Q1. What is a flanged floating ball valve used for, and where is it used?
A1. A ball valve isolates or switches flow with a quarter turn of a bored ball. It is used wherever the valve is operated often or has to be operated quickly and visibly: on-off duty on water, oil, gas and chemicals, at the inlet and outlet of instruments and small pumps, on manifold and sampling points, on filling and emptying connections, and on gas lines where a tight seal matters. Compared with a gate valve the advantages are speed, a seal made by a seat that wipes itself as the ball turns, and no cavity in line with the flow. The limits come from the seat material: the polymer seats that give bubble-tight shut-off set a temperature ceiling, and the bore through the ball adds a small pressure loss that a full-bore design is used to avoid.
Q2. What design variants are available, and how do I tell them apart?
A2. Two design families matter. A floating ball is pressed against the downstream seat by the line pressure itself; it is simple, seals well in the smaller sizes and is the usual choice up to about DN200. A trunnion-mounted ball is supported top and bottom in bearings so the seats are loaded by a spring rather than by the line, which is what allows large sizes and high pressure to be handled with a low operating torque. Body construction is one-piece, two-piece or three-piece, the choice being driven by whether the valve must be serviced in line. Port can be full bore or reduced, and the seat is either soft or metal.
Q3. What body materials and seating arrangements can be specified?
A3. Carbon steel is standard for oil, gas and water; forged steel is used for small-bore and high-pressure classes where a cast body would be too thick; stainless (CF8 / CF8M) suits corrosive and clean service. Seat material follows the temperature and the medium: PTFE to about 180 °C, reinforced PTFE or PEEK higher, and metal-to-metal for abrasive media or high temperature. Two details worth stating in the enquiry are whether a fire-safe design is required (a metal back-up seat that holds after the soft insert is destroyed) and whether an anti-static device between ball, stem and body is needed, which is standard on gas service.
Q4. How does it compare with the alternative valve types on the same line?
A4. Choose by duty first and by price second. Isolation over long periods with low loss points at a gate or a ball valve; frequent on–off points at a ball valve; flow regulation points at a globe or a control valve; tight shut-off on gas at a soft-seated ball; and space-constrained large lines point at a butterfly. The cost comparison only becomes meaningful once the duty is fixed, because the cheapest valve of the wrong type is the expensive one.
Q5. What are the common failure modes, and how are they avoided?
A5. A valve that fails early usually fails for one of four reasons: it was selected on the normal condition and then met the extreme one, it was installed against the flow arrow, it was used for a duty it was never designed for such as throttling or as the sole isolation point, or it was commissioned without the pipework being cleaned. Only the first of those is a selection issue; the other three are found on site, which is why the installation checks matter as much as the specification.
Q6. How do I select the right one for my line?
A6. Match the valve to the frequency of operation, because that is the variable most often left out. A valve worked twice a year can be a simple handwheel type; the same valve worked twice a day needs a different seat, a different stem finish and probably a gearbox; worked from a control room it needs an actuator with position feedback. The number of cycles also decides whether the seat should be soft or hard, and whether spare seats or a spare complete unit is the right thing to hold in stores.
Q7. How do I order, and what information is needed for a quotation?
A7. Give us the service conditions rather than only a model number: size, pressure rating, medium, temperature and connection. Where a standard applies, name it and the revision. Custom work is normal in this range — end connections, operator type, trim material and surface treatment are all specified per order.
