Importance of Certification Pressure Parts in Steam and Water Analysis System (SWAS):

of operator is one of the most important aspects for any . Any System must be designed considering safety aspects in mind.

In fact “Occupational Health and Safety” is on top priority for High pressure Boiler users.?

Steam and Water Analysis system () is used for online monitoring of / samples from and . These samples are at very high and . In next generation Ultra- power boilers, pressures can be as high as 350 Bar and Temperatures of superheated steam closed to 600 Deg C. In Ultra-supercritical Boilers it can be as high as 750 Deg C.

These samples hold very high energy in terms of Hydraulic pressure and Temperature. Any exposure to these samples can cause serious for human working around.

Steam and Water Analysis System (#SWAS) Package, mainly consist of two parts:

1. Mechanical Sampling System (Often called Wet Rack/ Panel)
2. Instrument or Analyzer Panel

Sampling system is designed to reduce temperature and pressure of these samples along with control of flow to Analyzers. Components of sampling system are exposed to very high Temperature & Pressure and must be designed to withstand these conditions.

These critical sample components must be certified by Authorized Inspector (AI) or Third party Inspector(TPI) to ensure:

1. Component’s Design is in line with International standards like ASME/ PED etc.
2. Materials selected properly to withstand high pressure and temperature conditions simultaneously
3. Manufacturing and Quality processes controlled

Figure#1 Indicates #components which are exposed to high pressure during operation.

These components are as below:

1. Sample Isolation and Blowdown Valves
2. Sample cooler
3. High pressure Sample Filters
4. Rod in Tube sample Pressure reducer
5. Thermal shut off Valve.?

Isolation and Blowdown valves:?

Isolation valve in Package is "First step towards safety". systems are often handling samples at very High Hydraulic Pressure and Temperatures. In some cases these samples can be very hot steam samples. System must be isolated and Lockout (Tag out) before system is inspected, maintained, cleaned or repaired. Isolation procedures must be included as a critical part of operation and maintenance manual for any sample handling system.

The aim of an isolation procedure is to:

• Isolate all forms of potentially hazardous energy (High Pressure and Temperature samples) to ensure that an accidental release of hazardous energy does not occur
• Ensure that entry to a restricted area is tightly controlled.
• Take blowdown and clean sample lines before taking SWAS Package in service.

?Result of Improper Steam Isolation in SWAS Package:?

Minimum Specification of Steam Isolation valves:

• Material Selected must be suitable to withstand high pressure and temperature of Steam
• Metal Braided grafoil gland packing rings and Gaskets to withstand high pressure and temperature of Steam
• Forge Body for high pressure as well as temperature steam application
• Sample Isolation and Blow-down valves are designed in line with ASME PTC 19.11-2008 and ASME B16.34 standards
• Non-rotating spindle design ensures easy operation
• Valves certified by Local Boiler Safety Authority like ASME (USA&Canada)/PED (Europe)/ IBR (Indian Subcontinent)/ DOSH (Malaysia) etc.?

Sample cooler:

After isolation valve second and most critical component of sampling system is Sample cooler. Sample cooler is designed to condense steam and cool high temperature samples to atmospheric temperature. All components downstream of sample cooler are designed for temperature below 50 to 60 Deg C. Main purpose of sample cooler is to efficient cooling of samples using closed circuit cooling waters so that it can be used for delicate analyzer sensors.

These sample coolers is counter flow heat exchanger with single or double helical coil in shell design. These coolers are specially designed as per PTC-19.11 OR VGB recommendations to achieve a very close approach temperature of the sample ASME D1192 requirement. "Failure of sample cooler Coil" may lead to damage to downstream components and create serious

Minimum Specification of Sample cooler:

• Material Selected must be suitable to withstand high pressure and temperature of Steam. Helical coils of sample cooler are manufactured using material like Stainless steel ( / ) OR Inconel 625 () in case of high chlorides in cooling water.
• Sample cooler must be designed as a Unfired pressure vessel like (a) ASME , Div-1 & 2 (b) PED etc. This cooler is certified by Third party design validation agency to handle high pressure & high temperature applications in Ultra-supercritical Power Boilers.
• Coolers certified by Local Boiler Safety Authority like ASME (USA& Canada)/PED (Europe)/ IBR (Indian Subcontinent)/ DOSH (Malaysia) etc.?

Sample Filter:?

Sample provides a clean , free from suspended matter. This suspended matter can clog small Tubing. Sample filter is located after sample cooler. Thus though sample temperature is reduced after sample cooling sample pressure is still high. Thus sample filter must be designed to withstand High pressure. Filter body is pressure retaining part and thus must be designed as per ASME Section VIII Div 1 & 2

Minimum Specification of Sample Filter:

• Material for sample filter must be minimum stainless steel ( / )
• Sample pressure Filter body is (a) ASME SECVIII, Div-1 & 2 (b) PED etc.
• This part must be certified by local Authorities like ASME (USA& Canada)/PED (Europe)/ IBR (Indian Subcontinent)/ DOSH (Malaysia) etc.?

Pressure Reducer:

Steam and Water analysis System (SWAS) in modern power generation plants requires precise control of flow and pressure. Modern Power plants are designed to take variable load Depending on the grid requirement. Many modern power Boiler and HRSG Manufacturers operating boiler on sliding pressure pressures. Boiler pressures often changed multiple times within a day. The SWAS operator needs to modulate the pressure reducing valve manually to maintain the desired flow to analysers.

Minimum Specification of Sample Pressure Reducer:

• Sample pressure reducer must be designed inline with ASME PTC19.11-2008 standard and must be Rod in tube type pressure reducer
• Material for this valve must be minimum stainless steel ( / )
• Sample pressure Reducer is (a) ASME SECVIII, Div-1 & 2 (b) PED etc.
• This part must be certified by local Authorities like ASME (USA&Canada)/PED (Europe)/ IBR (Indian Subcontinent)/ DOSH (Malaysia) etc.?

Thermal Shut off Valve:

Thermal shut off valve is mechanical device designed to protect downstream sample handling system components in case of sample cooling failures. In normal operation Thermal shut off valve is not exposed to high pressure as it’s located downstream of sample pressure reducer.

But, In case, cooling water to sample cooler fails this device actuates and block sample going to analyzers. As soon as it block sample it is exposed to high pressure.

Minimum Specification of Thermal shut off Valve:

• Thermal shut off valve must be designed inline with ASME PTC 19.11-2008 standard i.e. Mechanical device with Manual reset arrangement.
• It should latch in close position in case of failure of sample cooling
• Material for thermal shut off valve body must be minimum stainless steel ( / )
• Pressure retaining parts of Thermal shut off valve must be in line with (a) ASME SECVIII, Div-1 & 2 (b) PED etc.
• This part must be certified by local Authorities like ASME (USA& Canada)/PED (Europe)/ IBR (Indian Subcontinent)/ DOSH (Malaysia) etc.?

Why Third Party Certification is necessary for SWAS Component??

Safety & Plant Insurance:

• As mentioned above these are handling very high pressure & Temperature samples, through sample flows are very low any failure of this pressure part is not safe.
• Many times plant insurances are linked with certification of pressure parts.
• In many countries Boiler Safety authorities (ASME/ IBR-India/DOSH-Malaysia) don’t allow to start boiler unless certified pressure parts are used

Design Validation and Quality Control:

• In any new project, It is practically impossible for user to check and Validate design of small pressure parts in SWAS Package
• User need assurance from Authorized Inspector (AI) or Third Party Inspector (TPI) that SWAS supplier is using right design and material for critical pressure parts

Cross references for Articles:

1. Forbes Marshall Pvt. Ltd.
2. ASME Standards
3. VGB Standards
4. Indian Boiler Regulations
5. DOSH Malaysia