7/31/2019 Shrink Fitting - Liquefied Nitrogen

1/3

Offshore

SHRINK FITTINGUSING

LIQUEFIED NITROGEN

PROCEDURE

7/31/2019 Shrink Fitting - Liquefied Nitrogen

2/3

OffshoreShrink fitting of parts using liquefied nitrogen procedure

D:\Training\Training & QC Procedures\Assembly\Shrink fitting - Liquefied Nitrogen.doc

Page 2 of 3

Rev.2

1.0 INTRODUCTION1.1 Under normal condition, parts to be fitted can be installed with the aid of an

industrial press and lubrication. Some with lesser tolerances can be installed using

hammer.

1.2 However, for ease of parts installation under very close tolerances, freeze-fittingwith the use of liquid nitrogen provides a good alternative.

1.3 Due to its extremely cold condition, extra precautions and steps must be used toaccomplish the task. Bare skin coming in contact with liquefied nitrogen and the

chilled surface can cause severe BURNS!

2.0 PARTS TO BE REQUIRED2.1 a) Large metal container

b) Rags

c) Container lid (loose fitting)

d) Cardboard & thermal wool

e) Duct tape/ Masking tape

f) Wood blocks

g) Canvas gloves

h) Hard soled shoes

i) Safety goggles

j) Liquid nitrogen

k) Outside & inside micrometer

3.0 PROCEDURE3.1 Use a large container or drum enough to immerse the liquid nitrogen of the parts to

be installed.

3.2 Use water to rinse out the inside of the drum surface. Remove traces of oil,varnish, wax and other foreign substances with a clean rag.3.3 The container or drum should have a loose fitting lid that should prevent the escape

of the nitrogen gas during the immersion process.

3.4 Wrap the external metal container sides with a curved sheet of cardboard line withthermal wool from top to bottom with duct tape. The cardboard and thermal wool

will serve as insulation to the liquefied nitrogen.

3.5 Place the container or drum on some blocks of wood and test its stability. This is toensure that the container or drum does not topple with the liquefied nitrogen during

the immersion process.

7/31/2019 Shrink Fitting - Liquefied Nitrogen

3/3

OffshoreShrink fitting of parts using liquefied nitrogen procedure

D:\Training\Training & QC Procedures\Assembly\Shrink fitting - Liquefied Nitrogen.doc

Page 3 of 3

Rev.2

3.6 Wear safety goggles and canvas working gloves. No bare feet are allowed, alwayswear hard-soled safety shoes. Pour enough liquid nitrogen into the metal container

to cover enough the height plus 50mm of the part to be fitted.

3.7 Wait for a minimum one hour to one-hour hours for the part to completely chilland contract. While waiting, take a measurement of the inside diameter and record

the dimensions with a pen and paper.

3.8 After the chilling period, use a canvas gloves to remove the part. Quickly measurethe outside diameter and record the dimensions with a pen and paper.

3.9 Determine if the bearing has shrunk enough to fit into the bearing housing bycomparing both measurements. The outside diameter reading should be less thanthe internal diameter. If adequate shrinkage has occurred, place the part inside the

internal hole, pushing it in until it fully engage.