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ARTICLES
FLOW SAFE PILOT OPERATED RELIEF VALVES
by John Paul Heston
Posted by Devtech
Flow Safe was founded in 1995 as a manufacturer of high quality safety relief valve products. Flow Safe entered the market with several goals in mind. These goals are outlined in their company policy and are in place to offer a commitment to value through: environmentally compatible products, cost efficient design with minimal parts, quality products that are readily available, flexibility in meeting unique customer needs, and no hassle service. These core ideas and beliefs backed by a family owned company make for a great combination, and one of the main reasons Devtech is a proud representative of Flow Safe.
Flow Safe was founded in 1995 as a manufacturer of high quality safety relief valve products. Flow Safe entered the market with several goals in mind. These goals are outlined in their company policy and are in place to offer a commitment to value through: environmentally compatible products, cost efficient design with minimal parts, quality products that are readily available, flexibility in meeting unique customer needs, and no hassle service. These core ideas and beliefs backed by a family owned company make for a great combination, and one of the main reasons Devtech is a proud representative of Flow Safe.
Pilot operated relief valves are considered to be the most reliable type of overpressure protection in the gas industry. Flow Safe manufactures two pilot operated relief valves for the natural gas industry, the F70PR and the F7000/8000. Both of these relief valves have their specific niche within the distribution and transmission sides of the natural gas industry. All Flow Safe relief valves for the natural gas industry are soft seated valves and bubble tight upon closure. The F70PR is mainly used in natural gas distribution systems (lower pressure applications from 10" wc to 285 psig) and the F7000/8000 in transmission systems (higher pressure applications from 15 psig to 6000 psig).
The F70PR as stated above is a great product for distribution systems with pressures between 10" wc and 285psig. The F70PR comes in sizes from 1 ?" to 12" and in two separate designs. There is an F70PR low pressure assembly and an F70PR high pressure assembly. The only difference in these valves is that the F70PR low pressure assembly utilizes the F100 low pressure pilot which has an aluminum bodied diaphragm to be able to hold set pressures as low as 10" wc. The F70PR high pressure assembly uses the F100 pilot to handle the desired set pressure. The F100 pilot is a 5% pilot. What is meant by a 5% pilot is that the pilot allows the valve to fully open by modulating pressure within 5% of upset and also fully reseat within 5% of the set point. The F70PR has the ability to handle large volumes while providing consistent, bubble tight shutoff before and after a system upset (overpressure). The F70PR utilizes modulating action via the pilot applying differential pressure to the piston to ensure process efficiency as well as reduce product loss. Another benefit of Flow Safe's pilot operated valves both the F70PR and the F7000/8000 is the field test connection (FTC) fitting. This fitting allows the user to verify the set pressure while in service without valve removal. An external pressure source (pressurized gas can, etc...) is attached to the FTC to direct pressure to the pilot valve, while blocking off the inlet pressure, thus checking the set pressure and the general operation of the valve via the pilot regulator.
The F7000/8000 is an excellent valve for the transmission companies, while also supporting applications in distribution systems, and comes in sizes from 1" to 12". The F7000/8000 valve is an ASME compliant valve as well as NACE, ANSI, and DOT. This valve can accommodate pressures from 15psig to 6000psig, while offering full relief capabilities and bubble tight shutoff at all ranges within it capabilities. The F7000/8000 unlike the F70PR has two options for pilot valves, modulating and snap-acting. The most commonly used pilot valve is the F300. The F300 is a 3% modulating/flowing valve which begins to relive at 3% of set pressure while modulating with full relief at set pressure. The F200 pilot valve is a 1% non-flowing/snap acting valve which starts to relieve at 1% of set pressure with full relief at set pressure. The main difference in the two pilots is the F300 modulates relieving flow proportionate to upset while the F200 is either full open or full close. Having options for the pilot valves is just one of the many reasons the F7000/8000 relief valve is particularly advantageous and cost-effective. Some of the other reasons are if high cycling rate exists, a long service life is required, minimal product loss is important, and reduced maintenance and installation time is desirable. Just as the F70PR the F7000/8000 relief valves have no metal to metal contact of piston to liner assembly, thus limiting the wear usually seen when metal to metal contact occurs. All Flow Safe pilot operated reliefs are straight inlet and right angle outlet. This orientation accounts for ease of maintenance/inspection, extended capacity versus regulator reliefs, and longer life due to keeping moisture/elements out of the valve.
As one can see from the above information Flow Safe has invested a lot of time and great ideas into providing a great product for the natural gas industry. Flow Safe's relief valves will prove to be one of the more beneficial and longer lasting pieces of equipment within one's natural gas system, whether distribution or transmission. Flow Safe's commitment to value through: environmentally compatible products, cost efficient design with minimal parts, quality products that are readily available, flexibility in meeting unique customer needs, and no hassle service, is a true testament to the equipment they provide whether it be a pilot operated relief valve on any relief valve from their extensive portfolio.