PPCH™ OPERATION AND MAINTENANCE MANUAL
© 2009 DH Instruments, a Fluke Company
Page 14
2.3.9
CONNECTING TO OTHER DEVICES
ALWAYS use external tubing and fittings rated for pressure equal to or greater than the
maximum pressure PPCH will be used to generate.
The PPCH
TEST
port is a DH500 female fitting.
DH500 is a gland and collar type fitting for 1/4 in. (6.35 mm) coned and left hand threaded
tube. DH500 is equivalent to AE F250C, HIP HF4, etc.
DH500 fittings are rated for working pressure up to 500 MPa (72 500 psi). Be sure to use
stainless steel tubing rated for your maximum operating pressure with the DH500 fittings.
2.3.9.1
INSTALLING A LINE FILTER TO PROTECT THE PPCH
PPCH uses pressure shutoff valves that are needle valves that close by the
metal to metal contact of the needle in its seat. These valves can be damaged
by hard particles. If the test system to which PPCH will be connected may
contain hard particles, such as metal shavings from a production process, a line
filter should be installed on the PPCH test port to prevent the particles from
entering the PPCH when reducing pressure. The filter should not be smaller
then 40 micron. DHI recommends high pressure filter kit p/n 402376.
2.3.9.2
CONNECTING TO AN RPM4 TO BE USED AS AN EXTERNAL
REFERENCE DEVICE
ALWAYS use external tubing and fittings rated for pressure equal to or
greater than the maximum pressure PPCH will be used to generate.
PPCH can be connected hydraulically and by RS-232 to one or two RPM4
reference pressure monitors to use up to four external Q-RPTs (two in each RPM4)
as external reference pressure measurement devices (see Section 3.2.5).
The PPCH then manages communications and other RPM4 functions to
integrate the RPM4 measurement capabilities into the PPCH system.
The user
is responsible for setting up hardware and following procedures to isolate
lower pressure Q-RPTs from possible overpressure if pressures higher
than the Q-RPT maximum are generated..
PPCH and RPM4 do not have
hardware provisions for isolating external Q-RPTs from the
TEST
circuit.
As a general rule, making the hydraulic connection between the PPCH TEST
port and the remote Q-RPT as direct as possible favors good pressure control. As
distance, volumes and restrictions between the PPCH TEST port and the remote Q-
RPT increase, the possibility of difficulty with pressure control when using the
external Q-RPT increases.
