Impulse Piping Connection Examples - YOKOGAWA EJX110A Installation Manual

Ejx series and eja-e series differential pressure and pressure transmitters

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(4) Temperature Difference Between Impulse

Piping (for differential pressure

transmitters)

If there is a temperature difference between the high

and low impulse lines, the density difference of the fluids

in the two lines will cause an error in the measurement

pressure. When measuring flow, impulse lines must be

routed together so that there is no temperature difference

between them.

(5) Condensate Pots for Steam Flow

Measurement (for differential pressure

transmitters)

If the liquid in the impulse piping repeatedly condenses

or vaporizes as a result of changes in the ambient or

process temperature, this will cause a difference in the

fluid head between the high pressure and low pressure

sides. To prevent measurement errors due to these head

differences, condensate pots are used when measuring

steam flow.

(6) Preventing Wind Speed Effects in Very Low

Differential Pressure Measurement

(for differential pressure transmitters)

IMPORTANT

When using a differential pressure transmitter to

measure very low pressures (draft pressure), the low

pressure connection port is left open to atmospheric

pressure (the reference pressure).

Any wind around the differential pressure transmitter

will therefore cause errors in the measurement. To

prevent this, it will be necessary either to enclose the

transmitter in a box, or to connect a impulse line to

the low pressure side and insert its end into a wind

excluding pot (cylindrical with a base plate).

(7) Preventing Freezing

If there is any risk that the process fluid in the impulse

piping or transmitter could freeze, use a steam jacket or

heater to maintain the temperature of the fluid.

NOTE

After completing the connections, close the valves on

the process pressure taps (main valves), the valves at

the transmitter (stop valves), and the impulse piping

drain valves, so that condensate, sediment, dust and

other extraneous material cannot enter the impulse

piping.

<4. Installing Impulse Piping>

4.2

Impulse Piping Connection

Examples

Figure 4.6, 4.7, and 4.8 shows examples of typical

impulse piping connections. Before connecting the

transmitter to the process, study the transmitter

installation location, the process piping layout, and

the characteristics of the process fluid (corrosiveness,

toxicity, flammability, etc.), in order to make appropriate

changes and additions to the connection configurations.

Note the following points when referring to these piping

examples.

• If the impulse line is long, bracing or supports should

be provided to prevent vibration.

• The impulse piping material used must be compatible

with the process pressure, temperature, and other

conditions.

• A variety of process pressure tap valves (main valves)

are available according to the type of connection

(flanged, screwed, welded), construction (globe, gate,

or ball valve), temperature and pressure. Select the

type of valve most appropriate for the application.

Liguid

Orifice

Tap valve

Union

or flange

Tee

3-valve

manifold

Drain valve

Drain plug

Figure 4.6