Ashcroft 1495 - Low Pressure Receiver Gauge Manual do Utilizador descarregar pdf (Página 17)

ions must pass before they reach the bourdon

tube. The dampener reduces the magnitude of

the pressure pulse thus extending the life of

the Bourdon tube and movement. This reduc-

tion of the pressure pulsation as “seen” by the

pressure gauge is generally evidenced by a

reduction in the pointer travel. If the orifice is

very small the pointer may indicate the aver-

age service pressure, with little or no indica-

tion of the time varying component of the

process pressure.

Commonly encountered media (e.g. – water

and hydraulic oil) often carry impurities

which can plug the orifice over time thus ren-

dering the gauge inoperative until the damp-

ener is cleaned or replaced.

Highly viscous media and media that tend to

periodically harden (e.g., asphalt) require a

diaphragm seal be fitted to the gauge. The

seal contains an internal orifice which damp-

ens the pressure fluctuation within the fill

fluid.

8.2 Throttle Screws & Plugs – These acces-

sories provide dampening for the least cost.

They have the advantage of fitting completely

within the gauge socket and come in three

types: (a) a screwed-in type which permits

easy removal for cleaning or replacement; (b)

a pressed in, non-threaded design and (c) a

pressed in, threaded design which provides a

highly restrictive, helical flow path. Not all

styles are available on all gauge types.

8.3 Ashcroft Gauge Saver – Type 1073

Ashcroft gauge saver features an elastomeric

bulb that fully isolates the process media

from the bourdon tube. In addition to provid-

ing dampening of pressure pulses, the bour-

don tube is protected from plugging and cor-

rosion. The space between the bulb and bour-

don tube is completely filled with glycerin.

Felt plugs located between the bulb and bour-

don tube are first compressed some amount to

restrict the flow of glycerin through an orifice

and thus provide a degree of dampening. The

greater the compression of the felts the

greater the degree of dampening.

.4 Ashcroft Pulsation Dampener – Type

1106 Ashcroft pulsation dampener is a mov-

ing pin type in which the restricted orifice is

the clearance between the pin and any one of

five preselected hole diameters. Unlike a sim-

ple throttle screw/plug, this device has a self-

cleaning action in that the pin moves up and

down under the influence of pressure fluc-

tuations.

8.5 Ashcroft Pressure Snubber – The heart

of the Type 1112 pressure snubber is a thick

porous metal filter disc. The disc is available

in four standard porosity grades.

8.6 Campbell Micro-Bean

– Type 1110

Micro-Bean is a precision, stainless steel, nee-

dle valve instantly adjustable to changing

conditions of flow and viscosity. A very slight

taper on the valve stem fits into tapered hole

in the body. The degree of dampening is easi-

ly adjusted by turning the valve handle. A fil-

ter is built into the Micro-Bean to help pre-

vent plugging.

8.7 Ashcroft Needle Valves – Type 7001 thru

7004 steel needle valves provide varying

degrees of dampening similar to the Campbell

Micro-Bean but with a less precise and less

costly adjustability. Like the Micro-Bean

these devices, in the event of plugging, can

easily be opened to allow the pressure fluid to

clear away the obstruction.

8.8 Chemiquip

Pressure Limiting Valves –

Model PLV-255, PLV-2550, PLV-5460, PLV-

5500 and PLV-6430, available with and with-

out built-in snubbers, automatically “shut off”

at adjustable preset values of pressure to pro-

tect the gauge from damage to overpressure.

They are especially useful on hydraulic sys-

tems wherein hydraulic transients (spikes)

are common.

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