7/29/2019 Pneumatic Test - Calculation

1/3

Draft; Rev O; 10-31-2005 For Committee Use Only

Appendix 2

Stored Energy Calculations for Pneumatic Pressure Test

The stored energy of the equipment or piping system should be calculated and converted toequivalent kilograms (pounds) of TNT (Trinitrotoluene) using the following equations:

E =[1/(k-1)]x Pat x V [1 (Pa/Pat)[(k-1)/k]] (2-1)

Where E is the stored energy, J oules (ft-lbs)Pat is the absolute test pressure Pa (psia)Pa is absolute atmospheric pressure, 101 kPa (14.7 psia)V is the total volume under test pressure, M3 (ft3)k is the ratio of specific heat for the test fluid

When using air or nitrogen as the test medium (k = 1.4), this equation becomes

E = 2.5 x Pat x V [1 (Pa/Pat)0.286] (2-2)

andTNT = E (kg) (2-3)

4266920

where E is the stored energy, J oulesPat is the absolute test pressure PaPa is absolute atmospheric pressure, 101000 Pa

V is the total volume under test pressure, M3

For US customary units using air or nitrogen as the test medium (k = 1.4), thisequation becomes

E = 360 x P at x V [1 (Pa/Pat)0.286] (2-4)

and

TNT = E (lbs) (2-5)1488617

Where E is the stored energy, ft-lbsPat is the absolute test pressure psiaPa is absolute atmospheric pressure, 14.7 psiaV is the total volume under test pressure, ft3

See also Section 6.2.5 and 6.2.6.

Page 18

7/29/2019 Pneumatic Test - Calculation

2/3

Draft; Rev O; 10-31-2005 For Committee Use Only

Appendix 3

Safe Distance Calculations for Pneumatic Pressure Test

The minimum distance between all personnel and the equipment being tested shall be thegreater of

(a) R = 30 m for E < 135,500,000 JR = 60 m for for 135,500,000 J < E < 271,000,000 J

R = 100 ft for E < 100,000,000 ft-lbsR = 200 ft for 100,000,000 < E < 200,000,000 ft-lbs

(b) R = RSCALED (TNT)1/3 (3-1)

Where R = actual distance from equipment

E = stored energy as calculated by equation (2-1) or (2-2)RSCALED = scaled consequence factor; value for equation (3-1) shall be 20 m/kg

1/3(50 ft/lb1/3) or greater

TNT = Energy measured in TNT, kg (lbs), determined from equations (2-3) or(2-5)

For systems where E > 271,000,000 J (200,000,000 ft-lbs), the required distance shall becalculated by equation (3-1).

If the minimum calculated distance cannot be obtained, an alternative value for RSCALED may bechosen based on Table 3-1 for use in equation (3-1). See also section 6.2.7.

RSCALED (m/kg1/3

) RSCALED (ft/lb1/3

) Biological Effect Structural Failure

20 50 - Glass windows

12 30 Eardrum rupture Concrete block panels

6 15 Lung damage Brick walls

2 5 Fatal -

Table 3-1

For example, to prevent lung damage, the distance a person is from the equipment shouldresult in an RSCALED value of more than 6 m/kg1/3 (15 ft/lb1/3). Note the structural damage thatcan occur, which shall be considered.

Page 19

7/29/2019 Pneumatic Test - Calculation

3/3

Draft; Rev O; 10-31-2005 For Committee Use Only

Appendix 4Risk Evaluation Considerations for Pneumatic Pressure

Test

When considering the risk analysis factors listed in Section 6.2.4, it should be remembered thatrisk is a two dimensional combination of probability (or likelihood) and consequence. Risk is themeasure of the potential for harm or loss (i.e., hazard) that reflects the likelihood (or frequency)and severity of an adverse effect to health, property, or the environment. If probability andconsequence are defined quantitatively (i.e. numerical values are assigned), risk is the product.

Risk = Probability x Consequence (4-1)

In a qualitative assessment, a matrix is typically used to combine probability and consequence.Consideration should be given to the level of risk which is acceptable when performingpneumatic tests. Reference API RP 580 for use of risk assessment in determining theacceptable levels of risk associated with pneumatic testing.

In reviewing equation (4-1), it is clear that even though the consequence may be significant, ifthe probability is very low, the risk may become acceptable. For example, the consequence ofan airliner crashing is significant in that it will most likely result in serious injury or death to thepassengers along with major damage or total loss of the aircraft. However, the probability of theairliner crashing is very low, thus, the public accepts the risk associated with airline travel.

Risk considerations can be applied to pneumatic testing also. Examples may include:

A new austenitic stainless steel piping system that has been hydrostatically tested duringshop fabrication with the exception of four (4) final field assembly circumferential buttwelds. The piping system has a total volume which results in an energy level greaterthan 271,000,000 J (200,000,000 ft-lbs); however, it is not feasible to separate the pipingsystem into smaller sections for testing, nor is it feasible to install blast barriers. Byperforming volumetric examination such as UT or RT and determining the field welds arefree of rejectable indications, the risk associated with a full pneumatic pressure test ofthis system may be deemed acceptable.

An existing carbon steel vessel with an MDMT rating of -45 C (-50 F) into which a newnozzle had been installed following all requirements of the original Code of Construction.

The vessel has a total volume which results in an energy level greater than 271,000,000J (200,000,000 ft-lbs); however, it is still desired to perform a pressure test to check theintegrity of the weld and obtain the other benefits of pressure testing. It is not feasible toinstall blast barriers. By performing volumetric examination such as UT on the nozzleattachment weld and determining the weld is free of rejectable indications, along withverification by inspection that the vessel is in a like-new condition, the risk associatedwith a full pneumatic pressure test of this vessel may be deemed acceptable.

Page 20