How to Specify Liquid Distributor Orifice Diameter and Hole Arrangement
Orifice size is one of the most critical fabrication parameters in a liquid distributor.
It determines how liquid leaves the distributor under a given liquid head.
Because drilling a hole is simple, procurement teams sometimes treat the orifice diameter as a minor shop detail.
It is not.
Changing the hole diameter can change distributor hydraulics.
Why Orifice Diameter Matters
For a given liquid head, orifice diameter affects the flow through each discharge point.
A relatively small dimensional change can alter:
- individual point flow;
- total distributor capacity;
- operating liquid level;
- turndown performance.
Therefore, the production orifice diameter should match the approved hydraulic design.
Hole Size Cannot Be Chosen Alone
The correct diameter depends on:
- liquid rate;
- number of outlets;
- liquid head;
- liquid density;
- viscosity;
- fouling tendency.
This is why procurement should not specify a random hole size copied from another tower.
The orifice diameter should come from the distributor design.
Hole Arrangement Is Equally Important
Two distributors can have identical:
- total flow;
- number of holes;
- hole diameter
but different liquid distribution quality if the hole positions differ.
Therefore, the layout drawing should show:
- outlet location;
- spacing;
- wall-zone arrangement;
- inactive areas;
- relationship to structural members.
The approved layout becomes part of the procurement basis.
Drilling Tolerance
Manufacturing tolerances should be realistic but controlled.
A hole significantly larger than design can discharge more liquid than intended.
A hole too small may restrict flow or plug more easily.
For critical service, the purchase specification may define:
- nominal diameter;
- allowable tolerance;
- inspection method.
The level of control should match the hydraulic sensitivity of the distributor.
Burrs and Blockage
Poor drilling can leave:
- burrs;
- partially blocked holes;
- deformed openings.
These defects can disturb outlet flow.
Therefore, final inspection should confirm that discharge holes are open, clean, and reasonably free from burrs that affect hydraulic function.
Fouling Service
Very small holes may provide excellent distribution in clean service but become vulnerable to plugging in dirty service.
Procurement teams should ensure the supplier receives information on:
- suspended solids;
- crystallization;
- scaling;
- dirty liquids.
The process design may then require a different distributor concept rather than simply larger orifices.
Changes After Hydraulic Design
During fabrication, a supplier may find that another hole diameter is easier to manufacture.
It should not be changed informally.
Any change in:
- hole size;
- number of holes;
- layout
that affects distributor hydraulics should be submitted for technical approval.
Water Testing
For important distributor systems, a water test can help verify:
- flow distribution;
- liquid level;
- blocked outlets;
- fabrication consistency.
However, the test conditions should be defined.
A vague statement such as “water test required” is not enough.
The buyer should identify what the test is expected to demonstrate.
Inspection Records
Depending on project QA requirements, the supplier may record:
- orifice diameter sampling;
- outlet count;
- drawing revision;
- water-test results;
- dimensional inspection.
This creates traceability between the hydraulic design and the fabricated distributor.
Engineering Takeaway
Liquid distributor orifice diameter and hole arrangement should be treated as controlled hydraulic fabrication parameters.
The supplier should manufacture according to the approved design and should not change outlet geometry without technical review.