§ 3a.26. Safety devices.
(a) A boiler or unfired pressure vessel must be protected by safety relief devices, and indicating and controlling devices sufficient to insure its safe operation which meet all of the following requirements:
(1) The devices must be constructed, located, installed and maintained to prevent the safety devices from becoming inoperative.
(2) The devices must have sufficient relieving capacity to prevent a rise of pressure in the boiler or unfired pressure vessel of more than 10% above the maximum allowable working pressure, taking into account the effect of static head.
(3) The discharge from safety devices must be carried to a safe place away from the boiler or unfired pressure vessel.
(b) Safety valves for other than noxious liquids or toxic vapors must be direct spring-loaded type valves, designed with substantial lifting devices so that the disk can be lifted from its seat by the spindle of at least 1/8 the diameter of the valve if the pressure of the vessel is at 75% of the safety valve setting.
(c) Each safety valve must have clear manufacturer markings that are 1/4-inch or larger. The markings must contain all of the following information stamped on the valve, cast on the valve body, or cast on a plate securely fastened to the valve:
(1) The name or identifying trademark of the manufacturer.
(2) The pipe size, in inches, of the valve inlet.
(3) The pressure, in pounds, at which the valve is set to open.
(4) The blow down, in pounds.
(d) If the valve inlet is not threaded, the initial diameter of the inlet may not be less than the inside diameter of a standard pipe of the same size.
(e) The difference between the opening and closing pressures of a safety valve must be a minimum of 20%.
(f) Existing safety valves bearing ASME stamping different from the requirements in subsection (c) are permitted if the safety valves have equivalent construction and relieving capacity.
(g) Safety valves with a cast iron seat or a disk may not be used.
(h) If more than one safety valve is used, the discharge capacity must be the combined capacity of all safety valves.
(i) A boiler or unfired pressure vessel in which pressure is not generated and is derived from an outside source must have a safety device connected to the vessel or system which it protects in a manner to prevent a rise in pressure beyond the maximum allowable pressure.
(j) A boiler or unfired pressure vessel in which pressure may be generated must have a safety device or devices connected directly to the vessel and comply with all of the following:
(1) When the contents of a vessel may cause interference with the operation of the vessel or safety valve when the safety value is directly attached, the safety valve or valves may be connected in a manner to avoid the interference.
(2) An escape pipe may be used. The pipe must be full sized and fitted with an open drain to prevent liquid from lodging in the upper part of the safety valve. A valve may not be placed on the escape pipe between the safety valve and the atmosphere.
(3) An elbow may be placed on an escape pipe if it is located close to the safety valve outlet or the escape pipe is securely anchored and supported. If two or more safety devices are placed on one connection, the connection must have a cross sectional area at least equal to the combined area of the safety devices’ inlets.
(k) Every safety valve which is exposed to temperatures of 32°F or less must have a drain of at least 3/8 inch in diameter at the lowest point where water can collect.
(l) A spring in a safety or relief valve in service for pressures 250 psi and less may not be reset for a pressure more than 10% above or 19% below the pressure at which the valve is marked. For pressures higher than 250 psi, the spring may not be reset for any pressure more than 5% above or 50% below the pressure at which the safety or relief valve is marked.
(m) Safety valves for compressed air tanks cannot be larger than 3-inch diameter. The valves must be proportioned for the maximum number of cubic feet of free air that may be applied per minute.
(n) A rupture disk may be used as a pressure safety device on boilers or unfired pressure vessels containing nontoxic gases, when it is designed to fail at not more than the design pressure of the vessel.
(o) Safety valves on systems using toxic gases must discharge in accordance with the ASME Code, Section VIII, Division 1, 2 or 3.
(p) A company or organization holding a Department-issued certificate of authorization to reset and reseal safety valves and relief valves or a current VR stamp is required to reset and reseal safety valves and relief valves.
(q) A company or organization holding a current VR stamp is required to repair safety valves and relief valves.
(r) A safety valve or relief valve may not be loaded to maintain a working pressure in excess of the maximum working pressure stated on the boiler or unfired pressure vessel’s certificate of operation.
(s) Additional or supplemental safety or relief valves installed on a boiler or unfired pressure vessel, may exceed maximum working pressure if the valves comply with the applicable code of construction or this chapter.
Cross References This section cited in 34 Pa. Code § 3a.152 (relating to safety appliances).
No part of the information on this site may be reproduced for profit or sold for profit.
This material has been drawn directly from the official Pennsylvania Code full text database. Due to the limitations of HTML or differences in display capabilities of different browsers, this version may differ slightly from the official printed version.
