Haw. Code R. § 12-222.1-6

Current through September, 2024

Section 12-222.1-6 - Pressure relief valves for power boilers

(a) General requirements. The following shall apply to all power boilers:

(1) Each power boiler, miniature boiler, electric boiler, and high-temperature water boiler shall have at least one ASME and NB certified pressure relief valve marked with the ASME certification mark and "V" designator, and National Board NB symbols;

(2) When a new boiler is installed, ASME Form P-7 Manufacturer's Data Report for Pressure Relief Valves, or ASME Form P-8 Manufacturer's or Assembler's Certificate of Conformance for Pressure Relief Valves, as required by the ASME BPVC, shall be submitted along with the manufacturer's data on the power boiler;

(3) Pressure relief valves shall be manufactured in accordance with a national or international consensus standard;

(4) Only direct spring-loaded, pilot operated, or power actuated pressure relief valves or pilot operated pressure relief valves designed to relieve steam shall be used for steam service;

(5) Safety relief valves are valves designed to relieve either steam or water, depending on the application;

(6) Deadweight or weighted-lever pressure relief valves shall not be used;

(7) For high-temperature water boilers, safety relief valves shall have a closed bonnet, and valve bodies shall not be constructed of cast iron;

(8) At least one NB capacity certified pressure relief valve shall be installed on the boiler. If the boiler has more than five hundred (500) square feet of bare tube water heating surface, or if an electric boiler has a power input of more than 3.76 million Btu/hr (1,100 kilowatts), two or more NB capacity certified pressure relief valves shall be installed. For a boiler with combined bare tube and extended water-heating surface exceeding five hundred (500) square feet, two or more pressure relief valves are required only if the maximum designed steaming capacity of the boiler exceeds 4,000 Ib/hr;

(9) One or more pressure relief valves on the boiler proper shall be set at or below the maximum allowable working pressure. If additional valves are used, the highest pressure setting shall not exceed the maximum allowable working pressure by more than three per cent (3%). The complete range of pressure settings of all the pressure relief valves on a boiler shall not exceed ten per cent (10%) of the highest pressure to which any valve is set;

(10) Adjustments, repairs, and reconditioning of pressure relief valves shall be done by a National Board authorized "VR" repair company. The "VR" repair company shall affix a "VR" nameplate to the valve and provide repair documentation and the owner and user shall ensure that the nameplate identification plates remain legible; and

(11) The owner and user shall maintain all pressure relieving devices in good operating condition. When the valves cannot be tested in service, the user shall maintain and make available to the inspector records showing the test dates and set pressure for the valves.

(b) Installation of pressure relief valves. The following shall apply to the installation requirements of pressure relief valves:

(1) Every boiler shall have outlet connections for the pressure relief valve, or valves, independent of any other outside steam connection, and the area of opening shall be at least equal to the aggregate areas of inlet connections of all the attached pressure relief valves. An internal collecting pipe, splash plate, or pan should be used, provided the total area for inlet of steam is not less than twice the aggregate areas of the inlet connections of the attached pressure relief valves. The holes in such collecting pipes shall be at least 1/4 inch in diameter, and the least dimension in any other form of opening for inlet of steam shall be 1/4 inch. If pressure relief valves are attached to a separate steam drum or dome, the opening between the boiler proper and the steam drum or dome shall be not less than ten (10) times the total area of the pressure relief valve inlet;

(2) Pressure relief valves with an inlet connection greater than NPS 3 used for pressure greater than 15 psig shall have a flange or a welded inlet connection. The dimensions of flanges subjected to boiler pressure shall conform to the applicable standards;

(3) All covers, caps, and plugs utilized for shipping or transport shall be removed prior to installation or being placed in service; and

(4) Any wire or restraining device on lifting lever utilized for shipping or transport shall be removed prior to being placed in service.

(c) Discharge pipe. The following shall apply to pressure relief valve discharge piping requirements:

(1) All pressure relief valves shall be piped to a safe point of discharge so located or piped as to be carried clear from running boards or platforms. Provision for an ample gravity drain shall be made in the discharge pipe at or near each pressure relief valve, and where water or condensation may collect. Each valve shall have an open gravity drain through the casing below the level of the valve seat. For iron and steel-bodied valves exceeding NPS 2, the drain hole shall be tapped not less than NPS 3/8;

(2) Discharge piping from pressure relief valves on high-temperature water boilers shall have adequate provisions for water drainage as well as steam venting;

(3) If a muffler is used on a pressure relief valve, it shall have sufficient outlet area to prevent back pressure from interfering with the proper operation and discharge capacity of the valve. The muffler plates or other devices shall be so constructed as to avoid a possibility of restriction of the steam passages due to deposits; mufflers shall not be used on high-temperature water boiler pressure relief valves; and

(4) When a discharge pipe is used, it shall be at least the same size of the safety valve discharge port and fitted with an open drain to prevent water lodging in the upper part of the safety valve or in the discharge pipe. Sectional areas of a common discharge pipe shall not be less than the same size of the combined multiple valve outlets discharging into the common discharge pipe. The discharge pipe shall be as short and straight as possible and arranged to avoid undue stresses on the valve or valves. Discharge pipe elbows shall be placed close to the safety valve outlet, or the discharge pipe shall be anchored and supported securely. If umbrella type drip pan connection is used, the discharge piping shall be designed to prevent binding due to expansion.

(d) Capacity. The following shall apply to pressure relief valve capacity of power boilers:

(1) The pressure relief valve capacity for each boiler shall be such that the valve or valves will discharge all the steam that can be generated by the boiler without allowing the pressure to rise more than six per cent (6%) above the maximum allowable working pressure of the boiler;

(2) The minimum relieving capacity for other than electric boilers and forced-flow steam generators with no fixed steam line and waterline shall be estimated for the boiler and waterwall heating surfaces as given in NBIC Part I, Table 2.9.1.3 below, but in no case shall the minimum relieving capacity be less than the maximum designed steaming capacity as determined by the manufacturer;

(3) The required relieving capacity, C, of the pressure relief valves on a high temperature water boiler shall be determined as follows:

(A) C = Q/L;

(B) C = required relieving capacity in Ibs/hr (kg/hr);

(C) Q = maximum output in BTUH (W) at the boiler nozzle obtained by the firing of any fuel for which the unit is designed; and

(D) L = 1,000 BTU/lb (646W hr/kg);

(4) The minimum pressure relief valve capacity for electric boilers shall not be less than 3.5 Ibs/hr/KW input; and

(5) If the pressure relief valve capacity cannot be computed, or if it is desirable to prove the computations, it should be checked by any one of the following methods; and if found insufficient, additional relieving capacity shall be provided:

(A) By performing an accumulation test by shutting off all other steam discharge outlets from the boiler and forcing the fires to maximum (this method should not be used on a boiler with a superheater or reheater, or on a high-temperature water boiler);

(B) By measuring the maximum amount of fuel that can be burned and computing the corresponding evaporative capacity on the basis of the heating value of the fuel; or

(C) By determining the maximum evaporative capacity by measuring the feedwater. The sum of the pressure relief valve capacities marked on the valves shall be equal to or greater than the maximum evaporative capacity of the boiler. This method should not be used on high-temperature water boilers.

Table 2.9.1.3

MINIMUM POUNDS OF STEAM PER HOUR PER SQUARE FOOT OF HEATING SURFACE lb steam/hr ft² (kg steam/hr m²)

	Firetube Boiler	Watertube Boiler
Boiler Heating Surface
Hand-fired	5(24)	6(29)
Stoker-fired	7(34)	8(39)
Oil, gas, or pulverized coal	8(39)	10 (49)
Waterwall Heating Surface
Hand-fired	8(39)	8(39)
Stolker-fired	10 (49)	12(59)
Oil, gas, or pulverized coal	14 (68)	16 (78)
Copper-finned Watertubes
Hand-fired		4(20)
Stoker-fired		5(24)
Oil, gas, or pulverized coal		6(29)

Notes:

* When a boiler is fired only by a gas having a heat value not in excess of 200 Btu/ft.3(7.5MJ(m3), the minimum relieving capacity should be based on the values given for hand-fired boilers above.

* The heating surface shall be computed for that side of the boiler surface exposed to the products of combustion, exclusive of the superheating surface In computing the heating surface for this purpose only the tubes, fireboxes, shells tubesheets, and the projected area of headers need to be considered, except that for vertical firetube steam boilers, only that portion of the tube surface up to the middle gage cock is to be computed

* For firetube boiler units exceeding 8,000 Btu/ft.2 (9 085 J/cm 2) (total fuel Btu (J) Input divided by total heating surface), the factor from the table will be increased by 1 (4.88) for every 1,000 Btu/ft.2 (1,136 J/cm.2) above 8.000 Btu/ft.2 (9,085 J/cm 2) For units less than 7,000 Btu/ft.2 (7,950 J/cm 2), the factor from the fable will be decreased by 1 (4 88)

* For watertube boiler units exceeding 16,000 Btu/ft.2 (18,170 J/cm.2) (total fuel Btu input divided by the total heating surface) the factor from the table will tie increased by 1 (4.88) for every 1,000 Btu/ ft.2 (1,136 J/cm.2) above 16,000 Btu/ft.2 (18,170 J/cm.2). For units with less than 15,000 Btu/ft.2 (17,034 J/cm.2), the factor In the table will be decreased by 1 (4 88) for every 1,000 Btu/ft.2 (1,136 J/cm.2) below 15,000 Btu/ft.2 (17.034 J/cm 2).

(e) Location. The following shall apply to the location of the installation of pressure relief valves of power boilers:

(1) Pressure relief valves shall be placed on, or as close as physically possible to, the boiler proper;

(2) Pressure relief valves shall not be placed on the feedline;

(3) Pressure relief valves shall be connected to the boiler independent of any other connection without any unnecessary intervening pipe or fittings. The intervening pipe or fittings shall not be longer than the face-to-face dimension of the corresponding tee fitting of the same diameter and pressure rating as listed in the applicable standards;

(4) Every pressure relief valve shall be connected to stand in an upright position with spindle vertical;

(5) The opening or connection between the boiler and the pressure relief valve shall have at least the area of the valve inlet, and the inlet pipe to the pressure relief valve shall be as short and straight as possible, no longer than twice the center-to-end (face) dimension of a corresponding tee fitting of the same diameter, pressure class, and connection type. When a discharge pipe is used, the cross-sectional area shall not be less than the full area of the valve outlet, or of the total of the areas of the valve outlets. The discharge pipe shall be as short and straight as possible and arranged to avoid undue stresses on the valve or valves;

(6) No valves of any type except a changeover valve as defined below, shall be placed between the pressure relief valves and the boiler, nor on the discharge pipe between the pressure relief valves and the atmosphere;

(7) A changeover valve, which allows two redundant pressure relief valves to be installed for the purpose of changing from one pressure relief valve to the other while the boiler is operating, may be used provided the changeover valve is in accordance with the original code of construction. It is recommended that the department be contacted to determine the acceptability of changeover valves on boiler applications. The changeover valve shall be designed such that there is no intermediate position where both pressure relief valves are isolated from the boiler;

(8) When two or more pressure relief valves are used on a boiler, they should be mounted either separately or as twin valves made by placing individual valves on Y-bases, or duplex valves having two valves in the same body casing. Twin valves made by placing individual valves on Y-bases or duplex valves having two valves in the same body shall be of equal size;

(9) When two valves of different sizes are installed singly, the relieving capacity of the smaller valve shall not be less than fifty per cent (50%) of that of the larger valve; and

(10) When a boiler is fitted with two or more pressure relief valves on one connection, this connection to the boiler shall have a cross-sectional area not less than the combined areas of inlet connections of all the pressure relief valves with which it connects.

Haw. Code R. § 12-222.1-6

[Eff and comp 12/21/2019] (Auth: HRS § 397-4) (Imp: HRS § 397-4)

Am and comp 9/8/2024