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Leaking Relief Valves

Many relief valves leak hydrocarbons to the flare. If the vessel with a leaking relief valve is operating at a substantial pressure (about 30 or 40 psig), then the line downstream of the relief valve will be noticeably (perhaps 10°F) colder than the relief valve connection itself, due to a Joule-Thompson expansion. [Pg.592]

If the vessel with the leaking relief valve is liquid full with light hydrocarbons (ethane, propane, or butane), then a leaking relief valve will be quite obvious. The line downstream of the faulty pressure relief valve will be covered with ice. The ice is atmospheric moisture freezing on the line to the flare. This is not due to a Joule-Thompson expansion, but due to the auto-refrigeration of the volatile hydrocarbon liquid as it flashes to a vapor in the flare header piping. [Pg.592]


Hand jacks are a big help on large relief valves for several reasons. One is to give the operator a chance to reseat a leaking relief valve. [Pg.18]

The decision to apply a mechanical constraint to stop a leak should be carefully weighed to ensure that the situation is not exacerbated. For example, a leaking relief valve on a rail car may be caused by overfilling or by a pressure-producing reaction. In such circumstances, it would not be appropriate to cap or gag the relief valve. [Pg.104]

Often, the blowdown valve is routed to a closed flare system, which services other relief valves in the facility to ensure drat all the gas is vented or flared at a safe location. In such instances, a separate manual blow -down valve piped directly to atmosphere, with nothing else lied in, is also needed. After the compressor is shut down and safely blown down through the flare system, the normal blowdown valve must be closed to block any gas that may enter the flare system from other relief valves. The manual blowdown valve to atmosphere protects the operators from small leaks into the compressor during maintenance operations. [Pg.279]

Rupture discs are also used below relief valves to protect them from corrosion due to ves.sel fluids. The rupture disc bursts first and the relief valve immediately opens. The relief valve reseals, limiting flow when the pressure declines. When this configuration is used, it is necessary to monitor the pressure in the space between the rupture disk and the relief valve, either with a pressure indicator or a high pressure switch. Othei-wise, if a pinhole leak develops in the rupture disk, the pressure would equalize on both sides, and the rupture disk would not rupture at its set pressure because it works on differential pressure. [Pg.367]

Many leaks have been discussed under other headings, including leaks that occurred during maintenance (Chapter 1), as the result of human error (Chapter 3), or as the result of overfilling storage tanks (Section 5.1). Other leaks have occurred as the result of pipe or vessel failures (Chapter 9), while leaks of liquefied flammable gas are discussed in Chapter 8 and leaks from pumps and relief valves in Chapter 10. [Pg.144]

A visible cloud of vapor, 1 m deep, spread for 150 m and was ignited by a car that had stopped on a nearby road 25 minutes after the leak started. The road had been closed by the police, but the driver approached from a side road. The fire flashed back to the sphere, which was surrounded by flames. There was no explosion. The sphere was fitted with water sprays. But the system was designed to deliver only haif the quantity of water normally reeommended (0.2 U.S. gal/ft- min. or 8 L/m min.), and the supply was inadequate. When the fire brigade started to use its hoses, the supply to the spheres ran dry. The firemen seemed to have used most of the available w ater for cooling neighboring spheres to stop the fire from spreading, in the belief that the relief valve would pro-teet the vessel on fire. [Pg.167]

Do not assume that such things could not happen in your company (unless you have spent some time in the relief-valve workshop). All relief valves should be tested and inspected regularly. Reference 3 describes model equipment and procedures. When a large petroleum company introduced a test program, it was shocked by the results out of 187 valves sent for testing, 23 could not be tested because they were leaking or because the springs were broken, and 74 failed to open within 10% of the set pressure—that is, more than half of them could not operate as required [4]. [Pg.215]

The process involved in the incident is concerned with the separation of crude into three phases. The crude is pumped into a two stage separation process where it is divided into three phases oil, gas, and water. The water is cleaned up and dumped to drain. The remaining mixture of oil and gas is then pumped into the main oil line where it is metered and sent on for further processing. A simplified process diagram is shown in Figure 7.1. The case study described here is centered on a flange leak in one of the oil pipeline pumps (pump A) and its associated pressure relief valve piping. [Pg.294]

The use of bypass lines and valves is best avoided. Bypass valves are often found to be leaking steam because of wire drawing of the seating faces of valves, which have not been tightly closed. If they are used, the capacity of the bypass valve should be added to that of the pressure-reducing valve when sizing relief valves. If it is thought... [Pg.324]

Massive leak. It may be due to faulty operation of pressure relief valve, chemically induced failure of tank wall, puncture by a sharp object, or normal operation of pressure relief valve in case of fire. [Pg.562]

Slow leak. Probable reasons may be stress cracking of tank liner, faulty operation of pressure relief valve, faulty coupling from tank to the feed line, or failure of the fuel line connection. [Pg.562]

The most common scenario of interest for LOPA in the chemical process industry is loss of containment of hazardous material. This can occur through a variety of incidents, such as a leak from a vessel, a ruptured pipeline, a gasket failure, or release from a relief valve. [Pg.503]

Carbon dioxide is usually purchased in a tank, inside the tank the mobile phase exists as a liquid. Typically, the tank does not come with a pressure gauge but is hooked up to a pressure relief valve and rupture disk, which are set above the tank pressure should a tank leak occur. [Pg.570]

Air emissions include point and nonpoint sources (Chapter 4). Point sources are emissions that exit stacks and flares and thus can be monitored and treated. Nonpoint sources are fugitive emissions that are difficult to locate and capture. Fugitive emissions occur throughout refineries and arise from the thousands of valves, pumps, tanks, pressure relief valves, flanges, and so on. Although individual leaks are typically small, the sum of all fugitive leaks at a refinery can be one of its largest emission sources. [Pg.306]

RDs differ from relief valves, because once burst, they cannot reclose. Therefore, they are only used by themselves as primary relief devices if this characteristic can be tolerated. For a given venting area, they are less expensive than the relief valve. Their main advantage is that they do not leak, as PSVs can. If a tank is protected by both an RD and a PSV (mounted on differ-... [Pg.486]


See other pages where Leaking Relief Valves is mentioned: [Pg.592]    [Pg.592]    [Pg.981]    [Pg.323]    [Pg.324]    [Pg.333]    [Pg.250]    [Pg.222]    [Pg.396]    [Pg.5]    [Pg.162]    [Pg.170]    [Pg.393]    [Pg.14]    [Pg.281]    [Pg.465]    [Pg.471]    [Pg.721]    [Pg.430]    [Pg.435]    [Pg.430]    [Pg.435]    [Pg.157]    [Pg.139]    [Pg.80]    [Pg.238]    [Pg.112]    [Pg.113]    [Pg.153]   


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