Trim Selection. Selecting the right trim for your application is critical to optimizing flow. In addition to the standard 4-port trim of Master Flo choke valves, we offer a number of other styles to meet low-noise, high capacity, high pressure, well cleanup choke and other requirements. All can be engineered to provide custom flow.
Seat leakage classification through control valves
Control valves are designed to throttle flows and they are not necessary able to close 100% with no leakage.
The shut off ability has to do with type of valve. Double seated control valves have very poor shut off capabilities. In addition - the guiding, the seat material, the actuator thrust, the pressure drop and the type of fluid all play part in how well particular control valves shuts off.
Seat Leakage Classifications
There are actually six different seat leakage classifications defined by ANSI/FCI 70-2 2006 (European equivalent standard IEC 60534-4).
The most commonly used are
- CLASS IV
- CLASS Vl
CLASS IV is also known as metal to metal. It is the kind of leakage rate you can expect from a valve with a metal plug and a metal seat.
CLASS Vl is known as soft seat classification. Soft Seat Valves are those where either the plug or seat or both are made from some kind of composition material such as Polytetrafluoroethylene (PTFE) or similar.
Valve Leakage Classifications
Class I - Valve Leakage Classifications
Identical to Class II, III, and IV in construction and design intent, but no actual shop test is made. Cass I is also known as dust tight and can refer to metal or resilient seated valves.
Class II - Valve Leakage Classifications
Intended for double port or balanced singe port valves with a metal piston ring seal and metal to metal seats.
- 0.5% leakage of full open valve capacity
- Service dP or 50 psid (3.4 bar differential), whichever is lower at 50 to 125 oF
- Test medium air at 45 to 60 psig is the test fluid
Typical constructions:
- Balanced, single port, single graphite piston ring, metal seat, low seat load
- Balanced, double port, metal seats, high seat load
Class III - Valve Leakage Classifications
![Valve Valve](/uploads/1/2/6/3/126347641/386836866.png)
Intended for the same types of valves as in Class II.
- 0.1% leakage of full open valve capacity
- Service dP or 50 psid (3.4 bar differential), whichever is lower at 50 to 125 oF
- Test medium air at 45 to 60 psig is the test fluid
Typical constructions:
- Balanced, double port, soft seats, low seat load
- Balanced, single port, single graphite piston ring, lapped metal seats, medium seat load
Class IV - Valve Leakage Classifications
Intended for single port and balanced single port valves with extra tight piston seals and metal to-metal seats.
- 0.01% leakage of full open valve capacity
- Service dP or 50 psid (3.4 bar differential), whichever is lower at 50 to 125 oF
- Test medium air at 45 to 60 psig is the test fluid
Typical constructions:
- Balanced, single port, Polytetrafluoroethylene (PTFE) piston ring, lapped metal seats, medium seat load
- Balanced, single port, multiple graphite piston rings, lapped metal seats
- Unbalanced, single port, lapped metal seats, medium seat load
- Class IV is also known as metal to metal
Class V - Valve Leakage Classifications
Intended for the same types of valves as Class IV
- The test fluid is water at 100 psig or operating pressure
- Leakage allowed is limited to 5 x 10-4 ml per minute per inch of orifice diameter per psi differential
- Service dP at 50 to 125 oF
Typical constructions:
- Unbalanced, single port, lapped metal seats, high seat load
- Balanced, single port, Polytetrafluoroethylene (PTFE) piston rings, soft seats, low seat load
- Unbalanced, single port, soft metal seats, high seat load
Class Vl - Valve Leakage Classifications
Class Vl is known as a soft seat classification. Soft Seat Valves are those where the seat or shut-off disc or both
are made from some kind of resilient material such as Polytetrafluoroethylene (PTFE). Intended for resilient seating valves.
are made from some kind of resilient material such as Polytetrafluoroethylene (PTFE). Intended for resilient seating valves.
- The test fluid is air or nitrogen
- Pressure is the lesser of 50 psig or operating pressure
- The leakage limit depends on valve size and ranges from 0.15 to 6.75 ml per minute for valve sizes 1 through 8 inches
Port Diameter | Bubbles per minute | ml per minute | |
---|---|---|---|
inches | mm | ||
1 | 25 | 1 | 0.15 |
1 1/2 | 38 | 2 | 0.30 |
2 | 51 | 3 | 0.45 |
2 1/2 | 64 | 4 | 0.60 |
3 | 76 | 6 | 0.90 |
4 | 102 | 11 | 1.70 |
6 | 152 | 27 | 4.00 |
8 | 203 | 45 | 6.75 |
10 | 254 | 63 | 9 |
12 | 305 | 81 | 11.5 |
Typical constructions:
- Unbalanced, single port, soft seats, low load
![Valve Trim Selection Guide Valve Trim Selection Guide](/uploads/1/2/6/3/126347641/473166071.jpg)
Control Valve Leakage Classification - Overview
Leakage Class Designation | Maximum Leakage Allowable | Test Medium | Test Pressure | Testing Procedures Required for Establishing Rating |
---|---|---|---|---|
I | x | x | x | No test required |
II | 0.5% of rated capacity | Air or water at 50 - 125o F (10 - 52oC) | 45 - 60 psig or maximum operating differential whichever is lower | 45 - 60 psig or maximum operating differential whichever is lower |
III | 0.1% of rated capacity | As above | As above | As above |
IV | 0.01% of rated capacity | As above | As above | As above |
V | 0.0005 ml per minute of water per inch of port diameter per psi differential | Water at 50 to125oF (10 to 52oC) | Maximum service pressure drop across valve plug not to exceed ANSI body rating | Maximum service pressure drop across valve plug not to exceed ANSI body rating |
VI | Not to exceed amounts shown in the table above | Air or nitrogen at 50 to 125o F (10 to 52oC) | 50 psig or max rated differential pressure across valve plug whichever is lower | Actuator should be adjusted to operating conditions specified with full normal closing thrust applied to valve plug seat |
Related Topics
- Control Valves - Control Valve terminology, bodies, trim, flow characteristics, Cv and Kv sizing, noise, actuators and positioners
Related Documents
- Control Valves and Flow Characteristics - Relationship between control valve capacity and stem move
- NDT - Non Destructive Testing - Non-destructive testing of constructions
- Pressure-Temperature Ratings ASTM A216 Valves - Pressure and temperature ratings for Cast Carbon Steel Valves
- Steam Control Valves - Calculating Kv Values - Design of steam control valves and their Kv values
- Valve Types - Classifications of valves
- Valves - Temperature and Pressure Ratings - Temperature and pressure ratings for valves according API 6D
- Valves - Typical Operating Ranges - Types of valves and their typical operating sizes
- Valves - Typical Operating Temperatures - Operating temperatures for typical types of valves - ball valves, butterfly valves and more
- Valves for Specific Services - In case of a specific service - the choose of a valve may be simplified by following an established practice
- Valves Selection Guide - An applications guide for selecting valves
- Water Control Valves - Calculating Kv Values - Design of water process control valves and their Kv values
Tag Search
- en: control valve process seat
- es: asiento de válvula de control de proceso
- de: Steuerventil Prozesssitz
An applications guide for selecting valves
The suitability of a valve for a particular application is decided by the materials used in relation to the conveyed fluid as well as its mechanical design. The table below can be used as a valve selection guide.
Conveyed Fluid | Nature of Fluid | Valve Function | Type of Disc |
---|---|---|---|
Liquid | Neutral (Water, Oil, etc) | On/Off | Gate |
Rotary ball | |||
Plug | |||
Diaphragm | |||
Butterfly | |||
Plug gate | |||
Control valve, modulating | Globe | ||
Butterfly | |||
Plug gate | |||
Diaphragm | |||
Needle | |||
Corrosive (Acid, alkaline etc.) | On/Off | Gate | |
Plug gate | |||
Rotary ball | |||
Plug | |||
Diaphragm | |||
Butterfly | |||
Control valve, modulating | Globe | ||
Diaphragm | |||
Butterfly | |||
Plug gate | |||
Hygienic (Food, beverages, drugs etc) | On/Off | Butterfly | |
Diaphragm | |||
Control valve, modulating | Butterfly | ||
Diaphragm | |||
Squeeze | |||
Pinch | |||
Slurry | On/Off | Rotary ball | |
Butterfly | |||
Diaphragm | |||
Plug | |||
Pinch | |||
Squeeze | |||
Control valve, modulating | Butterfly | ||
Diaphragm | |||
Squeeze | |||
Pinch | |||
Gate | |||
Fibrous Suspensions | On/Off, Control valve, modulating | Gate | |
Diaphragm | |||
Squeeze | |||
Pinch | |||
Gas | Neutral (Air, Steam etc) | On/Off | Gate |
Globe | |||
Rotary ball | |||
Plug | |||
Diaphragm | |||
Control valve, modulating | Globe | ||
Needle | |||
Butterfly | |||
Diaphragm | |||
Gate | |||
Corrosive (Acid vapors, chlorine etc.) | On/Off | Butterfly | |
Rotary ball | |||
Diaphragm | |||
Plug | |||
Control valve, modulating | Butterfly | ||
Globe | |||
Needle | |||
Diaphragm | |||
Vacuum | On/Off | Gate | |
Globe | |||
Rotary ball | |||
Butterfly | |||
Solids | Abrasive Powder (Silica, etc) | On/Off, Control valve, modulating | Pinch |
Squeeze | |||
Spiral sock | |||
Lubricating powder (graphite, talcum, etc | On/Off, Control valve, modulating | Pinch | |
Gate | |||
Spiral sock | |||
Squeeze |
Related Topics
- Piping Systems - Dimensions of pipes and tubes, materials and capacities, pressure drop calculations and charts, insulation and heat loss diagrams
- Control Valves - Control Valve terminology, bodies, trim, flow characteristics, Cv and Kv sizing, noise, actuators and positioners
- Valve Standards - International standards for valves in piping systems
- Control Valves and Equipment - Sizing and dimensions of control valves & equipment in steam and condensate systems
Related Documents
- ASME - Valve Standards - An overview of the American Society of Mechanical Engineers - ASME - valve standards
- ASTM - Valve Standards - An overview of ASTM International - American Society for Testing and Materials - valve standards
- Control Valves and Flow Characteristics - Relationship between control valve capacity and stem move
- Diaphragm Valves and Diaphragm Materials - Typical diaphragm materials and their main properties when used in diaphragm valves
- Flow Coefficients - Cv - and Formulas for Liquids, Steam and Gases - Online Calculators - Flow coefficient and proper design of control valves - Imperial Units
- ISO Valve Standards - An overview of ISO - International Organization for Standardization - valve standards
- Leakage Classification of Control Valves - Seat leakage classification through control valves
- Safety Valve Standards - An survey of international safety valve standards. The most common used standards in Germany, UK, USA, France, Japan, Australia and Europe
- Slurry Transport - Minimum Flow Velocity - Avoid settling of solids in slurry transport systems with flow velocities above certain levels
- Steam Control Valves - Calculating Kv Values - Design of steam control valves and their Kv values
- Valve Abbreviations - Common US valve abbreviations used in drawings and documentation
- Valve Authority - The valve authority expresses the ratio between pressure drop across the control valve compared to total pressure drop across the whole system
- Valve Types - Classifications of valves
- Weir Diaphragm Valves - Flow Coefficients - Cv - and Flow Factors - Kv - Typical flow coefficients - Cv - and flow factors - Kv - for weir diaphragm valves