a) Liquid Sampling Procedure (Non-Flashing Type)
i) The person taking samples should wear proper or appropriate safety clothing like
face shields, aprons, rubber gloves etc. to protect face, hands and body.
ii) Whenever hot samples are taken, check cooling water flow in the sample cooler
is circulating properly.
iii) Sample points usually have two valves in series. One gate valve for isolation
(tight shutoff) and other globe valve for regulating the flow. Open gate valve first and then slowly open the globe valve after properly placing the sample containers. After the sampling is over, close the globe valve first and then the
gate. Then again open the globe valve and drain the hold up between the gate and globe valve in case of congealing liquid.
iv) Sample valve should be slowly opened, first slightly to check for plugging. If the
plugging is released suddenly, the liquid will escape at a dangerously uncontrolled rate. Never tap the line to release the plugging. Call the maintenance gang to properly unplug the line. In case of congealing type samples, sample point should be equipped with copper coil type steam tracer. It should be ensured that steam-tracing line is functioning normally.
v) The operator taking the sample should be careful to stand in a position such that
the liquid does not splash on him and he has unobstructed way out from the sample point in case of accident.
vi) While taking dangerous toxic material for sampling, it will act as an observer for
safety. Proper gas mask is to be used. It is advisable to stand opposite to wind direction in case of volatile toxic liquid.
vii) Sample should be collected in clean, dry and stoppered bottle. In case of congealing samples use clean dry ladle.
viii) Rinsing of the bottle should be thorough before actual collection.
ix) Before collecting, ensure that the line content has been drained and fresh sample
is coming.
x) Gradually warm up the sample bottle / metallic can by repeated rinsing before
collecting the sample.
xi) Stopper the bottle immediately after collection of sample.
xii) Attach a tag to the bottle indicating date, time, and name of the product and tests
to be carried out.
xiii) A few products suffer deterioration with time.
xiv) For example, the color of the heavier distillates slowly deteriorates with time. So
The samples after collection should be kept away from any source of ignition to minimize fire hazard.
Volatile samples (e.g. naphtha) should be collected in bottles and kept in ice particularly for some critical test like RVP.
b) High Pressure Hydrocarbon Liquid Samples (Flashing Type)
i) The person taking sample should use personal protection appliances like apron,
gas mask and hand gloves to protect himself.
ii) Ensure that sample bomb is empty, clean and dry.
iii) Connect the sample bomb inlet valve to the sample point with a flexible hose.
iv) Open the inlet and outlet valves of the sample bomb. Hold the sample bomb.
Hold the sample bomb outlet away from person. Keep face away from hydrocarbon vapor and stand in such a way that prevalent wind should blow hydrocarbon vapor away. Open the gate valve of sample point slowly till full open. Then slowly cracks open the regulating valve. One should be careful at the time of draining, because chance of icing is there. As a result, the formation of solid hydrates is a continuing process, which leads to the plugging of valves.
v) When all the air in the hose and bomb are displaced as seen by the hydrocarbon
vapor rising from the outlet of sample bomb close the sample outlet valve. Allow a little quantity of liquid to spill to make sure that the bomb is receiving liquid. Frosting will be an indication of liquid spillage.
vi) Allow liquid hydrocarbon to fill the bomb. When the bomb is full up to the
specified level, close both the valves on sample point. Close inlet valve on the sample point.
vii) Carefully disconnect the hose from the sample bomb. To allow for some vapor
space in the bomb for thermal expansion in case of overfilling, crack open the outlet valve of bomb and discharge a small part of the liquid. Close outlet valve.
viii) Closed sampling facilities are provided at some locations where it is not desirable to waste the costly product or if the material is toxic. For filling the sampling bomb, pressure drop across a control valve is usually utilized or across pump discharge & suction. Air is expelled from the bomb after it is connected to upstream of control valve or pump discharge side. The sample is then collected and bomb is detached after closing valves on both sides.
ix) Send sample bomb to laboratory for analysis. Protect the bomb from heat exposure.
c) Gas Sample
For collection of gas sample, which are not under high pressure and temperature, rubber bladders are used. For the operations under vacuum or low pressure, aspirator is used. For representative sample, purge the bladder 3 to 4 times with the gas and then take t he final sample. Use of 3 ways valve with bladder / aspirator will facilitate purging and sampling.
Sample bombs are to be used for taking gas samples from high pressure and high temperature source. Procedure mentioned under high-pressure liquid sampling (flashing type) is to be used.