tyco_prv sizing selection application guidelines

8/12/2019 Tyco_PRV Sizing Selection Application Guidelines

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PRV Sizing, Selection &PRV Sizing, Selection &

Application Guidelines Application Guidelines

1



Topics Covered

Some definitions….

Why do we require a Safety Relief Device

Causes of over pressure; the necessity of installing a safety relief valve

What does the code say? ASME, API Standards important notes

Very Important terminologies of safety relief valves More insight to Back Pressure and its effects on PRV sizing & relieving

capacity

Pressure losses, chattering, simmer and their effects on valve selection

Sizing & Selection formulae for liquid, gas and steam application

Constructional and design features – Spring Loaded Pressure Relief Valves

Overview of AGCO Spring loaded Pressure Relief Valve style JOS-E &JBS-E

Constructional and design features – Pilot Operated Pressure Relief Valves

Overview of AGCO Pilot Operated Pressure Relief Valve 200~800 series

More on Pilot Operated Pressure Relief Valves

Comparison of Conventional Spring loaded v/s Bellows Spring loaded v/s Pilot

operated design valves

Some Application Guide lines and selection criteria

What do we have for cryogenic service, LNG application.

Overview of 80 series thermal relief valves, cryogenic trim for pilot valves

Competitive advantages of AGCO valve range

We are great and we should sell them 2



3

A Pressure Relief Valve (Safety Valve) is a self actuated

valve used to control pressure and protect equipment and

personnel Often the final control device to prevent accidents or

explosions

Too often perceived only to comply with codes, regulations,

insurance...

Safety Valves

What does a PRV do? Opens at a pre-calibrated set pressure

Flows a specified rate of fluid capacity

And closes only when the system pressure has returned to a

safe level, usually 7-10% below the set pressure



4

Most Common Causes of Overpressure

Blocked Discharge

Thermal Expansion

Exposure to External Fire

Failure of any Equipment such as

a Control Valve or an Exchanger Tube

Must consider the one worst

case while sizing a PRD



5

Blocked Discharge

FULL INPUT FLOWULL INPUT FLOWULL INPUT FLOW

(FROM COMPRESSOROR PUMP)

(FROM COMPRESSORFROM COMPRESSOROR PUMP)R PUMP)

PRDRDRD

PressurePressureVesselVesselOUTLET BLOCK

VALVE CLOSED



6

PRDRD

STORAGE ORTORAGE ORPROCESS VESSELROCESS VESSEL

External Fire



7

PRDRDRD

LIQUID FULL PIPE ORIQUID FULL PIPE OR

PRESSURE VESSELRESSURE VESSEL

Thermal Expansion



8

BLOCKED DISCH RGELOCKED DISCH RGE

EXTERN L FIREXTERN L FIRE

THERM L EXP NSIONHERM L EXP NSION

Must Consider The One

Worst Case

Must Consider The One

Worst Case



9

Safety ValveProtected System

Maximum Allowable

Pressure

(Design Pressure...)

Reseat Pressure

Blowdown (usually 5-7%)

Overpressure

(Full) Opening Pressure

Set Pressure

(Tight) Shut-Off PressureOperating Pressure

(service pressure

The “money-maker”)

Accumulation

(usually 10%,

depends on code)

Where the SV is

normally sized

Pressures



10

Back-Pressure...

Constant Back-

Pressure valve discharge into a

system at a constant

pressure

pump suction, steam

tank, ...



11

Back-Pressure...

Variable Super-

Imposed valve discharge into a

system at a variable

pressure which exists

when valve is closed

flare system, ...



12

Back-Pressure...

Variable Built-Up exits only when valve is

flowing

created by the flow fromthe valve

always, and increases

with exhaust piping

accidents



13

Conventional Valve

Downwards spring

force (constant)Fd = K x L

Upwards fluid force(variable)

Fu = P x A

Set : Fd = Fu A

P

L



14

Back-Pressure

Back-Pressure can

creates manyproblems on a PRV

modify set

reduce valve capacity instability or chattering

introduce corrosive

environment to the

inner chamber

Backpressure



15

Backpressure on Conventional

valves

Conventional Unbalanced

Backpressure actson top of the Disc Holder

Set pressure varies

one for one withbackpressure

BP



16

Backpressure on Conventional

valves

Constant Backpressure

actual set = bench set + backpressure

required set: 10 bars

constant backpressure: 2 bars

bench set = 10 - 2 = 8 bars

Variable Backpressure

Super-imposed = set point will vary withback-pressure

Built-up = acceptable up to 10% of set



17

Bellows valve

The Balanced Bellows

isolates top side of disc

for Back-P

isolates spring and

guide from outletenvironment



18

50%

60%

70%

80%

90%

100%

0% 20% 40% 60% 80%

Buil t-Up Back Pressure in % of SET Pressure

% R a

t e d

L i f t

Conventional

Spring Valve

BalancedSpring Valve

Lift vs Built-Up Back Pressure



ASME Boiler and Pressure Vessel Code

Developed in 1914 to address boiler

explosions in the U.S.

Five book sections deal specifically withPressure Vessel Design & Equipment

What does the code say?

ASME, API Standards

ASME Sec I : power boilers

ASME Sec II : materials to use

ASME Sec V : NDE

ASME Sec VIII : Construction of pressure vessels

ASME Sec IX : welding, brazing



ASME Boiler and Pressure Vessel Code

Section I Power Boilers - “V” Stamp. Addresses Steam Boiler applications only

Safety Valve must attain full lift, discharging

its rated capacity at 3 % overpressure.

Valve must close at 96 % of its stamped set

pressure (4 % Blowdown maximum).

Lifting Lever mandatory to manually lift the

Disc off the nozzle seat for testing purposes



-Boiler and Pressure Vessel Code ASME VIII Unfired

Pressure Vessel Code “UV” Stamp

- The base code used for Anderson GreenwoodCrosby & Sapag Safety Valves for the oil & gas

process market

AGC CAN provide Safety Valves built to the requirementsof ASME Section VIII AND Set lower than 15 PSIG [1.03 barg]



THE NATIONAL BOARD CERTIFIES VALVE CAPACITY AND

VERIFIES VALVE COMPLIANCE WITH THE ASME CODE

ASME VIII Unfired Pressure Vessel Code Basic

Requirements

Pressure Relief Devices must prevent the pressure fromrising more than 10% (or 3psi, whichever is greater) above

the highest set pressure that any relief device is set, but in no

event more than 16% above the MAWP.

(to be continued in next page…)



If an additional hazard can be created by exposure of

the vessel to a fire, relief devices must be capable of

preventing the pressure from rising more than 21% aboveMAWP

Single Safety Valve as overpressure protection must be

set at or below the MAWP

Multiple Safety Valves Installationo One Safety Valve set at or below MAWP

o Balance may be staggered, set with the highest

being no more than 105% of MAWP

Blowdown (reseat) is not addressed by Section VIII for

production valves, therefore blowdown testing is not

performed at the factory

Depending on process fluid and valve type, blowdown

can vary from five to twenty percent



Part UG – General Requirements : UG–126 SetPressure

Set pressure tolerance:-

Up to 70 PSIG (4.8 bar) : ± 2 PSIG (0.14 bar)

Above 70 PSIG : ± 3%

UG–136 Minimum Requirements for Pressure Relief

Valves

Valves on air, water over 140F, or steam require a lifting

device:-

Spring Operated valve: Lifting Lever

Pilot Operated valve: Lifting Lever, Push Button or Field TestCon

Cast iron seats and discs not permitted

Springs must be of corrosion resistant material or have a

corrosion resistant coating



API Standard 526 Flanged Steel SafetyRelief Valves

An industry standard which covers:-

Orifice Designation and Effective Area (D to T)

Valve Size and Rating, Inlet x Outlet

Material Requirements - Body and Spring

Pressure and Temperature Limits

Center-to-Face Dimensions, inlet and outlet

API Standard 527 Seat Tightness of Pressure Relief

Valves

Methods for determining seat tightness for metal & softseated PRVs

Test Methods: air, steam and water

Acceptance Criteria

Soft Seated Valves: no leakage



Other Codes and Standards

ANSI B95.1 (PTC-25.3) : Terminology for Pressure Relief Devices

(refer to Crosby Engineering Handbook)

N.A.C.E. MR0175 (2002) / MR0103 : Sulfide Stress Cracking

Resistant Metallic Materials for Oilfield Equipment

National Board “VR” Repair Symbol : Rules and Procedures forRepairing ASME and National Board Stamped Pressure Relief Valves

ASME/ANSI B16.5. Pipe flanges and flanged fittings.

ASME/ANSI B16.34. Valves - Flanged, Threaded and Welding End.

MSS SP-55. Quality standards for steel castings for valves, flanges

and fittings and other piping components.

And lot more……. All are based on customer specification

requirements…..



27

MAWPAWP

(MAX. SET)MAX. SET)

ONE VALVE ONLYNE VALVE ONLY

ONENE

PRDRD

100

OR 3 PSIG,R 3 PSIG,

[0.20 BARG]0.20 BARG]

WHICHEVERHICHEVER

IS GREATERS GREATER

110110

100100

ASME VIII, Blocked Discharge

ALLOWABLE ALLOWABLE

OVERPRESSURE:OVERPRESSURE:



28

1ST VALVEST VALVEMAX. SET: MAWPAX. SET: MAWP

ALLOW. OVERPRES.:LLOW. OVERPRES.: 166

MULTIPLE VALVESULTIPLE VALVES

MAWPAWP

116116

105105

100100

2NDD

, 3 3RDD

, ... ...

2ND VALVEND VALVE

MAX. SET:AX. SET: 10505 MAWPAWP


1STT

ASME VIII Blocked Discharge



29

1 VALVE VALVE


MAWPAWP

121121

100100

211

ASME VIII, Fire



30

MAX SET:AX SET:

1ST VALVE: MAWPST VALVE: MAWP

2ND VALVE: 110 OF MAWPND VALVE: 110 OF MAWP

ALLOW. OVERPRES.:LLOW. OVERPRES.:

1ST VALVE: 21ST VALVE: 21

2ND VALVE: 10ND VALVE: 10

1STT VALVEALVE

1212121

MAWPAWPAWP000000

1101010

2ND , 3RD, ...NDD , 3 3RDD, ... ...

2 VALVES VALVES

ASME VIII, Fire



31

EFFECTIVE 1FFECTIVE 1-1-85, VALVES FOR ALL5, VALVES FOR ALL-LIQUIDIQUID

SERVICE MUST HAVEERVICE MUST HAVE CAPACITYAPACITY ANDNDOPERATIONPERATION CERTIFIED ON WATER. VALVEERTIFIED ON WATER. VALVE

MANUFACTURER MUST:ANUFACTURER MUST:

•• SET THE VALVE ON WATER.ET THE VALVE ON WATER.

•• STAMP NAMEPLATE CAPACITY INTAMP NAMEPLATE CAPACITY IN “GPMPM

WATERATER”.

•• ONLYNLY 100 OVERPRESSURE IS ALLOWEDVERPRESSURE IS ALLOWED

(NOT PREVIOUS 25OT PREVIOUS 25 )..

Liquid Service



32

OVER 1VER 1” [25 mm] INLET SIZE25 mm] INLET SIZE

ORR

SET PRESSURE OVER 300 psig [20.7 barg]ET PRESSURE OVER 300 psig [20.7 barg]

PRESSURE TEST TO AT LEAST 1.5 TIMES DESIGNRESSURE TEST TO AT LEAST 1.5 TIMES DESIGN

PRESSURE OF VALVE (1 minute)RESSURE OF VALVE (1 minute)

NO LEAKAGE ALLOWED.O LEAKAGE ALLOWED.

Factory Proof TestFactory Proof Test

of Primary Section of PRVof Primary Section of PRV



33

OVER 1VER 1” (25 mm) INLET SIZE25 mm) INLET SIZEANDND

WHEN PRV DISCHARGES INTO HEADERHEN PRV DISCHARGES INTO HEADER

AND BONNET IS A CLOSED DESIGN.ND BONNET IS A CLOSED DESIGN.

GAS PRESSURE TEST OF AT LEAST 30 psigAS PRESSURE TEST OF AT LEAST 30 psig

[2.04 barg].2.04 barg].

NO LEAKAGE ALLOWED.O LEAKAGE ALLOWED.

Factory TestFactory Test

of Discharge Section of PRVof Discharge Section of PRV



Conventional Spring Valves -

General

Advantages

Rugged design

Wide range of materials

Large chemical

compatibility

High temperaturecapability

Compatible with fouling or

dirty service

Disadvantages

Metal seat prone to

leakage

Long simmer or blowdown

Prone to chatter on liquid

if not well selected

Sensitive to inlet losses

Limitations in

pressure/size

No serviceable on line ‘Field test’ not easy

34



Bellows Spring Valves - General

Advantages

Protected guiding parts

Less sensitive to back

pressure

Wide range of materials

Large chemicalcompatibility

High temperature

capability

Compatible with fouling or

dirty service

Disadvantages

Metal seat prone to

leakage

Long simmer or blowdown

Prone to chatter on liquid

if not well selected

Sensitive to inlet losses

Limitations in

pressure/size

No serviceable on line

Limited bellows life

High maintenance costs

‘Field test’ not easy

35



Pilot Operated Valves - General

Advantages Smaller sizes with large

orifices Very good seat tightness

‘Field test’ easy

Not affected by back-

pressure In-line maintenance

(AGC)

High flexibility of design

Suitable for high inletlosses

Modulating valve stableon any service

Disadvantages Needs special

configuration forpolymerising, dirty fluids

Limitation of soft goods intemperature, chemical

More parts More difficult to select

various configuration

Needs more details onprocess conditions

36



Seat Tightness is a Concern

Service pressure in % of set

Up to 95%Spring valves with soft seat

POSV

Above 95% Assisted spring valves

POSV

Always check with factory Very dependent on application

Gas or liquid, pressure regulation,

pulsations…37



Blowdown is a Concern

Short blowdown required

Attention! Inlet pressure losses! POSV and 80’s = up to 3%

J()S-E = on application

Long blowdown required POSV and 80’s = up to 15%, gas service

J()S-E = up to 25%, on application, gas service

Liquid service = non-adjustable, 20 to 25% for

most of the spring valves If inlet pressure drop is a concern

POSV with remote sense: almost no limit

38



Extreme Temperature ?

Cryogenic… <-70ºC

Thermal relief = prefer 81 series

Process = prefer POSV (249…)

Vaporiser required for liquids

Balanced valve not needed

JOS-E can be proposed Balanced valve needed

Many customers do not accept Bellows valves

High Temperature

Metal seats If POSV required

727 or thermal barrier on gas only (pipe length)

39



Weight or Space is Important ?

POSV

Particularly in big sizes, up to 50%+ savings J()S-E

A, B, G or H caps (no extended spindle)

Omnis and 80’s available up to G and Jorifice

Smaller than J()S-E

No API 526

40



Large Capacity Required

Spring Loaded valves

JOS-E has a T2 orifice (180.1 cm2 with K=0.975)

‘Over – T’ spring valves

Sapag brand with CE mark

Or BlockBody®

POSV Full Bore valve, up to 8”x10” (251.3 cm2, gas & liquids) or

10”x14” (464.5 cm2, gas only) straight from catalogue

Multiple valves required

PSV 3045-A/B/C/D …

POSV (full bore or even API sizes) or BlockBody®

41



Two-Phase Flow

Modulating POSV recommended

Stable alwaysNo risk of over-sizing

Back-pressure friendly

Spring loaded valves Recommend

Liquid trim

Balanced valvesGas and Liquid certified (same model nr) !

JLT-JBS, 81P, Omni-BP

42



Reciprocating Compressor/Pump

Safety valve may

Leak Flutter

Open without reason

Wear out very quickly POSV with

Pressure Spike Snubber (gas)

Liquid Pulsation Dampener (liquid)

43



Set Pressure above API 526

Spring valve required: BlockBody®

Using forged blocks, almost no limits Pilot Operated Safety Valves

Most of the valves can go one rating higher

than shown in catalogue, or more Careful!

Reaction Force

Full bore POSV can be supplied with dual outlets

Noise…

44



Now some real Fun!Now some real Fun!

45



SizingSizing

This is funny! This is funny!

46



PRV Sizing Theory

Sizing PRV = Determine the correct orifice

for the specific valve type to be used tosupport a required relieving capacity.

Typical Method:

1 – Establish a set pressure by customer

2 – Determine the relieving capacity

by customer

3 – Select an orifice that will flow the required

relieving capacity Our Duty !

47



PRV Sizing Theory

How !

Method 1 – By using capacity chart

Self explanatory… But only gives capacity for Air, Water or Saturated Steam.

48



PRV Sizing Theory

How !

Method 2 – By calculation

49



Sizing for Vapors & Gases

Calculated by Capacity Weight or Volume

Formulas based on the perfect gas laws Assume gas does not gain or loss heat

(adiabatic)

Energy of expansion converted into kineticenergy

As few gases behave this way correction

factors are used (Gas Constants &

Compressibility factors)

2 Flowing Conditions: SONIC or SUBSONIC

50



Gas Flow above 1.03 Bar G

A nozzle area, cm2 P1 absolute inlet press. barA

W flow, kg/hr P2 absolute outlet press. barA

V flow, Nm3/hr Kb back-pressure factor

C gas constant T relief temp, ºK (ºC+273)K ASME flow coefficient Z compressibility factor

M molecular weight

P1 = Set + OverPressure - Inlet Losses + Atmosp.Pres (1.013 bar a)

P2 = Back Pressure + Atmospheric Pressure

AT Z

M

1316. W

C K P K

AV M T Z

17.02 C K P K1 b 1 b

51




Essential data from customer:

W or V, and description of the fluid

Set Pressure and Over Pressure

Back-pressure

Temperature

M or Density

Better to have also C or k=Cp/Cv, and Z

if unknown: C = 315 and Z=1

AT Z

M

1316. W

C K P K

AV M T Z

17.02 C K P K1 b 1 b

52




A increases (bigger valve) with W (V) and T

also with

low Set low overpressure

low C (Cair > Cnat gas > Cpropane)

low nozzle coefficient

high back-pressure (Kb < 1)

AT Z

M

1316. W

C K P K

AV M T Z

17.02 C K P K1 b 1 b

53



Sonic & Subsonic Flow

Theoretical nozzle

When BP (P2)< PC, flow isSonic

capacity depends only on P1

flow reaches the speed ofsound for particular gas

no reduction of P2 willincrease the flow

When BP > PC, flow becomesSubsonic

flow velocity is now less than

speed of sound then capacity depends on P

any increase of P2 will reducethe velocity thus the actualcapacity

Back Pressure

100%

50%

0% 100%50%

Capacity

P P kC

k

k

1

12

1

54



Steam

Simplified formula

Ks = coefficient of superheating

when 109 bar a P1 221 bar a, take into account Napier

coefficient

Need a bigger valve for superheated steam (Ks<1)

A

W

52.5 K P K1 S

55



Li id



Liquids

A nozzle area, cm2 p1 inlet pressure bar

V flow, m3/hr p2 outlet pressure bar

G specific gravity

KP correction factor for OverPressure

KV correction factor for Viscosity

KW correction factor for Back-Pressure

p1 = Set + OverPressure - Inlet Losses (+ Atmosp.Pres)

p2 = Back Pressure (+ Atmospheric Pressure)

A p

0.19631 V G

K K K K pP V W 1 2

57

Li id



Liquids

Essential data from customer: V, and description of the fluid

Set Pressure and Over Pressure

Density / SG and Viscosity at relief conditions

Back-pressure

And any other details: reciprocating pump,

pulsations, cold temp. starting...

A p

0.19631 V G

K K K K pP V W 1 2

58

K f Li id Si i



Kp , for Liquid Sizing

Only when valve not

certified at 10%

overpressure (required

by ASME...)

Kp = 0.6 i. e. 40%loss of capacity!

Over Pressure

Kp

10% 30%20%

1.00

0.80

0.60

59

K f Li id Si i



Kv , for Liquid Sizing

100,000

1.00

0.80

0.60

10 1000100 10,000

Kv

catalogue A

GV31313

1st Calc. A with Kv = 1

Select next larger catalogue area Acatalogue

Determine new Kv = from curve

Recalc. A with new Kv

calculate Reynolds number

A > Acat.

YES

Acat is adequate

NOµ = Liquid Viscosity (cP)

60



K K Back Pressure Factors



Conventional Valves on Liquid :

Constant back pressureno coefficient

Bench set = Set - BP

Variable back pressure

superimposed: not recommended

built-up <10% okay

>10% : definitively NOT!

Kb, Kw... Back Pressure Factors

62




Balanced Valves on Gas :

Constant or Variable back pressure<50% : obtain Kb from manufacturer’s curve

>50% : avoid (?!?!)

Balanced Valves on Liquid : Constant or Variable back pressure

(superimposed or built-up)

<50% : obtained KW from manufacturer’s

curve

>50% : avoid (?!?!)


63




Pilot Operated Valves on Gas :

Constant or Variable back pressure from manufacturer’s curve

Pilot Operated Valves on Liquid :

Constant or Variable back pressureKW = 1


64



Pressure / Temperature



Pressure / Temperature

45 barg

100°C

200°C

66

And When



And When…

And when Set

< 1.03 Bar G?

And when Fluid is

a Mixture of Gas &

Liquid?

We’ll see

that

later...

67



NON-FLOWING POP ACTION POPRVNON-FLOWING POP ACTION POPRV



O O G O C O O

(Closed)(Closed)

100%100%

SetSet

100%100%

SetSet

BlowdownBlowdown

SeatSeat

Relief Relief

SeatSeat

69



We are Great and we should sell it



We are Great and we should sell it

Widest SV range available

We should have the ‘right’ valve for the

application Valuable competitive advantage

We do not just sell what the client wants

We can propose, use our experience

What is most economical in the

short/medium/long term for the client

(depends what he cares about)

Look for ‘proposition’ that others cannotmatch

Lowest bid is not always the winner

Still best technical re utation use it !72

tyco_prv sizing selection application guidelines

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