In a time of ever-increasing demand for industrial growth and end products, sectors such as refining, water and wastewater, hydropower, chemical and mining are seeing a move toward bigger valves. But with greater size, many factors and design considerations come into play, as it’s not a simple proposition of enlarging the valve components. Very few companies in the world are capable of manufacturing such large valves.
What are the most significant challenges in dealing with exceptionally large valves?
There are simply fewer companies that have the design expertise and manufacturing capability available to handle big valves. There are also fewer foundries that can pour the large castings. Engineering capability and complex tooling may need to be created. Valve manufacturers that have the expertise, equipment and facilities to produce large valves are rare. The manufacturing process may be less vertically integrated — handling, testing and transporting larger valves is more challenging.
Other noteworthy large-valve challenges include:
Material handling for fabrication and testing (factory crane capacity and lift height limitations) is a challenge. Another issue is machine tool limitations (the mill and lathe size required).
Compliance with industry standards that apply to smaller valves can often be cost-prohibitive to meet on a larger valve.
Stroke speed (speed that the gate or flow element moves) for large electrically actuated valves may need to be faster than that for a smaller valve so as not to exceed standard 15- or 30-minute electric actuator motor run times.
Standard semi-trailer over-road maximum capacity is 80,000 pounds. At the site, the contractor may also have handling limitations or the access to the installed location may be restricted, requiring the valve be shipped in pieces and assembled onsite.
Are your largest valves all “one off” or custom-made?
The first time a large valve is built, it is a custom build, but as requirements for larger valves increase, so does the likelihood that the valve build will be repeated until it is no longer a special. All large Hilton valves are custom fabricated or “one off.” The advantage of this is that the valve can be designed to meet specific pressure regimes. Most cast valves have a minimum pressure rating of 150 psi; if only 50 psi is required, a 50 psi fabricated valve can be supplied. This greatly reduces the weight and cost of the valve.
Why is there a trend toward producing bigger valves?
The frequency and severity of drought in the West and severe weather events, like slow-moving hurricanes in the gulf and on the East Coast, have motivated municipalities to creatively figure out how to collect, protect and conserve available raw and semi-finished freshwater resources. The large population migration to non-drought areas and the numerous water conservation projects in drought-ridden regions are fueling some very large projects, such as protectively “banking” water that has already been treated in new facilities. There are also big projects underway to prevent raw water reservoirs from overflowing to the south. To do this, new or larger pumping stations are being built to pump (transfer) water over to neighboring northern reservoirs to minimize losing what has already been naturally collected. Moving larger amounts of water requires bigger valves.
What are the most significant challenges in dealing with exceptionally large valves?
One of the biggest challenges is costing and pricing. Due to the seldom-sourced large-diameter product, the ability to accurately estimate the cost to produce these sizes is a big risk for manufacturers — the work is often too large to machine in-house, so the outsourced production becomes an unknown cost variable, which is a gray area in getting a fixed or capped cost. The same goes for the raw materials. These projects are sometimes years out, so the cost per pound of carbon steel and stainless alloys can swing in the wrong direction over the course of the project. Also, any ancillary (one-time) equipment costs need to be taken into consideration, such as testing equipment (test heads with bolts and nuts). The costs are high and the lead time alone to obtain a pair of large-diameter test heads can be up to 18 months. Another challenge is that when you are dealing with large castings you have more room for casting issues, like porosity. Also handling and testing becomes more complicated as valves get larger.
Are your largest valves all “one off” or custom-made?
Yes. Anything that is not covered by a nationally recognized standard (or designed to the intent of a standard) is considered a custom product. For both butterfly and plug valves, we have large standard castings, but we have also fabricated large butterfly valves.
Post time: May-09-2022