Bettis Manual: J1-RT2 Rate of Drop Linebreak Detection System Service Manual | Bettis Manuals & Guides

Bettis Canada Ltd.
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Edmonton, Alberta, Canada T6E 5V2

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Service Manual

BETTIS J1-RT2

RATE OF DROP LINEBREAK DETECTION SYSTEM

CUSTOMER:

P.O.#:

W.O.#:

TYPE:

DATE:

EDMONTON

FACTORY SET: psi/min RoD @ psi P/L

SECTION PAGE

I GENERAL DESCRIPTION & INFORMATION .............. 2

II INSTALLATION AND START-UP . . . . . . ................. 4

III CALIBRATION AND TESTING ........................ 6

IV FUNCTION CHECK. ................................ 13

V TROUBLE-SHOOTING .............................. 16

VI MAINTENANCE PROCEDURES ....................... 18

VII DRAWINGS

- Outline Drawing .............................. FIG 3

- Schematic .................................. FIG 4

- J-1 Pilot Assembly ............................ FIG 5

- Manifold Assembly ............................ FIG 6

- Rate of Drop vs ∆P Calibration Charts ............. FIG 7

APPENDIX A: ALTERNATE PROCEDURES FOR SECTION III CALIBRATION

AND TESTING AND SECTION IV FUNCTION CHECK ..... 29

I-0057--.WPD/1

REV 6 1995-12-19

SECTION I GENERAL DESCRIPTION & INFORMATION

The Bettis J1-RT2 system is designed to automatically monitor a gas pipeline, and deliver a

pneumatic signal if a pre-determined rate of pressure drop is exceeded. The unit is typically

used to detect a pipeline break situation and signal a valve operator.

The system consists of a rate tank, J-1 differential pressure pilot, restrictor, check valve,

manifold assembly and associated tube, fittings, gauges and filters.

The system works as follows: when pipeline pressure is rising, gas flows through the check

valve and restrictor, into the rate tank. When pipeline pressure is falling, gas flows out of the

rate tank, back to the pipeline through the restrictor only. The restrictor resists the flow creating

a pressure drop which is sensed by the J-1 as differential pressure. The J-1 will send a

pneumatic signal if the differential pressure exceeds its calibrated setting. The greater the rate

of drop in the pipeline pressure, the greater the differential pressure across the J-1. The

following abbreviations will be used:

pipeline pressure P/L

rate of drop RoD

differential pressure ∆P

Normally, the pipeline will be operating at a steady or slowly changing pressure. When a

pipeline break occurs, the RoD at the J1-RT2 sensing point will depend on the distance to the

break. Greater distance to the break will decrease RoD at the sensing point. A compromise

must be made in adjusting the RoD setpoint. It must be as low as possible to detect remote

breaks, but not so low that normal pipeline pressure fluctuations will cause a false alarm.

As indicated earlier, the J-1 differential pressure pilot does not respond directly to RoD but to

∆P. The ∆P depends on RoD, but also on:

1. P/L: The RoD required to generate a given ∆P increases with higher P/L.

2. Time: After the initiation of a RoD due to a pipeline break the ∆P takes time to reach its

maximum value.

These dependencies are inherent in this type of system. The time delay in reaching the

maximum ∆P necessitates the following clarification:

P/L is the pipeline pressure occurring at the time that the maximum ∆P is developed, not the

pipeline pressure at the initiation of the RoD (refer to FIG 1). This time delay is apparent

and accounted for in the FUNCTION CHECK procedure (SECTION IV).

(i-0057--.wpd/2)

SECTION I GENERAL DESCRIPTION & INFORMATION - continued

Each combination of restrictor and rate tank size has a specific CALIBRATION CHART (Refer

to FIG 6), identified by a TYPE number which corresponds to the TYPE number stamped on

the unit name plate.

The CALIBRATION CHART maps the relationship between ∆P, RoD and P/L. The J-1 pilot is

calibrated to trip at a particular ∆P by adjusting the spring preload or changing springs. The

CALIBRATION CHART also indicates the ∆P ranges of the four J-1 springs which may be used

(stocked at the factory). The selection of restrictor is done at the factory based on the specified

RoD range and P/L operating range. Specific instructions for reading the required ∆P from the

CALIBRATION CHART are given in Section III (4. J-1 ∆P CALIBRATION).

The CALIBRATION CHARTS are for natural gas with a specific gravity (SG) of .67 and

temperature of 20bC. After correcting for SG and temperature, they will normally agree with

field data within ±20% (on RoD). The inaccuracy is due to manufacturing tolerances and the

fact that the chart P/L lines are adjusted from original data using air. Considering the above,

the recommended uses of the CALIBRATION CHARTS are limited to the following:

- Selection of the correct restrictor for an application (normally done at the factory).

- Initial J-1 pilot calibration (normally done at the factory), to be verified at final installation

using the FUNCTION CHECK procedure (Section IV).

- Illustration of performance characteristics for training, calibration or troubleshooting

purposes.

Use of the CALIBRATION CHARTS to verify FUNCTION CHECK data is not recommended as

it is complicated, (Corrections would generally have to be made for SG and temperature) and

unnecessary, (the data from the FUNCTION CHECK procedure, stands by itself as proof that

the system is operating to specification, provided the unit has been calibrated and tested per

Section III).

It is recommended that users establish their own baseline calibration records using the

procedures in Section III and IV and keep calibration records.

(i-0057--.wpd/4)

SECTION II INSTALLATION AND START-UP

GENERAL INFORMATION

The unit can be installed remote from or on the valve operator. The following preparations

are required:

1. Ensure the isolation valve on the pipeline is installed with take-off to top of pipeline to

allow liquids to drain back into the line.

2. Ensure that pipe and tube to be used is free of chips and debris.

3. Use minimum 1/4 NPT or 3/8 tube, with support adequate to prevent vibration and strain

on connections.

An additional pre-filter is recommended (Refer to Section VI, item 4). It should be installed

between the PIPELINE ISOLATION VALVE (FIG 4, item 101), and the customer supplied

isolation valve at the pipeline take-off.

CONNECTIONS (Refer to FIG 3)

When the J1-RT2 System is shipped pre-installed on the valve operator, customer

connections consist of:

- High pressure pipeline gas connection to PIPELINE ISOLATION VALVE (pipeline

connection "A", ¼ NPT female).

When the J1-RT2 System is shipped separately, customer connections, in addition to

above, include:

- Low pressure supply connection to J-1 pilot valve (supply connection "C", ¼ NPT

female, 150 psig max).

- Low pressure signal connection to J-1 pilot valve (signal connection "B", ¼ NPT female).

(i-0057--.wpd/5)

SECTION II INSTALLATION AND START-UP - continued

START UP (Refer to FIG 4)

1. OPERATION AND FUNCTION OF MANUAL VALVES

a. PIPELINE ISOLATION VALVE (item 101): This valve is normally open. Closing this

valve isolates the system from the pipeline.

b. RATE TANK DRAIN VALVE (item 107): This valve is normally closed and plugged.

Unplug and open to depressurize the J1-RT2 system or drain condensate.

2. START-UP

a. Check and close all manual control valves.

b. Open the main isolation valve on the pipeline (customer supplied).

c. SLOWLY open PIPELINE ISOLATION VALVE (item 101) to pressurize system.

d. When flow into the RATE TANK has stopped, the signal pressure gauge should

indicate if a signal is being applied to (or removed from) the valve operator control

package.

e. The Line Valve (item 2) should be able to be opened and it should remain open.

LEAK TEST ALL FITTINGS AND CONNECTIONS WITH SOAPY WATER.

(i-0057--.wpd/6)

SECTION III CALIBRATION AND TESTING

THREE REQUIREMENTS FOR CORRECT J1-RT2 OPERATION:

CORRECT J-1 PILOT CALIBRATION:

Verify using the J-1 ∆P CALIBRATION procedure in this section.

LEAK-TIGHT HIGH PRESSURE SIDE:

Verify using the PRESSURE HOLD TEST procedure in this section.

UNOBSTRUCTED RESTRICTOR AND FILTERS:

Verify using the PLUGGING TEST procedure in this section.

CALIBRATION AND TESTING PROCEDURES:

For routine calibration and testing, the following steps (1 to 7) are to be executed in

sequence.

NOTE: THESE PROCEDURES REQUIRE BETTIS CALIBRATION KIT, PART NO. 930-

980. REFER TO APPENDIX A FOR AN ALTERNATE PROCEDURE BASED

ON SIMPLIFIED EQUIPMENT. THIS SIMPLIFIED EQUIPMENT IS SPECIFIED

IN THE PROCEDURE AND MAY BE SUPPLIED BY THE USER.

1. DISARM SYSTEM

Isolate or disarm controls and equipment downstream of the J1-RT2 output signal to

prevent inadvertent operation or alarms (Follow applicable procedures and operating

instructions). Depending on where and how this is done, selected downstream controls

can be left active. The function of these controls can then be verified when J1-RT2

output signals are generated during the following procedures.

2. CHECK FOR EXTERNAL LEAKS:

While the J1-RT2 system is still pressurized, check for external leaks at all connections

using soapy water. Fix any leaks before proceeding.

(i-0057--.wpd/7)

SECTION III CALIBRATION AND TESTING - continued

3. SETUP TEST EQUIPMENT

SEE FIG 2, "SETUP FOR J1-RT2 CALIBRATION AND TESTING WITH CALIBRATION

KIT"

CAUTION: DISARM AND DEPRESSURIZE BEFORE ATTEMPTING SERVICE; Close

the PIPELINE TAKE-OFF VALVE and de-pressurize the system by opening

the RATE TANK DRAIN VALVE.

CAUTION: Ensure that contaminants (eg. dust, soapy water, etc.) do not enter at the

HIGH or LOW PRESSURE TEST CONNECTIONS.

a. Connect HIGH PRESSURE CONNECTION on CALIBRATION KIT PANEL to HIGH

PRESSURE TEST CONNECTION on the J1-RT2 MANIFOLD (3/8 tube fitting).

b. Connect LOW PRESSURE CONNECTION on CALIBRATION KIT PANEL to LOW

PRESSURE TEST CONNECTION on the J1-RT2 MANIFOLD (1/4 tube fitting).

c. Connect PIPELINE CONNECTION on CALIBRATION KIT PANEL to a PIPELINE

PRESSURE TAP (or between the PIPELINE TAKE-OFF VALVE and the PIPELINE

ISOLATION VALVE).

Ensure: 1. All CALIBRATION KIT PANEL valves are closed except the METERING

VALVE which should be near fully open.

2. GAUGE SELECTOR VALVE is set to FUNCTION CHECK.

3. All connections are made leak tight.

To pressurize system for leak checking connections:

- Open PIPELINE TAKE OFF VALVE and PIPELINE ISOLATION VALVE

- Open HIGH PRESSURE BLOCK VALVE

- Slowly open CALIBRATION PANEL NEEDLE VALVE allowing system to fill and

stabilize

To vent off:

- Close PIPELINE TAKE OFF VALVE

- Open RATE TANK DRAIN VALVE

- Open LOW PRESSURE BLOCK VALVE

(i-0057--.wpd/8)

SECTION III CALIBRATION AND TESTING - continued

4. J-1 ∆P CALIBRATION

a. Remove U-TUBE and install caps on fittings.

b. Open the LOW PRESSURE SIDE to atmosphere by fully opening the METERING

VALVE and the LOW PRESSURE BLOCK VALVE. Close the RATE TANK DRAIN

VALVE and PANEL NEEDLE VALVE. Set the GAUGE SELECTOR VALVE to the

SETPOINT CHECK GAUGE.

c. Open the HIGH PRESSURE BLOCK VALVE and slowly increase pressure on the

HIGH PRESSURE SIDE using the NEEDLE VALVE. Note the reading on the

SETPOINT CHECK GAUGE when the J-1 switches (ie. MICROVALVE toggles).

Close NEEDLE VALVE after J-1 switches.

d. Repeat test, vent the HIGH PRESSURE SIDE by closing the NEEDLE VALVE and

opening the RATE TANK DRAIN VALVE, and repeat procedure b and c above.

e. Compare the J-1 switch pressure to the required ∆P*.

f. Adjust the J-1 spring load if required (turn adjusting nut FIG 4, item 111) and repeat

steps b, c and d until switching occurs at the required ∆P. If the required ∆P is

outside the range of the J-1 spring, contact the factory for an alternate.

* If the required ∆P is unknown or not yet established, use the CALIBRATION CHART to

find the ∆P corresponding to the specified/desired rate-of-drop (RoD) and pipeline

pressure (P/L). (If the pipeline operates over a wide pressure range, a typical pressure

must be selected).

Use of CALIBRATION CHART to find ∆P: Find the specified/desired RoD along the

horizontal axis and trace a line upward to where it intersects the specified/desired P/L

line (interpolation between P/L lines may be required). From this intersection trace a

horizontal line to the vertical axis and read the ∆P value. Refer to comments on the

CALIBRATION CHART in Section I.

(i-0057--.wpd/10)

SECTION III CALIBRATION AND TESTING - continued

5. PRESSURE HOLD TEST

a. Ensure the PIPELINE ISOLATION VALVE is closed. Depressurize the system by

venting the RATE TANK (open the RATE TANK DRAIN VALVE). Disconnect the

hose from the PIPELINE PRESSURE TAP and PANEL PIPELINE CONNECTION.

Re-install plugs at both fittings.

b. If not done in step 4a then, remove the U-TUBE and install tubing caps on the

fittings. CAUTION: Ensure that contaminants (eg. dust, soapy water etc.) do not

enter at these fittings. Close the RATE TANK DRAIN VALVE and HIGH PRESSURE

BLOCK VALVE. CAUTION: Ensure that plugs have been installed leak tight. Check

with soapy water when the system is pressurized in step c. Set the GAUGE

SELECTOR VALVE to the SETPOINT CHECK GAUGE.

c. LOW PRESSURE HOLD TEST: Close the LOW PRESSURE BLOCK VALVE.

Pressurize the HIGH PRESSURE SIDE to 20 psi by opening the PIPELINE

ISOLATION VALVE (the flow through the check valve will require it to open and

reseat at low pressure resulting in a worst case test). Stabilize the pressure reading

for one minute then vent the LOW PRESSURE SIDE by opening the LOW

PRESSURE BLOCK VALVE (METERING VALVE near fully open). Monitor the

SETPOINT CHECK GAUGE for 3 minutes. The maximum allowable pressure loss is

10% of RoD over 3 minutes (eg. if RoD = 20 psi/min then allowable pressure loss

over 3 minutes is 2 psi or less).

d. HIGH PRESSURE HOLD TEST: Close the LOW PRESSURE BLOCK VALVE.

Pressurize the HIGH PRESSURE SIDE to 500 psi (or to available P/L if less) by

opening the PIPELINE ISOLATION VALVE. Stabilize the pressure reading for one

minute then vent the LOW PRESSURE SIDE by opening the LOW PRESSURE

BLOCK VALVE and metering valve is nearly full open. Monitor the SETPOINT

CHECK GAUGE for 3 minutes. The maximum allowable pressure loss is 10% of

RoD over 3 minutes (see example in step c above).

(i-0057--.wpd/11)

SECTION III CALIBRATION AND TESTING - continued

e. If the maximum allowable pressure loss rates are exceeded, there is a leak in the

HIGH PRESSURE SIDE which must be traced and fixed. A failure of the LOW

PRESSURE HOLD TEST is likely due to a faulty check valve. A failure of the HIGH

PRESSURE HOLD TEST is likely due to leaking tube fittings, valves or internal

leakage through the J-1 diaphragm or the check valve (refer to Section VI,

MAINTENANCE PROCEDURES). Depressurize the system by venting the RATE

TANK (open the RATE TANK DRAIN VALVE).

6. PLUGGING TEST

a. Ensure the PIPELINE ISOLATION VALVE is closed and the system is depressurized

(ie. the RATE TANK DRAIN VALVE is open).

b. Re-install the U-TUBE. Ensure that these tube connections are leak tight as they are

on the HIGH PRESSURE SIDE. Check with soapy water after the system is

pressurized. CAUTION: Use minimal torque when remaking U-TUBE connections to

extend tube life.

c. Close the RATE TANK DRAIN VALVE and LOW PRESSURE BLOCK VALVE.

Ensure the METERING VALVE is near fully open, the HIGH PRESSURE BLOCK

VALVE is closed and the GAUGE SELECTOR VALVE is on SETPOINT CHECK

GAUGE.

d. Pressurize the system to 300 psi by opening the PIPELINE ISOLATION VALVE.

Stabilize the pressure for one minute (If pressure will not stabilize, there is a leak in

the system which must be fixed before running the test. See item 5, PRESSURE

HOLD TEST).

e. Open the LOW PRESSURE BLOCK VALVE and simultaneously start TIMER.

f. Record pressure reading at 90 seconds and close the LOW PRESSURE BLOCK

VALVE.

g. Compare this to the appropriate MAXIMUM END PRESSURE value in the table

below. If the end pressure is above the maximum, there is plugging or obstruction of

the restrictor or filters (refer to Section VI, MAINTENANCE PROCEDURES).

(i-0057--.wpd/12)