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TECHNICAL INFORMATION
The technical information presented here is intended to assist designers in the proper selection of Parker Autoclave Engineers’ valves, fittings and tubing for fluid handling systems. This technical data does not represent product specifications but rather guidelines for direction in the proper application of the referenced equipment. These guidelines are general in nature because of the many process variables.
Materials:
Widely varying conditions frequently require that valves, fittings and tubing be constructed of materials other than conventional stainless steel. Since many variables affect the corrosion resistance of metallic materials, it is Parker Autoclave Engineers’ policy not to recommend materials based on corrosion resistance for specific fluid applications. We can, however, suggest materials based on mechanical strength and also indicate materials generally used in a specific application. Other materials not listed in this section are also available.
Pressure:
Included in this section are the standard pressure ratings for several common materials for valves and fittings as well as tubing. Parker Autoclave Engineers stocks a select quantity of special material tubing for immediate delivery.
Temperature:
Also contained in this section are pressure reduction factors at various temperatures for several materials. To obtain the maximum pressure rating at an elevated temperature, multiply the maximum pressure rating of the item at room temperature by the elevated temperature factor (% of RT). High and low temperatures or high heat up and/or cool down rates can affect the capability of a metal-to-metal seal. When selecting a valve series, consideration should not only be given to static pressure rating, but also static and dynamic temperature conditions. Generally, the smaller the seal diameter of a metal-to-metal seal, the more reliable the seal will be.
Gas or Liquid Service:
Light gases such as hydrogen and helium are more difficult to seal than liquids. When selecting a valve series, consideration should be given to the fluid application and not just pressure and temperature requirements. The higher the rating of the valve or fitting, the less the likelihood of weepage problems with light gases. Tubing selections should also consider the service requirements, since thicker wall, smaller outside diameter tube sizes will produce a more reliable connection seal. Handling of fittings and tubing during installation will make a difference in sealability of light gases as well as liquids. Do not handle the tube or fitting in such a way as to damage the sealing surfaces. If it is process tolerable, a small amount of lubrication (or even process fluid) on the seal area during
installation will help the sealing process. Refer to the Tools, Installation, Operation and Maintenance section for further information.
Valve Stem Packing Materials:
The considerations listed thus far should be applied when selecting a suitable valve stem packing material (PTFE, PTFE glass or Graphite yarn). Where possible, PTFE packing is the most reliable, low maintenance, packing choice; PTFE/glass is the second. While graphite yarn packing is a reliable packing
material for the majority of extremely high temperature applications, some gases may permeate more readily through graphite yarn packing than through the PTFE packing in a valve with an extended stuffing box. The packing material must be kept below the maximum permitted temperature listed on page 5.
Valve Stem Seating:
Abrasive flow or high cycle service will require more frequent maintenance. Special materials and the proper valve series selection may extend service life. For example, if flow is not critical, a 30VM valve with an N-Dura stem will require less maintenance than an SW series valve used in a low pressure, high cycle, abrasive flow application. Although all application parameters cannot be considered in this section, the user can generally expect several thousand cycles in a liquid application and several hundred cycles for gas service. The packing gland may require adjustment, however, to achieve these results.
Pressure Cycling:
In medium and high pressure applications, static as well as dynamic (cyclic) pressure must be considered when selecting an appropriate valve series. If fatigue life is a concern, Parker Autoclave Engineers can supply tubing which has been autofrettaged for improved fatigue resistance. For internally pressurized
tubing, autofrettaging is a method by which the inner wall of the tube is precompressed to reduce the tube operating bore stresses. By applying sufficient internal pressure, greater than the maximum working pressure of the tube, the inner wall is plastically deformed by a controlled amount. The remaining outer portion of the wall acts elastically, and when the pressure is released, a positive compressive load at the bore will exist. As mentioned previously, the result is reduced bore stress and increased fatigue life. In addition to the autofrettaging
method to increase cycle life, Parker Autoclave Engineers offers HP-HC (high-pressure — high cycle) tubing, rated to 100,000 psi (6895 bar). This tubing can be substituted for our standard 60,000 psi (4137 bar) tubing providing longer life at 60,000 psi (4137 bar) operation.
Vacuum Service:
The high, medium and low pressure series of Parker Autoclave Engineers’ standard valves, fittings and tubing can be used in light vacuum services to 10-2 torr. For high vacuums to 10-5 or 10-6 torr, Parker Autoclave Engineers’ high pressure series is recommended. Extreme care and proper seal lubrication is required (as mentioned in the Gas or Liquid Service paragraph) to achieve these degrees of vacuum. The pump type and size will determine the final vacuum pressure.
technical information catalogCONNECTION DETAILS
(Medium and High Pressure Coned-and-Threaded connections)
High-pressure designs require a superior joining technique for valves, fitting and tubing. Conventional joining methods fall short of the reliability needed for pressures above 10,000 – 15,000 psi (690-1034 bar) and tube sizes above 1/4” outside diameter. Dissimilar angles between the body and the tube cone provide line contact sealing along the perimeter of a contact circle. The sealing contact area is therefore, maintained at its practical minimum for the given tube size and a reliable seal is produced due to high sealing stresses that occur at low sealing loads. When process tolerable, a small amount of lubricant (or even process fluid) on the seal area will help improve the reliability of the metal to metal seals, especially when light molecule gases are to be sealed. The metal to metal
seal also eliminates the need for elastomers in the connections. Positive backup support occurs with the collar threaded (left-handed) directly onto the tubing to form a positive integral retaining surface. This allows for a consistent connection make up that is required at higher pressures and temperatures. When the gland nut is threaded into the connection, the tubing is locked securely in place and the
possibility for the ejection of the tubing from a properly assembled and used connection is extremely remote.
Remarks:
Since the glands and threaded collars can be removed from the tubing, properly lubricated Parker Autoclave Engineers Medium-Pressure and High-Pressure connections can be disassembled and reassembled repeatedly without loss of relability. These connections are used with cold-worked valve and fitting bodies which can withstand many repeated sealings. Therefore, valves, fittings and accessories can be inserted or removed from the pressure system or the system can bealtered or expanded in a fraction of the time and cost that may be imposed by welded, screwed, flared or other types of connections.
Vacuum Service:
Parker Autoclave Engineers’ Medium-Pressure connections can be reliably used in light vacuum service to 10-2 torr. Parker Autocalve Engineers’ High-Pressure connections are recommended for vacuum to 10-5 torr. Extreme care and proper seal lubrication are required to successfully achieve these levels of vacuum.
Pressure Cycling:
Since the metal to metal seal is pre-torqued to a specified value greater than the end load generated from the pressure, fatigue concerns of the connection due to pressure cycling are minimal.
Thermal Cycling:
Because of the threaded on collar design, Parker Autoclave Engineers’ Medium and High-Pressure connections can take repeated thermal cycling under pressure with no loss in reliability. These connections can also handle a wider range of temperatures than swaged or bite type connections and are designed to maintain integrity from -423°F to 1200°F (-252°C to 649°C).
Pre-Rated Systems:
Valves, fittings and tubing with Parker Autoclave Engineers’ Medium and High-Pressure connections provide a fully engineered, pre-rated system of components that are interchangeable from assembly to assembly. They are not over sensitive to abuse or careless assembly and no special gauges or tools are
needed to check the connection. Weep holes are provided in every connection to permit fast visual inspection for leakage, and prevent pressure build up in the threads.
Materials:
Parker Autoclave Engineers’ standard gland and collar material is type 316 cold-worked stainless steel. This material provides high strength and good impact resistance over the temperature range mentioned above. A bonded dry film lubricant, to be used as an anti-galling agent, is available.
Parker Autoclave Engineers’ Medium Pressure Coned and Threaded Connections
Features:
- Pressures to 20,000 psi (1379 bar)
- Uncompromised reliability under rigorous thermal and pressure cycling.
- Design is a more compact version of the original Parker Autoclave Engineers High Pressure connections.
- Well suited to installations which require repeated assembly and disassembly with consistent reliability.
- Available in tube outside diameter sizes from 1/4”(6.35 mm) through 1-1/2” (38.10 mm) and bore sizes from .109”(2.77 mm) to .938”(23.83 mm).
Note: 1″ 43,000 psi (2965 bar) utilizes the medium pressure coned-and-threaded connection.
Parker Autoclave Engineers’ High Pressure Coned and Threaded Connections
Features:
- Pressures to 60,000 psi (4137 bar)
- Increased pressure handling capabilities
- Uncompromised reliability under rigorous thermal and pressure cycling
- Well suited to installations which require repeated assembly and disassembly with consistent reliability.
- Available in tube outside diameter sizes of 1/4” (6.35mm), 3/8”(9.53mm) and 9/16”(14.27mm) and bore sizes of .083(2.11mm), .125”(3.18mm), .188”(4.78mm) and .250”(6.35mm).
PRESSURE / TEMPERATURE RATING GUIDE
Information in this rating guide is furnished to approximate the pressure/temperature capabilities of Parker Autoclave Engineers valves and fittings with various options.
To determine approximate ratings, the following factors should be considered:
- Refer to valve or fitting ordering pages for the base pressure rating of component at room temperature (R.T.).
- Refer to Technical Information section for pressure ratings of materials at elevated temperatures.
- Refer to appropriate tubing section for pressure ratings of standard Parker Autoclave Engineers’ tubing at various temperatures to 800°F (427°C).
- Note maximum temperature ratings for Parker Autoclave Engineers’ valves with various packing and stem options in table below.
- Note pressure/temperature curve below for type 316 stainless steel bodies and tubing.
- Note temperature information checklist below.
