PRV Sizing Selection Application Guidelines - xa.yimg.comxa.yimg.com/kq/groups/15856354/737305830/name/PRV... · PRV Sizing, Selection & Application Guidelines 1. Topics Covered

PRV Sizing, Selection & PRV Sizing, Selection & Application GuidelinesApplication 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 valveWhat 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 criteriaWhat 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 rangeWe are great and we should sell them 2

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A Pressure Relief Valve (Safety Valve) is a self actuatedvalve 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 DischargeThermal ExpansionExposure to External FireFailure of any Equipment such asa Control Valve or an Exchanger Tube

Must consider the one worst case while sizing a PRD

5

Blocked Discharge

FULL INPUT FLOWFULL INPUT FLOWFULL INPUT FLOW

(FROM COMPRESSOROR PUMP)

(FROM COMPRESSOR(FROM COMPRESSOROR PUMP)OR PUMP)

PRDPRDPRD

PressurePressureVesselVessel

OUTLET BLOCKVALVE CLOSED

6

PRDPRD

STORAGE ORSTORAGE ORPROCESS VESSELPROCESS VESSEL

External Fire

7

PRDPRDPRD

LIQUID FULL PIPE OR LIQUID FULL PIPE OR PRESSURE VESSELPRESSURE VESSEL

Thermal Expansion

8

BLOCKED DISCHARGEBLOCKED DISCHARGE

EXTERNAL FIREEXTERNAL FIRE

THERMAL EXPANSIONTHERMAL EXPANSION

Must Consider The OneWorst Case

Must Consider The OneWorst 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

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Back-Pressure...

Constant Back-Pressure valve discharge into a

system at a constant pressure

pump suction, steam tank, ...

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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 from

the 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 AP

L

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Back-Pressure

Back-Pressure can creates many problems on a PRV modify set reduce valve capacity instability or chattering introduce corrosive

environment to the inner chamber

Backpressure

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Backpressure on Conventional valves

Conventional Unbalanced Backpressure acts

on top of the Disc Holder Set pressure varies

one for one withbackpressure

BP

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Backpressure on Conventional valves

Constant Backpressureactual set = bench set + backpressure

required set: 10 barsconstant backpressure: 2 barsbench set = 10 - 2 = 8 bars

Variable BackpressureSuper-imposed = set point will vary with

back-pressureBuilt-up = acceptable up to 10% of set

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Bellows valve

The Balanced Bellows isolates top side of disc

for Back-P isolates spring and

guide from outlet environment

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50%

60%

70%

80%

90%

100%

0% 20% 40% 60% 80%

Built-Up Back Pressure in % of SET Pressure

%R

ated

Lift

ConventionalSpring 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 with Pressure 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 Greenwood Crosby & 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 from rising 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% above MAWP Single Safety Valve as overpressure protection must be set at or below the MAWP Multiple Safety Valves Installation

o One Safety Valve set at or below MAWPo 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 Set Pressure

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 Test Con 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 Safety Relief 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 & soft seated 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 for Repairing 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…..

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MAWPMAWP

(MAX. SET)(MAX. SET)

ONE VALVE ONLYONE VALVE ONLY

ONEONE

PRDPRD

10%10%

OR 3 PSIG,OR 3 PSIG,[0.20 BARG][0.20 BARG]WHICHEVERWHICHEVERIS GREATERIS GREATER

110110

100100

ASME VIII, Blocked Discharge

ALLOWABLE ALLOWABLE OVERPRESSURE:OVERPRESSURE:

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1ST VALVE1ST VALVEMAX. SET: MAWPMAX. SET: MAWP

ALLOW. OVERPRES.: ALLOW. OVERPRES.: 16%16%

MULTIPLE VALVESMULTIPLE VALVES

MAWPMAWP

116116

105105

100100

22NDND, 3, 3RDRD, ..., ...

2ND VALVE2ND VALVE

MAX. SET: MAX. SET: 105%105% MAWPMAWP


11STST

ASME VIII Blocked Discharge

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1 VALVE1 VALVE


MAWPMAWP

121121

100100

21%21%

ASME VIII, Fire

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MAX SET:MAX SET:1ST VALVE: MAWP1ST VALVE: MAWP2ND VALVE: 110% OF MAWP2ND VALVE: 110% OF MAWP

ALLOW. OVERPRES.:ALLOW. OVERPRES.:1ST VALVE: 21%1ST VALVE: 21%2ND VALVE: 10%2ND VALVE: 10%

11STST VALVEVALVE

121121121

MAWPMAWPMAWP100100100

110110110

2ND , 3RD, ...22NDND , 3, 3RDRD, ..., ...

2 VALVES2 VALVES

ASME VIII, Fire

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EFFECTIVE 1EFFECTIVE 1--11--85, VALVES FOR ALL85, VALVES FOR ALL--LIQUID LIQUID SERVICE MUST HAVE SERVICE MUST HAVE CAPACITYCAPACITY AND AND OPERATIONOPERATION CERTIFIED ON WATER. VALVE CERTIFIED ON WATER. VALVE MANUFACTURER MUST:MANUFACTURER MUST:

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

•• STAMP NAMEPLATE CAPACITY IN STAMP NAMEPLATE CAPACITY IN ““GPM GPM WATERWATER””..

•• ONLY ONLY 10%10% OVERPRESSURE IS ALLOWED OVERPRESSURE IS ALLOWED ((NOT PREVIOUS 25%NOT PREVIOUS 25%).).

Liquid Service

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

OROR

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

PRESSURE TEST TO AT LEAST 1.5 TIMES DESIGN PRESSURE TEST TO AT LEAST 1.5 TIMES DESIGN PRESSURE OF VALVE (1 minute) PRESSURE OF VALVE (1 minute)

NO LEAKAGE ALLOWED.NO LEAKAGE ALLOWED.

Factory Proof Test Factory Proof Test of Primary Section of PRVof Primary Section of PRV

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OVER 1OVER 1”” (25 mm) INLET SIZE(25 mm) INLET SIZE

ANDAND

WHEN PRV DISCHARGES INTO HEADERWHEN PRV DISCHARGES INTO HEADER

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

GAS PRESSURE TEST OF AT LEAST 30 psigGAS PRESSURE TEST OF AT LEAST 30 psig[2.04 barg].[2.04 barg].

NO LEAKAGE ALLOWED.NO LEAKAGE ALLOWED.

Factory Test Factory 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 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 ‘Field test’ not easy

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Bellows Spring Valves - General

Advantages Protected guiding parts Less sensitive to back

pressure Wide range of materials Large chemical

compatibility 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

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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 inlet

losses Modulating valve stable

on any service

Disadvantages Needs special

configuration for polymerising, dirty fluids

Limitation of soft goods in temperature, chemical

More parts More difficult to select

various configuration Needs more details on

process conditions

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Seat Tightness is a Concern

Service pressure in % of set Up to 95%

Spring valves with soft seatPOSV

Above 95%Assisted spring valvesPOSVAlways check with factory

Very dependent on applicationGas 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 limit38

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)

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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 J orifice Smaller than J()S-E No API 526

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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®

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Two-Phase Flow

Modulating POSV recommendedStable alwaysNo risk of over-sizingBack-pressure friendly

Spring loaded valves Recommend

Liquid trimBalanced 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)

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Set Pressure above API 526

Spring valve required: BlockBody®Using forged blocks, almost no limits

Pilot Operated Safety ValvesMost 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 to support 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 kinetic energy

As few gases behave this way correction factors are used (Gas Constants & Compressibility factors)

2 Flowing Conditions: SONIC or SUBSONIC50

Gas Flow above 1.03 Bar G

A nozzle area, cm2 P1 absolute inlet press. barAW flow, kg/hr P2 absolute outlet press. barAV flow, Nm3/hr Kb back-pressure factorC gas constant T relief temp, ºK (ºC+273)K ASME flow coefficient Z compressibility factor

M molecular weightP1 = Set + OverPressure - Inlet Losses + Atmosp.Pres (1.013 bar a)P2 = Back Pressure + Atmospheric Pressure

A T ZM

1316. WC K P K

A V M T Z17.02 C K P K1 b 1 b

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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

A T ZM

1316. WC K P K

A V M T Z17.02 C K P K1 b 1 b

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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)

A T ZM

1316. WC K P K

A V M T Z17.02 C K P K1 b 1 b

53

Sonic & Subsonic Flow

Theoretical nozzle When BP (P2)< PC, flow is

Sonic capacity depends only on P1 flow reaches the speed of

sound for particular gas no reduction of P2 will

increase the flow

When BP > PC, flow becomes Subsonic flow velocity is now less than

speed of sound then capacity depends on P any increase of P2 will reduce

the velocity thus the actual capacity

Back Pressure

100%

50%

0% 100%50%

Capacity

P PkC

kk

1

121

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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

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Steam

Essential data from customer: W Set Pressure and Over Pressure (Code!)

ASME I sizing: 52.5 becomes 52.45! Temperature (will give the superheat factor)

And also any details about the installation, the purity of the steam...

A W

52.5 K P K1 S

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Liquids

A nozzle area, cm2 p1 inlet pressure barV flow, m3/hr p2 outlet pressure barG specific gravity

KP correction factor for OverPressureKV correction factor for ViscosityKW correction factor for Back-Pressure

p1 = Set + OverPressure - Inlet Losses (+ Atmosp.Pres)p2 = Back Pressure (+ Atmospheric Pressure)

Ap

0.19631 V GK K K K pP V W 1 2

57

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...

Ap

0.19631 V GK K K K pP V W 1 2

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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

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Kv , for Liquid Sizing

100,000

1.00

0.80

0.60

10 1000100 10,000

Kv

catalogueAG V 31313

1st Calc. A with Kv = 1

Select next larger catalogue areaAcatalogue

Determine new Kv = from curve

Recalc. A with new Kv

calculate Reynolds number

A > Acat.YES

Acat is adequate

NOµ = Liquid Viscosity (cP)

60

Conventional Valves on Gas : Constant back pressure

Obtain Kb from manufacturer’s curveBench set = Set - BP

Variable back pressure superimposed: not recommendedbuilt-up <10% okay>10% : definitively NOT!

Kb, Kw... Back Pressure Factors

61

Conventional Valves on Liquid : Constant back pressure

no coefficientBench set = Set - BP

Variable back pressure superimposed: not recommendedbuilt-up <10% okay>10% : definitively NOT!


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

Example

Type JOS-E, K=0.975 = 18.50 cm2 4M6 (23.23) 81 series, K=0.816 = 22.10 cm2 No

Application on Hydrocarbon Vapors Req’d capacity = 75 000 kg/hr Set = 45 barg, OP =10%, No BP Relief temperature = 100ºC M = 34.0 k=1.31 or C=348 Z=0.94

65

Pressure / Temperature

45 barg

100°C

200°C

66

And When…

And when Set < 1.03 Bar G?

And when Fluid is a Mixture of Gas & Liquid?

We’ll see that

later...

67

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LNG Characteristics

Natural Gas itself is dangerous: highly flammable suffocating “Green House” effect

Liquid is cryogenic (-162ºC) high level of energy variable composition

NON-FLOWING POP ACTION POPRV (Closed)NON-FLOWING POP ACTION POPRV (Closed)

100%100%

SetSet

100%100%

SetSet

BlowdownBlowdownSeatSeat

ReliefReliefSeatSeat

69

NON-FLOWING POP ACTION POPRV (Relieving)NON-FLOWING POP ACTION POPRV (Relieving)

100%100%

SetSet

100%100%

SetSet0%0%



70

NON-FLOWING POP ACTION POPRV (Re-Closed)NON-FLOWING POP ACTION POPRV (Re-Closed)

100%100%

SetSet

100%100%

SetSet



71

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 wantsWe can propose, use our experienceWhat is most economical in the

short/medium/long term for the client (depends what he cares about)

Look for ‘proposition’ that others cannot match Lowest bid is not always the winner

Still best technical reputation, use it !72

Documents

PRV Sizing Selection Application Guidelines - xa.yimg.comxa.yimg.com/kq/groups/15856354/737305830/name/PRV... · PRV Sizing, Selection & Application Guidelines 1. Topics Covered