Products · 01

Gravimetric Control System

Installed at the top of the extruder feed port, it holds the weight of every metre with PID closed-loop control — continuously regulating screw speed, haul-off speed and feed rate. Control accuracy 0.4/100, saving 2%–5% of raw material.

Get a proposal & quote 4008-4040-80

What is it

What the gravimetric control system is

Meter weight is the weight of one metre of product. It can be calculated from the product's dimensions and the density of the material, and holding it constant during production largely determines how good the product is.

The Sealion gravimetric control system is installed at the top of the extruder's feed port. Using PID (proportional-integral-derivative) closed-loop control, it automatically and strictly controls the weight per metre, continuously regulating screw speed, haul-off speed and feed rate at any moment of the run.

Why equip it

Why a conventional line needs it

Stage	Without a control system	With Sealion gravimetric control
Start-up	Weight per metre is unknown; a long length must run out before thickness can be judged, and repeated adjustments waste material, time and labour.	Weight-per-metre data appears on screen from the first moment, shortening start-up; haul-off and extrusion speed can be trimmed live, saving material and time.
Running	Depends on the operator's experience; the process can't be monitored and deviation is unpredictable.	Extruder and haul-off are driven automatically from the weight recipe, removing human error; weight is monitored throughout and any deviation raises an alarm.
Material change	Every supplier's resin behaves differently; the weight shift is unknown and scrap is unavoidable.	However the raw material changes, the system detects and corrects it automatically.
Traceability	Once in the warehouse, nothing can be traced.	The whole run is recorded and stored, and can be traced afterwards.

Measured

The same line, recorded before and after control

These 20 readings come from Sealion's own product manual — not a simulation, but weight-per-metre logged on one line, before and after.

162–174Weight range, uncontrolled

164–165Weight range, controlled

12 → 1Spread narrowed

3.5 → 0.5Std. deviation (about 1/7 the swing)

Show the raw data (20 readings from the manual)

Without control system			With Sealion gravimetric control
#	Time	Weight	#	Time	Weight
1	16:12	174	11	00:14	164
2	16:15	173	12	00:31	164
3	16:26	165	13	00:50	164
4	16:59	166	14	01:16	164
5	17:19	167	15	01:38	164
6	17:41	165	16	01:57	164
7	20:18	167	17	02:30	164
8	20:39	162	18	03:00	165
9	21:21	167	19	03:15	165
10	21:43	166	20	03:40	165

Source: Sealion Technology Product Manual, Gravimetric Control System — Main function. Spread and standard deviation are computed directly from these readings.

Workflow

How the system works

The system carries an intelligent weighing device: the hopper valve opens and closes in a continuous cycle so that every batch falls freely under identical pressure. Each opening and closing is governed by the microcomputer in this sequence:

1
FillThe valve closes once material reaches 80% of the hopper.
2
FeedMaterial falls freely, feeding the main screw.
3
CycleAt 20% the valve opens, refills, and the next cycle begins.

Functions

Main functions

Shortens start-up and removes the blind spot where nothing can be adjusted in time

Stops weight deviation wasting resin — saves 2%–5% of raw material

Handles pipe breaks and re-joins by controlling weight and output

Absorbs changes in resin density and ratio that make walls uneven

Steadies the process and holds product quality

Prevents scrap pipe caused by a blocked screen pack

Records and stores production data for full traceability

Single-weight dual-output control for high-speed PE/PPR/PERT lines with synchronised twin haul-off

Technical structure

Technical structure of the gravimetric control system

01Display control unit

02Hopper weight & sensor unit

03Meter weight data acquisition unit

04Extruder rotating speed acquisition unit

05Tractor speed acquisition unit

Mechanical parts

Load cell, pneumatic cylinder, hopper, hopper retaining ring, hopper hooks, acrylic sleeve, aluminium feed-throat flange, silicone feed-throat flange, shut-off valve, extruder feed-throat mounting seat, main control box, air filter-regulator and alarm beacon.

Where it mounts The base and transition plate fit at the extruder feed throat, the shut-off valve seats into the base channel, and the weighing unit bolts onto the base; hopper, hooks, acrylic sleeve and cover then assemble in order.

Feed connection A wire-reinforced hose is clamped to the silo outlet at one end and sits in the aluminium flange feed-throat channel at the other.

Screw speed pick-up The proximity-switch bracket is fixed beside the extruder screw with the sensing collar on the screw itself; the switch aligns to the sensing point with a clearance gap preserved.

Line speed pick-up The encoder mounts either way: on an encoder arm riding the pipe above the water tank, or directly on the haul-off bearing.

Display & air supply The display mounts on the side of, or above, the extruder control cabinet; the air filter-regulator on the main box takes an external air line set to 0.3–0.4MPa.

Routine care Keep the inside of the control box dry and remove dust from the modules periodically.

Installation

The system installs on top of the extruder's feed port, without altering the existing line layout.

The production line before and after installing the Sealion gravimetric control system — Top: before installation　Bottom: after installing the Sealion gravimetric control system

Double output

Double-output gravimetric control system

On today's popular PE/PPR/PERT high-speed production lines, linear speed reaches 20 m/min. Adjusting that speed makes the tube too thick or too thin — sometimes the pipe breaks outright.

The double-output gravimetric control system controls both extrusions from the line's twin haul-off speeds and the host output. It works the same way: automatically regulating screw speed, twin haul-off speed and feed rate in real time to match the weight accuracy we set, so the pipe's weight-per-metre stays constant.

Parameters

Technical parameters

Power supply	AC220V	Operating temp.	-10~50℃
Max. humidity	90%R.H, non-condensing	Power consumption	10W
Load cell range	10 / 20 / 30 / 50kg	Input sensitivity	0.5uV/d
Input range	0.2~25mV	A/D resolution	24bit
D/A resolution	12bit	Conversion	Sigma-Delta
A/D speed	4000 /s	Non-linearity	0.01%F.S
Gain drift	10PPM/℃	Max. display accuracy	1/10000
Control mode	Extruder or haul-off	Control accuracy	0.4/100
Hopper volume	7L / 22L / 48L / 52L	Height	1000mm
Total weight	60KG

Model

Model configurations

Configurations can be tailored to your line.

Single-extruder gravimetric control

Model	Output	Size
MIXSCAN7	300 Kg/h	404×500×726
MIXSCAN22	500 Kg/h	404×500×886
MIXSCAN48	800 Kg/h	404×500×996
MIXSCAN52	≥1000 Kg/h	404×500×1096

Twin-extruder co-extrusion gravimetric control

Model	Output	Size
Mixscan7-7	300 + 300 Kg/h	404×500×726 (×2)
Mixscan22-7	500 + 300 Kg/h	404×500×886 / 726
Mixscan48-7	800 + 300 Kg/h	404×500×996 / 726
Mixscan52-7	1000 + 300 Kg/h	404×500×1096 / 726
Mixscan22-22	500 + 500 Kg/h	404×500×886 (×2)

Triple-extruder co-extrusion gravimetric control

Model	Output	Size
MIXSCAN 7-7-7	300 × 3 Kg/h	404×500×726 (×3)
MIXSCAN 22-7-7	500 + 300 + 300 Kg/h	404×500×886 / 726 / 726
MIXSCAN 48-7-7	800 + 300 + 300 Kg/h	404×500×996 / 726 / 726

Control modes

Four control modes

One system, four ways to hand over control — chosen to suit the line and the process goal. Whichever end the system takes over, the other stays available for the operator to trim by hand, which is what matters most on the floor.

Extruder wall-thickness control The system takes over screw speed; haul-off speed stays adjustable. To trim the extruder up or down, adjust the haul-off.

Haul-off wall-thickness control The system takes over haul-off speed; screw speed stays adjustable. To trim the haul-off, adjust the extruder.

Output control The system takes over screw speed; change the output figure and the line speeds up or slows down accordingly.

Dual control Both extruder and haul-off are under system control; changing the output value lets the system accelerate or decelerate on its own.

Under wall-thickness control, if the pipe comes out thin or thick, change the target in the gravimetric or spec setting — no need to touch the extruder. The system raises or lowers the screw or haul-off itself.

Calculation

Weight-per-metre calculation & four ways to start

Enter outer diameter, wall thickness and material density and the system derives the weight per metre; set OD, density and weight per metre instead and it derives the wall thickness.

weight/m = (OD − wall) × wall × 3.14 × density ÷ 1000

The line can be started four ways, whichever suits the crew: by frequency (Hz), by screw speed, by haul-off speed, or by output. Starting on frequency is usually the clearest right after installation.

Recipes

Recipes, changeover and thickening

Production recipes Once the line is stable, save the current spec as a recipe. Next time you run it, recall the recipe and extruder and haul-off ramp back to the saved speeds within 30 seconds — reaching steady state fast and cutting start-up scrap.

Changeover recipes Four further slots store the screw and haul-off speeds used when splicing, so a changeover is one recall instead of a fresh trial by feel.

Thickening For pipes that need one thickened end, such as socket ends, set the thickened wall and thickened length and the system switches between thick and thin sections in step with cut length.

Value

Seven things the system settles for a line

No more starting by trial It removes the problem of not being able to correct during start-up and production, so lines come up faster with less waste.

Order-based production Orders can be created and stored with spec, material and the person responsible, and combined with intelligent ratio setting for a fast, traceable start.

Closed-loop control in one step Closed-loop, self-adjusting control reaching 0.3% control accuracy under standard conditions.

Material saved, in cash terms It removes the raw-material waste caused by weight deviation during production, saving 2%–5% of material.

Absorbs density and ratio drift It corrects uneven wall — or uneven insulation and sheath on cable — caused by changes in material density or blend ratio.

Output reporting Output accumulates by year, month and day and is presented graphically for management.

24-hour quality monitoring Production quality is watched around the clock, with alarms for starved feed, weight fluctuation, and extruder or haul-off faults.

Statistics

Output statistics, pass rate & material planning

The system is not only a controller — it is also the line's production ledger.

Length & pass/fail judgement Set the length per piece or coil and anything within ±1 m of target counts as good. Set 21 m, for instance, and a measured 20–22 m passes. The running length resets automatically at each cut; a good piece increments the count, an out-of-tolerance one does not.

Good and scrap counted separately The output page records total output, good output, scrap output, piece count and produced length, so pass rate no longer has to be worked out by hand.

Material planning by coil Enter the wound length per coil and the number of coils and the system works out how much material to draw; enter the material weight already drawn and it tells you how many coils it will make.

Shift and long-period statistics Output can be metered per shift, with separate shift and grand-total resets, alongside twelve months of accumulated data and the records of the last 100 pieces.

One accumulation screen Current output, output since start-up, weight per metre, running time, output from the current batch of material and the running total are shown together.

A full audit trail Operator actions, commissioning steps, production records and alarm records are all retained for later review and shift handover.

Protection

Alarm-linked protection & curve diagnostics

An alarm is more than a notification. With alarms enabled the system acts, rather than letting a faulty line keep making scrap.

Coordinated slowdown and stop If the extruder or haul-off faults during production, the system ramps both down together and stops them, instead of running on in a broken state.

Automatic hand-back of control If gravimetric control itself becomes unstable, the control signal switches back to the machine's own control line — protection that does not cost you production.

Self-explaining alarm screen Cause, the operator actions at the time, the code's meaning and its remedy, plus the history log, all on one screen; re-enable alarms once the issue has been checked and cleared.

Ten performance curves Weight per metre, output, haul-off speed, extruder and haul-off voltage readings, extruder and haul-off outputs, screw speed, screw feed rate and hopper weight — switchable at a touch.

See the quality of control The speed and voltage curves reveal how hard the system is correcting, and whether overshoot or clamping is occurring during control.

See whether feeding is even Hopper value and screw feed-rate curves sit together, making uneven intake obvious — often the true source of weight fluctuation.

More

Interface language, connectivity & other practical features

Multilingual interface The interface switches between Chinese and English, with a Russian version also available for the pipe edition — useful for export lines and expatriate teams.

Monitoring platform link Network settings connect the system to the Sealion monitoring platform, sending production data straight through for remote viewing and central management.

Masterbatch ratio Working with the masterbatch dosing system, a colour ratio can be set against current output — at 300 kg/h and 1%, masterbatch output is 3 kg/h.

Reference wall thickness The main screen also shows the mean wall thickness derived from weight per metre, as a quick on-line reference.

Cable-specific conversion The cable edition derives mean cable circumference, outer diameter and sheath thickness from the measured data, for reference on the floor.

Two ways to take control Start on the machine's own control, with the extruder driving its own drives, or start under gravimetric control, where the system regulates extruder and haul-off automatically — speeds can also be typed in directly or ramped up and down in step.

ROI

Return on investment

The system typically saves 2%–5% of raw material, sometimes more. The figures below assume 2.5% savings at a material price of RMB 9.00/kg.

Line output	Running time	Saving	Material price	Annual saving
650 kg/h	16h/day × 200 days/yr	2.5%	RMB 9.00/kg	RMB 468,000/yr
350 kg/h	12h/day × 200 days/yr	2.5%	RMB 9.00/kg	RMB 189,000/yr
250 kg/h	12h/day × 180 days/yr	2.5%	RMB 9.00/kg	RMB 121,500/yr

Source: ROI examples in the Sealion cable-gravimetric brochure. Actual savings vary with output, hours, price and saving rate.

Alarms

Alarm codes & on-line checks

When the system alarms, a code appears on screen. The table below gives what each code means and the checks line staff can make without opening the cabinet and without working on live equipment. If the alarm persists after those checks, contact Sealion service — anything involving measurement inside the cabinet, wiring changes or part replacement is for our engineers.

Code	Meaning	Checks you can make on the line
00	Module cannot connect to the PC	Power the display off and on a few times to see if it recovers; check that the display-to-controller communication cable is firmly seated and undamaged.
01	Hopper starved	Is the silo empty? Is the drop path blocked or bridging? Is air pressure 0.3–0.4MPa? Does the shut-off mechanism move freely, and is anything propping up the cylinder base?
02	Output fluctuating	Is the hopper filling and discharging normally? Any disturbance near the weighing point (hopper vibration, blockage, excessive throat temperature)? Watch the silo — is the screw taking material unevenly?
03	Haul-off speed fluctuating	Is the encoder connector fully seated and the cable undamaged? Is the encoder mounted square and centred? Is the coupling tight? Is the supply healthy?
05	Excessive torque	The extruder is drawing overload current. Reduce screw speed first, then find the cause — commonly the screw is starved or the melt is too cold.
06	Poor feeding	Is the silo empty? Is the loader working?
07	Poor link between gravimetric and haul-off modules	Is the cable between the two modules fully seated and undamaged? Any strong source of electrical interference nearby?
09	Extruder signal low	Check the extruder control cable is firmly seated and undamaged. If it still alarms, an engineer needs to measure on site.
11	Large deviation between measured and set value	Look at the haul-off and output curves: if the haul-off curve is abnormal see code 03; if the output curve is abnormal see code 02.
12	Extruder fault	Has the extruder breaker tripped? Is the extruder start signal on?
13	Haul-off fault	Has the haul-off breaker tripped? Is the haul-off start signal on?
14	Haul-off signal at maximum	The haul-off is near the inverter's 50Hz ceiling. Reduce haul-off speed and establish why such a high speed was needed.
15	Measured weight per metre far from setpoint	Review the haul-off and output curves and work through the checks for codes 02 and 03.
17	Extruder or haul-off control signal exceeds the read signal by 30%	Raised when overshoot occurs in steady state. Check the curves to see whether the extrusion or the haul-off end is causing it.
19	Abnormal screw speed	Is the extruder speed curve smooth? If it is, the speed pick-up is the likely cause — check the proximity switch and sensing collar for movement and correct gap. If it is not smooth, check whether output fluctuation is driving the speed.
20	No or very low haul-off speed reading	Is the encoder wheel turning with the pipe, and is the encoder shaft rotating? Is the encoder cable fully seated? If there is still no reading, an engineer must assess the encoder or module.
none	Hopper value never reaches the set upper limit	Usually caused by a large change in material density, so a full hopper still falls short of the threshold; output is then neither calculated nor controlled. The hopper thresholds need adjusting — contact service.
none	Hopper stays full and output will not rise	Confirm valve auto mode is on; confirm air supply is normal (0.3–0.4MPa); watch whether the shut-off device moves freely or is sticking. If it is still wrong, contact service.

Sealion provides lifetime maintenance and a two-year free warranty. Please do not attempt diagnosis that involves live measurement inside the cabinet, wiring changes, or replacing modules and parts — leave those to a Sealion engineer.

Tell an engineer what your line is fighting

Weight-per-metre that won't settle, wall thickness that drifts, scrap after every material change — this is what we solve daily.

Get a proposal & quote View all products Read the manual