PRESSURE VESSEL PERMIT TO WORK ON CHEMICAL TANKERS- CAPT AJIT VADAKAYIL
PRESSURE MUST ALWAYS BE EXPECTED INSIDE A CHEMICAL TANKERS CARGO PIPELINES CONTAINING TOXIC, CARCINOGENIC, BIOACCUMULATIVE, CORROSIVE OR HEATED CHEMICALS --
-- WHICH CAN SCALD, KILL , MAIM INSTANTLY OR AFFECT YOUR FUTURE GENERATIONS WITH GROSS MORPHOLOGICAL ABNORMALITIES SUCH AS CLEFT LIP.
It is usual on parcel chemical tankers to introduce air or nitrogen at 7 kg pressure into pipelines to blow the stack or clear the line. Imagine a slug of free flowing dangerous cargo like Sulphuric acid being projected through a pipe by compressed air of 7 kg which you deliberately introduce into the pipelines at stripping time. It will smash into all corners like a bullet.
Vapour lock means boiling in cargo lines due to excessive VP . Do not open any pipeline without depressurizing it first on a chemical tanker.
Crew must be aware of the direction of wind by looking at the anemometer fan on the mast when releasing the pressure.
All must be familiar with eye wash and shower arrangements. Goggles of the appropriate type and as required are to be worn on top of hardhats by deck crew to be used when required at an instant notice.
When loading Carcinogenic, Toxic or Bioaccumulative cargoes, ascertain the TLV-TWA . The Vervey’s tankcleaning guide gives the VP/TLV ratio--- anything more than one is dangerous requiring the use of Draeger tubes on deck and great care while opening out blanks and spools at manifold. Epichlorohydrin is 17, Methanol is 0.46 (200/92).
Filter protection must only be used against gases which has a distinctive smell and there is no lack of oxygen. If you can smell gas it means the filter is saturated and is to be discarded.
Class 1/ 1000ppm
Class2/ 5000 ppm
Mark X/ low BP products
Those not actually involved in a job should still be aware of what is happening, so that they may avoid putting themselves at risk or interfere with an unsafe act before it is too late. All should care for their own health and safety and for their shipmates.
Gas suits have resistance tables Viton/ Chloroprene rubber/ PVC. Positive pressure inside the suits add to safety.
Splash suits –for protection against liquid splashes –polyamide fabric coated both sides with PVC. Hood with draw string to fit under the helmet. Front zipper must be protected by double fly
A PVP Permit must be issued for all maintenance and repairs to pressure vessels, bolted plates, manhole covers and pipelines used for pressurized or hot liquids, gases and vapours, e.g. cargo/fuel oil, hydraulic systems, water, compressed air, steam lines, etc.
A PVP Permit must also be issued where work on a pressure vessel or pipeline system may result in a potential risk from the above to cause:
-- Injuries to personnel,
-- Release of a pollutant to air or the sea or on deck,
-- Uncontrolled sea water ingress in the machinery or other spaces.
PVP Permits must be issued in conjunction with " DO NOT OPERATE" tags.
Prior to commencing work all valves or cocks used to vent or drain the pressure vessel or pipeline system must be OPEN and secured; all valves or cocks used to isolate the pressure vessel or pipeline system must be CLOSED and secured.
All such valves, cocks and the associated machinery/equipment must be tagged with "Do Not Operate" tags. Details of the tagged valves should be listed on the Permit or a Tag Out/Lock Out Record.
The "Do Not Operate" tags must contain the following information:
-- The name and/or rank of the person placing the tag. This person is the only person who can remove or authorise the removal of such tags, unless a senior officer, authorises the removal. In such an event this Senior Officer must ensure that all work has been completed and/or that it is safe to return the system to use.
-- The date and time that the tag was placed.
-- The PVP Permit identity number relating to the tag out.
Where a PVP Work Permit is issued for pipelines which are connected to equipment that is mechanically operated, but electrically driven, it must be ensured that the driving equipment is electrically isolated. The circuit breakers or switches must be locked out, and "Do Not Operate" tags applied, and an Electrical Work Permit (EWP) issued.
These "Do Not Operate" tags should state the PVP identity number, name and/or rank of the officer posting the tag, date and time of posting.
The "Do Not Operate" tags must be completed using a non erasable ink, i.e. felt or fibre tip marker. They are of the "use once only" type.
A PVP Work Permit must be issued for each individual job.
Where more than one job is carried out on the same pressure vessel or pipeline system, a Permit is required for each job. However only one tag need be used, provided that all Permit identity numbers applicable to that pressure vessel or pipeline system, are recorded on the tag and the same person is carrying out all the work. Should different persons be carrying out work on the same pressure vessel or pipeline system then a tag is to be placed by each person
Note: The validity of this Permit is usually only for the working day. If extended or continuous work (24 hour) is to be carried out, the Permit should be cancelled and re-issued at the time of a change of shifts.
A PVP Work Permit must be authorised by a senior officer, in respect of all relevant work carried out in the machinery spaces, accommodation spaces, store spaces or on deck by any personnel, including outside contractors.
It is the responsibility of the Permit Authoriser to ensure that the pressure vessel or pipeline system to which the Permit refers, is correctly isolated and drained or vented. The Permit Authoriser must ensure that all "Do Not Operate" tags are in position before work commences, and should be in attendance as work commences to ensure that the correct pressure vessel or pipeline system is being worked on.
The Permit Authoriser must regularly monitor the work progress to ensure that all isolation/safety requirements contained in the Permit are being adhered to.
A PVP Work Permit need not be issued for work undertaken during major repair periods with the machinery plant shut down. However, it is the responsibility of the Chief Engineer or Permit Authoriser, to ensure that all pressure vessels and pipeline systems that are to be worked on, have been completely drained/vented, cooled down and are safe to work on.
Although a pressure vessel or pipeline system may appear to be isolated and drained/vented, it is possible for valves to leak and vents or drains to be blocked. Personnel working on the pressure vessel or pipeline system, and the Permit Authoriser, must be aware of this and ensure that great caution is exercised when removing pipes, valves, covers, etc. as follows:-
--Never remove all the securing bolts at once before loosening a flange or cover.
--Always ease back the bolts and ensure that the flange or cover is free and there is no pressure behind it before removing the bolts or fixing clamp.
--Personnel must be aware of the potential danger from accumulated hot liquids or hot vapours being released from opened pipes or pressure vessels due to leaking valves.
CAPT AJIT VADAKAYIL