EN161 Butterfly Shut-Off Valves

Posted on June 20, 2014 by WebAdmin

EN161 is a European Standard (EN) entitled “Automatic Shut-Off Valves for Gas Burners and Gas Appliances” (Please consult the latest version of this standard for up to date information). The scope of this standard covers the overall design, construction, testing, and safety requirements for quick shut-off valves.

Although it is possible for different types of valves to conform to requirements of EN161— for example Ball or Solenoid Valves—butterfly valves that are widely used for sizes DN50 (2″ NPS) and above because of the benefits of this type of valves offers.

One benefit of butterfly valves is the “foot print” for butterfly valves is less than ball valves. Also there is a limitation on the maximum size that solenoid valves are available whereas for butterfly valves they can be manufactured up to quite large sizes with conformity to EN161 (up to DN1200).

In addition to EN 161 butterfly valves are available in “wafer” type body reducing the overall weight and material content of the valve, consequently reducing cost of manufacture. This reduction can be passed on to the customer in terms of reduced purchase price. Furthermore butterfly valves can also be easily automated using a pneumatic rotary actuator— such as a double piston rack and pinion actuator. The shut-off action can be easily fulfilled using springs in the actuator to ensure that the valve automatically closes upon signal failure. This type of actuator has the advantage of being robust, reliable, and being entirely mechanical can be used safely in hazardous zones or areas. The combination of quarter turn butterfly valve with pneumatic single acting double piston actuator also allows for quick shut off of the valves (Up to DN500 < 1second; DN600 – DN1200 < 2seconds).

To meet the tight shut-off requirements (Leak Rate A according to DIN EN 12266-1) a suitable lining material is selected according to the flowing medium and the maximum and minimum operating temperature range.

It is important to note that there is a maximum operating pressure limit for EN161 valves and this limit is dependent on the valve size.

If you have an EN161 shut-off valve enquiry, or to discuss your requirements, please contact us to discuss a suitable solution:

Trunnion versus Floating Ball Valves

Posted on June 19, 2014 by WebAdmin

Floating Ball Design

The name “floating” ball refers to the fact that the ball is suspended in the flowing medium held in position by the compression of the two elastomeric seats against it. The shaft is connected to a slot at the top of the ball which allows the ball to be driven travel through a quarter turn (90 degrees). The shaft allows for a certain amount of lateral movement of the ball that is generated from the upstream pressure acting against the ball. This small lateral movement in fact produces a load on the ball that presses it against the downstream seat. This type of ball valve design is therefore capable of bi-directional shut off.

As the nominal bore size of the ball increases, the weight of the ball also increases, and also the area subjected to the line pressure also increases. This has the overall effect of increasing the load (force) acting on the ball. There comes a point where it is no longer possible for the seats to support the ball and it is necessary to look at a different design: this where the trunnion mounted ball design comes into play.

Trunnion Ball Design

As described above, there comes a point where owing to the high value of the loading forces on the ball it becomes no longer possible for the seats to support the ball and an alternative design is required.

The trunnion mounted ball design in effect addresses this problem where in effect the shaft, ball, and trunnion act as single assembly that supports the ball instead of the seats and the seats become “floating” in a kind of reversal of the “floating ball” design. Similarly, trunnion mounted ball design is also capable of bi-directional sealing.

An advantage of trunnion ball design over floating ball is the lower operating torque of the ball. This is particularly advantageous when the ball valve is actuated because it reduce the size of the actuator and hence the overall costs of the valve actuation package. Obviously this difference becomes important when the pressure class and valve increases.

Availability of Floating Ball Size/Pressure Class

Generally speaking for floating ball design, the higher the size required, the lower the pressure class it is available for the reasons described earlier in this post. For example the largest size available is 10″ @ ANSI #150; the largest size available for is 1″ @ ANSI #2500. Trunnion is available for all sizes and for all pressure classes.

Please feel free to browse our scope of supply for ball valves and contact us if you have a requirement:

Triple Offset Butterfly Valve versus Concentric Butterfly Valve

Posted on June 12, 2014 by WebAdmin

This photos shows two butterfly valves that were installed on the SAME pipeline for the SAME service. As you can see from the photo the valve on the right did not fair as well as the valve on the left. There are significant signs of damage to the valve disc and the liner. The client complained that the valve on the right was “passing”, in other words, it was not shutting off fully and was leaking. When it was removed from the pipeline for examination, it was clear from examination why this was happening…

Why did the valve on the left perform better? This is because the valve was a triple offset butterfly valve designed for this type of “demanding” application on hydrocarbon service. It is a more robust design valve, constructed from the “correct” materials of construction for this service. Whereas a concentric rubber lined butterfly valve relies on an interference fit between the valve disc and liner, triple offset butterfly valves employ a robust metal-laminate seal installed on the valve disc that shuts off against a body seat. The triple offset geometry means that during the stroke there is no interference between the seal and seat increasing the service life of the valve. In addition triple offset valves are “fire-tested” and fully certified to comply with “fire-safe” valve standards such as API 607, API 6FA and other internationally-recognized Oil and Gas industry valve standards.

What is there to learn from this? Utility type valves, such as concentric rubber lined butterfly valves, are not designed for “demanding” oil and gas applications and in terms of technical performance are not in this league as triple offset butterfly valves.

Therefore correct valve selection is all important. In this example, the client was right to remove the valve from service and replace it with a more suitable valve.

For more information on triple offset butterfly valves, or to discuss your application, please contact us: