PROCEDURE:BLOWDOWN FLOAT & ALARM COLUMNS

RISK RANKING:MEDIUM

HAZARD ASSESSMENT:

SAFETY EQUIPMENT:

Safety Glasses with side shields, hard hat, steel toe boots, FR Clothing, rubber gloves and personal gas monitor.

SAFETY NOTE:

All float columns indicate liquid levels in a vessel. A float, which moves inside a tube, activates high and low fluid level alarms. For remote indication, a float column may connect to a transmitter (control room indicator) or tie into a controller (level control).

PROCEDURE:

1. Lowdown Float Column:

  • Ensure lowdown of level column does not upset the process.
  • Isolate column via upper and lower bridle block valves.
  • Crack open drain valve and observe change in output signal. Signal may increase or decrease depending on instrumentation design.
  • Crack open upper bridle block valve to allow flow to drain. Avoid violent lowdown through column.
  • Close upper bridle block valve and crack open lower bridal block valve to allow flow to drain, then close lower bridle block valve.
  • Slowly open upper bridal block valve.
  • Slowly open lower bridal block valve, observe change in output signal.
  • Return level control valve, alarms, shutdowns, etc. to service.

2.Lowdown Site Glasses:

•Isolate site glass via upper and lower bridal block valves.

•Close in upper and lower Pemberthy valves.

•Open drain valve to depressure site glass.

•Open upper bridal block valve, crack open upper Pemberthy ensuring the gas or liquid flows freely to drain. Repeat as required to clean deposits on site glass.

•Close upper Pemberthy.

•Crack open lower Pemberthy, observe rising liquid level in site glass, ensuring flow from lower bridle. Open 2 or 3 times to ensure flow.

•Close lower Pemberthy valve, open drain valve to depressure site glass.

3.To Return Site Glass to Service:

•Close drain valve.

•Slowly open upper Pemberthy to prevent surge of pressure causing Pemberthy built in check to seat.

•Open lower Pemberthy using same caution as above. As a precaution, one may want to fully close upper and lower Pemberthy and open fully again to be sure the checks are reset.

NOTE: Pemberthy valves are equipped with a corrosion resistant steel ball check. Should the gauge glass break, the pressure drop causes the ball to seat to prevent loss of vessel contents. Extensions on the ends of the valve stems unseat the balls when valves are closed. For this reason Pemberthy valves should be fully opened when in-service.

PROCEDURE: BLOWDOWN FLOAT & ALARM COLUMNS

- 1 -Date of Preparation: November 25, 2004

Date of Revision: November 25, 2004

Date of Last Review: February 15, 2010