Labconco Open Combination (Macro) Kjeldahl Systems 21237 Series - Manual (Page 15)

Chapter 2: Installation
Product Service 1-800-522-7658 12
WARNING: Acid resistant duct must be used on the exhaust connection on
your Kjeldahl Apparatus.
(Duct Area in Square Feet) x (Average Airflow Velocity in feet per minute)
= (Air Volume CFM)
(Pi) radius² X 117 FPM = 25 CFM
The exhaust stack rising from the blower exhaust connection must be vented to
the outside atmosphere. A 6" diameter duct is sufficient for carrying the fumes a
distance not exceeding 60 feet. In estimating the duct length count each 90°
elbow as 12 feet and add to the straight length total of duct for the duct system. If
the duct system exceeds 60 feet in equivalent length, it may be necessary to
increase the duct size to compensate for the friction loss generated by this
additional length.
Highly corrosive fumes produced from boiling sulfuric acid will flow through
the ductwork, so acid-resistant duct must be used. Polyvinyl chloride (PVC)
or fiberglass duct is recommended. The exhaust duct work must be supported
independent of the Kjeldahl System to avoid distortion of the blower housing.
Digestion Rack Drip Shield
The digestion heaters are located in a drip shield and constructed of stainless steel
which is resistant to acid attack. Liquid acid spills that occur can be drained to an
acid resistant container with the drip tube located on the left side of the digestion
rack.
Blower Acid Drip Tube
and
Digestion Rack Drip Tube
Figure 2-7