Api rp 521 pdf free download

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Droplets of smaller size would behave similar to combustion of gas. Droplets of larger size can result in incomplete combustion with excessive smoking, possible burning rain, and even flame-out.

Because some types of flares can accommodate larger droplets of combustible liquids, the vendor should always be consulted regarding the adequacy of a specific flare in burning liquids. The noise level sound power level expressed by Equation 58 is for either the noise due to flow across the pressure relief valve or the noise generated by flow across the discharge pipe outlet wherever the final discharge point is to atmosphere.

Can I extrapolate Figure 23? The noise calculations presented in Figure 23 are for noise generated during critical flow, and is not intended for use when the flow is not choked, nor should it be extrapolated beyond the values presented. As the pressure ratio is defined as the absolute static pressure upstream from the restriction e. Yes, provided all of the criteria in B. One of the four criteria to be satisfied is that no means can exist for blocking any of the equipment components being protected from the installation of the single pressure relief device unless closure of these valves is positively controlled as described in API Recommended Practice , Part II, Section 2.

Question: Can we provide locked open or car-sealed open valves in the interconnecting piping between the equipment components protected by a single relief device? Others are interpreting that B. Appendix B offers an example of a single relief valve protecting several equipment components. Section B. It does not unconditionally provide guidance on the relief device set point. RP , Section B. The relief valve is usually set at design pressure but consideration should be given to proper blowdown.

No, API does not have any minimum volume requirements as to when to exclude an overpressure scenario. If the fire scenario is considered for a shell and tube heat exchanger full of liquid should we size the safety valve based on single or two phase equations? As stated in API Std. We dont know if a heat exchanger shell with some baffles and tubes inside could be interpreted as a narrow passage according to API paragraph above.

It is up to the user to determine whether the internals within the shell-and-tube heat exchanger would result in two phase relief in a fire. References cited in Section 5. Now when applying this rule we discovered a significant difference in the result depending on the selection of the units, either SI or USC. The root cause of the difference appears to be in the constants C1 and C1, which have a different dimension when the exponent applied to the " total wetted surface" is changed from 0.

Applying the same constants C1 and C2 would result in a significant difference in the calculated Total heat absorption depending on the selected units. You have noted correctly that the equations were originally derived in USC units.

When applying Equations 6 and 7 in section 5. When applying these equations in USC units, the correct values of C1 and C2 are and , respectively.

An Addendum was issued noting this correction along with several unrelated additions to the J anuary 5th edition. Question 2: If it is not practical to locate air coolers away from equipment containing flammable equipment, are there any qualifications that could help us eliminate the need for providing a deluge system?

Reply 1: Yes, however, 5. A deluge system is one option to mitigate the potential consequences. It is up to the user to evaluate the risks involved in a particular application. The alternatives listed in Section 5. Reply 2: See Reply 1. Pressure relief for transient effects of tube rupture is not required where the corrected hydrotest pressure of the low pressure side including upstream and downstream equipment is equal to or greater than the design pressure of the high pressure side of the exchanger.

See 4. The statement implies to only consider a tube break at the tubesheet i. This would not be the most appropriate location for relief if a tube were to break at the opposite end of the exchanger. Is this purely for the determination of the relief rate? The Section 5. Section 5. The statement appears to only consider a tube break at the tubesheet, i. However, this would not be the most appropriate location for relief if a tube were to break at the opposite end of the exchanger.

No, this statement is for determination of the relief capacity only. What should be the reference and limit for design? The air requirements to achieve smokeless combustion can vary between manufacturers and between types of flare tips. The kPa psi air supply pressure is a typical value although the manufacturer for the specific flare tip and service should be consulted to determine the appropriate air supply conditions for their tip.

The calculation check for Mach number is for the pressure discontinuity that results from critical flow though a piping section or piping component, and the effect of this on the overall disposal system pressure drop.

API , 5th Edition, does not currently provide specific recommendations for maximum velocities for tail pipes and flare headers, although many companies have such standards.

This topic will be considered for the next edition of the standard. An errata was issued and this was corrected in the Amendment 5th - J an 7. Description under the equation says L is from Figure The description and the title under Figure 18 on page say this figure to be for L rather than L. After circulation reference equation 67 becomes useless. Question 2. Does the downstream pressure mean atmosphere pressure or the pressure immediate downstream of the nozzle atmosphere pressure plus PSV outlet pressure drop.

Question 3. In the examples in Sections 7. Can you give me detail descriptions of what 48 and 16 exactly stand for and what units they are?

Because the units are different in the two sections, at least the numbers should be different, even though the ratio may be the same. Response to question 1: Figure 18 has an error. The downstream, pressure should be atmospheric pressure when venting to atmosphere while the backpressure at the pressure-relief valve should be used when discharging to flare. Response to question 3: The original equation was based on an example involving a relieving pressure of 48 psia and a downstream of 16 psia, instead of bar pressure.

Units are in absolute pressure and they cancel out in the example given. An errata pertaining to the J anuary 5th edition was issued on J une 21, and is available on the API website.

Yes 5th, Addendum - April 5. Table 5 gives a guideline on the inventory of liquid at the column bottom but nothing mentioned about the composition of the liquid, considering the fact that the inventory is a homogenous mixture of column bottom liquid plus hold up liquid of all the trays. Question: What would the resultant composition of liquid at the fractionating column bottom be during an external fire?

It is up to the User to determine the composition based on the specific fire scenario and equipment configuration. Clarify why a higher " C factor" needs to be used where adequate drainage and firefighting equipment do not exist. The effect of drainage and firefighting in reducing the heat input to equipment from a pool fire was determined by tests.

Appendix A, Table A1, Tests 1 and 2 are the basis. This is inconsistent with the same equation in API which is defined to be taken as an ideal gas at relieving temperature. Which is correct? The specific heat ratio, k, should be taken as an ideal gas atmospheric pressure but at relieving temperature. Should the relief valves be sized for the two phase relief of the hydrocarbon foam entrained with water vapor?

See API for information about API and pressure vessels used for the transportation of The members of the American Petroleum Institute are dedicated to continuous efforts to improve Get api 5th edition PDF file for free from our online library. PDF File: api This document was produced under API standardization procedures that ensure Installations at Petroleum Facilities.

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