Engineering actuated on/off valve assemblies (AVs) has always carried challenges. One of the most acute of those challenges is the discipline gap between the valve and the actuation parts of the assembly when the valve is part of the piping package while instrumentation provides the automation. The issue is that assemblies are not currently treated as “engineered” items; they are often produced by slapping the actuator on the old (or new) valve specified by the piping requirements without much understanding of the specifics of the interactions between valve and actuator connections through the drive train (coupling). A similar challenge in control valve engineering was addressed several decades ago through the evolution of responsibilities, practices and vendor participation. It will be some time before the world knows if something similar will happen with assemblies.
AVs remain challenging today because of several factors, namely:
- Multiple different disciplines and parties are involved in all processes with varying terminologies and definitions and often shifting responsibilities in design and procurement practices;
- AV sizing data sheets lack standardization when addressing application requirements;
- A wide variety of definitions of the valve torque data exists, which influences factors and coefficients, creating ambiguous and confusing models;
- Quality valve torque data including application-specific correction factors is often missing;
- The lack of a standard approach in matching valve torque data to actuator selection contributes to under- or oversizing of the actuator;
- An underdeveloped functional safety model and certification exist that take into consideration all components of the assembly.
The WIB Actuated Valve Assembly Recommended Practice (AVRP) for part-turn automated on-off valves (S 2812-X-19) was released on June 1, 2019, and has recently taken on new importance. Results of this multi-year effort, which was led by Kees Meliefste (Dow Chemicals) and Henk Hinssen (formerly with ExxonMobil) with broad industry support has now been approved by the International Organization for Standards (ISO) Technical Committee 153. ISO/TC 153 derives an international AV assembly standard using WIB AVRP as seed material. This ensures continuous interest from all the parties traditionally involved in AV assemblies. This article seeks to address the impact of the future standard on certain existing work practices of owners/operators, engineering and manufacturing contractors and suppliers without trying to explain or analyze the technical content of the AVRP.
While actuated valves are widely used in the process industry, the AVRP focuses more practically on critical emergency shut-down valves (ESDV) or blow-down valves (BDV) because they are the most challenging, safety-critical and costly segment. Safety-related applications where these valves are most commonly used are particularly challenging when the valves are in long, stand-still mode, lying dormant for years between turnarounds but required to react and operate within seconds. Commonly used as safety instrumented system (SIS) final elements, ESDVs/BDVs require significant resources during project design and often represent a challenge in project startup as well as continued operation. This, in part, is because of the attention of the licensing bodies, which require proof of sound design and robust implementation.
From the very beginning, owners or process designers need to consider, define and clearly communicate application parameters for the valve assembly being designed. This will have a smaller impact on new capital projects where the assembly will be part of the process and control management. A more significant challenge occurs for operating facilities for which process parameters and the operational envelope for installed equipment (as well as vendor certified data) are harder to obtain. In some cases it won’t be possible at all to get these parameters or data if valve vendors did not provide certified torque data for that equipment in the past or the torque definitions vary from those in the RP. For these reasons, it’s likely the application of the RP on new projects will be seen first and then a gradual adaptation will occur for existing operating facilities during turnarounds and reliability assessment or improvement programs.
Currently, an instrument specification datasheet, based on the International Electrotechnical Commission (IEC) or International Society of Automation (ISA) standard forms, is the common medium communicating application parameters, manufacturer’s data or materials and components. This datasheet is clearly not capable today of handling all of the information on torque and other data necessary for application solutions; there is no place on the sheet to hold the necessary information elements. Even a simple visual comparison of the control valve specification and on/off valve specification forms will show that the control valve contains more information relative to the actuated valve.
WHAT THE RP PROPOSES
The RP proposes an on/off valve assembly sizing data sheet (Figure 1) with the necessary level of the detailed torque and correction factors, such as maximum allowed torque drive train (MAST) or sizing safety factor (SSF), but also has some overlap with the specification datasheet. Certainly, both owners and engineering, procurement, construction firms (EPCs) will initially struggle with the introduction of another critical engineering and design document. However, balance will eventually be found by adopting the sizing datasheet suggested in the RP or its variations, and using the data as part of the valve assembly documentation package, similar to how control valve sizing calculation sheets are often accompanying control valve specification datasheets.
One aspect of this RP adoption will be that substantial amounts of new torque and other assembly information will need to be handled for selected systems. Most owner/operators and EPCs are using one of the commercial off-the-shelf instrument design and documentation systems (IDDS). Without a doubt, their preference will be to adjust and expand the use of these systems to cover new technical data. However, this will drive a need to add valve manufacturers or assembly integrators to the pool of users, complicating an already tangled communication and information technology (IT) connectivity structure for the typical project or plant IT networks. Because of the slow pace of evolution for the popular IDDS, this may mean standalone dedicated applications are more likely to be successfully deployed for early adoption. Figures used in this article are taken from a prototype of a dedicated AV assembly sizing and selection tool created in support of the RP development.
Misuse and overuse of the AV assembly sizing safety factors have plagued the process for a long time. Introducing a method to derive an on-demand correction factor (ODCF) from objective application parameters allows tightening of the operating envelope while simplifying assembly and often reducing the actuator size and weight (Figure 2). This results in cost savings with a better understanding of the safety factors.
In addition, combined graphical representation of various torques applicable to the assembly, as defined in the AVRP, will allow a focused analysis of operational cases. An example of this is shown in Figure 3, with air torque (AT, Atmax), MAST, valve opening (VTO) and allowable flange (FLANGE) clearly relating to each other.
Another aspect of the on/off valve assembly sizing datasheet that should be closely considered in the adoption of the RP is the ownership or responsibility for the data. This assembly sizing datasheet clearly identifies where—in addition to traditional owner and process designer/EPC-provided data—different component vendors and assembly contractors’ input is necessary. Owners, EPCs and even major equipment or package vendors and suppliers are familiar with the process of using centrally managed projects or facility IDDS, but this could be a major step for assembly integrators/contractors. They will need to join the IDDS multi-discipline user environment or feed the necessary information to the general engineering contractor responsible for entering the data into the IDDS and issuing the sizing datasheet. Both practices are likely to be adopted and their use will depend on the project contractual engineering and supply responsibilities.
THE ROLE OF INTEGRATORS
Safety certification has been a norm and a standard of the day affecting all equipment and component supply chains for some time, but industry and certification bodies have struggled with the relationship between the components of the actuated valve assembly. In part, this is because, unlike typically single-sourced control valves, actuated on/off valve assembly components are usually supplied by different vendors. Individual assessment and certification of the components (valve, actuator or coupling/mounting) are not sufficient because they do not take into consideration assembly integration. A likely effect of the RP adoption will be a shift of the certification focus from the component manufacturers to the integrators, based on the manufacturer-certified data. This may result in time and cost savings by applying certification to the final engineering product.
Industry adoption of the RP is likely to have a direct business impact on the supply chain for the actuated valve assemblies. Existing integration contractors—specialized independent firms, valve or actuator manufacturers asked to provide complete packages or small specialized providers—will universally benefit from easily available standardized valve torque data. This will allow them to offer faster design, more flexibility and a wider choice of components for the assembly. However, openly and easily available certified valve torque data also will lower the entry barriers for new players into the area of integration, which will increase competition and give owners/operators a wider choice of assembly suppliers.
For practical reasons, the initial RP scope was limited to the pneumatically actuated, part-turn valves. However, industry interest and support may drive continued expansion with the working group to look into electrical actuators to be added to the RP in the next 12 months. Also, further expansion of the RP is likely for hydraulic actuation, especially in the areas of testing, ODCF testing and certification.
Past experience with the adoption of the new engineering and technology practices shows that it likely will take several years to see if the RP will be successfully adopted by the industry or if the search for a perfect solution will continue. In the first year or two, there’s likely to initially be an in-depth internal analysis and review by the major owner/operators, which will need to adopt and require their contractors to apply the RP. At the same time, valve vendors will be looking at availability and quality of the torque data based on the RP definitions and testing and collecting this information where it’s not available. A capital project of medium size is likely to be used by an owner as a proving ground for the RP use followed by the “lessons learned” for which the benefits and costs of the RP application will be assessed. Project start-up experience as well as assessed impact on the reliability of the delivered facility will be major considerations along with the added project costs. Still, the benefits of improved safety and reliability are likely to outweigh the costs, which should not be high, anyway, since these improvements are applied early in the engineering and design phase of the lifecycle.
It is still early to see what twists and turns the road to the industry adoption of the automated valve RP will take, but it is sure to be an interesting path.