Minimum pressurization temperature

STATE the two bases used for developing a minimum pressurization-temperature curve. 

EXPLAIN a typical minimum pressure-temperature curve including ... 

LIST the normal actions taken, in sequence, if the minimum pressurization-temperature curve is exceeded during critical operations. 

Plant operations are effected by the minimum pressurization-temperature curves. Personnel need to understand the information that is associated with the curves to better operate the plant. 

Minimum pressurization-temperature (MPT) curves specify the temperature and pressure limitations for reactor plant operation. They are based on reactor vessel and head stress limitations and the need to preclude reactor vessel and head brittle fracture. Figure 4 shows some pressure-temperature operating curves for a pressurized water reactor (PWR) Primary Coolant System (PCS). 

Minimum Pressurization Temperature (MPT) This is not an ASME Code requirement and is not stamped on the nameplate. This is the lowest temperature that will allow full pressurization for a vessel that has been subject to the long term effects of embrittlement. Embrittlement can be the result of temperature, hydrogen or irradiation. The temperature is either determined by calculation or testing methods. 

Briquets of mixed, finely divided oxide and carbon are heated to 1275—1400°C in a refractory container. The minimum pressure is about 40 Pa (0.3 mm Hg) for reduction at 1400°C. Lower pressures or higher temperatures cause excessive volatilisation of chromium. The result is a high purity, low interstitial product. 

In accordance with hsted standards, blind flanges may be used at their pressure-temperature ratings. The minimum thickness of nonstandard bhnd flanges shall be the same as for a bolted flat cover, in accordance with the rules of the ASME Boiler and Pressure Vessel Code, Sec. T11. 

Volume of vessel (free volume V) Shape of vessel (area and aspect ratio) Type of dust cloud distribution (ISO method/pneumatic-loading method) Dust explosihility characteristics Maximum explosion overpressure P ax Maximum explosion constant K ax Minimum ignition temperature MIT Type of explosion suppressant and its suppression efficiency Type of HRD suppressors number and free volume of HRD suppressors and the outlet diameter and valve opening time Suppressant charge and propelling agent pressure Fittings elbow and/or stub pipe and type of nozzle Type of explosion detector(s) dynamic or threshold pressure, UV or IR radiation, effective system activation overpressure Hardware deployment location of HRD suppressor(s) on vessel... 

External Combustor (experimental). The heat exehanger used for an external-combustion gas turbine is a direct-fired air heater. The air heater s goal is to achieve high temperatures with a minimum pressure decrease. It consists of a rectangular box with a narrow convection section at the top. The outer casings of the heater consist of carbon steel lined with lightweight blanket material for insulation and heat re-radiation. 

Temperature maximum and minimum Pressure at inlet and baek pressure, if any. 

Hoses to be indelibly marked to indicate the substances for which it is intended, its safe working pressure, proof-test pressure, date tested, and maximum or minimum service temperature. 

However, in the non-isothermal case the pressure is also high at low injection rates. This is because slow injection gives time for significant solidification of the melt and this leads to high pressures. It is clear therefore that in the non-isothermal case there is an optimum injection rate to give minimum pressure. In Fig. 5.28 this is seen to be about 3.0 x 10 m /s for the situation considered here. This will of course change with melt temperature and mould temperature since these affect the freeze-off time, //, in the above equations. 

Two properties of gases and vapors that may determine when an ignition can occur are the minimum ignition energy (MIL) and the antoignition temperature (AIT). These are discussed in Section 4.1.2 above. The MIL is a function of the pressure, temperature, and composition of a fuel-oxidant mixture. 

A number of gases may decompose (self-react) and propagate flames in the absence of any oxidant provided that they are above minimum conditions of pressure, temperature, and pipe diameter. Common examples are acetylene, ethylene oxide, and ethylene. Some, like acetylene, can decompose in a detonative manner, while ethylene cannot detonate in the absence of an oxidant, whatever the run-up length (CCPS 1993). Thus, detonation arresters must be used for acetylene, but deflagration arresters may be used for ethylene, even for in-line applications. 

Decomposition Flames Flames that are produced hy exothermic decomposition of certain gases in the absence of any oxidant, provided that they are above minimum conditions of pressure, temperature, and pipe diameter. Common examples include acetylene, ethylene oxide, and ethylene. 

The phase diagram for helium is shown here, (a) What is the maximum temperature at which superfluid helium-II can exist (b) What is the minimum pressure at which solid helium can exist (c) What is the normal boiling point of helium-I ... 

The phase diagram for carbon, shown here, indicates the extreme conditions that are needed to form diamonds front graphite, (a) At 2000 K, what is the minimum pressure needed before graphite changes into diamond (b) What is the minimum temperature at which liquid carhon can exist... 

Dost Minimum ignition temperature (°C) Minimum explosible concentration (g/l) Minimum ignition energy (m)) Maximum explosion pressure Maximum rate of pressure rise (psi/s) Maximum Notes oxygen cor>centration to prevent ignition (% by volume)... 

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