5 replies to this topic

[vashi saurabh]

I Want to ask 4 basic questions.

(1)What is per-Commissioning activity and what is commissioning activity?

(2)On what basis we will decide that this fluid will require hydro test and pneumatic test??Generally somewhere i read that In gas service pneumatic test will done and in liquid service hydro test will be done.is it true or is it some criteria based on that this will decide.

(3)On what basis hydro and pneumatic pressure will decide?

(4)What are parameters that will decide plant performance?

[wojtar]

I Want to ask 4 basic questions.

(1)What is per-Commissioning activity and what is commissioning activity?

(2)On what basis we will decide that this fluid will require hydro test and pneumatic test??Generally somewhere i read that In gas service pneumatic test will done and in liquid service hydro test will be done.is it true or is it some criteria based on that this will decide.

(3)On what basis hydro and pneumatic pressure will decide?

(4)What are parameters that will decide plant performance?

Regarding hydro and pneumatic pressure test:
Well, I'm not mechanical engineer but I think that pneumatic test should be used only in cases where any water presence in the system is not allowed. I would avoid that anyway. In case of failure it causes horrible destruction. Special safety precautions must be applied. During hydro test, in case of equipment failure, water just go out the equipment. Read further in ASME codes.

Regards.

Edited by wojtar, 27 April 2010 - 02:13 AM.

[Gaurav_O&G]

I Want to ask 4 basic questions.

(1)What is per-Commissioning activity and what is commissioning activity?

(2)On what basis we will decide that this fluid will require hydro test and pneumatic test??Generally somewhere i read that In gas service pneumatic test will done and in liquid service hydro test will be done.is it true or is it some criteria based on that this will decide.

(3)On what basis hydro and pneumatic pressure will decide?

(4)What are parameters that will decide plant performance?

(1)Pre commissioning activities include all the leak tests , flushing , dry outs etc. all the activities that are done before first start up of a unit takes place. The activities during first start up (after all pre-commissioning activities are completed) are commissioning activities.

(2)As far as i know any service where moisture content cannot be tolerated pneumatic test is done

(3)Normally hydro testing pressure is roughly 1.5 times (someone plz confirm) the design pressure of a equipment

(4)Plant performance can be characterized with conversion , energy efficiency etc. as parameters

Hope this helps

Gaurav Sharma

[gvdlans]

(1)Pre commissioning activities include all the leak tests , flushing , dry outs etc. all the activities that are done before first start up of a unit takes place. The activities during first start up (after all pre-commissioning activities are completed) are commissioning activities.

At the EPC company I worked for the shift from pre-commissioning to commissioning activities was when the plant was declared "mechanical complete". At that point of time the plant responsibility shifted from the construction manager to the commissioning manager. Commissioning ended when the plant was declared "Ready For Start Up". At that point of time the plant responsibility shifted from the commissioning manager to the plant manager.

Edited by gvdlans, 28 April 2010 - 03:35 AM.

[Gaurav_O&G]

(1)Pre commissioning activities include all the leak tests , flushing , dry outs etc. all the activities that are done before first start up of a unit takes place. The activities during first start up (after all pre-commissioning activities are completed) are commissioning activities.

At the EPC company I worked for the shift from pre-commissioning to commissioning activities was when the plant was declared "mechanical complete". At that point of time the plant responsibility shifted from the construction manager to the commissioning manager. Commissioning ended when the plant was declared "Ready For Start Up". At that point of time the plant responsibility shifted from the commissioning manager to the plant manager.

I am currently working in a refinery, here we define pre-commissioning activities as various activities to be performed after the mechanical completion to prepare unit for start up, and unit is said to be commissioned once we get on spec product

[Anirudh Kumar]

Dear Saurabh, my opinion to your ?? a) Pre-commissioning is upon 2 conditions-mechanical completion as per P & I D & the use of all non-process fluids (Nitrogen, air, anything not used normally for operation) for verification of system (piping, vessel, etc) and its integrity (blowing-cleanliness, pressure test, NDT etc). In short the system is ready to accept the process fluid. Commissioning is "first time"- successful introduction of process fluid at the first stage of the process, each sub-stage functioning OK and the final product generation.
Hydro-test (HT) and Pneumatic test (PT) are used based on "process safety" criteria, for e.g. if catalyst is already loaded into the vessel and then you close a few manholes, then attempt PT (fluid-can be Nitrogen), similarly for areas where water can be used, but piping configuration does not permit full draining or water blowing, we attempt equal pressure PT. For specific cases like boilers, drums, high press piping etc HT is mandatory, even though 100 % X-ray is done. In rare cases, client can forgo HT/PT in case of 100 % X-ray or very low pressure impracticality.
c) Pressure now a days is usually 1.25 times minimum of the design pressure, lower pressures is sometimes prescribed in case of Hot equipment - Note that HT or PT is not a static test, we raise the pressure gradually watching the system at each defined increment, don't want any mishaps
d) Parameters of plant performance vary with contract and process, some examples are - compliance to all air/water emission norms, local government laws, product quality and quantity, energy norms, safe operating range (say 40 % to 105 %)- safe shutdown system test, capability of control system in milli seconds, smooth control etc etc- this is a big issue, some of the parameters we cannot even practically verify. I hope you find this useful