Relief bypass

Fig. 6. Homogenizer used as a timing pump for HTST pasteurization. Details of bypass, relief lines, equalizer, and check valves are not included (10).

In the third e.vample, the line terminates at 53%. This means DO NOT run this pump at less than 53% of the BEP. 53% of 4500 gpm is 2385 gpm. Because this is a firewater pump and because firemen need to throttle the nozzles on their fire hoses, then we need to install a pressure relief valve on this system with a discharge bypass line so that the pump dumps the restricted water (less than 2400 gpm) back into the suction tank or lake. If not, this firewater pump is likely to suffer bearing failure during an emergency. 

The lube oil pumps are now ready to be turned on. The pump and filter bypass valves should be open to avoid pressure pulses in the filter eartridges. Strong pressure pulses may eause filter eartridges to eollapse. Typieal filter elements will withstand 35-100 psi differential. If the pumps are turned on with eaeh bypass elosed, an instantaneous pressure of approximately 150 psi will hit the filters. This is due to the setting of the relief valves. For this reason, it is important to have on hand several extra seal gas and lube oil eartridges. 

The filter elements should be replaceable and should be corrosion resistant. The filter should not contain any type of internal relief valve that would permit the bypassing of the dirty oil. 

Inadvrttcnt opening of a sal ety/relief valve (stuck) 12. Turbine bypass fails open... 

As long as pressure, level, and temperature control devices are operating correctly, the safety system is not needed. If the control system malfunctions, then pressure, level, and temperature safety switches sense the problem so the inflow can be shut off. If the control system fails and the safety switches don t work, then relief valves are needed to protect against overpressure. Relief valves are essential because safety switches do fail or can be bypassed for operational reasons. Also, even when safety switches operate correctly, shutdown valves take time to operate, and there may be pressure stored in upstream vessels that can overpressure downstream equipment while the system is shutting down. Relief valves are an essential element in the facility safety system. 

Vessel is final scrubber in a flare, relief, or vent system, i.s designed to withstand maximum built-up back-pressure, and is equipped with a rupture disk or safety head (PSE) to bypass any internal or external obstructions, such as mist extractors back-pressure valves, or flame arrestors. 

When a spec break is taken from a higher to a lower MAWP, there must be a relief valve on the lower pressure side to protect the piping from overpressure. The relief valve can be either on the piping or. more commonly, on a downstream vessel. Spec break problems most commonly occur where a block valve exists on a vessel inlet, or where a bypass is installed from a high pressure system, around the pressure vessel which has a relief valve, to a lower pressure system. 

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... 

Always install a relief valve that is capable of bypassing the full-load capacity of the compressor between its discharge port and the first isolation valve. Since helical-lobe compressors are less tolerant to over-pressure operation, safety valves are usually set within 10 per cent of absolute discharge pressure, or 5 psi, whichever is lower. 

Main system relief valves are generally installed between the pump or pressure source and the first system isolation valve. The valve must be large enough to allow the full output of the hydraulic pump to be delivered back to the reservoir. This design feature, called a full-flow bypass, is essential for all hydraulic systems. The location... 

Most state laws and safe practice require a safety relief valve ahead of the first stop valve in every positive displacement compressed air system. It is set to release at 1.25 times the normal discharge pressure of the compressor or at the maximum working pressure of the system, whichever is lower. The relief valve piping system sometimes includes a manual vent valve and/or a bypass valve to the suction to facilitate startup and shutdown operations. Quick line sizing equations are (1) line connection, (i/1.75 (2) bypass, ii/4.5 (3) vent, dl63 and (4) relief valve port, cU9. 

A vapor depressuring valve is usually installed in a bypass line around the vessel pressure relief valve that handles the largest relief load in the process train. 

A policy of a three level safety design was also adopted. This includes the use of utilities and safety devices. An orthogonal design was used such that interruption of any part of these services would not affect the remaining sections. Manual bypasses were also provided in order to permit operator intervention at any point in the process. Finally, any releases of material from any of the relief devices were directed into secondary holding vessels in order to prevent releases into the atmosphere. 

Smaller rotary positive displacement compressors are controlled with external bypass. Such equipment usually has a built-in relief valve that opens at a pressure short of damaging the equipment, but the external bypass still is necessary for smooth control. Large units may be equipped with turbine or gas engine drives which are speed adjustable. Variable speed gear boxes or belt drives are not satisfactory. Variable speed dc motors also are not useful as compressor drives. Magnetic clutches and hydraulic couplings are used. 

In a hydroelectric plant it is necessary to decrease the flow of water to a turbine very rapidly in the event of a sudden drop in the load. In such a case a relief valve may be opened so as to bypass water around the machine, and then this relief valve may be slowly closed. Alternatively, an air chamber may be used to absorb the shock. Some excess water may flow into this device and compress the air to a higher pressure. One disadvantage is that water under pressure absorbs air, so it is necessary to renew the air supply periodically by the operation of a small air compressor. Also, an air chamber has distinct size limitations. 

Another feature of PD pumps is that, if the line for any reason becomes blocked, they simply continue forcing high-pressure fluid into the line and eventually break something if a precautionary rupture system has not been installed. Thus, a PD pump should be protected by a high-pressure shutoff sensor and alarm system and also a bypass line containing a rupture disk or pressure relief valve. 

Soluble powders and liquid formulations such as solutions and emulsifi-able concentrates require little agitation. Bypass agitation is sufficient for these formulations. Bypass agitation uses the returning liquid from the pressure relief valve to agitate the tank. The return must extend to the bottom of... 

Low gear oil pump bypass/relief valve setting. 

We have reported the effect of inhaled nitric oxide in 10 patients (median age, 3.3 years range, 0.4-11.1 years) with symptomatic congenital mitral stenosis.These studies were performed during interventional cardiac catheterization or after surgery requiring the use of cardiopulmonary bypass. Six patients had additional left ventricular outflow tract obstruction (median, 25 mm Hg range, 15-50 mm Hg). Effective relief of the mitral gradient was present after intervention. 

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