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What is a backseat of Gate Valve

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What is a backseat?A backseat is a seating arrangement inside the bonnet. It provides a seal between the stem and bonnet and prevents system pressure from building against the valve packing when the valve is fully open. Back seats are often applied in gate and globe valves (source: wermac.org).
How to use the backseat?
The backseat should only be used to isolate the gland packing from the line medium for example when gland packing leakage is evident and until the valve can be de-pressurised and repaired.
How to not use the backseat?
Under no circumstances should the  backseat be used to allow gland packing replacement or repair while the valve and system are pressurized.Having clarified these 3 questions, the issue seems quite simple.
But it is not!One of the most common errors done on site is to believe that if the Gatevalve is back-seated (fully open position – and backseat sealing made), this will help to prevent wear of the packing rings.
Unfortunately using the back seat  in this way over a longer period of time, could  result in some serious issues:a)  Since the body, bonnet, stem, and disc heat up and expand at different rates, experience shows that valve can get jammed/blocked in back-seated positon.b) The gland packing will dry out since it’s not exposed to the steam, and could immediately blow upon closing of the valve.The simple but important rule for valve users, preventing misuse of the backseat!“Once the valve is brought into fully open position (back-seated), turn the hand wheel back one full turn”(this should be clearly stated in every Installation, Maintenance and Operating Manual of Valve Manufacturers),The other issue valve users experience is the problem with actuated valves. It does not matter if electric-, pneumatic- or hydraulic actuators are used. If the valve manufacturer does not correctly adjust the actuator in the open position, we will get back to the same problems (as described earlier). Field experience on high pressure/temperature drain valves (globe valve), pneumatically actuated and usually in fail safe open position, showing clearly the premature use of the gland packing rings.
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What is the difference between floating ball valve and Trunnion Ball Valves?

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What is the difference between floating ball valve and Trunnion Ball Valves? The ball of the floating ball valve is floating. Under the action of medium pressure, the ball can produce a certain displacement and press tightly on the sealing surface of the outlet end to ensure the sealing of the outlet end.

 

The floating ball valve has the advantages of small volume, light weight and simple structure. The ball of the floating ball valve has the function of free floating, which can better ensure the sealing; The ball can rotate freely in the valve seat sealing ring with the help of the valve stem. When opening, the ball hole is aligned with the pipe diameter to ensure that the working medium resistance of the pipe is very small. When the valve rod rotates for 1 / 4 turn, the ball hole is perpendicular to the channel of the valve. The ball is tightly pressed on the valve seat sealing ring at the outlet end by the preload and medium pressure applied to the two valve seat sealing rings, so as to ensure the complete sealing of the valve. This kind of ball valve is a one-sided forced seal.

The ball of the fixed ball valve can only rotate along the shaft under the action of the upper and lower valve shafts. The valve seat clings to the valve ball under the action of the back spring. The connection mode of valve ball and valve shaft includes welding, casting, forging and split type; There are many domestic key pin connections and many imported spline connections. Fixed ball valves are equipped with floating valve seats. After being subjected to medium pressure, the valve seats move to make the sealing ring tightly press on the ball to ensure sealing. Bearings are usually installed on the upper and lower shafts of the ball, with small operating torque. It is suitable for high-pressure and large-diameter valves. The common driving modes of fixed ball valves are worm gear drive, manual, electric and pneumatic. Most fixed ball valves are flanged, but there are also fixed ball valves in the form of welding.

 

 

 

 

 

 

 

 

 

 

 

 

 

The ball of the Trunnion Ball Valves can only rotate along the shaft under the action of the upper and lower valve shafts. The valve seat clings to the valve ball under the action of the back spring. The connection mode of valve ball and valve shaft includes welding, casting, forging and split type; There are many domestic key pin connections and many imported spline connections. Trunnion Ball Valves are equipped with floating valve seats. After being subjected to medium pressure, the valve seats move to make the sealing ring tightly press on the ball to ensure sealing. Bearings are usually installed on the upper and lower shafts of the ball, with small operating torque. It is suitable for high-pressure and large-diameter valves. The common driving modes of fixed ball valves are worm gear drive, manual, electric and pneumatic. Most Trunnion Ball Valves are flanged, but there are also fixed ball valves in the form of welding.

STV Valve Technology Group Co., Ltd is a professional leader China 150LB Cast Steel Ball Valve,24 Inch API 6D Cast Steel Trunnion Mounted Ball Valves,API 6D Cast Steel Trunnion Mounted Ball Valves,2-Piece Trunnion Mounted Ball Valve,Cast Steel Trunnion Mounted Ball Valve Manufacturer with high quality and competitive price.

 

Gate valve different globe valve

How To Maintain An Industrial Valves

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Industrial valves are everywhere in our lives, from the gates of major reservoirs to the taps used by every household. These are inseparable from the application of the valve, since the valve is so important to us, we should pay attention to the maintenance when we use the valve. Today, our STV Valve factory teaches you some maintenance methods of valves. Only after maintenance, can we use them for a longer time.

We only pay attention to the maintenance of the valve at ordinary times, so when we use the industrial valve, it will not go wrong, and the service life of the valve will be long. For that kind of special valve, its internal friction often occurs, so we should pay attention to the frequent application of lubricating oil to prevent friction problems. Have you ever had the experience that the faucet won’t turn when it’s not used for a long time. This is because the valve parts don’t move often and bite. So do not often use the valve also often to move the first round and add lubricating oil. For the kind of valve installed outdoors will receive the sun and rain, it is necessary to add a protective cover to extend its service life.

Industrial valve is a very important thing, as long as there is pollution on it, it should be cleaned quickly, not dragged. Always check all parts of the valve and replace them if they are damaged. Otherwise, it will be troublesome when the valve is required to work. Don’t hang things on the small valve, don’t put heavy things on the large valve, and don’t let children stand up to play. Unused valves should be stored in a dry place and should not be affected by moisture. Put them in order. To sum up, there are some maintenance methods for the valve, regular maintenance of the valve, to prevent the valve from getting worse and worse

Different Beteen A Lug And Wafer Butterfly Valve

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Butterfly valves have been around for a long time, and are used for a variety of applications. They made their first appearance during the 1930s, and have been utilized by several industries ever since. Often made out of cast iron, butterfly valve’s name is based from the functionality of its disc. There are a few different types of butterfly valves, however, they fall into two basic types – Lug and Wafer valves.

MORE ABOUT BUTTERFLY VALVES

Butterfly valves are classified as “quarter-turn” valves. When the metal disk that’s part of the valve’s design is rotated a quarter of a turn, it opens or closes. The disk, referred to as the “butterfly” is attached to a rod. When the butterfly valve is opened all the way, the disc rotates (a 1/4 turn), allowing for a nearly unrestricted passing of the fluid. You can also open the valve gradually to reduce flow. Turning the butterfly (disk), to close the valve, blocks the passage of the fluid. This is due to the disc always being perpendicular or parallel to the flow, resulting in a pressure decrease regardless of the position it is in.

LUG BUTTERFLY VALVE

The lug version of the butterfly valve’s design is similar to a 3-piece ball valve in that one end of the line can be taken off without having an effect on the opposing side. This can be executed by using threaded inserts, flanges, along with two sets of lugs (bolts) that don’t utilize nuts since each flange features its own bolts. It’s also important to note that you don’t need to shut down the entire system in order to clean, inspect, repair, or replace a lug butterfly valve (you would need to with a wafer butter valve).

WAFER BUTTERFLY VALVE

A wafer butterfly valve’s function is to retain a seal to protect against dual-directional pressure differential in the flow of fluid. In other words, the wafer version of butterfly valves was designed to hold a tight seal, safeguarding against bi-directional pressure differential in order to avoid any backflow in systems that have been manufactured for uni-directional flow. This is accomplished by using a tightly fitted seal, such as an O-ring, gasket, precision machined, along with a flat valve face on the downstream and upstream sections of the valve.

Both lug and wafer butterfly valves are used in a number of applications for industrial sectors that include food processing, pharmaceutical, chemical, oil, water as well as waste water management. The valves utilized in these industries are generally manufactured in compliance with the “Pharmaceutical Quality/Manufacturing Standard”, cGMP (current good manufacturing practice) guidelines. Butterfly valves for the most part have replaced ball valves in a lot of industries. This is especially the case for those dealing with petroleum because of they are less expensive and easy to install. It’s important to note that pipelines that contain butterfly valves can’t be ‘pigged’ for cleaning. “Pigging” is the process of making use of devices referred to as “pigs” to carry out a variety of maintenance operations.

What is The API 598 Leak testing of Valves

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API is American Petroleum Institute

The API standard 598: Valve Inspection and Testing, covers the testing and inspection requirements for gate, globe, check, ball, plug and butterfly valves. It has acceptable leakage rates for liquid as well as gas testing. All valves built to the various API standards are required to meet API-598 leakage criteria prior to shipment from the manufacturer or supplier.

API 598 states for shell and BACK SEAT tests, no visible leakage is permitted. If the fluid is a liquid, there shall be no visible evidence of drops or wetting of the external surfaces (no visible leakage through the body, body liner, if any, and body-to-bonnet joint and no structural damage).

If the test fluid is air or gas, no leakage shall be revealed by the established detection method. For both the low-pressure closure test and the high-pressure closure test, visual evidence of leakage through the disk, behind the seat rings, or past the shaft seals (of valves that have this feature) is not permitted (Plastic deformation of resilient seats and seals is not considered structural damage). The allowable rate for leakage of test fluid past the seats, for the duration of the tests, is listed in the following table:

Valve Size
NPS		 All Resilient
Seated
Valves		 All Metal Seated Valves
(except Check Valves)
Liquid Test
(drops
min.)		 Gas Test
(bubbles
min.)
< 2 0 0 (1) 0 (1)
2 – 6 0 12 24
8 – 12 0 20 40
> 12 0 28 56
Valve Size
NPS		 All Resilient
Seated
Valves		 Metal Seated
Check Valves
Liquid Test
(drops
min.)		 Gas Test
(bubbles
min.)
< 2 0 (2) (3)
2 – 6 0 (2) (3)
8 – 12 0 (2) (3)
> 12 0 (2) (3)

General notes:

  • 1 milliliter is considered equivalent to 16 drops.
  • For check valves larger than NPS 24, the allowable leakage rate
    shall be per agreement between purchaser and manufacturer.

Notes:

  1. There shall be no leakage for the minimum specified test duration. For liquid test, 0 drop means no visible leakage per minimum specified test duration. For gas test, 0 bubble means less then 1 bubble per minimum specified test duration.
  2. The maximum permissible leakage rate shall be 0.18 cubic inch (3 cubic centimeters) per minute per inch of nominal pipe size.
  3. The maximum permissible leakage rates shall be 1.5 standard cubic feet (0.042 cubic meter) of gas per hour per inch of nominal pipe size.

STV Delivery ANSI 150LB Gate Valve to Customer of South American

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STV Delivery ANSI 150LB Gate Valve to Customer of South American

150LB 1.- CLASS 150
2.- Valve design: API 600 / ASME B16.34
3.- Body: Carbon steel: ASTM A216-WCB
4.- Bonnete: ASTM A216-WCB
5.- Gate: A216-WCM carbon steel / 13% carbon
6.- Seat: Forged Steel ASTM A-105 / Estellita (Coated)
7.- Stem: ASTM A182
8.- Rear seat: A276-420
9.- Gasket:  A.276-420        STEEL VALVE TYPE BRIDGE TYPE  CLASS 150		 14“ 3 RF
150LB 18” 4 RF
150LB 24″ 4 RF

Introduction of the function of check valve and the analysis of the reason why check valve doesn’t work

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Function of check valve
The fluid resistance of swing check valve is generally less than that of lift check valve, which can be divided into three types: single disc swing, double disc swing and multi disc swing. Swing check valve is suitable for large caliber occasions. For the swing check valve larger than 80mm installed at the pump outlet, the horizontal installation method shall be adopted to reduce the valve disc seating and impact. For the pipeline with the diameter of the check valve at the pump outlet greater than or equal to 150 mm, the bypass shall be set before and after the check valve to prevent the damage to the sealing surface of the check valve caused by the high pressure rise in front of the valve.
The reason why the check valve does not work

  1. The check valve is installed reversely. It shows that the pipeline medium flows, and the check valve blocks the flow.
  2. Wrong selection or installation of check valve, such as vertical installation of check valve in vertical pipeline. For example, the flange connected lift check valve itself is installed vertically with the pipeline. The medium enters from the water inlet and pushes up the disc. The medium flows through the valve seat to another outlet of the check valve. The thrust to push the disc is less than the disc gravity, and the disc will fall naturally to the valve seat. If the valve is installed vertically, the gravity of the valve disc is all borne by the flange connected lift check valve, and the medium pushes the valve disc, only pushes the valve disc horizontally, and the valve disc cannot fall back to the valve seat naturally, causing the flange connected lift check valve to lose its function.
  3. The internal parts of the check valve are rusted. It is shown as the connection parts inside the swing check valve.
  4. The valve disc is not closed tightly due to the blockage of foreign matters
  5. Valve disc is broken or has sand hole.
  6. The check valves produced by  Stv Valve Technology Group  Co.,limited include swing check valve, lift check valve, ANSI check valve, DIN check valve, cast steel check valve, forged steel check valve and other materials.

150LB Stainless Steel Double Window Sight Glass

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PartsMaterialsMax.Pressure or Temperature
Body & Covers304 Stainless Steel-112°F to 797°F
316 Stainless Steel-320.8°F to 1202°F
316L Stainless Steel-320.8°F to 1472°F
WindowsTempered Soda Lime Glass235psig@212°F
Tempered Borosilicate Glass290psig@248°F
Tempered Quartz Glass362psig@392°F
Sealing GasketsNBR-4°F to 248°F
Viton-13°F to 400°F
PTFE(Teflon)-40°F to 500°F
Flange StandardANSI 150Lb/300Lb/DIN/JIS 5K/10K/Ghost/GB
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