Sea Water filtration and PHE protection: Is package Plate Heat Exchangers + Self Cleaning Filters purchased by one Supplier the right solution?

 

Central Cooling with sea water using Plate & Frame Heat Exchangers in Titanium is a now the system usually in operation when large duties are required (Oil & Gas, Petrochemicals, Power etc.) on seashore with small LMTD between fluids and advantage to use cooling water loop inside the plant with no requirements of exotic material on heat exchangers, valves etc.

On the other hand we have to protect Plate & Frame HEX: 1-2 mm filtration (20-50% of of the plate gap) when sea water is involved, to avoid clogging

EPC Contractors trend is now to prefer buying complete package (PFHE+filters) by one single supplier (to avoid discussion in case of malfunction) 

Due to large flowrate of sea water involved, pressure drop is a crucial value to consider in design: typically PFHE+Filters shouldn't be higher than 0.8-1 bar.

Sometimes increase size of connections to reduce pressure drop and number of PFHE installed can avoid to provide a booster pump station with significant impact on price.

Tradional filtration system are not used any longer due to high pressure drop required and Automatic Self-cleaning Bernoulli type Filter is by far the most common way to protect PFHE's in sea water applications.

Sizing is very simple: check on chart flow rate and select Filter Diameter to get pressure loss

Main competitive edge of Bernoulli type filter is low Delta P: can be even 11 kPa with 4,000 m3/h with DN 600 filter.

Several times EPC Contractors, in spite of different Material Requisitions, are asking for complete package to Plate & Frame HE's Manufacturer (ratio in terms of value PFHE/Filter is 70/30 due to plates in Titanium), so full responsability of total pressure drop is up to one single supplier.

There are few comments on this approach:

• PFHE Manufacturer is buying & reselling Filter, with his mark up at least 25-30%
• General Terms & Conditions (GTC) by EPC Contractors are really complicated and Filter Manufacturer maybe is not able to accept some paragraph.

• Logistic is more complicated: workshops normally are in different countries and Release Note for Invoice could be delayed owing to Forwarder issues.
• Milestones Payment related to main materials arrival is difficult to clarify: which supplier will determine date of payment?
• Bank Guarantee for Advance Payment and for Performance Bond will be issued by PFHE Manufacturer calculated on Total Amount, but Filter Company will not be involved in these Bank Guarantees. In case of trouble who will be responsible? Filter Manufacturer should provide Bank Guarantee to PFHE Manufacturer?

• Normally 10% Payment is related to Documentation (VDR, Operation Manual etc.) in case of late delivery by Filter Manufacturer all penalty will be up to PFHE Manufacturer. Even if this money will be charged to Filter Manufacturer in terms of cash flow this is not a nice situation.
• If Total Pressure Drop is higher than estimated PFHE Manufacturer will not pay Filter Manufacturer starting a claim.

Now you can understand why PFHE Manufacturers are trying to reply to EPC that their Core Business is pressing plate and not selling Filters...

Personally I have been involved in this kind of business with EPC Contractor in Italy, PFHE Manufacturer in Germany and Filter Manufacturer in Sweden.

Nightmare was documentation, because every supplier was using his own format, so that PFHE had to transform every single page according to EPC Contractor requirement

Delivery was FOB Antwerp and logistic problems have been settled.

Power of EPC Contractors is getting stronger and stronger , therefore Buyers are pushing to get one single Supplier.

Recommendations to Heat Transfer Specialists therefore is to select a Filter Manufacturer not on price only, but on experience with EPC Contractors and reference with large international OEM, otherwise money saved on purchasing will be spent after job execution in technical adjustment, penalty etc. and worst consequence will be reputation of PFHE Manufacturer lost due to trouble independent from his will!