Need To Design A Simple Phosphating System for Machine Shop

A. Joseph,
This literally takes a small book to answer.
Step 1 is to get a copy of the specification (with all reference specs) and see what they require.

Very probably, it will be a zinc phosphate, but there are several formulations for different grain sizes.

Step 2 would be to contact all of the vendors of the zinc phosphate solution that you need to use.

The possible vendors can provide you with all of the information that you need to run the line as well as most of them will have one or more equipment vendors that they like to recommend.

The secret to running a good phosphate line is to follow the instructions -- exactly -- and to always have a load in the tank as soon as it gets to operating temperature. This will allow it to keep the acid ratio exactly where you need it to be. I always made a water addition to the tank after the last load came out to drop the temperature rapidly. You will make several water additions throughout the day because of the evaporation resulting from the high temperature.

The vendor will train your people on how to do the titrations. If not, find a better vendor.

A. Hi Osama.

Unfortunately we don't have enough information to understand your situation.

I don't really know what you mean by a connection being "recut". If this is painted steel and you have exposed bare steel, it probably should be pretreated before painting. To my knowledge there are no "universal" rules; so using a primer instead of phosphating may be sufficient. But depending on what business you are in, and what service you are providing, they may be specific rules or codes that affect you ... but we don't know your situation.

If your question is a follow-up on Joseph's question about API requirements for re-threading a threaded joint, I would assume that re-phosphating is necessary. But you would need to get a copy of the API specification as James suggests. I'm sure this is copyrighted and must be purchased; people would not be allowed to send you a copy of their copy. I am not from the petroleum industry, so I am not familiar with API codes; but from the title of the specs, I'd probably start with API 570 "Piping Inspection Code: Inspection, Repair, Alteration, and Rerating of In-Service Piping Systems". Best of luck.

Regards,