08 Nov Cost and Performance Advantages
COST AND PERFORMANCE ADVANTAGES
DOCUMENT NUMBER: TB110
BY: CURTIS SCHMIDT, MS, PE
SHORT HISTORY OF THE BYPASS PRD
Given the niche nature of the flare bypass market, it has been slow to keep up with the technology
improvements of other industrial devices. The staging valves for instance, have been available in single,
double and triple offset designs since the 1970’s. They have had a variety of control systems put in place
to optimize their function and it has been shown the new triple offset seal design is the best and most
robust option in the market.
In this same period the bypass devices have changed little in technology, only recently moving from the
rupture disc style device to using a 90 degree buckling pin device or a double offset butterfly valve style
pressure relief device.
The butterfly style pin device is the only option that offers the economy of the butterfly staging valves
without the inconvenience of the past rupture discs. However, while the staging valves have embraced the
benefits of triple offset metal seals the bypass devices stagnated at double offset elastomeric seals. These
seals are limited in temperature and accuracy is often hindered by frictional effects.
The AccuShear pressure relief device brings the bypass devices up to the level of the currently used
staging devices, utilizing the same robust triple offset metal seal.
PERFORMANCE ADVANTAGES OF THE ACCUSHEAR:
The patented triple offset seal and associated pre-load technology of the AccuShear results in:
More reliable performance as un-predictable seating and breaking frictional forces are nearly
Temperature ranges that match the staging valve as both devices utilize the same fundamental
Tighter operational window as the new technology facilitates higher performance allowing
operating pressure closer to set pressures
Ease of re-setting as the shear pin is much easier to replace than previous technologies
More economical as the design is simple and robust utilizing far less precision machined parts
than other pressure relief devices.