CASE POL 1 - POL Storage Tanks, Spark Generating Equipment, R. Thomas
Problem: Perpetuated myths in and around full storage tanks concerning spark
Symptom: Unnecessary costs and job delays while trying to obtain specialized
equipment. Injuries from using non-ferrous tools with less strength.
Collection of Facts: The American Petroleum Institute (API) has issued 3
safety documents covering the most commonly misunderstood areas concerning
API-PSD2214 - So called "non-sparking" (non-ferrous) tools offer no
more degree of safety over ordinary ferrous tools.
API-PSD2213 - Subscriber type (Bell) telephone systems cannot
generate enough power for fuel ignition and therefore are suitable
for Class 1, Group D atmospheres.
API-PSD2212 - Flashlights containing 3-cells and less cannot generate
enough power for ignition and therefore do not need to be explosion
Solution: The API safety documents are endorsed by NAVFAC and can be
referenced along with NAVFAC MO-230 when performing maintenance around fuel
CASE POL 2 - Thermal Expansion of Fuel, R. Thomas
Problem: Excessive pressures from thermal expansion of fuel downstream of
pressure control valve even though system contains a pressure relief valve
Bulging or bursting of pantograph fueling hose and leaking swivels.
Collection of Facts: When an angle pattern PRV is used to relieve thermal
pressure buildup from downstream to upstream around a block valve, the spring
relief setting on the valve can be misleading if the upstream piping remains
under pressure. The actual relief pressure becomes the value of the spring
plus the upstream pressure which is also acting on top of the valve.
example, if the PRV has a 150 psi spring setting and the upstream pressure
holds at 170 psi, relief will not occur until 150 + 170 = 320 psi is obtained,
which may damage the hose.
Solution: Either relieve to an unpressurized line (return line) with the PRV,
or incorporate a thermal relief check valve around the shut-off valve to
relieve upstream. In stainless steel, the relief valve runs about $400 while
the thermal relief check is about $50.