Utah-94-721002-System-Manual.pdf - 第234页

lfmq=póëíÉãë lñÑç êÇ=fåë íêìãÉåí ë=m ä~ë ã~=qÉÅÜåçäçÖó== System Manual TK= iáèìáÇ=káíêçÖÉå= WARNING IF LIQUID NITROGEN FA CILITIES ARE NOT INST ALLED, OPERATED AND MAINTAINED CORRECTLY, DANGEROUS SITUATIONS CA N RESULT. …

System Manual lñÑçêÇ=fåëíêìãÉåíë=mä~ëã~=qÉÅÜåçäçÖó== lfmq=póëíÉãë

SKNKO= fåëí~ää~íáçå=çÑ=äçï=î~éçìê=éêÉëëìêÉ=Ö~ëÉë=EÉKÖK=pá`ä

I=_`ä

I=`

The low vapour pressure can lead to condensation in the gas supply lines, particularly at cold

points or when the gas passes into a cooler region. This condensation can result in a build up

of liquid in the gas pipe, usually at the low points or u-bends in the gas line, often leading to

instability of gas flow, especially if liquid condenses or flows into the MFC.

The low vapour pressure can also result in very low gas pressure if the gas cylinder is very

cold, e.g. if it is kept outdoors in the winter.

Therefore, it is important to adhere to the following guidelines:

(A) It is necessary to keep the gas cylinder indoors (in an extracted gas cabinet) to avoid

loss of line pressure when the outside temperature is cold.

However, do

NOT heat the gas cylinder with a heated jacket as this can cause

condensation problems when the gas passes into the cooler gas lines. Room

temperature is warm enough to provide sufficient vapour pressure.

(B) It is important to maintain a positive temperature gradient from the cylinder to the

MFC, or at least keep them at the same temperature. The simplest method is to

position the gas cabinet close to the gas pod, minimising the chances of temperature

differences, reducing the length of the gas pipe, and hence minimising the chances

of condensation. If this is not possible, then it is necessary to heat the gas lines by

the use of heater tape.

The MFC will also need to be heated. OIPT offers a heated MFC kit for these gases.

Alternatively, heater tape can be wrapped around the MFC. However, in this case, it

may also be necessary to detach the MFC from the backing plate to avoid heat loss

through the plate, and to cover the MFC in insulation material to avoid cooling from

air flow within the gas pod (from the gas pod exhaust).

It will then be necessary to set the MFC temperature hotter than the gas line

temperature, which in turn is hotter than the gas cylinder temperature. A typical set-

up might be MFC 40 °C or above, gas line 30-40 °C, and gas cylinder at room

temperature.

lines completely, and optimise the heater tape arrangement and temperature

setpoints before refilling the gas line.

(D) For SiCl

it is important to use a dedicated SiCl

MFC as this is designed specifically for

low-pressure condensable SiCl

operation.

Services Specifications

Printed: 6-Jan-06, 8:44 Page 15 of 22 Issue 16: April 05

lfmq=póëíÉãë lñÑçêÇ=fåëíêìãÉåíë=mä~ëã~=qÉÅÜåçäçÖó== System Manual

TK= iáèìáÇ=káíêçÖÉå=

WARNING

IF LIQUID NITROGEN FACILITIES ARE NOT INSTALLED, OPERATED AND MAINTAINED

CORRECTLY, DANGEROUS SITUATIONS CAN RESULT. THESE INTRODUCE RISKS OF:

A) HAZARDOUS PRESSURE BUILD-UP CAUSED BY THE BOIL-OFF OF LIQUID

NITROGEN, WHICH CAN RESULT IN AN EXPLOSION.

B) PERSONAL INJURY FROM TOUCHING PIPEWORK OR OTHER SYSTEM

COMPONENTS CARRYING LIQUID NITROGEN. THIS RISK CAN REMAIN EVEN

AFTER VENTING THE CHAMBER.

C) ASPHYXIATION CAUSED BY THE BOILED-OFF LIQUID NITROGEN REPLACING

OXYGEN IN THE SYSTEM ENVIRONMENT.

TKN= j~åÇ~íçêó=oÉèìáêÉãÉåíë=Ñçê=iáèìáÇ=káíêçÖÉå=ëóëíÉãë=

• Ensure that the Liquid Nitrogen installation is carried out in accordance with

local safety regulations. This includes the following:

(a) No part of the Liquid Nitrogen circuit can become blocked with ice

or other contaminants.

(b) Adequate precautions, e.g. pressure relief valves, are fitted to

prevent hazardous pressure build-up from boil-off of the Liquid

Nitrogen.

insulated, and covered to prevent personnel touching exposed

components.

• Ensure that the installation is inspected by a Specialist to confirm that it is

safe to use. Inspections must be carried out before the system is

commissioned and at regular intervals throughout its life.

• Pipework from the Dewar to the system must be adequately insulated and

connected to the system via a

” Swagelok connector.

Services Specifications

Issue 16: April 05 Page 16 of 22 Printed: 6-Jan-06, 8:44

System Manual lñÑçêÇ=fåëíêìãÉåíë=mä~ëã~=qÉÅÜåçäçÖó== lfmq=póëíÉãë

UK= bñíê~Åíáçå=

The following mandatory requirements describe the extraction systems

recommended by OIPT. While these recommendations may be regarded as “good

practice”, they are not a complete definition of the safety standards required when

handling toxic, corrosive or otherwise hazardous gases. It is the customer’s

responsibility to ensure that the installation meets all relevant local safety

regulations and OIPT accepts no responsibility in this respect.

For detailed information about the safety aspects of gas handling and pumping

systems, the customer should consult the relevant manufacturer/supplier of the

gases and pumps to be used.

UKN= j~åÇ~íçêó=êÉèìáêÉãÉåíë=Ñçê=oçí~êó=mìãé=Éñíê~Åíáçå=

The installation must provide a rotary pump exhaust extraction system which

matches the rotary pump exhaust and which conforms to local safety standards.

In particular, all fittings and pipework connected to the rotary pump exhaust must

be made from industry standard stainless steel in accordance with local safety

regulations.

Specialised equipment such as scrubbers and furnaces may be needed to dispose of

hazardous gases. The routing of the pump exhaust line must be arranged so that

condensates cannot flow back into the pump.

Note that there is a risk of damage from cross-contamination if rotary pumps share

one exhaust system. This applies whether the pumps are on the same system or on

different systems. Damage caused by any cross-contamination is not covered by the

system warranty.

Care must be taken to route mutually incompatible exhaust gases through separate

exhaust ducts. In particular, oxygen enriched exhaust gases should not be mixed

with exhausts from mineral oil pumps, otherwise, an explosion may occur.

UKO= j~åÇ~íçêó=êÉèìáêÉãÉåíë=Ñçê=d~ë=mçÇ=Éñíê~Åíáçå=

The gas pod must be connected to the customer's gas extraction system via a 100

mm diameter pipe collar to provide cabinet extraction with a minimum flow rate of

1 m

/hour (6-line gas pod) or 3 m

/hour (12-line gas pod), i.e. an extraction vacuum

of approximately 500 Pa relative to local atmospheric pressure is required. It is the

customer’s responsibility to ensure that the gas extraction system, including any

necessary gas sensors, meets local safety regulations.

Services Specifications

Printed: 6-Jan-06, 8:44 Page 17 of 22 Issue 16: April 05