For fixed orifice double regulating valves, a minimum of 5 pipe diameters of straight pipe (without intrusion) should be installed upstream of the orifice plate, and a minimum of 2 pipe diameters of straight pipe are required downstream of the valve
Minimum corrosion allowance for stainless steels is 0.8 mm
Minimum corrosion allowance of 1.5 mm shall be provided for carbon steel material
The piping material selection process is a critical step in the design of any piping system . The goal is to choose materials that ensure the safe, reliable, and cost-effective transport of fluids while withstanding the operating conditions and environmental factors . Here’s a detailed explanation of the process:
- Define Service Requirements:
- Fluid Type: Identify the fluid(s) to be conveyed, including their chemical composition and physical properties .
- Operating Conditions: Determine the operating temperature, pressure, and flow rate ranges .
- Codes and Standards: Identify applicable codes, standards, and regulations (e.g., ASME B31.3, B31.1, API standards) .
- Determine Material Properties Required:
- Corrosion Resistance: Select materials resistant to internal and external corrosion based on the fluid’s corrosivity and the external environment .
- Strength and Ductility: Ensure materials have adequate tensile strength, yield strength, and ductility to withstand operating pressures and mechanical stresses .
- Temperature Resistance: Select materials that maintain their strength and integrity at the operating temperature range, considering creep, embrittlement, and thermal expansion .
- Weldability: If welding is required, choose materials with good weldability to ensure sound joints .
- Erosion Resistance: For abrasive fluids or high velocities, select materials with good erosion resistance .
- Thermal Conductivity: Consider thermal conductivity for heat transfer applications or to prevent overheating or freezing .
- Fatigue Resistance: For systems with cyclic loading, select materials with good fatigue resistance .
- Evaluate Material Options:
- Carbon Steel: A common and cost-effective material for many applications, but susceptible to corrosion in some environments .
- Stainless Steel: Offers excellent corrosion resistance and high-temperature strength, suitable for corrosive fluids and high-temperature services .
- Alloy Steel: Used for high-temperature, high-pressure, or specialized applications requiring enhanced strength, creep resistance, or corrosion resistance .
- Non-Ferrous Metals: Copper, aluminum, and nickel alloys are used for specific applications based on their unique properties (e.g., high thermal conductivity, corrosion resistance) .
- Plastics: PVC, CPVC, PP, PVDF, and other plastics are used for corrosive fluids, low-pressure applications, and deionized water systems .
- Consider Fabrication and Installation Requirements:
- Welding: Select materials that can be easily welded using standard welding procedures .
- Formability: Consider the material’s formability for bending, threading, and other fabrication processes .
- Availability: Ensure that the selected materials are readily available in the required sizes and forms .
- Assess Cost:
- Material Cost: Compare the cost of different materials, considering both the initial cost and the long-term cost of maintenance and replacement .
- Fabrication Cost: Consider the cost of welding, forming, and other fabrication processes .
- Installation Cost: Evaluate the ease of installation and any special requirements (e.g., specialized welding procedures, supports) .
- Check Industry Standards and Regulations:
- ASME B31.3: Specifies material requirements for process piping .
- ASME B31.1: Specifies material requirements for power piping .
- API Standards: Provide guidelines for material selection in the petroleum and natural gas industries .
- Local Regulations: Ensure compliance with local building codes and environmental regulations .
- Make Final Selection:
- Document the Selection Process: Document the rationale for selecting the chosen materials, including the factors considered and the alternatives evaluated .
By following these steps, engineers can select the most appropriate piping materials for a given application, ensuring the safety, reliability, and longevity of the piping system .
To select a valve, follow these steps while considering the service conditions, valve functions, and cost :
- Determine the Valve Function: Decide if the valve will primarily be used for on/off control, throttling, preventing backflow, or specialty purposes such as pressure relief . Different valve types are better suited for specific functions .
- Identify Service Characteristics:
- Fluid Type: Determine if the fluid is a liquid, gas, steam, slurry, or solid .
- Fluid Properties: Identify if the fluid is clean, dirty, abrasive, corrosive, viscous, or hazardous .
- Pressure and Temperature: Determine the operating pressure and temperature ranges .
- Consider Valve Characteristics: Evaluate application and structural characteristics to ensure proper installation, repair, and maintenance .
- Assess Operation and Maintenance Requirements:
- Fire Resistance: Determine if fire-safe features are needed .
- Operability: Consider the required speed of operation (e.g., quarter-turn, multi-turn) and actuation method (manual, electric, pneumatic, hydraulic) .
- Leak Tightness: Determine acceptable leakage rates (internal and external) .
- Maintainability: Consider ease of access for maintenance and replacement .
- Evaluate Valve Types:
- Gate Valves: Suitable for on/off service with minimal flow restriction .
- Globe Valves: Used for throttling and on/off service, but with higher flow restriction .
- Ball Valves: Provide quarter-turn on/off operation with low-pressure drop .
- Butterfly Valves: Compact and lightweight, suitable for on/off and throttling of large flows .
- Plug Valves: Offer quarter-turn on/off operation, often used for diverting flow .
- Diaphragm Valves: Suitable for corrosive or contaminated fluids .
- Check Valves: Prevent backflow in a piping system .
- Consider the Cost: Evaluate not only the initial cost of the valve but also the installation, maintenance, and lifecycle costs .
- Check the valve size: Proper valve sizing is crucial for optimal performance. Use valve flow coefficient (Cv) calculations and consult valve manufacturers’ data to determine the correct size .
Gate valves are classified based on the type of disc, body-bonnet joint, and stem movement . Here’s a breakdown:
I. Based on Disc Type:
- Solid Wedge Gate Valve: This is the most common and basic type, known for its simplicity and strength . It’s a single, solid piece and suitable for most fluids and turbulent flow .
- Flexible Wedge Gate Valve: This has a one-piece disc with a cut around the perimeter to provide flexibility . This design is better for thermal expansion and prevents thermal binding, often used in steam systems .
- Split Wedge (Parallel Disc) Gate Valve: It has two solid pieces held together by a mechanism . This allows each disc to adjust to the seating surface and is suitable for noncondensing gasses and liquids .
II. Based on Body-Bonnet Joint:
- Screwed Bonnet: This is a simple, inexpensive design .
- Bolted Bonnet: This is the most common type, using a gasket to seal the joint .
- Welded Bonnet: It’s a design where disassembly is not required, and it’s lighter than bolted bonnets .
- Pressure-Seal Bonnet: Used for high-pressure and high-temperature applications, where increased pressure improves the seal .
III. Based on Stem Movement:
- Rising Stem (Outside Screw and Yoke – OS&Y): The stem rises when the valve is opened, giving a visual indication of the valve position . The stem threads are outside the valve, protecting them from the fluid .
- Non-Rising Stem (Inside Screw): The stem does not rise or lower; instead, it rotates, making it suitable for tight spaces . The stem threads are exposed to the fluid .
Additional Types:
- Knife Gate Valve: This is designed with a sharp edge to cut through thick fluids and slurries, often used in industries like mining and paper .
- Through-Conduit Gate Valve: This type has a gate that’s fully enclosed when open, which is designed to maintain a smooth, uninterrupted flow path. It’s commonly used in pipelines where pigging is required .
I. Purpose
- To ensure that all piping materials received at the job site conform to the specified requirements of the project and ASME B31.3
- To establish a system for verifying material identity, quality, and documentation
- To prevent the use of non-conforming materials in the piping system
II. Scope
This procedure applies to all piping materials, including pipes, fittings, flanges, valves, gaskets, bolts, and other components used in the construction of piping systems
III. References
- ASME B31.3, Process Piping
- ASME Section II, Materials
- Project Piping Material Specification
- Approved Piping Drawings and Material Take-Offs (MTOs)
- Purchase Orders
- ASTM Standards (as applicable to specific materials)
- Company Quality Control Manual
IV. Responsibilities
- Procurement Department: Responsible for ensuring that purchase orders accurately reflect the project’s material requirements
- Receiving Inspector: Responsible for performing the receiving inspection in accordance with this procedure
- Quality Control (QC) Engineer: Responsible for overseeing the receiving inspection process and resolving any non-conformance issues
- Material Controller: Responsible for maintaining material traceability and storage
V. Procedure
A. Pre-Receiving Activities
- 1. Review Documentation: Before material arrives, the Receiving Inspector shall review the Purchase Order, Material Requisition, Piping Material Specification, and approved drawings to understand the material
- 2. Prepare Inspection Area: Ensure a designated receiving area is available with adequate lighting, measuring tools, and access to relevant specifications
- 3. Obtain Approved Vendor List: Verify that the material supplier is an approved vendor per the project’s quality control requirements.
B. Receiving Inspection Steps
1. Visual Inspection:
- Verify Packing List: Check the packing list against the purchase order to confirm the correct quantity and description of materials received
- Inspect for Damage: Carefully examine all materials for any signs of damage during shipping, such as dents, bends, corrosion, or broken packaging.
- Document any damage on the receiving report and notify the supplier
- Check for Proper Marking: Verify that each item is clearly and legibly marked with the correct material grade, size, schedule, and heat number.
- Markings should comply with applicable standards (e.g., ASME, ASTM)
2. Material Verification:
- Review Material Test Reports (MTRs): Obtain and review the MTRs (also known as Certified Material Test Reports or CMTRs) for each material lot
- Compare MTRs to Specifications: Verify that the chemical composition, mechanical properties (tensile strength, yield strength, elongation), and heat treatment listed on the MTRs meet the requirements of the applicable material specification (e.g., ASTM A106 Grade B, ASTM A105) and the project piping material specification
- Verify Traceability: Ensure that the heat number on the MTR matches the heat number marked on the material
- This confirms traceability of the material back to its origin
- Positive Material Identification (PMI): For critical applications or materials susceptible to mix-ups (e.g., alloy steels), perform PMI using a portable spectrometer to verify the material’s chemical Document PMI results
3. Dimensional Verification:
- Check Dimensions: Using calibrated measuring tools (e.g., calipers, tape measure), verify that the dimensions of the received materials (pipe diameter, wall thickness, flange dimensions, fitting dimensions) conform to the specified standards and the project drawings
- Verify Wall Thickness: Use ultrasonic thickness testing to verify the wall thickness of pipes and fittings, especially for corrosion-resistant alloys.
4. Specific Component Checks:
- Pipes: Check for straightness, ovality, and surface defects
- Fittings: Verify the angle, radius, and end preparation (e.g., bevel angle for welding
- Flanges: Check flange face finish, bolt hole alignment, and dimensions
- Valves: Verify valve type, pressure rating, end connections, and operator type. Check for smooth valve operation
- Bolting: Verify bolt diameter, length, material grade, and thread
- Gaskets: Check gasket type, size, and material compatibility with the intended
5. Documentation:
- Complete Receiving Inspection Report: Document all inspection results on a receiving inspection report, including the purchase order number, material description, quantity inspected, inspection date, inspector’s name, and any discrepancies or non-conformances
- Attach MTRs: Attach copies of the MTRs to the receiving inspection
- Maintain Records: Maintain a file of all receiving inspection reports, MTRs, and related documentation for future
C. Non-Conformance Handling
- 1. Identify Non-Conformances: Any material that does not meet the specified requirements shall be identified as non-conforming
- 2. Segregation: Segregate non-conforming materials from conforming materials to prevent accidental use
- 3. Notification: Notify the QC Engineer and Procurement Department of the non-conformance
- 4. Disposition: The QC Engineer will determine the appropriate disposition of the non-conforming material, which may include:
- Return to Supplier: Return the material to the supplier for replacement or credit
- Repair: Repair the material, if possible, and re-inspect to verify conformance
- Use-as-is: Accept the material “as-is” with a deviation, if it is determined that the non-conformance does not affect the safety or functionality of the piping system. This requires approval from the Engineering Department and the client, if
- 5. Documentation: Document the non-conformance and the resolution on a Non-Conformance Report (NCR)
D. Material Storage and Handling
- Proper Storage: Store materials in a clean, dry, and secure area to prevent damage or deterioration
- Material Identification: Maintain material identification throughout storage and handling
- Handling Procedures: Use proper lifting and handling equipment to prevent damage to materials
- Inventory Control: Implement an inventory control system to track the location and status of all piping materials
VI. Acceptance Criteria
- Materials are accepted if they meet all the requirements of this procedure, the applicable material specifications, and the project piping material
- All documentation is complete and accurate
- There are no unresolved non-conformances
VII. Training
All personnel involved in the receiving inspection process shall be trained on this procedure and the relevant material specifications
VIII. Records
- Receiving Inspection Reports
- Material Test Reports (MTRs)
- Non-Conformance Reports (NCRs)
- Purchase Orders
- Material Requisitions
- Calibration Records for Measuring Equipment
- PMI Reports
This comprehensive procedure ensures that all piping materials are thoroughly inspected upon arrival at the job site, minimizing the risk of using non-conforming materials and ensuring the integrity of the piping system
Remember to adapt this procedure to your specific project requirements and company standards.
I. Purpose
- To verify the integrity and leak-tightness of the constructed piping system before it is put into service
- To ensure compliance with ASME B31.3 code requirements
II. Scope
- This procedure applies to all new piping systems and modified piping systems within the specified facility or project
- It covers hydrostatic and pneumatic testing methods
III. References
- ASME B31.3, Process Piping
- Project Piping Specifications
- Approved Piping Drawings and Isometrics
IV. Responsibilities
- Piping Engineer: Responsible for determining the test pressure, test medium, and any special testing requirements
- Construction Supervisor: Responsible for ensuring that the piping system is properly prepared for testing, including adequate supports and restraints
- Quality Control Inspector: Responsible for witnessing and documenting the pressure test
- Test Personnel: Responsible for performing the pressure test in accordance with this procedure
V. Prerequisites
- All piping fabrication and installation must be complete and inspected
- All welds must be visually inspected
- Piping system should be supported per the design requirements
- Temporary supports may be needed to accommodate the weight of the test fluid
- All components, including valves, fittings, and specialty items, must be properly installed and tightened
- The piping system must be clean and free from debris
- All connections not subject to the pressure test must be disconnected or isolated using blinds or other suitable methods
- Pressure gauges must be calibrated and certified
- Safety relief devices must be installed or provisions made to prevent over pressurization
- All personnel involved in the test must be trained and familiar with this procedure and potential hazards
VI. Test Medium
- Hydrostatic Test: Potable water is the preferred test medium. If water could damage the system or cannot be used due to freezing, a suitable non-toxic liquid with a flash point above 120°F (49°C) may be used
- Pneumatic Test: Clean, dry compressed air or nitrogen is used
VII. Test Pressure
- Hydrostatic Test Pressure: Calculated per ASME B31.3, para. 345.4.2
The test pressure shall be 1.5 times the design pressure multiplied by the ratio of the allowable stress at the test temperature to the allowable stress at the design
Globe Valve Types based on Body Bonnet Connection
Screwed bonnet: This is the simplest design available and it is used for inexpensive valves.
Bolted-bonnet: This is the most popular design and used in a large number of globe valves. This requires a gasket to seal the joint between the body and bonnet.
Welded-Bonnet: This is a popular design where disassembly is not required. They are lighter in weight than their bolted-bonnet counterparts.
Pressure-Seal Bonnet: This type is used extensively for high-pressure high-temperature applications. The higher the body cavity pressure, the greater the force on the
gasket in a pressure -seal valve.
Application of Globe valve
Globe Valves are used in the systems where flow control is required and leak tightness is also important.
It used in high-point vents and low-point drains when leak tightness and safety are major concerns. Otherwise, you can use a gate valve for drain and vent.
It can be used in Feed-water, chemical, air, lube oil and almost all services where pressure drop is not an issue
This valve is also used as an automatic control valve, but in that case, the stem of the valve is a smooth stem rather than threaded and is opened and closed by lifting action of an actuator assembly.
Advantages
Better shut off as compared to gate valve
Good for frequent operation as no fear of wear of seat and disk
Easy to repair, as seat and disk can be accessed from the valve top
Fast operation compares to gate valve due to shorter stroke length
Usually operated by an automatic actuator
Disadvantages
High head loss from two or more right-angle turns of flowing fluid within the valve body.
Obstructions and discontinuities in the flow path lead to a high head loss.
In a large high-pressure line, pulsations and impacts can damage internal trim parts.
A large valve require considerable power to open and create noise while in operation.
It is heavier than other valves of the same pressure rating.
Costlier compared to the gate valve
Depending on the type of body there are three types of globe valves;
- Z types
- Y types
- Angle Types
Z types Globe Valve
The simplest design and most common type is a Z-body. The Z-shaped partition inside the globular body contains the seat. The horizontal seating arrangement of the
seat allows the stem and disk to travel at a perpendicular to the pipe axis resulting in a very high-pressure loss.
The valve seat is easily accessible through the bonnet which is attached to a large opening at the top of the valve body. Stem passes through the bonnet like a gate
valve.
This design simplifies manufacturing, installation, and repair. This type of valve is used where pressure drop is not a concern and throttling is required.
Y types Globe Valve
The Y-type design is a solution for the high-pressure drop problem in Z-type valves. In this type, seat and stem are angled at approximately 45° to the pipe axis. Y-body valves are used in high pressure and other critical services where pressure drop is concerned.
Angle types Globe Valve
Angle globe valve turns the flow direction by 90 degrees without using an elbow and one extra pipe weld. Disk open against the flow. This type of globe valve can be
used in the fluctuating flow condition also, as they are capable of handling the slugging effect.
Stainless steels may be classified by their crystalline structure into four main types: austenitic, ferritic, martensitic and duplex
Difference between 304 and 316 stainless steel?
The simple answer is 304 contains 18% chromium and 8% nickel while 316 contains 16% chromium, 10% nickel and 2% molybdenum. The molybdenum is added to help resist corrosion to chlorides (like sea water and deicing salts)
Stress Analysis
- Permissible load variation is determined as the ratio of (Travel x Spring rate / Load ) based on max. operating condition.
- Cold Load = Hot Load + Movement x Spring Rate (For pipe movement up)
- Cold Load = Hot Load – Movement x Spring Rate (For pipe movement down)
- the load variability shall be up to 25% throughout the total travel. However, for critical systems such as piping connected to pumps, compressors, reboilers, etc. lesser load variation is required to meet the allowable load requirements.
- if the load variation exceeds the allowed value, in the same load range selects a spring with lower spring rate. Else, select higher size spring.
Strainers
- If the application requires that the system has to run continuously and cannot be shut down, then the only real choice is a duplex basket strainer.
- If a vertical installation is planned, a Y-Strainer is the one that will work. Y-Strainers can be installed either vertically or horizontally. A basket strainer must be installed horizontally.
For Cold Service Bolting torque to develop 70% Bolt Yield Stress at Nut Factor, K=0.16 (Nut Factor based on lubricant used)
Bolting torque to develop 50% Bolt Yield Stress at Nut Factor, K=0.16 (Nut Factor based on lubricant used)
if the vessel is protected by multiple relief devices, then one relief device must be set no higher than the MAWP but the others can be set as high as 105% of the MAWP.
Relief Valves
– The required relief area for two-phase flow is typically two to ten times the area for single-phase flow.
– For spring-operated relief valves, small amounts of leakage start to occur at 92–95% of the set pressure.
– A relief devices over-pressure is the pressure increase over its set pressure, usually expressed as a percentage of the set pressure. Pop-acting relief valves do not immediately open completely (to 100% lift). Sufficient over pressure is necessary to achieve full lift.
– if the vessel is protected by multiple relief devices, then one relief device must be set no higher than the MAWP but the others can be set as high as 105% of the MAWP.
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