Valve MAST (Maximum Allowable Stem Torque): Its Relevance and Use in Valve Automation

One of the most important criteria when performing calculations for sizing of automated and manually-operated valves is considering the valve’s MAST value. The MAST value is the Maximum Allowable Stem Torque, defined as the greatest torque to which a valve stem can be subjected to during operation without mechanical failure.

Historically, its relevance was somewhat reduced in the valve and actuation industry, especially when it came to actuator sizing. Even today, you may be hard-pressed to find it included in sizing procedures in any manufacturer’s standard catalogue since this information is usually considered proprietary to design. However, as assets age and failure history is established, this value’s importance and demand for accuracy have adopted a more influential role in actuator sizing today.

Failure to identify, select, and size inclusive of the MAST value usually results in a partial or full shearing of the valve stem causing anything from valve leakage to complete loss of control. In some cases, it is not necessarily shearing that occurs but rather deflection during operation. The cause of this deflection originates from the selected stem material being too soft to withstand the applied forces to the disc, ball, or plug. Unfortunately, this discrepancy yields a chronological accelerated wear of the sealing surfaces which ultimately gives way to premature leakage and accelerated valve failure. The valve, and its level of importance in the application, determine the severity of the failure’s outcome. It is important to understand that there is currently no regulation by API (American Petroleum Institute) that requires manufacturers to publish their MAST values or “raw” torque values, despite mutual agreement throughout the industry by valve experts and engineers that such information is essential to actuator sizing and lifetime valve performance.

“Raw” torque values refer to the valve torques that have not been inflated by a manufacturer’s internal safety factor (which is usually added to account for manufacturing tolerances). In most cases this all boils down to the repeatability of each manufacturer’s manufacturing process and various checkpoints for quality control. Most manufacturers have very predictable manufacturing tolerances; however, they elect to omit the safety factor from published torque data. This exclusion is the primary reason why MAST values are exceeded. Excessive torque at the stem when sizing actuators will create a need to consider changing stem material. Specifying a higher yield stem material will prevent deflection or in the worst-case complete valve failure due to sheering. There are many different factors that can affect stem material selection and design in valves. Whether butterfly valves, ball valves, or plug valves, the customer or EPC provides the application conditions and, in turn, the valve manufacturer or automation supplier recommends a product that meets the provided conditions. Factors that may affect stem material selection are pressure class, process media, environmental factors, and client classification requirements.

Since valve manufacturers and distributors usually stock only the most popular valves to reduce inventory costs and maintain a high level of turnover, valves with uncommon body, disc, and stem materials are typically only produced on a machine-to-order basis. Therefore, delivery of these products can range anywhere from 26-48 weeks with cost variances of four to five times the average. If the manufacturer does not state the provided values are raw, it is imperative for one to seek clarification for this added multiplier. In short, ask questions! Ensuring that this base torque value for the valve excludes a safety factor is of the utmost importance for the following reasons: 1) preventing a multiplication of safety factors and oversizing of the actuator and 2) forcing an unnecessary upgrade to the stem and disc material.

Some of the most common stem materials are listed below in increasing order in terms of MAST as well as cost impact:

  • 316/316L SS
  • 17-4 PH SS
  • Monel K-500
  • Inconel 718

It is crucial to consider safety factors from both the client-driven requirements and the built-in margin from the manufacturer. In doing so there will be instances where combinations of the above must be utilized. Even when MAST values have been identified, failure to confirm the manufacturer’s published numbers can drive up costs and lead times exponentially due to misinterpreted data. Correctly interpreting manufacturer’s data, identifying red flags, partnering with experienced automation groups, and having strong relationships with valve suppliers are all keys to ensuring that an automated valve assembly’s configuration is mechanically correct and cost-effective.

For more information or if you need assistance with valve automation contact:

Supreme Integrated Technologies

Houston:              281 822 5000

Website:              www.supremeintegratedtechnology.com

Blog Authors: Chris Sarro & Jacob Shoesmith

10.2019


What is an Integrator? The Top Reasons Companies are Making a Switch to Single-Source Suppliers for Capital Projects

Integrators have become the supplier of choice for capital projects in terms of turnkey systems design. Traditional suppliers, such as distributors, have vast inventory but often lack the technical understanding of a system. Manufacturers can create project-specific components but, like distributors, lack the in-depth knowledge to develop and execute a turnkey, fully integrated solution. To help paint a picture of this relationship, consider the following: asking a goldfish to fly is no different than asking a bird to swim. Each has a different set of skills and the communication between the two is essentially nonexistent. True integrators overcome this challenge by being proficient in various technical disciplines (hydraulics, pneumatics, electronic controls, structural design), thus positioning them strategically to pull these technologies together into one turnkey package.

Traditionally, most customers will go to one supplier for their actuators, another for their controls, a third for their automation, and so on. This entails numerous contacts and accounts to manage, not to mention the documentation and administrative costs associated with each account. Utilizing an integrator significantly reduces the human resources needed to manage their project and can save thousands, sometimes millions, of dollars in capital expenditures. Also, very few suppliers can design and build a turnkey system to a level that is required by many in the deep-water, subsea, civil, and military markets. It takes a comprehensive technical understanding across multiple engineering disciplines to successfully integrate hydraulics, structural components, and electronic controls into one package. As previously mentioned, most in the industry source out various parts of the system to multiple vendors, each of whom has very little knowledge of the products and services provided by the other suppliers. Therefore, the interface required to compose multiple packages into one system becomes challenging, especially during the installation phase. Ultimately, without this communication and single-source teamwork, efficiency is reduced and installation costs soar; hence, this is where integrators earn their keep. The ideal supplier will have the following in-house capabilities:

• Project management
• Engineering
• Logistical
• Procurement
• Fabrication
• Assembly
• Testing
• Coating/painting
• Documentation management
• Certifications
• Regulatory approvals (DNV, Lloyd’s, USCG, ABS, MILS)
• Quality management

Very few organizations have the capacity and expertise for all these services and those that do are highly successful. It is very likely that suppliers who can manage these different processes have a longstanding record of diverse and large-scale projects. It simply makes sense from an owner’s perspective in terms of cost reduction and value proposition.

Jacob Shoesmith | Integrated Systems Development

Out with the Old, In with the New: Comparing Ballast Control Systems for the Hull

Comparing Conventional Hydraulic to Electro-Hydraulic Hull Systems

Conventional hydraulic systems are great for deep-water applications because they allow you to control a wide range of equipment. In a conventional hydraulic integrated ballast control system, the platform requires two or four central HPUs (hydraulic power unit) and the associated solenoid valve cabinets and accumulator racks. This field-proven design has been utilized on deep-water platform installations for decades. It is a tried-and-true hull automation solution that offers long service life, high reliability, and minimal required maintenance. However, from an installation perspective, central hydraulic systems might not be the most cost-effective option.

Today, a more cost-effective approach is an integrated electro-hydraulic hull solution. This solution incorporates an electrically-powered, PLC-controlled device that mounts directly to the hydraulic actuator and allows the operator to remotely open and close an automated valve assembly. This device is known as an LPU (local power unit). The LPU consists of a pump, reservoir, asynchronous capacitor motor, printed circuit board and logic manifold. This option eliminates the need for solenoid valve cabinets (for directing flow to the valve assembly), accumulator racks (for emergency shutdown operations), and miles of tubing. The obvious benefits include, but are not limited to, local control at the actuator and significant reduction in weight, oil volume, and space requirements. In other words, everything needed to operate the valve assembly is contained in one compact unit as opposed to two or four HPUs.

CapEx (Capital Expenditure) Comparison
In the offshore industry, CapEx costs are constantly being monitored so as to not exceed predetermined project budgets. The type of ballast control system utilized on a vessel can greatly influence this number. Factors that influence how a hull is automated include environmental considerations, installation costs, space availability, and weight. Consider the installation costs of a conventional hydraulic system. It is quite expensive because it requires the installation of thousands of feet of hydraulic tubing throughout the hull. However, conventional systems require more than just installing the tubing. Other requirements include flushing of the lines and penetration of multiple bulkheads. The installation costs associated with the conventional hydraulic ballast control system comprises the largest percentage of the CapEx value. Electro-hydraulic ballast control systems eliminate the aforementioned costs. As a result, this technology reduces capital expenditures and drives additional profitability.

High Torque of Hydraulics, Precise Control of Electronics
In an effort to optimize costs, today’s market is seeing a transition away from conventional hydraulic control systems and towards electro-hydraulic automation due to their environmentally-considerate design and high torque-to-weight ratios. Given the benefits of an electro-hydraulic integrated ballast control system, this design should be strongly considered as the most cost-effective solution for deep-water platform operators.

Jacob Shoesmith │ Marine/Offshore Integration Systems
Supreme Integrated Technology, Inc.

Efficiency through Integrated Design Methods

When we think of efficiency, pertaining to hydraulics, we commonly refer to the percentage of power loss in individual components within a system that dictates our required input power and cooling requirements. However, efficiency isn’t just about power loss through an individual component or system. It’s about using each component within the system to its greatest potential to drive out size and cost.

Take for example the historical approach to valve, actuator, and Hydraulic Power Unit (HPU) integration and supply. The path of least resistance is to allow the valve supplier to specify, procure, and integrate the actuators with the valves as a mated set. A separate supplier might then take the pressure requirements of the components provided to them by the end user or Engineering Procurement & Construction (EPC) firm, and design the HPU around that criteria.

Would the system perform with this degree of separation between the actuator and the HPU integrator? Sure it would, but does it maximize efficiency? Not at all. Valve torque is a fixed value at a given differential pressure (DP). And, the flow provided by the system dictates the cycle time.

From this basic information the entire system can be developed and optimized. The actuators are the system efficiency drivers. When separating the driver from the operator (in this case the HPU) efficiency is lost due to a lack of information in the design/supply chain which causes oversizing, sacrifices efficiency, and increases cost. The ability to capture and understand the impact of torque, pressure, and flow, as it relates to performance and efficiency, is a game changer in system design.

By treating the actuators, or motors in other examples, as an integrated part of the hydraulic system, true efficiency can be achieved. The benefits of a well-engineered and properly integrated system, include:

  • Actuator and motor size reductions by 25-50%
  • HPU footprint reductions by 20-40%
  • Reduction in energy consumption
  • Weight reductions from 20-35%
  • Installation time reductions
  • Overall system cost reductions by 20-35%

Additionally, component consolidation can be achieved through high pressure logic manifolds, simplified maintenance and tooling, decreased system pressure drops, and further reductions in installation and operator/maintainer training schedules and costs.

To sum it up, efficiency is not just about the percentage of power loss in individual components within a system. Its understanding how the components work together to perform the required tasks in the most efficient way possible, increasing performance and driving out costs.

Chris Sarro | Offshore / Subsea Systems Development Supreme Integrated Technology, Inc. 

 

Supreme Integrated Technology, Inc. Celebrates One Year Anniversary of Merger with Hydraquip Custom Systems, Inc.

Supreme Integrated Technology, Inc. Celebrates One Year Anniversary

of Merger with Hydraquip Custom Systems, Inc.

Houston, Texas – On September 1, 2017, Supreme Integrated Technology, Inc. (SIT) celebrated its one year anniversary of its merger with Hydraquip Custom Systems, Inc. (CSI). SIT is part of Employee Owned Holdings, Inc., a 100% employee-owned family of companies headquartered from Houston, Texas. As a result of the merger, SIT doubled its operations and now operate from Houston, Texas, in addition to its original headquarters in Harahan, Louisiana.

“This was a decision that just made sense,” stated Richard Neels, president of Employee Owned Holdings, Inc. “We had an opportunity where the synergies basically dictated we do this and it is now gratifying to see such success as a result.”

SIT expanded its reach into new and existing markets as a result of the merger, stretching further internationally than ever before. The result is that regardless of location, SIT can readily provide support and quick response times for its customer’s field service needs.

Over the past year, SIT engaged in several significant operations. SIT assisted in providing mission critical steering systems and hydraulic power units for marine vessels. Additionally, SIT engaged in completing jacking systems for two international liftboat projects, requiring and involving newly engineered and designed jacking system.

One additional highlight was an international project focused on crude and refined oil buoys involving over a dozen SIT employees. SIT was selected because it is able to significantly condense the amount of equipment needed for installation onto offshore buoys in order to rapidly transfer fluid from a ship to an onshore facility and vise-versa.

’Creating Structures in Motion’ is our motto,” stated Kevin Hayes, President of SIT. “But we will continue to look for ways, like this merger, to improve our offerings in design conception, engineering, and supply & support of turnkey systems along with product based applications to see what the next year will provide!”

Supreme Integrated Technology, Inc. is a subsidiary of Employee Owned Holdings, Inc., headquartered in Harahan, Louisiana, and is a 100% employee owned company. For other information about SIT and our family of employee owned companies, please visit www.supremeintegratedtechnology.com.

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