General Service Butterfly Control Valves Technical Requirements

1. PURPOSE – This article is about technical specification of minimum design requirements for the supply of butterfly 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.

2. General Service Butterfly Control Valves Technical Requirements

This engineering specification applies to general service butterfly control valves designed for installation in facilities engineered or operated by Air Products and Chemicals worldwide.
All valves supplied under this specification shall be designed for continuous operation and according to conditions specified in the accompanying unit specifications.
Butterfly 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.
This specification does not apply to ultrahigh-purity gas plants or vacuum-jacketed piping systems.
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, STANDARDS AND CODES

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

75.11.01 Inherent Flow Characteristic and Rangeability of Control Valves

RP75.23 Considerations for Evaluating Control Valve Cavitation

3.4 American Petroleum Institute (API)

STD 598 Valve Inspection and Testing

STD 609 Butterfly Valves: Double Flanged, Lug- and Wafer-Type

3.5 American Society of Mechanical Engineers (ASME)

B16.5 Pipe Flanges and Flanged Fittings

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

B16.47 Large Diameter Steel Flanges NPS 26 through NPS 60

B31.3 Process Piping

3.6 British Standards Institute (BSI)

BS EN 593 Industrial Valves—Metallic Butterfly Valves

3.7 European Committee for Standardization (CEN)

EN 593 Industrial Valves Metallic Butterfly Valves

EN 10204 Metallic products—Types of inspection documents

3.8 Manufacturers Standardization Society of the Valve and Fittings Industry (MSS)

SP-68 High Pressure Butterfly Valves with Offset Design

3.9 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

4. DEFINITIONS

High Performance Butterfly Valve refers to butterfly valves that can be characterized by having heavy shafts and discs and full-rated bodies with seat designs that shut off against high pressures. The shaft and disc assembly is eccentric mounted, which allows the disc to swing clear of seat area, minimizing wear and torque. The offset disc design allows the seat to be replaced without removing the shaft or disc. Valve has control capabilities beyond 60-degree rotation.

5. Butterfly Control Valves Design Requirements

5.1 Butterfly Control Valve Body

The valve body shall be a high-performance butterfly valve design. The body configuration will primarily be a flangeless wafer style for installation between pipe flanges. Lug pattern valves, when specified, will also adhere to the general requirements of this specification. Valve type will be identified in the unit specification. This specification applies typically to valve sizes DN80 (3 NPS) and larger.
Body material will be identified in the unit specification.
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.
Valve bodies shall be according to API STD 609, MSS SP-68, or EN593 (BS 5155).
Flanged body connections for valve bodies up to and including DN600 (NPS 24) shall be designed to be fitted between flanges according to ASME B16.5. Valve bodies larger than DN600 (NPS 24) shall be designed to be fitted between flanges according to ASME B16.47, Series A.
Valves referenced for purchase under this specification will be components of a process piping system that 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, supplying CE- marked equipment, as required.
All pressure-containing parts shall be tested to API 598.
Valve bodies for this application are to be classified as fully rated bodies. Fully rated valve bodies are defined as bodies that can withstand a DP equal to its ASME body rating. De-rated valve internals are only acceptable when used in conjunction with fully rated bodies and can only be used by obtaining prior written approval from Air Products. De-rated valve internals are classified as a valve that has its allowable DP limited to a value less than its fully rated valve body. This can be considered on an application basis, when for larger size valves this may prove to be an economic alternative.
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.
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.
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 Disc

As a minimum, disc material will be stainless steel. Alloys discs or stainless steel discs with hard facing material coatings might be required depending on the application. Carbon steel discs are not acceptable.
The disc shall be securely attached to the stem and positively centered in the seat.
Bidirectional shutoff is a requirement for this application. Bidirectional is defined as being able to hold full rated ASME body rating pressure in both directions with zero pressure on the opposite side. Manufacturer is permitted to have a preferred flow direction. Fully rated valves are required to be bidirectional.
The control valve’s inherent flow characteristic and rangeability shall be according to the requirements of ISA 75.11.01.

5.3 Shaft

The shaft shall be of a blowout-proof design.
One- and two-piece shaft designs are acceptable.
The manufacturer is responsible for proper sizing and material selection of the shaft to withstand the maximum torque generated by the valve under service conditions.

5.4 Seat Leakage

The leakage rate specified in the unit specification is stated as the minimum requirement. Class VI shall be supplied unless a lower level is stated as an absolute requirement in the unit specification.
Permitted seat leakage for warm butterfly 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

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 specification.
The standard stem packing for general service butterfly control valves is PTFE. Double PTFE v-ring or braided PTFE packing designs are acceptable. Packing type will be designated in the unit specification.
Two additional designs of stem packing exist for use in general service butterfly 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.
Asbestos gaskets and packing are not acceptable.
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.
Packing gland followers shall be stainless steel at a minimum.

5.6 Bearings

The top and lower bearings, including the thrust bearing (if required) shall be of the manufacturers standard design for this application. Material shall be compatible with the intended process conditions as stated in the unit specification.
Lubricated bearings are prohibited. All bearings shall be designed to withstand 40,000 cycles per year.

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.

Note 4: *Thin parts assembled directly against other metallic parts may be evaluated based on their combined thickness.

6.1 Valve Discs

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 > 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)

6.2 Valve Shafts

Shaft material shall be as defined on the Air Products unit specification.
Typically 17-4PH >3 mm (1/8 in) up to 20.7 bar g (300 psi) and Monel K500 at higher pressures.

6.3 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.
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 3000 psi

6.4 Other Wetted Components

All other metallic components within the wetted parts of the valve shall be selected from the list in paragraph 6.3 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.

6.5 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:
PTFE (Virgin and Glass Filled) to 207 bar g (3000 psi).
Viton to 62 bar g (900 psi) for seats and 207 bar g (3000 psi) for static seals.
Kalrez to 207 bar g (3000 psi).
Kel-F81 (Unplasticized) to 207 bar g (3000 psi)
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.

6.6 Valve Construction: The following addition requirements apply to all valves supplied for oxygen duty.

Plating of metal surfaces in not permitted in any oxygen valves. Spring-energized seals must be an oxygen compatible material and any spring used to assist the loading must be Monel or Inconel. Stainless steel springs are not allowed because of the very thin spring wire cross- section.
The maximum noise level permitted in oxygen valves is 95 dba.

7. Butterfly Control Valves Actuation & Accessories

Actuation and accessory requirements for general service butterfly valves are addressed in Control Valve Actuators and Accessories and the unit specification.

8. Butterfly Control Valves Cleaning

Cleaning requirements of all process wetted parts to Standard Clean (Class SC) Inspection and Acceptance Requirements, Process Clean (Class B) Inspection and Acceptance Requirements will be defined in the unit specification. Additional cleaning requirements will be specified in the unit specification.

9. VALVE IDENTIFICATION

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.
Direction of flow arrows shall be permanently attached to the valve body. The valve tag number shall be engraved on a stainless steel tag and permanently attached to the actuator mounting flange.
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

Valves shall not be damaged when subjected to the manufacturer’s recommended noise limits.
The valve manufacturer shall perform a valve noise calculation according to IEC-60534-8-3, using the service conditions specified in the unit specification, and shall advise the specifier if the predicted noise level exceeds valve manufacturer’s limits.
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. Air Products will be moving towards full adoption of the IEC method by the end of year 2002.
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.
The valve manufacturer shall substantiate claims of aerodynamic noise attenuation capabilities according to IEC-60534-8-1.

11. Butterfly Control Valves Cavitation

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.
If cavitation is predicted, the manufacturer shall submit recommendations for the specifiers’ review, which will mitigate damage to the control valve and piping system.
The valve manufacturer shall be familiar with ISA RP75.23 and its recommendations of successful solutions for cavitation problems.