MPC1-1000 and MPC1-3000 User’s Manual
There are four possible leak conditions:
•
A leak causing a pressure increase when system pressure is above atmosphere
•
A leak causing a pressure decrease when system pressure is above atmosphere
•
A leak causing a pressure increase when system pressure is below atmosphere
•
A leak causing a pressure decrease when system pressure is below atmosphere
A common reaction to a system leak is to close a particular valve more tightly. Although a valve may
not have been completely closed, care should be used when attempting to do so.
Repeatedly overtightening a valve may result in premature failure.
If a procedure requires you to tighten a leaky fitting, there are two precautions that need to
be observed. First, never tighten a fitting while it is under pressure. If pressure is in the system and
the fitting should fail while tightening it, there is a possibility of injury. Second, do not overtorque the
compression type fittings that are inside the MPC1. Overtorquing these fittings will damage them
requiring their replacement.
5.2.1
PRESSURE INCREASE LEAK (ABOVE ATMOSPHERE)
Only three conditions within the MPC1 can cause this type of leak:
1. A damaged or improperly closed test inlet valve (1) when a pressure source is
connected.
2. A leaking VV piston O-ring.
3. A leaking or improperly closed equalization valve (3).
1. is the most probable cause. Check if the valve is properly closed, use caution not to
overtorque the valve. If an upward leak is still present, remove the source pressure from the
supply connection and observe conditions. If pressure begins to drop, use a leak detection
liquid at the supply fitting. If bubbles are present, replace or repair the test inlet valve.
2. and 3. can only cause an upward leak if the pressure in the front chamber of the VV is
above that in the test circuit. Generate a pressure in the front chamber by closing the
equalization valve (push in) and rotating the VV knob counter-clockwise.
The pressure in the test circuit will decrease. Wait for pressure to stabilize. If pressure rises,
check to see if the equalization valve is properly closed. If pressure continues to increase,
open equalization valve. Wait for pressure to stabilize. If pressure stops increasing,
have VV serviced.
© 2001 - 2007
DH Instruments, a Fluke Company
Page 16
