Engineered with the end user in mind

The design of the valve in consideration of assembly, maintenance, and repair

The control valve landscape has been relatively unchanged for the last 50-plus years. Globe valve OEMs have rolled out different trim variations in an attempt to manage cavitation, noise, fugitive emissions, and other adverse operating conditions, but the general design principle is largely unchanged. The same applies for ball valves, butterfly valves, and other valve types that are ideally suited to shutoff functions, but which are sometimes pressed into service for process control.

The Shutter Valve™ is a radical departure in form and function, from all of the above listed valve types; it will require unique classification in ISA and ASME valve standards.

Challenge
As we have described elsewhere, there are different types of barriers to the adoption of new technologies, and these must be addressed by product design and other strategies.

The Clarke Valve™ mission is “to continue to innovate and develop valves that customers, technical personnel, and engineers love to use,” which requires us to make the Shutter Valve readily understandable not only to buyers, but to the operators and maintenance teams who will be responsible for installing and servicing the Shutter Valve over its lifetime.

Solution
From the initial concept of the Shutter Valve through to the ongoing R&D and design iterations, Clarke Valve’s engineering team has designed the valve for ease of assembly, maintenance, and repair. Every Shutter Valve is sized and manufactured for zero modification installation with existing piping schedules and face-to-face dimensions. And, little or no additional training is required for operators or technicians to maintain a Shutter Valve, once installed. Every valve comes with a bill of materials and a simple diagram describing assembly and maintenance procedures.

We achieved our goal of simplified assembly of the Shutter Valve with the ingenious design of the ring gear, integral arms, and valve petals. The hub design of the ring gear dictates that it must go on the bottom, followed by the arms, and then the petals. Each of the arms is designed to ensure that it can only go into the ring gear one way. Likewise, each petal can only fit onto the arm and the guide pins in the valve body in the proper orientation. This prevents untrained personnel from making a critical assembly error.

 

Figure 1: Although the internal mechanism of the Shutter Valve represents a departure from existing control valve designs, the components fit together intuitively without any special training or tools required. As described above, the ring gear, integral arms, and valve petals are designed to only allow assembly in one manner, preventing improper alignment of the components during maintenance or inspection.

There are no special tools required to extract or install the petals or the arms. The entire valve assembly can be removed and replaced by hand, once the bolts on the valve body and bonnet have been removed. The insertion points for each element are machined to a sufficiently precise tolerance to prevent play or instability, but still allow for hand assembly with minimal pressure.

Over time, Clarke Valve has made modifications to the design of the arms and petals to make the Shutter Valve even simpler to assemble and service. Previously, there were 22 pieces comprising the valve mechanism, including 6 control arms (2 for each petal), 6 pins and 6 retaining rings, 3 petals, and 1 ring gear. The evolution of our design and the replacement of the linkages with integral arms has effectively reduced the number of valve mechanism parts to 7, including 3 petals, 3 arms, and 1 ring gear.

Figure 2: The design of the Shutter Valve has been adapted and simplified even further, over time. The original design (left) featured linkage arms with 2 pins and 2 retaining rings for each of the 3 valve petals. The current design (right) uses 3 integral arms that connect each valve petal to the ring gear and allow the petals to pivot inward and outward, as the valve opens and closes. The result is a rugged, streamlined design that uses 7 parts, instead of 22.

The Clarke Valve design philosophy also carries over to our selection of the soft goods that help to ensure tight shutoff in every valve. The O-rings for the valve body and bonnet  and the stem seals are all commonly available, off the shelf sizes, and can be replaced by hand.

The seals that form the interlocking rib and seal combination between the 3 valve petals are provided as part of the Spares Kit for every valve, and can be removed by hand or with the aid of a flat-head screwdriver. Again, no special tools are needed. New seals easily snap into place with hand pressure, once the old seal has been removed. Depending upon the valve application, these seals are either made from elastomer or PTFE.

The Shutter Valve bonnet was also designed to reduce the need for ongoing maintenance, unlike the stem seals of globe valves, butterfly valves, and other common valve types. In its current configuration, the Shutter Valve eliminates the live loading that occurs with the packing in these other valve types. The spring activated seals and bearings of the Shutter Valve are held in the optimum sealing position by the bonnet itself. This eliminates the need to progressively tighten any followers and potentially increase the torque required for stem movement/valve operation. In future design iterations, we may explore live loading. But, at present, the Shutter Valve bonnet design outperforms existing stem sealing methods for other valve types.

Figure 3: The design of the stem packing and bonnet of the Shutter Valve have resulted in a zero-maintenance sealing solution. Unlike other control valves that require live loading, the bonnet of the Shutter Valve and a spring energized seal at the top of the valve packing apply all the necessary loading to the O-rings and bearings, to ensure an industry leading seal that allows 97% less emissions/leakage than other “low emissions” control valves.

 

Results
By focusing on an intuitive design for the valve mechanism, using off-the-shelf seals, and matching existing face-to-face dimensions for globe control valves, Clarke Valve has engineered the Shutter Valve to be a superior plug-and-play replacement, that is easy for technicians to service and re-assemble.

Figure 4: The Spare Parts Kit for each Shutter Valve provides step-by-step visual instructions and clearly labeled parts. No training or specialized tools are required, when an end user or their service provider performs scheduled maintenance on the Shutter Valve.

The unique geometry of the Shutter Valve and its significantly lower torque requirements means that it can replace a globe valve with comparable flow rate (CV), but with a 50% to 80% reduction in weight and overall footprint. This size and weight savings reduces the labor and time needed to install or replace a Shutter Valve, conferring still further efficiency benefits to the industrial facility that chooses to deploy the Shutter Valve.