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Packing acts like a labyrinth seal
Dynamic sealing
Sintered Sic with spherical porosity Hexoloy SP Sic is a new sintered alpha silicon carbide material designed for optimum performance in sliding contact applications such as pump seal faces and product lubricated bearings. Carborundum says this material improves upon the corrosion and erosion resistance properties of sintered alpha Sic through the addition of spherical pores. These pores are discrete, non-interconnecting and dispersed in a controlled manner throughout the body of the material. The spherical pores act as fluid or lubricant reservoirs helping to promote the retention of a fluid film at the interface of sliding component surfaces. According to the maker, this “pore” based lubrication mechanism allows Hexoloy SP Sic to outperform conventional reaction-bonded and sintered silicon carbides in a wide variety of severe seal and bearing applications.
Split seal expands performance envelope A new split seal has been announced by Flexibox, which it says exhibits leakage rates under stable operating conditions comparable with those achieved by mechanical seals employed in environmentally sensitive applications.
Contact: Carborundum Structural Ceramics Division, PO Box 1054, Niagara Falls, NY 14302, USA. Tel: +l 716 278 2150: Fax: +l 716 278 2373.
The Sectaflex seal is a balanced split seal, designed for extended life. The carbon/silicon carbide face combination is standard, but the hard face combination of silicon carbide/silicon carbide is available for abrasive applications. Flexibox claims that, with a maximum pressure rating of 300 psig, the operating envelope for standard split seals has been greatly extended. Stable pressure at the seal faces is provided, and clogging or corrosion prevented, by the use of stationary multi-springs, isolated from the product and external environment. A seal face wear indicator gives early warning for planning of maintenance. The seal was designed with the minimum of components in order to facilitate installation. Adhesive is not required and the seal is supplied with a C-ring for axial and radial positioning. Contact: Flexibox, Inc., 2407 Albright Drive, Houston, Texas 77017, USA. Tel: +l 713 944 6690; Fax: +1713 946 8252.
Packing acts like a labyrinth seal Spherical
pores help retain the fluid film.
Sealing Technology
No. 28
An evolutionary improvement in New England Braiding’s Anti-Keystone packings has been made. This newly patented improvement changes the shape of the packing when it is installed, creating a void
3
Dynamic sealing between the rings of packing at the shaft. This void enables Anti-Keystone II Packing to consume up to 80% less power when compared to conventionally braided packings, according to the makers. Originally, this modification to the trapezoidal cross section was intended to add mass to the outer half of the packing. This helps to prevent spinning of rings that are not seated fully during installation. However, a significant side effect was discovered after the patent filing, in that the modified packing acted like a braided labyrinth seal. The voids remaining between the rings at the shaft sleeve provide a space for the fluid film to reside with added dwell time. Slowing the fluid’s passage between shaft and packing has two advantages: l
l
Pressure drops proportionally at each void, lowering the leakage rate. Increased non-contact packing surface area raises the heat transfer rate through the packing, lowering the shaft sleeve temperature.
Independent l
l
tests by a licensee indicate that:
At moderate pressures - approx 45 psi - an 80% reduction in power consumption is possible compared to conventionally braided packings of the same iibre and under the same conditions. At high pressures - approx 264 psi - power consumption is still reduced by 20% over conventionally braided packings.
The company says that as well as enhanced performance on rotating equipment such as pumps and agitators, the packing performs well in reciprocating services. Contact: New England Braiding Company, PO Box 4917, Manchester, New Hampshire 03108-4917, USA. Tel: + 1603 669 1987; Fax: +1603 669 4121.
Imnroved braiding enhances packin; performance Two braided packing products have been launched by Utex Industries Inc. Utex Style 686 Tex Flex is a packing comprised of pure flexible graphite, which has been expanded and made into a braidable yarn. The finished product retains the properties of flexible graphite such as heat resistance, chemical inertness, self lubrication and conformability, but incorporates an active corrosion inhibitor to reduce pitting on sleeves and stems. The manufacturer claims Tex-Flex is easier to install than graphite in ribbon or tape form as it does not tear or unravel when cut or handled like tape. Style 686 does not break down in service, but conforms to shafts and stuffing boxes under gland pressure. The product need not be removed when repacking the box, as the gland can be backed off, a ring of packing added and the gland retightened.
4
Typical applications are pumps and valves handling steam, condensate, boiler feed water and chemicals. Style 687 packing uses the strength of carbon yarn reinforcement. Tex-Flex ribbon is braided with pure carbon strands in the corners to add strength and provide anti-extrusion properties under high pressure. The braiding technique has been developed to keep the carbon oriented properly in the corner to maximise the sealing effect. The material is suited to applications like centrifugal pumps, gear pumps, rising stem valves, chokes and agitators. Contact: Utex Industries Inc., PO Box 79227, Houston, Texas 77279, USA. Tel: +l 713 467 1000: Fax: +l 1800 359 9230.
Hydrogenated nitrile seals for braking system A special hydrogenated nitrile compound for seals within the braking system of the new Terex 55 tonne payload off-highway rigid truck, has been developed by Precision Polymer Engineering. The rear axle multi-plate, oil immersed discs, have a large diameter and a high flow cooling system, and give the hydraulic braking system excellent steep grade or long-duration braking. The PPE hydrogenated nitrile compound endures the high temperature and stress conditions that occur in oil cooled brakes. The seals, which are 25” and 28” in size play a key part in stopping the trucks 95 tonne weight. Contact: Precision Polymer Engineering, Clarendon Road, Blackbum BBl 988, UK. Tel: +44 1254 679916; Fax: +44 1254 680182.
Split seal for rapid installation The difficulties encountered when attempting seal changeout in large equipment or equipment in awkward locations can be alleviated according to Flex-A-Seal, with its Style 85 split cartridge seal. The stationary cartridge design prevents the springs from rotating with the shaft and compensates for misalignment between box face and shaft, facilitating higher speeds. A positive set screw assembly prevents axial motion. Cartridge style setting clips assure radial and axial alignment and permit simple impeller adjustment. Sealed equipment does not need to be diassembled, with the Style 85. All the components -
Sealing Technology
No. 28
Sintered Sic with spherical porosity Hexoloy SP Sic is a new sintered alpha silicon carbide material designed for optimum performance in sliding contact applications such as pump seal faces and product lubricated bearings. Carborundum says this material improves upon the corrosion and erosion resistance properties of sintered alpha Sic through the addition of spherical pores. These pores are discrete, non-interconnecting and dispersed in a controlled manner throughout the body of the material. The spherical pores act as fluid or lubricant reservoirs helping to promote the retention of a fluid film at the interface of sliding component surfaces. According to the maker, this “pore” based lubrication mechanism allows Hexoloy SP Sic to outperform conventional reaction-bonded and sintered silicon carbides in a wide variety of severe seal and bearing applications.
Split seal expands performance envelope A new split seal has been announced by Flexibox, which it says exhibits leakage rates under stable operating conditions comparable with those achieved by mechanical seals employed in environmentally sensitive applications.
Contact: Carborundum Structural Ceramics Division, PO Box 1054, Niagara Falls, NY 14302, USA. Tel: +l 716 278 2150: Fax: +l 716 278 2373.
The Sectaflex seal is a balanced split seal, designed for extended life. The carbon/silicon carbide face combination is standard, but the hard face combination of silicon carbide/silicon carbide is available for abrasive applications. Flexibox claims that, with a maximum pressure rating of 300 psig, the operating envelope for standard split seals has been greatly extended. Stable pressure at the seal faces is provided, and clogging or corrosion prevented, by the use of stationary multi-springs, isolated from the product and external environment. A seal face wear indicator gives early warning for planning of maintenance. The seal was designed with the minimum of components in order to facilitate installation. Adhesive is not required and the seal is supplied with a C-ring for axial and radial positioning. Contact: Flexibox, Inc., 2407 Albright Drive, Houston, Texas 77017, USA. Tel: +l 713 944 6690; Fax: +1713 946 8252.
Packing acts like a labyrinth seal Spherical
pores help retain the fluid film.
Sealing Technology
No. 28
An evolutionary improvement in New England Braiding’s Anti-Keystone packings has been made. This newly patented improvement changes the shape of the packing when it is installed, creating a void
3
Dynamic sealing between the rings of packing at the shaft. This void enables Anti-Keystone II Packing to consume up to 80% less power when compared to conventionally braided packings, according to the makers. Originally, this modification to the trapezoidal cross section was intended to add mass to the outer half of the packing. This helps to prevent spinning of rings that are not seated fully during installation. However, a significant side effect was discovered after the patent filing, in that the modified packing acted like a braided labyrinth seal. The voids remaining between the rings at the shaft sleeve provide a space for the fluid film to reside with added dwell time. Slowing the fluid’s passage between shaft and packing has two advantages: l
l
Pressure drops proportionally at each void, lowering the leakage rate. Increased non-contact packing surface area raises the heat transfer rate through the packing, lowering the shaft sleeve temperature.
Independent l
l
tests by a licensee indicate that:
At moderate pressures - approx 45 psi - an 80% reduction in power consumption is possible compared to conventionally braided packings of the same iibre and under the same conditions. At high pressures - approx 264 psi - power consumption is still reduced by 20% over conventionally braided packings.
The company says that as well as enhanced performance on rotating equipment such as pumps and agitators, the packing performs well in reciprocating services. Contact: New England Braiding Company, PO Box 4917, Manchester, New Hampshire 03108-4917, USA. Tel: + 1603 669 1987; Fax: +1603 669 4121.
Imnroved braiding enhances packin; performance Two braided packing products have been launched by Utex Industries Inc. Utex Style 686 Tex Flex is a packing comprised of pure flexible graphite, which has been expanded and made into a braidable yarn. The finished product retains the properties of flexible graphite such as heat resistance, chemical inertness, self lubrication and conformability, but incorporates an active corrosion inhibitor to reduce pitting on sleeves and stems. The manufacturer claims Tex-Flex is easier to install than graphite in ribbon or tape form as it does not tear or unravel when cut or handled like tape. Style 686 does not break down in service, but conforms to shafts and stuffing boxes under gland pressure. The product need not be removed when repacking the box, as the gland can be backed off, a ring of packing added and the gland retightened.
4
Typical applications are pumps and valves handling steam, condensate, boiler feed water and chemicals. Style 687 packing uses the strength of carbon yarn reinforcement. Tex-Flex ribbon is braided with pure carbon strands in the corners to add strength and provide anti-extrusion properties under high pressure. The braiding technique has been developed to keep the carbon oriented properly in the corner to maximise the sealing effect. The material is suited to applications like centrifugal pumps, gear pumps, rising stem valves, chokes and agitators. Contact: Utex Industries Inc., PO Box 79227, Houston, Texas 77279, USA. Tel: +l 713 467 1000: Fax: +l 1800 359 9230.
Hydrogenated nitrile seals for braking system A special hydrogenated nitrile compound for seals within the braking system of the new Terex 55 tonne payload off-highway rigid truck, has been developed by Precision Polymer Engineering. The rear axle multi-plate, oil immersed discs, have a large diameter and a high flow cooling system, and give the hydraulic braking system excellent steep grade or long-duration braking. The PPE hydrogenated nitrile compound endures the high temperature and stress conditions that occur in oil cooled brakes. The seals, which are 25” and 28” in size play a key part in stopping the trucks 95 tonne weight. Contact: Precision Polymer Engineering, Clarendon Road, Blackbum BBl 988, UK. Tel: +44 1254 679916; Fax: +44 1254 680182.
Split seal for rapid installation The difficulties encountered when attempting seal changeout in large equipment or equipment in awkward locations can be alleviated according to Flex-A-Seal, with its Style 85 split cartridge seal. The stationary cartridge design prevents the springs from rotating with the shaft and compensates for misalignment between box face and shaft, facilitating higher speeds. A positive set screw assembly prevents axial motion. Cartridge style setting clips assure radial and axial alignment and permit simple impeller adjustment. Sealed equipment does not need to be diassembled, with the Style 85. All the components -
Sealing Technology
No. 28