The new environmental protection policy of reduction in volatile organic compound and particularly hazardous compound leakage resulting from chemical processes and plant equipment was released for the human concern by the Environmental Protection Agency in U.S.A in 1990. The new law required the plant handling the toxic gas to periodically monitor the leakage for not exceeding 500 ppm. If so then the equipment is to be repaired or replace.
In 1995, the leak level was restricted to below 100 ppm and is expected that such restriction will be more stringent in all countries in the world. Spire Industrial Equipments Co. with several testing, have designed, engineered and manufactured low emission valves to meet the 100 ppm maximum emission level. Gate & Globe valves are meeting the requirement of TA-LUFT and with reference to VDI 2440. The major design considerations for having achieved this performance are as below.
Flexible graphite packing set consist of 04 die formed flexible graphite rings and 02 braided flexible graphite rings, along with pure carbon bush.
Spiral wounded flexible graphite filler and stainless steel hoop is provided.
Small Diametrical interface clearance between vital parts like stem to gland, stem to bonnet bushing, gland to stuffing box.
Stem and Stuffing box
6 to 32 RMS surface finish is provided for stem. Straightness and roundness are precision controlled for super finish. 63 to 125 RMS surface finish is provided for Stuffing box. Cylindricity and verticality are precision controlled in manufacturing.
Lantern ring is provided with double packing set in critical service (as shown in figure) with a leak-off connection. The leak-off is provided to allow collection of leakage from the packing set.
Packing Ring compression
Each packing rings are compressed in stuffing box to ensure equal stress distribution of all rings
Two sets of Belleville springs are provided above the gland flange to maintain permanent packing stress. This feature provide longer life to low emission valves at frequent pressure and temperature transients.
Stainless Steel plate is affixed to the body flange indicating "LOW EMISSION"