ARAMCO Replaces Noisy Flare Pressure-Control Valve

As a part of a gas-to-flare upgrade program, ARAMCO has replaced a noisy pressure-control valve with DRAG® technology to hold noise levels at Uthmaniyah-Khuff to less than 90 dBA without thermal or acoustic padding on the downstream pipe. In order to avoid similar problems that have been experienced with the type of valve being replaced, the end user has decided to install a CCI DRAG® valve based on success achieved with CCI valves in the past.

This balanced, six inch x eight inch (150-millimeter x 200-millimeter) balanced, under-the-plug DRAG® valve will control velocity head (Hv) to less than 70 psi (4.8 Bar) to limit the sound-power level to a maximum of 90 dBA. Pressure-equalizing rings (PERs) are provided to assure equal pressure distribution around the plug to prevent flow-induced vibration.

The valve is designed for a maximum flow of 196,000 pounds/hour (90,000 kilograms/hour) at a specific gravity of 0.7700 to provide a 10-percent over-capacity margin. Maximum inlet pressure is 332 psig (23 BarG); maximum differential pressure of 280 psi (20 Bar) at 103 F (40 C).

PCS Nitrogen, Ltd. In Trinidad Replaces Failed Atmospheric Vent Valve

A single-seat globe valve onhigh-pressure venting service at PCS Nitrogen, LTD’s Point Lisas Ammonia Plant in Trinidad failed due to high vibration, mechanical failures such as stem breakage, and resultant poor control.

It has now been replaced with a 12-inch (300-millimeter) DRAG® multi-stage pressure reduction control valve rated at 417,000 pounds/hour (190,000 kilograms/hour) with an inlet pressure of 600 psia (41 BarA) and a DP as high as 408 psi (28 Bar) at 250 F (121 C).

To minimize noise and vibration, the trim exit kinetic energy (velocity head – Hv) is limited to 70 psi (4.8 Bar). Noise levels of 86 dBA maximum at 3 feet (1 meter) are based on no thermal padding or insulation on the down-stream piping. To prevent flow-induced plug vibration, pressure-equalizing rings (PERs) are provided on the inside diameter of each multi-stage pressure reduction disk in the trim stack. The plug is balanced to minimize the pneumatic actuator loading.

Meeting Extreme PRC Requirement with Noise-Control Technology

The People’s Republic of China ’s Natural Gas Transmission and Distribution Dept. in Chengdu recently ordered four gas header pressure-control valves, with exceedingly low noise-level specifications for this service. Under all operating conditions, sound-power-level emissions are required to be less than 60 dBA at 3 feet (1 meter), and are based on no thermal or acoustic padding on the downstream piping.

CCI’s unique and demonstrated ability to meet this extremely low noise requirement – perhaps as much as 25 dBA below the normal requirements for this service – convinced the PRC engineers that CCI’s DRAG® technology was the only design approach that would meet their stringent needs.

These four 12-inch x 14-inch (300-millimeter x 350-millimeter) control valves are designed for a future gas flows of up to 88,000 CFM (150,000 meters3/hour). Inlet pressures range up to 800 psig (4.5 MPaG) with future DPs of 2.2 MPa. To meet the extremely low noise levels specified, a large number of right-angle turns/pressure-reduction stages (as many as 44), were required.

Published in SOLUTIONS Winter 2000