10 Safety Valves

8/4/2019 10 Safety Valves

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Western Regional Boiler

Association Annual Meeting

March 17, 2010

Steve Teeter- Bay Valve Service

Safety Valves

Operation, Handling and CodeCompliance


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Mechanical Device designed toprotect against an over pressure

condition. Last Line of Defense

What is a SAFETY VALVE?


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Protects Life and Property bymaintaining control of safe working

pressures of related piping andequipment.

What does a Pressure Relief

Valve do?


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Set Pressure: Gauge pressure at the valve inlet

for which the safety valve has been set to relieve atTolerance:Section 1: 15-70 psi + or 2 psi

71-300 psi + or 3 % of Set

301-1000 psi + or 10 psi1001 and up + or 1% of SetSection 8: 15-70 psi + or 2 psi

71 psi and up + or 3 % of Set

Operating Pressure: Gauge pressure to which theprocess or system normally operates in service,Not to exceed 90% of valves set pressure for aspring operated valve.

Definitions:


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Issues affecting Capacity Superimposed Back pressure:

Constant and Variable

Constant: Fixed Value and existscontinuously prior to and duringvalve opening

Variable: Varies over a range andexists prior to and during valveopening

Definitions:


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Blow down: Difference between set pressure and

reseating pressure of a pressure relief valveexpressed as a percentage of the set pressure

Section 1: 15-67 psi 4% of Set Pressure

68 to 250 psi 6% of Set Pressure

251 to 375 psi 15 psi 376 and above 4 % of Set Pressure

Section 8: To Manufacturers Specs (5-10% of Set

Pressure approximate) Maximum Allowable Working Pressure (MAWP)

Maximum gauge pressure permissible in a vesselat a designated temperature

Definitions:


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Overpressure: Pressure increase overthe set pressure of the primaryrelieving device. Highest Pressure atwhich the primary safety relief valve isset to open.

Definitions:


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LIFT

The disc rise in a Safety Relief

Valve

Typically 1/4 of the bore diameterat full capacity


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A spring exerts a closing force on avalve disc.

The spring force has to be largeenough to hold the valve disc closedat normal operating pressure and

sized correctly to open when thepressure exceeds the set pressure ofthe safety Valve.

How does a Safety Valve work?


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The set pressure is made byadjusting a compression screwabove the spring.

The blowdown of the safety valvemust be adjusted as well.

This is accomplished by using an

upper adjusting and lower adjustingcompression ring to achieve desiredblowdown specifications.

How does a Safety Valve work?


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Lift Lever Assembly

Adjusting Screw

Spring Assembly

Spindle

Guide

Disc Holder

Disc

Adjusting Rings

Nozzle


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SAFETY VALVES


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WHY PRESSURE RELIEFDEVICES?

WHAT BACKS UP A SAFETY

VALVE ??


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TENNIS SHOES ?!!?


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What is

Good Operating Condition??

What must be done to maintain a

Safety Valve in good workingorder?


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Hey we have a steam leak!


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ASME/National Board CodeStamped Valves

Code Valves must be identified by amanufacturers metal tag with applicable NationalBoard ASME symbol stamps on the tag attachedto each valve.

Without the manufacturers tag the valve should

not be in service.


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ASME CODE


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ASME CODESYNOPSIS

ASME Section I - Power Boilers

Set Pressure Tolerances

Blowdown Requirements

System Overpressure Allowances No Block Valves

Safety Valves Only

Valves Calibrated (set) on Steam Lifting Lever Required


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NBIC A07 2.5.8

Recommended Inspection and TestFrequencies for Pressure Relief

Devices a) Power Boilers

1) Pressure less than 400 psig: ManualCheck every 6 months; Pressure test

annually to verify nameplate setpressure or as determined by operatingexperience as verified by testing history.


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NBIC A07 2.5.8

2) Pressure greater than 400 psig:

Pressure test to verify nameplate setpressure every 3 years or as

determined by operating experience as

verified by testing history


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NBIC A07 2.5.8

3) Pressure tests should be performed

prior to bringing the boiler down forplanned internal inspection so neededrepairs or adjustments can be made

while boiler is down.


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NBIC A07 2.5.8

Note: When any boiler experiences

an overpressure condition such that

the safety or safety relief valvesactuate, the valves should be

inspected for seat leakage and

other damage as soon as possibleand any deficiencies corrected.


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NBIC A07 2.5.8

3) Service Records with test

results should be maintained for

all overpressure protectiondevices.


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For a Safety Valve to be Safe it

must:

Relieve at the proper setpressure

Relieve the required capacity


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Means to Determine a SafetyValve will relieve at the Proper

Set Pressure1. Lift the Valve Lever (High Risk)

2. Individual Safeties and Over-pressuringthe Boiler (Live Set) (High Risk)

3. Lift Assist Device (EVT) (Low Risk)

4. Removing Safety Valve and having ittested at a Certified Shop (No Risk)


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Means to Actuate a Safety Valve

1. Lift the Valve Lever

Must be done at a minimum of 75% ofoperating pressure


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Means to Actuate a Safety Valve

2. Live Set on the Boiler

Exercising the Valves by overpressuringthe relief valves above Set Pressure


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Consolidated EVT II

Portable Diagnostic Tool

In-Line Pressure ReliefValve Testing

ASME Code Approved

Records ValvePerformance Signatures

Data Retention &Reports

Detect PerformanceIssues


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Means of Determining a Safety

Valve can Relieve Remove Valve and bring to Valve Repair

Shop for Verification


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National Board VR Certification

Provides the industry the means toidentify organizations that havedemonstrated an adequate quality

system for the repair of Safety Valves The goal is to improve the caliber of

repairs for ASME capacity certifiedsafety and safety relief valves tocontinue to protect boilers and systemsfrom catastrophic overpressures

VR Repair A thori ation


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Repaired Valves Meet ApplicableASME Standards for New Valves

Stringent Quality Control Program

Technician Training and EvaluationProcess

Documentation & Record Keeping

Steam, Air, Water Testing

Annual Audits

VR Repair AuthorizationProgram

NATIONAL BOARD VR CERTIFICATE


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NATIONAL BOARD VR CERTIFICATE

H dli f S f t R li f V l


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Handling of Safety Relief Valves

1. Field Hydrostatic Testing of your Boiler

Importance of gagging safety relief valves toprevent damage

Should be gagged by a certified technician

If Safety Valves are not gagged they should beremoved

2. Storage: Flanged Safety Valves should bebolted to a pallet in vertical orientation tomaintain spindle and disc alignment

Handling of Safet Relief Val es


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Handling of Safety Relief Valves

3. Wiring of Lift Levers

Valves have lift levers wired to the body toprevent exercising the valve by picking it upby the handle or rigging it by the handle

Valves will function correctly with lift lever wiredto the body of the valve, but should beremoved after installation.


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Boiler Non Return Valve

Stop Check Valve versus Boiler NonReturn Valve

Purpose Function

Issues to be aware of


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Questions?

Thank you!

Documents

10 Safety Valves