6 replies to this topic

[Lethal83]

I have been asked by a client to define what is a safe area to vent a PSV or a burst disc to.

Does anyone know if this is defined anywhere or if there is any guidelines.

I have looked through the API stds but done see any definition.

To me a safe area is an area where no personnel will be present or put at risk. Could anyone elaborate further?

[breizh]

You will probably need a dispersion model to evaluate the risk associated with the release of chemicals through a PSV or Bursting disk for the staff and neighborhood .
Probably required by local EPA as well.

Breizh

[kkala]

Probably http://www.asiaiga.o...ormat Apr11.pdf '> http://www.asiaiga.o...ormat Apr11.pdf could be also helpful, even though limited to oxygen and inert gases. It complies with post No 2 by Breizh.
Clarification on what substance is vented from PSV (steam, hydrocarbon gas, etc) would result in more specific answers.

[ankur2061]

Lethal83,

A safe area or safe level from a pressure relief device is directly a function of the material that is being relieved from the relief device and its proximity to working personnel.

By material it is meant whether the material that is being reilived is toxic, flammable or a source of heat radiation. Proximity of working personnel means the minimum distance from the relief discharge where a person might be required to work and thus is being exposed to the materialdischarged from the relief device.

As Breizh mentioned if you are dealing with toxic, flammable or heat radiant discharges then a dispersion analysis needs to be done to ascertain what is the safe area or height of the discharge.

If you are discharging something harmless such as air from the relief device a rule-of-thumb is to have a height of 3 m from the discharge comnection which is based on the fact that a person's height is generally less than 3 m.

Hope this helps.

Regards,
Ankur.

[Zubair Exclaim]

i remeber we did some thing similar for BP :

we did to analysis
1-radiation zone analysis
2-dispersion zone analysis

then we set out the lethal/harm ful ranges separately for both cases and based on contours of these analysis specified relevent area

but most companies dont bother all that hustle and may adopt diff approach

Edited by Exclamation, 17 April 2012 - 05:00 AM.

[Robert Montoya]

I have been asked by a client to define what is a safe area to vent a PSV or a burst disc to.

Does anyone know if this is defined anywhere or if there is any guidelines.

I have looked through the API stds but done see any definition.

To me a safe area is an area where no personnel will be present or put at risk. Could anyone elaborate further?

Dear Lethal83; depend of what kind of vent that you are using. In the case of vapors of hydrocarbons, they are for vent is determinate using of dispersion model usually the hydrocarbon that you can vent are such the MW are lower of the MW of the air. In case of dust, you can use NFPA 68 and EN 14491.

[kkala]

Another factor to be considered is noise during discharge, which should comply with local regulations.
For Greece, noise at distance of 1 m from equipment, or from pipe of continuous flow, should be 85 dB abs, or lower.
Discharge from vents and safety valves (like the present case) should result in no more than 95 dB abs on any place or platform where people may be during operation. Downstream silencers should be installed, if necessary.

(From a duty spec of a local refinery boiler, recently ordered).

Edited by kkala, 16 April 2012 - 04:32 AM.