Manual valves Flashcards
Welke 4 functies van valves zijn er, en hoe heten deze soorten die de respectievelijke functie vervullen?
Starting or stopping flow – Block Valves Controlling the amount of flow – Control Valves Preventing backflow (flow reversal) – Check Valves Relieving excess pressure – Safety Valves
Vertel wat meer over block valves: Hoe openen, hoe in het gebruik, tight shutoff, most common type?
On-off valve, fully opened or fully closed, 1) separate fluids 2) combine fluids 3) equip isolation for maintenance tight shut-off at closure Most common is block valve
Vertel wat meer over control valves: 1) primary purpose 2) position 3) most common type 4) welke valves toepasbaar
1) restrict flow, thus enabling the flow of fluid to be regulated (or throttled) 2) partially open 3) globe valve 4) most valves can be used to control flow, not all valves are designed to consistently operate as a controller for an extended period of time
Vertel eens wat meer over check valves: 1) prupose 3) additional purposes 2) position? 4) how close?
1) allow for normal flow in one direction 3) helps isolate piping system to min potential safety hazards, preventing fluid contamination, prevent back flow that can be damaging to rotating equipment 2) open position by the fluid 4) gravity, attempted reversal of flow, springs, drop in system pressure
Vertel eens wat meer over PRV’s 1) purpose
automatically release excessive pressures
Noem de verschillende onderdelen van een klep
Wat is de functie van de body?
Secundaire functie?
Hoe kan de body zijn verbonden?
- Body, sometimes called shell, is the primary pressure boundary of valve
- Body serves as the principal part of valve assembly because the body is the piece holding everything together
- Connected to inlet and outlet piping:
–Threaded
–bolted or
–welded
Vertel wat meer over de bonnet
- Bonnet is part of the valve’s outer casing
- Mounted on top of valve body
- Houses:
–Stem
–Disk
–Packing
- Bonnet is the second principal pressure boundary of a valve
- Cast or forged of the same material as the body
- Bonnet is connected to the body by a threaded, bolted, or welded joint
- In all cases, the attachment of the bonnet to the body is considered a pressure boundary
- The weld joint or bolts that connect the bonnet to the body are pressure-retaining parts
- Valve bonnets, although a necessity for most valves, represent a cause for concern. Bonnets can:
–Complicate the manufacture of valves
–Increase valve size/weight
–Be a source for potential leakage
Vertel wat meer over de trim: waar bestaat die uit. Performance bepaald door? Welke twee basic motions zijn mogelijk?
- Internal elements of valve collectively referred to as valve trim
- Trim typically includes:
–Disk
–Seat
–Stem and
–Sleeves to guide stem
•Valve’s performance is determined by:
–Disk and seat interface and
–Relation of disk position to seat
- Because of the trim, basic motions and flow control are possible
- Basic motions are linear and rotational.
–In linear motion trim designs, the disk lift perpendicular to the seat so that an annular orifice appears
–In rotational motion trim designs, the disk slides closely past the seat to produce a change in flow opening
Vertel wat meer over de disk: wat gebeurt wanneer de disk is gesloten? Gegoten of gesmeed? Welk materiaal bij goede slijtage weerstand? Wat is de voorwaarde voor een goede sealing functie?
- With the disk closed, full system pressure is applied across the disk if the outlet side is depressurized
- Disk is a pressure-retaining part
- Disks are typically forged
- In some designs, disks are hard-surfaced to provide good wear characteristics
- A fine surface finish of disk’s seating area is necessary for a good seal when the valve is closed
Vertel wat meer over de seats: hoe verzozrgt seating surface de afdichting?
•Seat or seal rings provide seating surface for disk
–In some designs, body is machined to serve as the seating surface, and seal rings are not used
–In other designs, forged seal rings are threaded or welded to the body to provide the seating surface
•Surface is often hard-faced by welding, and machined smooth for a tight fit of the disk, which improves the wear resistance of the steel rings
Vertel wat meer over de stem: wat is de functie? hoe is gemaakt, forged or cast? is het een pressure boundary part?
- Stem, which connects actuator (hand wheel) to disk, is responsible for positioning the disk
- Stems typically forged and connected to disk by slotted, threaded, or welded joints
- For valve designs requiring stem packing or sealing to prevent leakage, a fine surface finish of stem in area of seal is necessary
- Typically, stem is not considered a pressure boundary part
Welke twee types stem zijn er?
•Two types of valve stems
–Rising stems and
–Non-rising stems
Vertel wat meer over Yoke and Stuffing Box
•Yoke
–Attached to top of bonnet
–Supports hand wheel through which stem is threaded
•Stuffing box
–Is a cavity inside valve bonnet that holds packing material
–Packing
ØProvides seal against leakage around the valve stem
ØCompressed to fit inside stuffing box
ØExpands during operation to prevent fluid from leaking out
•Gland follower
–Fits around stem, on top of packing gland, and exerts pressure on the packing gland
–Compresses the packing
•Packing gland
–Ring-shaped piece that fits around stem and compresses packing into the stuffing box
•Pressure is usually applied
–By tightening gland nuts, which connect follower to bonnet, or
–In some small valves, gland follower is threaded to the stuffing box and is “screwed down” to compress packing
Vertel wat meer over gate valves?
Voornamlijk gebruikt als? Hoe krijgt deze zijn naam? Kun je throttlen?
- Gate valves are the most common type of block valves and are often referred to as ON/OFF valves
- Primarily used to isolate systems and equipment
- Gate valves are named for the operation of the disk, which is raised and lowered like a gate
- Gate valve is a linear motion valve used to start or stop fluid flow
- Gate valve is not designed to regulate or throttle flow
