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We are installing a hot gas bypass to protect centrifugal compressor from surge following ESD. The design includes two 24-inch check valves immediately downstream of the bypass line to minimise the compressor discharge volume that needs to be depressured. The required opening time of the bypass...

The possibility of ice formation in the flare system when high pressure wet gas stream from a separator is relieved to flare looks very high. If two-phase relief flow including the free water is considered, the situation looks even worse. Does anyone know thow these scenarios are mitigated...

The possibility of ice formation in the flare system when high pressure wet gas stream from a separator is relieved to flare looks high. If two-phase relief flow including the free water is considered, the situation looks worse. Does anyone know thow these scenarios are mitigated against? I...

The crane cab is cited as one of the positions critical with respect to flare radiation. Should credit be taken if cab is air conditioned? If so, how do we factor A/C into the radiant heat predictions.

It's the the builtup plus superimposed backpressure. We don't find that much of a balancing out effect. Valve A has slightly higher backpressure, but this is more than compensted for by the difference in Kb. The 16% overpressure valve with the lower set point has around 8-10% more capacity...

We have 2 identical balanced bellows type PSVs. PSV A is set at 9.5 barg and PSV B 10 barg. They both protect the same equipment which has a 10 barg design pressure. PSV A has a 16% overpressure, PSV B has 10% overpressure. Each PSV has a backpressure of 4 barg. When I refer to API 520, Figure...

To Big Inch. The 2-in PSV inlet is taken off a 2-in process line. The pressure drop is taken from entrance to the 2-in inlet to the PSV inlet flange. On other PSVs with larger inlets, the inlet vent valve is fitted onto a Nipoflange and issue of a Tee doesn't arise (no Tee has been allowed for...

Thanks for your responses. It's a welded, 2 x 3/4 inch reducing Tee.

On a 2-inch inlet line to a PSV we have an installed Tee fitting with a blanked vent valve taken off the Tee branch. The equivalent length of a Straight through Tee is dominating the friction losses in the PSV inlet line generating losses exceeding API 3% guideline. If there is no flow to or...

The PSV is a modulating pilot which can accept considerably higher backpressures than 14 barg. I think our initial concern has been laid to rest.

JoeWong88 thanks for your comments. Our current thinking is that the pressure downstream of the psv nozzle will incease. Provided the increased pressure is below the PSV critical flow pressure, relief capacity will not unaffected.

PSV has a 6-inch outlet. We have input the PSV data into our Flarenet model with following result; Flowrate = 308,136 kg/h PSV backpressure = 14 barg. PSV 6-inch outlet flange Mach No. = 1 If we increase to 8-inch outlet; Flowrate = 308,136 kg/h PSV backpressure = 14 barg. Mach No at 8-inch...

My concern is that we get sonic at the outlet flange at lower than psv design throughputs. Does this suggest that the psv capacity may be affected?

When we run several of our PSVs in Flarenet we get mach one at the PSV outlet flanges. Does this mean these flanges are undersized? In some cases we need to go up two sizes to avoid sonic.

Can the Mach number be allowed to reach 1.0 in the PSV disposal system piping?

Hello, I'm trying to determine the consequences to the DGS system in the event of a compressor blowdown. If using the compressor gas a source for DGS, is the seal is lost? Further, the potential for low blowdown temperatures may give rise to liquid formation and possible damage to the DGS...

We have vendor pump curve that report NPSH required in feet of water, which I understand is the norm. The fluid being pumped is pentane. Given the differences in vapour pressures and densities between pentane and water, using NPSHr for water surely can't be right. The NPSH available has been...

Morten, could you elaborate on your answer? I'm hearing from others the benefits of placing valve upstream, such as single phase to valve, lower pressure rating for exchanger, possible saving of a relief valve, and avoid leakage into tower feed rather than product (heating medium is column...

A bubble point liquid feed from a separator is preheated in an exchanger before entering a stabilizer tower. There is a control valve in the feed line where pressure is letdown from separator pressure (20 bar) to stabilizer pressure (8 bar). Should the control valve be located upstream or...

As a rule of thumb, for a A bubble point liquid feed from a separator is preheated in an exchanger before entering a stabilizer tower. There is a control valve in the feed line where pressure is letdown from separator pressure (20 bar) to stabilizer pressure (8 bar). Should the control valve...