ASME Code Case 181

ASME Code Case on Use of Alternative

Ultrasonic Examination Acceptance

Criteria in ASME B31.3

Charlie Chong

Charlie Chong

Process Piping

Charlie Chong/ Fion Zhang

NOTICE REGARDING CODE CASES OF

THE ASME B31 CODE FOR PRESSURE PIPING

All B31 Code Cases in effect as of September 21, 2007 will remain available

for use unless annulled by the B31 Standards Committee

Fion Zhang/ Charlie Chong

Charlie Chong

B31 CASE 181-1

CASES OF THE CODE FOR PRESSURE PIPING

– B31 Approval Date: January 23, 2007

B31 Case 181-1

Use of Alternative Ultrasonic Examination acceptance Criteria in ASME B31.3

Inquiry: Under what conditions and limitations may alternative UT acceptance

criteria apply in lieu of those described in para. 344.6.2 of ASME B31.3.

Reply: It is the opinion of the Committee that alternative UT acceptance

criteria as described in this case may be applied in lieu of those described in

para. 344.6.2 of ASME B31.3 provided that all of the following requirements

are met:

Charlie Chong

ASME B31.3

344.6 Ultrasonic Examination

344.6.1 Method. Examination of castings is covered in para. 302.3.3; other

product forms are not covered. Ultrasonic examination of welds shall be

performed in accordance with BPV Code, Section V, Article 4, except that the

alternative specified in (a) and (b) below is permitted for basic calibration

blocks specified in T-434.2.1 and T-434.3.

(a) When the basic calibration blocks have not received heat treatment in

accordance with T-434.1.5, transfer methods shall be used to correlate the

responses from the basic calibration block and the component. Transfer is

accomplished by noting the difference between responses received from the

same reference reflector in the basic calibration block and in the component

and correcting for the difference

Charlie Chong

(b) The reference reflector may be a V-notch (which must subsequently be

removed), an angle beam search unit acting as a reflector, or any other

reflector that will aid in accomplishing the transfer.

(c) When the transfer method is chosen as an alternative, it shall be used, at

the minimum

1)for sizes ≤ DN 50 (NPS 2), once in each 10 welded joints examined

2)for sizes > DN 50 and ≤ DN 450 (NPS 18), once in each 1.5 m (5 ft) of

welding examined

3)for sizes > DN 450, once for each welded joint examined

(d) Each type of material and each size and wall thickness shall be

considered separately in applying the transfer method. In addition, the

transfer method shall be used at least twice on each type of weld joint.

(e) The reference level for monitoring discontinuities shall be modified to

reflect the transfer correction when the transfer method is used.

Charlie Chong

344.6.2 Acceptance Criteria. A linear-type discontinuity is unacceptable if

the amplitude of the indication exceeds the reference level and its length

exceeds

(a) 6 mm (1⁄4 in.) for T w ≤ 19 mm (3/4 in.)

(b) T w 3 for 19 mm < T w ≤ 57 mm (2 1/4 in.)

(c) 19 mm for T w > 57 mm

Keywords:

linear-type discontinuity

Charlie Chong

(a) The ultrasonic examination area shall include the volume of the weld,

plus the lesser of 25 mm (1in) or t on each side of the weld

(b) A documented examination strategy or scan plan shall be provided

showing transducer placement, movement, and component coverage that

provides a standardized and repeatable methodology for weld

acceptance. The scan plan shall also include ultrasonic beam angle

used, beam directions with respect to weld centerline, and pipe volume

examined for each weld. The documentation shall e made available to

the owner’s Inspector.

Key point:

A documented examination strategy or scan plan

plus the lesser of 25 mm (1 in)

or t on each side of the weld

Charlie Chong

(c) The ultrasonic examination shall be performed in accordance with a

written procedure conforming to the requirements of Section V, Article 4. 1

The procedure shall have been demonstrated to perform acceptably on a

qualification block(s). Qualification block(s) shall be in accordance with

section V, Article 4, T-434.1.2 through T-434.1.6. The qualification block(s)

shall be prepared by welding or the hot isostatic process (HIP) and shall

contain a minimum of three flaws, oriented to simulate flaws parallel to the

production weld's fusion line as follows:

1) one surface flaw on the side of the block representing the pipe OD

surface

2) one surface flaw on the side of the block representing the pipe ID

surface

3) one subsurface flaw

4) If the block can be flipped during UT examination, then one flaw may

represent both the ID and OD surfaces. Thus only two flaws may be

required.

Charlie Chong

1

Sectorial scans (S-scans) with phased arrays may be used for the

examination of welds, provided they are demonstrated satisfactorily in

accordance with para. (c). S-scans provide a fan beam from a single emission

point, which covers part or all of the weld, depending on transducer size, joint

geometry, and section thickness. While S-scans can demonstrate good

detectability from side drilled holes, because they are omnidirectional

reflectors, the beams can be misoriented for planar reflectors (e.g., lack of

fusion and cracks). This is particularly true for thicker sections, and it is

recommended that multiple linear passes with S-scans be utilized for

components greater than 25 mm (1 in.) thick. An adequate number of flaws

should be used in the demonstration block to ensure detectability for the

entire weld volume.

Keywords:

An adequate number of flaws should be used in the demonstration block to

ensure detectability for the entire weld volume.

Charlie Chong

Charlie Chong

The qualification block(s) shall be prepared by welding or the hot isostatic

process (HIP) and shall contain a minimum of three flaws, oriented to

simulate flaws parallel to the production weld's fusion line as follows:

Charlie Chong

ARTICLE 4

ULTRASONIC EXAMINATION METHODS FOR WELDS

T-434 CALIBRATION BLOCKS

T-434.1 General.

T-434.1.1 Reflectors. Specified reflectors (i.e., sidedrilled holes, flat bottom

holes, notches, etc.) shall be used to establish primary reference responses

of the equipment. An alternative reflector(s) may be used provided that the

alternative reflector(s) produces a sensitivity equal to or greater than the

specified reflector(s) (e.g., side-drilled holes in lieu of notches, flat bottom

holes in lieu of side-drilled holes).

.

T-434.1.2 Material.

(a) Similar Metal Welds. The material from which the block is fabricated shall

be of the same product form and material specification or equivalent P-

number grouping as one of the materials being examined. For the purposes

of this paragraph, P-Nos. 1, 3, 4, 5A through 5C, and 15A through 15F

materials are considered equivalent.

(b) Dissimilar Metal Welds. The material selection shall be based on the

material on the side of the weld from which the examination will be

conducted. If the examination will be conducted from both sides, calibration

reflectors shall be provided in both materials. T-434.1.3 Quality. Prior to

fabrication, the block material shall be completely examined with a straight

beam search unit. Areas that contain an indication exceeding the remaining

back-wall reflection shall be excluded from the beam paths required to reach

the various calibration reflectors.

Charlie Chong

Charlie Chong

T-434.1.3 Quality. Prior to fabrication, the block material shall be completely

examined with a straight beam search unit. Areas that contain an indication

exceeding the remaining back-wall reflection shall be excluded from the beam

paths required to reach the various calibration reflectors.

Flaw size shall be no larger than the flaw in Table 1 or 2 for the thickness to

be examined.

Acceptable performance is defined as response from the maximum allowable

flaw and other flaws of interest demonstrated to exceed the reference level.

Alternatively, for techniques that do not use amplitude recording levels,

acceptable performance is defined as demonstrating that all imaged flaws

with recorded lengths, including the maximum allowable flaws, have an

indicated length equal to or greater than the actual length of the flaws in the

qualification block.

TABLE 1

FLAW ACCEPTANCE CRITERIA FOR WELD

THICKNESS LESS THAN 25 mm (1 in.)

Charlie Chong

Charlie Chong

TABLE 1

FLAW ACCEPTANCE CRITERIA FOR WELD

THICKNESS LESS THAN 25 mm (1 in.)

Charlie Chong

GENERAL NOTES:

(a)t = the thickness of the weld excluding any allowable reinforcement. For a

butt weld joining two members having different thickness at the weld, t is the

thinner of these two thicknesses. If a full penetration weld includes a fillet

weld, the thickness of the throat of the fillet weld shall be included in t.

(b) A subsurface indication shall be considered as a surface flaw if the

separation (S in Fig. 1) of the indication from the nearest surface of the

component is equal to or less than half the through dimension (2d in Fig. 1,

sketch [b]) of the subsurface indication.

Charlie Chong

A subsurface indication shall be considered as a surface flaw if the separation

(S in Fig. 1) of the indication from the nearest surface of the component is

equal to or less than half the through dimension (2d in Fig. 1, sketch [b] ) of

the subsurface indication

Charlie Chong

TABLE 2

FLAW ACCEPTANCE CRITERIA FOR 25 mm (1 in)

TO 300 mm (12 in.) THICK WELD

Charlie Chong

GENERAL NOTES:

(a)t = thickness of the weld excluding any allowable reinforcement. For a

buttweld joining two members having different thickness at the weld, t is the

thinner of these two thicknesses. If a full penetration weld includes a fillet

weld, the thickness of the throat t of the fillet weld shall be included

in t.

(b)A subsurface indication shall be considered as a surface flaw if separation

(S in Fig. 1) of the indication from the nearest surface of the component is

equal to or less than half the through thickness dimension (2d in Fig. 1,

sketch [b]) of the subsurface indication.

(c)If the acceptance Criteria in this table results in a flaw length, l , less than

6.4 mm (0.25 in.) , a value of 6.4 mm (0.25 in.) may be used.

(d)for intermediate flaw aspect ratio a/l and thickness t (64 mm [2 1/2 in] < t <

100 mm [4 in.]) linear interpolation is permissible.

Charlie Chong

(d) The ultrasonic examination shall be performed using a device employing

automatic computer based data acquisition. The initial straight beam material

examination (T-472 of Section V, Article 4) for reflectors that could interfere

with the angle beam examination shall be performed

(1) manually,

(2) as part of a previous manufacturing process, or

(3) during the automatic UT examination provided detection of these

ref1ecctors is demonstrated as described in Para. (c)

(e) Data is recorded in unprocessed form. A complete data set with no gating,

filtering, or thresholding for response from examination volume in para. (a)

above shall be included in the data record.

(f) Personnel performing and evaluating UT examinations shall be qualified

and certified in accordance with their employer's written practice. ASNT SNT-

TC-lA or CP-189 shall be used as a guideline. Only Level II or III personnel

shall analyze the data or interpret the results.

Charlie Chong

Charlie Chong

(e) Data is recorded in unprocessed form. A complete data set with no gating,

filtering, or thresholding for response from examination volume in para. (a)

above shall be included in the data record.

(g) Qualification records of certified personnel shall be approved by the

owner’s Inspector per para. 342.1.

(h) In addition, personnel who acquire and analyze UT data shall be qualified

and certified in accordance with (f) above and shall be trained using the

equipment in (d) above, and participate in the demonstration of (c) above.

Charlie Chong

(i) Data analysis and acceptance criteria shall be as follows:

(1) Data Analysis Criteria. Reflectors exceeding the limits in either (a) or

(b) below, as applicable, shall be investigated to determine whether the

indication originates from a flaw or is a geometric indication in

accordance with para. (i) (2 ) below. When a reflector is determined to

be a flaw, it shall be evaluated for acceptance in accordance with para.

(i)(4), Flaw Evaluation and Acceptance Criteria.

(a) For amplitude-based techniques, the location, amplitude, and

extent of all reflectors that produce a response greater than 20% of

the reference level shall be investigated.

Charlie Chong

(b) For non amplitude-based techniques, the location and extent of all

images that have an indicated length greater than the limits in (1) or

(2) below, as applicable, shall be investigated.

(1) For welds in material equal to or less than 38 mm (1 ½ in.)

thick at the weld, images with indicated lengths greater than

3.8 mm (0.150 in.) shall be investigated.

(2) For welds in material greater than 38 mm (1 ½ in). thick but

less than 64 mm (2 ½ in.) thick at the weld, images with

indicated lengths greater than 5 mm (0.200 in.) shall be

investigated.

Charlie Chong

Charlie Chong

(2) Geometric. Ultrasonic indications of geometric and metallurgical origin

shall be classified as follows:

(a) Indications that are determined to originate from the surface

configurations (such as weld reinforcement or root geometry) or

variations in metallurgical structure of materials (such as cladding

to base metal interface) may be classified as geometric indications,

and

(1) need not be characterized or sized in accordance with ( i )(3)

below;

(2) need not be compared to allowable flaw acceptance criteria

of Table 1 or 2;

(3) the maximum indication amplitude and location shall be

recorded, for example: interna attachements, 200% DAC

maximum amplitude, 25 mm (1in.) above the weld centerline,

on the inside surface, from 90 to 95 deg.

Charlie Chong

(b) The following steps shall be taken to classify an indication as

geometric:

(1) Interpret the area containing the reflector in accordance with

the applicable examination procedure;

(2) Plot and verify the reflector coordinates, provide a crosssectional

display showing the reflector position and surface

discontinuity such as root or counterbore; and

(3) Review fabrication or weld prep drawings.

Charlie Chong

(c) Alternatively, other NDE methods may be applied to classify an

indication as geometric (e.g., alternative UT beam angles,

radiography,). The method employed is for information only to

classify the indication as geometric and ASME B31.3 requirements

for examination techniques are only required to the extent that they

are applicable.

(3) Flaw Sizing. Flaws shall be sized in accordance with a procedure

demonstrated to size similar flaws at similar material depths.

Alternatively, a flaw may be sized by a supplemental manual technique

so long as it has been qualified by the demonstration above. The

dimensions of the flaw shall be determined by the rectangle that fully

contains the area of the flaw. (Refer to Figs. 1-5.)

(a) The length (l) of the flaw shall be drawn parallel to the inside

pressure-retaining surface of the component.

(b) The depth of the flaw shall be drawn normal to the inside pressure

retaining surface and shall be denoted as "a" for a surface flaw or

"2a“ for a subsurface flaw.

Charlie Chong

(b) Multiple Flaws

(1) Discontinuous flaws shall be considered a singular planar

flaw if the distance between adjacent flaws is equal to or less

than S as shown in Fig. 2.

(2) Discontinuous flaws that are oriented primarily in parallel

planes shall be considered a singular planar flaw if the

distance between the adjacent planes is equal to or less than

1/2 in. (13 mm). (Refer to Fig. 3.)

(3) Discontinuous flaws that are coplanar and nonaligned in the

through-wall thickness direction of the component shall be

considered a singular planar flaw if the distance between

adjacent flaws is equal to or less than S as shown in Fig. 4.

(4) Discontinuous flaws that are coplanar in the through-wall

direction within two parallel planes 13 mm (1/2 in.) apart (i.e.,

normal to the pressure-retaining surface of the component)

are unacceptable if the additive flaw depth dimension of the

flaws exceeds those shown in Fig. 5.

(c) Subsurface Flaws. Flaw length (l) shall not exceed 4t.

Charlie Chong

Charlie Chong

Figure 2

Charlie Chong

Figure 3

Charlie Chong

Figure 4

Charlie Chong

Figure 5

(j) Examination data including the data record of (c) above and data analysis

or interpretation of (i) above shall be reviewed by a UT level III individual.

When flaw evaluation or characterization of (i) above are performed by

another qualified level II or III individual, their review may be performed by

another individual from the same organization. Examination data review shall

include verification that the records indicated in Section V, Article 4, T-491 and

T-492 and records noted in the applicable Article 4 appendices are available.

B31.3, para 346 applies.

Alternatively, the review may be achieved by arranging for a data acquisition

and initial interpretation by a Level II individual qualified in accordance with

paras. (f) and (h) above, and a final interpretation and evaluation shall be

performed by a Level III individual qualified similarly. The Level III individual

shall have been qualified in accordance with para. (f) above, including a

practical examination on flawed specimens.

Charlie Chong

Charlie Chong

(d) With the owner’s approval, the flaw acceptance criteria in Table 2 for wall

thicknesses between 25 mm (1 in.) and 54 mm (2½ in.) may be used for wall

thicknesses of less than 25 mm (1 in.). The maximum allowable flaw depth for

qualification purposes shall be specified.

Charlie Chong

ASME V-T-490 DOCUMENTATION

T-491 RECORDING INDICATIONS

T-491.1 Non rejectable Indications. Non rejectable indications shall be recorded as specified by the referencing

Code Section.

T-491.2 Rejectable Indications. Rejectable indications shall be recorded. As a minimum, the type of indication

(i.e., crack, non fusion, slag, etc.), location, and extent (i.e., length) shall be recorded. Non mandatory

Appendices D and K provide general recording examples for angle and straight beam search units. Other

techniques may be used.

T-492 EXAMINATION RECORDS

For each ultrasonic examination, the following information shall be recorded:

(a) procedure identification and revision;

(b) ultrasonic instrument identification (including manufacturer’s serial number);

(c) search unit(s) identification (including manufacturer’s serial number, frequency, and size);

(d) beam angle(s) used;

(e) couplant used, brand name or type;

(f) search unit cable(s) used, type and length;

(g) special equipment when used (search units, wedges, shoes, automatic scanning equipment, recording equipment, etc.);

(h) computerized program identification and revision when used;

(i) calibration block identification;

(j) simulation block(s) and electronic simulator(s) identification when used;

(k) instrument reference level gain and, if used, damping and reject setting(s);

(l) calibration data [including reference reflector(s), indication amplitude(s), and distance reading(s)];

(m) data correlating simulation block(s) and electronic simulator(s), when used, with initial calibration;

(n) identification and location of weld or volume scanned;

(o) surface(s) from which examination was conducted, including surface condition;

(p) map or record of rejectable indications detected or areas cleared;

(q) areas of restricted access or inaccessible welds;

(r) examination personnel identity and, when required by referencing Code Section, qualification level;

(s) date of examination.

Items (b) through (m) may be included in a separate calibration record provided the calibration record identification is included in

the examination record.

ASME B31.1- 346 RECORDS

346.2 Responsibility

It is the responsibility of the piping designer, the manufacturer, the fabricator,

and the erector, as applicable, to prepare the records required by this Code

and by the engineering design.

346.3 Retention of Records

Unless otherwise specified by the engineering design, the following records

shall be retained for at least 5 years after the record is generated for the

project:

(a) examination procedures

(b) examination personnel qualifications

Charlie Chong

Charlie Chong

B31 Case 181 2 (Approval Date: January 4,

2012) Use of Alternative Ultrasonic

Examination Acceptance Criteria in ASME

B31.3

Charlie Chong

B31 Case 181-2

Original Inquiry: Under what conditions and limitations may alternative

UT acceptance criteria apply in lieu of those described in para.

344.6.2 of ASME B31.3?

When specified by the owner, the ultrasonic examination acceptance criteria

included below may be applied for welds in material greater than or equal to

25mm (1.0 in.) in thickness 1 in accordance with ASME B31.3 provided the

following requirements are met:

1) General/Scope:

a) The examination shall be conducted using automated or semiautomated

techniques utilizing computer based data acquisition.

b) The examination shall be performed in accordance with a written

procedure approved by a Level III and conforming to the

requirements of ASME Section V, Article 4 Mandatory Appendix VIII

and:

i) For Phased Array – ASME Section V, Article 4, Mandatory

Appendix V

ii) For Time of Flight Diffraction (TOFD) - ASME Section V, Article 4,

Mandatory Appendix III

c) Procedure qualification shall meet the requirements of ASME Section

V, Article 4, Mandatory Appendix IX.

1

For wall thicknesses less than 25mm (1.0 in.), the acceptance criteria stated

in paragraph 344.6.2 of B31.3 shall be used.

Charlie Chong

344.6.2 Acceptance Criteria. A linear-type discontinuity is unacceptable if

the amplitude of the indication exceeds the reference level and its length

exceeds

(a) 6 mm (1⁄4 in.) for T w ≤ 19 mm (3/4 in.)

(b) T w 3 for 19 mm < T w ≤ 57 mm (2 1/4 in.)

(c) 19 mm for T w > 57 mm

Keywords:

linear-type discontinuity

Charlie Chong

2) Equipment

A mechanical guided scanner capable of maintaining a fixed and consistent

search unit position relative to the weld centerline shall be used.

3) Personnel

a)Set-up and scanning of welds shall be performed by personnel certified as

Level II or III (or by Level I personnel under the direct supervision of Level II

personnel).

b)Interpretation and evaluation of data shall be performed by Level II or III

personnel.

c)Examination personnel shall be qualified and certified following a procedure

or program as described in ASME BPV Code, Section V, Article 1, T-120 (e),

(f), (h) and (i).

d)Personnel demonstration requirements shall be as stated in ASME Section

V, Article 4 Mandatory Appendix VII.

Charlie Chong

Charlie Chong

4) Examination

a)The initial straight beam scan for reflectors that could interfere with the

angle beam examination shall be performed (a) manually, (b) as part of a

previous manufacturing process, or (c) during the weld examination, provided

detection of these reflectors is included in the demonstration as required in

1(c) above.

b)The examination area shall include the volume of the weld, plus the lesser

of 25mm (1.0 in.) or t of adjacent base metal. Alternatively, the examination

volume may be reduced to include the actual heat affected zone (HAZ) plus

6mm (0.25 in.) of base material beyond the heat affected zone on each side

of the weld, provided the extent of the weld HAZ is measured and

documented.

c)Scanning may be performed at reference level provided the procedure

qualification was performed at reference level.

Charlie Chong

The examination area shall include the volume of the weld, plus the lesser of

25mm (1.0 in.) or t of adjacent base metal. Alternatively, the examination

volume may be reduced to include the actual heat affected zone (HAZ) plus

6mm (0.25 in.) of base material beyond the heat affected zone on each side

of the weld, provided the extent of the weld HAZ is measured and

documented.

Charlie Chong

5) Data Recording

Data shall be recorded in the

unprocessed form with no thresholding.

The data record shall include the

complete examination area as specified

in (4)(b) above.

Charlie Chong

Stored valves shall be commercially cleaned before re-testing and before

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Charlie Chong


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300.2 Definitions

Some of the terms relating to piping are defined below. For welding, brazing,

and soldering terms not shown here, definitions in accordance with AWS

Standard A3.03 apply.

fluid service: a general term concerning the application of a piping system,

considering the combination of fluid properties, operating conditions, and

other factors that establish the basis for design of the piping system. See

Appendix M.

(a) Category D Fluid Service: a fluid service in which all of the following apply:

(1)the fluid handled is nonflammable, nontoxic, and not damaging to human

tissues as defined in para. 300.2

(2)the design gage pressure does not exceed 1 035 kPa (150 psi)

(3)the design temperature is not greater than 186°C (366°F)

(4)the fluid temperature caused by anything other than atmospheric

conditions is not less than −29°C (−20°F)

Charlie Chong

(b) Category M Fluid Service: a fluid service in which the potential for

personnel exposure is judged to be significant and in which a single exposure

to a very small quantity of a toxic fluid, caused by leakage, can produce

serious irreversible harm to persons on breathing or bodily contact, even

when prompt restorative measures are taken.

(c) Elevated Temperature Fluid Service: a fluid service in which the piping

metal temperature is sustained equal to or greater than Tcr as defined in

Table 302.3.5, General Note (b).

(d) High Pressure Fluid Service: a fluid service for which the owner specifies

the use of Chapter IX for piping design and construction; see also para. K300.

Charlie Chong

(e) High Purity Fluid Service: a fluid service that requires alternative methods

of fabrication, inspection, examination, and testing not covered elsewhere in

the Code, with the intent to produce a controlled level of cleanness. The term

thus applies to piping systems defined for other purposes as high purity, ultra

high purity, hygienic, or aseptic.

(f) Normal Fluid Service: a fluid service pertaining to most piping covered by

this Code, i.e., not subject to the rules for Category D, Category M, Elevated

Temperature, High Pressure, or High Purity Fluid Service.

Charlie Chong

Charlie Chong


shipment.

There are many valve designs, types and models, with a wide range of

industrial applications. All satisfy one or more of the functions identified above.

Valves are expensive items, and it is important that a correct valve is

specified for the function, and must be constructed of the correct material for

the process liquid.

Regardless of type, all valves have the

following basic parts:

■ the body,

■ bonnet,

■ trim (internal elements),

■ actuator, and

■ packing.

The basic parts of a valve are illustrated

in the image on the right.


http://www.wermac.org/valves/valves_general.html

1.0 Valve Body

The valve body, sometimes called the shell, is the primary boundary of a

pressure valve. It serves as the main element of a valve assembly because it

is the framework that holds all the parts together.

The body, the first pressure boundary of a valve, resists fluid pressure loads

from connecting piping. It receives inlet and outlet piping through threaded,

bolted, or welded joints.

The valve-body ends are designed to connect the valve to the piping or

equipment nozzle by different types of end connections, such as butt or

socket welded, threaded or flanged.

Valve bodies are cast or forged in a variety of forms and each component

have a specific function and constructed in a material suitable for that function.



2.0 Valve Bonnet

The cover for the opening in the body is the bonnet, and it is the second most

important boundary of a pressure valve. Like valve bodies, bonnets are in

many designs and models available.

A bonnet acts as a cover on the valve body, is cast or forged of the same

material as the body. It is commonly connected to the body by a threaded,

bolted, or welded joint. During manufacture of the valve, the internal

components, such as stem, disk etc., are put into the body and then the

bonnet is attached to hold all parts together inside.

In all cases, the attachment of the bonnet to the body is considered a

pressure boundary. This means that the weld joint or bolts that connect the

bonnet to the body are pressure-retaining parts. Valve bonnets, although a

necessity for most valves, represent a cause for concern. Bonnets can

complicate the manufacture of valves, increase valve size, represent a

significant cost portion of valve cost, and are a source for potential leakage.



5 Valve Certification and Retesting

5.1 CERTIFICATE OF COMPLIANCE

When specified by the purchaser, the valve manufacturer shall submit to the

purchaser a certificate of compliance as required in the purchase order.

5.2 RE-TESTING

A completed valve does not require re-testing unless inspection by the

purchaser is specified in the purchase order.

This re-testing may be waived by the purchaser’s inspector upon written

certification by the manufacturer that he valve has been inspected, tested,

and examined for conformance with the requirements of this standard.

Painted valves need not have paint removed for re-testing.


shipment.


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Good Luck!

ASME Code Case 181

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