33 CFR Appendix A to Part 154, Guidelines for Detonation Flame Arresters
This appendix contains the draft ASTM standard for detonation flame arresters. Devices meeting this standard will be accepted by the Commandant (CG-ENG).
1.1 This standard provides the minimum requirements for design, construction, performance and testing of detonation flame arresters.
2.1 This standard is intended for detonation flame arresters protecting systems containing vapors of flammable or combustible liquids where vapor temperatures do not exceed 60 °C. For all tests, the test media defined in 14.1.1 can be used except where detonation flame arresters protect systems handling vapors with a maximum experimental safe gap (MESG) below 0.9 millimeters. Detonation flame arresters protecting such systems must be tested with appropriate media (the same vapor or a media having a MESG no greater than the vapor). Various gases and their respective MESG are listed in attachment 1.
2.2 The tests in this standard are intended to qualify detonation flame arresters for all in-line applications independent of piping configuration provided the operating pressure is equal to or less than the maximum operating pressure limit specified in the manufacturer's certification and the diameter of the piping system in which the detonation arrester is to be installed is equal to or less than the piping diameter used in the testing.
Detonation flame arresters meeting this standard as Type I devices, which are certified to be effective below 0 °C and which can sustain three stable detonations without being damaged or permanently deformed, also comply with the minimum requirements of the International Maritime Organization, Maritime Safety Committee Circular No. 373 (MSC/Circ. 373/Rev.1).
3. Applicable Documents
3.1 ASTM Standards 1
1 Footnotes appear at the end of this article.
3.2 ANSI Standards 2
3.3 Other Documents
3.3.1 ASME Boiler and Pressure Vessel Code 2
3.3.2 International Maritime Organization, Maritime Safety Committee 3
3.3.3 International Electrotechnical Commission 4
4.1 Δ P/Po - The dimensionless ratio, for any deflagration and detonation test of 14.3, of the maximum pressure increase (the maximum pressure minus the initial pressure), as measured in the piping system on the side of the arrester where ignition begins by the device described in paragraph 14.3.3, to the initial absolute pressure in the piping system. The initial pressure should be greater than or equal to the maximum operating pressure specified in paragraph 11.1.7.
4.2 Deflagration - A combustion wave that propagates subsonically (as measured at the pressure and temperature of the flame front) by the transfer of heat and active chemical species to the unburned gas ahead of the flame front.
4.3 Detonation - A reaction in a combustion wave propagating at sonic or supersonic (as measured at the pressure and temperature of the flame front) velocity. A detonation is stable when it has a velocity equal to the speed of sound in the burnt gas or may be unstable (overdriven) with a higher velocity and pressure.
4.4 Detonation flame arrester - A device which prevents the transmission of a detonation and a deflagration.
4.5 Flame speed - The speed at which a flame propagates along a pipe or other system.
4.6 Flame Passage - The transmission of a flame through a device.
4.7 Gasoline Vapors - A non-leaded petroleum distillate consisting essentially of aliphatic hydrocarbon compounds with a boiling range approximating 65 °C/75 °C.
5.1 The two types of detonation flame arresters covered in this specification are classified as follows:
5.1.1 Type I - Detonation flame arresters acceptable for applications where stationary flames may rest on the device.
5.1.2 Type II - Detonation flame arresters acceptable for applications where stationary flames are unlikely to rest on the device, and further methods are provided to prevent flame passage when a stationary flame occurs. One example of “further methods” is a temperature monitor and an automatic shutoff valve.
6. Ordering Information
6.1 Orders for detonation flame arresters under this specification shall include the following information as applicable:
6.1.1 Type (I or II).
6.1.2 Nominal pipe size.
6 1.3 Each gas or vapor in the system and the corresponding MESG.
6.1.4 Inspection and tests other than specified by this standard.
6.1.5 Anticipated ambient air temperature range.
6.1.6 Purchaser's inspection requirements (see section 10.1).
6.1.7 Description of installation.
6.1.8 Materials of construction (see section 7).
6.1.9 Maximum flow rate and the maximum design pressure drop for that maximum flow rate.
6.1.10 Maximum operating pressure.
7.1 The detonation flame arrester housing, and other parts or bolting used for pressure retention, shall be constructed of materials listed in ASTM F 1155 (incorporated by reference, see § 154.106), or section VIII, Division 1 of the ASME Boiler and Pressure Vessel Code. Cast and malleable iron shall not be used; however, ductile cast iron in accordance with ASTM A395 may be used.
7.1.1 Arresters, elements, gaskets, and seals must be made of materials resistant to attack by seawater and the liquids and vapors contained in the system being protected (see section 6.1.3).
7.2 Nonmetallic materials, other than gaskets and seals, shall not be used in the construction of pressure retaining components of the detonation flame arrester.
7.2.1 Nonmetallic gaskets and seals shall be non-combustible and suitable for the service intended.
7.4 The possibility of galvanic corrosion shall be considered in the selection of materials.
7.5 All other parts shall be constructed of materials suitable for the service intended.
8. Other Requirements
8.1 Detonation flame arrester housings shall be gas tight to prevent the escape of vapors.
8.2 Detonation flame arrester elements shall fit in the housing in a manner that will insure tightness of metal-to-metal contacts in such a way that flame cannot pass between the element and the housing.
8.2.1 The net free area through detonation flame arrester elements shall be at least 1.5 times the cross-sectional area of the arrester inlet.
8.3 Housings, elements, and seal gasket materials shall be capable of withstanding the maximum and minimum pressures and temperatures to which the device may be exposed under both normal and the specified fire test conditions in section 14, and shall be capable of withstanding the hydrostatic pressure test of section 9.2.3.
8.4 Threaded or flanged pipe connections shall comply with the applicable B16 standards in ASTM F 1155 (incorporated by reference, see § 154.106). Welded joints shall comply with ASTM F 722 (incorporated by reference, see § 154.106).
8.5 All flat joints of the housing shall be machined true and shall provide for a joint having adequate metal-to-metal contact.
8.6 Where welded construction is used for pressure retaining components, welded joint design details, welding and non-destructive testing shall be in accordance with Section VIII, Division 1, of the ASME Code and ASTM F 722 (incorporated by reference, see § 154.106). Welders and weld procedures shall be qualified in accordance with section IX of the ASME Code.
8.7 The design of detonation flame arresters shall allow for ease of inspection and removal of internal elements for replacement, cleaning or repair without removal of the entire device from the system.
8.8 Detonation flame arresters shall allow for efficient drainage of condensate without impairing their efficiency to prevent the passage of flame. The housing may be fitted with one or more drain plugs for this purpose. The design of a drain plug should be such so that by cursory visual inspection it is obvious whether the drain has been left open.
8.9 All fastenings shall be protected against loosening.
8.10 Detonation flame arresters shall be designed and constructed to minimize the effect of fouling under normal operating conditions.
8.11 Detonation flame arresters shall be capable of operating over the full range of ambient air temperatures anticipated.
8.12 Detonation flame arresters shall be of first class workmanship and free from imperfections which may affect their intended purpose.
8.13 Detonation flame arresters shall be tested in accordance with section 9.
9.1 Tests shall be conducted by an independent laboratory capable of performing the tests. The manufacturer, in choosing a laboratory, accepts that it is a qualified independent laboratory by determining that it has (or has access to) the apparatus, facilities, personnel, and calibrated instruments that are necessary to test detonation flame arresters in accordance with this standard.
9.1.1 A test report shall be prepared by the laboratory which shall include:
18.104.22.168 Detailed drawings of the detonation flame arrester and its components (including a parts list identifying the materials of construction).
22.214.171.124 Types of tests conducted and results obtained. This shall include the maximum temperature reached and the length of testing time in section 14.2 in the case of Type II detonation flame arresters.
126.96.36.199 Description of approved attachments (reference 9.2.6).
188.8.131.52 Types of gases or vapors for which the detonation flame arrester is approved.
184.108.40.206 Drawings of the test rig.
220.127.116.11 Record of all markings found on the tested detonation flame arrester.
18.104.22.168 A report number.
9.2 One of each model Type I and Type II detonation flame arrester shall be tested. Where approval of more than one size of a detonation flame arrester model is desired, only the largest and smallest sizes need be tested provided it is demonstrated by calculation and/or other testing that intermediate size devices have equal or greater strength to withstand the force of a detonation and have equivalent detonation arresting characteristics. A change of design, material, or construction which may affect the corrosion resistance, or ability to resist endurance burning, deflagrations or detonations shall be considered a change of model for the purpose of this paragraph.
9.2.1 The detonation flame arrester shall have the same dimensions, configuration, and most unfavorable clearances expected in production units.
9.2.2 A corrosion test shall be conducted. In this test, a complete detonation flame arrester, including a section of pipe similar to that to which it will be fitted, shall be exposed to a 20% sodium chloride solution spray at a temperature of 25 °C for a period of 240 hours, and allowed to dry for 48 hours. Following this exposure, all movable parts shall operate properly and there shall be no corrosion deposits which cannot be washed off.
9.2.3 The detonation flame arrester shall be subjected to a hydrostatic pressure test of at least 350 psig for ten minutes without rupturing, leaking, or showing permanent distortion.
9.2.4 Flow characteristics as declared by the manufacturer, shall be demonstrated by appropriate tests.
9.2.5 Detonation flame arresters shall be tested for endurance burn and deflagration/detonation in accordance with the test procedures in section 14. Type I detonation flame arresters shall show no flame passage when subjected to both tests. Type II detonation flame arresters shall show no evidence of flame passage during the detonation/deflagration tests in section 14.3. Type II detonation flame arresters shall be tested for endurance burn in accordance with section 14.2. From the endurance burn test of a Type II detonation flame arresters, the maximum temperature reached and the test duration shall be recorded and provided as part of the laboratory test report.
9.2.6 Where a detonation flame arrester is provided with cowls, weather hoods and deflectors, etc., it shall be tested in each configuration in which it is provided.
9.2.7 Detonation flame arresters which are provided with a heating arrangement designed to maintain the surface temperature of the device above 85 °C shall pass the required tests at the maximum heated operating temperature.
9.2.8 Each finished detonation arrester shall be pneumatically tested at 10 psig to ensure there are no defects or leakage.
10.1 The manufacturer shall afford the purchaser's inspector all reasonable access necessary to assure that the device is being furnished in accordance with this standard. All examinations and inspections shall be made at the place of manufacture, unless otherwise agreed upon.
10.2 Each finished detonation arrester shall be visually and dimensionally checked to ensure that the device corresponds to this standard, is certified in accordance with section 11 and is marked in accordance with section 12. Special attention shall be given to the checking of welds and the proper fit-ups of joints (see sections 8.5 and 8.6).
11.1 Manufacturer's certification that a detonation flame arrester meets this standard shall be provided in an instruction manual. The manual shall include as applicable:
11.1.1 Installation instructions and a description of all configurations tested (reference paragraph 9.2.6). Installation instructions to include the device's limitations.
11.1.2 Operating instructions.
11.1.3 Maintenance requirements.
22.214.171.124 Instructions on how to determine when arrester cleaning is required and the method of cleaning.
11.1.4 Copy of test report (see section 9.1.1).
11.1.5 Flow test data, maximum temperature and time tested (Type II).
11.1.6 The ambient air temperature range over which the device will effectively prevent the passage of flame.
Other factors such as condensation and freezing of vapors should be evaluated at the time of equipment specification.
11.1.7 The maximum operating pressure for which the device is suitable.
12.1 Each detonation flame arrester shall be permanently marked indicating:
12.1.1 Manufacturer's name or trademark.
12.1.2 Style, type, model or other manufacturer's designation for the detonation flame arrester.
12.1.3 Size of the inlet and outlet.
12.1.4 Type of device (Type I or II).
12.1.5 Direction of flow through the detonation flame arrester.
12.1.6 Test laboratory and report number.
12.1.7 Lowest MESG of gases that the detonation flame arrester is suitable for.
12.1.8 ASTM designation of this standard.
12.1.9 Ambient air operating temperature range.
12.1.10 Maximum operating pressure.
13. Quality Assurance
13.1 Detonation flame arresters shall be designed, manufactured and tested in a manner that ensures they meet the characteristics of the unit tested in accordance with this standard.
13.2 The detonation flame arrester manufacturer shall maintain the quality of the arresters that are designed, tested and marked in accordance with this standard. At no time shall a detonation flame arrester be sold with this standard designation that does not meet the requirements herein.
14. Test Procedures for Detonation Arresters
14.1 Media/Air Mixtures
14.1.1 For vapors from flammable or combustible liquids with a MESG greater than or equal to 0.9 mm, technical grade hexane or gasoline vapors shall be used for all tests in this section except technical grade propane may be used for the deflagration/detonation tests in section 14.3. For vapors with a MESG less than 0.9 mm, the specific vapor (or alternatively, a media with a MESG less than or equal to the MESG of the vapor) must be used as the test medium in all Section 14 tests.
14.1.2 Hexane, propane, gasoline and other test vapors shall be mixed with air to form the most easily ignitable mixture. 5
14.2 Endurance Burn Test Procedure
14.2.1 An endurance burning test shall be carried out as follows:
126.96.36.199 The test rig shall consist of an apparatus producing an explosive mixture, a small tank with a diaphragm, a prototype of the detonation flame arrester and a firing source in close proximity to the test device (see Figure 1). The detonation flame arrester shall be installed so that the mixture emission is vertically upwards, or installed in the position for which it is designed and which will cause the most severe heating of the device under the prescribed endurance burn conditions. In this position the mixture shall be ignited.
188.8.131.52 Endurance burn test shall start by using the most easily ignitable test vapor/air mixture with the aid of a pilot flame or a spark igniter at the outlet. The flammable mixture may be reignited as necessary in the course of the endurance burn.
184.108.40.206 Temperature measurement will be performed on the surface of the arrester element half way between the center and its edge.
220.127.116.11 By varying the proportions of the flammable mixture and the flow rate, the detonation flame arrester shall be heated by a stable flame on the surface of the arrester until the highest obtainable temperature is reached on the ignited side or until the temperature on the side which was not ignited (protected side) rises 100 °C.
18.104.22.168 The flammable mixture proportions will then be varied again until the conditions which result in the highest temperature on the protected side are achieved. This temperature shall be maintained for a period of ten minutes, after which the flow shall be stopped and the conditions observed. The highest attainable temperature is considered to have been reached when any subsequent rise of temperature does not exceed 0.5 °C per minute over a ten minute period.
22.214.171.124 If difficulty arises in establishing the highest attainable temperature on the protected side, the following criteria shall apply. When the increase in temperature on the protected side occurs so slowly that its temperature does not rise 100 °C, the conditions which produced the highest temperature on the ignited side of the arrester will be maintained for two hours. For the condition in which the temperature on the protected side continues to rise at a rate in excess of 0.5 °C per minute for a 10 minute period, endurance burning shall be continued, using the most severe conditions of flammable mixtures and flow rate, for a period of two hours. In either of these cases, at the end of the two hour period, the flow shall be stopped and the conditions observed. The two hour interval shall be measured commencing with the setting of the conditions which produced the most severe conditions of mixture and flow rate. For Type I detonation flame arresters, flame passage shall not occur during this test. For Type II detonation flame arresters, the maximum temperature obtained, and the time elapsed from the time when the most severe conditions are set to when flame passage occurs, shall be recorded. However, for Type II detonation flame arresters the test may be terminated 15 minutes after setting the most severe conditions on the protected side.
14.3 Deflagration/Detonation Test Procedure
14.3.1 A detonation flame arrester shall be installed at one end of a pipe of the same diameter as the inlet of the detonation flame arrester (see Figure 2). The length and configuration of the test pipe shall develop a stable detonation 6 at the device and shall be capable, by change in its length or configuration, of developing deflagrations and unstable (overdriven) detonations as measured on the side of the pipe where ignition occurs (run-up side). For deflagration testing, two test piping arrangements shall be used on the outlet side of the detonation flame arrester (the side which is not ignited). In both of the following end arrangements, the outlet side pipe diameter shall be equal to that on the run-up side. In one arrangement, the outlet side pipe shall be at least 10 pipe diameters long with a plastic bag over the free end. (Alternate end of pipe closures are also acceptable provided they easily give way during the course of the test, and the closure allows the required gas concentration to be maintained throughout the test piping arrangement.) In the other arrangement the outlet side pipe shall be fitted with a restriction located 0.6 meters from the outlet side arrester flange. The size of the restriction for each nominal size detonation flame arrester shall be as follows:
|Nominal pipe diameter (inches)||Restriction diameter (inches)|
14.3.2 Flame speeds shall be measured by optical devices capable of providing accuracy of ±5%. These devices shall be situated no more than a distance equal to 3% of the length of the run-up pipe apart with one device no more than 8 inches from the end of the test pipe to which the detonation flame arrester is attached. In addition, each outlet arrangement described in paragraph 14.3.1 shall be fitted with an optical device located no more than 8 inches from the detonation flame arrester outlet. 7
14.3.3 Explosion pressures within the pipe shall be measured by a high frequency transducer situated in the test pipe no more than 8 inches from the run-up side of the housing of the detonation flame arrester.
14.3.4 Using the first end arrangement (10 pipe diameter outlet) described in paragraph 14.3.1, a series of tests shall be conducted to determine the test pipe length and configuration that results in the maximum unstable (overdriven) detonation having the maximum measured flame speed at the detonation flame arrester. (These tests may also be carried out using a single length of pipe with igniters spaced at varying distances from the arrester.) The flame speeds, explosion pressures and test pipe configurations shall be recorded for each of these tests. The piping configuration that resulted in the highest recorded unstable (overdriven) detonation flame speed shall be used, and the device shall be subjected to at least four additional unstable (overdriven) detonations. In the course of testing, the device shall also demonstrate its ability to withstand five stable detonations, five deflagrations (as determined by flame speed) where Δ P/Po was less than 1 and five deflagrations (as determined by flame speed) where Δ P/Po was greater than 1 but less than 10. Initiation of deflagrations shall be at several locations to generate a range for Δ P/Po. Deflagration tests using the restricted outlet arrangement described in paragraph 14.3.1 shall then be conducted. In these tests the device shall demonstrate its ability to stop five deflagrations (as determined by flame speed) generated by the same configurations which resulted in Δ P/Po being less than 1 during the deflagration tests which were conducted without the restricted end arrangements, and five deflagrations (as determined by flame speed) generated by the same configurations which resulted in Δ P/Po being greater than 1 but less than 10 during the deflagration tests which were conducted without the restricted end arrangements. No evidence of flame passage shall occur during these tests. The flame speeds and explosion pressures for each of these tests shall be recorded.
14.3.5 A device that successfully passes the tests of 14.3.4 shall be considered to be directional (suitable for arresting a detonation advancing only from the direction as tested) except;
126.96.36.199 A device may be tested according to 14.3.4 for detonations approaching from either direction, or
188.8.131.52 The design of the device is symmetrical where each end may be considered to be identical when approached by a detonation from either direction.
1 Available from the American Society for Testing and Materials (ASTM), 100 Barr Harbor Dr., West Conshohocken, PA 19428-2959.
2 Available from the American Society of Mechanical Engineers International, Three Park Avenue, New York, NY 10016-5990.
3 Available from the International Maritime Organization, 4 Albert Embankment, London SE1 7SR, England.
4 Available from the International Electrotechnical Commission, 1 rue de Varembe, Geneva, Switzerland.
5 See IEC Publication 79-1.
6 Some data are available for the estimation of flame speeds in horizontal pipes without detonation flame arresters. Some data indicate that the presence of small obstacles, fittings or bends in the test pipe can accelerate the flame speeds appreciably.
7 Other pressure and/or flame speed measuring techniques may be used if effective.
|Inflammable gas or vapour||Experimental maximum safe gap|
|Blast furnace gas||1.193||0.047|
|Coal gas (H2 57%)||0.482||0.019|
|Blue water gas (H2 53% CO 47%)||0.203||0.008|
|Ammonia||1 3.33||1 0.133|