API 510 Preparatory ClassAPI 510 Preparatory Class

Lesson 5Lesson 5

Hydrostatic, Pneumatic TestsHydrostatic, Pneumatic Tests

(a) A hydrostatic test shall be conducted on all vessels after:

(1) all fabrication has been completed, except for operations which could not be performed prior to the test such as weld end preparation….

(2) all examinations have been performed, except those required after the test…...

UG-99 Standard Hydrostatic Test Page 80 Section VIII

(b) Except as otherwise permitted in (a) above and 27-3, vessels designed for internal pressure shall be subjected to a hydrostatic test pressure which at every point in the vessel is at least equal to 1.3 times the maximum allowable working pressure to be marked on the vessel multiplied by the lowest ratio (for the materials of which the vessel is constructed) of the stress value S for the test temperature on the vessel to the stress value S for the design temperature…

Stress at Test TempStress at Design Temp

UG-99 Standard Hydrostatic Test

(c) A hydrostatic test based on a calculated pressure may be used by agreement between the user and the manufacturer….. A New and Cold Test relates to a statement in API 510.

(d) The requirements of (b) above represent the minimum standard hydrostatic test pressure required by this Division……

UG-99 Standard Hydrostatic Test

(g) Following the application of the hydrostatic test pressure, an inspection shall be made of all joints and connections. This inspection shall be made at a pressure not less than the test pressure divided by 1.3. Except for leakage that might occur at temporary test closures for those openings intended for welded connections, leakage is not allowed at the time of the required visual inspection………..

UG-99 Standard Hydrostatic Test

The visual inspection of joints and connections for leaks at the test pressure divided by 1.3 may be waived provided:

(1) a suitable gas leak test is applied;(2) substitution of the gas leak test is by agreement

reached between Manufacturer and Inspector;(3) all welded seams which will be hidden by assembly be given a visual examination for workmanship prior to assembly;(4) the vessel will not contain a “lethal” substance.

UG-99 Standard Hydrostatic Test

(h) Any non-hazardous liquid at any temperature may be used for the hydrostatic test if below its boiling point. Combustible liquids having a flash point less than 110°F, such as petroleum distillates, may be used…..

It is recommended that the metal temperature during hydrostatic test be maintained at least 30°F above the minimum design metal temperature, but need not exceed 120°F, to minimize the risk of brittle fracture.

API 510 has a different rule for this, it recommends that the temperature be 10°F above for 2” (50mm) thickness and under and 30°F above for over 2 inches (50mm) .

UG-99 Standard Hydrostatic Test

Footnote Caution: A small liquid relief valve set to 1-1/3 times the test pressure is recommended for the pressure test system, in case a vessel, while under test, is likely to be warmed up materially with personnel absent.

(i) Vents shall be provided at all high points of the vessel in the position in which it is to be tested to purge possible air pockets…….

(j) Before applying pressure, the test equipment shall be examined to see that it is tight and that all low pressure filling lines and other appurtenances………

UG-99 Standard Hydrostatic Test

(k) Vessels, except for those in lethal service, may be painted or otherwise coated either internally or externally, and may be lined internally, prior to the pressure test. However, the user is cautioned that such painting / coating / lining may mask leaks that would otherwise have been detected during the pressure test.

UG-99 Standard Hydrostatic Test

1. If the test is required it shall be conducted after welded repairs.

2. The test pressure must at least be1.3 times the MAWP or whatever the original design Code specified i.e. 1.5.3. The test pressure shall be adjusted for lowest ratio of stresses.4. Any non-hazardous fluid may be used if below its boiling point.5. It is recommended that the metal temperature during hydro test be maintained at least 10 °F above MDMT for vessels 2” (51mm) and less and 30 °F above for vessels over 2” (51mm) to minimize the risk of brittle fracture.6. Following the application of hydro pressure a visual inspection shall be performed at no less than the test pressure divided by 1.3 or whatever was originally used.

API 510 Hydrostatic Test Procedure

Problem: Calculate the required hydro test pressure for a vessel using the following conditions:

Material Carbon SteelDesign Temp. 700 °FTest Temp 85 °FMAWP 350 psi

Step 1 Determine the ratio of stresses for the test and design temperatures.

(a) From Table 1A Section II Part D.  Stress allowed at 700 °F = 15,500 psi

Stress allowed at 85 °F = 16,300 psi

UG-99 Standard Hydrostatic

(b) Per UG-99 the ratio equals

UG-99 Standard Hydrostatic

05.1 500,15

300,16

(c) Per UG-99 the ratio equals

Step 2 UG-99(b) Test pressure equals 1.3 x MAWP x ratio

1.3 x 350 psi x 1.05 = 477.75 psi at the top of the vessel.

Temp. Design at StressTemp. Test at Stress

Look at the reference next to UG-100 (See UW-50)

This is what is referred to as a parenthetical reference in the ASME Codes. You must read these to see what modifiers the Code has placed on subject paragraph.

On welded pressure vessels to be pneumatically tested in accordance with UG-100, the full length of the following welds shall be examined for the purpose of detecting cracks:

(a) all welds around openings;(b) all attachment welds, including welds attaching nonpressure parts to pressure parts, having a throat thickness greater than 1/4 in….

UW-50 NDE of Welds for Pneumatically Tested Vessels

(a) Subject to the provisions of UG-99(a)(1) and (a)(2), a pneumatic test prescribed in this paragraph may be used in lieu of the standard hydrostatic test prescribed in UG-99 for vessels:

(1) that are so designed and/or supported that theycannot safely be filled with water;

(2) not readily dried, that are to be used in serviceswhere traces of the testing liquid cannot be tolerated

and the parts of which have, where possible, been previously tested by hydrostatic pressure to the pressure required in UG-99.

UG-100 Standard Pneumatic Page 81 Section VIII

(b) Except for enameled vessels, for which the pneumatic test pressure shall be at least equal to, but need not exceed, the maximum allowable working pressure to be marked on the vessel, the pneumatic test pressure shall be at least equal to 1.1 times the maximum allowable working pressure to be stamped on the vessel multiplied by the lowest ratio of the stress value S for the test temperature of the vessel to the stress value S for the design temperature. In no case shall the pneumatic test pressure exceed 1.1 times……

So we have:

UG-100 Standard Pneumatic

Stress at Test Stress at Design

(c) The metal temperature during pneumatic test shall be maintained at least 30°F (17°C) above the minimum design metal temperature to minimize brittle fracture risk. [See UG-20 and General Note (6) to Fig. UCS-66.2.]

* API 510 states as a minimum Pneumatic tests shall meet all the safety requirements of ASME Section VIII.

(d) The pressure in the vessel shall be gradually increased to not more than one-half of the test pressure. The test pressure shall be increased in steps of approximately one-tenth of the test pressure until the required test pressure has been reached. Pressure shall be reduced to a value equal to the test pressure divided by 1.1 and held fora sufficient time to permit inspection of the vessel………….

UG-100 Standard Pneumatic

1. If the test is required it shall be conducted after welded repairs.

2. The welded repairs shall be subjected to the tests required by UW-50.3. The test pressure must at least be 1.1 times the MAWP or whatever the original design Code specified i.e.1.25.4. Test pressure is adjusted for lowest ratio of stresses.5. Metal must be maintained at least 30 °F over MDMT.6. The test pressure shall be raised at a gradual rate to not

more than 1/2 the test pressure and then raised by 1/10th of the test pressure until the test is reached.7. Visual inspection must be made at test pressure divided

by 1.1 or whatever was originally used.. The visual may be waived if the requirements in UG-100 are met.

UG-100 Standard Pneumatic Tests

Problem: Calculate the required pneumatic test pressure for a vessel using the following conditions.

Material Carbon SteelDesign Temp. 700 o FTest Temp 85 o FMAWP 350 psi

Step 1: Determine the ratio of stresses for the test and design temperatures.

 (a) From Table 1A Section II Part D.  Stress allowed at 700 o F= 15,500 psi

Stress allowed at 85 o F= 16,300 psi

UG-100 Calculating Pneumatic Test Pressure

(b) Per UG-100 the ratio equals

UG-100 Calculating Pneumatic Test Pressure

Temp. Design at StressTemp. Test at Stress

05.1 500,15

300,16

Step 2 Per UG-100(b) Test pressure equals 

1.1 x MAWP x

1.1 x 350 psi x 1.05 = 404.25 psi 

Temp. Design at StressTemp. Test at Stress

1. Slowly raise the pressure to approximately one-half 404.25 psi which equals 202.125. Next raise the pressure in steps of one-tenth of the test pressure.

2. 202.125 + 40.425 = 242.55 psi3. 242.55 + 40.425= 282.975 psi4. 282.975 + 40.425 = 323.40 psi5. 323.40 + 40.425 = 363.825 psi6. 363.825 + 40.425 = 404.25 psi

There are a total of 6 steps when raising up to pneumatic test pressure. Finally lower to the inspection pressure of404.25/1.1 = 367.5 psi

Pneumatic Test Procedure

The Code has some definite requirements for the selection and uses of gages for the tests described in UG-99 and UG-100. Directions for location, number of, range of and the calibration of the indicating gage(s) is located in UG-102. The high points of UG-102 are below.

1. An indicating gage shall be connected directly to the vessel. If it is not readily visible to the operator of the test equipment an additional gage shall be used which is visible....

2. When doing large vessel pressure tests it is recommended to have a recording gage in addition to the indicating gage.

UG-102 Test Gauges Overview

3. Dial type indicating gages shall have a range of about double the maximum test pressure, but in no case shall the range of the gage be less than 1 1/2 times nor more than 4 times the maximum test pressure.

4. Digital gages having a wider range may be used as long as they provide the same or greater accuracy of the dial type.

5. All gages shall be calibrated against a standard deadweight tester or a calibrated master gage.

6. Gages must be calibrated any time their accuracy is in doubt.

UG-102 Test Gages Overview

Class Quizzes UG-99/UG-100/102

1. A vessel made of Stainless Steel is being hydrostatically tested after an alteration. The vessel's MAWP is 225 psi at 400 o F. The allowable stress at operating is 14,700 psi and 16,700 psi at the test temperature.

Answer the following:

a. What is the required test pressure?b. What is the least pressure for the inspection?c. In psi, what is the min. and max. range of the test gage?

Class Quizzes UG-99/UG-100/102

2. A pneumatic test of a vessel will be conducted to a pressure of 310 psi. Describe the steps for raising the vessel to the test pressure. At what pressure shall the visual examination take place?

1. Hydrostatic Test

a.

b.

c. Min. gage range 1.5 x 332.295 = 498.4 ( 500 psi )Max. gage range 4 x 332.295 = 1329.18 ( 1000

psi ) the gage pressure at the 4X range would be rounded down to closest standard range!

Solutions

psixx 295.332700,14

700,162253.1

psi61.2553.1

295.332

2. Pneumatic Test

Step 1 Raise the pressure to ½ the test pressure, ½ x 310 psi = 155 psi, then raise in steps of 1/10 to full

test pressure.

Step 2 155+31=186 psiStep 3 186+31=217 psiStep 4 217+31=248 psiStep 5 248+31=279 psiStep 6 279+31=310 psi

The inspection pressure is 310/1.1 = 281.8 psi for visual inspection.

Solutions

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