Chapter 21 - Low Voltage And High Voltage Holiday Detection

Question 1

Low voltage (wet sponge) holiday detector are powered by batteries with output voltage ranging

Answer 1

From 5-120 V DC

Question 2

Describe low voltage (wet sponge ) holiday detectors?

Answer 2

Ground cable is attached directly to substrate
Sponge saturated with a solution of tap water/wetting agent
Maximum rate of 30cm /s (1liner ft/s) double stroke
Used on coating up to 500um ( 20mils)
May be used on concrete

Question 3

High voltage DC holiday detector types include

Answer 3

DC- Pulsed

DC- constant current

Question 4

Describe high voltage DC holiday detectors

Answer 4

Ground connection must be made direct to metal substrate (preferred) or indirectly when necessary eg to soil for pipeline measurement
Rule of thumb 100v / mil ( 4V/um)
Electrode rate of 0.3 m/s 1 ft/s in single pass according to NACE standard SP0188
Voltage output range from 800 to 60,000v

Question 5

The type of high voltage holiday detector used for concrete is a

Answer 5

High voltage DC constant current

Question 6

General types of holiday detectors include

Answer 6

Low-voltage DC
High-voltage DC
High-voltage AC