CALCULATIONS
1. A horizontal deaerator has been in-service for approximately 10 years. An onstream inspection shows that the vessel shell thickness is .275" (uniform) and that the heads have both pitted, reducing the thickness at the crown radius to .300. The MDR for this vessel reflects that the shell is made from SA 414 GR E plate with Type #2 longitudinal joints in all three courses, with an I.D. of 66". The heads are made from SA 285 GR C material, and are full hemispherical, with weld seams (Type 1) with an I.D. of 66" The nameplate stamping shows that the original MAWP is 280 psig @ 650°F, and complies with the rules for spot radiography (RT-3) with no static head considered, can this vessel be allowed to continue to operate at this pressure and temperature? If it should be reduced, what is the MAWP that can safely be applied to this vessel? (shell S = 16,200, Head S = 13,800)
a. No - allowable pressure should be reduced to approximately 212 psig.
b. No - allowable pressure should be reduced to approximately 107 psig.
c. Yes - vessel is acceptable for operation at 280 psig.
d. Yes - vessel is acceptable for operation at 280 psig, if impact tests are conducted.
2. A tubular heat exchanger is constructed with a flat, unstayed, seamless circular head, welded to the shell with inside and outside fillet welds as shown in Fig. UG-34, Sketch (F) (C=.20) The measured thickness of the head is 1", and is corroding approximately 1/32" (uniform) every year. The thickness of the shell has not corroded, and an onstream inspection shows the shell to be .375" thick. There are Type #1 joints in the shell, with full RT, and a vessel I.D. of 30". The fillet welds are in good condition, and are measured at .375" on both the inside and outside welds. The diameter of the head is 30", and the vessel is stamped for an MAWP of 90 psig @ 500°F. The head is constructed of SA-516 GR 70 material, and the shell is constructed of SA 285 GR C material. Assuming that the corrosion rate of 1/32" per year will continue, how many more years may this vessel be allowed to operate within the principles of the ASME Code? (head S = 17,500)
a. 1.96 years
b. 3.42 years
c. 9.62 years
d. 1.21 years
3. A new pressure vessel has been received from a manufacturer with the following information made available to the Inspector about the shell:
MAWP 500 psig @ 780°F MDMT 10°F 200 psig Spot RT, 60" I.D.
Hydro pressure 750 psig @ 70°F (material stress is 18,100 psi @ 70ºF)
Material: SA 387 GR 21, CL 1 Thickness: .350" (P# 5 material, Stress = 14,000) Type 1 Category A welds
Vertical height: 140 feet No impact tests performed No heat treatment performed Material not normalized
From the above given information, how many individual Code violations can you, as the Inspector, find as reason for not accepting this replacement part?
a. No violations - This part meets all Code requirements.
b. 3 Code violations c. 5 Code violations d. 10 Code violations
4. A fractionating tower is 14' I.D. X 21' long, bend line to bend line, and is fitted with fractionating trays.
The tower is designed for an external design pressure of 15 psig @ 700°F. The tower is constructed of SA-285 GR C carbon steel, yield strength 30,000 psi, and the design length is 39" between the fractionating trays, which are adding support to the vessel. Does this construction comply with ASME VIII requirements (assuming a designed thickness of ½")?
a. Yes, meets Code requirements
b. No - does not meet Code - pressure should be increased to 30 psig c. No - does not meet Code - pressure should be decreased to 10 psig d. No - does not meet Code - thickness should be increased to 3.6”
5. An ASME-stamped pressure vessel has been altered and now requires a hydrostatic pressure test to be applied. The vessel is 175' tall and has a pressure gauge at the top of the vessel and another gauge 25' up from the bottom of the vessel for the Inspector to look at. The MAWP is 125 psig. The ratio of design to material test stress = 1. What pressure should be shown on the gauge at the 25' level to meet API 510 requirements?
a. approximately 275 psig b. approximately 185 psig c. approximately 125 psig d. approximately 228 psig
6. An existing carbon steel pressure vessel is stamped for lethal vapor service, and has an elliptical 2:1 head. The head is measured at 60.25" I.D. in the corroded condition. The head, when new, was 1.375"
thick and 60" I.D. The stress value is 13,800, the MAWP is 300 psig, and the head is attached to the shell with a Type 1 Category B weld. Assuming a corrosion rate of 1/8" per year, answer the following questions:
• What are the radiography requirements for the head-to-shell joint?
• Does the head, in its corroded condition, meet ASME Code requirements?
• If the answer to B is yes, how many more years can the vessel operate within the parameters of ASME Code requirements?
a. full, yes, 4.75 years b. spot, yes, 8.95 years c. partial, no, 10.65 years d. none of the above
7. A torispherical head is connected to a seamless vessel with a single welded butt joint with backing. The seam has been welded by a single welder, and is spot radiographed per 11(a)(5)(b).
• What is the type of joint, joint category, and joint efficiency factor?
a. Type 1, Cat. D, E = .85 b. Type 2, Cat. B, E = 1.0 c. Type 3, Cat. A, E = 1.0 d. Type 2, Cat. B, E = .85
8. A 60" I.D. pressure vessel will require a fillet welded (temporary) patch plate. The patch and the shell are both SA 515-60 material (S = 15,000). The patch is .375" thick and the vessel is .622" thick with no corrosion allowance. The vessel has Type 1 Category A welds, and is stamped for RT-2, 200 psig @ 500°F, and an MDMT of -15°F. From the information given, will this repair require the use of a welding procedure that has been impact tested?
a. yes, impact tests are required on the welding procedure b. no, impact tests are not required on the welding procedure
c. yes, impact tests are required on both the base metal and welding procedure d. no, impact tests are only required on the base metal
9. A nozzle is installed in a vessel shell, as illustrated in Fig. UW-16.1(i), using two equal size fillet welds.
The minimum shell thickness is 3/4 inch and the nozzle wall is 7/16 inch minimum thickness. Using equal leg fillet welds, what is the leg dimension of the welds rounded up to the next larger 1/16 inch?
a. 7/16”
b. 3/16”
c. 9/16”
d. 11/16”
10. A vertical vessel is to be rerated to a new Maximum Allowable Working Pressure based on calculations of the vessel parts. The top of the vessel is located at an elevation of 75 feet. The following calculated values (P) have been determined by the Engineer (elevations are given to the bottom of the item being considered, (static head of water equals 0.433 psi per vertical foot):
1. top head, elevation 72.5 feet, P-351.3 psi 2. top shell section, elevation 65 feet, P - 352.6 psi 3. manway connection, elevation 50 feet, P = 360 psi 4. reducer section, elevation 30 feet, P = 372.5 psi 5. bottom head, elevation 6 feet, P = 425 psi
What is the maximum value of MAWP which can be applied to this vessel?
a. 450 psig
b. 360 psig
c. 395 psig
d. 348 psig
11. During the inspection of a horizontal pressure vessel, a torispherical head is measured and found to have the following dimensions: Thickness equals 1.25 inches. Inside diameter of skirt = 48 inches. The distance from the bottom of the head to the top of the vessel is 5 ft 6 in. The weight of water equals 0.433 psi/ft. From the vessel data report S = 15000 psi, and “RT-2” has been met. At what Maximum Allowable Working Pressure can this head be used with no corrosion allowance?
a. 490 psig
b. 390 psig
c. 416 psig
d. 426 psig
12. A lap patch is to be installed on a pressure vessel built to ASME Code, Section VIII, Div. 1 as part of a repair of the vessel. The patch is made of SA-515 Gr. 70 material (P-No. 1), 1-1/8 inch thickness without normalization. The owner’s engineer has determined the ratio of the allowable stress to the actual stress to be 1.0. The vessel nameplate lists the MDMT as 50°F with “HT” for the heat treatment, therefore, the patch will be voluntarily heat treated. Will the patch plate require impact testing?
a. yes
b. no
c. no, if welding procedure is impact tested d. none of the above
13. A pressure vessel cylindrical shell is measured and found to be 1.36 inches thickness at its thinnest point. The inside radius was measured at 28.625 inches. Plant records provide the following information:
1. The vessel has been in service for 4 years
2. The original vessel thickness was 1.4375 inches minimum
3. The allowable stress of the vessel material is 17500 psi at design temperature 4. The weld seam efficiency is 1
5. The maximum allowable working pressure is 745 psi with a static head of water equal to 5 psi
• Based on the above, how much material thickness is available as remaining corrosion allowance?
• What is the remaining life of the vessel?
a. .111”/10.61 years
b. .250”/3.6 years
c. .101”/5.31 years
d. .202”/4.1 years
14. A vessel’s cylindrical shell has corroded down to .25” in thickness. The cylinder is 40” o.d. with an unsupported length of 10’. Design temperature is 300°F, and the material yield strength is 30,000 psi.
What is the allowable external pressure allowed on this vessel?
a. 38 psi (approximately) b. 45 psi (approximately) c. 12 psi (approximately) d. 23 psi (approximately)
15. During the inspection of an existing pressure vessel you find it necessary to determine the weld seam efficiency of several joints on a vessel. The vessel nameplate shows RT-4. The joint type and degree of RT we read from ASME data reports for the vessel. What are the joint efficiencies for the following?
Type Category RT Joint Efficiency
16. A vessel cylindrical shell is measured today and found to be 1.0625” at the thinnest point. The inside radius is 24”. Plant records provide the following:
1. Vessel has been in service 64 years.
2. Original t was 1.1875” min.
3. SV = 15000 at design 4. Efficiency = .85
5. MAWP = 500 psi with a static head of water equal to 6 psi
6. Previous (last) inspection was completed 8 years ago and the wall thickness was 1.087
• Based on the above information, how much material t is available as remaining corrosion allowance?
• What is the remaining life of the vessel?
a. .065”/40.6 years
b. .0868”/29.93 years
c. .001”/32 years
d. .862”/15.6 years
17. A flat unstayed circular head with a diameter of 14” is operating at 350 psi at 500°F. The SV = 17500 with an efficiency of 1.0 the C factor = .33. Can this head continue in service in its present state or would a repair be necessary, if the present thicknesses is 1.25”?
a. no, head must be replaced b. no, head must be repaired c. yes, head can continue in service
d. no, head thickness must be 2.5” to be acceptable
18. A vessel owner is to repair a pressure vessel by replacing one of the vessels seamless ellipsoidal heads with a duplicate head, but welded to the shell. The original vessel name plate is stamped “W”
“RT-2” and “HT”.
• What type or types welded joints may be used in the repair?
• What Radiographic Testing of the joint is required?
a. Type 1/full RT
b. Type 2/spot RT
c. Type 3/full RT d. Type 1 or 2/spot RT
19. A vertical pressure vessel in water service with Type 1 Category "A" long seam welds is 10' seam/seam, is made from 1/2" thick SA516 GR70 material (S = 17,500), is stamped for an MAWP of 100 psig @ 650°F, and is also stamped as "RT-3" (satisfies spot radiography rules) with an I.D. of 60".
What is the actual minimum thickness of this vessel, including hydrostatic head.
a. .211”
b. .250”
c. .350”
d. .360”
20. The heads on the vessel in #19 are 2:1 elliptical heads, are seamless, and are made from the same material, same diameter, same thickness, and are welded to the vessel with Category "B" Type 1 circumferential welds. What is the minimum thickness of the bottom head if the extra radiograph required by UW-11(a)(5)(b) is taken on each head-to-shell weld? (Remember static head)
a. .250”
b. .200”
c. .179”
d. .105”
21. Assuming the same parameters for the above pressure vessel in # 19, but the heads are seamless hemispherical heads with a 30" spherical radius attached with a Category "A" Type 1 full penetration weld, what is the minimum thickness of the bottomhead?
a. .250
b. .220”
c. .179
d. .105”
22. An 8 feet I.D. horizontal pressure vessel with Type 1 weld joints is constructed totally of SA285 GR C (S = 12,100) plate with two courses (one circumferential seam joining two cylinders.) The original thickness is .375" uncorroded (new and cold) and the vessel is stamped for full radiography (RT-1). The MAWP is 50 psig @ 750° F. The heads are torispherical, 6% knuckle, 96.75" O.D. skirt, and were .375" thick also when new. An onstream inspection shows the vessel has corroded evenly over the head and shell with a uniform 1/4" external corrosion. What MAWP can this vessel be operated at, assuming no static head?
a. 25 psig (S = 17,500)? Attachment is as shown in Fig. UG-34(A), and the inside corner radius is not less than three times the required head thickness.
a. 1.1”
b. 1.9”
c. 2.3”
d. 1.66”
24. Given the parameters of the above flat head in #23, assume the head is not circular but elliptical with the same short span and a long span of 36". What is the required thickness of this head? (NOTE: This question is not supposed to be in the test, but a similar question has been asked previously.)
a. 1.9”
b. 1.5”
c. 2.1”
d. 1.66”