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Balanced Single Seat Trim Double Seat Trim
For moderately low temperature applications, up to 450°F (232°C), the Balanced Single Seat option is available. In this version the upper seat of the plug is removed and a flexible “U” cup seal is provided at the top of the cage. This seal is energized by fluid pressure passing through holes drilled in the plug crown and effectively makes a seal between the outside of the cage and the inside of the plug. The GAD double seat trim is ideal for continuous modulating high mass flow rate applications requiring only nominal shutoff. It has top and bottom seats on both the plug and cage, and the net out-of-balance area between the two seats is kept to an absoluteminimum by the seats being struck off acommon line, i.e. the outside diameter of the cage. The valve trim is not affected by temperature or pressure fluctuations and a considerably better shutoff can be achieved,compared to that of conventional double seat trim. It is possible to achieve Class III of ANSI B16.104 which is equivalent to 0.1% of rated valve capacity. Trim balance is achieved by a series of holes drilled in the plug crown through which inlet pressure isadmitted. This acts on both the top and underside of the plug crown and on the plug’s bottom edge. Balanced Single Seat Tandem Double Seat Single Stage Hush Tandem Trim
In the Tandem Trim version, the top seats on the plug and cage have been removed and the trim is effectively a single seat design. A spring loaded pilot valve is provided in the main plug crown which in the open position allows high inlet pressure to pass through and act on the underside of the plug crown. This balances the forces on both sides of the crown.When the plug is on its seat the pilot valve plug closes and the inlet pressure acts on top of the main plug crown only, as the underside of the crown is exposed to the downstream pressure conditions. This ensures that positive shutoff is achieved and considerable seating force is employed.The initial upward movement of the valve stemopens the pilot valve, allowing the high inlet pressure to pass through to the underside of the main plug crown, thus balancing the pressures acting on the plug and enabling relatively small actuators to be employed in repositioning the plug. A spring is provided in the pilot valve to ensure that in the open position the pilot valve remains open and does not hunt. Single Stage Hush
™ Trim
(Available on each of the preceding options) Where the level of noise generated by the standard trim is above acceptable limits, a Single Stage Hush ™ trim option is availablegiving a degree of attenuation. In place of the normal characterized ports there is a series of drilled holes which are designed to break the mass flow down into a series of small streams, which effectively change the frequency of any noise generated to achieve the required attenuation. These holes are arranged in rising spirals and give a continuous linear characteristic when uncovered progressively as the plug rises. Sales and Service
For information about our worldwide locations, approvals and certifications, and local representatives, please visit our web site. Web Site: www.spxvalves.com E-Mail: info@spxvalves.com 250 Riverside Ave. N. Sartell, Minnesota 56377-1743 Telephone: 320-259-2000 Fax: 320-259-2227 SPX Valves & Controls reserves the right to incorporate our latest design and material changes without notice or obligation.Design features, materials of construction and dimensional data, as described in this bulletin, are provided for your information onlyand should not be relied upon unless confirmed in writing by SPX Valves & Controls. Certified drawings are available upon request. Printed in the U.S.A. 010302
For moderately low temperature applications, up to 450°F (232°C), the Balanced Single Seat option is available. In this version the upper seat of the plug is removed and a flexible “U” cup seal is provided at the top of the cage. This seal is energized by fluid pressure passing through holes drilled in the plug crown and effectively makes a seal between the outside of the cage and the inside of the plug. The GAD double seat trim is ideal for continuous modulating high mass flow rate applications requiring only nominal shutoff. It has top and bottom seats on both the plug and cage, and the net out-of-balance area between the two seats is kept to an absoluteminimum by the seats being struck off acommon line, i.e. the outside diameter of the cage. The valve trim is not affected by temperature or pressure fluctuations and a considerably better shutoff can be achieved,compared to that of conventional double seat trim. It is possible to achieve Class III of ANSI B16.104 which is equivalent to 0.1% of rated valve capacity. Trim balance is achieved by a series of holes drilled in the plug crown through which inlet pressure isadmitted. This acts on both the top and underside of the plug crown and on the plug’s bottom edge. Balanced Single Seat Tandem Double Seat Single Stage Hush Tandem Trim
In the Tandem Trim version, the top seats on the plug and cage have been removed and the trim is effectively a single seat design. A spring loaded pilot valve is provided in the main plug crown which in the open position allows high inlet pressure to pass through and act on the underside of the plug crown. This balances the forces on both sides of the crown.When the plug is on its seat the pilot valve plug closes and the inlet pressure acts on top of the main plug crown only, as the underside of the crown is exposed to the downstream pressure conditions. This ensures that positive shutoff is achieved and considerable seating force is employed.The initial upward movement of the valve stemopens the pilot valve, allowing the high inlet pressure to pass through to the underside of the main plug crown, thus balancing the pressures acting on the plug and enabling relatively small actuators to be employed in repositioning the plug. A spring is provided in the pilot valve to ensure that in the open position the pilot valve remains open and does not hunt. Single Stage Hush
™ Trim
(Available on each of the preceding options) Where the level of noise generated by the standard trim is above acceptable limits, a Single Stage Hush ™ trim option is availablegiving a degree of attenuation. In place of the normal characterized ports there is a series of drilled holes which are designed to break the mass flow down into a series of small streams, which effectively change the frequency of any noise generated to achieve the required attenuation. These holes are arranged in rising spirals and give a continuous linear characteristic when uncovered progressively as the plug rises. Sales and Service
For information about our worldwide locations, approvals and certifications, and local representatives, please visit our web site. Web Site: www.spxvalves.com E-Mail: info@spxvalves.com 250 Riverside Ave. N. Sartell, Minnesota 56377-1743 Telephone: 320-259-2000 Fax: 320-259-2227 SPX Valves & Controls reserves the right to incorporate our latest design and material changes without notice or obligation.Design features, materials of construction and dimensional data, as described in this bulletin, are provided for your information onlyand should not be relied upon unless confirmed in writing by SPX Valves & Controls. Certified drawings are available upon request. Printed in the U.S.A. 010302