In the following, "NPT" means
National Pipe Threads.
Pressure Resistance - Pipe Threads
||Test Results (Test Fluid –10 wt. Motor
psi (72 MPa)
psi (69 MPa)
discontinued with no sign of leakage
psi (36 MPa)
psi (28 MPa)
psi (35 MPa)
psi (21 MPa)
Pressure Resistance - Straight Threads
In addition to NPT joints, Vibra-Seal products can also be
used to seal straight threads. Test performed on 3/8-16
straight threads, torqued up snug, exhibited excellent
sealing characteristics at oil pressures up to 600 PSIG
Tests performed on 1/2” cast iron NPT assembled
with 24 lb.-in. (2.7 N•m) seating torque yielded the
psi (.014 MPa)
discontinued after 1,000 hours with no sign of
psi (.207 MPa)
on 1/2” cast iron NPT at 100 PSIG (.69 MPa) hydrostatic
pressure after 30 days immersion in solvents indicated.
Weight Motor Oil
@ 98% Relative Humidity
Glycol and Water
Break-loose and Prevailing
parts will resist loosening because of the prevailing torque
characteristics shown below:
- Bolts — Grade
5, 3/8”-16 x 1-1/2” zinc phosphate and oil
- Nuts — Grade 2,
3/8”-16 zinc phosphate and oil finish.
||Prevailing Torque – 180°
lb-ins (40.7 N•m)
lb-ins (27.5 N•m)
lb-ins (0 N•m)
lb-ins (40.7 N•m)
lb-ins (19.8 N•m)
lb-ins (2.4 N•m)
The tension in the fastener
can be reasonably controlled by controlling the torque. For
any given fastener the torque tension relationship can be
stated as follows:
T = KDF
where T =
Torque, lb.-in. (N•m)
Nominal bolt diameter, in. (m)
Tension or clamping force, lbs. (N)
a universal constant for all sizes which can be established
(You can find safe stresses
for bolts in manufacturers’ fasteners specifications
or tool engineers’ handbooks).
NPT joint assembly is made
quicker and easier because of the lubricating ingredients
in Vibra-Seal products which resist thread galling. Line-up
adjustments can be made several hours after assembly without
loss of sealing quality. Joints can be easily disassembled
with regular tools even after years of service.
Vibra-Seal products have
exhibited the ability to be reused five times on 1/2” NPT
fittings which are torqued up snugly. After five uses, these
fittings still maintain 300 psi (2.0 MPa) hydraulic pressure
or burnt orange
K Values for Vibra-Seal® Sealants*
on Dry zinc phospate
on Zinc phosphate/oil
*3/8”-16 Grade 5
bolts with Grade 2 as received nuts. Example: Vibra-Seal
on 3/8”-16, Grade 5, zinc phosphate bolt:T = -.11 X
375 X 5000 = 206 lb.-in.
Vibra-Seal coatings are slightly basic and may stain or discolor some metals, especially those containing copper. However, the effect on performance of the sealant and staining of the metals is inconsequential.
Vibra-Seal coated fasteners and components are produced to order by Long-Lok. We can process your supplied parts, or we can supply complete products, including the basic fasteners or fluid fittings.
To order Vibra-Seal coated fasteners and components, or to request a quote, please call us and speak directly with one of our Sales Engineers.