Misconceptions and Misapplication of Production Valve Test Standards It’s really about detecting Leaks
Greg Smith- Director, Quality and Productivity
Improvement
From an engineering viewpoint there is no such thing as a “zero leak”
Std cc/sec Reference Rate Comments
1x10-8 Leak 1 cc every 3 years Diffusion of helium through
glass per square cm of
surface area
1x10-7 Leak rate of 3 cc/year About the size of 3 marbles
1x10-6 About 1 cc every 2 days Breathing on a leak this size
can provide enough
moisture to temporarily close
the leak
1x10-5 About 1 cc/day Better deploy a wetting
agent to detect this during
water immersion testing
1x10-4 About a cc every 3 hours Visible bubbles rising in
water immersion
1x10-3 4 cc/hour A leak of this size is readily
detectible using water
immersion
1x10-1 & up Too much! Audible
Definition of Leak Testing Sensitivity
Leak test sensitivity refers to how small a physical leak
can be detected, that is the minimum detectable size of
leak.
To avoid the difficulty of using dimensions that usually
could never be measure, a leak is measured by how
much leakage will occur in a specific period of time
under specific leak test conditions.
(ASNT NDT Handbook 2nd Edition)
Many of the Industry Specifications define the Test
Conditions , and in that sense they become
standardized.
Example from API 598
Gas test at 41 deg F -122 deg F
Pressure differential for the test 60-80 psig
Test Media Air or inert gas
:
Variations in basic test parameters
:
Standard Gas Test water
chlorides
Temperature
ASME B16.34 > 80 psi NA <125 deg F
API-598 60-80 psi <100* 41-122 deg F
MSS SP-61 60-100 psi NA <125 deg F
ISO-5208 6 bar +/-1
bar(73-102
psi)
<100* >5 deg C < 40
deg C(41-106
deg F)
API 6D NA <30**
(by mass)
>5 deg C < 40
deg C(41-106
deg F)
*austenitic stainless steel valves
** wetted components austenitic & duplex stainless steels
Visual Acuity for Test Operators
Check the vision of testing personnel
annually for their natural or corrected near
distance acuity. SNT-TC-1A recommends
"Jaeger Number 2 or equivalent type and
size letter at the distance designated on the
chart but not less than 12 inches (30.5 cm)
on a standard Jaeger test.
(From a practical perspective, a color blind
test is encouraged as well)
Test Configuration…continuedProvide a clear and unobstructed view of the test
valve
•Direct visual examination may usually be
made when access is sufficient to place the
eye within 24 in. (600 mm) of the surface to
be examined and at an angle not less than
30 deg to the surface to be examined.
•The minimum light intensity at the
examination surface/site shall be 100
footcandles.
Test Configuration
When a view of the test object is obstructed:
Remote visual examination may have to be
substituted for direct examination. (Mirrors,
telescopes, borescopes, fiber optics,
cameras, or other suitable instruments shall
have a resolution capability at least
equivalent to that obtainable by direct visual
observation.
Para-phased from 2007 ASME V
Sensitivities Attainable with Immersion Bubble TestingThe sensitivity of the bubble emission leak test is hard
to define because this depends upon the observation
and alertness of the leak test operator
When locating leaks in the 10-4 std. cm3/sec. the
component after being immersed, has to be completely
stripped of attached air bubbles so that the bubbles
formed by leakage gas may be detected.
It is an ideal method for quick detection of large to
moderate size leaks (10-2 std.cm3/sec. to 10-3 std.
cm/sec)at very low costs
(ASNT NDT Handbook 2nd Edition)
Sensitivities Attainable with Liquid Film Bubble Testing
The sensitivity of the liquid application technique of
bubble leak testing is adequate for locating leaks with
leakage rates in excess of 10-4 std. cm3/sec.
(pg.393 ASNT NDT Handbook 2nd Ed.)
The bubble forming solution shall produce a film that
does not break away from the area to be tested, and
the bubbles formed shall not break rapidly due to air
drying or low surface tension. Household soap or
detergents are not permitted as substitutes for bubble
testing solutions.
The bubble forming solution shall be applied to the
surface to be tested by flowing, spraying, or brushing
the solution over the examination area.
2007 ASME V
Improve the Sensitivity of Bubble Testing
Increase the pressure differential across the leak
Apply a gas with a low molecular weight
Introduce gas prior to immersion in detection liquid.
Optimize the position of test surfaces intended for
visual observation
Improve the lighting to highlight bubble emissions
Use clear translucent immersion fluids & maintain
clarity
Increase time for bubble formation & observation
Eliminate any false bubble indications
Decrease the surface tension of the detection liquid
so formed bubbles are smaller
Personnel Safety and Testing with Compressible Fluids:
Shock wave overpressures:
A pressure wave of >5 PSI eardrum rupture
>15 PSI permanent lung
damage
>35 PSI fatalities
(ASNT NDT Handbook 2nd Ed.)
When inert gas is used, safety aspects of
oxygen deficient atmosphere should be
considered.
Mitigation of Risk
Shell tests are specified to accomplish the following:
“A pressure test in excess of the cold-working
–pressure , CWP, rating of the valve for the purpose of
validating the soundness and strength of the valve
pressure containing structures.”
API598 ninth edition
“Test at a pressure in excess of the cold
working pressure rating of a valve for the purpose of
validating the soundness and strength of the valve
pressure containing and retaining structures.
Note: These structures include valve actuating
mechanisms that have a direct connection to the valve
internal subject to fluid test pressure within the valve
proper.” ISO 5208:2008(E)
Irrespective of the testing protocol, your customer will
call you if valve leaks through the pressure boundary.
It’s our obligation to learn from the occurrence and
continuously improve the supplier chain and validation
process when these events do occur.
Visually Detectible Leakage Through the Pressure Boundary Walls is not Acceptable
The receiving scenario:
• Customer gas tests new valve fresh from the crate
• Applies a liquid film solution to the closure element
• Wets the entire valve down with a liquid film solution
• Patiently observes until bubbles form on the cast body
What next? It’s your brand, and your opportunity.
Relative Cost of Testing Equipment
The cost of detecting a leak depends of the sensitivity of
detection. The greater the sensitivity the higher the cost.
Bubble Immersion Test:
Water must remain clear to retain the sensitivity of the
immersion test and changed at regularly scheduled
intervals
Low surface tension immersion liquids can be
accomplished by the addition of wetting agents into the
test water. The resulting test liquid will dramatically
reduce the radius of the bubble formed at the end of a
capillary leak.
“When a test liquid does not wet the solid surface around
the orifice of a leak, the bubble rim tends to spread away
from the leak orifice. This results in the formation of
larger bubbles.” (ASNT NDT Handbook 2nd Ed.)
Bubble Immersion Test:
“Use of low surface tension liquids might theoretically reveal
leakage rates in the range of 1/50 to 1/100 of the lowest
leakage rates detectable when bubbles are formed in water.”
(ASNT NDT Handbook 2nd Ed.)
Percentage
Additive (In
Immersion Water
Minimum Detectable Leakage
Rate with Nitrogen Gas at
120KPa (Gauge) or 18 psig
0 1 x 10-3 std cm3/sec
1 1 x 10-4
5 1 x 10-5
25 1x 10 -6
A good offence (prevention) is the best defense.
Dewpoint temperature is the temperature that gas can
hold no additional water vapor and condensation of
moisture takes place. Apply a dewpoint sensor to
monitor compressed air systems to retain test air
which is free of condensed moisture.
If the objective is to find minute porosity in cast or
welded structures, there are numerous tests utilizing
air or inert gas that will be more effective than tests
that use high pressure water.
Introducing the air prior to immersion in the detection
liquid will improve the leak test sensitivity, by avoiding
the capillary action of water into the pores of the
material. Water and other liquids can actually clog
leaks.
“The surface areas to be tested shall be free of oil,
grease, paint, or other contaminants that might mask
a leak. If liquids are used to clean the component or if
a hydrostatic or hydropneumatic test is performed
before leak testing, the component shall be dry before
leak testing.” 2007 ASME V
Alternatives to Bubble Leak Testing:
If the objective is to detect a bubble, why make
the bubble radius smaller?
Pressure Change Testing
The test sensitivity is established against known
commercially available calibrated leak device
A leak test technician monitors the color of the panel lights
to identify on a pass-fail basis
Advantage: Operator follows the defined sequence, and
close, prolonged observation for leaks is mitigated.
Disadvantage: The leak location is not identified.
Note: For automatic leak detection methods, “no visible leakage” is defined in MSS SP-61
as a leak no greater than 6.7x10-4 ml/sec. with a pressure differential of 80-100 psi for
valves NPS 8” & smaller.
The Test Procedure
A documented procedure to conduct a test
including the elements of the test, both essential
and nonessential variables.
When an essential variable is changed, the
procedure qualification is effected because the
sensitivity of the test is potentially impacted
Requirements
Example
Essential
Variables
Nonessential
Variables
Test solution X
Lighting intensity X
Post cleaning X
Pressurizing gas X
The Test Procedure Qualification
Preproduction testing conducted under controlled
conditions, which document the actual sensitivity and
reliability of the testing procedure in detecting leaks.
The procedure includes the parameters of the testing
process including but not limited to personnel
qualification requirements, how to prepare the item to
be tested, the method of application of the test
solution. Some other elements include test pressure,
test fluid, duration, lighting, applicable remote viewing
and qualification of that device.
Personnel Qualification & Record
Written procedure to establish the minimum
requirements for education, training, experience,
examination, and qualification of personnel
responsible for conducting testing.
Training is typically followed by both a written
examination and a practical demonstration of
competency where the results are recorded and
retained.
Requirements for retesting due to failing results
are defined.
Control Valve Seat Leakage vs. a Cup of Coffee
Liquid Test 4”
diameter seat
Leakage Rate
ml/min
Time to fill a 14
oz. cup of
coffee
ISO 5208 Third
edition Rate A
0 -
ISO 5208 Third
edition Rate B
0.06 A little less than
5 days
ISO 5208 Third
edition Rate C
0.18 About a day and
a half
ANSI/FCI 70-2-
2006 class V
0.55 12.5 hours
ISO 5208 Third
edition Rate D
0.60 11.5 hours
Summary and Conclusions:
Industrial valve customers are specifying casting examination
and upgrade, similar to requirements intended for special class
valves in ASME B16.34.
NDT methods such as radiography, magnetic particle
examination, liquid dye penetrant tests all have their strengths
and limitations.
To detect through wall capillary leaks formed during casting
solidification, in fabrication, and defect removal by welding, the
industry should consider changes which include greater
utilization of gas testing.
There’s an Opportunity to Improve the Standards
1. Require a low pressure gas shell test to reliably identify
small leaks, and do so prior to filling the potential
leakage capillaries with water during other tests.
2. Encourage the use of clear immersion fluids and wetting
agents for improved sensitivity of leak detection.
3. Address the protective coatings deployed to protect
ferrous materials and the sequence in which they are
applied with respect to pressure testing
The liquid shell test is known to be an efficient means to assure
the strength of pressure containing structures, yet this test does
less well in revealing small leak paths.
Requirements Overview ASME B16.34ASME B16.34-2009 Valves-Flanged, Threaded, and Welding End
Test Requirement Description of Test Requirement Additional Controls
Shell Gage pressure no less than 1.5 x >100 deg. F rating rounded up to next 25 psi
increment. Visually detectable leakage through the pressure boundary walls not
acceptable
In partially open position
Shell Test Duration NPS< 2” at least 15 sec.
2.5 <NPS<6” at least 60 sec.
8 <NPS<12” at least 120 sec.
14”< NPS at least 300 sec.
Test time is the period of inspection after the valve is fully prepared & is
under shell test pressure
Stem seal Stem seals shall be capable of retaining pressure at least equal to the 100 deg. F
ratings w/o visible leakage
LP Closure At mfr’s option gas test >80psi. may be substituted for HP closure test as follows:
Valve Size Pressure Class
NPS < 4” < 2500
NPS <12” < 300
Refer to Note 1
Closure test leakage acceptance criteria shall be by agreement between
manufacturer and purchaser
HP Closure Test shall not be less than 110% of the 100 deg F pressure rating
Refer to option for LP Closure above
Refer to Note 1
Closure test leakage acceptance criteria shall be by agreement between
manufacturer and purchaser
Closure Test Duration NPS < 2” at least 15 sec.
2 1/2” < NPS< 8” at least 30 sec.
10”< NPS < 18” at least 60 sec.
< 20” NPS at least 120 sec.
Backseat provision No
Double seating provision Pressure applied successively on each side
Visual examination of castings MSS SP-55
Directional sealing provision Test in direction producing the most adverse condition
Restricted Seating for less than the 100
deg. F rating
Test may be reduced to 110% of maximum specified closed position differential
pressure
Test Fluid Temperature <125 deg. F
Detection Fluids Water which may contain a corrosion inhibitor, kerosene, or other suitable fluid w/ a
viscosity not greater than water
Cautionary statement concerning gas shell testing hazards
End Clamping restrictions None identified
Leakage detection devices May be used for detecting leakage provided that they are used at the required
pressures
Manufacturer shall have demonstrated that test results are equivalent to
requirements
Surface protection Valves shall not be painted or otherwise coated with materials capable of sealing
against leakage before shell tests are completed
Chemical corrosion protection treatment is permitted
Allowance made for internal linings or coatings included in the design.
Refer to Note 2
Supplementary Examinations For Special Class Valves per mandatory examinations in appendix
Note 1: Closure tests shall follow the shell test except for valves NPS 4” and smaller w/ ratings Class 1500 & lower the closure test may precede the shell test when a gas closure is used.
Note 2: Refer to Code for assembled valves having bodies & bonnets or cover plates that have been separately tested
Requirements Overview API Standard 598, API Standard 598, Ninth Edition, September 2009
Test Requirement Description of Test Requirement Additional Controls
Shell Where applicable same as ASME B16.34. Additional valve materials included by NPS and
pressure Class Visually detectable leakage through the pressure boundary walls and any
fixed body joint is not permitted
When specified by the purchaser a high pressure
pneumatic shell test shall be performed after the shell
test. Test is at 110% of the max. allowable pressure
at 100 deg F. visible leakage is not allowed
Shell Test Duration < 2” NPS 15 sec. minimum
2.5 - 6” NPS 60 sec. minimum
8”- 12” NPS 120 sec. minimum
>14” NPS 300 sec. minimum
Test time is the period of inspection after the valve is
fully prepared & is under full pressure
Stem seal Leakage through the stem seals during the shell test shall not be cause for rejection.
However, stem seals shall be capable of retaining pressure at least equal to the 100 deg. F
ratings w/o visible leakage
Visible leakage through nonadjustable stem seals is
not permitted.
LP Closure Gas test at 60-100 psig
(refer to standard for applicability by valve type, size, material and pressure class
Refer to note 1
Multiple clarifications and restrictions concerning
testing protocol by valve type, size, material and
pressure class.
External forces that affect seat leakage prohibited
HP Closure 110% of maximum allowable pressure at (100 deg. F) or design differential pressure or test
pressure specified in Table 4 depending on valve size, Class and type.
Multiple clarifications and restrictions concerning
testing protocol by valve type, size, material and
pressure class
Refer to note 2:
Closure Test Duration < 2” NPS 15 sec. minimum (except for check valves API 594 60 sec. min.)
2.5 - 6” NPS 60 sec. minimum
8”- 12” NPS 120 sec. minimum
>14” NPS 120 sec. minimum
Backseat Test As applicable to valve type
A high or low pressure test at the manufacturers option
Excludes bellows seals. Multiple clarifications and
restrictions concerning testing protocol
Double Block & Bleed high pressure closure test Apply pressure successively to each side , monitor at position G
Visual examination of castings MSS SP-55
Supplementary Examinations Part 8, ASME B16.34 Optional
Directional sealing provision Apply pressure on pressure side only
Restricted Seating for less than the 100 deg. F
rating
Test at 110% of maximum specified closed differential
Test Fluid Temperature 41 deg F to 122 deg. F
Detection Fluids Air, inert gas, kerosene, or a noncorrosive liquid with a viscosity not higher than that of water.
When testing austenitic stainless steels the chloride content shall not exceed 100 ppm .
Low pressure closure and low pressure backseat shall
be air or inert gas.
End Clamping restrictions None
Leakage detection devices Allowed- when manufacturer can demonstrate and validate that the procedure yields
equivalent results
Surface protection Required protective coatings such as paint which may mask surface defects shall not be
applied to any surface before inspection or pressure testing
Allowance permitted for chemical conversion
processes
Note 1: Closure tightness requirements vary by valve type, size and seat material. For resilient seat valves the maximum allowable leakage is zero (0) Note 2: The high pressure closure test of resilient seated valves may degrade subsequent sealing performance in low pressure service” 9th Ed. API-598 9/2009
Requirements Overview MSS SP-61MSS SP-61-2009 Pressure Testing of Valves
Test Requirement Description of Test Requirement Additional Controls
Shell 1.5 x >100 deg. F design pressure rating rounded up to next 25 psi increment.
Visually detectable leakage through the pressure boundary walls is not
acceptable
Shell test precedes the closure test.
For a hydrostatic test there shall be no visible weeping or formation
of drops at the test press and for the duration of the test.
For air or gas testing no visible formation of bubbles in a water
immersion test or application of a leak detection fluid at the test
pressure and for the duration of the test.
Shell Test Duration < 2” NPS and smaller at least 15 sec.
2.5 - 8” NPS at least 60 sec.
10” & larger at least 180 sec.
Test time is the period of inspection after the valve is fully prepared
& is under full pressure
Stem seal Leakage through the stem seals during the shell test shall not be cause for
rejection. However, stem seals shall be capable of retaining pressure at least
equal to the 100 deg. F ratings w/o visible leakage
Visible leakage through nonadjustable stem seals is not permitted.
LP Closure Gas test at 60-100 psig
(refer to standard for applicability by valve type, size, material and pressure class
Acceptable leakage rate tabulated per NPS- Refer to note 1
Seat closure tests for NPS 4” and larger shall be conducted after
an acceptable shell test. For ASME B16.34 valves, requirements of
para. 7.2 from that Code apply.
HP Closure 110% of maximum allowable pressure at (100 deg. F) or design differential
pressure or test pressure specified in Table 4 depending on valve size, Class
and type.
Acceptable leakage rate tabulated per NPS-Refer to note 1
Seat closure tests for NPS 4” and larger shall be conducted after
an acceptable shell test. For ASME B16.34 valves, the
requirements of paragraph 7.2 from that Code apply.
Closure Test Duration < 2” NPS 15 sec. minimum except for check valves (API 594) 60 sec. min.
2.5 - 6” NPS 60 sec. minimum
8”- 12” NPS 120 sec. minimum
>14” NPS 120 sec. minimum
Backseat Test As applicable to valve type Excludes bellows seals. Multiple clarifications and restrictions
concerning testing protocol
Double seating provision Pressure applied successively to each side Alternate method for independent double seating provided for
Double Block and Bleed provision NA
Visual examination of castings NA
Directional sealing provision Pressure applied in the most adverse direction, and if marked for one direction
tested in the appropriate direction
Clarifications provided for valves with singular or symmetrical seat
and butterfly valves with offset stem design
Restricted Seating for less than the 100 deg. F rating Test at 110% of maximum specified closed differential
Test Fluid Temperature < 125 deg. F
Detection Fluids Air, inert gas or a liquid, such as water (which may include a corrosion inhibitor),
kerosene, or other fluid with a viscosity not higher than that of water.
End Clamping restrictions Loads are limited to those required to effectively seal valve ends
Leakage detection devices Allowed- Manufacturer must be able to demonstrate equivalent results to the
requirements of this standard
Definition shall be considered equivalent to a leak of 6.7x10-4
ml/sec. with a pressure differential of 80-100 psi for valves NPS 8”
and smaller
Surface protection Must be shell tested prior to painting Allowance permitted for chemical corrosion protection treatment
such as phosphatizing and lining may be applied prior to shell test
Supplementary Examinations NA
Note 1: For valves having a seat closure member that uses a compliant material, there shall be no visible leakage for the duration of the test.
Requirements Overview ISO 5208- Industrial Valves, Third Ed. 2008-08-01- Pressure testing of metallic valves
ISO 5208- Industrial Valves, Third Ed. 2008-08-01- Pressure testing of metallic valves
Test Requirement Description of Test Requirement Additional Controls
Shell 1.5 x (38 deg C) 100 deg. F CWP rating minimum Visually detectable leakage from any
external surface of the shell is cause for rejection
A liquid test is required.
Stem seal leakage is permitted provided that there is no visually
detectible leakage at 110% CWP
Shell Test Duration Valve Size
DN<50(2”) 15 sec. minimum
65<DN<150(2.5”- 6”) 60 sec. minimum
200<DN<300(8”-12”)180 sec. minimum
DN>350 (14”) 300 sec. minimum
Test time is the period of inspection after the valve is fully prepared & is
under test pressure
Stem seal No visually detectible leakage at 110% CWP during a liquid test
LP Closure Gas test at 6 bar +/-1 bar(72.5-101.5 psi)
(refer to standard for applicability by valve type, size, material and pressure class)
Successful completion of an optional test does not relieve the
manufacturer from successful completion of required test.
HP Closure Liquid test at 110% of CWP minimum
(refer to standard for applicability by valve type, size, material and pressure class)
In the case of resilient seated vales, a high pressure test mat degrade
subsequent sealing performance in low pressure applications
Closure Test Duration Valve Size
DN<50(2”) 15 sec. minimum ( except 60 sec. for check valves)
65<DN<150(2.5”- 6”) 60 sec. minimum
200<DN<300(8”-12”)120 sec. minimum
DN>350 (14”) 120 sec. minimum
Backseat Test Optional when so specified by the purchaser for relevant valves. not required for bellows
stem seals
A liquid test at 110% of valve CWP minimum. Multiple
recommendations for testing protocol
Double seating provision Provides for closure testing progressing for gat ball and plugs valves
Double Block and Bleed provision High pressure closure test is required, low pressure closure test is optional
High pressure pneumatic shell test Optional Test fluid is gas at 110% of CWP, minimum. Liquid shell test should be
performed first. Continuous formation of bubbles from external surface
is cause for rejection
Directional sealing provision Testing protocol defined for valves with a unidirectional flow marking
Restricted Seating for less than the
100 deg. F rating
Per agreement between the purchaser and manufacturer. Test at a pressure of 1.1 x the
design differential pressure
I.D. plate with limitation required
Temperature >5 deg. C < 40 deg. C (104 deg. F)
Detection Fluids Water (which may contain a corrosion inhibitor), kerosene, or other appropriate liquid fluid
having a viscosity not greater than that of water.
Air or other suitable gas
When water is the test fluid the chloride content a the shall not exceed
100 ppm when testing austenitic stainless steels
Purchaser may specify that a wetting agent be added to the water used
as a test fluid
End Clamping restrictions When end clamping devices are used, the manufacturer shall be able to demonstrate that,
during the valve closure test, they do not serve to reduce the resultant leakage
Leakage detection devices Allowed- Manufacturer shall be capable of demonstrating equivalence of the system with the
requirements of this international standard
Surface protection Shall not be externally painted or coated with materials capable of sealing against leakage
from external surfaces of the shell. Internal linings and coatings that form a design feature
are permitted to be tested with them in place
Chemical corrosion protection treatments prior to shell testing are not
mentioned.
Location Pressure tests shall take place either at the site of the valve manufacture, or at a test facility
under the supervision of the valve manufacturer.
Note 1: For valves having a seat closure member that uses a compliant material, there shall be no visible leakage for the duration of the test.
Requirements Overview API Standard 6D, 23rd Edition, April 2008- Specification for Pipeline Valves
API Standard 6D, 23rd Edition, April 2008- Specification for Pipeline Valves
Test Requirement Description of Test Requirement Additional Controls
Shell 1.5 or more times the 100 deg F pressure rating. No visible
leakage is permitted during the test.
Provision to remove relief valve valves when applicable
Shell Test Duration 1/2”- 4” NPS… 2 minutes minimum
6”-10” NPS …..5 minutes minimum
12”-18” NPS. .15 minutes minimum
>20” NPS….. 30 minutes minimum
Provision to test the relief valve connection
Stem seal Leakage through the stem seals not permitted
LP Closure Not applicable- Alternative inert gas seat test is allowed after shell
testing by agreement and remains a high pressure test
HP Closure Shall not be less than 1.1 times the100 deg F pressure rating Soft seated and lubricated plug valves shall not exceed ISO 5208 rate A (no
visible leakage) Metal seated valves shall not exceed ISO 5208-1993, Rate D.
Seat test procedures for block valves described within the standard.
Alternative gas pressure tests may be specified by the purchaser.
Closure Test Duration 1/2”-4” NPS….2 minutes minimum
> 6” NPS……..5 minutes minimum
Backseat Test When applicable and packing gland loosened unless a test port is
provided
1.1 x 100 deg F pressure rating, no leakage permitted. Test is performed prior
to the hydrostatic shell test.
Double Block & Bleed
Provision
With valve 1/2 open the valve and cavity completely filled with test
fluid. The valve is closed, body vent opened to allow excess fluid to
drain.
Test pressure applied simultaneously from both ends. Seat tightness is
monitored via overflow through the cavity drain connection.
Refer to note 1:
Unidirectional Provision Cavity completely filled with test fluid, valve is closed and test
pressure applied at appropriate end of valve
Monitored at body cavity vent or drain connection or downstream end of valve
Visual examination of
castings
MSS SP-55
Supplementary
Examinations
Optional Per normative annex
Bidirectional sealing
provision
Cavity completely filled with test fluid, valve is closed and test
pressure applied successively at both ends of valve
Monitored at body cavity vent or drain connection or downstream end of valve
Temperature 5 deg C -40 deg C
Detection Fluids Fresh water or by agreement light weight oil with a viscosity not
exceeding that of water
If the valve has wetted components of austenitic or duplex stainless steels
then chloride content shall not exceed 30 ppm by mass
End Clamping restrictions No restrictions
Leakage detection devices Not in scope
Surface protection Testing shall be carried out prior to coating of the valves
Note 1: Testing protocol also provided for double isolation and bleed DIB-1 (both seats bi-directional) and double isolation and
bleed DIB-2(one seat uni-directional and one seat bidirectional)
Requirements Overview ANSI/FCI 70-2-2006 American National Standard, Control Valve Seat Leakage, Fluid Controls Institute Inc.
ANSI/FCI 70-2-2006 American National Standard, Control Valve Seat Leakage, Fluid Controls Institute Inc.
Test Requirement Description of Test Requirement Additional Controls
Seat leakage classes defined for
control valves
Defines test media, temperature
range, pressure ranges and leakage
flow
Actual leakage is measured and compared to calculated
values as a % of value capacity or volume over time for
applicable orifice or seat diameter according to seat
diameter depending on leakage class