SEPCO Puts Life into Die-Formed Rings
Standard die forming of Grafoil squeezes the life out of the ring. That is why we pre-form.We put compressibility and resilience into each flexible graphite ring and that is what makes the difference. When you receive a pre-formed ring from SEPCO, it still has 15% to 20% compressibility left in it. As you install the ring, it’s only necessary to tighten the packing until a seal is effected, which leaves considerable life in the ring for future adjustments. The extra care we take makes the difference.
Note: For clearances greater than .020 between stem and stuffing box, SEPCO suggests a single ring of ML-4444 braided flexible graphite packing in bottom of stuffing box as an anti-extrusion ring.
Consider the Benefits of Die-Formed Grafoil
- Individually formed to meet your specific dimensions.
- Slight interference fit to bore and stem to insure a tight seal.
- Less waste than conventional coils of packing.
- No need to pull old packing out. Simply add rings when needed.
- Each ring molded to 85 lbs. per cu. foot.
- Even distribution of work load to each ring.
SEPCO Die-Formed Cartridge Grafoil
Single Grafoil cartridge die molded to 90 lbs. per cubic foot density with a slight interference fit on the stem and the stuffing box bore.
SEPCO can also furnish packing rings fabricated from layers of Grafoil sheet. Because these rings sets do not have the compressibility and resilience of our pre-formed rings, equipment dimensions and equipment conditions are critical. A SEPCO representative should be consulted. Unlike pre-formed rings, heat conductivity and expansion characteristics are very directional with these packing rings.
The SEPCO Die-Formed Grafoil Cartridge offers the following advantages.
- Only one ring to install. Pack the complete box in the time it takes to install one ring. A labor savings of 75%.
- Slight interference fit to bore and stem insuring a tight seal.
- Cartridge is pre-compressed to 90 lbs. per cubic foot density insuring even distribution of gland pressure along the entire stem area.
- More economical due to lower manufacturing cost.
- Due to the superior sealing and heat transfer properties of Grafoil, some valve manufacturers have redesigned bonnets for shallower stuffing boxes and thinner walls, a material savings.
SEPCO Grafoil Gaskets
- Leak free performance at moderate bolt loads.
- No cold flow or creep.
- Precision bolt tightening unnecessary.
- No flange sticking.
Gasket Loading vs. Leakage Pressures
The prime requirement for satisfactory sealing with Grafoil gaskets is sufficient unit load on the gasket at all times and at all points on the gasket.
If surfaces are maintained flat and within 0.005 inches and are held to a surface finish of 125 RMS or better, Grafoil gaskets will seal hydrostatic pressures as shown on the graph “Leak Pressure vs. Gasket Unit Load for Grafoil Gaskets.” For example, a Net Unit Load of 7,000 p.s.i. will seal up to 3,150 p.s.i water pressure.