260 R.I. Code R. 260-RICR-30-10-2.6

Current through December 3, 2024

Section 260-RICR-30-10-2.6 - EXISTING INSTALLATION: POWER BOILERS

2.6.1EBO-1 Age Limit of Existing Boilers

A. The age limit of any boiler of nonstandard construction, installed prior to the date the Act became effective, shall be 30 years except that, a boiler having other than lap-riveted longitudinal joint, after a thorough internal and external inspection, and when required by the inspector, a hydrostatic pressure test of 1-1 /2 times the allowable working pressure held for a period of at least 30 minutes during which no distress or leakage develops, may be continued in operation at the working pressure determined by § 2.6.3 of this Part.. The age limit of any nonstandard boiler having lap-riveted longitudinal joints and operating at a pressure in excess of 50 psi shall be 20 years. This type of boiler, when removed from an existing setting, shall not be reinstalled for a pressure in excess of 15 psi. A reasonable time for replacement, not to exceed one year, may be given at the discretion of the Chief Inspector.

B. The age limit of boilers of standard construction installed prior to the date this law became effective shall be dependent on thorough internal and external inspection and where required by the inspector, a hydrostatic pressure test not exceeding 1-1 /2 times the allowable working pressure. If the boiler, under these test conditions, exhibits no distress or leakage, it may be continued in operation at the working pressure determined by § 2.6.2 of this Part.

C. The shell or drum of a boiler in which a lap seam crack develops along a longitudinal lap-riveted joint shall be condemned. A lap seam crack is a crack found in lap seams extending parallel to the longitudinal joint and located either between or adjacent to rivet holes.

2.6.2EBO-2 Maximum Allowable Working Pressure for Standard Boiler

The maximum allowable working pressure for standard boilers shall be determined in accordance with the applicable provisions of the edition of the ASME Code under which they were constructed and stamped.

2.6.3EBO-3 Maximum Allowable Working Pressure for Nonstandard Boilers

A. The maximum allowable working pressure for boilers fabricated by riveting shall be determined by the applicable rules of the 1971 Edition of Section I of the ASME Code.

B. The lowest factor of safety permissible on existing installations shall be 5.0, except for horizontal-return- tubular boilers having continuous longitudinal lap seams more than 12 ft. in length, the factor of safety shall be 8. When this latter type of boilers is removed from its existing setting, it shall not be reinstalled for pressures in excess of 15 psi.

C. The maximum allowable working pressure for boilers of welded construction in service may not exceed that allowable in Section I of the 2017 ASME Code, incorporated above, for new boilers of the same construction.

D. The maximum allowable working pressure on the shell of a boiler or drum shall be determined by the strength of the weakest course computed from the thickness of the plate, the tensile strength of the plate, the efficiency of the longitudinal joint, the inside diameter of the course, and the factor of safety allowed by these rules in accordance with the following formula:

1. TStE = maximum allowable working pressure, psi RFS where:

a. TS = specified minimum tensile strength of shell plate material. When the tensile strength of steel or wrought-iron shell plate is not known, it shall be taken as 55,000 psi for steel and 45,000 psi for wrought-iron.

b. t = minimum thickness of shell plate in weakest course, in inches.

c. E = efficiency of longitudinal joint, method of determining which is given in Paragraph PG-27 of Section I of the ASME Code.

d. R = inside radius of the weakest course of the shell or drum, in inches.

e. FS = factor of safety which shall be at least 5.0.

E. The inspector may increase the factor of safety, if the condition and safety of the boiler warrants it.

2.6.4EBO-4 Cast Iron Headers and Mud Drums

The maximum allowable working pressure on a water tube boiler, the tubes of which are secured to cast iron or malleable iron headers, or which have cast iron mud drums, shall not exceed 160 psi.

2.6.5EBO-5 Pressure on Cast Iron Boilers

The maximum allowable working pressure for any cast iron boiler, except hot water boilers, shall be 15 psi. See §§ 2.7.1, 2.7.2, and 2.7.4 of this Part.

2.6.6EBO-6 Safety Valves

A. The use of weighted-lever safety valves or safety valves having either the seat or disc of cast iron are prohibited; valves of this type of construction shall be replaced by direct spring loaded, pop-type valves that conform to the requirements of 2017 ASME Code, Section I.

B. Each boiler shall have at least one ASME/NB Stamped and certified safety valve, and if it has more than 500 sq. ft. of water-heating surface, or an electric power input of more than 1100 KW, it shall have two or more safety valves of the same type.

C. The valve or valves shall be connected to the boiler, independent of any other steam connection; and attached as close as possible to the boiler, without unnecessary intervening pipe or fittings. Where alteration is required to conform to this requirement, owners or users shall be allowed reasonable time in which to complete the work as permitted by the Chief Inspector.

D. No valves of any description shall be placed between the safety valve and the boiler nor on the escape pipe, if used. When an escape pipe is used, it shall be at least the full size of the safety valve discharge and fitted with an open drain to prevent water lodging in the upper part of the safety valve or in the escape pipe. When an elbow is placed on a safety valve escape pipe, it shall be located close to the safety valve outlet or the escape pipe shall be anchored and supported securely. All safety discharges shall be so located or piped as to be carried clear from walkways or platforms.

E. The safety valve capacity of each boiler shall be such that the safety valve or valves will discharge all the steam that can be generated by the boiler without allowing the pressure to rise more than six percent (6%) above the highest pressure to which any valve is set, and in no case to more than six percent (6%) above the maximum allowing working pressure.

F. One or more safety valves on every boiler shall be set at or below the maximum allowable working pressure. The remaining valves may be set within a range of three percent (3%) above the maximum allowable working pressure, but the range of setting of all the safety valves on a boiler shall not exceed ten percent (10%) of the highest pressure to which any valve is set.

G. When boilers of different maximum allowable working pressures with minimum safety valve settings varying more than six percent are so connected that steam can flow toward the lower pressure units, the latter shall be protected by additional safety valve capacity, if necessary, on the lower pressure side of the system. The additional safety valve capacity shall be based upon the maximum amount of steam which can flow into the lower pressure system.

H. In those cases where the boiler is supplied with feed-water directly from water mains without the use of feeding apparatus (not to include return traps), no safety valve shall be set at a pressure greater than 94 percent of the lowest pressure obtained in the supply main feeding the boiler.

I. The relieving capacity of the safety valves on any boiler shall be checked by one of the three following methods and, if found to be insufficient, additional valves shall be provided:

1. by making an accumulation test, which consists of shutting off all other steam discharge outlets from the boiler and forcing the fires to the maximum. The safety valve capacity shall be sufficient to prevent a rise of pressure in excess of six percent (6%) of the maximum allowable working pressure. This method should not be used on a boiler with a super-heater or re-heater;

2. by measuring the maximum amount of fuel that can be burned and computing the corresponding evaporative capacity (steam generating capacity) upon the basis of the heating value of this fuel. These computations shall be made as outlined in the Appendix of the 2017 ASME Code, Section I;

3. by measuring the maximum amount of feed-water that can be evaporated;

J. When either of the methods outlined in § 2.6.6(1)(2) and (3) of this Part is employed, the sum of the safety valve capacities shall be equal to or greater than the maximum evaporative capacity (maximum steam generating capacity) of the boiler.

2.6.7EBO-7 Boiler Feeding

A. Each boiler shall have a feed supply which will permit it to be fed at any time while under pressure.

B. A boiler having more than 500 sq. ft. of water heating surface shall have at least two suitable means of feeding, at least one of which shall be a feed pump. A source of feed at a pressure 6 percent greater than the set pressure of the safety valve with the highest setting may be considered one of the means. Boilers fired by gaseous, liquid, or solid fuel in suspension may be equipped with a single means of feeding water provided means are furnished for the shutoff of heat input prior to the water level reaching the lowest safe level.

C. The feed-water shall be introduced into a boiler in such a manner that the water will not be discharged directly against surfaces exposed to gases of high temperature or to direct radiation from the fire. For pressures of 400 psi or over, the feed-water inlet through the drum shall be fitted with shields, sleeves, or other suitable means to reduce the effects of temperature differentials in the shell or head.

D. The feed piping to the boiler shall be provided with a check valve near the boiler and a valve or cock between the check valve and the boiler. When two or more boilers are fed from a common source, there shall also be a valve on the branch to each boiler between the check valve and the source of supply. Whenever a globe valve is used on feed piping, the inlet shall be under the disc of the valve.

E. In all cases where returns are fed back to the boiler by gravity, there shall be a check valve and stop valve in each return line, the stop valve to be placed between the boiler and the check valve, and both shall be located as close to the boiler as is practicable. It is recommended that no stop valves be placed in the supply and return pipe connections of a single boiler installation.

F. Where de-aerating heaters are not employed, it is recommended that the temperature of the feed-water be not less than 120 degrees Fahrenheit to avoid the possibility of setting up localized stress. Where de-aerating heaters are employed, it is recommended that the minimum feed-water temperature be not less than 215 degrees Fahrenheit so that dissolved gases may be thoroughly released.

2.6.8EBO-8 Water Level Indicators

A. Each boiler, except forced-flow steam generators with no fixed steam and waterline, and high-temperature water boilers of the forced circulation type that have no steam and water-line, shall have at least one water gage glass. Boilers operated at pressures over 400 psi shall be provided with two water gage glasses which may be connected to a single water column or connected directly to the drum.

B. Two independent remote level indicators may be provided instead of one of the two required gage glasses for boiler drum water level indication in the case of power boilers with all drum safety valves set at or above 900 psi. When both remote level indicators are in reliable operation, the remaining gage glass may be shut off, but shall be maintained in serviceable condition.

C. When the direct reading of gage glass water level is not readily visible to the operator in his working area, two dependable indirect indications shall be provided, either by transmission of the gage glass image or by remote indicators.

D. The lowest visible part of the water gage glass shall be at least 2 in. above the lowest permissible water level, at which level there will be no danger of overheating any part of the boiler when in operation at that level. When remote level indication is provided for the operator in lieu of the gage glass, the same minimum level reference shall be clearly marked.

E. Connections from the boiler to the remote level indicator shall be at least 3/4-inch pipe size to and including the isolation valve and from there to the remote level indicator at least 1/2 in. O.D. tubing. These connections shall be completely independent of other connections for any function other than water level indication. For pressures of 400 psi or over, lower connections to drums shall be provided with shields, sleeves, or other suitable means to reduce temperature differentials in the shells or heads.

F. Boilers of the horizontal fire-tube type shall be so set that when the water is at the lowest reading in the water gage glass there shall be at least 3 in. of water over the highest point of the tubes, flues, or crown sheets.

G. Boilers of locomotives type shall have at least one water glass provided with top and bottom shutoff cocks and lamp, and two gage cocks for boilers 36 in. in diameter and under, and three gage cocks for boilers over 36 in. in diameter.

H. The lowest gage cock and the lowest reading of water glass shall not be less than 2 in. above the highest point of crown sheet on boilers 36 in. in diameter and under, nor less than 3 in. for boilers over 36 in. in diameter. These are minimum dimensions, and on larger locomotives and those operating on steep grades, the height should be increased, if necessary, to compensate for change of water level on descending grades.

I. The bottom mounting for water glass and for water column if used must extend not less than 1-1 /2 in. inside the boiler and beyond any obstacle immediately above it, and the passage therein must be straight and horizontal.

J. Tubular water glasses must be equipped with a protecting shield.

K. All connections on the gage glass shall be not less than 1/2 in. pipe size. Each water-gage glass shall be fitted with a drain cock or valve having an unrestricted drain opening of not less than 1/4 in. diameter to facilitate cleaning. When the boiler operating pressure exceeds 100 psi the glass shall be furnished with a connection to install a valved drain to the ash pit or other safe discharge point.

L. Each water gage glass shall be equipped with a top and a bottom shutoff valve of such through-flow construction as to prevent stoppage by deposits of sediments. If the lowest valve is more than 7 ft. above the floor or platform from which it is operated, the operating mechanism shall indicate by its position whether the valve is open or closed. The pressure-temperature rating shall be at least equal to that of the lowest set pressure of any safety valve on the boiler drum and the corresponding saturated-steam temperature.

M. Straight-run globe valves, shall not be used on such connection.

N. Automatic shutoff valves, if permitted to be used, shall conform to the requirements of Section I of the 2017 ASME Code.

2.6.9EBO-9 Water Columns

A. The water column shall be so mounted that it will maintain its correct position relative to the normal waterline under operating conditions.

B. The minimum size of pipes connecting the water column to a boiler shall be 1 in. For pressures of 400 psi or over, lower water column connections to drums shall be provided with shields, sleeves, or other suitable means to reduce the effect of temperature differentials in the shells or heads. Water glass fittings or gage cocks may be connected directly to the boiler.

C. The steam and water connections to a water column or a water gage glass shall be such that they are readily accessible for internal inspection and cleaning. Some acceptable methods of meeting this requirement are by providing a cross or fitting with a back outlet at each right-angle turn to permit inspection and cleaning in both directions, or by using pipe bends or fittings of a type which does not leave an internal shoulder or pocket in the pipe connection and with a radius of curvature which will permit the passage of a rotary cleaner.

D. Screwed plug closures using threaded connections as allowed by Section I of the 2017 ASME Code are acceptable means of access for this inspection and cleaning. For boilers with all drum safety valves set at or above 400 psi, socket-welded plugs may be used for this purpose in lieu of screwed plugs. The water column shall be fitted with a connection for a drain cock or drain valve to install a pipe of at least 3/4 in. pipe size to the ash pit or other safe point of discharge. If the water connection to the water column has a rising bend or pocket which cannot be drained by means of the water-column drain, an additional drain shall be placed on this connection in order that it may be blown off to clear any sediment from the pipe.

E. The design and material of a water column shall comply with the requirements of Section I of the 2017 ASME Code. Water column made of cast iron in accordance with SA-278 may be used for maximum boiler pressures not exceeding 250 psi. Water columns made of ductile iron in accordance with SA-395 may be used for maximum boiler pressure not exceeding 350 psi. For higher pressures, steel construction shall be used.

F. Shutoff valves shall not be used in the pipe connections between a boiler and a water column or between a boiler and the shutoff valves required for the gage glass, unless they are either outside-screw-and-yoke or lever-lifting type gate valves or stopcocks with lever permanently fastened thereto and marked in line with their passage, or of such other through-flow construction as to prevent stoppage by deposits of sediment, and to indicate by the position of the operating mechanism whether they are in open or closed position; and such valves or cocks shall be locked or sealed open. Where stop cocks are used, they shall be of a type with the plug held in place by a guard or gland.

G. No outlet connections, except for control devices (such as damper regulators and feed-water regulators), drains, steam gages, or apparatus of such form as does not permit the escape of an appreciable amount of steam or water therefrom shall be placed on the pipes connecting a water column or gage glass to a boiler.

2.6.10EBO-10 Gage Glass Connections

A. Gage glasses and gage cocks that are not connected directly to a shell or drum of the boiler shall be connected by one of the following methods:

1. The water gage glass or glasses and gage cocks shall be connected to an intervening water column.

2. When only water gage glasses are used, they may be mounted away from the shell or drum and the water column omitted, provided the following requirements are met:

3. The top and bottom gage glass fittings are aligned, supported, and secured so as to maintain the alignment of the gage glass; and

4. The steam and water connections are not less than 1 in. pipe size and each water glass is provided with a valved drain; and

5. The steam and water connections comply with the requirements of the following:

B. The lower edge of the steam connection to a water column or gage glass in the boiler shall not be below the highest visible water level in the water gage glass. There shall be no sag or offset in the piping which will permit the accumulation of water; and

C. The upper edge of the water connection to a water column or gage glass and the boiler shall not be above the lowest visible water level in the gage glass. No part of this pipe connection shall be above the point of connection at the water column.

D. Each boiler (except those not requiring water level indicators) shall have three or more gage cocks located within the visible length of the water glass, except when the boiler has two water glasses located on the same horizontal lines.

E. Boilers not over 36 in. in diameter in which the heating surface does not exceed 100 sq. ft. need have but two gage cocks.

F. The gage cock connections shall be not less than 1/2 in. pipe size.

2.6.11EBO-11 Pressure Gages

A. Each boiler shall have a pressure gage so located that it is easily readable. The pressure gage shall be installed so that it shall at all times indicate the pressure in the boiler. Each steam boiler shall have the pressure gage connected to the steam space or to the water column or its steam connection. A valve or cock shall be placed in the gage connection adjacent to the gage. An additional valve or cock may be located near the boiler providing it is locked or sealed in the open position. No other shutoff valves shall be located between the gage and the boiler. The pipe connection shall be of ample size and arranged so that it may be cleared by blowing out. For a steam boiler the gage or connection shall contain a siphon or equivalent device which will develop and maintain a water seal that will prevent steam from entering the gage tube. Pressure gage connections shall be suitable for the maximum allowable working pressure and temperature, but if the temperature exceeds 406 degrees Fahrenheit, brass or copper pipe or tubing shall not be used. The connections to the boiler, except the siphon, if used, shall not be less than 1/4 in. inside diameter standard pipe size but where steel or wrought-iron pipe or tubing is used they shall not be less than 1/2 in. The minimum size of a siphon, if used, shall be 1/4 in. inside diameter. The dial of the pressure gage shall be graduated to approximately double the pressure at which the safety valve is set, but in no case to less than 1-1/2 times this pressure.

B. Each forced-flow steam generator with no fixed steam and water line shall be equipped with pressure gages or other pressure measuring devices located as follows:

1. At the boiler or super-heater outlet (following the last section which involves absorption of heat), and

2. At the boiler or economizer inlet (preceding any section which involves absorption of heat), and

3. Upstream of any shutoff valve which may be used between any two sections of the heat absorbing surface.

C. Each high-temperature water boiler shall have a temperature gage so located and connected that it shall be easily readable. The temperature gage shall be installed so that it at all times indicates the temperature in degrees Fahrenheit of the water in the boiler, at or near the outlet connection.

2.6.12EBO-12 Stop Valves

A. Each steam outlet from a boiler (except safety valve and water column connections) shall be fitted with a stop valve located as close as practicable to the boiler.

B. When a stop valve is so located that water can accumulate, ample drains shall be provided. The drainage shall be piped to a safe location and shall not be discharged on the top of the boiler or its setting.

C. When boilers provided with manholes are connected to a common steam main, the steam connected from each boiler shall be fitted with two stop valves having an ample free blow drain between them. The discharge of the drain shall be visible to the operator while manipulating the valves and shall be piped clear of the boiler setting. The stop valves shall consist preferably of one automatic nonreturn valve (set next to the boiler) and a second valve of the outside-screw-and-yoke type.

2.6.13EBO-13 Blow-off Piping

A. A blow-off as required herein is defined as a pipe connection provided with valves located in the external piping through which the water in the boiler may be blown out under pressure, excepting drains such as are used on water columns, gage glasses, or piping to feed-water regulators, etc., used for the purpose of determining the operating condition of such equipment. Piping connections used primarily for continuous operation, such as de-concentrators on continuous blow-down systems, are not classed as blow-off's but the pipe connections and all fittings up to and including the first shutoff valve shall be equal at least to the pressure requirements for the lowest set pressure of any safety valve on the boiler drum and with the corresponding saturated-steam temperature.

B. A surface blow-off shall not exceed 2-1 /2 in. pipe size, and the internal pipe and the terminal connection for the external pipe, when used, shall form a continuous passage, but with clearance between their ends and arranged so that the removal of either will not disturb the other. A properly designed steel bushing, similar to or the equivalent of those shown in Fig. PG-59.1 of Section I of the 2017 ASME Code or a flanged connection shall be used.

C. Each boiler except forced-flow steam generators with no fixed steam and waterline and high-temperature water boilers shall have a bottom blow-off outlet in direct connection with the lowest water space practicable for external piping conforming to PG- 58.3.6 of Section I of the 2017 ASME Code.

D. All water walls and water screens which do not drain back into the boiler, and all integral economizers, shall be equipped with outlet connections for a blow-off or drain line and conform to the requirements of PG- 58.3.7 of the 2017 ASME Code.

E. Except as permitted for miniature boilers, the minimum size of pipe and fittings shall be 1 in., and the maximum size shall be 2-1/2 in., except that for boilers with 100 sq. ft. of heating surface or less, the minimum size of pipe and fittings may be 3/4 in.

F. Condensate return connections of the same size or larger than the size herein specified may be used, and the blow-off may be connected to them. In such case the blow-off shall be so located that the connection may be completely drained.

G. A bottom blow-off pipe when exposed to direct furnace heat shall be protected by firebrick or other heat resisting material which is so arranged that the pipe may be inspected.

H. An opening in the boiler setting for a blow-off pipe shall be arranged to provide free expansion and contraction.

2.6.14EBO-14 Repairs and Renewals of Boiler Fittings and Appliances

Whenever repairs are made to fittings or appliances or it becomes necessary to replace them, the work shall comply with the requirements for new installations.

2.6.15EBO-15 Conditions Not Covered by These Requirements

All cases not specifically covered by these requirements shall be treated as new installations or may be referred to the Chief Inspector for instructions concerning the requirements.

260 R.I. Code R. 260-RICR-30-10-2.6

Amended effective 4/28/2019