1. The Swagelok® SK series and AFS Multipurpose Ball Valves
Swagelok® SK series and AFS ball valves are high-pressure, high-flow ball valves for applications where high pressure (up to 6000 psig ( 413 bar)), high flow, and durability are critical. The purpose of today’s presentation is to provide an overview of the design and the performance characteristics, as well as features and benefits associated with these valves.
This presentation is best used in combination with:
MS (SK series ball valve catalog)
MS (AFS ball valve catalog)
MS E (SK series ball valve product feature card)
SS-4SKPS4-CA (SK series ball valve cut-away)

2. Presentation Overview
Product Overview
Features and Benefits
Stem Seal
Seat Seal
Product Options and Accessories
In this presentation, we will discuss an overview of this family of products. I will describe the product features and benefits, specifically focusing on the stem and seat seals, and finally I will provide you with some information on the product options and accessories. Let’s begin with an overview of these products.

3. Product Overview Working pressures up to 6000 psig (413 bar)
Temperature ratings
0 to 3020F (– 17 to 1500C)
– 40 to 2000F (– 40 to 930C)
Flow coefficients (Cv)
SK Series 0.9 to 1.4
AFS 4.0 to 13.8
316 stainless steel body and end connections
Easy to maintain
Variety of end connections
Manual and pneumatic actuation
Both the SK series and AFS ball valves can withstand working pressures up to 6000 psig (or 413 bar)
They have a wide operating temperature range of 0 to 302F (– 17 to 150C) and 40 to 200F (– 40 to 93C)
The valves are considered high-flow valves, with flow coefficients of 0.9 to 13.8.
Both have 316 stainless steel bodies and end connections, and are easy to maintain in the field.
They are available with a wide variety of end connections including female NPT, male NPT, VCO®, female ISO, female SAE/MS, as well as fractional and metric Swagelok tube fitting end connections. The end screw design allows for different end connections on the inlet and outlet.
A variety of manual and pneumatic actuation options are available. Both the AFS and SK series come standard with a black nylon directional handle. When pneumatic actuation is preferred, the valves are available with Swagelok 130 series and ISO 5211-compliant actuators.

4. Working Pressure Rating
Product Overview
SK Series
AFS
Working Pressure Rating
6000 psig
(413 bar)
Temperature Rating
0 to 302F
(– 17 to 150C)
Low-temp option: – 40 to 200F
(– 40 to 93C)
– 40 to 250F
(– 40 to 121C)
Ball Orifice
0.188 in.
(4.8 mm)
0.472 in.
(12.0 mm)
End Connection Sizes
1/4 to 3/8 in.
6 to 8 mm
3/8 to 1 in.
12 to 16 mm
Certifications 
NGV 3.1 and NGV 4.6
ECE R110
To differentiate between the two ball valves, we are going to review their parameters.
As you can see both valves are rated to a working pressure of 6000 psig (413 bar), but as we look at the temperature ratings for the valves, there are some differences.
The SK series has both a standard valve and a low-temperature option. The standard SK series valve is rated for temperatures from 0 to 302F (– 17 to 150C). The low-temperature option is rated for temperatures ranging from – 40 to 200F (– 40 to 93C).
As we look at the AFS ball valve, you can see that the temperature range for this valve is – 40 to 250F (– 40 to 121C).
The SK series has a smaller orifice than the AFS, therefore the AFS has a higher flow rate with a Cv 4.0 to The SK series has a flow rate of 0.9 to 1.4.
As mentioned, the SK series is a smaller valve with end connection sizes of 1/4 to 3/8 in. and 6 to 8 mm. For applications needing larger end connections, the AFS is available with end connection sizes of 3/8 to 1 in. and 12 to 16 mm. If there is a need for end connection sizes not published in our literature, additional end connection sizes may be available upon request.
Although the valves are very similar in design, the AFS was designed to meet the alternative fuel specifications including NGV 3.1, NGV 4.6, and ECE R110. These certifications are the most commonly accepted specifications used in the natural gas vehicle industry.
Additional size end connections available upon request.
Working pressure rating may be limited by end connection.
Materials of construction vary. See product catalog.

5. Features Directional handle O-ring stem seal Spring-loaded
Now, let us take a look at some of the features of the SK and AFS ball valves.
These valves contain an O-ring stem seal. This O-ring works in conjunction with the back-up rings to provide a leak-tight seal without the requirement of a packing adjustment.
Both valves are characterized by a 316 stainless steel floating ball, supported by spring-loaded PEEK seats. As you can see from this image, the spring-loaded PEEK seats are highlighted and the location of the seat spring is indicated by the arrow closest to the end connection. These are important features because the spring-loaded, floating ball design maintains sufficient sealing force between the seat and the ball to ensure a leak-tight seal under various operating conditions. The 316 stainless steel seat springs provide consistent force for the valve.
Later in this presentation, we will show how these components work together to provide a robust seat seal.
In addition to the seat design just mentioned, both valves have a nylon directional handle which opens and closes the valve with an easy 90° turn of the handle.
Spring-loaded
PEEK seats
Stainless steel floating ball
SK series shown

6. 316 SS Pressure-Containing Components
Packing bolt
Stem
Body
Packing bolt gasket
End screw
Both the SK series and the AFS valves were designed to withstand pressures up to 6000 psig (or 413 bar) and be compatible with many different system media. The identified pressure-containing components are all made from 316 stainless steel. This provides robust sealing, as well as broad chemical compatibility.
As you can see, there are a minimal number of components in this valve. This allows for an easily rebuildable valve. Replacement kits and instructions are available.
End screw gaskets
SK series shown

7. Stem Seal Stem thrust washer Chamfered back-up ring Stem back-up ring
Stem O-ring
Stem
Stem thrust washer
Chamfered back-up ring
Stem back-up ring
Next, we will discuss the stem seal. The components shown here work together to provide a leak-tight seal to atmosphere. This design allows for leak-tight performance without the need for adjustments. This minimizes overall maintenance costs and fugitive emissions.
The stem design of the SK series valve is constructed with a low-temperature fluorocarbon O-ring supported by a PEEK stem back-up ring as well a chamfered back-up ring made of PEEK. The chamfered PEEK back-up ring expands under high pressure, providing containment of the PTFE stem backup ring and the stem O-ring. Finally a PEEK stem thrust washer supports the stem assembly at the upper part of the stem. The thrust washer is in place to ensure that there is no metal-to-metal contact between the upper stem and the packing bolt, which could cause wear over time.
SK series shown

8. Seat Seal Seat spring Seat O-ring Seat gland PEEK seat
Seat back-up rings
Seat O-ring
The seat seal design is an integral part of the floating ball design. PEEK is a material that provides a chemical compatibility in a broad range of system fluids. The spring loading of the seats allows the floating ball to seal in both high- and low-pressure applications.
The PEEK seats are supported by a seat gland, back-up rings, O-rings, and a seat spring. This design provides a “live-loaded” seat seal, which supports the floating ball.
On the following screens you will be able to see how this live-loaded seat seal works with the floating ball.
SK series shown

9. Seat Seal SK series shown
The SK and AFS valves incorporate a “floating ball design.” A “floating ball design” means the ball is not rigidly attached to the stem, and is able to “float” downstream and back as the system pressure changes. It also allows for pressure assisted seat sealing at high pressures.
Click to actuate valve and show the stem tab into the ball slot.
With this design, the ball and stem are coupled by the tab on the stem mating with the slot in the ball. This gives the stem the ability to rotate the ball, while still allowing axial movement, or the ability to “float” when pressurized in the closed position.
Click to show the media flow and the seat movement.
When the valve is closed, the surface of the ball is exposed to pressure, which pushes the ball downstream. This pressure is contained by the two PEEK seats that allow the ball to float between them while still maintaining a seal. The springs apply a consistent force against the seat gland. This gland then transmits the force to the seat, which in turn is forced back against the ball.
The downstream spring compresses. The load on the spring supporting the upstream seat decreases. The spring begins to relax, pushing the gland and seat forward while maintaining contact between the seat and the ball.
The spring loaded seats in both the SK and AFS valves allow them to operate leak-tight consistently in applications where pressures may fluctuate between low and high pressure. These spring-loaded seats provide sealing at low pressures, particularly after the valve has been exposed to high pressure.
If the seats should wear over time, the springs still provide a consistent sealing force in low-pressure situations. In addition, when compared to valves with typical compression loaded seats, the SK and AFS valve spring-loaded seats provide a consistent and low operating torque.
SK series shown

10. Seat Seal High Pressure Low Pressure SK series shown
Finite element analysis (FEA) was used to assist in the design of the valve seat and ball interface.
Click to show low-pressure sealing.
As you can see from the load profile on the seat at low pressure, both the upstream and downstream seats seal against the ball. The red area shows the highest stress, while the green and light blue show secondary sealing.
Click to show high-pressure sealing.
As pressure increases, the seat is forced against the downstream seat. The seal is greater at high pressure as can be seen by a larger stress area shown in red. Unlike compression-loaded ball valves, the upstream seat still maintains a seal as seen here.
These components work together to provide a leak-tight seal in various operating conditions. The live-loading gives you confidence over a wide temperature and pressure range allowing these valves to be used in a multitude of applications.
SK series shown

11. Options Handles Directional Oval Metal Lock-out
Next, we will discuss some of the options for the SK and AFS valves. There are several types of handles including directional, oval, metal, and lock-out.
Both the SK and AFS come standard with a black directional nylon handle. This handle type is also available in a wide variety of colors including blue, green, orange, red, and yellow.
Both series are available with a black nylon oval handle, as well.
The SK series is available with a stainless steel directional handle, while the AFS is available with a black aluminum directional handle.
A lock-out bracket is available with either the nylon or metal directional handle.

12. Actuators - Pneumatic Rack and pinion Compact, lightweight
Operated with standard shop air
Spring return and double acting
Dual mounting available
Special service actuators
ISO 5211-compliant
When pneumatic actuation is preferred, both the SK and AFS valves are available with Swagelok pneumatic actuators. These actuators are compact and lightweight and can be operated with standard shop air. They can be ordered with either spring return or double acting actuation mode.
Swagelok offers actuators that are ISO 5211-compliant, as well as actuators that can be dual-mounted. These actuators are available for special service which include, both high and low temperatures, different materials of construction, and coatings.

13. Product Summary Working pressures up to 6000 psig (413 bar)
Temperature range from – 40 to 302F (– 40 to 150C)
Easy to assemble and maintain
Manual and pneumatic actuation
In summary, the SK and AFS valves provide a family of ball valves that can withstand working pressures up to 6000 psig (or 413 bar) with temperature ranges of – 40 to 302F (– 40 to 150C).
The construction provides you with the opportunity to rebuild and maintain the valve easily.
Many different options are available which include various handles and pneumatic actuators.