Globe Control Valves General Service Minimum Design Requirements

1.  PURPOSE – This Engineering specification defines the minimum design requirements for the supply of globe control valves in general process plant service. This specification is designed to detail the specific requirements and, when specified, shall become an integral part of the unit specification.

Globe Control Valves General Service Minimum Design Requirements

1. This engineering specification applies to general service globe control valves designed for installation in facilities engineered or operated.
2. All valves supplied under this specification shall be designed for continuous operation and according to conditions specified in the accompanying unit specifications.
3. Globe valves shall conform to this engineering specification unless the accompanying unit specification indicates otherwise. In case of a conflict, the unit specification shall take precedence.
4. This specification does not apply to ultrahigh-purity gas plants or vacuum-jacketed piping systems.
5. Valves specified using this specification are required to be suitable for 40,000 on/off cycles per year. Valves are required to operate maintenance free for a four-year duration between normal maintenance outages. A cycle is defined as a valve fully stroked from closed to open and back to the closed position.

3. RELATED ARTICLES, STANDARD AND INTERNATIONAL CODES

3.1    Engineering Articles

Standard Clean (Class SC) Inspection and Acceptance Requirements

Process Clean (Class B) Inspection and Acceptance Requirements

Oxygen Clean (Class AA) Inspection and Acceptance Requirements

Control Valve Actuators and Accessories

3.2      American National Standards Institute (ANSI)/Fluid Controls Institute (FCI)

ANSI/FCI 70-2             Control Valve Seat Leakage Classifications

3.3      The International Society for Measurement and Control (ISA)

75.02.01               Control Valve Capacity Test Procedures

75.08.01               Face-to Face Dimensions for Integral Flanged Globe-Style Control Valve Bodies

75.11.01               Inherent Flow Characteristics and Rangeability of Control Valves

75.08.05               Face-to Face Dimensions for Buttweld-End Globe-Style Control Valves

3.4      American Petroleum Institute (API)

STD 598               Valve Inspection and Testing

3.5      American Society of Mechanical Engineers (ASME)

B16.5                   Pipe Flanges And Flanged Fittings

B16.11                 Forged Fittings, Socket-Welding and Threaded

B16.25                 Buttwelding Ends

B16.34                 Valves – Flanged, Threaded, and Welding End

B31.3                   Process Piping

3.6      European Committee for Standardization (CEN)

EN 10204              Metallic products—Types of inspection documents

3.7      International Electrotechnical Commission (IEC)

60534-8-1             Laboratory Measurement of Noise Generated by Aerodynamic Flow Through Control Valves

60534-8-3            Control Valve Aerodynamic Noise Prediction Method

3.8      The International Society for Measurement and Control (ISA)

RP75.23                Considerations for Evaluating Control Valve Cavitation

DEFINITIONS

What is Globe valve? Refers to valves that can be characterized by having a linear motion of the valve stem and a body distinguished by a globular-shaped cavity around the port area. Typically, a globe valve is used in throttling service using a plug and seat arrangement that is contoured in different shapes for a variety of flow characteristics.

5. GLOBE CONTROL VALVE DESIGN REQUIREMENTS

5.1      Valve Body

1. The valve body shall be a conventional linear motion, single port removable seat, globe valve design. This specification does not allow the use of split body, dual port, off set port, three- way, or top/bottom guided designs. The valve body end connections will be flanged or weld- end, as defined in the unit specification. This specification applies typically to valve sizes DN 25 (1 NPS) and larger.
2. Body material will be identified on the unit specification.
3. Valves shall be designed for pressure-temperature ratings corresponding to the class ratings defined in ASME B16.34. The valve ASME class rating, or design pressure and temperature rating required, will be specified in the unit specification.
4. Integral flange globe style valves shall be supplied with face-to-face dimensions according to ISA 75.08.01. Buttweld end globe style valves shall be supplied with face-to face dimensions according to ISA 75.08.05 long pattern. The end connection type will be specified on the unit specification.
5. Buttweld end connections shall be according to ASME B16.25. Socket-weld end connections shall be according to ASME B16.11. Flanged valve body end connections shall be according to ASME B16.5.
6. Valves referenced for purchase under this specification will be components of a process piping system and will be designed and installed according to ASME B31.3, unless other local codes and standards take precedence. When valves are designated for use in the European Union, it is the suppliers’ responsibility to comply with all EU directives and standards and supply CE- marked equipment, as required.
7. All pressure-containing parts shall be tested to API STD 598.
8. All materials considered as pressure-containing parts are subject to proof of material certification to CEN EN 10204, Type 3.1.B. The supplier shall retain copies of these documents for a ten-year time period for possible review by Air Products.
9. All valves referenced for purchase under this specification will be new and free of casting defects. New valves are defined as valves manufactured specifically for a purchase order, or valves taken from manufacturer or distributor’s stock and not previously used. Damaged or used valves that have been restored to their original condition, and carry a new valve warranty, are not acceptable.
10. Valve body designs referenced for purchase under this specification shall have had the flow coefficient (Cv) tested and verified according to ISA 75.02.01.

5.2  Trim

1. As a minimum, trim material will be stainless steel. Alloys and other hard facing material coatings might be required, depending on application. Carbon steel trims are not acceptable.
2. Equal percent, linear, and quick-opening flow characteristics shall be the standard designs. The manufacturer’s inherent flow characteristic and rangeability shall adhere to the requirements of ISA 75.11.01.
3. Other trim configurations such as pressure-balanced, anti-cavitation, and anti-noise shall be available for applications as needed.

5.3  Stem

1. As a minimum, stem material will be stainless steel. Alloy materials might be required depending on the application.
2. The manufacturer is responsible for proper sizing and material selection of the shaft to withstand the maximum thrust generated by the valve actuator, under the service conditions described in the unit specification.

5.4  Seat Leakage

1. The leakage rate specified in the unit specification is stated as the minimum requirement. Class IV should be supplied unless the unit specification states otherwise.
2. Permitted seat leakage for general service globe control valves shall be according to ANSI/FCI 70-2, which defines the levels of leakage from Class I to Class VI.

5.5  Packing and Gaskets

1. All valve packing, gaskets, and O-rings shall be designed to operate at the ASME pressure rating for the valve. Soft goods must also meet the service conditions as stated in the unit specifications.
2. The standard stem packing for general service globe control valves is PTFE. Double PTFE v-ring or braided PTFE packing designs are acceptable. Packing type will be designated in the unit specification.
3. Two additional designs of stem packing exist for use in general service globe control valves. One design is the standard Grafoil packing, consisting of a series of laminated Grafoil rings. The second design is a live-loaded, Grafoil packing that is self-adjusting, and made up of laminated Grafoil rings with a set of spring washers to provide uniform packing pressure. Standard Grafoil packing is preferred in hydrocarbon and toxic service. Live-loaded packing is recommended for use in high-cycle or fugitive-emission service.
4. Asbestos gaskets and packing are not acceptable.
5. The bonnet area shall be designed to accept a 6 mm (1/4 in) FNPT packing purge connection in the area between the two packing sets when required. The purge connection will be called out in a note in the unit specification as “Double Lantern Ring Packing.” A 3 mm (1/8 in) connection is acceptable on smaller valves.
6. Packing gland followers shall be stainless steel at a minimum.

5.6      Bonnets

1. Screwed bonnets are not acceptable. Bonnets supplied to this specification will be bolted.
2. Bonnets will be tested according to API 598.

5.7      Installation Orientation

Valves must perform according to this specification, and with the orientation of the packing located at any angle at or above horizontal.

6.  ADDITIONAL REQUIREMENTS FOR GASEOUS OXYGEN VALVES.

Note 1:   All materials used in valves supplied for oxygen service shall comply with the following minimum requirement. Substitution of materials is only permitted with Air Products specific written approval. Metallic components shall comply with this section when the O2 concentration is > 40% and nonmetallic components when the O2 concentration is > 23.5%

Note 2:   The maximum permitted aluminum content for an alloy used in O2 service shall not exceed 2.5%.

Note 3:   All pressures listed in the following sections apply to the circuit design pressure listed on the unit specification and not the normal operating pressures.

6.1  Valve Trims

1. All valve trim materials shall be stainless steel, copper alloy or nickel alloy as called out in the unit specification and as listed below. Other metals may be suitable but are only permitted with Air Products specific written approval.
   • 304 and 316 stainless steel > 3mm (1/8 in) thick* is suitable from 0 to 13.8 bar g (0 to 200 psig)
   • 304 and 316 stainless steel > 6 mm(1/4 in) thick* is suitable from 0 to 20 bar g (0 to 290 psig)
   • Monel any thickness is suitable from 0 to 207 bar g (0 to 3000 psig)
   • Inconel 600 any thickness is suitable from 0 to 69 bar g (0 to 1000 psig)
   • Inconel 625 > 3 mm (1/8 in)* is suitable from 0 to 86 bar g (0 to 1250 psig)
2. Hard facings shall be provided when specified on the unit specification or when it is required to prevent galling of similar metals. Acceptable hard facing materials are as follows:
   • Stellite of any thickness is suitable to a maximum of 34.5 bar g (500 psi).
   • Colmonoy of any thickness is suitable to a maximum of 0 to 207 bar g (0 to 3000 psig).

Note:   *Thin parts assembled directly against other metallic parts may be evaluated based on their combined thickness.

6.2  Valve Bodies

Valve bodies shall be stainless steel, copper alloy, or nickel alloy as called out in the unit specification and as listed below. Other metals may be suitable but are only permitted with Air Products specific written approval. Occasionally carbon steel may be called for on the unit specification when the pressure is low and the O2 concentration is lower than 70%.

• • 304 and 316 stainless steel > 3 mm (1/8 in) thick is suitable from 0 to 13.8 bar g (0 to 200 psig).
  • 304 and 316 stainless steel > 6 mm (1/4 in) thick is suitable from 0 to 20 bar g (0 to 290 psig).
  • Monel any thickness is suitable from 0 to 207 bar g (0 to 3000 psig).
  • Inconel 600 any thickness is suitable from 0 to 69 bar g (0 to 1000 psig).
  • Inconel 625 > 3 mm (1/8 in) is suitable from 0 to 86 bar g (0 to 1250 psig).
  • High tensile bronze BS1400 HTB1 any thickness is suitable from 0 to 207 bar g (0 to 3000 psig).

6.3  Other Wetted Components

All other metallic components within the wetted parts of the valve shall be selected from the list in paragraph 6.2 and shall comply with the same minimum material thickness requirements. One permitted exception is that metallic valve components that are wetted but not in the flowing stream may be stainless steel at any pressure and thickness. This exception is only granted with written approval from Air Products.

6.4   Soft Parts and Lubricants

All soft parts and lubricants inside the wetted parts of valves shall be oxygen compatible and approved by Air Products. The following materials may be used without requesting Air Products approval:

1. • PTFE to 207 bar g (3000 psig)
   • Viton to 62 bar g (900 psi) for seats and 207 bar g (3000 psi) for static seals.
   • Kalrez to 207 bar g (3000 psig).
   • Kel-F81 (Unplasticized) to 207 bar g (3000 psig).
   • Graphite. The use of graphite is limited to when the graphite is totally contained and cannot shed particles into the flowing steam. Example:  Graphite packing ring in conjunction with metal wiper ring at the process end of the packing set.

6.5   Valve Construction:   

The following addition requirements apply to all valves supplied for Oxygen duty.

1. The use of slip on flanged is not permitted by Air Products on any valve in oxygen service.
2. Plating of metal surfaces in not permitted in any oxygen valves. Balanced plug designs may use spring energized plug seal to control leakage between the plug and cage. Those seals must be an oxygen compatible material and any spring used to assist the loading must be Monel. Inconel is also acceptable but is limited to 69 bar g (1000 psig). Stainless steel springs are not allowed because of the very thin spring wire cross-section.
3. All compressor recycle valves, all valves in pulsating service and all valves operating at > 4 bar g (60 psi) shall have integral plug and stem or shall have the plug back-welded to the stem.
4. The maximum noise level permitted in oxygen valves is 100 dba.

7.  ACTUATION AND ACCESSORIES

Actuation and accessory requirements for globe control valves are addressed in specification Control Valve Actuators and Accessories and the unit specification. Additional cleaning requirements will be specified in the unit specification.

8.  GLOBE CONTROL VALVE CLEANING

Cleaning requirements of all pressure-containing parts to Standard Clean (Class SC) Inspection and Acceptance Requirements, Process Clean (Class B) Inspection and Acceptance Requirements, Oxygen Clean (Class AA) Inspection and Acceptance Requirements will be defined on the unit specification.

9.  VALVE IDENTIFICATION

1. Each valve shall be supplied with a serial number or other traceable identification marking, which shall be engraved on a stainless steel nameplate. The nameplate shall also include the valve tag number from the unit specification and shall be permanently attached to the valve actuator.
2. Direction of flow arrows shall be permanently attached to the valve. The valve tag number shall be engraved on a stainless steel tag and permanently attached to the actuator mounting flange.
3. All tags and nameplates shall be stainless steel. Wire tie-wrapped tags are not acceptable. Any additional tagging requirements will be specified within the unit specification or the purchase order document.

10.  NOISE PREDICTION/ATTENUATION

1. Valves shall not be damaged when subjected to the manufacturer’s recommended noise limits.
2. The valve manufacturer shall perform a valve noise calculation using the service conditions specified in the unit specification, and shall advise the specifier if the predicted noise level exceeds valve manufacturer’s limits.
3. Noise calculated using the suppliers’ calculation technique is acceptable. When a discrepancy occurs or the predicted level is debated, the IEC 60534-8-1 method will be used. Company will be moving towards full adoption of the IEC method by the end of year 2002.
4. The unit specification may advise the manufacturer of a lower noise limit that cannot be exceeded. The manufacturer will advise the specifier if the lower noise limit specified is exceeded.
5. The valve manufacturer shall substantiate claims of aerodynamic noise attenuation capabilities according to IEC 60534-8-1.

11.  Globe Control Valves Cavitation

1. The valve manufacturer shall perform a valve calculation verifying the prediction of cavitation using the service conditions in the unit specification. The manufacturer shall advise the specifier if cavitation was predicted.
2. If cavitation is predicted, the manufacturer shall submit recommendations for the specifiers’ review, which will mitigate damage to the control valve and piping system.
3. The valve manufacturer shall be familiar with ISA RP75.23 and its recommendations of successful solutions for cavitation problems.