Heath Consultants Heath Volume Corrector (HVC) - Manual (Page 8)

8
Pressure Connection
Connect the pressure (or gas) supply to the 1/4” NPT female connector located on the back of the HVC
325 housing. After piping is complete, check all connections to ensure that no leaks are present. Note:
For ease and isolation of testing, the HVC large mounting kit is recommended. This kit will assist in
future calibrations and inspection while the unit is in service.
Temperature Probe Installation
If equipped, the standard temperature probe (6” x 1/4” OD) should be installed into the appropriately
sized thermowell filled with a thermo conductive medium such as glycol or alcohol. Insert the
temperature probe into the thermowell through the standard 1/4” inch NPT male fitting (provided) until
the tip of the probe reaches the bottom of the well. Secure excess armor cable length of the probe.
It may be necessary to isolate the pressure and temperature connections to the pipeline, so as not to
disturb the cathodic protection system.
Electrical installation
NOTE: Refer to drawing MTM-308-1 for field wiring requirements for external power and
modem connections to maintain intrinsic safety.
The HVC 325 unit must be earth grounded to maintain safe operation and warranty.
The ground stud of the HVC 325 (located on the bottom left of the instrument) must be connected to a
suitable known external earth ground (usually a dedicated ground rod and NOT AC ground). All of the
major components in the HVC 325 are bonded together and connected internally to this ground stud.
It is required that grounding be performed, especially when an external modem and/or external power
supply (which requires a dedicated ground rod in close proximity to the safe area) is used. All cabling
connecting to the HVC 325 must be shielded with all shields tied to case ground.
For multiple device interconnections (modems, power supplies etc.) the ground stud of the HVC 325
must be tied directly to this same (safe area) ground rod rather than having a separate ground rod of its
own. It may be necessary to isolate the portion of the pipe that the HVC 325 is mounted to (with
insulating flanges) so as not to disturb the cathodic protection system.
The American Gas Association recommends grounding all electronic field devices to a driven ground
rod. This will help protect the device from transients including lightning and power surges on the
pipeline.
To reduce the possibility of “secondary” lightning strike damage (damage caused by static electricity
fields in the immediate area), the above precautions are required. However, these precautions cannot
prevent damage to an instrument that receives a “direct” lightning strike.
Battery Pack and Back-up Batteries
The HVC 325 units utilize (1) 1.5-volt, encapsulated “D” cell alkaline battery as its primary power
source. The pack supplied with the HVC 325 consists of an alkaline dry cell and a protection circuit.