cashco 764P Manual de instalação, operação e manutenção - Página 9

Procurar online ou descarregar pdf Manual de instalação, operação e manutenção para Controlador cashco 764P. cashco 764P 14 páginas. Pneumatic pressure controllers

Imprimir página

2. Improper control valve action.

Possible Cause

A. Mismatch of pneumatic hardware.

B. Improper action; port "A" or "B"

connections are reversed.

3. Erratic Operation; Rapid Cycling.

Possible Cause

A. Insufficient PB

B. Improper air supply.

C. Pulsing process sensing.

D. Non-Correctible process dynamics.

4. Sluggish operation; slow action.

Possible Cause

A. Restricted flow(s).

B. Insufficient air supply.

C. Too much PB.

D. Improper range selection.

E. Too large actuator.

F. Use of alcohols, glycols in freezing

weather; dissolved lubricant on O-rings.

5. Calibration Erratic; frequent setpoint adjustments.

Possible Cause

A. Sensing diaphragm loose at screwed

connection to housing or adapter.

B. Bent sensing diaphragm.

C. Air supply debris.

IOM-764P / PD

A. Check bench set of actuator. Consider positioner or

booster.

B. Reference Tables 1 and 2 herin for desired action

and proper port; reverse as required.

A. Increase PB in 1/8 rev. increments by turning the needle valve

CCW. Reset setpoint as required (Max PB at 1-1/2 revs.).

B1. Supply pressure too high. Reduce airset output supply pres

sure to 15-18 psig.

B2. Air supply unsteady. Replace airset.

C1. Snub process needle valve as far as practical without shutting

off. Observe process gauges carefully.

C2. Poor location of process pressure tap. Evaluate and consider

relocation.

D1. Bypass control valve positioner and directly load actuator.

D2. Review sizing of control valve, may be oversized. Use re

stricted trim if necessary.

D3. Consult factory

A1. Open process needle valve adequately. Disconnect tubing and

blow sensing line.

A2. Check equivalent output tubing line length against those

indicated herein in Section 11.7. Relocate controller, or

consider adding an air booster or positioner at the control

valve.

A3. Check for mashed or pinched tubing.

A4. Installation debris. Air blow line.

A5. Ice in lines. Use dry air supply.

B. Increase supply up to 18-20 psig.

C. Decrease PB in 1/8 rev. increments. Reset setpoint as

required.

D. Use the lowest range possible, if available to obtain the best

response.

E. Add an air booster or positioner at the actuator.

F. Remove sensor sub-assembly and lubricate O-rings.

A. Piping weight is cantilevered off of process connections or

instrument air connections causing unscrewing, and effecting

internal clearances. Change piping or add supports as required.

B. Inspect diaphragm; replace if bent. Bent diaphragm indicates an

overpressure condition; correct if necessary.

C1. Provide a cleaner air supply or piping source.

C2. Ice in lines. Correct as necessary.

Remedy