Subsection 4.4.1. - Application
This Section applies to piping systems consisting of pipe, tubing, flanges, bolting, gaskets, valves, fittings, flexible connectors, pressure fit devices such as expansion joints and other components such as pumps, strainers, filters, meters, etc. Any piping system is susceptible to leakage or spill of liquids. Because of the additional fire hazard in piping systems handling flammable and combustible liquids, these systems must be able to withstand the intense heat generated by fire for reasonable periods of time while emergency shutdown procedures are implemented and fire fighting measures begin. The failure of pipes, valves, fittings and gaskets during the fire exposure, can turn a small fire into a large catastrophic fire condition.
This Section does not apply to:
All elements of a piping system handling flammable and combustible liquids must be capable of withstanding the maximum design pressures and temperatures of the system. The various components of a piping system must be able to withstand internal stress, thermal shock or rupture by mechanical failure and must have a melting point above 540oC. Thus the use of low melting materials such as plastic, brass, bronze, copper or aluminum are prohibited in aboveground installations. The use of cast iron is also prohibited because of its brittleness. Under fire conditions the cast iron valve, fitting or flange could fail from the stresses caused by thermal expansion of the pipe system or from the thermal shock of being suddenly cooled by a fire hose stream. Steel is the only practical material that is capable of withstanding the stresses and temperatures created by the fire for a period of time.
Prescriptive requirements are given for steel pipe operating at pressures up to a maximum of 875 kPa. Where the pressures exceed 875 kPa, the pipe and fittings shall be carbon steel or other specified material with welded or flanged joints as per ANSI/ASME B31.3, "Chemical Plant and Petroleum Refinery Piping".
Where there are problems concerning corrosion, contamination, sanitation or product purity, other materials may be used subject to approval by the Chief Fire Official. These components may be approved where they are protected by thermal insulation with a steel shield for fire hose stream protection.
Underground piping that would not be subject to fire exposure can be made from materials that conform to ULC standards.
As the flammable or combustible liquids represent a sizable fire load, to minimize these contents from contributing to a spill, this Subsection requires all tank valves to be of steel construction. The general practice is to use a valve with a rising stem so that it clearly indicates whether it is open or closed. These valves should be normally closed except during tank filling, emptying or blending operation.
In Clause 4.4.2.1.(2)(a), cast iron is a material that is intended to be prohibited due to its susceptibility to failure by internal stress or rupture, either mechanical or thermal. In Clause (2)(b), "low melting point" is intended to exclude materials such as aluminum, copper and brass. Materials with a melting point below 1100°C should be considered low melting.
Wherever a piping system is exposed to a corrosive environment, it must be protected against corrosion to prevent premature failure.
Underground steel piping, valves and fittings are subjected to considerable corrosion due to direct contact with the backfill material. This material can be moist for lengthy periods as a result of rainfall or from melting snow. This code prescribes corrosion protection in conformance with CAN/ULC-S603.1 or by good engineering practice such as described in PACE Report No. 87-1 published by the Canadian Petroleum Products Institute.
To assist firefighters arriving at the scene of a fire involving a piping system, identification of piping handling flammable and combustible liquids is required. This can be accomplished by appropriate lettering, tags, strips or banding but in no event should the system be painted red. The colour red to a firefighter would signify fire protection equipment such as sprinkler, inert gas or foam extinguishing systems.
Plans showing the piping systems for flammable and combustible liquids including storage tanks and associated pumping facilities must be available to the fire department upon request. Copies of these piping plans are to be kept at two separate locations so that should the set of plans at the plant be lost or destroyed for whatever reason, another set is available from another location.
At transfer points in piping systems handling flammable or combustible liquids, the piping must be clearly identified so that employees are less likely to direct the liquid flow to a wrong destination with possible disastrous consequences. The code prescribes two standards, either of which can be used for such identification.
All piping joints used to connect the various components of the system must be liquid tight and capable of handling the design pressure of the piping system without leaking. Piping joints should be either screwed, flanged or welded.
Welded piping provides excellent integrity under fire exposure conditions but has the disadvantage of requiring hot work to both dismantle and reconnect the piping. Pumps or other equipment that require periodic removal for maintenance, should be provided with flanged joints to facilitate this activity. Since both cutting and welding creates an ignition source, this should be avoided in piping systems handling flammable and/or combustible liquids.
The use of victaulic joints and improper gaskets on flammable or combustible liquid piping will readily fail on fire exposure and should not be used.
The bolts used in a flanged joint must be steel and not a low melting material like brass or bronze to maintain mechanical strength under fire exposure. Bolts must conform to ASTM Standard A193/A 193M. The proper installation of bolts or studs is important to attain the required tightness in the flanged joint. The bolt or stud must be long enough and a stud so positioned that a nut can be fully engaged with 1 1/2 threads protruding beyond the nut face. The last thread on the bolt or stud is chamfered to facilitate thread engagement and therefore does not provide the full thread strength.
Testing of all new, altered, repaired or suspected leaking piping systems must be done before the system is placed in service. Tests are not an absolute guarantee that the system is leak free or that it will remain that way. It is a method to help ensure that the system will perform as desired under normal circumstances and in predictable emergency situations.
Exposed piping systems which are in service should receive routine periodic visual inspection, looking for any signs of leaks, as required in Article 4.4.11.5. Leak testing may be performed by pneumatic testing to 350 kPa or 150 % of the maximum system design pressure, whichever is greatest, except pressures above 700 kPa are not permitted unless the system has been designed for this pressure. A piping system shall be considered to be leaking when the test shows a pressure drop within a 2 hour period after steady temperature conditions have been reached and the pressure source has been removed. The piping, including all joints, should be coated with soap solution to facilitate finding any leaks.
Class I liquids should not be used for hydraulic testing unless the piping system normally contains only a Class I liquid. The test pressure is not to exceed the maximum operating pressure of the piping system.
Where pneumatic testing is to be performed on piping, it must be completely purged of liquid and vapours, unless an inert gas is used for the test. The use of air without purging the system could result in an explosive vapour/air mixture in the pipe. If during the test, a leak is detected, the piping system shall be either repaired or replaced and re-tested until tested satisfactorily.
A record of all piping system pressure tests must be retained for examination by the Chief Fire Official.
Although Article 4.4.6.3. references Subsection 4.1.6. for the removal of escaped liquids, Article 4.1.6.3. is the specific reference to ensure clean up of any escaped liquid.
The location of piping carrying flammable or combustible liquids is important since these liquids, if spilled or leaked, would constitute a severe fire hazard. This is particularly true where such piping is provided inside a building. The location of piping should be such that a spill or leak from the piping would not endanger a building or its occupants. This Subsection has requirements pertaining to piping systems on building roofs or located on outside building walls.
All aboveground piping should be properly supported according to good engineering practices to prevent damage from vibration and stress. Where vehicular traffic can be present, piping systems must be provided with approved protective guarding devices. Where there is overhead piping crossing private roads, railway sidings or highways, a warning sign is required indicating the presence of this hazardous piping and showing the clearances that are provided.
and combustible liquid piping inside buildings should be above grade so that any leaks are readily apparent and repairs can be easily undertaken. If overhead, the piping should be properly supported close to the ceiling, beams or wall and at least 1.8 metres above the floor to provide sufficient clearance from mechanical damage. Greater clearances are required in areas where fork lift trucks or other mechanical equipment are present. For pipes having a nominal diameter of 50 mm or less, it is a good practice to space hangers not more than 3.5 metres apart.
Underground piping located under roadways or railroad tracks is subject to vibration and ground settlement caused by the movement of vehicles or rail cars and locomotives. Vibration and ground settlement can cause underground piping to fail and leak with the possibility that the leak may not be detected for a period of time. In order to prevent considerable environmental damage and possible fire, the underground piping must be protected. The code requires conformance with regulations of Transport Canada for underground piping under or adjacent to railroad tracks.
Protection against vibration or settlement should be provided before underground piping is installed under any building or structural foundation. The code contains prescriptive requirements for the support and backfill of underground piping. Piping for flammable and combustible liquids should be aboveground when entering a building. This piping should be provided with an inside and outside shut-off valve, preferably through a pipe sleeve so that undue stress on the piping is not caused by frost movement or vibration.
Service tunnels that are used for pedestrian traffic should not contain piping for flammable or combustible liquids. The possibility of a leak producing a flammable vapour may create health or life safety hazards.
Indoor flammable or combustible liquid piping should not be installed under a combustible floor due to fire spread and fire fighting difficulties.
Indoor trenches containing piping for flammable and combustible liquids must have a trapped drainage system conforming to Subsection 4.1.6. The trench would contain any leaks in the area because it is lower. The heavier-than-air vapours that are released would stay in the trench and be carried to other building areas. Positive ventilation to the outdoors must be provided if the trench piping contains Class I liquids. Alternatively, the ventilation must be designed to prevent the development of an explosive vapour/air mixture.
The intent of Article 4.4.7.8. is to ensure that the trenches are not covered with combustible material that could be contaminated with flammable liquid and susceptible to easy ignition and/or fire spread. The concealed pipe could develop a leak that could go unnoticed for some period of time. Therefore, piping in trenches must not be covered with combustible material.
Provision for thermal expansion and contraction caused by variations in liquid temperature, air temperature fluctuations or by direct sunlight exposure must be incorporated into the design of aboveground flammable and combustible liquid piping systems. The required flexibility in the aboveground piping may be achieved by a variety of methods including the use of expansion loops, changes in piping direction, telescoping expansion connectors, expansion bellows or flexible hose connectors.
Subsection 4.4.2. indicates the importance of the materials used for valves in the piping systems. These valves must be able to withstand the maximum operating pressures and temperatures of the piping system such as the pressure that could be developed if a pump in the system is run against a closed valve. In order to isolate tanks or portions of the system in fire situations, steel shut-off valves must be placed in strategic locations in the piping system. Steel shut-off valves are required in the following locations:
Where quality and product purity are required, stainless steel and monel valves are permitted. An example of such an activity would be the handling of distilled beverage alcohol (ethyl alcohol) in Section 4.9.
All air operated valves (control valves, diaphragm valves), pumps or equipment must be designed and maintained in order to prevent the leakage of flammable or combustible liquid into the air line. Any leakage of flammable or combustible liquid into the air line could create a serious fire hazard.
Shut-off or isolating valves should clearly indicate whether the valves are closed or open or somewhere in-between. One valve that is frequently utilized is the outside stem and yoke valve which, when fully closed, very little of the valve stem can be seen above the operating wheel. The valve stem protrudes several centimetres above the valve operating wheel when the valve is in the fully open position. Ball valves and plug valves clearly show whether the valve is open or closed by the position of the valve operating handle. If the handle is parallel with the piping, the valve is fully open. The valve is fully closed when the operating handle is at a right angle to the piping.
Cast iron meters would quickly fail due to the brittle nature of cast iron. This Subsection requires such meters to be provided with steel valves on either side of the meter. In order to minimize the amount of fuel release due to meter failure in a fire, these valves should be placed close to the meter to provide isolation. The use of isolation valves permits the removal of the meters from the piping system for maintenance and recalibration with a minimum of liquid spill.
In order to assist the firefighter in an emergency, valves in flammable and combustible liquid piping systems must be clearly identified or labeled to distinguish them from valves in other nearby piping systems.
An amendment in Article 4.4.8.1. provides a means by which existing valves that are not in conformance with one of the referenced standards but are still functional and structurally sound and have many more years of useful life may continue to be used. The concern about valves relate to valves made from materials that are subject to failure from mechanical and/or thermal shocks or high temperature, such as cast iron or low melting or combustible material. Thus existing valves that are not leaking and not made of cast iron or low melting materials, such as aluminum or plastic, may continue to be used until they are replaced or begin to leak. This will not force owners to undergo unnecessary expense to determine if all of their valves comply with the standards, while still requiring replacement of the valves that are a real concern.
There are processes where the flammable or combustible liquids are heated in order for the reaction or process to take place. Such processes must be designed, installed and maintained to prevent a hot pipe surface from becoming a source of ignition and to prevent the overheating of the liquids. Heating of a combustible liquid to or above its flash point, changes its classification to a flammable liquid. This significantly increases the fire hazard if the liquid is leaked or spilled. When such liquids are heated above their autoignition temperature, any leak may result in immediate ignition on contact with air.
A heat exchange system with steam or other liquids (e.g. hot water, heat transfer agent) may be used to heat the flammable and combustible liquids in a piping system. In order to prevent flammable and combustible liquids from exceeding the design operating temperatures and pressures of the piping system, heat exchange systems must possess good controls on the heating medium.
Hot pipes are a potential ignition source for flammable vapours. Hot piping is required to be enclosed in insulation as per Article 6.2.9.4. of the Building Code. This insulation will protect against ignition, conserve energy and protect worker safety.
Piping may be heated by passing an alternating current through the pipe. These thermal electrical conduction heating systems must be installed and tested as complete units in accordance with the Electrical Safety Code (e.g. Rule 62-404) and the following:
Open flames are not allowed as a heat source for heating piping since the flame is an excellent ignition source if there are flammable vapours present.
The three methods that are acceptable for the transfer of flammable and combustible liquids are pumping, hydraulic pressuring and inert gas pressuring.
The use of pumps is the most common method. Pumps are subject to wear and may leak. Therefore, their placement is important. Pumps located outdoors must be located a minimum of 1.5 metres from building openings so that vapours are less likely to enter the building and 3 metres from property lines to provide fire fighting access. Indoor pumps must be placed in a fire separated area in conformance with Subsection 4.2.9.
Clearly identified switches at or near a pump and a switch at a remote location are required to ensure that power can be shut off in the event of an emergency. The duplicate control switch at a remote accessible location is required in case a fire or a spill of flammable liquid at the pump makes it unsafe to shut off the flow of liquid at the pump location. The switches at the pump and at the remote location should be readily accessible and not blocked by the storage of other materials. Minimizing the amount of leakage and potential fire loss requires quick access to the shut-off switch of the pump should the pump develop a leak. The remote switch location could be situated in a motor control room or electrical switchgear room as long as the switches and breakers are clearly labeled.
Positive displacement pumps, pumps that can develop high discharge pressures, can be used in piping systems. In order to protect the piping system from excessive pressure it is good practice to install a pressure relief valve. The valve can be connected to the discharge piping of the positive displacement pump and discharge back into the suction side of the pump.
Hydraulic pressure transfer of flammable or combustible liquids that are miscible in water is not permitted. Pressure vessels used for hydraulic transfer systems must be constructed, installed and tested in accordance with Subsection 4.3.1. In order to prevent the failure of the piping or tanks, the operating pressure of the hydraulic transfer system must not exceed the design pressure of the piping system or tanks connected to it. The water pressure is only to be on the flammable or combustible liquid piping system when product transfer is taking place.
During the operation of a hydraulic transferring system, the water pressure must not be allowed to fluctuate widely since this will cause unnecessary stress on the flammable or combustible liquid piping system. This can be accomplished by controlling the operating pressure by a constant-level float valve or by a pressure regulating valve on the water piping. To prevent contamination of the water supply, a check valve must be installed and maintained on the water piping to prevent a backflow of flammable or combustible liquids into the water lines.
Another method of flammable and combustible liquid transfer is by applying pressure to the liquid with an inert gas such as nitrogen or carbon dioxide. A gas regulator should control the operating pressure of the inert gas transfer system. It should be set at the minimum pressure needed to force the liquid through the piping system at the desired flow rate. The pressure must not exceed the design pressure of the connected piping system or tanks to prevent the failure of the system. Inert gas transfer systems must be constructed, installed and tested in accordance with Subsection 4.3.1. Downstream of the inert gas regulator, a pressure relief valve is installed at a pressure slightly higher than required to transfer the flammable and combustible liquid. In the event of a fire or a leak, provision must be made to safely release the line pressure in the piping system to stop the flow. This must occur automatically on fire detection. These valves are to be clearly identified or labeled and readily accessible.
Never use compressed air to transfer flammable or combustible liquids due to the fire and explosion risks this creates.
Instruction and training in normal day-to-day operations in the transfer, use and handling of flammable and combustible liquids must be given to all personnel involved in these activities. Emergency procedures in the event of fire or spills should also be provided. Personnel should be trained in how to extinguish at least a small spill fire of flammable or combustible liquids. Written copies of these operating and emergency procedures must be kept readily available in the operating area. The procedures must be consistent with available plant equipment and personnel. The written emergency procedures should deal with how to respond to fire, spills of flammable or combustible liquids or other emergencies. This procedure or plan shall include the following concerning a fire emergency:
In addition, the following must be included when a spill of flammable or combustible liquid is involved:
An excellent way to indicate the location of emergency of emergency shutdown valves or switches is the use of drawings or marked up plans. These drawings should be included as a part of the written procedures. The local fire department and the plant personnel who will be involved with the implementation should be consulted during the development stage of these written procedures. Periodic reviews of the procedures will ensure that they are up to date and include a current list of personnel and telephone numbers. The procedures should be reviewed at least annually.
In order to assist plant personnel and the local fire department, signs must be posted in conspicuous locations to clearly indicate where emergency shut-off valves, pump shutdown switches and fire equipment operating valves are located. Both operating and maintenance personnel should be trained and familiar with these valve and switch locations. They should also be knowledgeable in the plant code used to identify flammable and combustible liquid piping.
A visual routine inspection procedure should be performed at least once a shift on all flammable and combustible liquid piping systems and storage tanks to report any abnormal conditions such as leaks, excessive vibration, instrument readings not in the normal operating range, etc.
Safety shut-off off valves, shutdown switches and other safety devices must be frequently inspected to ensure they will operate as designed. These safety devices are very important for the overall protection of the personnel and plant. It is recommended that these devices be inspected at least once a month and tested annually or as suggested in the operating instructions that accompany these devices. Records should be kept showing the date and results of the inspections and/or tests.
Due to the inherent hazard associated with flammable and combustible liquids, any piping containing these liquids must be drained and purged before the start of any maintenance work. Equipment used for handling flammable or combustible liquids should be removed and taken to the maintenance area to carry out required repairs. All valves or switches for pumps on piping systems that are not to be operated due to the maintenance work, are to be tagged and locked out. The requirement of this Article does not apply to routine maintenance such as lubrication, painting, insulating and tightening.
|
||||||||||||||||||
