Confronto fra i requisiti delle normative PED e ASME per le misurazioni di livello nei boiler

(in lingua inglese)

Sono analizzati i principali requisiti delle norme PED e ASME per la strumentazione di livello, applicati ai corpi cilindrici delle caldaie. In particolare sono mostrati i punti in comune e le differenze nella loro applicazione.

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Atti di convegni o presentazioni contenenti case history
mcT Petrolchimico Milano novembre 2017 workshop

da Benedetta Rampini
mcT Petrolchimico Milano 2017Segui aziendaSegui


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Milano, 30 novembre 2017 Gli atti dei convegni e pi di 8.000 contenuti su ASME and PED Requirements for Drum Level Instrumentation 2017 Presented by: Amir Hedayatnia Clark-Reliance Corp. Topics ' Gage Glasses and Remote Reading Instruments
' ASME Code Section I Requirements for Drum Level Instrumentation (boilers that operate > 1 Bar G) ' Water Columns(Standpipes) and Water Gage Isolation Valves ' Requirements for Isolation Valves
' ASME CSD-1 Low Water Cutouts Applications
' ASME Section VII Recommendations for Proper Care of Power Boilers ' Common Code Violations (Illustrated)
' PED Requirements ASME Code General Terms Gage Glass Direct Reading Indirect Reading Remote Level Indicator Direct Reading Gage Glasses Tubular Glass to 17 Bar G Bi-Color (Ported) to 206 Bar G Flat Glass (Transparent) to 132 Bar G Prismatic (Reflex) to 24 Bar G End-to-End Reflex Gage Glasses
Are Permitted
- - PG.60.1 Clarifies
the use of multi-
section gages
without overlap, due
to the light
refraction principle
- Transparent Type
Multi-section gages
do require a 25 mm
minimum overlap
Flat Glass Transparent Type Water Gage Glasses with LED Illumination Typical View of Water Level with no obstructions in the
viewing area. The gage must be il uminated, as needed for the level to be readily visible by the operator. Structural Webs are Prohibited
From Flat Glass Gages Designs
- These Webs may
mask the actual
location of the water
- The risk of Masking
the level is enhanced
on elevated gage
glass installations
Bi-Color Water Gage Principle of Operation Water shows GREEN Steam shows RED. Bi-Color Gages must be outfitted with an illuminator to be Code Compliant (Light refracts differently through water than steam with glasses on specific angles) Remote (Indirect) Level Indicator Technologies Differential Pressure Conductivity Magnetic Guided Wave Magnetic Water Level Gages are Permitted up to 62 Bar G Magnetic Level Gage (equipped w/ 4-20 transmitter) For Process (Typical) For Power
Indication Scale External switches
Are not permitted
for control purposes,
such as
Low Water Cutouts
(PG-12 and PG-60)
Code Issues and Concerns for the Use of Magnetic Level Gages on Boiler Drums ' Acceptable as an acceptable Indirect Reading for applications range up to 62 Bar G), Ref: PG12.2 ' The Indication Scale must follow ASME guidelines, Ref: PG-60.3.2 & PG60.3.3 ' May not be used to support a water Gage glass, due to prohibition of stainless steel construction for water columns. Ref: PG-12.3 ' No accessories are permitted to be attached for control purposes (No Trip limiting switches). This device must be used for indication only. Ref: PG- The use of a Magnetic Level Gage does not replace the Code requirement for a Water Gage Glass on any Power Boiler Drum designed to meet Section I of the ASME Code Section I Requirements Operating up to 27 Bar G
One Direct Reading Gage Required
(which must be kept continuous service)
Operating over 27 Bar G
Two Direct Reading Gages in service
or Two Remote (Indirect) Level Indicators
On Continuous Display for the
Operator and One Direct Reading Gage
(Which may be Isolated but kept in serviceable condition)
or One gage glass in continuous service with a camera
system combined with an Indirect Remote Level
Indicator Water Gage Requirements: Section I Requirements for Gage Glass Placement Level 'A' = Lowest Permissible Water Level, at which there will be no danger of overheating the boiler Note: 4 and 6 must not intersect 1 and 2 1- Lower side steam conn. 2- Upper side water conn. 3- Level A
4- Low vision
5- Drum
6- High vision
7- Steam conn.
Section I - References Water Columns (PG-60.2) ' 25 mm (1' min) connections for water column to boiler (PG-60.3.4) ' 20 mm (3/4' min) drain connection (PG-60.2.3) ' Stainless Steel construction for water columns is prohibited (PG-12.3) ' A Code stamp is not required on water columns, because they along with level instruments are considered to be fittings (PG-11) Water Level Indicators (PG-60.1) ' Water Gage Glass Requirements (PG-60.1.1) ' 20 mm (3/4' min) connection size for Remote (Indirect) level indicators (PG-60.3.4) ' Highest & Lowest visible permissible water level (PG-60.1) ' Isolation and Drain Valve Requirements (PG-60.1.2) ' 25 mm (1') Gage overlap requirement for Transparent Gages (PG-60.1) - 1996 ' Transverse or Structural Webs are prohibited from the construction of Transparent (Flat Glass) Water Gages, which may obstruct view of the level(PG60.1) - 2009 ' Stainless Steel is permissible for Gage Glass Body construction (PG-12) ' Magnetic (Float Type) Level Gages are permitted up to 62 Bar G (PG-12) - 2007 ' Gage Cocks not required PG60.4 ' 1991 (See image above ) Section I Valve Requirements ' Isolation valves installed between the drum and a water column are optional and when
installed they must be locked open, to
prevent unauthorized use.
' Isolation (shut off) and drain valves must be installed for any level indicating instrument
(Ref: PG-60.1.2)
' Drain valves must have an unrestricted 6 mm (') minimum opening Globe Valves for Isolation In-line flow prevents sediment or condensate traps, which can lead to false level indication with traditional Globe valves Correct Incorrect Globe type valves are permitted if the lowest edge of the seat is at least 25% of the port diameter.
(Ref: PG-60.3.7)
Specifying Ball Checks on Water Gage Valves ' Ball Checks are not mandatory on ASME Applications ' Ball Checks are mandatory on PED (European EN standards) and IBR (India) Applications ' Ball Check Valves (Reference: 'Automatic Shutoff Valves' in the Appendix of the ASME Boiler Code) and defines the design requirements for this User OPTION. ' Consider the application, before specifying Water Gage Valves with the Ball Check feature. The use of Chain operators improve safety by operating from a distance. Ball Check Specifications, when Applied Must have a
vertical rising
ball in lower
valve to prevent
trap of water in
gage glass
Typical upper
Ball check
Always Install Chain Operated valves for Operator and Plant Safety PG.60.1.2 requires a
means to operate when
the valves are 2 meters
above the operating
floor or platform
ASME CSD-1 (Controls and Safety Devices for Automatically Fired Boilers) ' Applications: Boilers within the fuel input range
>400,000 Btu/hr and < 12,500,000 Btu/hr
' Ref: Section CW-140 for High Pressure Steam Boilers Low Water Cutouts ' ASME CSD-1 Section CW-140 requires two separate devices ' The two devices must be in separate chambers and connected to separate water nozzles from
the drum, but they may connected to the same
steam nozzle.
Note: One of the devices may be inserted directly into the boiler. ' Minimum pipe connection size is 25 mm (1') with a vertical drain at least 20 mm (') ASME Section VII - Recommended Guidelines for the Proper Care of Power Boilers ' Check water level in 2 or more instruments prior to start up and verify when a deviation is observed ' Keep Water Gage Glasses clean and easy to read, confirm there is no deviation that could be mistaken as water level ' Water Gages should be properly illuminated for easy observation ' Excessive blow down may cause premature wear of the gage internals ' Verification of high and low water alarms is critical to the prevention of carryover or damage to drum internals Blowdown Procedure Bypass Low Trip during this procedure Common ASME Code Violations and Concerns ' Isolated inoperable water gages
' Missing water gage glasses
' Missing illumination from water gages
' Inadequate display of remote level indicators in the control room combined
with isolated gages
Code Violations A drain valve is missing on this lower water gage valve Magnetic Level Gage Scale
extends below lower connection,
it will always indicate some level
Photo of Serious Installation Error Code Violation and Operation Risk to Boiler Photo of Corrected Installation Violation and Remedy Before and After ASME Summary Requirements ' Code compliant material is used in all pressure parts ' All welding procedures and personnel are qualified ' All instruments are hydrostatically tested at 1-1/2 times their design
PED Requirements for Instrumentation ' EN12952-7 Subsection 5.4 requires a minimum of two Water Gage Glasses on all Power Boilers or one water gage combined with 2 Remote Level Indicators ' Connecting Tubes (Piping) between the Boiler and the Water Level Indicator must have a minimum inside diameter of 20 mm When the water connecting lines are longer than 750 mm, the inside diameter of the connecting piping must be at least 40 mm Water connecting piping from the Boiler must always be horizontally oriented to the Water Level Indicators PED Requirements for Instrumentation ' 5.4.6 All Water Gage Glasses must be fitted with an internal Self-Closing Safety Device (Ball Checks in the Water Gage Isolation Valves) ' 5.4.5 On each Gage glass the Lowest Permissible Water Level shall be marked 'LWL' ' 5.4.4 The lower limit of the gage glass range shall be at least 30 mm below the lowest permissible level ' The 'open position' on Water Gage Cocks (Valves) shall be indicated Compliance with PED For All PED Categories:
' We conduct a PED Assessment using a Program to evaluate the pressure and
volume of the instrument to determine
the PED Hazard Category
' Prepare a Declaration of Conformity for Article 4 Par. 3 (most level instrumentation), or Category I or II Compliance with PED ' All Categories must be manufactured with material including EN10204 3.1 rating ' On the MTR. All materials must be traceable back to the European Community and
meeting all PED requirements.
' The final PED package (MDR) must be retained for 10 years Compliance with PED Risk Analysis Form required for Category I and II includes: ' Job # (Clark-Reliance Order Number) ' Item # (Clark-Reliance Item Model Number) ' Internal Pressure (pressure from the Hazard Calc.) ' Operating Temp. (Saturated Steam Temp.) ' Static Pressure & Volume of Contents: - (Design Pressure & Volume of contents)
- This Form is signed by the Product or Quality
Manager Compliance with PED Complete a Final Internal and External Inspection Report including: ' 'Check' drawings that go through our Shop with the production documents. ' Each workstation initials they have witnessed or completed 'their' responsibility for the equipment, we
are self certifying. This includes Dimensions, Welds,
Testing and Painting procedures
' These Check List drawings go to our Quality Dept. for review and 'sign-off' Compliance with PED Information Included in the Final PED Package: ' Weld Procedures (ASME ' CAT. I or PED ' CAT. II)
' Welders Qualifications
' Drawings with Weld Maps
' C-R ISO Registration Certificate
' Hydrotest Reports Compliance with PED Additional items that may apply (Cat I & II): ' Calibration Certificates for Torque Wrenches and Hydrotest Gauges ' Calibration PMA ' Particular Material Appraisal required for each material on the order (Category I and II) ' Our QC Manual for Receiving and Inspection
' Instruction Manuals must be 'CE' specific.
' Category I and II require PED tags attached to
the instrument Compliance with PED Additional Requirements For Category II ' Must use PED Certified Welders ' Must have their PED Qualifications ' PED Welding Procedures must be reviewed by an EU recognized Inspection Agency Essential Information Required for the Evaluation of Applications Specifications: - Design Pressure
- Indication Range
- Vessel connection Size
- Vessel Connection Centers
- Application Environment
(Indoor or Outdoor) ' Specify LED Illumination for Water Gage Glass applications for optimum view of the level ' Specify multiple technologies for Remote Indication to maximize reliability and protect against common mode failure ' Recommend proper maintenance and routine inspection of these critical instruments General Summary Recommendations for Technology on Drum Level Instrumentation ' All piping from the drum to the water level instruments is to be insulated for the following reasons: 1. Provides safety for plant personnel 2. Increases level accuracy 3. Reduce excess condensate formation to improve instrument service life ' Piping from Drum to Level Instruments should be kept to a minimum < 2M Recommendations for Level Instrument Piping Summary Your time and attention to this information is
appreciated, along with your contributions to
Operator and Plant Safety of Power Boilers
Questions Request a copy at Reliance Boiler Trim

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