Definition of Valve:Valves are mechanical devices specifically designed to direct, start, stop, or regulate the flow, pressure of a process fluid. Valves can be designed to handle either liquid or gas applications.By nature of their design, function, & application, valves come under wide variety of styles, sizes & pressure classes. Valves can be manufactured from different types of materials, like steel, alloys of steels, nickel alloys, iron or number of special alloys
GlobeValves: – Globe valve is a linear-motion valve characterized by a body with a longer face to face that accommodates flow passages sufficiently longs enough to ensure smooth flow through the valve without any sharp turns. It is used for both on-off and throttling applications. The most common closure element is the single-seat design, which operates in linear fashion & is found in the middle of the body. Majority of the globe valve designs permit easier servicing of the internal parts by disassembling the bonnet flange & flange bolting & removing the bonnet, & plug as one assembly. Most globe valves use the T-style body, allowing the valve to be installed in a straight pipe. Flow enters through the inlet port to the center of the valve where the trim is located. At this point the flow makes a 90-degree turn to flow through the seat, followed by another 90-degree turn to exit the valve. In most of the globe valves flow direction is under the plug.
Bellow Sealed Globe Valves: -The large volume & wide variety of hazardous & toxic materials in use, coupled with increasingly stringent regulatory requirements, makes positive containment & control mandatory. One of the serious valve problems is gland leakage resulting in waste & increased plant downtime. Apart from the high cost of energy losses, gland leakage can also cause serious environmental ecological & often health problems to the plant workers & personnel’s. Leakage of sensitive materials can constitute a fire hazard. There could be the risk of explosion, or corrosive materials could damage other equipments & also be harmful to the employees. Air entering the pipeline could produce inflammable explosive or poisonous mixtures.
“Zero-stem” leakage eliminates product losses, hazards to humans, the environment & costly downtime ordinarily required for packing maintenance. SG brand globe valves with bellow seal construction eliminates the gland leakage absolutely & valve spindle is sealed with Stainless steel / Hastelloy-C 276 / Inconel-625 Bellow either in single ply or multiply construction. Bellow with bottom bellow collar is welded to valve spindle/plug at lower side & the top bellow collar at the upper side. This top bellow collar is held in between the body & bonnet joints or directly welded to the bonnet & glands are sealed to have Absolute Zero-Leakage. These metallic bellows can withstand high pressure & temperature also. Body bonnet joints are with metallic gaskets to prevent the leakage.
M/s SG valves. produces wide range of Globe Valves. Classification of the Globe Valves will be done on the basis of,
Types of valve:
- ANSI / ASME CLASS 2500,Sizes from ½” NB to 4”NB
- ANSI / ASME CLASS 1500,Sizes from ½” NB to 6”NB
- ANSI / ASME CLASS 900,Sizes from ½” NB to 14”NB
- ANSI / ASME CLASS 800,Sizes from ½” NB to 2”NB
- ANSI / ASME CLASS 600,Sizes from ½” NB to 14”NB
- ANSI / ASME CLASS 300,Sizes from ½” NB to 24”NB
- ANSI / ASME CLASS 150,Sizes from ½” NB to 24”NB
- Size & Class:
- Bellow Seal Globe valves
- Globe Valves
- Type of construction:
- Casting valves
- Forging valves
- Body –Bonnet connection:
- Bolted connection
- Welded connection
- Screwed connection
- End connections:
- Flanged end
- Butt weld end
- Socket weld end
- Screwed end
- Type of body:
- Straight or “T” type
- “Y” type
- Angle type
Bellow Sealed Globe Valve:Bellow sealed Globe valve is a linear motion valve characterized by a Body with longer face to face that accommodates flow passages, which is sufficiently long enough to ensure smooth flow through the valve without any sharp turns.
- 1.Body: The design of the Body shall be such that it has to provide ample resistance to distortion under the maximum cold working pressure & under specified pressure at the maximum temperature. Body is the major pressure-retaining component of valve that houses the closure device, as well as inlet and outlet parts.
- Body End connection: The part of a valve that matches and joins with the matching piping.
- Bonnet: A pressure retaining part that house the packing box and guides, as well as seals the top works of a valve body. It has got a flange used to retain the Bonnet to the body.
- Plug or Disk: The closure component in a Globe valve used to open or close the flow. In linear globe valve a round orifice in which the plug fits to achieve shutoff. In this case plug is of pressure relief type Design so that we can operate the valve smoothly.
- Integral seat: A seating surface machined into the body itself. Integral seats are usually used with oversized closure elements to provide greater flow than is normally provided in a given valve size.
- Bellow: Bellow is a metallic component. It is flexible device that is welded to a stem or a shaft to provide a solid barrier between the process fluid and the atmosphere. The bellows seal arrangement shall prevent leakage past the stem to atmosphere. The bellow shall have minimum of two plies.
- Bellow Collar: Bellow Collar is used as a supporting ring to weld the bellow to the stem. The bellow collar material is same as that of bellow material.
- Stem: The component attached to the closure device and the actuation device. It is a rod portion of the closure element.
- Back Seat: In linear valves, a special design that permits a portion of the stem to seat against the bottom of the bonnet to help prevent process flow from migrating into the packing box.
- Stud/Fasteners: A threaded rod in which both ends are secured with a nut. Used to connect various joints of valves such as Body, Bonnet, Cylinder, Side Flanges etc.
- Gland Bush: A part found at the top of the packing box that protects the packing Box from atmospheric elements and transfers force from the gland flange bolting to the packing.
- Gland Flange: Valve part used to retain & compress, packing by applying Bolting Load.
- Packing: A soft material used to prevent the leakage of process fluid from around a valve stem or shaft and the bore of the Bonnet.
- Yoke Sleeve: In Globe Valves, the part that provides a sliding seal surface for a pressure balanced plug.
- Gland stud / Nut: Gland stud / Nut is used to connect the Gland Flange to the Bonnet. By tightening the Gland stud / nut proper sealing of the packing can be done through the Gland Bush.
- Hand Wheel: A manual operator with a wheel that turns clockwise or counter clockwise to manually operate the valve. Normally clockwise to open the valve
- Hand wheel Nut/Indicator: Hand wheel nut/Indicator is fitted to the yoke sleeve. Outer portion of the threading that prevents the movement of Hand wheel coming out from the yoke sleeve. It also show the valve opening indication.
- Yoke Nut: Yoke nut fitted the top of bonnet, which resists the upward movement of the yoke sleeve due to upward force creating due linear motion of the stem.
- Top Bellow Collar (TBC): TBC is the supporting ring for the Bellow to weld at top side. It is placed in between the body and the bonnet Gasket Groove provided. The material is same as that of bellow material. In some cases the TBC is directly welded to the Bonnet.
- Gasket: A Gasket produced with simple inside & outside diameters with even, flat A gasket consisting of alternate layer of metallic & non-metallic materials would together.
- Hand Wheel Key: Hand Wheel Key is used to transfer the rotary motion of the hand wheel to yoke sleeve, which in turn moves the stem linearly.
- Guide Plate: Guide Plate is used to prevent the rotation of the stem in case of Bellow Seal Globe Valve because it may damage the bellow.
- Grease Nipple: Grease Nipple is fitted at the Top Flange of the Bonnet where the Yoke Sleeve seats. With the help of Grease Nipple we can provide proper lubrication to the rotating Yoke Sleeve, which in turn reduces the friction between the mating parts.
- Grub Screw: Grub Screw is fitted at the Top Flange of the Bonnet to prevent rotation of the yoke nut.
- Leak detector: This is fitted in between gland packing and bellow area .Thiswill help us to detect the leakage of process fluid..
Bellow sealed Globe Valve Operation: Most common globe valves use a T-style body. Flow enters inlet port to the center of the valve where the trim is located. At this point, the flow makes a 90o turn to exit the valve. Where as in case of Pressure relief type plug design flow is over the plug. The flow direction of globe valves is defined by the manufacturer or the application. Although in most manual application, flow direction is under the plug. With under the plug flow, the valve is relatively easy to close as long as the fluid pressure and flow rate are low to moderate. In addition, under the plug flow provides easy opening by the flow pushing against the bottom of the plug.
Rotary motion of the Hand wheel causes the linear motion of the stem along with plug with the help of ACME threading between the Yoke Sleeve and Stem. In ideal situations, the flow should freely circulate around the plug and seat, allowing flow to enter the seat from every possible direction.
When globe valve closes, the axial force of the manual hand wheel is transferred to the plug. Plug-seating surface is forced against the seat ring, not allowing any flow to pass through the closure element. In full open position, the entire seating area is open to the flow.