Getting Started
MedWeld 4000 Operator’s Guide
Modified: 9/17/08
xvi
M-032116 Programs #T03300, #T02300 and #T02400
SCRs with Hose
Running Between
Tangs at 480 VAC.
The following warning applies ONLY to SCRs which have the water
cooling hose running between tangs at 480 VAC (non-isolated).
WARNING!
REMOVE POWER from the SCR if the
cooling water is not flowing and the
resistivity of the water is less than 2,000
ohms/cm @ 25
°
C, or conductivity is
greater than 500
μ
Siemens @ 25
°
C.
If water circulation (in hosing between tangs) stops or is interrupted
while the power is on, leakage current through the water in the hose
between the SCR tangs will cause gas bubbles to form. Current will arc
across these voids, weakening or destroying the hose. Putting the water
into circulation again develops pressure in the cooling circuit,
consequently causing the hose to rupture.
Therefore, WTC does NOT
recommend the use of water savers with these SCRs.
When magnetic contactors are used, they remove power from the SCR
module and prevent destruction of the hose. If cooling manifolds are
used (rather than hose), leakage current in the water can cause the same
destructive action to occur while power is being applied. This can
destroy the cement holding the manifold together, resulting in serious
water leaks. (WTC’s warranty specifically EXCLUDES such failures.)
Hoses
If a cooling hose (for non-isolated SCRs) needs replacing, use a certified
non-electrically conductive hose. Its inside diameter must NOT exceed
3/8”. The hose between SCR tangs must be
at least
18 inches long
across the power voltages, where the SCR tangs are directly cooled.