Valsource International, LLC (VSI) provides valve repair and maintenance for pipeline valves through our "Field Service Group". VSI can perform the covered tasks that involve valve repair and maintenance in all pipeline locations. Our crew is vetted through NCCER and Veriforce, Valsource is nationally compliant with both DOT and PHMSA. Valsource interfaces with ISNetworld, Pics Auditing, DISA & PES Safety verified on both EMR and OSHA. These institutions ensure the customer that a valve technician has been trained and is knowledgeable. Pipeline valves consist of the following types of valves:
- Ball Valves
- Butterfly Valves
- Check Valves
- Gate Valves
- Globe Valves
- Plug Valves
A ball valve is a valve with a spherical disc (or ball) that works to control the flow through it. The ball (sphere) has a hole (known as a port) that when "in line" or "open" allows flow to occur. When the valve is closed the hole is perpendicular to the ends of the valve thus stopping flow. Ball valves are typically operated with a lever, gear, or an actuator. They are part of the quarter turn family meaning that the opening mechanism needs to be turned a quarter (or 90 degrees) to open or close the valve. They are en excellent choice for shutoff applications; however typically do not offer fine control necessary for throttling applications.
Butterfly valves are used for isolating or regulating flow. They are a quarter turn valve similar to a ball valve except the closing mechanism is a disk instead of a ball. Butterfly valves are typically lower in cost to other valve types as they are lighter in weight meaning less support is required to have them in line. The disc of the valve is operated by either a lever, gear or actuator. When the valve is closed the disc blocks the flow- when open the disk turns to allow flow to pass through; however the disk will always be present within the flow resulting in a pressure drop regardless of valve position. Butterfly valves can also be open incrementally to throttle flow. Butterfly valves come typically in wafer or lug style; however it is not uncommon to see a flanged butterfly valve in high performance applications.
A globe valve is a linear valve used to start, stop and regulate flow. The globe valve disk can be completely or partially removed from the flow or it can completely close the flow. Globe valves are used for applications requiring throttling and frequent operation. For example, globe valves or valves with a similar mechanism, may be used as sampling valves, which are normally shut except when liquid samples are being taken. Since the baffle restricts flow, they're not recommended where full, unobstructed flow is required.
Plug valves are valves with cylindrical or conically-tapered "plugs" which can be rotated inside the valve body to control flow through the valve. The plugs in plug valves have one or more hollow passageways going sideways through the plug, so that fluid can flow through the plug when the valve is open. Plug valves are simple and often economical. When the plug is conically-tapered, the stem/handle is typically attached to the larger diameter end of the plug. Plug valves usually do not have bonnets but often have the end of the plug with the handle exposed or mostly exposed to the outside. In cases like that, there is usually not much of a stem. The stem and handle often come in one piece, often a simple, approximately L-shaped handle attached to the end of the plug. The other end of the plug is often exposed to the outside of the valve too, but with a mechanism which retains the plug in the body.
Control valves are valves used to control conditions such as flow, pressure, temperature and liquid level by fully or partially opening or closing in response to signals received from controllers that compare a "setpoint" to a "process variable" whose value is provided by sensors that monitor changes in such conditions. The opening or closing of control valves is done by means of electrical, pneumatic or hydraulic systems. Positioners are used to control the opening or closing of the actuator based on Electric, or Pneumatic Signals. These control signals, traditionally based on 3-15psi (0.2-1.0bar), more common now are 4-20mA signals for industry, 0-10V for HVAC systems, & the introduction of "Smart" systems, HART, Fieldbus Foundation and Profibus being the more common protocols.
Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave. There are various types of check valves used in a wide variety of applications. Check valves are often part of common household items. Although they are available in a wide range of sizes and costs, check valves generally are very small, simple, and/or inexpensive. Check valves work automatically and most are not controlled by a person or any external control; accordingly, most do not have any valve handle or stem.
A gate valve is a valve that operates using a round/rectangular gate (wedge) out of the path of the fluid. The distinct feature of a gate valve is the sealing surfaces between the gate and seats are planar, so gate valves are often used when a straight-line flow of fluid and minimum restriction is desired. The gate faces can form a wedge shape or they can be parallel. Typical gate valves should never be used for regulating flow, unless they are specifically designed for that purpose. On opening the gate valve, the flow path is enlarged in a highly nonlinear manner with respect to percent of opening. This means that the flow rate does not change evenly with stem travel. Also, a partially open gate disk tends to vibrate from the fluid flow. Most of the flow change occurs near shutoff with a relatively high fluid velocity causing disk and seat wear and eventual leakage if used to regulate flow. Typical gate valves are designed to be fully opened or closed. When fully open, the typical gate valve has no obstruction in the flow path, resulting in very low friction loss.