Pressure tests and leak detection

Installation

Equivalent pressure drops

To correctly determine the size of the liquid and discharge lines for connection on site, it is first necessary to establish the equivalent pressure drops for each line, comprising the additional flow resistances, from bends, valves, etc. As a first approximation, we can estimate the equivalent pressure drops at 1.5 times the piping length.

Size of the liquid line

The standpipe must not be more than 5 m above the air-cooled condenser base. It is not necessary to slope the liquid line. It is recommended to have a line diameter as small as possible, while maintaining an acceptable pressure drop so as to minimize the refrigerant charge (length and maximum pressure drops defined above).

Determine the size using the following criteria:

1.Operating conditions with full load

2.Maximum pressure drops of 100-kPa

3.Liquid speed not exceeding 3 m/s (to prevent liquid shocks)

In normal operating conditions (suction temperature 4.5°C, condenser air inlet temperature 35°C or condensation temperature of 52°C), the liquid leaving the condenser is sub-cooled by approximately 10°C.Take this value as a basis to determine the maximum permitted pressure drops, and use it to calculate the liquid line pressure drops.

Discharge line

Install them so as to obtain a gas speed in the horizontal and vertical lines making it possible to carry along the compressor oil. Determine the dimensions of the suction line using the following criteria:

1.2.5 m/s (minimum) in the horizontal parts

2.5.0 m/s (minimum) in the vertical parts

3.Maximum speed 20 m/s

The minimum slope of the suction line to the condenser must be 5%. Isolate refrigerant fluid lines from the building to prevent the vibrations normally generated by the ducts from being transmitted to the building's structure. Also avoid bypassing the unit's isolation system by fixing the refrigerant fluid lines or the electrical ducts very rigidly. Any vibrations may be propagated into the building via rigid piping or lines.

WARNING

During these operations, take the following precautions:

1.Do not use oxygen or acetylene instead of the refrigerant fluid and nitrogen to detect leaks.This may cause a violent explosion.

2.Always use the expansion valve, safety valves and manometers to control the test pressure in the system. Excessive pressure may cause piping to rupture, damage the unit or cause explosion resulting in personal injury.

Carry out the liquid line and hot gas line pressure tests using the standards in force.The test pressure applied to the liquid line and the discharge line must comply with local regulations. Insert enough refrigerant fluid into the circuit to obtain a pressure of 1 bar.

By injecting dry nitrogen using a pump, increase this pressure to

7 bars. Look for leaks in the entire system using a detector.

If leaks are detected, evacuate the fluid from the system and repair the defective component. Repeat the test process to check the repair is watertight.

RLC-SVX03A-E4