| Size | Ball Long Pattern | Ball Short Pattern | Gate Solid Wedge & Double Disc | Plug Short Pattern | Plug Regular Pattern | Globe Lift & Swing Check |
|---|---|---|---|---|---|---|
| 1/2" | 4.25 | 4.25 | 4.25 | - | - | 4.25 |
| 3/4" | 4.60 | 4.60 | 4.60 | - | - | 4.60 |
| 1" | 5.00 | 5.00 | 5.00 | 5.50 | - | 5.00 |
| 1-1/4" | 5.50 | 5.50 | 5.50 | - | - | 5.50 |
| 1-1/2" | 6.50 | 6.50 | 6.50 | 6.50 | - | 6.50 |
| 2" | 7.00 | 7.00 | 7.00 | 7.00 | - | 8.00 |
| 2-1/2" | 7.50 | 7.50 | 7.50 | 7.50 | - | 8.50 |
| 3" | 8.00 | 8.00 | 8.00 | 8.00 | - | 9.50 |
| 4" | 9.00 | 9.00 | 9.00 | 9.00 | 12.00 | 11.50 |
| 6" | 15.50 | 10.50 | 10.50 | 10.50 | 15.50 | 16.00 |
BUT WHAT DOES COMPLIANCE TO B16.34 EXACTLY MEAN?
- Body and shell materials comply with ASME and ASTM material standards for chemistry and strength.
- Body and shell materials are heat-treated to insure proper grain structure, corrosion resistance and hardness.
- Wall thicknesses of body and other pressure-containing components meet ASME B16.34 specified minimum values for each pressure class.
- NPT and Socket Weld end connections comply with ASME B1.20.1 or ASME B16.11.
- Stems will internally loaded and blowout proof.
- All bolting will be ASTM grade with maximum applied stress controlled by B16.34.
- Each valve is tested for seat leakage in both directions for a specific test time duration.
- Each valve is permanently tagged with materials of construction, operating limits and name of manufacturer.
When purchasing valves according to ASME B16.34 it is advised to check with the supplier if they are really in full compliance with this standard.
The choice of end connections for connecting a valve to its associated pipework is dependent upon the pressure and temperature of the working fluid and the frequency of dismantling the pipeline or removing the valve from the line.
SCREWED VALVE END CONNECTIONS
Male threads of various forms may be used for special purposes, but as a rule screwed end valves have female pipe threads, wither tapered for assembly to taper threaded pipe, or parallel for assembly to taper or parallel threaded pipe. In taper-to-taper and in taper-to-parallel connections, the pressure-tight joint is made on the threads. In parallel-to-parallel connections, the pres- sure tight joint is made by compressing a grommet or gasket against the end face of a valve. Screwed ends, usually confined to pipe sizes of 150mm and smaller, are widely used for bronze valves and to a lesser extent in iron and steel valves.
FLANGED VALVE END CONNECTIONS
Flanged-end valves are easy to install or remove from a pipeline, being bolted to the mating pipe flanges. To ensure a tight seal, a gasket is usually fitted between the machined facing of the flanges. The type of gasket, which can be non-metallic, metallic or a combination of both, depends upon service conditions and upon the type of flange facing employed. Bronze and iron valves are normally supplied with plain (flat) facings, and steel valves with plain (flat), raised or male facings, although female, tongue and groove, or ring-joint types are available. Flanged end valves are made in sizes from 15mm upwards.
SOCKET WELD VALVE END CONNECTIONS
In this type, the ends of a valve are socketed to receive plain-end pipe. A circumferential weld is made on the outside of the pipe so that ‘icicles’ and weld spatter are unable to enter the pipeline. Socket-weld ends are used only on steel valves, and as a rule they are limited to sizes of 50mm and smaller for higher pressure/temperature applications in pipelines not requiring frequent dismantling.
BUTT WELD VALVE END CONNECTIONS
In this case, the ends of the valve are beveled to match wall thickness and machined bevel at the end of a mating pipe. A circum- ferential weld is made at the abutted mating bevels. ‘Backing rings’ which are basically sleeves fitting inside the pipe, are sometimes used to align the pipe and valve bores also to prevent ‘icicles’ and weld spatter from entering the pipeline. Butt- weld ends are used only on steel valves, normally in sizes 50mm and upwards, for the higher pressure/temperature applications in pipelines which do not require frequent dismantling.
COMPRESSION VALVE END CONNECTIONS
This type of valve end has a socket to receive the pipe and is fitted with a screwed union nut. The joint is made by the compres- sion of a ring or sleeve on to the outside of a plain-end pipe, or by compressing a preformed portion of the pipe end. As a rule compression ends are used with copper tubing and steel tubing up to 65mm diameter and are used for low pressures or where pipes may require frequent dismantling.
Flanges are usually installed on valves larger than 2”. For sizes smaller than 2”, threaded-style valve are typically used, depend- ing on the application and safety considerations: for example at steam lines, even for sizes below 2”, welded type valves are used instead of threaded type ones. The main advantage of using a flanged valve is the valve can be easily removed from the line. However, it is to be noted that flanges are subject to thermal distortion and shock. Therefore a weld connection would usually recommended for applications where significant temperature variations occur. Flanges are generally built to ANSI standard B16.5 (or DIN or other international standards). Rating of flanged is made according to the type of service, material requirement, maximum service temperature and pressure. The following three (3) major valves flanged ends connections are mostly in use nowadays:
- Flat face (FF)
- Raised face (RF)
- Ring type joint
FLAT FACE FLANGE CONNECTION
Flat face flanges allow full contact between the two mating flanges and the flange gasket (a gasket is installed between the flanges in order to seal the connection). They are mostly used with low pressure applications, like for example in cast iron flanges. Due to the fact that both flanges are in full contact with each other, this design keeps help flange stresses to a minimum. However, a disadvantage of this type of flanges is the flange faces will have to completely flat in order to properly seal across the entire flange.
RAISED FACE FLANGE CONNECTION
The raised face is the most common of all flanged faces. The Raised face is named like the because the gasket surfaces are raised above the bolting circle face (the raised face is only a slight step). Raised face flanges are therefore not full contact flanges. As such, some flange stress may be created when the bolting is tightened. The raised face is finished with a series of concentric circular grooves for keeping the gasket in place and providing a better seal. Raised face flanges are specified for low, medium and high pressure-temperature applications.
RING TYPE JOINT FLANGE CONNECTION
Ring type joint flanges are actually a modification of the raised face design. RTJ flanges have grooves cut into their faces with steel ring gaskets. RTJ flanges are usually specified for high pressure and high temperature applications.
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