[MW:582] Surface Preparation and Coating

Let us discuss these two issues seperately for better clarity
one can't specify the timing when to start and stop, it depend various parameters, minumum you should check
apart from humudity atleast 3°C difference between the dew point and surface temperature of the steel to be coated, with the surface temperature being high.

surface after blasting is open to environment until first coat is applied, presence of humidity results in rust formation, and coating on top of it leads to blisters.

If u can, use dehumidifiers to over come the problem

On Feb 19, 2008 5:57 PM, Jivan Dhamane <jivanadhamane@yahoo.co.in> wrote:

Dear Friends

 

I have two queries that are as follows please advice me.

 

1. We are constructing Horton Sphere, at the initial stage our subcontractor had submitted PWHT procedure for whole sphere, but due to some accessories to inserted in the sphere for PWHT purpose they revised PWHT procedure in two parts. That is by Internal Firing Method for whole sphere except (Bottom Centre Crown plate weld) and after welding of Bottom Centre Crown plate weld PWHT is to carry out by Local Electrical Heating Method.

 

By doing so, BVIS Surveyor is asking for 02 Nos. Production Test Coupons (PTC). One for PWHT by Internal Firing Method and another for PWHT by Local Electrical Heating Method. We tried to convince BVIS Surveyor for only one no. PTC as Welding Procedure Specification (WPS), PWHT cycle and other all construction activities are same for both the part but BVIS Surveyor is no satisfied and asking for 02 Nos. PTC.

 

2. As per painting specifications codes and standard paining shall not carried out when the humidity is above 85%. What time sand/slag blasting shall start in the morning (as water due is present in atmosphere or the surface) and up to what time it shall continue in the evening? As you know India environmental condition and our site is near seashore.

 

Waiting for your reply, till then take care and good bye

 

Regards

 

 

Jivan Dhamane

---

--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to materials-welding-unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
-~----------~----~----~----~------~----~------~--~---