1. Brie Briefl flyy des descr crib ibee the the appl applic icat atio ions ns and and imi imita tati tion onss for for the the fol follo lowi wing ng safe safety ty reli relief ef devices. .
safety ty valv valvee is a dire direct ct sprin pring g load loaded ed pres pressu sure re reli relief ef valv valvee that that Safety Safety valve - A safe is actuated by the static pressure upstream of the valve and characterized by rapid opening or pop action relief valve is a direct spring loaded loaded pressure relief relief valve actuated by the the static Relief valve - A relief pressure upstream of the valve. The valve opens normally in proportion to the pressure increase over the opening pressure. conventional safety relief relief valve is a direct spring loaded loaded Conventional safety relief valve - A conventional pressure relief valve whose operational characteristics (opening pressure, closing pressure, and relieving capacity) are directly affected by changes in the back pressure safety relief valve valve is a pressure relief relief valve in Pilot operated safety relief valve - A pilot-operated safety which the maor relieving device or main valve is combined with and controlled by a self actuated au!iliary pressure relief valve (pilot). Balanced safety relief valve - A balanced safety relief relief valve is a direct direct spring loaded loaded pressure relief valve that incorporates a bellows or other means for minimizing the effect of back pressure on pressure on the operational characteristics of the valve. and temperature sensitive element element of a rupture disk Rupture disk - a pressure containing, pressure and device. "upture disks may be designed in several several configurations, such as flat, flat, domed (prebulged), or reverse acting. The rupture disk holder secures the disk in place. A rupture disk device is a nonreclosable pressure relief device actuated by the static differential differential pressure between the inlet a nd outlet of the device and device and designed to function by the bursting of a rupture disk.
2.
What should be checked during an on-stream inspection of a relieving device?
a. The correct relief device wa s installed. b. The company identification (such as a tag or stencil) provides means to establish the proper pressure setting for the e#uipment protected by the identified device. c. $f not clear from the records, that the established test interval has not been e!ceeded. d. %o gags, blinds, closed valves, or piping obstructions would prevent the valves from functioning properly. e. &eals installed to protect the spring setting and ring pin setting have not been broken. f. The relief device does not leak. 'ressure relief valves that have opened in-service fre#uently leak. etection and correction of this leakage eliminates product loss and possible pollution and prevents fouling and subse#uent sticking of the valve. $f the valve is a bellows valve, the bellows vent should be checked for leakage. g. ellows vents are open and clear, and any connected piping is routed to a safe location. h. *pstream and downstream block valves are sealed or chained and locked in the proper position. evices that ensure that a block valve is in its proper position include locking plastic bands, car seals, chains and padlocks, and special locking devices made especially for certain types of block valves. i. +ent stacks, discharge piping and small nipples are properly supported to avoid breakage or leakage. $nade#uately supported or anchored nipples can be damaged during maintenance and by vibration. . +alve +alve body drains and and vent stack drains are open. k. Any lifting lever is operable and positioned properly. properly. l. Any heat tracing, insulation or purge that is critical to the proper operation of the relief system is intact and operating properly. properly. m. A gauge gauge installed as part of a combination of a rupture disk and a pressure relief valve or a device for checking pressure between a pressure relief valve and a block valve is serviceable. heck to see that there is no pressure build up indicated by a gauge installed between a rupture disk and a pressure relief valve. n. Any rupture disk is properly oriented.
3.
ist 3 applications applications of a rupture disk. disk.
a. To protect the upstream side of pressure relief valves against corrosion by the system fluid. b. To protect pressure relief valves against plugging or clogging by viscous fluids or polymerization products. c. $nstead of pressure relief valves if the protected system can tolerate process interruptions or loss of fluids in case the disk ruptures. d. $nstead of pressure relief valves if e!tremely fast response is desirable. e. As secondary pressure-relieving devices when the difference between the operating pressure and the rupture pressure is large, depending on the type of rupture disk selected.
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What is the principal reason for inspecting relieving devices?
$nspections of pressure relief devices must determine the general physical and operating conditions of the devices, and ensure that their performance meets the requirements for a given installation. $n making this determination, two types of inspections can be used. They are shop inspectionoverhauls, and visual on-stream inspections. 're- and post-testing of the pressurerelieving device should be included in the /shop inspectionoverhaul0.
". What is the primary consideration in evaluating the inspection fre#uency to be established for relieving devices? . The inspection of pressure-relieving devices provides data that can be evaluated to determine a safe and economical fre#uency of scheduled inspections.
$. %here are 3 bases for establishing the inspection fre#uency. What is each and briefly describe them. &. What inspections and testing should be done on new relieving devices installations? All pressure relief valves and other automatic pressure-relieving devices that depend on a spring adustment for proper functioning should be inspected and tested before they are installed on process e#uipment
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(f a valve fails to open within the pressure tolerance) what should be done?
$f a valve fails to open within the set pressure tolerance, it re#uires immediate attention. $f it opens at the set pressure but fails to reseat properly, the urgency of inspection and repairs depends on the type of leakage, its environmental and human impact, the amount of leakage, and the characteristics of the leaking substance such as whether it1s to!ic, flammable, or fouling.
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What is the ideal time to inspect relieving devices?
The ideal time to inspect pressure relief valves is when the inspection least interferes with the process and maintenance manpower is readily available.
1+. unit?
What should be done during e,tended shutdowns with relieving devices left on a
A pressure relief valve left on a unit during an e!tended shutdown should be inspected and tested before the resumption of operations.
11.
ollowing reassembly of the relieving device what tests should be done?
Air and 234 test
12.
What identification data should be carried on a relieving device tag?
*nit designation, ompany number, &et pressure, 5#uipment designation, Test dates
13.
When repairing a relieve device in place what precautions should be observed?
4nly an authorized person should isolate a relief device by closing any adacent block valves upstream or downstream. (&ee A&65 &ection +$$$, Appendi! 6). This may re#uire providing or identifying alternate relief protection. The space between the relief device and any adacent block valve should be vented to a safe location to release trapped lading fluid and to determine whether the block valve is holding. $f a block valve is not installed on the downstream side of a relief device discharging into a common header, a blind or other suitable means should be p rovided to prevent discharge through the open outlet pipe in case one of the other relief devices opens. A blind should be inserted between the pressure relief valve and any adacent upstream block valve before a pressure relief valve is inspected or repaired in place. $f the pressure relief valve discharges into a common discharge header, a blind should be installed between the pressure relief valve and the header. $f there is a rupture disk device associated with the pressure relief valve and the rupture disk device is disturbed as part of the accompanying relief valve removal, consider the need to install a new rupture disk since the disk could easily be damaged and could fail prematurely if reused. All blinds should be removed after the relief device has been inspected, repaired or replaced. The block valves on the inlet and outlet should be opened and locked or sealed in that position. 7hen used with a relief device, these block valves must have full pipe area through them to prevent flow restriction and possible instability when the relief device opens. $n cases where there are in-situ spare pressure relief valves, the outlet side should be protected from an inlet leak through overpressure. The inlet block valve of the spare valve should be closed. The outlet block valve could be locked open, or p ositive means of venting could be provided, if the outlet is shut. •
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1!. What operating information should be contained in the operating history of a relieving device? An operating history of each pressure relief valve since its last inspection should be obtained and should include pertinent information such as8 a. $nformation on upsets and their effect on the valve. b. The e!tent of any leakage while in service. c. Any other evidence of malfunctioning. $n addition, records of valve p erformance during previous runs should be checked to determine whether changes are needed in the valve materials or components or in the inspection interval.
1". lat metal rupture disks are usually limited to what percentage of the disks predetermined bursting pressure? 9or prebulged metal rupture disks installed so that pressure acts against the concave side and for flat metal rupture disks, the operating pressure of the protected system is usually limited to :; -<;= of the disk1s predetermined bursting pressure. The e!act percentage depends on the type of disk used.
1$.
What medium are generally used to test relieving devices in the shop test block?
7ater, air, or an inert gas such as bottled nitrogen is generally used as the testing medium in the shop.
1&. 1'.
Briefly describe the shop test block used for testing with air. ake a sketch. What things should be done prior to removal of the relieve devices to the shop?
efore moving the valve, flange faces on the valve (and flanges on the piping) should be protected so that gasket faces are not damaged. The valves should be transported in the upright position.
1*. ist at least $ of the * points that are visually checked during the dismantling of a relieving device. a. The flanges, for evidence of pitting, roughening, or decreases in the width of seating surfaces. b. The springs, for evidence of corrosion or cracking and for the correct pressure range at the valve1s operating pressure and temperature. c. $f the valve is of the bellows type, the bellows for evidence of corrosion, cracking or deformation. d. The positions of the set screws and openings in the bonnet. e. The inlet and outlet nozzles, for evidence of deposits of foreign material or corrosion. f. The e!ternal surfaces, for any indication of a corrosive atmosphere or of mechanical damage. g. The body wall thickness. h. +alve components and materials, for a match with the information on the identification tag and specification card. i. The pilots and associated parts.
2+.
/rior to the start of dismantling what test should be performed and why?
a valve should be visually inspected to estimate its condition when removed from service. This inspection should be made by the shop1s pressure relief valve repair mechanic unless unusual corrosion, deposits, or conditions are noted in the pressure relief valve
21.
0uring the relieving device test after reassembly what 2 points are checked?
+alve set pressure and check for tightness or leaks.
22.
What basic information should the specification record contain?
The specification record provides the basic information needed to evaluate the ade#uacy of a device for a given installation or for a contemplated change in operating conditions, provides the correct dimensional and material information needed to minimize shop errors and e!pedite repairs, and provides design information that facilitates the purchase of a similar device and that is re#uired to inventory spare parts.
23.
What data should the istorical data contain?
The historical record for a pressure-relieving device shows a typical permanent card-form service record that holds the dates and results of periodic inspections and tests. The information recorded will form a basis for determining test intervals and design changes .
2!.
ist $ causes of improper performance in relieving devices.
amaged &eating &urfaces 9ailed &prings $mproper &etting and Adustment 'lugging and &ticking 6isapplication of 6aterials $mproper >ocation, 2istory, or $dentification "ough 2andling. $mproper ifferential etween 4perating and &et 'ressures $mproper ischarge 'iping Test 'rocedures
2".
What is the meaning of 0%/?
The pressure at which a pressure relief valve is adusted to open on the test stand. The T' includes corrections for the service conditions of back pressure or temperatures or both.
2$. What should be done with connecting piping and block valves before disconnecting relief valves? efore disconnecting pressure-relieving devices, the connected piping and block valves sh ould be checked to ensure that they are sufficiently supported.
2&.
What should be done before relief lines are opened to the atmosphere?
efore inspection and any repairs on pressure-relieving devices are e!ecuted, general precautions should be taken to maintain the safety of the e#uipment protected by the devices, especially if the e#uipment is in operation. 7hen inspection and repairs on an operating unit are re#uired, the unit operations should be normal and the proper authority and permits for the work should be obtained.
2'.
What 2 things are tested for in the test block?
as received pop pressure. it can be tested for seat tightness by increasing the pressure on the valve to ?@= of the T' and observing the discharge side of the valve for evidence of leakage.
2*. device.
ist the applications and limitations for each type of non-reclosable relieving
A pressure relief device is actuated by inlet static pressure and designed to open during emergency or abnormal conditions to prevent a rise of internal fluid pressure in e!cess of a specified design value. The device also may be designed to prevent e!cessive internal vacuum. The device may be a pressure relief valve, a non-reclosing pressure relief device or a vacuum relief valve. ommon e!amples include direct spring loaded pressure relief valves, pilot-operated pressure relief valves, rupture disks, weight-loaded devices, and pressure andor vacuum vent valves. "elief valves should not be used as follows8 a. $n steam, air, gas, or other vapor services. b. $n services piped to a closed header unless the effects of any constant or variable back pressure has been accounted for. c. As pressure control or bypass valves.
