Pressure-control valve

Fig. 1. Fat sphtter. TRC, temperature recorder controller FLIC, Hquid level indicator controller PCV, pressure control valve and HCV, heat control valve.

Pneumatic and hydraulic vibrating conveyors have as their greatest asset ehmination of explosion hazards. If pressurized air, water, or oil is available, they can be extremely practical since their drive design is relatively simple and pressure-control valves can be used to vaiy capacity either manually or automatically. 

In most units, the flue gas pressure is reduced to atmospheric pressure across an orifice chamber. The orifice chamber is a vessel containing a series of perforated plates designed to maintain a given back-pressure upstream of the regenerator pressure control valve. 

Flue gas line hydraulics to the expander, including the regenerator pressure control valve... 

Demonstrate the oil pressure control valve can control oil pressure. 

Another pressure control method is a hot gas bypass. The author has seen a retrofitted hot gas bypass system solve an unsatisfactory pressure control scheme. In the faulty system, a pressure control valve was placed between the overhead condenser and the lower reflux drum. This produced en atic reflux drum pressures. A pressure safety valve (psv) vented the reflux drum to the flare to protect against over-pressure. A psv saver control valve, set slightly below the psv relieving... 

The fix for the erratic reflux drum pressure problem was to provide for separate pressure control of the fractionator column and the reflux drum. A new pressure control valve was installed upstream of the condenser and the old condenser outlet control valve was removed. A hot gas bypass, designed for 20% vapor flow, was installed around the pressure control valve and condenser. A control valve was installed in the hot gas bypass line. The column pressure was then maintained by throttling the new control valve upstream of the condenser. The reflux drum pressure w as controlled by the hot gas bypass control valve and the psv saver working in split range. The new system is shown in the figure below. 

Incorrect pressure control valve set- wheels, causing unbalance. 

For positive displacement pumps, a bypass-type control valve should be furnished to set the primary lube system pressure. The valve should be able to maintain system pressure during pump startup and pump transfers, which includes relieving the capacity of one pump, while both are running. The valve should provide stable, constant pressure during these transients. Flow turndown of 8 to 1 is not unusual. Multiple valves in parallel should be used if a single valve is not suitable. The valve should be sized to operate between 10 and 90% of the flow coefficient (Cv). Additional pressure control valves should be furnished as required to pro ide any of the intermediate pressure levels. 

On the smaller, non-API type systems, the relief valve is also the pressure control valve. This definitely must be an external valve. While a compromise for the smaller system, the requirements are also not so severe. 

Lubrication of cuuplitigs, Lubrication pumps. uid drivers, 309 Lubrication systems check valves, I commissioning, 462, 4ti coolers, 315 degassing drum, 322 filters, 316 gear box, 328 oil flooded helical, 109 overall system review, 1 overhead tanks, 319 piping, 322 pressure control valves, 313... 

FV - Flow Control Valve T - Tank P - Pump PV - Pressure Control Valve RV - Relief Valve V - Valve 1 - 1 inch size P - Pressure T - Temperature L - Level F - Flow I - Indicator C - Controller A - Alarm H - High. L - Low... 

Moke end Model for Flow, Temperoture and Pressure Control Valves Hand Voives Thermometers, Steam Traps and Strainers, Electrical ortd other miscellaneous equipment. 

The choice of a suitable temperature or pressure control valve for steam application will depend on the supply side pressure, the downstream pressure, and the flow rate of steam to be passed. In the case of temperature control valves the first of these is usually known and the third can be calculated, but the appropriate pressure drop through the valve is often to be decided. Sometimes the maker s rating of a heater will specify that it transfers heat at a certain rate when supplied with steam at a certain pressure. This pressure is then the pressure downstream of the control valve, and the valve may be selected on this basis. 

The safe and efficient operation of fluid power systems, system components and related equipment requires a means to control pressure within the system. There are many types of automatic pressure control valves. Some of them merely provide an escape for excess pressures some only reduce the pressure and some keep the pressure within a pre-set range. 

On double seal installations, be sure the sealing liquid lines are connected, the pressure control valves are properly adjusted, and the sealing liquid system is operating before starting the equipment. 

Figure A8.14 Closed column reactor for the production of L-alanine. 1) reactor 2) plunger pump 3) pressure control valve 4) reservoir 5) substrate tank 6) pressure gauge 7) safety valve 8) heat exchanger.

The whole set-up for partial oxidation comprises a micro mixer for safe handling of explosive mixtures downstream (flame-arrestor effect), a micro heat exchanger for pre-heating reactant gases, the pressure vessel with the monolith reactor, a double-pipe heat exchanger for product gas cooling and a pneumatic pressure control valve to allow operation at elevated pressure [3]. 

Two separate 2.1 L reservoirs contain the catalyst and product phases and the contents are fed into the reactor through a standard liquid mass flow controller. The contents of the reactor can be sampled from a pressure fed sample tube. The pressurized liquid reactor products exit the reactor through a pressure control valve, which reduces the pressure to atmospheric, and the liquid contents are delivered to a continuous decanter where the phases separate. The catalyst phase then settles to the bottom where it is drained for recycle and reuse, while the product phase is collected into a 4.2 L reservoir. 

A fixed-bed reactor system was employed (Figure 32.2). Each of the two reactors was charged with 38 cc of Amberlyst BD20 catalyst. Sample ports located at the exit of each reactor enabled increased acquisition of residence time data. Pressure was maintained by a back pressure control valve to maintain methanol in the liquid phase. After charging, the 1st and then 2nd reactors were connected to the pumps and filled with the reaction mixture while vapor was released from each through the top vent valve. Once each reactor was filled with liquid and emptied of vapor, the pressure regulator was connected to the output and both reactors were immersed into the water bath. 

Limit steam pressure with a relief valve or pressure control valve on the steam connection, thus limiting the maximum temperature short of a runaway. 

Industry literature typically cites concern with open air explosions when 4,536 kgs (10,000 lbs.) or more of flammable gas is released, however, open air explosions at lower amounts of materials are not unheard of. When the release quantity is less than 4,536 kgs (10,000 lbs.), a flash fire is usually the result. The resulting fire or explosion damage can cripple a hydrocarbon processing facility. Extreme care must be taken to prevent the release of hydrocarbon from vessels resulting in vapor releases and resultant blast overpressure. Measures such as hydrotesting, weld inspections, pressure control valves, adequate pressure safety valves, etc., should all be prudently applied. 

Figure 1. Diagram of apparatus (M) monomer reservoir (F) flow meter (VG) vacuum gage (mercury manometer) (E) electrode (T) liquid nitrogen trap (P) mechanical pump (V,) needle valve (Vt) stop valve (Vs) pressure control valve (OSC) discharge frequency oscillator (AMP) amplifier (1MC) impedance matching circuit...

There was one instance of a pipe leaking near the pressure control valve. This was readily fixed but resulted in one day of downtime. The leak was attributed to having retrofitted an alternative pipe routing without a thermal expansion analysis. 

Pressure control valve Check vale Block and bleed valve... 

Monthly Gauges in good working condition and reading normal pressure, control valves (with locks or electronic supervision) open, fire department connections in good condition... 

Depressurization of the oxidation unit is achieved with the use of a high pressure control valve (Annin Wee Willie). This control valve can be set to operate in any one of three control actions proportional, reset, or derivative. Following the control valve, the hot products are directed to a water cooled high pressure condenser. Here they are cooled to ambient conditions before being sent to a holding vessel for GC andysis. 

Regenerator flue gas left the top of regenerator through porous stainless steel filters to pressure control valve PRC-6, to an orifice, and a sample tap. From this point the flue gas could be vented, as shown on the flow sheet for nitrogen-air once-through... 

A controller opens and closes the pressure control valve at the gas outlet to maintain desired vessel pressure. Normally, horizontal separators are operated half full of liquid to maximize the gas-liquid interface area. 

---