Manual Airwell MFH - Mobile (page 7 of 20) (English)

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exposed while charging, recovering or purging the system;

That there is continuity of earth bonding.

7.Repairs to sealed components

1)During repairs to sealed components, all electrical

supplies shall be disconnected from the equipment being

worked upon prior to any removal of sealed covers, etc. If it

isabsolutely necessary to have an electrical supply to

equipment during servicing, then a permanently operating

form of leak detection shall be located at the most critical

point to warn of a potentially hazardous situation.

2)Particular attention shall be paid to the following to ensure

that by working on electrical components, the casing is not

altered in such a way that the level of protection is affected.

This shall include damage to cables, excessive number of

connections, terminals not made to original specification,

damage to seals, incorrect fitting of glands, etc.

Ensure that apparatus is mounted securely.

Ensure that seals or sealing materials have not degraded

such that they no longer serve the purpose of preventing the

ingress of flammable atmospheres. Replacement parts shall

be in accordance with the manufacturer's specifications.

NOTE: The use of silicon sealant may inhibit the

effectiveness of some types of leak detection

equipment. Intrinsically safe components do not have to

be isolated prior to working on them.

8.Repair to intrinsically safe components

Do not apply any permanent inductive or capacitance

loads to the circuit without ensuring that this will not

exceed the permissible voltage and current permitted for

the equipment in use. Intrinsically safe components are

the only types that can be worked on while live in the

presence of a flammable atmosphere. The test apparatus

shall be at the correct rating. Replace components only

with parts specified by the manufacturer. Other parts may

result in the ignition of refrigerant in the atmosphere from

a leak.

9.Cabling

Check that cabling will not be subject to wear, corrosion,

excessive pressure, vibration, sharp edges or any other

adverse environmental effects. The check shall also take

into account the effects of aging or continual vibration

from sources such as compressors or fans.

10.Detection of flammable refrigerants

Under no circumstances shall potential sources of ignition

be used in the searching for or detection of refrigerant

leaks. A halide torch (or any other detector using a naked

flame) shall not be used.

11.Leak detection methods

he following leak detection methods are deemed

acceptable for systems containing flammable refrigerants.

Electronic leak detectors shall be used to detect flammable

refrigerants, but the sensitivity may not be adequate, or

Warnings(for using R290/R32 refrigerant only)

may need re-calibration. (Detection equipment shall be

calibrated in a refrigerant-free area.) Ensure that the

detector is not a potential source of ignition and is suitable

for the refrigerant used. Leak detection equipment shall be

set at a percentage of the LFL of the refrigerant and shall be

calibrated to the refrigerant employed and the appropriate

percentage of gas (25 % maximum) is confirmed. Leak

detection fluids are suitable for use with most refrigerants

but the use of detergents containing chlorine shall be

avoided as the chlorine may react with the refrigerant and

corrode the copper pipe-work. If a leak is suspected, all

naked flames shall be removed/ extinguished. If a leakage

of refrigerant is found which requires brazing, all of the

refrigerant shall be recovered from the system, or isolated

(by means of shut off valves) in a part of the system remote

from the leak. Oxygen free nitrogen (OFN) shall then be

purged through the system both before and during the

brazing process.

12.Removal and evacuation

When breaking into the refrigerant circuit to make repairs

or for any other purpose conventional procedures shall be

used. However, it is important that best practice is followed

since flammability is a consideration. The following

procedure shall be adhered to:

Remove refrigerant;

Purge the circuit with inert gas;

Evacuate;

Purge again with inert gas;

Open the circuit by cutting or brazing.

The refrigerant charge shall be recovered into the correct

recovery cylinders. The system shall be flushed with OFN

to render the unit safe. This process may need to be

repeated several times. Compressed air or oxygen shall

not be used for this task.

Flushing shall be achieved by breaking the vacuum in the

system with OFN and continuing to fill until the working

pressure is achieved, then venting to atmosphere, and

finally pulling down to a vacuum. This process shall be

repeated until no refrigerant is within the system. When

the final OFN charge is used, the system shall be vented

down to atmospheric pressure to enable work to take

place. This operation is absolutely vital if brazing

operations on the pipe-work are to take place.

Ensure that the outlet for the vacuum pump is not close to

any ignition sources and there is ventilation available.

13.Charging procedures

In addition to conventional charging procedures, the

following requirements shall be followed.

Ensure that contamination of different refrigerants does

not occur when using charging equipment. Hoses or lines

shall be as short as possible to minimise the amount of

refrigerant contained in them.

Cylinders shall be kept upright.

Ensure that the refrigeration system is earthed prior to

charging the system with refrigerant.

Label the system when charging is complete (if not already).

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Airwell MFH - Mobile Manual

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