Orifice clamp joint: how to choose the diameter of the calibrated orifice plate

On a line of 2″ to 5 m³/h water, a 16.4 mm orifice creates 0.5 bar of pressure drop. Formula, table from 1″ to 3″, choice of model and adjustment on site: the method for dimensioning a clamp joint at Port without adjustment valve.

Par Jean-Philippe Pavard, ingénieur, Tubes TechnologiesPublié le à compléterLecture 8 min

the essential

A hole clamp joint is a tri-clamp joint which carries a drilled 316L stainless steel plate: it adjusts a flow to the joint plane, without valve or dead arm.
The diameter is calculated with the LISO 5167-2: Q = C × (π × D² / 4) × √(2ΔP / ρ(1 − β⁴)), C ≈ 0.61.
Order of magnitude: 21.8 mm for 0.5 bar in a 2″ tube at 1.5 m/s.
Eccentric plate for lines that must drain, conical for vertical pipes (up to 4″).
On site, in particular at the EPPI sampling points, the diameter is adjusted by successive drilling, starting from a small orifice.

One Orifice clamp seal is a tri-clamp sanitary seal in which is set a stainless steel plate pierced with a calibrated hole. The diameter of this hole fixes the pressure drop, therefore the flow rate, to the joint plane, without valve or additional tapping. On a line of 2″ to 5 m³/h water, a 16.4 mm orifice creates approximately 0.5 bar of permanent pressure drop.

All the sizing fits in this relationship between the flow rate, the targeted pressure drop and the orifice diameter. This article gives the formula, an array of diameters from 1″ to 3″ and the rules of choice of the model.

What is a hole plate in a clamp fitting for?

A hole plate creates a fixed restriction. Passing through the lorifice, the fluid accelerates, its pressure drops, then it partially goes downstream. The part that does not go up is the permanent pressure drop, that which regulates the flow.

In a pharmaceutical or biotech installation, the orifice clamp seal is used for four uses:

balance a loop Purified water or DEPPI: Limit the flow of a short branch to guarantee speed in long branches.
Maintain a back pressure on the loop return, so that the points of use remain powered.
Adjust the flow rate of a sample point DEPPI or purified water, the most common use on site, or limit the flow of a point of use or a rinsing circuit.
break During a sterilization phase (SIP) or cleaning in place (CIP) phase.

The interest compared to an adjustment valve: no valve body, no dead arm added, no drift setting. The plate mounts between two ferrules instead of a standard joint. The SD share of BPE lasme Also cite the orifice plates among the components of the hygienic systems.

The sizing formula

The flow that passes through a sharp-edged port follows Liso 5167-2:

Q = c × (π × d² / 4) × √(2 × Δp / (ρ × (1 − β⁴)))

Q: Volume flow, in m³/s;
C: discharge coefficient, about 0.61 for a thin, sharp-edged plate;
D: Hole diameter, in m;
Δp: pressure difference on either side of the orifice, in PA;
ρ: density of the fluid, in kg/m³ (998 for water at 20°C);
β: ratio d / d between the head diameter and the inside diameter of the tube.

The permanent pressure drop is lower than Δp, because part of the pressure recovers downstream. For β between 0.3 and 0.4, it is 82 to 90% of Δp. For β = 0.6, it drops to 63%.

For a first calculation, when β remains below 0.4, the term (1 − β⁴) is close to 1 and the formula is simplified:

d ≈ √( 4 × q / (π × c × √(2 × Δp / ρ)) )

Table: Door diameter according to tube and pressure drop

The table below gives the diameter for a speed of 1.5 m/s in the tube, a current value in purified water circuit and in CIP. Tubes with ASME BPE dimensions (1.65 mm thick), water at 20°C.

Tube (Ø ext. × ép.)	Ø intérieur	Débit à 1,5 m/s	Orifice pour 0,2 bar	Orifice pour 0,5 bar	Orifice pour 1 bar	Orifice pour 2 bar
1" (25,4 × 1,65)	22,1 mm	2,1 m³/h	12,2 mm	10,1 mm	8,7 mm	7,5 mm
1 1/2" (38,1 × 1,65)	34,8 mm	5,1 m³/h	19,2 mm	16,0 mm	13,7 mm	11,7 mm
2" (50,8 × 1,65)	47,5 mm	9,6 m³/h	26,2 mm	21,8 mm	18,8 mm	16,0 mm
3" (76,2 × 1,65)	72,9 mm	22,5 m³/h	40,2 mm	33,5 mm	28,8 mm	24,6 mm

Perte de charge permanente visée. Calcul selon l'équation de l'ISO 5167-2, coefficient de décharge 0,61. Ordre de grandeur, pas une valeur de projet.

two useful readings. Dividing the pressure drop by ten only gains a factor of 1.6 to 1.8 on the diameter: the header diameter varies as the fourth root of the pressure drop. And a 1 mm error when drilling a 10 mm orifice changes the pressure drop from 30 to 50%, because it varies as the reverse of power four of the diameter. The precision of the drilling matters more than that of the calculation.

Encrypted Example: Balancing an EPPI Loop Branch

A 2″ ASME BPE Tube Loop Branch (47.5 mm inner Ø) should be limited to 5 m³/h, with a permanent pressure drop of 0.5 bar.

Flow: 5 m³/h = 0.00139 m³/s.
First calculation with the simplified formula: d ≈ 16.9 mm, i.e. β = 0.36.
Correction of permanent pressure drop: at β = 0.36, it is 85% of ΔP. It is therefore necessary to aim Δp = 0.58 bar through the orifice.
Result: an orifice of 16.4 mm, β = 0.34.
Speed in lorifice: about 6.5 m/s, without any particular risk for cold water under a few bars.

For LEPPI at 80°C, the density drops to 972 kg/m³ and the diameter gap remains below 1%.

Full, pre-drilled or vertical plate: choose the model

Joint clamp à orifice : plaque pleine et plaque prépercée excentrée — Joint clamp à orifice : plaque pleine à percer (à gauche) et plaque prépercée excentrée (à droite).

The orifice clamp joint comes in three executions. The choice depends on the orientation of the line and when the diameter is frozen.

Modèle	Description	Quand le choisir
Plaque pleine non percée	Livrée sans trou, à percer après calcul	Le diamètre n'est pas encore figé, ou vous percez vous-même
Plaque plate prépercée concentrique	Alésage centré	Ligne sans contrainte de vidange
Plaque plate prépercée excentrée	Alésage en bas de veine	Ligne horizontale qui doit se vidanger sans rétention, par exemple un circuit CIP
Plaque verticale conique	Plaque conique orientée vers le bas	Conduite verticale : une plaque plate y retiendrait le liquide. Jusqu'au 4"

On an eccentric plate, the hole is drilled opposite the tongue. The tongue rises upwards, which places the lorifice at the bottom of the vein. The visual cue becomes an editing mark.

Materials, sizes and standards

Caractéristique	Valeur
Plaque	Inox 316L, électropolie en standard
Rugosité de plaque	0,8 µm à 0,38 µm électropolie (EP)
Joint	EPDM, FKM, silicone, PTFE ou Steam-Flon
Liaison joint / plaque	Élastomère lié en standard, joint amovible en option
Tailles	1/2" à 6", jusqu'au 4" pour le modèle vertical
Normes de raccord	DIN 32676 série A, série B (ISO 1127), série C (ASME BPE)
Conformité	FDA et USP Class VI
Options	Languette gravable au laser, service de perçage

The bonded joint is replaced with its plate in case of failure. The removable seal is justified when you drill the plates yourself: it avoids contaminating the elastomer during the machining.

The plate stiffens the joint: a clamp that is too tight or misaligned pipes damage it faster than a full joint. the compression is taken at the torque prescribed for the collar, and a Safx Safety Clamp Collar Avoids the accidental opening of a fitting that has a restriction.

Joint clamp with orifice or adjustment valve: the comparison

The orifice clamp seal and the adjustment valve meet the same need, limit a flow, but not with the same constraints. The choice depends above all on the stability of the target flow and the cleanability requirements of the line.

Critère	Joint clamp à orifice	Vanne de réglage à membrane
Débit	Fixe, défini par le diamètre d'orifice	Réglable en exploitation
Bras mort ajouté	Aucun : la plaque est au plan de joint	Corps de vanne et ses raccords
Dérive du réglage	Aucune, sauf usure de l'orifice	Possible après démontage ou maintenance
Encombrement	Épaisseur d'un joint	Corps de vanne, actionneur ou volant
Nettoyage CIP et SIP	Plaque lisse, 0,8 µm à 0,38 µm EP, drainable en version excentrée ou verticale	Membrane à qualifier, rétention possible selon l'orientation
Qualification	Un diamètre à documenter	Position de réglage à verrouiller et à vérifier
Changement de consigne	Remplacer le joint clamp à orifice	Tourner le volant

In practice, the orifice clamp joint is imposed on the loop branches and returns whose flow does not change. The valve remains necessary where the flow rate is to vary depending on the production. The two often combine: a valve to adjust during commissioning, then a calibrated orifice plate to freeze the adjustment obtained.

Commissioning on site: adjust the clamp joint with holes by successive holes

On site, the door diameter is most often adjusted by tests, in particular on the EPPI sampling points. The calculation gives the starting point, the test gives the final value: the actual pressure losses of the sampling valve, output and loop always move a little from the model.

The method consists of pre-drilling a small diameter orifice clamp joint, and then growing in stages to the desired flow rate, measured under the standard operating conditions.

Leave small. Drill a first plate, or order a pre-drilled calibrated orifice plate, at a diameter less than that given by the calculation. An orifice can always grow, never be reduced.
Measure in standard operating conditions : Routine EPPI loop pressure and temperature, sampling valve open as with actual sampling.
Enlarge in stages. If the flow rate is insufficient, drill back to the next higher drill and start the measurement again. The flow varies like the square of the diameter: going from 4.0 to 4.5 mm increases the flow by about 27%. 0.5 mm bearings are sufficient.
Freeze the validated diameter. When the target flow is reached, engrave the diameter on the tongue and record it in the sampling point file.
reproduce without trying again. Order the pre-drilled replacement hole clamp seals with a diameter validated, rather than drilling on site at each maintenance.

Each drilling is done outside the clean zone, followed by deburring and cleaning the plate before reassembly. The removable joint is the right choice here: it is removed during machining and is not likely to be contaminated by chips. This method makes the setting reproducible: the same orifice clamp joint, reassembled after maintenance, restores the same flow rate at the sampling point.

Locate the plate once mounted

A port clamp seal cannot be seen, collar closed. This is the weak point of the solution: a plate forgotten during a maintenance, or reassembled in the wrong branch, unbalances the whole loop. The tab that protrudes from the fitting signals the in-line plate. Laser engraved with the header diameter, it allows you to check the correct plate without disassembling. it is the same logic as the Engraved clamp joint : travel information with the room.

Documents to download

PDFDimensions des joints clampCorrespondance collier, ferrule et tube, commune à toutes les exécutionsEN PDFListe de résistance chimique des élastomèresCompatibilité par fluide et par matière de jointEN

frequently asked questions

Qu'est-ce qu'un joint clamp à orifice ?

C'est un joint sanitaire tri-clamp dans lequel est sertie une plaque inox 316L percée d'un orifice calibré. Il se monte entre deux ferrules comme un joint standard et crée une perte de charge fixe qui règle le débit.

Comment calculer le diamètre d'un orifice calibré ?

Avec l'équation de l'ISO 5167-2 : Q = C × (π × d² / 4) × √(2 × Δp / (ρ × (1 − β⁴))), avec un coefficient de décharge C d'environ 0,61. Pour β inférieur à 0,4, d ≈ √(4Q / (π × C × √(2Δp/ρ))).

Quel diamètre d'orifice pour 0,5 bar sur un tube 2" ?

À 1,5 m/s dans un tube 2" ASME BPE (9,6 m³/h d'eau), environ 21,8 mm. Pour 5 m³/h dans le même tube, environ 16,4 mm.

Quelle différence entre une plaque à orifice concentrique et excentrée ?

L'orifice concentrique est centré. L'orifice excentré est placé en bas de veine pour que la ligne se vidange sans rétention en amont de la plaque, ce qui compte sur un circuit CIP horizontal.

Peut-on monter une plaque à orifice sur une conduite verticale ?

Oui, avec le modèle vertical conique. Une plaque plate dans une conduite verticale retient le liquide en amont. La forme conique orientée vers le bas assure l'auto-drainage. Ce modèle existe jusqu'au 4".

Quelles matières pour un joint clamp à orifice ?

Plaque en inox 316L électropoli, joint en EPDM, FKM, silicone, PTFE ou Steam-Flon, conformes FDA et USP Class VI.

Plaque pleine ou prépercée ?

La plaque pleine laisse le diamètre ouvert jusqu'au dernier moment : on la perce après calcul. La prépercée arrive avec son alésage défini et fait gagner l'étape de perçage.

Une plaque à orifice remplace-t-elle une vanne de réglage ?

Pour un débit fixe, oui, sans bras mort ni réglage qui dérive. Pour un débit qui doit varier en exploitation, non : il faut une vanne.

Quelle rugosité pour un joint clamp à orifice ?

La plaque d'un joint clamp à orifice est en inox 316L, avec une rugosité de 0,8 µm à 0,38 µm électropolie (EP), cohérente avec les surfaces d'un circuit pharmaceutique.

Comment repérer un joint clamp à orifice une fois monté ?

Par sa languette, qui dépasse du raccord clamp. Gravée au laser avec le diamètre d'orifice, elle permet de vérifier la plaque à orifice calibré en ligne sans démonter le collier.

Comment régler un joint clamp à orifice sur un point d'échantillonnage EPPI ?

Par perçages successifs : partir d'un orifice plus petit que le diamètre calculé, mesurer le débit dans les conditions d'opération standard, puis agrandir l'orifice par paliers de 0,5 mm jusqu'au débit souhaité. Le diamètre validé est ensuite gravé sur la languette et reproduit sur les joints de rechange.

Jean-Philippe Pavard

Auteur · Ingénieur, Tubes Technologies · tuyauterie procédé, agitation magnétique, disques de rupture, étanchéité

Ancien ingénieur mise en route et expert traitement d'eau dans un grand groupe alimentaire, puis chargé d'affaires en pharmaceutique, microélectronique et agroalimentaire. Profil LinkedIn

Pierre Goubert

Co-éditeur · Spécialiste des composants aseptiques à rugosité contrôlée, Tubes Technologies

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The products mentioned in this article

Clamp Joint Clamp and Clamp Fitting Components, FDA/USP Class VI, distributed by Tubes Technologies.

Inox 316L · FDA / USP Class VIJoint clamp à orifice calibréPleine, prépercée ou verticale, 1/2" à 6"Voir la fiche →EPDM · FDA / USP Class VIJoint clamp EPDMLe joint plein en amont et en aval de la plaqueVoir la fiche →PTFE · FDA / USP Class VIJoint clamp PTFEFluides agressifs et températures élevéesVoir la fiche →1.4435 · Safetron 0,40 µm BFFerrule standard type BLa portée qui reçoit le joint à orificeVoir la fiche →

Have your orifice calculated and drilled

Send us the flow rate, fluid, temperature and load loss targeted: our technical team calculates the diameter and can deliver the clamp seal with an already drilled orifice, with engraved tongue.