Saturday, January 8, 2011

【 Weak current College 】 ammonia refrigeration systems of safety devices and safety check 】

Ammonia refrigeration systems of safety devices and safety checks

Summary: in ammonia refrigeration management and operations personnel have refrigeration system in the basics of security appliance, a timely check and exclusions refrigeration system of insecurity, on the prevention of accidents, the realization of safe production has important practical significance.
Keywords: ammonia refrigeration safety devices require ▲
1 of ammonia refrigeration systems and safety devices
Ammonia refrigeration systems commonly used key security appliance with safety valve, pressure gauges, thermometers, ammonia liquid, emergency release ammonia, pressure controllers, pressure controllers and safety leave cover, etc.
1.1 safety valve
Ammonia refrigeration equipment generally use Spring safety valve, which is when the cooling system pressure exceeds the limits, the valve is opened automatically, so that ammonia discharge through automatic safety valve, thereby protecting the safety of equipment and personnel. Safety valve installed in the ammonia compressor, connected suction and exhaust pipe when the suction pressure difference to automatically turn on when 1.6MPa for exhaust gases to the suction side side. Two-stage compressor (cylinder) in the pressure relief valve on, when the suction side pressure difference as to 0.6MPa should also be automatically opened. In accordance with the provisions of ammonia refrigeration system pressure vessel must also be installed and the devices conform to the safety valve. Condensing pressure of a pressure vessel of its safety valve set pressure for 1.85MPa, low-voltage equipment safety valve set pressure for 1.25MPa. Installation in front of the stop valve safety valve should be on for that lead. Safety valve for pressure pipe should be higher than the ammonia compressor room canopy 1m above; a condenser operating platform 3m above. Ammonia refrigeration systems safety valve diameter selection according to the following formula:
-D1-compressor valve diameter; 0.9 constant; V to compressor discharge capacity, m3/h.
-Safety valve diameter D2 as containers; 8 is a constant; D to container diameter, m; L-container length, m.
At present, in the refrigeration systems of ammonia pump circuit and intercooler, widely used in automatic by-pass valve is spring safety valve of a particular form, also played the role of security protection, that is, when the pressure exceeds the set value, the valve automatically turn on, bypass buck features.
1.2 monitor
Ammonia pressure gauge, thermometer and level gauge is a guarantee for the safe operation of ammonia refrigeration systems indispensable monitor. System in each of the ammonia compressor suction side, all pressure vessel and ammonia pumps, oil pumps and other equipment shall be fitted with appropriate ammonia pressure gauge. Due to ammonia on corrosion of copper and other metals have, ammonia pressure gauges must not be used in place of other pressure gauge, you must have the certificate of conformity and manufacturer of seals. The range should be greater than the maximum working pressure of 1.5 times less than the maximum working pressure of 3 times, the accuracy may not be lower than level 2.5. Thermometer settings in ammonia compressor suction side, seal-side, distribution points, heat pipe of station Assembly to observe and record the operating condition of the system. To grasp the changes of liquid within a container, storing ammonia, intercooler, ammonia liquid separator, and other equipment shall be equipped with liquid level gauge. Glass level meter use is higher than the maximum working pressure of the pressure resistance of glass tube and metal protection cover, automatic block device, such as the use of plate glass level meter is better.
1.3 emergency release ammonia converter
Ammonia refrigeration systems equipped with emergency release ammonia is to prevent the engine room fire and other accidents during the explosion of ammonia storage container. Emergency release ammonia with many small holes drilled on imports of tube and high-pressure liquid barrels, evaporator. When an emergency, ammonia liquid inlet valve inlet valve and, in the open so that ammonia liquid and water dilution by outlet discharge into the sewer. Emergency release ammonia does not work, you should periodically check the valve and connecting pipes to guarantee smooth.
1.4 pressure controller
Pressure controllers and pressure relays, for ammonia refrigeration equipment of one of the important electrical switches, its working principle is based on the bellows gas tank to engine room, after receiving pressure signal so that the resulting displacement of bellows gas tanks to promote contacts and broken, control purpose of protection. Pressure controller-high-voltage and low-voltage in two parts, you can individually or combined into a whole. Pressure controllers and pressure bellows connected to ammonia compressor-way valve bypass hole, when refrigeration system discharge pressure higher than the normal value, the controller action, cut off the motor power. Low pressure bellows connected to ammonia compressor suction-side way valve with bypass hole, it will also lower than the normal value of inspiratory pressure and automatic cutting motor power. Pressure controllers and pressure parts of the set pressure 1.65 ~ 1.7MPa, low-voltage part of the set pressure: better than the lowest 5 ° c evaporation temperature and low pressure.
1.5 pressure controller
Ammonia compressor running process, the relative motion parts need certain pressure lubricant continuous lubrication and cooling. As part of oil pressure too low, causing poor lubrication machine damage. Therefore, you should install pressure controller (pressure differential relays) oil pressure control. In ammonia compressor pressure controller installed on his high and low pressure gas-box corrugated pipe through the tubes andthe oil pump connecting the tubing and the compressor suction pipe connections, it accepts a lubricating pump discharge pressure and compressor suction pressure (crankcase pressure) two pressure signal. When the pressure difference is less than the minimum circuit breaker pressure 0.15MPa, the controller switches the compressor power shutdown action. In addition, the pressure differential controller can also be used as a water protection and the protection of the pump dry run protection device.
1.6 filter dryers
Ammonia vapour compression refrigeration system is a demanding sealing system. Which is neither allowed to air, water, metal dust, nor allow any dirt, otherwise it may cause damage or dirt plugging machines, ice jam, etc. Therefore, not only the compressor intake side, fuel system to install filters, but also in liquid barrels and throttle valve on the pipe between the need to retrofit dryers and filters.
1.7 security leave cover emergency button
Ammonia compressors each cylinder exhaust parts are fitted with a safety belt buffer spring holiday cover, when cylinder subjected to hydraulic hammer or the impact of mechanical objects, you can top up fake cover to prevent damage to the cylinder or cylinder head explode. In order to advancePreventing incidents in the engine room doorway or lateral convenient location shall be cut off the ammonia compressor power emergency button. This button should be located private line, with obvious signs that can stop all compressor operation. If the machine control panel is set to master control room, each machine to an additional button next to the switch.
1.8 other safety devices
Ammonia compressor pressure exhaust and ammonia pumps out liquid pipe valve, condenser and liquid barrels with voltage between the pipe and so also for ammonia refrigeration system frequently used safety devices. Automatic control of compressors are equipped with exhaust overheating protection, motor overheating protection, temperature controller, and are equipped with anti intercooler and circular liquid barrel level too high a protective device, once the situation is not normal to automatically.
2 ammonia refrigeration system security check contents and requirements
On the daily ammonia refrigeration system strengthening of security checks, maintenance, and management to keep equipment in good technical condition, to achieve the purpose of the safe and efficient operation.
Ammonia refrigerating systems, safety inspection of the main content and requirements are as follows; (1) of the compressor should be no rap. Ammonia compressor operates normally, except the intake and exhaust valve slice up and down lift and regularly issued clear sound, should not have any other non-normal percussion sound. (2) exhaust pressure and suction (row) gas temperature must be properly. Ammonia compressor pressure exhaust pressure must not exceed 1.5MPa, compression ratio equal to or less than 8. Suction temperature: single-or dual-class machine LP cylinder than evaporation temperature high: 5-15¡æ, two-stage machines generally in high pressure cylinder-5 to 5 ° c. Exhaust gas temperature: 80 single-stage machine should be ~ 150 ℃, the low pressure cylinder two-stage machines should be 60 ~ 90 ° c, high pressure cylinder in 70-120 degrees centigrade. (3) crankcase oil surface is correctly positioned. When one sees the hole should be held in the following as the hole 2/3 to 1/Visual hole 2 range. Sealing device is not oil penetration. Lubricating oil should not be sparkling, to identify causes, processed in a timely manner. (4) oil pressure, oil temperature is moderate. The serialization of the ammonia compressor oil than Crankcase gas pressure high 0.15 ~ 0.3Mpa, other use of low-speed gear oil pump compressors should 0.05 ~ 0.15Mpa. Because of the oil temperature is too low, the viscosity is too large to overheat and lubricating properties, crankcase oil temperature is generally within 45-60 ° c, notmore than 70 ° c, oil pump and oil temperature is below 5 ° c. (5) compressor parts temperature without exception. Bearing temperature is 35 ~ 60 ℃. Sealing temperature must not exceed 70 ° c, the compressor other friction parts temperature must not exceed the room temperature of 25 ~ 30 ℃. Also note that in addition to the suction valve should open dry cream, cylinder head, cylinder and crankcase should frosting. (6) the container level. Such as high-pressure liquid barrel level should remain in the volume of 30% to 80%; liquid level should control the intercooler in meter height of 50% and higher than the intake pipe mouth more than 150 ~ 200mm; recycling barrels of liquid level maintain barrel high 1/3 or so, not more than 1/2; set oil for oil volume should not exceed 70% of its volume. In normal circumstances should no ammonia liquid of low pressure liquid barrels, if liquid reaches 30% should be flowing. (7) equipment pressure, temperature changes, to ensure effective security of the refrigeration system. Normally, the condensing pressure and condensing temperature, evaporation pressure and evaporation temperature is correspondence. Condensing pressure, temperature, with cooling water temperature and water conditions. Condensation temperature lower than 40 ° c, higher than the condenser outlet temperature 3 to 5 ° c, maximum condensing pressure shall not exceed 1.5MPa, evaporation pressure, temperature, with cooling temperature requirements, when evaporation to 0 ° c and-15 ° c,-28 ° c,-33 ° c, the corresponding evaporation pressure respectively 0.44MPa, 0.24MPa, 0.13MPa and 0.11MPa. (8) refrigeration system all devices connecting pipe sealing performance good, no release of ammonia. Pipeline filter not chills, no dew and frost; throttle valve into the fluid end no frost, but the lower valve body and fluid-a thin layer of soft frost. (9) the fan and motor revolution steady, cooling water circulation pump is working properly, the water cycle pipe and tank without serious leakage. (10) pressure controllers, pressure controllers and temperature controllers and other safety devices technology in good condition, properly adjusted, the required pressure (and temperature) numeric range can play a protective effect of automatic control. The ammonia pressure gauge indicating the correct pointer stability. (11) on refrigeration system using ammonia safety valve, manometer, thermometer, protection switch, and so should periodically verify. Which safety valve, manometer ammonia at least send a legal departments check (check with leaded), ensure that sensitive and reliable, its accuracy.

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