with

IS 2825

:

1969, the manufacturers standard practice as

published, or as designated by the purchaser. The set

pressure adjustment shall be sealed when specified.

6.3

Seat Leakage Test

Safety and safety relief valves shall be subjected

to a seat leakage test in accordance with IS 12992

(Part 2 )

:

1990.

7 MARKING

7.1 On

the Body of the Safety Valve

The

following minimum information shall be marked

ou the body of all safety valves. Marking on the body

may be integral with the body or on a plate

securely

fixed to the body. When a plate is used, it shall be

separate and distinct from the identification plate

referred elsewhere in this standard:

a>

b)

4

4

The inlet and outlet nominal size, for example

PN;

The material designation of the body;

The nianufacturers name and/or trade-mark;

and

An

arrow showing the direction of flow where

the inlet and outlet connections have the same

dimensions or the same pressure rating.

7.2 Identification Plate

The following minimum information, stating units,

shall be on ad identificatiou plate securely fixed to the

safety valve:

a) The limiting operating temperature(s) (in C)

for which the valve has been designed;

b) The set pressure in MPa;

c) The number of this standard;

d) Manufacturers type reference;

e) Coefficient or discharge or certified discharge

capacity of reference fluid, kg/b;

f) Flow area in square centimetres; and

g) Lift in millimetres and corresponding over

pressure expressed as a percentage.

7.3 Name Plate

Each valve shall have a corrosion-resistant name plate

permaneutly attached to the body or bonnet. The name

plate shall be stamped with the data specified in

Annex B.

7.4

Tagging

Each valve shall be stamped with the valve number or

other identificatiou data as specified on the purchase

order. This data may be stamped ou the name plate or

on a separate corrosion-resistant tag that is permanently

attached to the valve.


8/50

IS 12992 ( Part 1) : 1993

8 SHIPMENT

b) Threaded opeklgs shall be plugged with a

8.1 Preparation for Shipment

suitable protective device. Temporary plugs

should be readily distinguishable from per-

a) After test and inspection, all exterior sur-

manent metal plugs.

faces except flange facings shall be painted.

Corrosion-resistant materials need not be

c) To prevent damage to the faces during shipment

and foreign material from entering, inlet and

painted.

outlet flanges shall be protected.


9/50

Table 1 Flanged Steel Safety Relief Valves - D Orifiie

(

Clauses

4.3

and

4.4 )

P

Materials V W ~omioal

EYange Mdmum Pressure &ding Bar

Cetlll+tO-F8_

Sizes Rating(Clas3)

Conventional Balanced Bellows and Balanced Piston Valves

Conven- Balanced

Dim&

tiOMl

Below

(mm)

Valves

Valves

Inlet by Inlet

Outlet

Body Spring

Orifice by

Inlet Outlet - 267oc -60C to - 29C to - 28OC o

232C 427

540C 38C

38OC Inlet outlet

outlet

to - 102C - 101C - 59OC 38C

Temperature Range - 28C to 23ZC

25D50 150 150 20 13 20 105 114

25D50 300 150 20 20 20 105 114

Cast

Carbon 25D50 300 150 52 43 20 105 114

carbon

steel steel 25D50 600 150 104 87 20 105 114

4OD50 900 ux) 156 130 42 105 140

40D50 1500 300 266 217 42 105 140

4oD65 2500 300 422 361 52 140 165

. .

Cast

carbon

steel

High

temper-

ature

alloy

steel

25D50 150 150

25D50 300 150

25D50 300 150

25D50 600 150

4OD50 900 300

4OD50 1500 300

4OD65 2500 300

233 to 42PC

TmpFaturr Range

13

- 20

43

87

130

217

361

Temperature Range 428C te 540

* .

6 20 ios 114

20 20 105 114

29 20 - 105 114

58 20 105 114

87 42 105 140

145 42 105 140

241 52 - 140 165

Cast

carbon

molyb-

denum

steel

High 23D50 300 150 36 16 20 105 114

temper-

25D50 600 150 71 31 20 105 114

ature

40D50 YOO 300 107 47 52 105 140

alloy

. .

steel 4OD50 1500 300 179 78 52 105 140

40D65 2500 300 297 131 52 140 165


10/50


11/50

Materials

Valve

Sizes

Table 2 Flanged Steel Safety Relief Valves - E Or&e

t:

( Clauses 4.3 nd 4.4 )

G

z

NominallFlange

Maximum Pressure Rating Bar

Ceotr&o-Face

Rating ( C&s )


Convett-

Balanced

Dimensions

tionaI

BdOW

64

Body

Valves

Valves

Inlet by

Inlet

Outlet

Spring

Orifice by

Inlet

Outlet

- 267C

-60C to

- 29OC to - zw to

232C

427C

540C 38C 38C

Inlet Outlet

outlet

to - 102C

- 101C

- 59OC 38OC

h

2

3

c

V

. .

c

s

Temperature Ram : - 2@C to 232%

I

20

105 114

20 105 114

20

105

114

20

105

114

42

105

140

42 105 140

52 140 165

20

13

20

20

52 43

104 87

156 130

260

217

422

361

2SE 50 150

150

25E30 300 150

25E50

300

150

25E50 600 150

4OE50

900 300

4Ol30 1500

300

4OE65

2500

300

Cast

carbon

steel

Carbon

steel

Temperature Range 233C to 427C

6

20

29

58

87

145

241

-

I

105

114

105 114

105

114

105

114

i

105

140

105

140

140 165

20

20

20

20

42

42

52

Temperature Range 428OC to 540%

I +

Cast

carbon

molyb-

denum

Steel

300 150

660 150

900 300

1500 300

2500 300

36 16 20 105 114

71

31

20

105

114

107

41

52 105 140

179

78

52 105 140

297

131

52 140

165

High 2.X50

temper-

2SE50

ature

alloy

4oF.50

steel

4OE50

4OE65


12/50


13/50


14/50

W

Temperature Rauge -29C to -59C

4OF50 150 15g u) 20 16 124 121

Cast

4OF50 300 150 20 20 16 124 121

3;

Carbon

4OF50 300 150 52 .- 20 16 124 152

percent steel

4OF50 600 150 104

nickel

20 16 124 152

steel 4OF65 900 300 156 52 35 124 152

4OF65 1500 300 260 - 52 35 124 152

4OF65 2500 300 352 52 35 140

165

Temperature Range -60C to - 101C

4OF.50 150 150 ?9. 20 16

124 121

Cast

4OF50 300 150 19

1

20

16 124

3;

121

Auste- ,4OF50 300 150 51

-

itic

.

20 16 124

.152

percent

steel

4OF50 600 150 101

ickel

20

16 124 152

steel

4OF65

I I :z

, ;;i, i, , if, , ] r, , ;; ] ;;, ;i, if

Temperature Range - 102C to - 267

4OF.50 150 150 19 20 16

124 121

cast

4OF.50 300 150 19

20 16 124 121

autenit- Auste- 4OF50 300 150 43

its

nitic

2n 16 124 152

steel

steel 4OF50 600 150 87 20 16 124 152

4OF65 900 300 130

52 35 124 152

4OF65 1500 300 155

52 35 124 152

4OF65 2500 300 239

52 35 140 165


15/50


16/50


17/50


18/50

_~...r____~_.-____

. - __ -. -

4OH80 150 1.50

20

20 16 130 124

Cast

3; 4OH80 300 150

20

20 16 130 124

arbon

50H80 300 150

52 .-

20 16 130 124

percent

steel

nickal SOH80 600 150

104

20 16 1.54 162

steel 50H80 900 150

1.56 .

20 16 154 162

I ,

5OH80

,

1500, 300,

- I - I 193 ( - I - I - I

- I 52 , 29 , 154 ( 162

Temperature Range - 60 to - 101C

4OH80 150 150

19

20 16 130 124

Cast

3; Auteni- 4oH80 3M) 150

19

20 16 130 124

tic 50H80 300 150

51

20 16 130 124

percent

nickel steel 50H80 600 150

101

20 16 154 162

steel

50H80 900 150

104

20 16 154 162

1

5OH80

1

1500

1

3m

I

- I 112 l -I -I -I -I

-I 52 I 29 I

154

1

162

Temperature Range -1OtC to -2@C

4OH80 150 150

19

20 16 130

124

Cast

Auste-

4oH80 300 150

19

20 16 130 124

austen-

nitic 5OH80 300 150

43 i

20 16

itic

130 124

steel

steel

5oH80 600 150

87

20 16 154 162

50H80 900. 150 104

-

20 16 154 162

5OH80 1500 300 112

52 29 154 162


19/50

Table 6 Flanged Steel Safety Relief Valves - J Orifice

( czuuses 4.3 and 4:4 )

Nontioal Flange

Rating ( Class )

MaxImum Pressure Rating Bar

Conventional Balanced Bellows and EIaIanced Piston Valves

Conven- BaIanced

tionaI

Below

Valves

Valves

Css~tre-to-Face

DimCnSioOS

(mm)

Inlet

Inlet

Outlet

Outlet - 26pC -60oC to

- 29OC to -28Yto

232%

427oc

54ooc 38OC

38OC

InIet

Outkt

to - 1wc

- 10lC

- 59C 38OC

1

1

-WCtC

12C

20

13

20 20

52 43

104 87

156 130

190

190

-&Ire

Ral

.-

6

20

29

58

87

145

High 65JlOO

300 150

36

temper-

65JlOO 600 150 71

ature

alloy 655100

900 150

107

steel 8OJlOO

1500 300

143

5OJ80

150

5OJ80

300

65JlOO

300

i

65Jloo

600

805100

900

8OJloo

1500

5OJ80

5OJ80

653100

653100

65JlOO

655100

1.50

300

308

600

900

1500

I

137

137

137

156

184

184

124

124

143

171

181

181

20

20

20

20

20

42

20

20

30

20

20

42

16

16

16

16

16

16

16

16

16

16

16

16

150

150

150

150

150

300

150

150

150

150

150

300

Cast

carbon

steel

Carbon

steel

-I-

I

I

Temperatuure Rat c 233C to 427%

124

124

143

171

181

181

13

20

43

87

130

190

High

temper-

ature

alloy

stqel

cast

C@OIl

steel


Cast

carbon

Molyb-

denum

steel


20/50

Temperature Range -29OC to -59C

Cast

3+

percent

nickel

steel

Carbon

steel

5OJ80 150 150

20

20 16 137 124

5oJ80 300 150

20

20 16 137 124

655100 300 150

-

52

20 16 I37 1 43

655100 600 150

104

20 16 156 171

8OJloO 900 150

104 2

20 16

184 181

Cast

3;

percent

nickel

steel

, 8OJloO , 1500, 300, -,

-, -, 190 ,

-

I

-

I -

I 42 I 16 , 184 , 181

Temperature Range -6OC to -101C

5oJ80

150 150

19

20 16 137 124

Auste- 5oJ80 300 150

19

20 16 137 124

nitic

655100

300 150

35

20 16 137 143

steel 655100 600 150

44

20 16 156 171

8OJlOO 900 150

56

20

16 184 181

, 8CUlOLI , 1500, 300, - I

56 I - I - I - I - I -

I 42 I 16 1 184 I 181

Temperature Range -102C to -267?Z

Cast

austen-

itic

steel

50580 150 150 19

20 16

137 124

Auste-

50580 3cNl 150 19

20 16 137 124

nitic

655100 300 150 36

20 16

137

143

steel 65JlOO

,

600 150 44

- .-.

20 16 156 171,

8OJlOO 900 150 56

20 16

184 181

8OJlOO 1500 300 56

-

42 16 184

181


21/50

Table 7 Flanged Steel Safety Relief Valves - K Oritice

( Clauses 4.3 and 4.4 )

Conventional Balanced Bellows an d Balanced Piston Valves

Temperature Range -WC to 232C

0KlCHII 150 150 20 13 20 11 156 162

Cast

80Klal 300 150 20 20 - 20 11 156 162

carbon

Carbon

steel

8OKlcQ 300 150 52 43 20 11 156 162

steel

80K100 600 150 104 87 20

14 184 181

80K150 900 150 156 130 20 14 198 216

80K150 1500 300 156 156 42 14 197 216

I

Temperature Ranee 233O o 427C

1 80KlOO

High

80KlOO

temper-

ature

80KlOO

alloy

steel

80KlOO

80K150

80K150

150 150

13 6

20

11 156

162

300 150

20 20

20

11 156

162

300

150 43

29 20

11 156

162

600

150 87 58

20

14 184

181

900

150 130

87 20

14 198

216

1500 300 156 145 42

14 197

216

300

600

900

1500

150.

150

T

50

300

Temperature Range 428OC to HO%

156

156

184

197

162

162

181.

216


22/50


23/50


24/50


25/50


26/50

e -29OC toern

52

T IIIDW&II-C RN

Cast

3;

percent

nickel

steel

cast

3;

percent

nickel

steel

I

:

178

178

lOOM150

lOOMl5P

lOOM150

lOOM150

150

300

300

600

150

300

300

600

150

150

150

150

150

150

150

150

150

150

150

150

Carbon

steel

178 184

-T-

78

184

9

42 42

1OOM150

Austen-

lOOM150

itic

steel

.

lOOM150

lOOM150

20 . 6

20 6

20 _ 11

20 11

\

178 184

178

I

203

TemperatureRange -102C o -267C

lOOM150

150 19

19

37

42

20

20

20

20

cast

austen-

itic

steel

Auste-

loOM150

300

IlitiC

steel lOOMl50

300

lOOMl50

600

.


27/50


28/50


29/50

Table 11 Flanged Steel Safety Relief Valves - P Orifiie

( czauses 4.3 and 414 )

Ccntrc-to-Faa

Dimensions

(mm)

Nominal Flange


atekials Valve

sizes

Rating ( class )

Conventional Balanced Bellows and Balanced Piston VaIves

Qaven- Balanced

IionaI

Below

Valves

Valves

Ti

tisy Inlet

1

Outlet t;:zCI lyzO;

1 -_29Jc1 1 - zto 1

232C 1 427C 1 540C

38Cou~3SoC Inlet

1

Outlet

Temperature Range -28C to 232C

Cast

carbon

Carbml

steel steel

lOOP150 150 150 20 13 20 6 181 229

.

OOPl50 300 150

-

20 20 20 6 181 229

looP150 300 150 37 37 - 20 11 225 254

lOOP150 600 150 70 70 .- 20 11 225 254


High

150

150

150

150

150

20

20

20

20

20

13 6

20 20

37

29

70

58

70 70

lOOP150 150

100P150

,300

looPl50 300

lOOP150 600

h00P150 900

181

229

181

229

225 254

225

254

225

254

temper-

atme

alloy

steel

cast

carbon

steel


1

cast

High

carbon

temper-

molyb-

ature

denum

alloy

steel

steel

lOOP150

lcOP150

~lOOP150

36

70

70

254

254

254

Temperature Range -29C to -59C

150 20 .- 20 6

150 20 20 6

150 37 - 20 11

150 - 70 20 11

150

300

L

00

cast

1

lOoP150

lalP150

looP150

lOoP150

3:

Carbon.

steel

L

percent

nickel

St4


30/50


31/50

lable 12 Flanged Steel Safety Relief Valves - Q Orifice

( Clauses 4.3 and 4.4 )

-

Materials

Valve

Nom naNlange


Ckutre-to-Face

Sizes

Rating ( Class )


Conven-

Balanced

Dimensions

tional Below

(mm>

Valves Valves

Ir?et by

Inlet

Outlet

Body

Spring

Orifice by

outlet

Inlet

Outlet

- 26% -60C to

- 29C to - 28=C o

540C 38T

to - 102T

- 101C - 59C 38OC

Temperature Range -28C to

232C

15OQ200

150 1.50

12

12

8 5 240

241

Cast

rrbon

steel

Carbon

steel

15oQ2Oo 300 150 12 12 -

.

8 5 240 241

15oQ200

300 150

21

21

8 8 240 241

15oQ200

600 150

42

42

. 8 8 240

241

Temperature Range

233C

to

427?Z

1500200

150 150

12 6

8 5

240

241

High

Cast temper- 15oQ200

300 150

12 12

8 5 240

241

nrboo ature

steei alloy 15ocEoo

300 150

21 21

8 8 240

241

steel

15OQ200

600 150

42 42

8 8

240

241

Temperature Rauge 428% to 544YC

Cast High 15OQ200

300 150

12 12

8 8 240

241

arbon temper-

nolyb-

ature

lenum

15oQ200

600

alloy

150

42 31

8 8 240

241

steel

steel

c


32/50


33/50


34/50


35/50


36/50


37/50


38/50

C:ap

Screwed/Bolted

Lever Plain/Packed

GAG

Yes/No

Screwed/Bolted

Plain/Packed

Yes/No

Screwed/Bolted

Plain/Packed

Yes/No

Screwed/Bolted

Plain/Packed

Yes/No

28 2 Others

I I

29

30

31

32

33

34

35

36

37

41

42

43

Body

Disc

Nozzle

Spindle

Resilient Seat Seal

Guide

47 q

48

Spring

Bonnet

49 Bellows

50

51

Code

Fire

Calculated area, cm2

Selected area, cm2

Orifice letter

Manufacturers model No.

Valve capacity

Internal valve code

Malve rated capacity

Size Inlet/outlet

Screwed socket

Type facing

52 . Inspection agency

53 g Form of certificate

E

54

Mounting details D. No.


39/50

IS 12992 (Part 1) : 1993

ANNEX B

(Clause 1.4)

SAFETY RELIEF VALVE NAMEPLATE NOMENCLATURE

Nomenclature

Size

Type, style,model or

figure No.

Orifice

Capacity at x percent

overpressure

Serial No. or Shop NO.

Set pressure bar

Back pressure bar

Cold differential test

pressure bar

Description

Nominal pipe size,

inlet by outlet

Manufacturers desig-

nation

Valve orifice size, tan-

dardized letter desig-

nation

kg/h of saturated

steam, normal cubic

metre per hour of air or

litres per minute of

water at 21C

Manufacturers iden-

tification number

Valve inlet pressure at

which the pressure

relief valve is

adjusted to open

under service condi-

tions (see Note)

Constant (Example: 7

bar) Variable

(Example

: 0

to

7 Bar)

Valve inlet opeing (see

below) pressure on an

air test stand at am-

bient temperature

against atmospheric

back pressure. Cold

differential test pres-

sure

includes

ap-

plicable temperature

correction.

Example 1 Conventional Valve

Set pressure bar 14

Back pressure bar Atmoshperic (or

zero)

Temperature, deg C

200

Cold differential test pressure, 14 + manufacturers

bar

recommended

temperature correc-

tion

Example 2 - Balanced Bellows Valve

Set pressure, bar

14

Back pressure, bar

3.5 or 0 to 3.5

Temperature, deg C 200

Cold differential test pressure, 14 t manufacturers

bar recommended

temperature correc-

tion

Example 3 -

Conventional Valve

Set pressure, bar 14

Back pressure, bar 3.5

Temperature, deg C 200

Cold differential test pressure, 10.5 t manufacturers

bar

recommended

temperature correc-

tion

NOTE-

Popping pressure on vapours and gases -

When constant back pressure is present on conventional

valves:

Set pressure = Differential test pressure + Back pressure

(Depending upon the service fluid temperature, an addi-

tional correction factor may be required to obtain thecold

differential test pressure for adjusting the valve on the test

stand.)


40/50

IS 12992 (Part I )

:

1993

ANNEX C

(Clause 4.2)

DETERMINATION OF ORIFICE AREA

Kb =

Capacity correction factor due to back pres-

sure[constant or variable]. This can be obtained

horn Fig. 2 which is applied to balanced bellows

valves. For conventional safety reliefvalves& = 1.

Molecular weight of the gas or vapour. Various

handbooks carry tables of molecular weights of

materials,but the composition ofthe

lowing

gas

or vapour is seldom the same as that listed in the

tables. This value should be obtained from the

process data.

a) For Vapour

A = CKP,K,,B m

.

(1)

M=

b) For Sat Steam

A=

W

51.45 P,KK , B

. (2)

For P c 105.5. Bar,

Kc =

1

For P 2 105.5 Bar,

ii =2.7103P-1000 T =

3.2592P- 1061

c) For Superheated Steam

z =

W

A=51.45P,KKcKbKshB

d) For Liquid

P=

A=

v?T

v,

84.09K 41.25P - Pb K, K, Kp

. (3)

Pb =

G =

[ 25% Over Pressure

]

where

Ksh =

A =

w=

c =

K=

NOTE - For liquid service ifK is unknown, a conserva-

tive value of 0.62 is recommended.

VI. =

P, =

B =

Upstream relieving pressure, in bars. This is the

k-=

set pressure plus the allowable overpressure

plus the atmospheric pressure in bar.

Capacity correction factor due to constant back

pressure. This can be obtained from Fig. 1 which

applies to conventional safety relief valves.

Required effective discharge area of the valve

in square centimetres. This is a nominal or corn-

puted area of flow through a pressure-relief

K, =

valve, differing from the actual discharge area,

for use in recognized flow formulae to deter-

mine the capacity of a pressure relief valve.

(see 4.2 for values).

Required flow through valve, in kilograms per

hour.

K, =

Coefficient determined by ratio of specific heats

of the gas or vapour at standard conditions. This

can be obtained from Table 15.

Effective coefficient of discharge for use in

Kp =

fonnula (1) and for formula (2) value assigned

by manufacturer.

Absolute temperature of the inlet vapour, in

degrees centigrade t 273.

Compressibility factor for the deviation of the

actual gas from A perfect gas, a ratio evaluated

at inlet conditions.

Set pressure at which relief valve is to begin

opening, in bar.

Back pressure, in bar.

Specific gravity of the liquid at the flowing

temperature referred to water = 1.00 at 21C.

Superheat correction factor. This can be

obtained from Table 16.

Capacity correction factor due to back pressure.

If the back pressure is atmospheric, the factor

can be disregarded, or Kw = 1.00 conventional

valves in back pressure service require no spe-

cial correction

Kw =

1.00 . Balanced bellows

valves in back pressure service will require the

correction factor as determined from Fig. 3.

Capacity correction factor due to viscosity. For

most applications, viscosity may not be sig-

nificant, in which case K, = 1.00.

Capacity correction factor due to over pressure.

k, ny relief valves in liquid service are sized on

the basis of 25 percent over pressure, in which

case Kp = 1.00. The factor for other percentages

of overpressure can be obtained from Fig. 4.

Liquid discharge capacity , I/m.

C&, the ratio ofspecitic heats of any ideal gas

or the ratio of specific heats of a diatomic acutal

gas that expands in accordance with the perfect

gas laws, values of

K

can be determined from

the properties of gases as presented in any

acceptable reference work.


41/50

IS 12992 ( Part 1)

:

1993

0.6

n

I1 I I I

0 10 20 30 40 50 60 70 60 90

100

% ABSOLUTE BACK PRESSURE = BACK PRESSRE ber

SET PRESSlJRE.OVERPRESSURE,bar

* 100

5

YxlOO

x amp l e

Set pressure [MAWP] =7bar

Superimposed back pressure = 5 bar

Spring set =2bar

Built up back pressure = 0.7 bar

Percent absolute back pressure = +$$+ (loo) = 77.1 percent

Follow dotted line 8 = 0.89 [From curve]

Capacity with back pressure = (0.89) (Rated capacity without back pressure)

NOTE - This chart is typical and suitable for use only when the make of valve or the actual critical flow pressure point for the vapour

or gas is unknown; otherwise, the valve manufacturer should be consulted for specific data.

FIG.1 CONSTANTACK-PRESSUREIZING ACWR FORCONVENTIONAL

SAFER RELIEFALVESVAPOURSNDGASESONLY)

Table 15 Valves of Co-eftkient C

k :

C

1.00

234.3

1.02

236.7

1.04 238.3

1.06

239.9

1.08

241.4

1.10

243.8

1.12

245.4

1.14

246.9

k c

k

C

c

1.32 259.5 1.48

270.4

1.34 260.2

1so

271.2

1.36 261.8

1.52

272.1

1.38 263.4

1.54

274.3

1.40 264.9

1.56

275.2

1.42

266.5

1 8

276.6

1.44 267.3

1.60

277.5

1.46 268.8

1.62

279.1

k c

1.64

280.6

1.66 281.4

1.68 282.9

1.70

283.8

2.00

297.9

2.20 307.3


42/50

IS 12992 Part 1) : 1993

0 60

0 50

0 5 10 15 20 25 30 35 40 15 50

% GAUGE BACK PRESSURE:

BACK PRESSURE, bar x ,oo

SET PRESSURE, bar

NOTE -The above curves represent a compromise of the values recommended by a number of relief valve manufacturers and may be

used when the make of valve or the actual critical flow pressure point for the vapour or gas is unknown. When the make is known, the

manufacturer should be consulted for the correction factor.

These curves are for set pressures of 3.5 bar and above. They are limited to back pressure below critical flow pressure for a given set

pressure. For subcritical flow back pressures below 3.5 bar, the manufacturer must be consulted for the values of&

FIG.

2

VARLULEORCONSTANTACK-PRESSUREIZINGACTORK,,FOR ALANCED

BELLOWSAFEITRELIEFALVESVAPOURSNDGASES)


43/50

IS 12992 ( Part 1) : 1993

1.00

0.95

0.90

0 65

0.60

0.75

0.70

0.65

0.60

0.55

0.50

0 10 20 30 10 50

BACK PRESSURE, bar

1. GAUGE B ACK PRESSURE:

x

100

SET PRESSURE, bar

NOTE-The above curve represents a compromise of rbcvalues recommended by a number of relief valve manufacturers. This

curve may be used when the make of the valve is not known. When the make is known the manufacturers should be consulted for

the correction factor.

FIG.3 VARIABLE RCONSTANTACK-PRESSUREKLNG ACIDRI& FOR .5 PERCENT

OVERPRESSUREN BALANCEDELLOWSSAITTY RELIEF ALVESLIQUIDSO~Y)]


44/50

IS 12992 Part 1) : 1993

0.90

0.60

z.2

0 0.70

E

f 0.60

z

2

0.50

tt

g 0.40

00

0.30

0.20

0

0 5 to 15 20

25 30 35 40 45 50

PERCENT OVERPRESSURE

NOTE-The

abovecurveshows

hat up to and including 25 percent overpressure capacity is affected by the change in lift the change

in orifice discharge co-efficient and the change in overpressure.

Above

25 percent capacity is affected only by the change in

overpressure.

Valves operating at low overpressures tend to chatter; therefore, overpressures of less than JO percent should be avoided.

FIG.4 CAPACITYORRECTIONACKIRS UEM OVER-PRESSUREORREUEFAND m

RELIEF ALVESNLIQUID mvm


45/50

As in the Original Standard, this Page is Intentionally Left Blank


46/50


47/50

As in the Original Standard, this Page is Intentionally Left Blank


48/50

IS 12992 (

Part

1) : 1993

ANNEX D

(Clause 4.2)

SIZING FOR GAS EXPANSION DUE TO EXTERNAL FIRE

The discharge areas for safety and safety relief valves

F =

on gas containing vessels exposed to open fires can be

determined by the use of the following formula :

A. =

where

A =

F

A= +x 18.86

0

P, =

Effective discharge area of the valve, in square

centimetres.

An operating factor determined from Figure 5.

Exposed surface area of the vessel, in square

metres; and

Upstream pressure, in bar. This is the set pres-

sure multiplied by 1.10 or 1.20 ( Depending on

the over pressure permissible) plus the at

mospberic pressure, in bar.

i.005

0.015

0.025

0.035 0.045 0.055

RELIEF VALVE FACTOR F1

NOTE - F = Factors for noninsulated carbon steel vessels in gas service exposed to open fires.

FIG.5 SIZING ORGASEWANSION UETOEXTERNALIRE

43


49/50

-____

~

Standard Mark

The use of the Standard Mark is governed by the provisions of the Bureau of Indian

Standards Act 1986 and the Rules and Regulations made thereunder. The Standard Mark on

-products covered by an Indian Standard conveys the assurance that they have been

produced to comply with the requirements of that standard under a well defined system of

tnspection, testing and quality control which is devised and supervised by BIS and operated

by the producer. Standard marked products are also continuously checked by BIS for con-

formity to that standard as a further safeguard. Details of conditions under which a licence

for the use of the Standard Mark may be granted to manufacturers or producers may be

I

obtained from the Bureau of Indian Standards.

I


50/50

Bureau of Indian Standards

BIS is a statutory institution established under the Bureau o ndian Standards Act, 1986 to promote

harmonious development of the activities of standardization, marking and quality certification of goods

and attending to connected matters in the country.

Copyright

BIS

has the copyright of all its publications. No part of these publications may be reproduced in any

form without the prior permission in writing of BIS. This does not preclude the free use, in the course

of implementing the standard. of necessary details, such as symbols and sizes, type or grade

designations. Enquiries relating to copyright be addressed to the Director ( Pubhcations ), BIS.

Review of Indian Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards are also

reviewed periodically; a standard along with amendments is reaffirmed when such review indicates that

no changes are needed; if the review indicates that changes are needed, it is taken up for revision.

Users of Indian Standards should ascertain that they are in possession of the latest amendments or

edition by referring to the latest issue of BIS Handbook

and Standards Monthly Additions.

Comments on this Indian Standard may be sent to BIS giving the following reference:

Dot No. HMD 17 ( 5119)

Amendments Issued Since Publication

1

Amend No.

Date of Issue

Text Affected

BUREAU OF INDIAN STANDARDS

Headquarters:

Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002

Telephones : 331 01 31, 331 13 75

Regional Offices I

Central : Manak Bhavan, 9 Bahadur Shah Zafar Marg

NEW DELHI 110002

Eastern

:

l/14 C. I. T. Scheme VII M, V. I. P. Road, Maniktola

CALCUTTA 700054

Northern 8 SC0 445-446, Sector 35-C, CHANDIGARH 160036

Telegrams : Manaksanstha

( Common to all offices )

Telephone

I

331 01 31

331 13 75

I

37 84 99, 37 85 61

37 86 26, 37 86 62

I

53 38 43, 53 16 40

53 23 84

Southern : C. I. T. Campus, IV Cross Road, MADRAS 600113

I

235 02 16, 235 04 42

235 15 19, 235 23 15

spring loaded safety relief valves_design

Documents